Merge branch 'mc-1.20.x' into mc-1.21.x

This adds a new mechanism for attaching additional objects to a
computer, allowing them to be queried by other mods. This is primarily
designed for mods which add external APIs, allowing them to add APIs
which depend on the computer's position or can interact with the turtle
inventory.

I will stress that the use-cases for custom APIs are few and far
between. Almost all the time a peripheral would be the better option,
and I am wary that this PR will encourage misuse of APIs. However, there
are some legitimate use-cases, and I think we should enable them.

 - Add a new "ComputerComponent" class, and several built-in components
   (for turtle, pocket and command computers).

 - Add a method to `IComputerSystem` to read a component from the
   computer. We also add methods to get the level and position of the
   computer.

 - Move all our existing APIs (built-in turtle, pocket, command) to use
   the public API.

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -8,10 +8,8 @@ body:
     label: Minecraft Version
     description: What version of Minecraft are you using?
     options:
-      - 1.16.x
-      - 1.18.x
-      - 1.19.x
-      - 1.20.x
+      - 1.20.1
+      - 1.21.x
   validations:
     required: true
 - type: input

.pre-commit-config.yaml

@@ -27,7 +27,7 @@ repos:
     exclude: "^(.*\\.(bat)|LICENSE)$"
 
 - repo: https://github.com/fsfe/reuse-tool
-  rev: v2.1.0
+  rev: v4.0.3
   hooks:
   - id: reuse
 

.reuse/dep5

@@ -1,100 +0,0 @@
-Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
-Source: https://github.com/cc-tweaked/cc-tweaked
-Upstream-Name: CC: Tweaked
-Upstream-Contact: Jonathan Coates <git@squiddev.cc>
-
-Files:
-  projects/common/src/main/resources/assets/computercraft/sounds.json
-  projects/common/src/main/resources/assets/computercraft/sounds/empty.ogg
-  projects/common/src/testMod/resources/data/cctest/computercraft/turtle_upgrade/*
-  projects/common/src/testMod/resources/data/cctest/structures/*
-  projects/*/src/generated/*
-  projects/web/src/htmlTransform/export/index.json
-  projects/web/src/htmlTransform/export/items/minecraft/*
-Comment: Generated/data files are CC0.
-Copyright: The CC: Tweaked Developers
-License: CC0-1.0
-
-Files:
-  doc/images/*
-  package.json
-  package-lock.json
-  projects/common/src/client/resources/computercraft-client.mixins.json
-  projects/common/src/main/resources/assets/minecraft/shaders/core/computercraft/monitor_tbo.json
-  projects/common/src/main/resources/computercraft.mixins.json
-  projects/common/src/testMod/resources/computercraft-gametest.mixins.json
-  projects/common/src/testMod/resources/data/computercraft/loot_tables/treasure_disk.json
-  projects/common/src/testMod/resources/pack.mcmeta
-  projects/core/src/main/resources/data/computercraft/lua/rom/modules/command/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/modules/main/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/modules/turtle/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/motd.txt
-  projects/fabric-api/src/main/modJson/fabric.mod.json
-  projects/fabric/src/client/resources/computercraft-client.fabric.mixins.json
-  projects/fabric/src/main/resources/computercraft.fabric.mixins.json
-  projects/fabric/src/main/resources/fabric.mod.json
-  projects/fabric/src/testMod/resources/computercraft-gametest.fabric.mixins.json
-  projects/fabric/src/testMod/resources/fabric.mod.json
-  projects/forge/src/client/resources/computercraft-client.forge.mixins.json
-  projects/forge/src/main/resources/computercraft.forge.mixins.json
-  projects/web/src/frontend/mount/.settings
-  projects/web/src/frontend/mount/example.nfp
-  projects/web/src/frontend/mount/example.nft
-  projects/web/src/frontend/mount/expr_template.lua
-  projects/web/tsconfig.json
-Comment: Several assets where it's inconvenient to create a .license file.
-Copyright: The CC: Tweaked Developers
-License: MPL-2.0
-
-Files:
-  doc/logo.png
-  doc/logo-darkmode.png
-  projects/common/src/main/resources/assets/computercraft/models/*
-  projects/common/src/main/resources/assets/computercraft/textures/*
-  projects/common/src/main/resources/pack.mcmeta
-  projects/common/src/main/resources/pack.png
-  projects/core/src/main/resources/assets/computercraft/textures/gui/term_font.png
-  projects/core/src/main/resources/data/computercraft/lua/rom/autorun/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/help/*
-  projects/core/src/main/resources/data/computercraft/lua/rom/programs/fun/advanced/levels/*
-  projects/web/src/htmlTransform/export/items/computercraft/*
-Comment: Bulk-license original assets as CCPL.
-Copyright: 2011 Daniel Ratcliffe
-License: LicenseRef-CCPL
-
-Files:
-  projects/common/src/main/resources/assets/computercraft/lang/cs_cz.json
-  projects/common/src/main/resources/assets/computercraft/lang/ko_kr.json
-  projects/common/src/main/resources/assets/computercraft/lang/pl_pl.json
-  projects/common/src/main/resources/assets/computercraft/lang/pt_br.json
-  projects/common/src/main/resources/assets/computercraft/lang/ru_ru.json
-  projects/common/src/main/resources/assets/computercraft/lang/uk_ua.json
-  projects/common/src/main/resources/assets/computercraft/lang/zh_cn.json
-Comment: Community-contributed license files
-Copyright: 2017 The CC: Tweaked Developers
-License: LicenseRef-CCPL
-
-Files:
-  projects/common/src/main/resources/assets/computercraft/lang/*
-Comment: Community-contributed license files
-Copyright: 2017 The CC: Tweaked Developers
-License: MPL-2.0
-
-Files:
-  .github/*
-Comment:
-  GitHub build scripts are CC0. While we could add a header to each file,
-  it's unclear if it will break actions or issue templates in some way.
-Copyright: Jonathan Coates <git@squiddev.cc>
-License: CC0-1.0
-
-Files:
-  gradle/wrapper/*
-  gradlew
-  gradlew.bat
-Copyright: Gradle Inc
-License: Apache-2.0
-
-Files: projects/core/src/test/resources/test-rom/data/json-parsing/*
-Copyright: 2016 Nicolas Seriot
-License: MIT

CONTRIBUTING.md

@@ -12,7 +12,6 @@ If you've any other questions, [just ask the community][community] or [open an i
 
 ## Table of Contents
  - [Reporting issues](#reporting-issues)
- - [Translations](#translations)
  - [Setting up a development environment](#setting-up-a-development-environment)
  - [Developing CC: Tweaked](#developing-cc-tweaked)
  - [Writing documentation](#writing-documentation)
@@ -21,17 +20,13 @@ If you've any other questions, [just ask the community][community] or [open an i
 If you have a bug, suggestion, or other feedback, the best thing to do is [file an issue][new-issue]. When doing so, do
 use the issue templates - they provide a useful hint on what information to provide.
 
-## Translations
-Translations are managed through [Weblate], an online interface for managing language strings. This is synced
-automatically with GitHub, so please don't submit PRs adding/changing translations!
-
 ## Setting up a development environment
 In order to develop CC: Tweaked, you'll need to download the source code and then run it.
 
  - Make sure you've got the following software installed:
-   - Java Development Kit (JDK). This can be downloaded from [Adoptium].
+   - Java Development Kit 21 (JDK). This can be downloaded from [Adoptium].
    - [Git](https://git-scm.com/).
-   - [NodeJS][node].
+   - [NodeJS 20 or later][node].
 
  - Download CC: Tweaked's source code:
    ```
@@ -101,7 +96,6 @@ about how you can build on that until you've covered everything!
 [community]: README.md#community "Get in touch with the community."
 [Adoptium]: https://adoptium.net/temurin/releases?version=17 "Download OpenJDK 17"
 [illuaminate]: https://github.com/SquidDev/illuaminate/ "Illuaminate on GitHub"
-[weblate]: https://i18n.tweaked.cc/projects/cc-tweaked/minecraft/ "CC: Tweaked weblate instance"
 [docs]: https://tweaked.cc/ "CC: Tweaked documentation"
 [ldoc]: http://stevedonovan.github.io/ldoc/ "ldoc, a Lua documentation generator."
 [mc-test]: https://www.youtube.com/watch?v=vXaWOJTCYNg

README.md

@@ -26,8 +26,9 @@ developing the mod, [check out the instructions here](CONTRIBUTING.md#developing
 
 ## Community
 If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
-ComputerCraft, do check out our [forum] and [GitHub discussions page][GitHub discussions]! There's also a fairly
-populated, albeit quiet [IRC channel][irc], if that's more your cup of tea.
+ComputerCraft, do check out our [GitHub discussions page][GitHub discussions]! There's also a fairly populated,
+albeit quiet IRC channel on [EsperNet], if that's more your cup of tea. You can join `#computercraft` through your
+desktop client, or online using [KiwiIRC].
 
 We also host fairly comprehensive documentation at [tweaked.cc](https://tweaked.cc/ "The CC: Tweaked website").
 
@@ -39,7 +40,7 @@ on is present.
 ```groovy
 repositories {
   maven {
-    url "https://squiddev.cc/maven/"
+    url "https://maven.squiddev.cc"
     content {
       includeGroup("cc.tweaked")
     }
@@ -85,6 +86,6 @@ the generated documentation [can be browsed online](https://tweaked.cc/javadoc/)
 [modrinth]: https://modrinth.com/mod/gu7yAYhd "Download CC: Tweaked from Modrinth"
 [Minecraft Forge]: https://files.minecraftforge.net/ "Download Minecraft Forge."
 [Fabric]: https://fabricmc.net/use/installer/ "Download Fabric."
-[forum]: https://forums.computercraft.cc/
 [GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: https://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[EsperNet]: https://www.esper.net/
+[KiwiIRC]: https://kiwiirc.com/nextclient/#irc://irc.esper.net:+6697/#computercraft "#computercraft on EsperNet"

REUSE.toml

@@ -0,0 +1,111 @@
+# SPDX-FileCopyrightText: 2017 The CC: Tweaked Developers
+#
+# SPDX-License-Identifier: MPL-2.0
+
+version = 1
+SPDX-PackageName = "CC: Tweaked"
+SPDX-PackageSupplier = "Jonathan Coates <git@squiddev.cc>"
+SPDX-PackageDownloadLocation = "https://github.com/cc-tweaked/cc-tweaked"
+
+[[annotations]]
+# Generated/data files are CC0.
+SPDX-FileCopyrightText = "The CC: Tweaked Developers"
+SPDX-License-Identifier = "CC0-1.0"
+path = [
+    "gradle/gradle-daemon-jvm.properties",
+    "projects/common/src/main/resources/assets/computercraft/sounds.json",
+    "projects/common/src/main/resources/assets/computercraft/sounds/empty.ogg",
+    "projects/common/src/testMod/resources/data/cctest/computercraft/turtle_upgrade/**",
+    "projects/common/src/testMod/resources/data/cctest/structures/**",
+    "projects/**/src/generated/**",
+    "projects/web/src/htmlTransform/export/index.json",
+    "projects/web/src/htmlTransform/export/items/minecraft/**",
+]
+
+[[annotations]]
+# Several assets where it's inconvenient to create a .license file.
+SPDX-FileCopyrightText = "The CC: Tweaked Developers"
+SPDX-License-Identifier = "MPL-2.0"
+path = [
+    "doc/images/**",
+    "package.json",
+    "package-lock.json",
+    "projects/common/src/client/resources/computercraft-client.mixins.json",
+    "projects/common/src/main/resources/assets/minecraft/shaders/core/computercraft/monitor_tbo.json",
+    "projects/common/src/main/resources/computercraft.mixins.json",
+    "projects/common/src/testMod/resources/computercraft-gametest.mixins.json",
+    "projects/common/src/testMod/resources/data/computercraft/loot_tables/treasure_disk.json",
+    "projects/common/src/testMod/resources/pack.mcmeta",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/modules/command/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/modules/main/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/modules/turtle/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/motd.txt",
+    "projects/fabric-api/src/main/modJson/fabric.mod.json",
+    "projects/fabric/src/client/resources/computercraft-client.fabric.mixins.json",
+    "projects/fabric/src/main/resources/computercraft.fabric.mixins.json",
+    "projects/fabric/src/main/resources/fabric.mod.json",
+    "projects/fabric/src/testMod/resources/computercraft-gametest.fabric.mixins.json",
+    "projects/fabric/src/testMod/resources/fabric.mod.json",
+    "projects/forge/src/client/resources/computercraft-client.forge.mixins.json",
+    "projects/forge/src/main/resources/computercraft.forge.mixins.json",
+    "projects/web/src/frontend/mount/.settings",
+    "projects/web/src/frontend/mount/example.nfp",
+    "projects/web/src/frontend/mount/example.nft",
+    "projects/web/src/frontend/mount/expr_template.lua",
+    "projects/web/tsconfig.json",
+]
+
+[[annotations]]
+# Bulk-license original assets as CCPL.
+SPDX-FileCopyrightText = "2011 Daniel Ratcliffe"
+SPDX-License-Identifier = "LicenseRef-CCPL"
+path = [
+    "doc/logo.png",
+    "doc/logo-darkmode.png",
+    "projects/common/src/main/resources/assets/computercraft/models/**",
+    "projects/common/src/main/resources/assets/computercraft/textures/**",
+    "projects/common/src/main/resources/pack.mcmeta",
+    "projects/common/src/main/resources/pack.png",
+    "projects/core/src/main/resources/assets/computercraft/textures/gui/term_font.png",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/autorun/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/help/**",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/programs/fun/advanced/levels/**",
+    "projects/web/src/htmlTransform/export/items/computercraft/**",
+]
+
+[[annotations]]
+# Community-contributed license files
+SPDX-FileCopyrightText = "2017 The CC: Tweaked Developers"
+SPDX-License-Identifier = "LicenseRef-CCPL"
+path = [
+    "projects/common/src/main/resources/assets/computercraft/lang/cs_cz.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/ko_kr.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/pl_pl.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/pt_br.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/ru_ru.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/uk_ua.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/zh_cn.json",
+]
+
+[[annotations]]
+# Community-contributed license files
+SPDX-FileCopyrightText = "2017 The CC: Tweaked Developers"
+SPDX-License-Identifier = "MPL-2.0"
+path = "projects/common/src/main/resources/assets/computercraft/lang/**"
+
+[[annotations]]
+# GitHub build scripts are CC0. While we could add a header to each file,
+# it's unclear if it will break actions or issue templates in some way.
+SPDX-FileCopyrightText = "Jonathan Coates <git@squiddev.cc>"
+SPDX-License-Identifier = "CC0-1.0"
+path = ".github/**"
+
+[[annotations]]
+path = ["gradle/wrapper/**", "gradlew", "gradlew.bat"]
+SPDX-FileCopyrightText = "Gradle Inc"
+SPDX-License-Identifier = "Apache-2.0"
+
+[[annotations]]
+path = "projects/core/src/test/resources/test-rom/data/json-parsing/**"
+SPDX-FileCopyrightText = "2016 Nicolas Seriot"
+SPDX-License-Identifier = "MIT"

buildSrc/build.gradle.kts

@@ -32,7 +32,7 @@ repositories {
         }
     }
 
-    maven("https://squiddev.cc/maven") {
+    maven("https://maven.squiddev.cc") {
         name = "SquidDev"
         content {
             includeGroup("cc.tweaked.vanilla-extract")

buildSrc/src/main/kotlin/cc-tweaked.java-convention.gradle.kts

@@ -38,7 +38,7 @@ java {
 repositories {
     mavenCentral()
 
-    val mainMaven = maven("https://squiddev.cc/maven") {
+    val mainMaven = maven("https://maven.squiddev.cc/mirror") {
         name = "SquidDev"
     }
 
@@ -47,6 +47,7 @@ repositories {
         filter {
             includeGroup("cc.tweaked")
             // Things we mirror
+            includeGroup("com.simibubi.create")
             includeGroup("commoble.morered")
             includeGroup("dev.architectury")
             includeGroup("dev.emi")
@@ -133,8 +134,8 @@ tasks.processResources {
 tasks.withType(AbstractArchiveTask::class.java).configureEach {
     isPreserveFileTimestamps = false
     isReproducibleFileOrder = true
-    dirMode = Integer.valueOf("755", 8)
-    fileMode = Integer.valueOf("664", 8)
+    filePermissions {}
+    dirPermissions {}
 }
 
 tasks.jar {

buildSrc/src/main/kotlin/cc-tweaked.publishing.gradle.kts

@@ -38,7 +38,7 @@ publishing {
     }
 
     repositories {
-        maven("https://squiddev.cc/maven") {
+        maven("https://maven.squiddev.cc") {
             name = "SquidDev"
 
             credentials(PasswordCredentials::class)

buildSrc/src/main/kotlin/cc/tweaked/gradle/CCTweakedExtension.kt

@@ -22,7 +22,6 @@ import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.bundling.Jar
 import org.gradle.api.tasks.compile.JavaCompile
 import org.gradle.api.tasks.javadoc.Javadoc
-import org.gradle.configurationcache.extensions.capitalized
 import org.gradle.language.base.plugins.LifecycleBasePlugin
 import org.gradle.language.jvm.tasks.ProcessResources
 import org.gradle.process.JavaForkOptions
@@ -181,7 +180,7 @@ abstract class CCTweakedExtension(
 
     fun <T> jacoco(task: NamedDomainObjectProvider<T>) where T : Task, T : JavaForkOptions {
         val classDump = project.layout.buildDirectory.dir("jacocoClassDump/${task.name}")
-        val reportTaskName = "jacoco${task.name.capitalized()}Report"
+        val reportTaskName = "jacoco${task.name.capitalise()}Report"
 
         val jacoco = project.extensions.getByType(JacocoPluginExtension::class.java)
         task.configure {

buildSrc/src/main/kotlin/cc/tweaked/gradle/Extensions.kt

@@ -9,6 +9,7 @@ import org.gradle.api.file.FileSystemLocation
 import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.JavaExec
+import org.gradle.kotlin.dsl.getByName
 import org.gradle.process.BaseExecSpec
 import org.gradle.process.JavaExecSpec
 import org.gradle.process.ProcessForkOptions
@@ -46,6 +47,21 @@ fun JavaExec.copyToFull(spec: JavaExec) {
     copyToExec(spec)
 }
 
+/**
+ * Base this [JavaExec] task on an existing task.
+ */
+fun JavaExec.copyFromTask(task: JavaExec) {
+    for (dep in task.dependsOn) dependsOn(dep)
+    task.copyToFull(this)
+}
+
+/**
+ * Base this [JavaExec] task on an existing task.
+ */
+fun JavaExec.copyFromTask(task: String) {
+    copyFromTask(project.tasks.getByName<JavaExec>(task))
+}
+
 /**
  * Copy additional [BaseExecSpec] options which aren't handled by [ProcessForkOptions.copyTo].
  */
@@ -155,3 +171,15 @@ fun getNextVersion(version: String): String {
     if (dashIndex >= 0) out.append(version, dashIndex, version.length)
     return out.toString()
 }
+
+/**
+ * Capitalise the first letter of the string.
+ *
+ * This is a replacement for the now deprecated [String.capitalize].
+ */
+fun String.capitalise(): String {
+    if (isEmpty()) return this
+    val first = this[0]
+    val firstTitle = first.titlecaseChar()
+    return if (first == firstTitle) this else firstTitle + substring(1)
+}

buildSrc/src/main/kotlin/cc/tweaked/gradle/ForgeExtensions.kt

@@ -1,62 +0,0 @@
-// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
-//
-// SPDX-License-Identifier: MPL-2.0
-
-package cc.tweaked.gradle
-
-import net.neoforged.gradle.common.runs.run.RunImpl
-import net.neoforged.gradle.common.runs.tasks.RunExec
-import net.neoforged.gradle.dsl.common.extensions.RunnableSourceSet
-import net.neoforged.gradle.dsl.common.runs.run.Run
-import org.gradle.api.plugins.JavaPluginExtension
-import org.gradle.api.tasks.JavaExec
-import org.gradle.api.tasks.SourceSet
-import org.gradle.jvm.toolchain.JavaToolchainService
-import org.gradle.kotlin.dsl.assign
-import org.gradle.kotlin.dsl.create
-import org.gradle.kotlin.dsl.findByType
-import java.nio.file.Files
-
-/**
- * Set [JavaExec] task to run a given [RunConfig].
- *
- * See also [RunExec].
- */
-fun JavaExec.setRunConfig(config: Run) {
-    mainClass.set(config.mainClass)
-    workingDir = config.workingDirectory.get().asFile
-    argumentProviders.add { config.programArguments.get() }
-    jvmArgumentProviders.add { config.jvmArguments.get() }
-
-    environment(config.environmentVariables.get())
-    systemProperties(config.systemProperties.get())
-
-    config.modSources.all().get().values().forEach { classpath(it.runtimeClasspath) }
-    classpath(config.classpath)
-    classpath(config.dependencies.get().runtimeConfiguration)
-
-    (config as RunImpl).taskDependencies.forEach { dependsOn(it) }
-
-    javaLauncher.set(
-        project.extensions.getByType(JavaToolchainService::class.java)
-            .launcherFor(project.extensions.getByType(JavaPluginExtension::class.java).toolchain),
-    )
-
-    doFirst("Create working directory") { Files.createDirectories(workingDir.toPath()) }
-}
-
-/**
- * Add a new [Run.modSource] with a specific mod id.
- */
-fun Run.modSourceAs(sourceSet: SourceSet, mod: String) {
-    // NeoGradle requires a RunnableSourceSet to be present, so we inject it into other project's source sets.
-    val runnable = sourceSet.extensions.findByType<RunnableSourceSet>() ?: run {
-        val extension = sourceSet.extensions.create<RunnableSourceSet>(RunnableSourceSet.NAME, project)
-        extension.modIdentifier = mod
-        extension.modIdentifier.finalizeValueOnRead()
-        extension
-    }
-    if (runnable.modIdentifier.get() != mod) throw IllegalArgumentException("Multiple mod identifiers")
-
-    modSource(sourceSet)
-}

doc/guides/speaker_audio.md

@@ -191,7 +191,7 @@ end
 
 > [Confused?][!NOTE]
 > Don't worry if you don't understand this example. It's quite advanced, and does use some ideas that this guide doesn't
-> cover. That said, don't be afraid to ask on [GitHub Discussions] or [IRC] either!
+> cover. That said, don't be afraid to ask [the community for help][community].
 
 It's worth noting that the examples of audio processing we've mentioned here are about manipulating the _amplitude_ of
 the wave. If you wanted to modify the _frequency_ (for instance, shifting the pitch), things get rather more complex.
@@ -205,5 +205,4 @@ This is, I'm afraid, left as an exercise to the reader.
 [PCM]: https://en.wikipedia.org/wiki/Pulse-code_modulation "Pulse-code Modulation - Wikipedia"
 [Ring Buffer]: https://en.wikipedia.org/wiki/Circular_buffer "Circular buffer - Wikipedia"
 [Sine Wave]: https://en.wikipedia.org/wiki/Sine_wave "Sine wave - Wikipedia"
-[GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: https://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[Community]: /#community

doc/index.md

@@ -50,7 +50,11 @@ little daunting getting started. Thankfully, there's several fantastic tutorials
 Once you're a little more familiar with the mod, the sidebar and links below provide more detailed documentation on the
 various APIs and peripherals provided by the mod.
 
-If you get stuck, do [ask a question on GitHub][GitHub Discussions] or pop in to the ComputerCraft's [IRC channel][IRC].
+<h2 id="community">Community</h2>
+If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
+ComputerCraft, do check out our [GitHub discussions page][GitHub discussions]! There's also a fairly populated,
+albeit quiet IRC channel on [EsperNet], if that's more your cup of tea. You can join `#computercraft` through your
+desktop client, or online using [KiwiIRC].
 
 ## Get Involved
 CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please do [create an issue][bug].
@@ -65,4 +69,5 @@ CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please
 [Fabric]: https://fabricmc.net/use/installer/ "Download Fabric."
 [lua]: https://www.lua.org/ "Lua's main website"
 [GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: https://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[EsperNet]: https://www.esper.net/
+[KiwiIRC]: https://kiwiirc.com/nextclient/#irc://irc.esper.net:+6697/#computercraft "#computercraft on EsperNet"

doc/mod-page.md

@@ -50,7 +50,11 @@ little daunting getting started. Thankfully, there's several fantastic tutorials
 Once you're a little more familiar with the mod, the [wiki](https://tweaked.cc/) provides more detailed documentation on the
 various APIs and peripherals provided by the mod.
 
-If you get stuck, do [ask a question on GitHub][GitHub Discussions] or pop in to the ComputerCraft's [IRC channel][IRC].
+## Community
+If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
+ComputerCraft, do check out our [GitHub discussions page][GitHub discussions]! There's also a fairly populated,
+albeit quiet IRC channel on [EsperNet], if that's more your cup of tea. You can join `#computercraft` through your
+desktop client, or online using [KiwiIRC].
 
 ## Get Involved
 CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please do [create an issue][bug].
@@ -60,4 +64,5 @@ CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please
 [computercraft]: https://github.com/dan200/ComputerCraft "ComputerCraft on GitHub"
 [lua]: https://www.lua.org/ "Lua's main website"
 [GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: http://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[EsperNet]: https://www.esper.net/
+[KiwiIRC]: https://kiwiirc.com/nextclient/#irc://irc.esper.net:+6697/#computercraft "#computercraft on EsperNet"

doc/reference/breaking_changes.md

@@ -25,13 +25,13 @@ as documentation for breaking changes and "gotchas" one should look out for betw
 
  - Update to Lua 5.2:
    - Support for Lua 5.0's pseudo-argument `arg` has been removed. You should always use `...` for varargs.
-   - Environments are no longer baked into the runtime, and instead use the `_ENV` local or upvalue. `getfenv`/`setfenv`
-     now only work on Lua functions with an `_ENV` upvalue. `getfenv` will return the global environment when called
-     with other functions, and `setfenv` will have no effect.
-   - `load`/`loadstring` defaults to using the global environment (`_G`) rather than the current coroutine's
+   - Environments are no longer baked into the runtime, and instead use the `_ENV` local or upvalue. [`getfenv`]/[`setfenv`]
+     now only work on Lua functions with an `_ENV` upvalue. [`getfenv`] will return the global environment when called
+     with other functions, and [`setfenv`] will have no effect.
+   - [`load`]/[`loadstring`] defaults to using the global environment (`_G`) rather than the current coroutine's
      environment.
-   - Support for dumping functions (`string.dump`) and loading binary chunks has been removed.
-   - `math.random` now uses Lua 5.4's random number generator.
+   - Support for dumping functions ([`string.dump`]) and loading binary chunks has been removed.
+   - [`math.random`] now uses Lua 5.4's random number generator.
 
  - File handles, HTTP requests and websockets now always use the original bytes rather than encoding/decoding to UTF-8.
 
@@ -44,7 +44,7 @@ as documentation for breaking changes and "gotchas" one should look out for betw
    `keys.enter` constant was queued when the key was pressed)
 
  - Minecraft 1.13 removed the concept of item damage and block metadata (see ["The Flattening"][flattening]). As a
-   result `turtle.inspect` no longer provides block metadata, and `turtle.getItemDetail` no longer provides damage.
+   result [`turtle.inspect`] no longer provides block metadata, and [`turtle.getItemDetail`] no longer provides damage.
 
    - Block states (`turtle.inspect().state`) should provide all the same information as block metadata, but in a much
      more understandable format.
@@ -70,7 +70,7 @@ as documentation for breaking changes and "gotchas" one should look out for betw
  - Unlabelled computers and turtles now keep their ID when broken, meaning that unlabelled computers/items do not stack.
 
 ## ComputerCraft 1.80pr1 {#cc-1.80}
- - Programs run via `shell.run` are now started in their own isolated environment. This means globals set by programs
+ - Programs run via [`shell.run`] are now started in their own isolated environment. This means globals set by programs
    will not be accessible outside of this program.
 
  - Programs containing `/` are looked up in the current directory and are no longer looked up on the path. For instance,

gradle.properties

@@ -12,7 +12,7 @@ neogradle.subsystems.conventions.runs.enabled=false
 
 # Mod properties
 isUnstable=true
-modVersion=1.111.0
+modVersion=1.112.0
 
 # Minecraft properties: We want to configure this here so we can read it in settings.gradle
 mcVersion=1.21

gradle/gradle-daemon-jvm.properties

@@ -0,0 +1,2 @@
+#This file is generated by updateDaemonJvm
+toolchainVersion=21

gradle/libs.versions.toml

@@ -7,13 +7,13 @@
 # Minecraft
 # MC version is specified in gradle.properties, as we need that in settings.gradle.
 # Remember to update corresponding versions in fabric.mod.json/neoforge.mods.toml
-fabric-api = "0.100.3+1.21"
+fabric-api = "0.100.7+1.21"
 fabric-loader = "0.15.11"
-neoForge = "21.0.21-beta"
+neoForge = "21.0.143"
 neoForgeSpi = "8.0.1"
 mixin = "0.8.5"
-parchment = "2024.06.16"
-parchmentMc = "1.20.6"
+parchment = "2024.07.28"
+parchmentMc = "1.21"
 yarn = "1.21+build.1"
 
 # Core dependencies (these versions are tied to the version Minecraft uses)
@@ -47,6 +47,8 @@ rei = "16.0.729"
 rubidium = "0.6.1"
 sodium = "mc1.20-0.4.10"
 mixinExtra = "0.3.5"
+create-forge = "0.5.1.f-33"
+create-fabric = "0.5.1-f-build.1467+mc1.20.1"
 
 # Testing
 hamcrest = "2.2"
@@ -60,18 +62,18 @@ checkstyle = "10.14.1"
 curseForgeGradle = "1.1.18"
 errorProne-core = "2.27.0"
 errorProne-plugin = "3.1.0"
-fabric-loom = "1.6.7"
+fabric-loom = "1.7.1"
 githubRelease = "2.5.2"
 gradleVersions = "0.50.0"
 ideaExt = "1.1.7"
 illuaminate = "0.1.0-73-g43ee16c"
 lwjgl = "3.3.3"
 minotaur = "2.8.7"
-neoGradle = "7.0.145"
+neoGradle = "7.0.152"
 nullAway = "0.10.25"
 spotless = "6.23.3"
 taskTree = "2.1.1"
-teavm = "0.10.0-SQUID.4"
+teavm = "0.11.0-SQUID.1"
 vanillaExtract = "0.1.3"
 versionCatalogUpdate = "0.8.1"
 
@@ -100,11 +102,13 @@ nightConfig-toml = { module = "com.electronwill.night-config:toml", version.ref
 slf4j = { module = "org.slf4j:slf4j-api", version.ref = "slf4j" }
 
 # Minecraft mods
-fabric-api = { module = "net.fabricmc.fabric-api:fabric-api", version.ref = "fabric-api" }
-fabric-loader = { module = "net.fabricmc:fabric-loader", version.ref = "fabric-loader" }
-fabric-junit = { module = "net.fabricmc:fabric-loader-junit", version.ref = "fabric-loader" }
-fabricPermissions = { module = "me.lucko:fabric-permissions-api", version.ref = "fabricPermissions" }
+create-fabric = { module = "com.simibubi.create:create-fabric-1.20.1", version.ref = "create-fabric" }
+create-forge = { module = "com.simibubi.create:create-1.20.1", version.ref = "create-forge" }
 emi = { module = "dev.emi:emi-xplat-mojmap", version.ref = "emi" }
+fabric-api = { module = "net.fabricmc.fabric-api:fabric-api", version.ref = "fabric-api" }
+fabric-junit = { module = "net.fabricmc:fabric-loader-junit", version.ref = "fabric-loader" }
+fabric-loader = { module = "net.fabricmc:fabric-loader", version.ref = "fabric-loader" }
+fabricPermissions = { module = "me.lucko:fabric-permissions-api", version.ref = "fabricPermissions" }
 iris = { module = "maven.modrinth:iris", version.ref = "iris" }
 jei-api = { module = "mezz.jei:jei-1.21-common-api", version.ref = "jei" }
 jei-fabric = { module = "mezz.jei:jei-1.21-fabric", version.ref = "jei" }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

gradlew

@@ -55,7 +55,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.

projects/common-api/src/main/java/dan200/computercraft/api/ComputerCraftAPI.java

@@ -4,9 +4,11 @@
 
 package dan200.computercraft.api;
 
+import dan200.computercraft.api.component.ComputerComponent;
 import dan200.computercraft.api.filesystem.Mount;
 import dan200.computercraft.api.filesystem.WritableMount;
 import dan200.computercraft.api.lua.GenericSource;
+import dan200.computercraft.api.lua.IComputerSystem;
 import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.ILuaAPIFactory;
 import dan200.computercraft.api.media.IMedia;
@@ -165,7 +167,20 @@ public final class ComputerCraftAPI {
      * Register a custom {@link ILuaAPI}, which may be added onto all computers without requiring a peripheral.
      * <p>
      * Before implementing this interface, consider alternative methods of providing methods. It is generally preferred
-     * to use peripherals to provide functionality to users.
+     * to use peripherals to provide functionality to users. If an API is <em>required</em>, you may want to consider
+     * using {@link ILuaAPI#getModuleName()} to expose this library as a module instead of as a global.
+     * <p>
+     * This may be used with {@link IComputerSystem#getComponent(ComputerComponent)} to only attach APIs to specific
+     * computers. For example, one can add an additional API just to turtles with the following code:
+     *
+     * <pre>{@code
+     * ComputerCraftAPI.registerAPIFactory(computer -> {
+     *   // Read the turtle component.
+     *   var turtle = computer.getComponent(ComputerComponents.TURTLE);
+     *   // If present then add our API.
+     *   return turtle == null ? null : new MyCustomTurtleApi(turtle);
+     * });
+     * }</pre>
      *
      * @param factory The factory for your API subclass.
      * @see ILuaAPIFactory

projects/common-api/src/main/java/dan200/computercraft/api/component/AdminComputer.java

@@ -0,0 +1,24 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.component;
+
+import net.minecraft.commands.CommandSourceStack;
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * A computer which has permission to perform administrative/op commands, such as the command computer.
+ */
+@ApiStatus.NonExtendable
+public interface AdminComputer {
+    /**
+     * The permission level that this computer can operate at.
+     *
+     * @return The permission level for this computer.
+     * @see CommandSourceStack#hasPermission(int)
+     */
+    default int permissionLevel() {
+        return 2;
+    }
+}

projects/common-api/src/main/java/dan200/computercraft/api/component/ComputerComponent.java

@@ -0,0 +1,48 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.component;
+
+import dan200.computercraft.api.lua.IComputerSystem;
+import dan200.computercraft.api.lua.ILuaAPIFactory;
+
+/**
+ * A component attached to a computer.
+ * <p>
+ * Components provide a mechanism to attach additional data to a computer, that can then be queried with
+ * {@link IComputerSystem#getComponent(ComputerComponent)}.
+ * <p>
+ * This is largely designed for {@linkplain ILuaAPIFactory custom APIs}, allowing APIs to read additional properties
+ * of the computer, such as its position.
+ *
+ * @param <T> The type of this component.
+ * @see ComputerComponents The built-in components.
+ */
+@SuppressWarnings("UnusedTypeParameter")
+public final class ComputerComponent<T> {
+    private final String id;
+
+    private ComputerComponent(String id) {
+        this.id = id;
+    }
+
+    /**
+     * Create a new computer component.
+     * <p>
+     * Mods typically will not need to create their own components.
+     *
+     * @param namespace The namespace of this component. This should be the mod id.
+     * @param id        The unique id of this component.
+     * @param <T>       The component
+     * @return The newly created component.
+     */
+    public static <T> ComputerComponent<T> create(String namespace, String id) {
+        return new ComputerComponent<>(namespace + ":" + id);
+    }
+
+    @Override
+    public String toString() {
+        return "ComputerComponent(" + id + ")";
+    }
+}

projects/common-api/src/main/java/dan200/computercraft/api/component/ComputerComponents.java

@@ -0,0 +1,29 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.component;
+
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.pocket.IPocketAccess;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+
+/**
+ * The {@link ComputerComponent}s provided by ComputerCraft.
+ */
+public class ComputerComponents {
+    /**
+     * The {@link ITurtleAccess} associated with a turtle.
+     */
+    public static final ComputerComponent<ITurtleAccess> TURTLE = ComputerComponent.create(ComputerCraftAPI.MOD_ID, "turtle");
+
+    /**
+     * The {@link IPocketAccess} associated with a pocket computer.
+     */
+    public static final ComputerComponent<IPocketAccess> POCKET = ComputerComponent.create(ComputerCraftAPI.MOD_ID, "pocket");
+
+    /**
+     * This component is only present on "command computers", and other computers with admin capabilities.
+     */
+    public static final ComputerComponent<AdminComputer> ADMIN_COMPUTER = ComputerComponent.create(ComputerCraftAPI.MOD_ID, "admin_computer");
+}

projects/common-api/src/main/java/dan200/computercraft/api/lua/IComputerSystem.java

@@ -0,0 +1,59 @@
+// SPDX-FileCopyrightText: 2017 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.lua;
+
+import dan200.computercraft.api.component.ComputerComponent;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import org.jetbrains.annotations.ApiStatus;
+
+import javax.annotation.Nullable;
+
+/**
+ * An interface passed to {@link ILuaAPIFactory} in order to provide additional information
+ * about a computer.
+ */
+@ApiStatus.NonExtendable
+public interface IComputerSystem extends IComputerAccess {
+    /**
+     * Get the level this computer is currently in.
+     * <p>
+     * This method is not guaranteed to remain the same (even for stationary computers).
+     *
+     * @return The computer's current level.
+     */
+    ServerLevel getLevel();
+
+    /**
+     * Get the position this computer is currently at.
+     * <p>
+     * This method is not guaranteed to remain the same (even for stationary computers).
+     *
+     * @return The computer's current position.
+     */
+    BlockPos getPosition();
+
+    /**
+     * Get the label for this computer.
+     *
+     * @return This computer's label, or {@code null} if it is not set.
+     */
+    @Nullable
+    String getLabel();
+
+    /**
+     * Get a component attached to this computer.
+     * <p>
+     * No component is guaranteed to be on a computer, and so this method should always be guarded with a null check.
+     * <p>
+     * This method will always return the same value for a given component, and so may be cached.
+     *
+     * @param component The component to query.
+     * @param <T>       The type of the component.
+     * @return The component, if present.
+     */
+    <T> @Nullable T getComponent(ComputerComponent<T> component);
+}

projects/common-api/src/main/java/dan200/computercraft/api/lua/ILuaAPIFactory.java

@@ -4,13 +4,15 @@
 
 package dan200.computercraft.api.lua;
 
+import dan200.computercraft.api.ComputerCraftAPI;
+
 import javax.annotation.Nullable;
 
 /**
- * Construct an {@link ILuaAPI} for a specific computer.
+ * Construct an {@link ILuaAPI} for a computer.
  *
  * @see ILuaAPI
- * @see dan200.computercraft.api.ComputerCraftAPI#registerAPIFactory(ILuaAPIFactory)
+ * @see ComputerCraftAPI#registerAPIFactory(ILuaAPIFactory)
  */
 @FunctionalInterface
 public interface ILuaAPIFactory {

projects/common-api/src/main/java/dan200/computercraft/api/pocket/IPocketAccess.java

@@ -5,16 +5,35 @@
 package dan200.computercraft.api.pocket;
 
 import dan200.computercraft.api.upgrades.UpgradeBase;
+import dan200.computercraft.api.upgrades.UpgradeData;
 import net.minecraft.core.component.DataComponentPatch;
+import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.phys.Vec3;
+import org.jetbrains.annotations.ApiStatus;
 
 import javax.annotation.Nullable;
 
 /**
  * Wrapper class for pocket computers.
  */
+@ApiStatus.NonExtendable
 public interface IPocketAccess {
+    /**
+     * Get the level in which the pocket computer exists.
+     *
+     * @return The pocket computer's level.
+     */
+    ServerLevel getLevel();
+
+    /**
+     * Get the position of the pocket computer.
+     *
+     * @return The pocket computer's position.
+     */
+    Vec3 getPosition();
+
     /**
      * Gets the entity holding this item.
      * <p>
@@ -61,6 +80,26 @@ public interface IPocketAccess {
      */
     void setLight(int colour);
 
+    /**
+     * Get the currently equipped upgrade.
+     *
+     * @return The currently equipped upgrade.
+     * @see #getUpgradeData()
+     * @see #setUpgrade(UpgradeData)
+     */
+    @Nullable
+    UpgradeData<IPocketUpgrade> getUpgrade();
+
+    /**
+     * Set the upgrade for this pocket computer, also updating the item stack.
+     * <p>
+     * Note this method is not thread safe - it must be called from the server thread.
+     *
+     * @param upgrade The new upgrade to set it to, may be {@code null}.
+     * @see #getUpgrade()
+     */
+    void setUpgrade(@Nullable UpgradeData<IPocketUpgrade> upgrade);
+
     /**
      * Get the upgrade-specific NBT.
      * <p>
@@ -70,6 +109,7 @@ public interface IPocketAccess {
      * @see #setUpgradeData(DataComponentPatch)
      * @see UpgradeBase#getUpgradeItem(DataComponentPatch)
      * @see UpgradeBase#getUpgradeData(ItemStack)
+     * @see #getUpgrade()
      */
     DataComponentPatch getUpgradeData();
 

projects/common/build.gradle.kts

@@ -45,6 +45,7 @@ dependencies {
     compileOnly(libs.mixin)
     compileOnly(libs.mixinExtra)
     compileOnly(libs.bundles.externalMods.common)
+    compileOnly(variantOf(libs.create.forge) { classifier("slim") }) { isTransitive = false }
     clientCompileOnly(variantOf(libs.emi) { classifier("api") })
 
     annotationProcessorEverywhere(libs.autoService)

projects/common/src/client/java/dan200/computercraft/client/ClientRegistry.java

@@ -25,6 +25,7 @@ import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerContext;
 import dan200.computercraft.shared.computer.inventory.AbstractComputerMenu;
 import dan200.computercraft.shared.media.items.DiskItem;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import net.minecraft.Util;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.color.item.ItemColor;
@@ -53,6 +54,7 @@ import net.minecraft.world.level.ItemLike;
 import javax.annotation.Nullable;
 import java.io.File;
 import java.io.IOException;
+import java.util.Collection;
 import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -143,15 +145,14 @@ public final class ClientRegistry {
         register.accept(GuiSprites.initialise(minecraft.getTextureManager()));
     }
 
-    private static final String[] EXTRA_MODELS = new String[]{
-        "block/turtle_colour",
-        "block/turtle_elf_overlay",
-        "block/turtle_rainbow_overlay",
-        "block/turtle_trans_overlay",
+    private static final ResourceLocation[] EXTRA_MODELS = {
+        TurtleOverlay.ELF_MODEL,
+        TurtleBlockEntityRenderer.COLOUR_TURTLE_MODEL,
     };
 
-    public static void registerExtraModels(Consumer<ResourceLocation> register) {
-        for (var model : EXTRA_MODELS) register.accept(ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, model));
+    public static void registerExtraModels(Consumer<ResourceLocation> register, Collection<ResourceLocation> extraModels) {
+        for (var model : EXTRA_MODELS) register.accept(model);
+        extraModels.forEach(register);
         TurtleUpgradeModellers.getDependencies().forEach(register);
     }
 

projects/common/src/client/java/dan200/computercraft/client/model/ExtraModels.java

@@ -0,0 +1,68 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.client.model;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.JsonOps;
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.packs.resources.ResourceManager;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.*;
+
+/**
+ * A list of extra models to load on the client.
+ * <p>
+ * This is largely intended for use with {@linkplain TurtleOverlay turtle overlays}. As overlays are stored in a dynamic
+ * registry, they are not available when resources are loaded, and so we need a way to request the overlays' models be
+ * loaded.
+ *
+ * @param models The models to load.
+ */
+public record ExtraModels(List<ResourceLocation> models) {
+    private static final Logger LOG = LoggerFactory.getLogger(ExtraModels.class);
+    private static final Gson GSON = new Gson();
+
+    /**
+     * The path where the extra models are listed.
+     */
+    public static final ResourceLocation PATH = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "extra_models.json");
+
+    /**
+     * The coded used to store the extra model file.
+     */
+    public static final Codec<ExtraModels> CODEC = ResourceLocation.CODEC.listOf().xmap(ExtraModels::new, ExtraModels::models);
+
+    /**
+     * Get the list of all extra models to load.
+     *
+     * @param resources The current resource manager.
+     * @return A set of all resources to load.
+     */
+    public static Collection<ResourceLocation> loadAll(ResourceManager resources) {
+        Set<ResourceLocation> out = new HashSet<>();
+
+        for (var path : resources.getResourceStack(PATH)) {
+            ExtraModels models;
+            try (var stream = path.openAsReader()) {
+                models = ExtraModels.CODEC.parse(JsonOps.INSTANCE, GSON.fromJson(stream, JsonElement.class)).getOrThrow(JsonParseException::new);
+            } catch (IOException | RuntimeException e) {
+                LOG.error("Failed to load extra models from {}", path.sourcePackId());
+                continue;
+            }
+
+            out.addAll(models.models());
+        }
+
+        return Collections.unmodifiableCollection(out);
+    }
+}

projects/common/src/client/java/dan200/computercraft/client/model/turtle/TurtleModelParts.java

@@ -12,13 +12,14 @@ import dan200.computercraft.api.turtle.ITurtleUpgrade;
 import dan200.computercraft.api.turtle.TurtleSide;
 import dan200.computercraft.api.upgrades.UpgradeData;
 import dan200.computercraft.client.platform.ClientPlatformHelper;
-import dan200.computercraft.client.render.TurtleBlockEntityRenderer;
 import dan200.computercraft.client.turtle.TurtleUpgradeModellers;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.items.TurtleItem;
 import dan200.computercraft.shared.util.DataComponentUtil;
 import dan200.computercraft.shared.util.Holiday;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.resources.model.BakedModel;
+import net.minecraft.client.resources.model.ModelManager;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.item.ItemStack;
@@ -52,7 +53,7 @@ public final class TurtleModelParts<T> {
         boolean colour,
         @Nullable UpgradeData<ITurtleUpgrade> leftUpgrade,
         @Nullable UpgradeData<ITurtleUpgrade> rightUpgrade,
-        @Nullable ResourceLocation overlay,
+        @Nullable TurtleOverlay overlay,
         boolean christmas,
         boolean flip
     ) {
@@ -113,10 +114,10 @@ public final class TurtleModelParts<T> {
         var parts = new ArrayList<BakedModel>(4);
         parts.add(transform(combo.colour() ? colourModel : familyModel, transformation));
 
-        var overlayModelLocation = TurtleBlockEntityRenderer.getTurtleOverlayModel(combo.overlay(), combo.christmas());
-        if (overlayModelLocation != null) {
-            parts.add(transform(ClientPlatformHelper.get().getModel(modelManager, overlayModelLocation), transformation));
-        }
+        if (combo.overlay() != null) addPart(parts, modelManager, transformation, combo.overlay().model());
+
+        var showChristmas = TurtleOverlay.showElfOverlay(combo.overlay(), combo.christmas());
+        if (showChristmas) addPart(parts, modelManager, transformation, TurtleOverlay.ELF_MODEL);
 
         addUpgrade(parts, transformation, TurtleSide.LEFT, combo.leftUpgrade());
         addUpgrade(parts, transformation, TurtleSide.RIGHT, combo.rightUpgrade());
@@ -124,6 +125,10 @@ public final class TurtleModelParts<T> {
         return parts;
     }
 
+    private void addPart(List<BakedModel> parts, ModelManager modelManager, Transformation transformation, ResourceLocation model) {
+        parts.add(transform(ClientPlatformHelper.get().getModel(modelManager, model), transformation));
+    }
+
     private void addUpgrade(List<BakedModel> parts, Transformation transformation, TurtleSide side, @Nullable UpgradeData<ITurtleUpgrade> upgrade) {
         if (upgrade == null) return;
         var model = TurtleUpgradeModellers.getModel(upgrade.upgrade(), upgrade.data(), side);

projects/common/src/client/java/dan200/computercraft/client/render/TurtleBlockEntityRenderer.java

@@ -11,6 +11,7 @@ import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.turtle.TurtleSide;
 import dan200.computercraft.client.platform.ClientPlatformHelper;
 import dan200.computercraft.client.turtle.TurtleUpgradeModellers;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlockEntity;
 import dan200.computercraft.shared.util.Holiday;
 import net.minecraft.client.Minecraft;
@@ -21,14 +22,15 @@ import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
 import net.minecraft.client.renderer.blockentity.BlockEntityRendererProvider;
 import net.minecraft.client.resources.model.BakedModel;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.util.CommonColors;
+import net.minecraft.util.FastColor;
 import net.minecraft.world.phys.BlockHitResult;
 import net.minecraft.world.phys.HitResult;
 
 import javax.annotation.Nullable;
 
 public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBlockEntity> {
-    private static final ResourceLocation COLOUR_TURTLE_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_colour");
-    private static final ResourceLocation ELF_OVERLAY_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_elf_overlay");
+    public static final ResourceLocation COLOUR_TURTLE_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_colour");
 
     private final BlockEntityRenderDispatcher renderer;
     private final Font font;
@@ -38,12 +40,6 @@ public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBloc
         font = context.getFont();
     }
 
-    public static @Nullable ResourceLocation getTurtleOverlayModel(@Nullable ResourceLocation overlay, boolean christmas) {
-        if (overlay != null) return overlay;
-        if (christmas) return ELF_OVERLAY_MODEL;
-        return null;
-    }
-
     @Override
     public void render(TurtleBlockEntity turtle, float partialTicks, PoseStack transform, MultiBufferSource buffers, int lightmapCoord, int overlayLight) {
         transform.pushPose();
@@ -62,13 +58,13 @@ public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBloc
             transform.pushPose();
             transform.translate(0.5, 1.2, 0.5);
             transform.mulPose(mc.getEntityRenderDispatcher().cameraOrientation());
-            transform.scale(-0.025f, -0.025f, 0.025f);
+            transform.scale(0.025f, -0.025f, 0.025f);
 
             var matrix = transform.last().pose();
             var opacity = (int) (mc.options.getBackgroundOpacity(0.25f) * 255) << 24;
             var width = -font.width(label) / 2.0f;
             font.drawInBatch(label, width, (float) 0, 0x20ffffff, false, matrix, buffers, Font.DisplayMode.SEE_THROUGH, opacity, lightmapCoord);
-            font.drawInBatch(label, width, (float) 0, 0xffffffff, false, matrix, buffers, Font.DisplayMode.NORMAL, 0, lightmapCoord);
+            font.drawInBatch(label, width, (float) 0, CommonColors.WHITE, false, matrix, buffers, Font.DisplayMode.NORMAL, 0, lightmapCoord);
 
             transform.popPose();
         }
@@ -94,14 +90,15 @@ public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBloc
             renderModel(transform, buffers, lightmapCoord, overlayLight, model, null);
         } else {
             // Otherwise render it using the colour item.
-            renderModel(transform, buffers, lightmapCoord, overlayLight, COLOUR_TURTLE_MODEL, new int[]{ colour });
+            renderModel(transform, buffers, lightmapCoord, overlayLight, COLOUR_TURTLE_MODEL, new int[]{ FastColor.ARGB32.opaque(colour) });
         }
 
         // Render the overlay
-        var overlayModel = getTurtleOverlayModel(overlay, Holiday.getCurrent() == Holiday.CHRISTMAS);
-        if (overlayModel != null) {
-            renderModel(transform, buffers, lightmapCoord, overlayLight, overlayModel, null);
-        }
+        if (overlay != null) renderModel(transform, buffers, lightmapCoord, overlayLight, overlay.model(), null);
+
+        // And the Christmas overlay.
+        var showChristmas = TurtleOverlay.showElfOverlay(overlay, Holiday.getCurrent() == Holiday.CHRISTMAS);
+        if (showChristmas) renderModel(transform, buffers, lightmapCoord, overlayLight, TurtleOverlay.ELF_MODEL, null);
 
         // Render the upgrades
         renderUpgrade(transform, buffers, lightmapCoord, overlayLight, turtle, TurtleSide.LEFT, partialTicks);

projects/common/src/client/java/dan200/computercraft/data/client/ClientDataProviders.java

@@ -6,15 +6,18 @@ package dan200.computercraft.data.client;
 
 import dan200.computercraft.client.gui.GuiSprites;
 import dan200.computercraft.data.DataProviders;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.inventory.UpgradeSlot;
 import net.minecraft.client.renderer.texture.atlas.SpriteSource;
 import net.minecraft.client.renderer.texture.atlas.SpriteSources;
 import net.minecraft.client.renderer.texture.atlas.sources.SingleFile;
+import net.minecraft.core.HolderLookup;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.packs.PackType;
 
 import java.util.List;
 import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
 import java.util.stream.Stream;
 
 /**
@@ -26,7 +29,7 @@ public final class ClientDataProviders {
     private ClientDataProviders() {
     }
 
-    public static void add(DataProviders.GeneratorSink generator) {
+    public static void add(DataProviders.GeneratorSink generator, CompletableFuture<HolderLookup.Provider> registries) {
         generator.addFromCodec("Block atlases", PackType.CLIENT_RESOURCES, "atlases", SpriteSources.FILE_CODEC, out -> {
             out.accept(ResourceLocation.withDefaultNamespace("blocks"), List.of(
                 new SingleFile(UpgradeSlot.LEFT_UPGRADE, Optional.empty()),
@@ -44,5 +47,12 @@ public final class ClientDataProviders {
                 GuiSprites.COMPUTER_COLOUR.textures()
             ).flatMap(x -> x).<SpriteSource>map(x -> new SingleFile(x, Optional.empty())).toList());
         });
+
+        generator.add(pack -> new ExtraModelsProvider(pack, registries) {
+            @Override
+            public Stream<ResourceLocation> getModels(HolderLookup.Provider registries) {
+                return registries.lookupOrThrow(TurtleOverlay.REGISTRY).listElements().map(x -> x.value().model());
+            }
+        });
     }
 }

projects/common/src/client/java/dan200/computercraft/data/client/ExtraModelsProvider.java

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.data.client;
+
+import com.mojang.serialization.JsonOps;
+import dan200.computercraft.client.model.ExtraModels;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.data.CachedOutput;
+import net.minecraft.data.DataProvider;
+import net.minecraft.data.PackOutput;
+import net.minecraft.resources.ResourceLocation;
+
+import java.nio.file.Path;
+import java.util.concurrent.CompletableFuture;
+import java.util.stream.Stream;
+
+/**
+ * A data provider to generate {@link ExtraModels}.
+ */
+abstract class ExtraModelsProvider implements DataProvider {
+    private final Path path;
+    private final CompletableFuture<HolderLookup.Provider> registries;
+
+    ExtraModelsProvider(PackOutput output, CompletableFuture<HolderLookup.Provider> registries) {
+        path = output.getOutputFolder(PackOutput.Target.RESOURCE_PACK).resolve(ExtraModels.PATH.getNamespace()).resolve(ExtraModels.PATH.getPath());
+        this.registries = registries;
+    }
+
+    /**
+     * Return a stream of models to load.
+     *
+     * @param registries The current registries.
+     * @return The collection of extra models to load.
+     */
+    public abstract Stream<ResourceLocation> getModels(HolderLookup.Provider registries);
+
+    @Override
+    public final CompletableFuture<?> run(CachedOutput output) {
+        return registries.thenCompose(registries -> {
+            var models = new ExtraModels(getModels(registries).sorted().toList());
+            var json = ExtraModels.CODEC.encodeStart(JsonOps.INSTANCE, models).getOrThrow(IllegalStateException::new);
+            return DataProvider.saveStable(output, json, path);
+        });
+    }
+
+    @Override
+    public final String getName() {
+        return "Extra Models";
+    }
+}

projects/common/src/generated/resources/assets/computercraft/extra_models.json

@@ -0,0 +1 @@
+["computercraft:block/turtle_rainbow_overlay", "computercraft:block/turtle_trans_overlay"]

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_advanced_overlays/rainbow_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/turtle_trans_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/rainbow_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/turtle_trans_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/rainbow_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_advanced_overlays/trans_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/turtle_rainbow_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/trans_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/turtle_rainbow_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/trans_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_normal_overlays/rainbow_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_normal_overlays/turtle_trans_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_normal_overlays/rainbow_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/turtle_trans_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/rainbow_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_normal_overlays/trans_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_normal_overlays/turtle_rainbow_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_normal_overlays/trans_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/turtle_rainbow_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/trans_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/computercraft/turtle_overlay/rainbow_flag.json

@@ -0,0 +1 @@
+{"model": "computercraft:block/turtle_rainbow_overlay", "show_elf_overlay": true}

projects/common/src/generated/resources/data/computercraft/computercraft/turtle_overlay/trans_flag.json

@@ -0,0 +1 @@
+{"model": "computercraft:block/turtle_trans_overlay", "show_elf_overlay": true}

projects/common/src/generated/resources/data/computercraft/recipe/turtle_advanced_overlays/rainbow_flag.json

@@ -20,7 +20,7 @@
     {"item": "computercraft:turtle_advanced"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_rainbow_overlay"},
+    "components": {"computercraft:overlay": "computercraft:rainbow_flag"},
     "count": 1,
     "id": "computercraft:turtle_advanced"
   }

projects/common/src/generated/resources/data/computercraft/recipe/turtle_advanced_overlays/trans_flag.json

@@ -17,7 +17,7 @@
     {"item": "computercraft:turtle_advanced"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_trans_overlay"},
+    "components": {"computercraft:overlay": "computercraft:trans_flag"},
     "count": 1,
     "id": "computercraft:turtle_advanced"
   }

projects/common/src/generated/resources/data/computercraft/recipe/turtle_normal_overlays/rainbow_flag.json

@@ -20,7 +20,7 @@
     {"item": "computercraft:turtle_normal"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_rainbow_overlay"},
+    "components": {"computercraft:overlay": "computercraft:rainbow_flag"},
     "count": 1,
     "id": "computercraft:turtle_normal"
   }

projects/common/src/generated/resources/data/computercraft/recipe/turtle_normal_overlays/trans_flag.json

@@ -17,7 +17,7 @@
     {"item": "computercraft:turtle_normal"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_trans_overlay"},
+    "components": {"computercraft:overlay": "computercraft:trans_flag"},
     "count": 1,
     "id": "computercraft:turtle_normal"
   }

projects/common/src/main/java/dan200/computercraft/data/DataProviders.java

@@ -7,6 +7,7 @@ package dan200.computercraft.data;
 import com.mojang.serialization.Codec;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import net.minecraft.Util;
 import net.minecraft.core.HolderLookup;
 import net.minecraft.core.RegistrySetBuilder;
@@ -38,6 +39,7 @@ public final class DataProviders {
             Util.make(new RegistrySetBuilder(), builder -> {
                 builder.add(ITurtleUpgrade.REGISTRY, TurtleUpgradeProvider::addUpgrades);
                 builder.add(IPocketUpgrade.REGISTRY, PocketUpgradeProvider::addUpgrades);
+                builder.add(TurtleOverlay.REGISTRY, TurtleOverlays::register);
             }));
         var fullRegistries = fullRegistryPatch.thenApply(RegistrySetBuilder.PatchedRegistries::full);
 
@@ -57,7 +59,8 @@ public final class DataProviders {
         // and invoke that.
         try {
             Class.forName("dan200.computercraft.data.client.ClientDataProviders")
-                .getMethod("add", GeneratorSink.class).invoke(null, generator);
+                .getMethod("add", GeneratorSink.class, CompletableFuture.class)
+                .invoke(null, generator, fullRegistries);
         } catch (ReflectiveOperationException e) {
             throw new RuntimeException(e);
         }

projects/common/src/main/java/dan200/computercraft/data/RecipeProvider.java

@@ -28,6 +28,7 @@ import dan200.computercraft.shared.recipe.ImpostorShapelessRecipe;
 import dan200.computercraft.shared.recipe.TransformShapedRecipe;
 import dan200.computercraft.shared.recipe.TransformShapelessRecipe;
 import dan200.computercraft.shared.recipe.function.CopyComponents;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.items.TurtleItem;
 import dan200.computercraft.shared.turtle.recipes.TurtleUpgradeRecipe;
 import dan200.computercraft.shared.util.ColourUtils;
@@ -45,6 +46,7 @@ import net.minecraft.data.recipes.RecipeCategory;
 import net.minecraft.data.recipes.RecipeOutput;
 import net.minecraft.data.recipes.ShapedRecipeBuilder;
 import net.minecraft.data.recipes.ShapelessRecipeBuilder;
+import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.tags.ItemTags;
 import net.minecraft.tags.TagKey;
@@ -96,7 +98,7 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
         diskColours(add);
         pocketUpgrades(add, registries);
         turtleUpgrades(add, registries);
-        turtleOverlays(add);
+        turtleOverlays(add, registries);
 
         addSpecial(add, new DiskRecipe(CraftingBookCategory.MISC));
         addSpecial(add, new ColourableRecipe(CraftingBookCategory.MISC));
@@ -189,8 +191,8 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
         }
     }
 
-    private void turtleOverlays(RecipeOutput add) {
-        turtleOverlay(add, "turtle_trans_overlay", x -> x
+    private void turtleOverlays(RecipeOutput add, HolderLookup.Provider registries) {
+        turtleOverlay(add, registries, TurtleOverlays.TRANS_FLAG, x -> x
             .unlockedBy("has_dye", inventoryChange(itemPredicate(ingredients.dye())))
             .requires(ColourUtils.getDyeTag(DyeColor.LIGHT_BLUE))
             .requires(ColourUtils.getDyeTag(DyeColor.PINK))
@@ -198,7 +200,7 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
             .requires(Items.STICK)
         );
 
-        turtleOverlay(add, "turtle_rainbow_overlay", x -> x
+        turtleOverlay(add, registries, TurtleOverlays.RAINBOW_FLAG, x -> x
             .unlockedBy("has_dye", inventoryChange(itemPredicate(ingredients.dye())))
             .requires(ColourUtils.getDyeTag(DyeColor.RED))
             .requires(ColourUtils.getDyeTag(DyeColor.ORANGE))
@@ -210,14 +212,14 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
         );
     }
 
-    private void turtleOverlay(RecipeOutput add, String overlay, Consumer<ShapelessSpecBuilder> build) {
-        var overlayId = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/" + overlay);
+    private void turtleOverlay(RecipeOutput add, HolderLookup.Provider registries, ResourceKey<TurtleOverlay> overlay, Consumer<ShapelessSpecBuilder> build) {
+        var holder = registries.lookupOrThrow(overlay.registryKey()).getOrThrow(overlay);
 
         for (var turtleItem : turtleItems()) {
             var name = RegistryHelper.getKeyOrThrow(BuiltInRegistries.ITEM, turtleItem);
 
             var builder = ShapelessSpecBuilder
-                .shapeless(RecipeCategory.REDSTONE, DataComponentUtil.createStack(turtleItem, ModRegistry.DataComponents.OVERLAY.get(), overlayId))
+                .shapeless(RecipeCategory.REDSTONE, DataComponentUtil.createStack(turtleItem, ModRegistry.DataComponents.OVERLAY.get(), holder))
                 .group(name.withSuffix("_overlay").toString())
                 .unlockedBy("has_turtle", inventoryChange(turtleItem));
             build.accept(builder);
@@ -226,7 +228,7 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
                 .build(s -> new TransformShapelessRecipe(s, List.of(
                     CopyComponents.builder(turtleItem).exclude(ModRegistry.DataComponents.OVERLAY.get()).build()
                 )))
-                .save(add, name.withSuffix("_overlays/" + overlay));
+                .save(add, name.withSuffix("_overlays/" + overlay.location().getPath()));
         }
     }
 

projects/common/src/main/java/dan200/computercraft/data/TurtleOverlays.java

@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.data;
+
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
+import net.minecraft.data.worldgen.BootstrapContext;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+
+/**
+ * Built-in turtle overlays.
+ */
+final class TurtleOverlays {
+    public static final ResourceKey<TurtleOverlay> RAINBOW_FLAG = create("rainbow_flag");
+    public static final ResourceKey<TurtleOverlay> TRANS_FLAG = create("trans_flag");
+
+    private static ResourceKey<TurtleOverlay> create(String name) {
+        return ResourceKey.create(TurtleOverlay.REGISTRY, ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, name));
+    }
+
+    private TurtleOverlays() {
+    }
+
+    public static void register(BootstrapContext<TurtleOverlay> registry) {
+        registry.register(RAINBOW_FLAG, new TurtleOverlay(
+            ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_rainbow_overlay"),
+            true
+        ));
+
+        registry.register(TRANS_FLAG, new TurtleOverlay(
+            ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_trans_overlay"),
+            true
+        ));
+    }
+}

projects/common/src/main/java/dan200/computercraft/impl/ApiFactories.java

@@ -14,7 +14,6 @@ import java.util.Objects;
 /**
  * The global factory for {@link ILuaAPIFactory}s.
  *
- * @see dan200.computercraft.core.ComputerContext.Builder#apiFactories(Collection)
  * @see dan200.computercraft.api.ComputerCraftAPI#registerAPIFactory(ILuaAPIFactory)
  */
 public final class ApiFactories {

projects/common/src/main/java/dan200/computercraft/mixin/ItemStackComponentizationFixMixin.java

@@ -31,7 +31,7 @@ abstract class ItemStackComponentizationFixMixin extends DataFix {
     }
 
     @Inject(method = "fixItemStack", at = @At("TAIL"))
-    @SuppressWarnings("UnusedMethod")
+    @SuppressWarnings("unused")
     private static void fixItemStack(ItemStackComponentizationFix.ItemStackData data, Dynamic<?> ops, CallbackInfo ci) {
         ComponentizationFixers.fixItemComponents(data, ops);
     }

projects/common/src/main/java/dan200/computercraft/shared/ModRegistry.java

@@ -8,6 +8,7 @@ import com.mojang.brigadier.arguments.ArgumentType;
 import com.mojang.serialization.Codec;
 import com.mojang.serialization.MapCodec;
 import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.component.ComputerComponents;
 import dan200.computercraft.api.detail.DetailProvider;
 import dan200.computercraft.api.detail.VanillaDetailRegistries;
 import dan200.computercraft.api.media.IMedia;
@@ -26,6 +27,7 @@ import dan200.computercraft.shared.common.ClearColourRecipe;
 import dan200.computercraft.shared.common.ColourableRecipe;
 import dan200.computercraft.shared.common.DefaultBundledRedstoneProvider;
 import dan200.computercraft.shared.common.HeldItemMenu;
+import dan200.computercraft.shared.computer.apis.CommandAPI;
 import dan200.computercraft.shared.computer.blocks.CommandComputerBlock;
 import dan200.computercraft.shared.computer.blocks.ComputerBlock;
 import dan200.computercraft.shared.computer.blocks.ComputerBlockEntity;
@@ -64,6 +66,7 @@ import dan200.computercraft.shared.peripheral.speaker.SpeakerBlockEntity;
 import dan200.computercraft.shared.platform.PlatformHelper;
 import dan200.computercraft.shared.platform.RegistrationHelper;
 import dan200.computercraft.shared.platform.RegistryEntry;
+import dan200.computercraft.shared.pocket.apis.PocketAPI;
 import dan200.computercraft.shared.pocket.items.PocketComputerItem;
 import dan200.computercraft.shared.pocket.peripherals.PocketModem;
 import dan200.computercraft.shared.pocket.peripherals.PocketSpeaker;
@@ -72,8 +75,11 @@ import dan200.computercraft.shared.recipe.*;
 import dan200.computercraft.shared.recipe.function.CopyComponents;
 import dan200.computercraft.shared.recipe.function.RecipeFunction;
 import dan200.computercraft.shared.turtle.FurnaceRefuelHandler;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
+import dan200.computercraft.shared.turtle.apis.TurtleAPI;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlock;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlockEntity;
+import dan200.computercraft.shared.turtle.core.TurtleAccessInternal;
 import dan200.computercraft.shared.turtle.inventory.TurtleMenu;
 import dan200.computercraft.shared.turtle.items.TurtleItem;
 import dan200.computercraft.shared.turtle.recipes.TurtleUpgradeRecipe;
@@ -81,6 +87,7 @@ import dan200.computercraft.shared.turtle.upgrades.TurtleCraftingTable;
 import dan200.computercraft.shared.turtle.upgrades.TurtleModem;
 import dan200.computercraft.shared.turtle.upgrades.TurtleSpeaker;
 import dan200.computercraft.shared.turtle.upgrades.TurtleTool;
+import dan200.computercraft.shared.util.ComponentMap;
 import dan200.computercraft.shared.util.DataComponentUtil;
 import dan200.computercraft.shared.util.NonNegativeId;
 import net.minecraft.commands.CommandSourceStack;
@@ -95,7 +102,6 @@ import net.minecraft.network.RegistryFriendlyByteBuf;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.codec.ByteBufCodecs;
 import net.minecraft.network.codec.StreamCodec;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.flag.FeatureFlags;
 import net.minecraft.world.inventory.MenuType;
 import net.minecraft.world.item.BlockItem;
@@ -114,6 +120,7 @@ import net.minecraft.world.level.block.state.BlockBehaviour;
 import net.minecraft.world.level.material.MapColor;
 import net.minecraft.world.level.storage.loot.predicates.LootItemConditionType;
 
+import java.util.Objects;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
 import java.util.function.UnaryOperator;
@@ -320,8 +327,8 @@ public final class ModRegistry {
         /**
          * The overlay on a turtle.
          */
-        public static final RegistryEntry<DataComponentType<ResourceLocation>> OVERLAY = register("overlay", b -> b
-            .persistent(ResourceLocation.CODEC).networkSynchronized(ResourceLocation.STREAM_CODEC)
+        public static final RegistryEntry<DataComponentType<Holder<TurtleOverlay>>> OVERLAY = register("overlay", b -> b
+            .persistent(TurtleOverlay.CODEC).networkSynchronized(TurtleOverlay.STREAM_CODEC)
         );
 
         /**
@@ -579,6 +586,22 @@ public final class ModRegistry {
             return null;
         });
 
+        ComputerCraftAPI.registerAPIFactory(computer -> {
+            var turtle = computer.getComponent(ComputerComponents.TURTLE);
+            var metrics = Objects.requireNonNull(computer.getComponent(ComponentMap.METRICS));
+            return turtle == null ? null : new TurtleAPI(metrics, (TurtleAccessInternal) turtle);
+        });
+
+        ComputerCraftAPI.registerAPIFactory(computer -> {
+            var pocket = computer.getComponent(ComputerComponents.POCKET);
+            return pocket == null ? null : new PocketAPI(pocket);
+        });
+
+        ComputerCraftAPI.registerAPIFactory(computer -> {
+            var admin = computer.getComponent(ComputerComponents.ADMIN_COMPUTER);
+            return admin == null ? null : new CommandAPI(computer, admin);
+        });
+
         VanillaDetailRegistries.ITEM_STACK.addProvider(ItemDetails::fill);
         VanillaDetailRegistries.BLOCK_IN_WORLD.addProvider(BlockDetails::fill);
     }

projects/common/src/main/java/dan200/computercraft/shared/computer/apis/CommandAPI.java

@@ -6,11 +6,11 @@ package dan200.computercraft.shared.computer.apis;
 
 import com.mojang.brigadier.tree.CommandNode;
 import com.mojang.brigadier.tree.LiteralCommandNode;
+import dan200.computercraft.api.component.AdminComputer;
 import dan200.computercraft.api.detail.BlockReference;
 import dan200.computercraft.api.detail.VanillaDetailRegistries;
 import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.Logging;
-import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.util.NBTUtil;
 import net.minecraft.commands.CommandSource;
 import net.minecraft.commands.CommandSourceStack;
@@ -35,11 +35,13 @@ import java.util.*;
 public class CommandAPI implements ILuaAPI {
     private static final Logger LOG = LoggerFactory.getLogger(CommandAPI.class);
 
-    private final ServerComputer computer;
+    private final IComputerSystem computer;
+    private final AdminComputer admin;
     private final OutputReceiver receiver = new OutputReceiver();
 
-    public CommandAPI(ServerComputer computer) {
+    public CommandAPI(IComputerSystem computer, AdminComputer admin) {
         this.computer = computer;
+        this.admin = admin;
     }
 
     @Override
@@ -295,7 +297,7 @@ public class CommandAPI implements ILuaAPI {
 
         return new CommandSourceStack(receiver,
             Vec3.atCenterOf(computer.getPosition()), Vec2.ZERO,
-            computer.getLevel(), 2,
+            computer.getLevel(), admin.permissionLevel(),
             name, Component.literal(name),
             computer.getLevel().getServer(), null
         );

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/AbstractComputerBlockEntity.java

@@ -39,7 +39,7 @@ import javax.annotation.Nullable;
 import java.util.Objects;
 import java.util.UUID;
 
-public abstract class AbstractComputerBlockEntity extends BlockEntity implements IComputerBlockEntity, Nameable, MenuProvider {
+public abstract class AbstractComputerBlockEntity extends BlockEntity implements Nameable, MenuProvider {
     private static final String NBT_ID = "ComputerId";
     private static final String NBT_LABEL = "Label";
     private static final String NBT_ON = "On";
@@ -326,17 +326,14 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         for (var dir : DirectionUtil.FACINGS) updateRedstoneTo(dir);
     }
 
-    @Override
     public final int getComputerID() {
         return computerID;
     }
 
-    @Override
     public final @Nullable String getLabel() {
         return label;
     }
 
-    @Override
     public final void setComputerID(int id) {
         if (getLevel().isClientSide || computerID == id) return;
 
@@ -344,7 +341,6 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         BlockEntityHelpers.updateBlock(this);
     }
 
-    @Override
     public final void setLabel(@Nullable String label) {
         if (getLevel().isClientSide || Objects.equals(this.label, label)) return;
 
@@ -354,7 +350,6 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         BlockEntityHelpers.updateBlock(this);
     }
 
-    @Override
     public ComputerFamily getFamily() {
         return family;
     }

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/ComputerBlockEntity.java

@@ -12,6 +12,7 @@ import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.computer.inventory.ComputerMenuWithoutInventory;
 import dan200.computercraft.shared.config.Config;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.server.level.ServerLevel;
@@ -34,7 +35,8 @@ public class ComputerBlockEntity extends AbstractComputerBlockEntity {
     protected ServerComputer createComputer(int id) {
         return new ServerComputer(
             (ServerLevel) getLevel(), getBlockPos(), id, label,
-            getFamily(), Config.computerTermWidth, Config.computerTermHeight
+            getFamily(), Config.computerTermWidth, Config.computerTermHeight,
+            ComponentMap.empty()
         );
     }
 

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/IComputerBlockEntity.java

@@ -1,22 +0,0 @@
-// Copyright Daniel Ratcliffe, 2011-2022. Do not distribute without permission.
-//
-// SPDX-License-Identifier: LicenseRef-CCPL
-
-package dan200.computercraft.shared.computer.blocks;
-
-import dan200.computercraft.shared.computer.core.ComputerFamily;
-
-import javax.annotation.Nullable;
-
-public interface IComputerBlockEntity {
-    int getComputerID();
-
-    void setComputerID(int id);
-
-    @Nullable
-    String getLabel();
-
-    void setLabel(@Nullable String label);
-
-    ComputerFamily getFamily();
-}

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ComputerSystem.java

@@ -0,0 +1,101 @@
+// SPDX-FileCopyrightText: 2019 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.computer.core;
+
+import dan200.computercraft.api.component.ComputerComponent;
+import dan200.computercraft.api.lua.IComputerSystem;
+import dan200.computercraft.api.lua.ILuaAPIFactory;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.apis.ComputerAccess;
+import dan200.computercraft.core.apis.IAPIEnvironment;
+import dan200.computercraft.core.computer.ApiLifecycle;
+import dan200.computercraft.shared.util.ComponentMap;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * Implementation of {@link IComputerSystem} for usage by externally registered APIs.
+ *
+ * @see ILuaAPIFactory
+ */
+final class ComputerSystem extends ComputerAccess implements IComputerSystem, ApiLifecycle {
+    private final ServerComputer computer;
+    private final IAPIEnvironment environment;
+    private final ComponentMap components;
+
+    private boolean active;
+
+    ComputerSystem(ServerComputer computer, IAPIEnvironment environment, ComponentMap components) {
+        super(environment);
+        this.computer = computer;
+        this.environment = environment;
+        this.components = components;
+    }
+
+    void activate() {
+        active = true;
+    }
+
+    @Override
+    public void shutdown() {
+        unmountAll();
+    }
+
+    @Override
+    public String getAttachmentName() {
+        return "computer";
+    }
+
+    @Override
+    public ServerLevel getLevel() {
+        if (!active) {
+            throw new IllegalStateException("""
+                Cannot access level when constructing the API. Computers are not guaranteed to stay in one place and
+                APIs should not rely on the level remaining constant. Instead, call this method when needed.
+                """.replace('\n', ' ').strip()
+            );
+        }
+        return computer.getLevel();
+    }
+
+    @Override
+    public BlockPos getPosition() {
+        if (!active) {
+            throw new IllegalStateException("""
+                Cannot access computer position when constructing the API. Computers are not guaranteed to stay in one
+                place and APIs should not rely on the position remaining constant. Instead, call this method when
+                needed.
+                """.replace('\n', ' ').strip()
+            );
+        }
+        return computer.getPosition();
+    }
+
+    @Nullable
+    @Override
+    public String getLabel() {
+        return environment.getLabel();
+    }
+
+    @Override
+    public Map<String, IPeripheral> getAvailablePeripherals() {
+        // TODO: Should this return peripherals on the current computer?
+        return Map.of();
+    }
+
+    @Nullable
+    @Override
+    public IPeripheral getAvailablePeripheral(String name) {
+        return null;
+    }
+
+    @Override
+    public <T> @Nullable T getComponent(ComputerComponent<T> component) {
+        return components.get(component);
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ResourceMount.java

@@ -7,7 +7,6 @@ package dan200.computercraft.shared.computer.core;
 import com.google.common.annotations.VisibleForTesting;
 import dan200.computercraft.api.filesystem.FileOperationException;
 import dan200.computercraft.core.filesystem.ArchiveMount;
-import dan200.computercraft.core.filesystem.FileSystem;
 import net.minecraft.ResourceLocationException;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.MinecraftServer;
@@ -65,9 +64,10 @@ public final class ResourceMount extends ArchiveMount<ResourceMount.FileEntry> {
             existingNamespace = file.getNamespace();
 
             if (!file.getNamespace().equals(namespace)) continue;
-            if (!FileSystem.contains(subPath, file.getPath())) continue; // Some packs seem to include the parent?
 
-            var localPath = FileSystem.toLocal(file.getPath(), subPath);
+            var localPath = getLocalPath(file.getPath(), subPath);
+            if (localPath == null) continue;
+
             try {
                 getOrCreateChild(newRoot, localPath, this::createEntry);
             } catch (ResourceLocationException e) {

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ServerComputer.java

@@ -5,15 +5,16 @@
 package dan200.computercraft.shared.computer.core;
 
 import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.component.AdminComputer;
+import dan200.computercraft.api.component.ComputerComponents;
 import dan200.computercraft.api.filesystem.WritableMount;
-import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.WorkMonitor;
 import dan200.computercraft.core.computer.Computer;
 import dan200.computercraft.core.computer.ComputerEnvironment;
 import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.core.metrics.MetricsObserver;
-import dan200.computercraft.shared.computer.apis.CommandAPI;
+import dan200.computercraft.impl.ApiFactories;
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
 import dan200.computercraft.shared.computer.terminal.NetworkedTerminal;
 import dan200.computercraft.shared.computer.terminal.TerminalState;
@@ -22,6 +23,7 @@ import dan200.computercraft.shared.network.NetworkMessage;
 import dan200.computercraft.shared.network.client.ClientNetworkContext;
 import dan200.computercraft.shared.network.client.ComputerTerminalClientMessage;
 import dan200.computercraft.shared.network.server.ServerNetworking;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.core.BlockPos;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.entity.player.Player;
@@ -48,7 +50,8 @@ public class ServerComputer implements InputHandler, ComputerEnvironment {
     private int ticksSincePing;
 
     public ServerComputer(
-        ServerLevel level, BlockPos position, int computerID, @Nullable String label, ComputerFamily family, int terminalWidth, int terminalHeight
+        ServerLevel level, BlockPos position, int computerID, @Nullable String label, ComputerFamily family, int terminalWidth, int terminalHeight,
+        ComponentMap baseComponents
     ) {
         this.level = level;
         this.position = position;
@@ -58,10 +61,27 @@ public class ServerComputer implements InputHandler, ComputerEnvironment {
         terminal = new NetworkedTerminal(terminalWidth, terminalHeight, family != ComputerFamily.NORMAL, this::markTerminalChanged);
         metrics = context.metrics().createMetricObserver(this);
 
+        var componentBuilder = ComponentMap.builder();
+        componentBuilder.add(ComponentMap.METRICS, metrics);
+        if (family == ComputerFamily.COMMAND) {
+            componentBuilder.add(ComputerComponents.ADMIN_COMPUTER, new AdminComputer() {
+            });
+        }
+        componentBuilder.add(baseComponents);
+        var components = componentBuilder.build();
+
         computer = new Computer(context.computerContext(), this, terminal, computerID);
         computer.setLabel(label);
 
-        if (family == ComputerFamily.COMMAND) addAPI(new CommandAPI(this));
+        // Load in the externally registered APIs.
+        for (var factory : ApiFactories.getAll()) {
+            var system = new ComputerSystem(this, computer.getAPIEnvironment(), components);
+            var api = factory.create(system);
+            if (api == null) continue;
+
+            system.activate();
+            computer.addApi(api, system);
+        }
     }
 
     public ComputerFamily getFamily() {
@@ -211,10 +231,6 @@ public class ServerComputer implements InputHandler, ComputerEnvironment {
         computer.getEnvironment().setBundledRedstoneInput(side, combination);
     }
 
-    public void addAPI(ILuaAPI api) {
-        computer.addApi(api);
-    }
-
     public void setPeripheral(ComputerSide side, @Nullable IPeripheral peripheral) {
         computer.getEnvironment().setPeripheral(side, peripheral);
     }

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ServerContext.java

@@ -17,7 +17,6 @@ import dan200.computercraft.core.lua.ILuaMachine;
 import dan200.computercraft.core.methods.MethodSupplier;
 import dan200.computercraft.core.methods.PeripheralMethod;
 import dan200.computercraft.impl.AbstractComputerCraftAPI;
-import dan200.computercraft.impl.ApiFactories;
 import dan200.computercraft.impl.GenericSources;
 import dan200.computercraft.shared.CommonHooks;
 import dan200.computercraft.shared.computer.metrics.GlobalMetrics;
@@ -74,7 +73,6 @@ public final class ServerContext {
             .computerThreads(ConfigSpec.computerThreads.get())
             .mainThreadScheduler(mainThread)
             .luaFactory(luaMachine)
-            .apiFactories(ApiFactories.getAll())
             .genericMethods(GenericSources.getAllMethods())
             .build();
         idAssigner = new IDAssigner(storageDir.resolve("ids.json"));

projects/common/src/main/java/dan200/computercraft/shared/config/AddressRuleConfig.java

@@ -69,6 +69,13 @@ class AddressRuleConfig {
         );
     }
 
+    public static UnmodifiableConfig newRule() {
+        return makeRule(config -> {
+            config.add("host", "example.com");
+            config.add("action", Action.DENY.name().toLowerCase(Locale.ROOT));
+        });
+    }
+
     private static UnmodifiableConfig makeRule(Consumer<CommentedConfig> setup) {
         var config = InMemoryCommentedFormat.defaultInstance().createConfig(LinkedHashMap::new);
         setup.accept(config);

projects/common/src/main/java/dan200/computercraft/shared/config/ConfigFile.java

@@ -126,7 +126,7 @@ public interface ConfigFile {
 
         public abstract ConfigFile.Value<Integer> defineInRange(String path, int defaultValue, int min, int max);
 
-        public abstract <T> ConfigFile.Value<List<? extends T>> defineList(String path, List<? extends T> defaultValue, Predicate<Object> elementValidator);
+        public abstract <T> ConfigFile.Value<List<? extends T>> defineList(String path, List<? extends T> defaultValue, Supplier<T> newValue, Predicate<Object> elementValidator);
 
         public abstract <V extends Enum<V>> ConfigFile.Value<V> defineEnum(String path, V defaultValue);
 

projects/common/src/main/java/dan200/computercraft/shared/config/ConfigSpec.java

@@ -145,7 +145,7 @@ public final class ConfigSpec {
                     or a single method (computercraft:inventory#pushItems).
                     """)
                 .worldRestart()
-                .defineList("disabled_generic_methods", List.of(), x -> x instanceof String);
+                .defineList("disabled_generic_methods", List.of(), () -> "", x -> x instanceof String);
         }
 
         {
@@ -214,7 +214,7 @@ public final class ConfigSpec {
                      - "max_websocket_message" (optional): The maximum size (in bytes) that a computer can send or
                        receive in one websocket packet.
                      - "use_proxy" (optional): Enable use of the HTTP/SOCKS proxy if it is configured.""")
-                .defineList("rules", AddressRuleConfig.defaultRules(), x -> x instanceof UnmodifiableConfig);
+                .defineList("rules", AddressRuleConfig.defaultRules(), AddressRuleConfig::newRule, x -> x instanceof UnmodifiableConfig);
 
             httpMaxRequests = builder
                 .comment("""

projects/common/src/main/java/dan200/computercraft/shared/data/HasComputerIdLootCondition.java

@@ -5,7 +5,7 @@
 package dan200.computercraft.shared.data;
 
 import dan200.computercraft.shared.ModRegistry;
-import dan200.computercraft.shared.computer.blocks.IComputerBlockEntity;
+import dan200.computercraft.shared.computer.blocks.AbstractComputerBlockEntity;
 import net.minecraft.world.level.storage.loot.LootContext;
 import net.minecraft.world.level.storage.loot.parameters.LootContextParam;
 import net.minecraft.world.level.storage.loot.parameters.LootContextParams;
@@ -27,7 +27,7 @@ public final class HasComputerIdLootCondition implements LootItemCondition {
     @Override
     public boolean test(LootContext lootContext) {
         var tile = lootContext.getParamOrNull(LootContextParams.BLOCK_ENTITY);
-        return tile instanceof IComputerBlockEntity computer && computer.getComputerID() >= 0;
+        return tile instanceof AbstractComputerBlockEntity computer && computer.getComputerID() >= 0;
     }
 
     @Override

projects/common/src/main/java/dan200/computercraft/shared/integration/CreateIntegration.java

@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.integration;
+
+import com.simibubi.create.content.contraptions.BlockMovementChecks;
+import com.simibubi.create.content.contraptions.BlockMovementChecks.CheckResult;
+import dan200.computercraft.shared.peripheral.modem.wired.CableBlock;
+import dan200.computercraft.shared.peripheral.modem.wireless.WirelessModemBlock;
+
+/**
+ * Integration with Create.
+ */
+public final class CreateIntegration {
+    public static final String ID = "create";
+
+    private CreateIntegration() {
+    }
+
+    public static void setup() {
+        // Allow modems to be treated as "attached" to their adjacent block.
+        BlockMovementChecks.registerAttachedCheck((state, world, pos, direction) -> {
+            var block = state.getBlock();
+            if (block instanceof WirelessModemBlock) {
+                return CheckResult.of(state.getValue(WirelessModemBlock.FACING) == direction);
+            } else if (block instanceof CableBlock) {
+                return CheckResult.of(state.getValue(CableBlock.MODEM).getFacing() == direction);
+            } else {
+                return CheckResult.PASS;
+            }
+        });
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/integration/ExternalModTags.java

@@ -8,6 +8,7 @@ import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
 
 /**
  * Tags defined by external mods.
@@ -26,9 +27,9 @@ public final class ExternalModTags {
         /**
          * Create's "brittle" tag, used to determine if this block needs to be moved before its neighbours.
          *
-         * @see <a href="https://github.com/Creators-of-Create/Create/blob/mc1.20.1/dev/src/main/java/com/simibubi/create/content/contraptions/BlockMovementChecks.java">{@code BlockMovementChecks}</a>
+         * @see com.simibubi.create.content.contraptions.BlockMovementChecks#isBrittle(BlockState)
          */
-        public static final TagKey<Block> CREATE_BRITTLE = make("create", "brittle");
+        public static final TagKey<Block> CREATE_BRITTLE = make(CreateIntegration.ID, "brittle");
 
         private static TagKey<Block> make(String mod, String name) {
             return TagKey.create(Registries.BLOCK, ResourceLocation.fromNamespaceAndPath(mod, name));

projects/common/src/main/java/dan200/computercraft/shared/network/client/PocketComputerDataMessage.java

@@ -43,7 +43,7 @@ public record PocketComputerDataMessage(
         this(
             computer.getInstanceUUID(),
             computer.getState(),
-            computer.getLight(),
+            computer.getBrain().getLight(),
             sendTerminal ? Optional.of(computer.getTerminalState()) : Optional.empty()
         );
     }

projects/common/src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java

@@ -276,16 +276,18 @@ public abstract class SpeakerPeripheral implements IPeripheral {
      * Attempt to stream some audio data to the speaker.
      * <p>
      * This accepts a list of audio samples as amplitudes between -128 and 127. These are stored in an internal buffer
-     * and played back at 48kHz. If this buffer is full, this function will return {@literal false}. You should wait for
-     * a [`speaker_audio_empty`] event before trying again.
+     * and played back at 48kHz. If this buffer is full, this function will return {@literal false}. Programs should
+     * wait for a [`speaker_audio_empty`] event before trying to play audio again.
      * <p>
-     * > [!NOTE]
-     * > The speaker only buffers a single call to {@link #playAudio} at once. This means if you try to play a small
-     * > number of samples, you'll have a lot of stutter. You should try to play as many samples in one call as possible
-     * > (up to 128×1024), as this reduces the chances of audio stuttering or halting, especially when the server or
-     * > computer is lagging.
+     * The speaker only buffers a single call to {@link #playAudio} at once. This means if you try to play a small
+     * number of samples, you'll have a lot of stutter. You should try to play as many samples in one call as possible
+     * (up to 128×1024), as this reduces the chances of audio stuttering or halting, especially when the server or
+     * computer is lagging.
      * <p>
-     * [`speaker_audio`] provides a more complete guide to using speakers
+     * While the speaker accepts 8-bit PCM audio, the audio stream is re-encoded before being played. This means that
+     * the supplied samples may not be played out exactly.
+     * <p>
+     * [`speaker_audio`] provides a more complete guide to using speakers.
      *
      * @param context The Lua context.
      * @param audio   The audio data to play.

projects/common/src/main/java/dan200/computercraft/shared/pocket/apis/PocketAPI.java

@@ -6,10 +6,10 @@ package dan200.computercraft.shared.pocket.apis;
 
 import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.api.pocket.IPocketAccess;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.api.upgrades.UpgradeData;
 import dan200.computercraft.impl.PocketUpgrades;
-import dan200.computercraft.shared.pocket.core.PocketServerComputer;
 import net.minecraft.core.NonNullList;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
@@ -34,10 +34,10 @@ import java.util.Objects;
  * @cc.module pocket
  */
 public class PocketAPI implements ILuaAPI {
-    private final PocketServerComputer computer;
+    private final IPocketAccess pocket;
 
-    public PocketAPI(PocketServerComputer computer) {
-        this.computer = computer;
+    public PocketAPI(IPocketAccess pocket) {
+        this.pocket = pocket;
     }
 
     @Override
@@ -56,10 +56,10 @@ public class PocketAPI implements ILuaAPI {
      */
     @LuaFunction(mainThread = true)
     public final Object[] equipBack() {
-        var entity = computer.getEntity();
+        var entity = pocket.getEntity();
         if (!(entity instanceof Player player)) return new Object[]{ false, "Cannot find player" };
         var inventory = player.getInventory();
-        var previousUpgrade = computer.getUpgrade();
+        var previousUpgrade = pocket.getUpgrade();
 
         // Attempt to find the upgrade, starting in the main segment, and then looking in the opposite
         // one. We start from the position the item is currently in and loop round to the start.
@@ -73,7 +73,7 @@ public class PocketAPI implements ILuaAPI {
         if (previousUpgrade != null) storeItem(player, previousUpgrade.getUpgradeItem());
 
         // Set the new upgrade
-        computer.setUpgrade(newUpgrade);
+        pocket.setUpgrade(newUpgrade);
 
         return new Object[]{ true };
     }
@@ -87,13 +87,13 @@ public class PocketAPI implements ILuaAPI {
      */
     @LuaFunction(mainThread = true)
     public final Object[] unequipBack() {
-        var entity = computer.getEntity();
+        var entity = pocket.getEntity();
         if (!(entity instanceof Player player)) return new Object[]{ false, "Cannot find player" };
-        var previousUpgrade = computer.getUpgrade();
+        var previousUpgrade = pocket.getUpgrade();
 
         if (previousUpgrade == null) return new Object[]{ false, "Nothing to unequip" };
 
-        computer.setUpgrade(null);
+        pocket.setUpgrade(null);
 
         storeItem(player, previousUpgrade.getUpgradeItem());
 
@@ -111,7 +111,7 @@ public class PocketAPI implements ILuaAPI {
         for (var i = 0; i < inv.size(); i++) {
             var invStack = inv.get((i + start) % inv.size());
             if (!invStack.isEmpty()) {
-                var newUpgrade = PocketUpgrades.instance().get(computer.getLevel().registryAccess(), invStack);
+                var newUpgrade = PocketUpgrades.instance().get(pocket.getLevel().registryAccess(), invStack);
 
                 if (newUpgrade != null && !Objects.equals(newUpgrade, previous)) {
                     // Consume an item from this stack and exit the loop

projects/common/src/main/java/dan200/computercraft/shared/pocket/core/PocketBrain.java

@@ -0,0 +1,176 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.pocket.core;
+
+import dan200.computercraft.api.pocket.IPocketAccess;
+import dan200.computercraft.api.pocket.IPocketUpgrade;
+import dan200.computercraft.api.upgrades.UpgradeData;
+import dan200.computercraft.core.computer.ComputerSide;
+import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.network.client.PocketComputerDataMessage;
+import dan200.computercraft.shared.network.server.ServerNetworking;
+import dan200.computercraft.shared.pocket.items.PocketComputerItem;
+import net.minecraft.core.component.DataComponentPatch;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.component.DyedItemColor;
+import net.minecraft.world.phys.Vec3;
+
+import javax.annotation.Nullable;
+
+/**
+ * Holds additional state for a pocket computer. This includes pocket computer upgrade,
+ * {@linkplain IPocketAccess#getLight() light colour} and {@linkplain IPocketAccess#getColour() colour}.
+ * <p>
+ * This state is read when the brain is created, and written back to the holding item stack when the holding entity is
+ * ticked (see {@link #updateItem(ItemStack)}).
+ */
+public final class PocketBrain implements IPocketAccess {
+    private final PocketServerComputer computer;
+
+    private PocketHolder holder;
+    private Vec3 position;
+
+    private boolean dirty = false;
+    private @Nullable UpgradeData<IPocketUpgrade> upgrade;
+    private int colour = -1;
+    private int lightColour = -1;
+
+    public PocketBrain(PocketHolder holder, int computerID, @Nullable String label, ComputerFamily family, @Nullable UpgradeData<IPocketUpgrade> upgrade) {
+        this.computer = new PocketServerComputer(this, holder, computerID, label, family);
+        this.holder = holder;
+        this.position = holder.pos();
+        this.upgrade = upgrade;
+        invalidatePeripheral();
+    }
+
+    /**
+     * Get the corresponding pocket computer for this brain.
+     *
+     * @return The pocket computer.
+     */
+    public PocketServerComputer computer() {
+        return computer;
+    }
+
+    PocketHolder holder() {
+        return holder;
+    }
+
+    /**
+     * Update the position and holder for this computer.
+     *
+     * @param newHolder The new holder
+     */
+    public void updateHolder(PocketHolder newHolder) {
+        position = newHolder.pos();
+        computer.setPosition(newHolder.level(), newHolder.blockPos());
+
+        var oldHolder = this.holder;
+        if (holder.equals(newHolder)) return;
+        holder = newHolder;
+
+        // If a new player has picked it up then rebroadcast the terminal to them
+        var oldPlayer = oldHolder instanceof PocketHolder.PlayerHolder p ? p.entity() : null;
+        if (newHolder instanceof PocketHolder.PlayerHolder player && player.entity() != oldPlayer) {
+            ServerNetworking.sendToPlayer(new PocketComputerDataMessage(computer, true), player.entity());
+        }
+    }
+
+    /**
+     * Write back properties of the pocket brain to the item.
+     *
+     * @param stack The pocket computer stack to update.
+     * @return Whether the item was changed.
+     */
+    public boolean updateItem(ItemStack stack) {
+        if (!dirty) return false;
+        this.dirty = false;
+
+        stack.set(DataComponents.DYED_COLOR, colour == -1 ? null : new DyedItemColor(colour, false));
+        PocketComputerItem.setUpgrade(stack, upgrade);
+        return true;
+    }
+
+    @Override
+    public ServerLevel getLevel() {
+        return computer.getLevel();
+    }
+
+    @Override
+    public Vec3 getPosition() {
+        // This method can be called from off-thread, and so we must use the cached position rather than rereading
+        // from the holder.
+        return position;
+    }
+
+    @Override
+    public @Nullable Entity getEntity() {
+        return holder instanceof PocketHolder.EntityHolder entity && holder.isValid(computer) ? entity.entity() : null;
+    }
+
+    @Override
+    public int getColour() {
+        return colour;
+    }
+
+    @Override
+    public void setColour(int colour) {
+        if (this.colour == colour) return;
+        dirty = true;
+        this.colour = colour;
+    }
+
+    @Override
+    public int getLight() {
+        return lightColour;
+    }
+
+    @Override
+    public void setLight(int colour) {
+        if (colour < 0 || colour > 0xFFFFFF) colour = -1;
+        lightColour = colour;
+    }
+
+    @Override
+    public DataComponentPatch getUpgradeData() {
+        var upgrade = this.upgrade;
+        return upgrade == null ? DataComponentPatch.EMPTY : upgrade.data();
+    }
+
+    @Override
+    public void setUpgradeData(DataComponentPatch data) {
+        var upgrade = this.upgrade;
+        if (upgrade == null) return;
+        this.upgrade = UpgradeData.of(upgrade.holder(), data);
+    }
+
+    @Override
+    public void invalidatePeripheral() {
+        var peripheral = upgrade == null ? null : upgrade.upgrade().createPeripheral(this);
+        computer.setPeripheral(ComputerSide.BACK, peripheral);
+    }
+
+    @Override
+    public @Nullable UpgradeData<IPocketUpgrade> getUpgrade() {
+        return upgrade;
+    }
+
+    /**
+     * Set the upgrade for this pocket computer, also updating the item stack.
+     * <p>
+     * Note this method is not thread safe - it must be called from the server thread.
+     *
+     * @param upgrade The new upgrade to set it to, may be {@code null}.
+     */
+    @Override
+    public void setUpgrade(@Nullable UpgradeData<IPocketUpgrade> upgrade) {
+        this.upgrade = upgrade;
+        dirty = true;
+        invalidatePeripheral();
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/pocket/core/PocketHolder.java

@@ -0,0 +1,115 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.pocket.core;
+
+import dan200.computercraft.shared.computer.core.ServerComputer;
+import dan200.computercraft.shared.pocket.items.PocketComputerItem;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.phys.Vec3;
+
+/**
+ * An object that holds a pocket computer item.
+ */
+public sealed interface PocketHolder permits PocketHolder.EntityHolder {
+    /**
+     * The level this holder is in.
+     *
+     * @return The holder's level.
+     */
+    ServerLevel level();
+
+    /**
+     * The position of this holder.
+     *
+     * @return The position of this holder.
+     */
+    Vec3 pos();
+
+    /**
+     * The block position of this holder.
+     *
+     * @return The position of this holder.
+     */
+    BlockPos blockPos();
+
+    /**
+     * Determine if this holder is still valid for a particular computer.
+     *
+     * @param computer The current computer.
+     * @return Whether this holder is valid.
+     */
+    boolean isValid(ServerComputer computer);
+
+    /**
+     * Mark the pocket computer item as having changed.
+     */
+    void setChanged();
+
+    /**
+     * An {@link Entity} holding a pocket computer.
+     */
+    sealed interface EntityHolder extends PocketHolder permits PocketHolder.PlayerHolder, PocketHolder.ItemEntityHolder {
+        /**
+         * Get the entity holding this pocket computer.
+         *
+         * @return The holding entity.
+         */
+        Entity entity();
+
+        @Override
+        default ServerLevel level() {
+            return (ServerLevel) entity().level();
+        }
+
+        @Override
+        default Vec3 pos() {
+            return entity().getEyePosition();
+        }
+
+        @Override
+        default BlockPos blockPos() {
+            return entity().blockPosition();
+        }
+    }
+
+    /**
+     * A pocket computer in a player's slot.
+     *
+     * @param entity The current player.
+     * @param slot   The slot the pocket computer is in.
+     */
+    record PlayerHolder(ServerPlayer entity, int slot) implements EntityHolder {
+        @Override
+        public boolean isValid(ServerComputer computer) {
+            return entity().isAlive() && PocketComputerItem.isServerComputer(computer, entity().getInventory().getItem(this.slot()));
+        }
+
+        @Override
+        public void setChanged() {
+            entity.getInventory().setChanged();
+        }
+    }
+
+    /**
+     * A pocket computer in an {@link ItemEntity}.
+     *
+     * @param entity The item entity.
+     */
+    record ItemEntityHolder(ItemEntity entity) implements EntityHolder {
+        @Override
+        public boolean isValid(ServerComputer computer) {
+            return entity().isAlive() && PocketComputerItem.isServerComputer(computer, this.entity().getItem());
+        }
+
+        @Override
+        public void setChanged() {
+            entity.setItem(entity.getItem().copy());
+        }
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/pocket/core/PocketServerComputer.java

@@ -4,11 +4,7 @@
 
 package dan200.computercraft.shared.pocket.core;
 
-import dan200.computercraft.api.pocket.IPocketAccess;
-import dan200.computercraft.api.pocket.IPocketUpgrade;
-import dan200.computercraft.api.upgrades.UpgradeData;
-import dan200.computercraft.core.computer.ComputerSide;
-import dan200.computercraft.shared.ModRegistry;
+import dan200.computercraft.api.component.ComputerComponents;
 import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerComputer;
@@ -17,176 +13,81 @@ import dan200.computercraft.shared.network.client.PocketComputerDataMessage;
 import dan200.computercraft.shared.network.client.PocketComputerDeletedClientMessage;
 import dan200.computercraft.shared.network.server.ServerNetworking;
 import dan200.computercraft.shared.pocket.items.PocketComputerItem;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.component.DataComponentPatch;
-import net.minecraft.core.component.DataComponents;
-import net.minecraft.server.level.ServerLevel;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.server.level.ServerPlayer;
-import net.minecraft.world.entity.Entity;
-import net.minecraft.world.entity.LivingEntity;
-import net.minecraft.world.entity.item.ItemEntity;
-import net.minecraft.world.entity.player.Player;
-import net.minecraft.world.item.ItemStack;
-import net.minecraft.world.item.component.DyedItemColor;
+import net.minecraft.world.level.ChunkPos;
 
 import javax.annotation.Nullable;
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.List;
 import java.util.Set;
 
-public class PocketServerComputer extends ServerComputer implements IPocketAccess {
-    private @Nullable IPocketUpgrade upgrade;
-    private @Nullable Entity entity;
-    private ItemStack stack = ItemStack.EMPTY;
-
-    private int lightColour = -1;
+/**
+ * A {@link ServerComputer}-subclass for {@linkplain PocketComputerItem pocket computers}.
+ * <p>
+ * This extends default {@link ServerComputer} behaviour by also syncing pocket computer state to nearby players, and
+ * syncing the terminal to the current player.
+ * <p>
+ * The actual pocket computer state (upgrade, light) is maintained in {@link PocketBrain}. The two classes are tightly
+ * coupled, and maintain a reference to each other.
+ *
+ * @see PocketComputerDataMessage
+ * @see PocketComputerDeletedClientMessage
+ */
+public final class PocketServerComputer extends ServerComputer {
+    private final PocketBrain brain;
 
     // The state the previous tick, used to determine if the state needs to be sent to the client.
     private int oldLightColour = -1;
     private @Nullable ComputerState oldComputerState;
 
-    private final Set<ServerPlayer> tracking = new HashSet<>();
+    private Set<ServerPlayer> tracking = Set.of();
 
-    public PocketServerComputer(ServerLevel world, BlockPos position, int computerID, @Nullable String label, ComputerFamily family) {
-        super(world, position, computerID, label, family, Config.pocketTermWidth, Config.pocketTermHeight);
+    PocketServerComputer(PocketBrain brain, PocketHolder holder, int computerID, @Nullable String label, ComputerFamily family) {
+        super(
+            holder.level(), holder.blockPos(), computerID, label, family, Config.pocketTermWidth, Config.pocketTermHeight,
+            ComponentMap.builder().add(ComputerComponents.POCKET, brain).build()
+        );
+        this.brain = brain;
     }
 
-    @Nullable
-    @Override
-    public Entity getEntity() {
-        var entity = this.entity;
-        if (entity == null || stack.isEmpty() || !entity.isAlive()) return null;
-
-        if (entity instanceof Player) {
-            var inventory = ((Player) entity).getInventory();
-            return inventory.items.contains(stack) || inventory.offhand.contains(stack) ? entity : null;
-        } else if (entity instanceof LivingEntity living) {
-            return living.getMainHandItem() == stack || living.getOffhandItem() == stack ? entity : null;
-        } else if (entity instanceof ItemEntity itemEntity) {
-            return itemEntity.getItem() == stack ? entity : null;
-        } else {
-            return null;
-        }
-    }
-
-    @Override
-    public int getColour() {
-        return DyedItemColor.getOrDefault(stack, -1);
-    }
-
-    @Override
-    public void setColour(int colour) {
-        stack.set(DataComponents.DYED_COLOR, colour == -1 ? null : new DyedItemColor(colour, false));
-        setItemChanged();
-    }
-
-    @Override
-    public int getLight() {
-        return lightColour;
-    }
-
-    @Override
-    public void setLight(int colour) {
-        if (colour < 0 || colour > 0xFFFFFF) colour = -1;
-        lightColour = colour;
-    }
-
-    @Override
-    public DataComponentPatch getUpgradeData() {
-        var upgrade = PocketComputerItem.getUpgradeWithData(stack);
-        return upgrade == null ? DataComponentPatch.EMPTY : upgrade.data();
-    }
-
-    @Override
-    public void setUpgradeData(DataComponentPatch data) {
-        var upgrade = PocketComputerItem.getUpgradeWithData(stack);
-        if (upgrade == null) return;
-
-        PocketComputerItem.setUpgrade(stack, new UpgradeData<>(upgrade.holder(), data));
-        setItemChanged();
-    }
-
-    private void setItemChanged() {
-        if (entity instanceof Player player) player.getInventory().setChanged();
-    }
-
-    @Override
-    public void invalidatePeripheral() {
-        var peripheral = upgrade == null ? null : upgrade.createPeripheral(this);
-        setPeripheral(ComputerSide.BACK, peripheral);
-    }
-
-    public @Nullable UpgradeData<IPocketUpgrade> getUpgrade() {
-        return PocketComputerItem.getUpgradeWithData(stack);
-    }
-
-    /**
-     * Set the upgrade for this pocket computer, also updating the item stack.
-     * <p>
-     * Note this method is not thread safe - it must be called from the server thread.
-     *
-     * @param upgrade The new upgrade to set it to, may be {@code null}.
-     */
-    public void setUpgrade(@Nullable UpgradeData<IPocketUpgrade> upgrade) {
-        synchronized (this) {
-            stack.set(ModRegistry.DataComponents.POCKET_UPGRADE.get(), upgrade);
-            setItemChanged();
-            this.upgrade = upgrade == null ? null : upgrade.upgrade();
-            invalidatePeripheral();
-        }
-    }
-
-    public synchronized void updateValues(@Nullable Entity entity, ItemStack stack, @Nullable IPocketUpgrade upgrade) {
-        if (entity != null) setPosition((ServerLevel) entity.level(), entity.blockPosition());
-
-        // If a new entity has picked it up then rebroadcast the terminal to them
-        if (entity != this.entity && entity instanceof ServerPlayer) markTerminalChanged();
-
-        this.entity = entity;
-        this.stack = stack;
-
-        if (this.upgrade != upgrade) {
-            this.upgrade = upgrade;
-            invalidatePeripheral();
-        }
+    public PocketBrain getBrain() {
+        return brain;
     }
 
     @Override
     protected void tickServer() {
         super.tickServer();
 
-        // Find any players which have gone missing and remove them from the tracking list.
-        tracking.removeIf(player -> !player.isAlive() || player.level() != getLevel());
+        // Get the new set of players tracking the current position.
+        var newTracking = getLevel().getChunkSource().chunkMap.getPlayers(new ChunkPos(getPosition()), false);
+        var trackingChanged = tracking.size() != newTracking.size() || !tracking.containsAll(newTracking);
 
         // And now find any new players, add them to the tracking list, and broadcast state where appropriate.
         var state = getState();
-        if (oldLightColour != lightColour || oldComputerState != state) {
+        var light = brain.getLight();
+        if (oldLightColour != light || oldComputerState != state) {
             oldComputerState = state;
-            oldLightColour = lightColour;
+            oldLightColour = light;
 
             // Broadcast the state to all players
-            tracking.addAll(getLevel().players());
-            ServerNetworking.sendToPlayers(new PocketComputerDataMessage(this, false), tracking);
-        } else {
+            ServerNetworking.sendToPlayers(new PocketComputerDataMessage(this, false), newTracking);
+        } else if (trackingChanged) {
             // Broadcast the state to new players.
-            List<ServerPlayer> added = new ArrayList<>();
-            for (var player : getLevel().players()) {
-                if (tracking.add(player)) added.add(player);
-            }
+            var added = newTracking.stream().filter(x -> !tracking.contains(x)).toList();
             if (!added.isEmpty()) {
                 ServerNetworking.sendToPlayers(new PocketComputerDataMessage(this, false), added);
             }
         }
+
+        if (trackingChanged) tracking = Set.copyOf(newTracking);
     }
 
     @Override
     protected void onTerminalChanged() {
         super.onTerminalChanged();
 
-        if (entity instanceof ServerPlayer player && entity.isAlive()) {
+        if (brain.holder() instanceof PocketHolder.PlayerHolder holder && holder.isValid(this)) {
             // Broadcast the terminal to the current player.
-            ServerNetworking.sendToPlayer(new PocketComputerDataMessage(this, true), player);
+            ServerNetworking.sendToPlayer(new PocketComputerDataMessage(this, true), holder.entity());
         }
     }
 

projects/common/src/main/java/dan200/computercraft/shared/pocket/items/PocketComputerItem.java

@@ -14,22 +14,26 @@ import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.impl.PocketUpgrades;
 import dan200.computercraft.shared.ModRegistry;
 import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.computer.core.ServerComputer;
+import dan200.computercraft.shared.computer.core.ServerComputerRegistry;
 import dan200.computercraft.shared.computer.core.ServerContext;
 import dan200.computercraft.shared.computer.items.ServerComputerReference;
 import dan200.computercraft.shared.config.Config;
 import dan200.computercraft.shared.network.container.ComputerContainerData;
-import dan200.computercraft.shared.pocket.apis.PocketAPI;
+import dan200.computercraft.shared.pocket.core.PocketBrain;
+import dan200.computercraft.shared.pocket.core.PocketHolder;
 import dan200.computercraft.shared.pocket.core.PocketServerComputer;
 import dan200.computercraft.shared.pocket.inventory.PocketComputerMenuProvider;
 import dan200.computercraft.shared.util.DataComponentUtil;
 import dan200.computercraft.shared.util.IDAssigner;
+import dan200.computercraft.shared.util.InventoryUtil;
 import dan200.computercraft.shared.util.NonNegativeId;
 import net.minecraft.ChatFormatting;
 import net.minecraft.core.HolderLookup;
 import net.minecraft.network.chat.Component;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.Container;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.InteractionResultHolder;
@@ -53,12 +57,33 @@ public class PocketComputerItem extends Item implements IMedia {
         this.family = family;
     }
 
-    private boolean tick(ItemStack stack, Entity entity, PocketServerComputer computer) {
-        var upgrade = getUpgrade(stack);
+    /**
+     * Tick a pocket computer.
+     *
+     * @param stack  The current pocket computer stack.
+     * @param holder The entity holding the pocket item.
+     * @param brain  The pocket computer brain.
+     */
+    private void tick(ItemStack stack, PocketHolder holder, PocketBrain brain) {
+        brain.updateHolder(holder);
 
-        computer.updateValues(entity, stack, upgrade);
+        // Update pocket upgrade
+        var upgrade = brain.getUpgrade();
+        if (upgrade != null) upgrade.upgrade().update(brain, brain.computer().getPeripheral(ComputerSide.BACK));
 
-        var changed = false;
+        if (updateItem(stack, brain)) holder.setChanged();
+    }
+
+    /**
+     * Copy properties from the brain back to the item stack.
+     *
+     * @param stack The current pocket computer stack.
+     * @param brain The current pocket brain.
+     * @return Whether the item was changed.
+     */
+    private boolean updateItem(ItemStack stack, PocketBrain brain) {
+        var changed = brain.updateItem(stack);
+        var computer = brain.computer();
 
         // Sync label
         var label = computer.getLabel();
@@ -73,21 +98,20 @@ public class PocketComputerItem extends Item implements IMedia {
             stack.set(ModRegistry.DataComponents.ON.get(), on);
         }
 
-        // Update pocket upgrade
-        if (upgrade != null) upgrade.update(computer, computer.getPeripheral(ComputerSide.BACK));
-
         return changed;
     }
 
     @Override
     public void inventoryTick(ItemStack stack, Level world, Entity entity, int slotNum, boolean selected) {
-        if (world.isClientSide) return;
-        Container inventory = entity instanceof Player player ? player.getInventory() : null;
-        var computer = createServerComputer((ServerLevel) world, entity, inventory, stack);
-        computer.keepAlive();
+        // This (in vanilla at least) is only called for players. Don't bother to handle other entities.
+        if (world.isClientSide || !(entity instanceof ServerPlayer player)) return;
 
-        var changed = tick(stack, entity, computer);
-        if (changed && inventory != null) inventory.setChanged();
+        // If we're in the inventory, create a computer and keep it alive.
+        var holder = new PocketHolder.PlayerHolder(player, slotNum);
+        var brain = getOrCreateBrain((ServerLevel) world, holder, stack);
+        brain.computer().keepAlive();
+
+        tick(stack, holder, brain);
     }
 
     @ForgeOverride
@@ -95,8 +119,11 @@ public class PocketComputerItem extends Item implements IMedia {
         var level = entity.level();
         if (level.isClientSide || level.getServer() == null) return false;
 
+        // If we're an item entity, tick an already existing computer (as to update the position), but do not keep the
+        // computer alive.
         var computer = getServerComputer(level.getServer(), stack);
-        if (computer != null && tick(stack, entity, computer)) entity.setItem(stack.copy());
+        if (computer != null) tick(stack, new PocketHolder.ItemEntityHolder(entity), computer.getBrain());
+
         return false;
     }
 
@@ -104,14 +131,18 @@ public class PocketComputerItem extends Item implements IMedia {
     public InteractionResultHolder<ItemStack> use(Level world, Player player, InteractionHand hand) {
         var stack = player.getItemInHand(hand);
         if (!world.isClientSide) {
-            var computer = createServerComputer((ServerLevel) world, player, player.getInventory(), stack);
+            var holder = new PocketHolder.PlayerHolder((ServerPlayer) player, InventoryUtil.getHandSlot(player, hand));
+            var brain = getOrCreateBrain((ServerLevel) world, holder, stack);
+            var computer = brain.computer();
             computer.turnOn();
 
             var stop = false;
             var upgrade = getUpgrade(stack);
             if (upgrade != null) {
-                computer.updateValues(player, stack, upgrade);
-                stop = upgrade.onRightClick(world, computer, computer.getPeripheral(ComputerSide.BACK));
+                brain.updateHolder(holder);
+                stop = upgrade.onRightClick(world, brain, computer.getPeripheral(ComputerSide.BACK));
+                // Sync back just in case. We don't need to setChanged, as we'll return the item anyway.
+                updateItem(stack, brain);
             }
 
             if (!stop) {
@@ -153,34 +184,42 @@ public class PocketComputerItem extends Item implements IMedia {
 
     }
 
-    public PocketServerComputer createServerComputer(ServerLevel level, Entity entity, @Nullable Container inventory, ItemStack stack) {
-
+    private PocketBrain getOrCreateBrain(ServerLevel level, PocketHolder holder, ItemStack stack) {
         var registry = ServerContext.get(level.getServer()).registry();
-        var computer = (PocketServerComputer) ServerComputerReference.get(stack, registry);
-        if (computer == null) {
-            var computerID = NonNegativeId.getOrCreate(level.getServer(), stack, ModRegistry.DataComponents.COMPUTER_ID.get(), IDAssigner.COMPUTER);
-            computer = new PocketServerComputer(level, entity.blockPosition(), computerID, getLabel(stack), getFamily());
-
-            var instanceId = computer.register();
-            stack.set(ModRegistry.DataComponents.COMPUTER.get(), new ServerComputerReference(registry.getSessionID(), instanceId));
-
-            var upgrade = getUpgrade(stack);
-
-            computer.updateValues(entity, stack, upgrade);
-            computer.addAPI(new PocketAPI(computer));
-
-            // Only turn on when initially creating the computer, rather than each tick.
-            if (isMarkedOn(stack) && entity instanceof Player) computer.turnOn();
-
-            if (inventory != null) inventory.setChanged();
+        {
+            var computer = getServerComputer(registry, stack);
+            if (computer != null) return computer.getBrain();
         }
 
-        return computer;
+        var computerID = NonNegativeId.getOrCreate(level.getServer(), stack, ModRegistry.DataComponents.COMPUTER_ID.get(), IDAssigner.COMPUTER);
+        var brain = new PocketBrain(holder, computerID, getLabel(stack), getFamily(), getUpgradeWithData(stack));
+        var computer = brain.computer();
+
+        stack.set(ModRegistry.DataComponents.COMPUTER.get(), new ServerComputerReference(registry.getSessionID(), computer.register()));
+
+        // Only turn on when initially creating the computer, rather than each tick.
+        if (isMarkedOn(stack) && holder instanceof PocketHolder.PlayerHolder) computer.turnOn();
+
+        updateItem(stack, brain);
+
+        holder.setChanged();
+
+        return brain;
+    }
+
+    public static boolean isServerComputer(ServerComputer computer, ItemStack stack) {
+        return stack.getItem() instanceof PocketComputerItem
+            && getServerComputer(computer.getLevel().getServer(), stack) == computer;
+    }
+
+    @Nullable
+    public static PocketServerComputer getServerComputer(ServerComputerRegistry registry, ItemStack stack) {
+        return (PocketServerComputer) ServerComputerReference.get(stack, registry);
     }
 
     @Nullable
     public static PocketServerComputer getServerComputer(MinecraftServer server, ItemStack stack) {
-        return (PocketServerComputer) ServerComputerReference.get(stack, ServerContext.get(server).registry());
+        return getServerComputer(ServerContext.get(server).registry(), stack);
     }
 
     public ComputerFamily getFamily() {

projects/common/src/main/java/dan200/computercraft/shared/pocket/peripherals/PocketModem.java

@@ -41,8 +41,6 @@ public class PocketModem extends AbstractPocketUpgrade {
     public void update(IPocketAccess access, @Nullable IPeripheral peripheral) {
         if (!(peripheral instanceof PocketModemPeripheral modem)) return;
 
-        modem.setLocation(access);
-
         var state = modem.getModemState();
         if (state.pollChanged()) access.setLight(state.isOpen() ? 0xBA0000 : -1);
     }

projects/common/src/main/java/dan200/computercraft/shared/pocket/peripherals/PocketModemPeripheral.java

@@ -14,31 +14,21 @@ import net.minecraft.world.phys.Vec3;
 import javax.annotation.Nullable;
 
 public class PocketModemPeripheral extends WirelessModemPeripheral {
-    private @Nullable Level level = null;
-    private Vec3 position = Vec3.ZERO;
+    private final IPocketAccess access;
 
     public PocketModemPeripheral(boolean advanced, IPocketAccess access) {
         super(new ModemState(), advanced);
-        setLocation(access);
-    }
-
-    void setLocation(IPocketAccess access) {
-        var entity = access.getEntity();
-        if (entity != null) {
-            level = entity.level();
-            position = entity.getEyePosition(1);
-        }
+        this.access = access;
     }
 
     @Override
     public Level getLevel() {
-        if (level == null) throw new IllegalStateException("Using modem before position has been defined");
-        return level;
+        return access.getLevel();
     }
 
     @Override
     public Vec3 getPosition() {
-        return position;
+        return access.getPosition();
     }
 
     @Override

projects/common/src/main/java/dan200/computercraft/shared/pocket/peripherals/PocketSpeakerPeripheral.java

@@ -8,15 +8,11 @@ import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.pocket.IPocketAccess;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerPosition;
 import dan200.computercraft.shared.peripheral.speaker.UpgradeSpeakerPeripheral;
-import net.minecraft.world.level.Level;
-import net.minecraft.world.phys.Vec3;
 
 import javax.annotation.Nullable;
 
 public class PocketSpeakerPeripheral extends UpgradeSpeakerPeripheral {
     private final IPocketAccess access;
-    private @Nullable Level level;
-    private Vec3 position = Vec3.ZERO;
 
     public PocketSpeakerPeripheral(IPocketAccess access) {
         this.access = access;
@@ -25,7 +21,7 @@ public class PocketSpeakerPeripheral extends UpgradeSpeakerPeripheral {
     @Override
     public SpeakerPosition getPosition() {
         var entity = access.getEntity();
-        return entity == null ? SpeakerPosition.of(level, position) : SpeakerPosition.of(entity);
+        return entity == null ? SpeakerPosition.of(access.getLevel(), access.getPosition()) : SpeakerPosition.of(entity);
     }
 
     @Override
@@ -35,12 +31,6 @@ public class PocketSpeakerPeripheral extends UpgradeSpeakerPeripheral {
 
     @Override
     public void update() {
-        var entity = access.getEntity();
-        if (entity != null) {
-            level = entity.level();
-            position = entity.position();
-        }
-
         super.update();
 
         access.setLight(madeSound() ? 0x3320fc : -1);

projects/common/src/main/java/dan200/computercraft/shared/recipe/CustomShapedRecipe.java

@@ -15,17 +15,17 @@ import java.util.function.Function;
  * A custom version of {@link ShapedRecipe}, which can be converted to and from a {@link ShapedRecipeSpec}.
  */
 public abstract class CustomShapedRecipe extends ShapedRecipe {
-    private final ShapedRecipePattern pattern;
+    private final ShapedRecipePattern shapedPattern;
     private final ItemStack result;
 
     public CustomShapedRecipe(ShapedRecipeSpec recipe) {
         super(recipe.properties().group(), recipe.properties().category(), recipe.pattern(), recipe.result(), recipe.properties().showNotification());
-        this.pattern = recipe.pattern();
+        this.shapedPattern = recipe.pattern();
         this.result = recipe.result();
     }
 
     public final ShapedRecipeSpec toSpec() {
-        return new ShapedRecipeSpec(RecipeProperties.of(this), pattern, result);
+        return new ShapedRecipeSpec(RecipeProperties.of(this), shapedPattern, result);
     }
 
     @Override

projects/common/src/main/java/dan200/computercraft/shared/turtle/TurtleOverlay.java

@@ -0,0 +1,78 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.turtle;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.shared.ModRegistry;
+import dan200.computercraft.shared.util.Holiday;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.resources.RegistryFileCodec;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+
+import javax.annotation.Nullable;
+
+/**
+ * A cosmetic overlay on a turtle.
+ *
+ * @param model          The path to the overlay's model.
+ * @param showElfOverlay Whether this overlay is compatible with the {@linkplain #ELF_MODEL Christmas elf model}.
+ * @see ModRegistry.DataComponents#OVERLAY
+ */
+public record TurtleOverlay(ResourceLocation model, boolean showElfOverlay) {
+    /**
+     * The registry turtle overlays are stored in.
+     */
+    public static final ResourceKey<Registry<TurtleOverlay>> REGISTRY = ResourceKey.createRegistryKey(ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "turtle_overlay"));
+
+    /**
+     * The codec used to read/write turtle overlay definitions from datapacks.
+     */
+    public static final Codec<TurtleOverlay> DIRECT_CODEC = RecordCodecBuilder.create(instance -> instance.group(
+        ResourceLocation.CODEC.fieldOf("model").forGetter(TurtleOverlay::model),
+        Codec.BOOL.optionalFieldOf("show_elf_overlay", false).forGetter(TurtleOverlay::showElfOverlay)
+    ).apply(instance, TurtleOverlay::new));
+
+    /**
+     * The codec used for {@link TurtleOverlay} instances.
+     *
+     * @see ModRegistry.DataComponents#OVERLAY
+     */
+    public static final Codec<Holder<TurtleOverlay>> CODEC = RegistryFileCodec.create(REGISTRY, DIRECT_CODEC);
+
+    /**
+     * The stream codec used for {@link TurtleOverlay} instances.
+     */
+    public static final StreamCodec<RegistryFriendlyByteBuf, Holder<TurtleOverlay>> STREAM_CODEC = ByteBufCodecs.holder(REGISTRY, StreamCodec.composite(
+        ResourceLocation.STREAM_CODEC, TurtleOverlay::model,
+        ByteBufCodecs.BOOL, TurtleOverlay::showElfOverlay,
+        TurtleOverlay::new
+    ));
+
+    /**
+     * An additional overlay that is rendered on all turtles at {@linkplain Holiday#CHRISTMAS Christmas}.
+     *
+     * @see #showElfOverlay()
+     * @see #showElfOverlay(TurtleOverlay, boolean)
+     */
+    public static final ResourceLocation ELF_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_elf_overlay");
+
+    /**
+     * Determine whether we should show the {@linkplain #ELF_MODEL elf overlay}.
+     *
+     * @param overlay   The current {@link TurtleOverlay}.
+     * @param christmas Whether it is Christmas.
+     * @return Whether we should show the elf overlay.
+     */
+    public static boolean showElfOverlay(@Nullable TurtleOverlay overlay, boolean christmas) {
+        return christmas && (overlay == null || overlay.showElfOverlay());
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/turtle/apis/TurtleAPI.java

@@ -11,7 +11,6 @@ import dan200.computercraft.api.turtle.TurtleCommandResult;
 import dan200.computercraft.api.turtle.TurtleSide;
 import dan200.computercraft.core.metrics.Metrics;
 import dan200.computercraft.core.metrics.MetricsObserver;
-import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.peripheral.generic.methods.AbstractInventoryMethods;
 import dan200.computercraft.shared.turtle.core.*;
 
@@ -68,8 +67,8 @@ public class TurtleAPI implements ILuaAPI {
     private final MetricsObserver metrics;
     private final TurtleAccessInternal turtle;
 
-    public TurtleAPI(ServerComputer computer, TurtleAccessInternal turtle) {
-        this.metrics = computer.getMetrics();
+    public TurtleAPI(MetricsObserver metrics, TurtleAccessInternal turtle) {
+        this.metrics = metrics;
         this.turtle = turtle;
     }
 

projects/common/src/main/java/dan200/computercraft/shared/turtle/blocks/TurtleBlockEntity.java

@@ -5,6 +5,7 @@
 package dan200.computercraft.shared.turtle.blocks;
 
 import com.mojang.authlib.GameProfile;
+import dan200.computercraft.api.component.ComputerComponents;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.turtle.ITurtleAccess;
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
@@ -20,9 +21,10 @@ import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.config.Config;
 import dan200.computercraft.shared.container.BasicContainer;
 import dan200.computercraft.shared.platform.PlatformHelper;
-import dan200.computercraft.shared.turtle.apis.TurtleAPI;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.core.TurtleBrain;
 import dan200.computercraft.shared.turtle.inventory.TurtleMenu;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.core.HolderLookup;
@@ -30,7 +32,6 @@ import net.minecraft.core.NonNullList;
 import net.minecraft.core.component.DataComponentMap;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.nbt.CompoundTag;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.Container;
 import net.minecraft.world.ContainerHelper;
@@ -81,10 +82,9 @@ public class TurtleBlockEntity extends AbstractComputerBlockEntity implements Ba
     protected ServerComputer createComputer(int id) {
         var computer = new ServerComputer(
             (ServerLevel) getLevel(), getBlockPos(), id, label,
-            getFamily(), Config.turtleTermWidth,
-            Config.turtleTermHeight
+            getFamily(), Config.turtleTermWidth, Config.turtleTermHeight,
+            ComponentMap.builder().add(ComputerComponents.TURTLE, brain).build()
         );
-        computer.addAPI(new TurtleAPI(computer, brain));
         brain.setupComputer(computer);
         return computer;
     }
@@ -222,8 +222,9 @@ public class TurtleBlockEntity extends AbstractComputerBlockEntity implements Ba
         return brain.getColour();
     }
 
-    public @Nullable ResourceLocation getOverlay() {
-        return brain.getOverlay();
+    public @Nullable TurtleOverlay getOverlay() {
+        var overlay = brain.getOverlay();
+        return overlay == null ? null : overlay.value();
     }
 
     public ITurtleAccess getAccess() {

projects/common/src/main/java/dan200/computercraft/shared/turtle/core/TurtleBrain.java

@@ -20,6 +20,7 @@ import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.config.Config;
 import dan200.computercraft.shared.container.InventoryDelegate;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlockEntity;
 import dan200.computercraft.shared.util.BlockEntityHelpers;
 import dan200.computercraft.shared.util.Holiday;
@@ -32,7 +33,6 @@ import net.minecraft.core.component.DataComponentPatch;
 import net.minecraft.core.particles.ParticleTypes;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.Tag;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.tags.FluidTags;
 import net.minecraft.world.Container;
@@ -74,7 +74,7 @@ public class TurtleBrain implements TurtleAccessInternal {
     private int selectedSlot = 0;
     private int fuelLevel = 0;
     private int colourHex = -1;
-    private @Nullable ResourceLocation overlay = null;
+    private @Nullable Holder<TurtleOverlay> overlay = null;
 
     private TurtleAnimation animation = TurtleAnimation.NONE;
     private int animationProgress = 0;
@@ -134,7 +134,7 @@ public class TurtleBrain implements TurtleAccessInternal {
         // Read fields
         colourHex = nbt.contains(NBT_COLOUR) ? nbt.getInt(NBT_COLOUR) : -1;
         fuelLevel = nbt.contains(NBT_FUEL) ? nbt.getInt(NBT_FUEL) : 0;
-        overlay = nbt.contains(NBT_OVERLAY) ? ResourceLocation.parse(nbt.getString(NBT_OVERLAY)) : null;
+        overlay = nbt.contains(NBT_OVERLAY) ? NBTUtil.decodeFrom(TurtleOverlay.CODEC, registries, nbt, NBT_OVERLAY) : null;
 
         // Read upgrades
         setUpgradeDirect(TurtleSide.LEFT, NBTUtil.decodeFrom(TurtleUpgrades.instance().upgradeDataCodec(), registries, nbt, NBT_LEFT_UPGRADE));
@@ -144,7 +144,7 @@ public class TurtleBrain implements TurtleAccessInternal {
     private void writeCommon(CompoundTag nbt, HolderLookup.Provider registries) {
         nbt.putInt(NBT_FUEL, fuelLevel);
         if (colourHex != -1) nbt.putInt(NBT_COLOUR, colourHex);
-        if (overlay != null) nbt.putString(NBT_OVERLAY, overlay.toString());
+        if (overlay != null) NBTUtil.encodeTo(TurtleOverlay.CODEC, registries, nbt, NBT_OVERLAY, overlay);
 
         // Write upgrades
         NBTUtil.encodeTo(TurtleUpgrades.instance().upgradeDataCodec(), registries, nbt, NBT_LEFT_UPGRADE, getUpgradeWithData(TurtleSide.LEFT));
@@ -418,11 +418,11 @@ public class TurtleBrain implements TurtleAccessInternal {
         BlockEntityHelpers.updateBlock(owner);
     }
 
-    public @Nullable ResourceLocation getOverlay() {
+    public @Nullable Holder<TurtleOverlay> getOverlay() {
         return overlay;
     }
 
-    public void setOverlay(@Nullable ResourceLocation overlay) {
+    public void setOverlay(@Nullable Holder<TurtleOverlay> overlay) {
         if (!Objects.equals(this.overlay, overlay)) {
             this.overlay = overlay;
             BlockEntityHelpers.updateBlock(owner);

projects/common/src/main/java/dan200/computercraft/shared/turtle/items/TurtleItem.java

@@ -12,11 +12,11 @@ import dan200.computercraft.api.upgrades.UpgradeData;
 import dan200.computercraft.impl.TurtleUpgrades;
 import dan200.computercraft.shared.ModRegistry;
 import dan200.computercraft.shared.computer.items.AbstractComputerItem;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlock;
 import net.minecraft.core.cauldron.CauldronInteraction;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.network.chat.Component;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.ItemInteractionResult;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.level.block.LayeredCauldronBlock;
@@ -74,8 +74,9 @@ public class TurtleItem extends AbstractComputerItem {
         return stack.get(side == TurtleSide.LEFT ? ModRegistry.DataComponents.LEFT_TURTLE_UPGRADE.get() : ModRegistry.DataComponents.RIGHT_TURTLE_UPGRADE.get());
     }
 
-    public static @Nullable ResourceLocation getOverlay(ItemStack stack) {
-        return stack.get(ModRegistry.DataComponents.OVERLAY.get());
+    public static @Nullable TurtleOverlay getOverlay(ItemStack stack) {
+        var overlay = stack.get(ModRegistry.DataComponents.OVERLAY.get());
+        return overlay == null ? null : overlay.value();
     }
 
     public static int getFuelLevel(ItemStack stack) {

projects/common/src/main/java/dan200/computercraft/shared/turtle/upgrades/TurtleInventoryCrafting.java

@@ -80,7 +80,7 @@ public final class TurtleInventoryCrafting {
         var recipe = candidate.recipe();
         var input = candidate.input();
         var xStart = candidate.xStart();
-        var yStart = candidate.xStart();
+        var yStart = candidate.yStart();
 
         var player = TurtlePlayer.get(turtle).player();
 

projects/common/src/main/java/dan200/computercraft/shared/util/ComponentMap.java

@@ -0,0 +1,66 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.util;
+
+import dan200.computercraft.api.component.ComputerComponent;
+import dan200.computercraft.core.metrics.MetricsObserver;
+
+import javax.annotation.Nullable;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * An immutable map of components.
+ */
+public final class ComponentMap {
+    public static final ComputerComponent<MetricsObserver> METRICS = ComputerComponent.create("computercraft", "metrics");
+
+    private static final ComponentMap EMPTY = new ComponentMap(Map.of());
+
+    private final Map<ComputerComponent<?>, Object> components;
+
+    private ComponentMap(Map<ComputerComponent<?>, Object> components) {
+        this.components = components;
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T> @Nullable T get(ComputerComponent<T> component) {
+        return (T) components.get(component);
+    }
+
+    public static ComponentMap empty() {
+        return EMPTY;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static final class Builder {
+        private final Map<ComputerComponent<?>, Object> components = new HashMap<>();
+
+        private Builder() {
+        }
+
+        public <T> Builder add(ComputerComponent<T> component, T value) {
+            addImpl(component, value);
+            return this;
+        }
+
+        public Builder add(ComponentMap components) {
+            for (var component : components.components.entrySet()) addImpl(component.getKey(), component.getValue());
+            return this;
+        }
+
+        private void addImpl(ComputerComponent<?> component, Object value) {
+            if (components.containsKey(component)) throw new IllegalArgumentException(component + " is already set");
+            components.put(component, value);
+        }
+
+        public ComponentMap build() {
+            return new ComponentMap(Map.copyOf(components));
+        }
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/util/ComponentizationFixers.java

@@ -82,7 +82,8 @@ public class ComponentizationFixers {
 
         if (item.is(TURTLES)) {
             item.moveTagToComponent("Fuel", "computercraft:fuel");
-            item.moveTagToComponent("Overlay", "computercraft:overlay");
+
+            item.removeTag("Overlay").result().ifPresent(x -> item.setComponent("computercraft:overlay", fixOverlay(x)));
 
             moveUpgradeToComponent(item, ops, "LeftUpgrade", "LeftUpgradeNbt", "computercraft:left_turtle_upgrade");
             moveUpgradeToComponent(item, ops, "RightUpgrade", "RightUpgradeNbt", "computercraft:right_turtle_upgrade");
@@ -152,6 +153,7 @@ public class ComponentizationFixers {
         return typed -> typed.updateTyped(input, output, typed2 -> typed2.update(DSL.remainderFinder(), x -> {
             x = moveUpgradeData(x, "LeftUpgrade", "LeftUpgradeNbt");
             x = moveUpgradeData(x, "RightUpgrade", "RightUpgradeNbt");
+            x = x.update("Overlay", ComponentizationFixers::fixOverlay);
             return x;
         }));
     }
@@ -164,6 +166,20 @@ public class ComponentizationFixers {
         return ops.set(key, createUpgradeData(ops, upgradeId, ops.get(dataKey))).remove(dataKey);
     }
 
+    private static Dynamic<?> fixOverlay(Dynamic<?> overlay) {
+        // Rewrite known overlays to their new ids.
+        var overlayId = overlay.asString(null);
+        if (overlayId == null) return overlay;
+
+        return switch (overlayId) {
+            // Map known overlays to their new id.
+            case "computercraft:block/turtle_trans_overlay" -> overlay.createString("computercraft:trans_flag");
+            case "computercraft:block/turtle_rainbow_overlay" -> overlay.createString("computercraft:rainbow_flag");
+            // And unknown overlays to a direct entry.
+            default -> overlay.emptyMap().set("model", overlay);
+        };
+    }
+
     /**
      * Create a new upgrade data.
      *

projects/common/src/main/java/dan200/computercraft/shared/util/InventoryUtil.java

@@ -8,6 +8,9 @@ import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.Container;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.phys.EntityHitResult;
 import net.minecraft.world.phys.Vec3;
@@ -18,6 +21,20 @@ public final class InventoryUtil {
     private InventoryUtil() {
     }
 
+    /**
+     * Get the inventory slot for a given hand.
+     *
+     * @param player The player to get the slot from.
+     * @param hand   The hand to get.
+     * @return The current slot.
+     */
+    public static int getHandSlot(Player player, InteractionHand hand) {
+        return switch (hand) {
+            case MAIN_HAND -> player.getInventory().selected;
+            case OFF_HAND -> Inventory.SLOT_OFFHAND;
+        };
+    }
+
     public static @Nullable Container getEntityContainer(ServerLevel level, BlockPos pos, Direction side) {
         var vecStart = new Vec3(
             pos.getX() + 0.5 + 0.6 * side.getStepX(),

projects/common/src/main/resources/assets/computercraft/models/block/turtle_rainbow_overlay.json

@@ -1,38 +1,37 @@
 {
-	"parent": "block/block",
-	"textures": {
-		"particle": "computercraft:block/turtle_rainbow_overlay",
-		"texture": "computercraft:block/turtle_rainbow_overlay"
-	},
-	"elements": [
-		{
-			"name": "Flag",
-			"from": [1.5, 13, 10.5],
-			"to": [2, 16.5, 15.5],
-			"rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
-			"faces": {
-				"north": {"uv": [0, 0, 1, 6], "texture": "#texture"},
-				"east": {"uv": [0, 0, 7, 6], "texture": "#texture"},
-				"south": {"uv": [0, 0, 1, 6], "texture": "#texture"},
-				"west": {"uv": [0, 0, 7, 6], "texture": "#texture"},
-				"up": {"uv": [15, 0, 16, 6], "texture": "#texture"},
-				"down": {"uv": [8, 0, 9, 6], "texture": "#texture"}
-			}
-		},
-		{
-			"name": "Stick",
-			"from": [1.5, 10.5, 10.5],
-			"to": [2, 13, 11],
-			"rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
-			"faces": {
-				"north": {"uv": [12, 0, 13, 6], "texture": "#texture"},
-				"east": {"uv": [13, 0, 14, 6], "texture": "#texture"},
-				"south": {"uv": [12, 0, 13, 6], "texture": "#texture"},
-				"west": {"uv": [13, 0, 14, 6], "texture": "#texture"},
-				"up": {"uv": [12, 6, 13, 7], "texture": "#texture"},
-				"down": {"uv": [13, 6, 14, 7], "texture": "#texture"}
-			}
-		}
-	],
-	"display": {}
+    "parent": "block/block",
+    "textures": {
+        "particle": "computercraft:block/turtle_rainbow_overlay",
+        "texture": "computercraft:block/turtle_rainbow_overlay"
+    },
+    "elements": [
+        {
+            "name": "Flag",
+            "from": [1.5, 13.5, 10.5],
+            "to": [2, 16.5, 15.5],
+            "rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
+            "faces": {
+                "north": {"uv": [0, 0, 1, 6], "texture": "#texture"},
+                "east": {"uv": [0, 0, 7, 6], "texture": "#texture"},
+                "south": {"uv": [0, 0, 1, 6], "texture": "#texture"},
+                "west": {"uv": [0, 0, 7, 6], "texture": "#texture"},
+                "up": {"uv": [15, 0, 16, 6], "texture": "#texture"},
+                "down": {"uv": [8, 0, 9, 6], "texture": "#texture"}
+            }
+        },
+        {
+            "name": "Stick",
+            "from": [1.5, 10.5, 10.5],
+            "to": [2, 13.5, 11],
+            "rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
+            "faces": {
+                "north": {"uv": [12, 0, 13, 6], "texture": "#texture"},
+                "east": {"uv": [13, 0, 14, 6], "texture": "#texture"},
+                "south": {"uv": [12, 0, 13, 6], "texture": "#texture"},
+                "west": {"uv": [13, 0, 14, 6], "texture": "#texture"},
+                "up": {"uv": [12, 6, 13, 7], "texture": "#texture"},
+                "down": {"uv": [13, 6, 14, 7], "texture": "#texture"}
+            }
+        }
+    ]
 }

projects/common/src/main/resources/assets/computercraft/models/block/turtle_trans_overlay.json

@@ -1,38 +1,37 @@
 {
-	"parent": "block/block",
-	"textures": {
-		"particle": "computercraft:block/turtle_trans_overlay",
-		"texture": "computercraft:block/turtle_trans_overlay"
-	},
-	"elements": [
-		{
-			"name": "Flag",
-			"from": [1.5, 13.5, 10.5],
-			"to": [2, 16.5, 15.5],
-			"rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
-			"faces": {
-				"north": {"uv": [0, 0, 1, 5], "texture": "#texture"},
-				"east": {"uv": [0, 0, 7, 5], "texture": "#texture"},
-				"south": {"uv": [0, 0, 1, 5], "texture": "#texture"},
-				"west": {"uv": [0, 0, 7, 5], "texture": "#texture"},
-				"up": {"uv": [15, 0, 16, 5], "texture": "#texture"},
-				"down": {"uv": [15, 0, 16, 5], "texture": "#texture"}
-			}
-		},
-		{
-			"name": "Stick",
-			"from": [1.5, 10.5, 10.5],
-			"to": [2, 13.5, 11],
-			"rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
-			"faces": {
-				"north": {"uv": [12, 0, 13, 6], "texture": "#texture"},
-				"east": {"uv": [13, 0, 14, 6], "texture": "#texture"},
-				"south": {"uv": [12, 0, 13, 6], "texture": "#texture"},
-				"west": {"uv": [13, 0, 14, 6], "texture": "#texture"},
-				"up": {"uv": [12, 6, 13, 7], "texture": "#texture"},
-				"down": {"uv": [13, 6, 14, 7], "texture": "#texture"}
-			}
-		}
-	],
-	"display": {}
+    "parent": "block/block",
+    "textures": {
+        "particle": "computercraft:block/turtle_trans_overlay",
+        "texture": "computercraft:block/turtle_trans_overlay"
+    },
+    "elements": [
+        {
+            "name": "Flag",
+            "from": [1.5, 13.5, 10.5],
+            "to": [2, 16, 15.5],
+            "rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
+            "faces": {
+                "north": {"uv": [0, 0, 1, 5], "texture": "#texture"},
+                "east": {"uv": [0, 0, 7, 5], "texture": "#texture"},
+                "south": {"uv": [0, 0, 1, 5], "texture": "#texture"},
+                "west": {"uv": [0, 0, 7, 5], "texture": "#texture"},
+                "up": {"uv": [15, 0, 16, 5], "texture": "#texture"},
+                "down": {"uv": [15, 0, 16, 5], "texture": "#texture"}
+            }
+        },
+        {
+            "name": "Stick",
+            "from": [1.5, 10.5, 10.5],
+            "to": [2, 13.5, 11],
+            "rotation": {"angle": 22.5, "axis": "x", "origin": [2, 11, 10.75]},
+            "faces": {
+                "north": {"uv": [12, 0, 13, 6], "texture": "#texture"},
+                "east": {"uv": [13, 0, 14, 6], "texture": "#texture"},
+                "south": {"uv": [12, 0, 13, 6], "texture": "#texture"},
+                "west": {"uv": [13, 0, 14, 6], "texture": "#texture"},
+                "up": {"uv": [12, 6, 13, 7], "texture": "#texture"},
+                "down": {"uv": [13, 6, 14, 7], "texture": "#texture"}
+            }
+        }
+    ]
 }

projects/common/src/testMod/kotlin/dan200/computercraft/gametest/Turtle_Test.kt

@@ -4,6 +4,7 @@
 
 package dan200.computercraft.gametest
 
+import dan200.computercraft.api.ComputerCraftAPI
 import dan200.computercraft.api.detail.BasicItemDetailProvider
 import dan200.computercraft.api.detail.VanillaDetailRegistries
 import dan200.computercraft.api.lua.ObjectArguments
@@ -21,11 +22,14 @@ import dan200.computercraft.shared.peripheral.modem.wired.CableBlock
 import dan200.computercraft.shared.peripheral.modem.wired.CableModemVariant
 import dan200.computercraft.shared.peripheral.monitor.MonitorBlock
 import dan200.computercraft.shared.peripheral.monitor.MonitorEdgeState
+import dan200.computercraft.shared.turtle.TurtleOverlay
 import dan200.computercraft.shared.turtle.apis.TurtleAPI
+import dan200.computercraft.shared.turtle.items.TurtleItem
 import dan200.computercraft.shared.util.WaterloggableHelpers
 import dan200.computercraft.test.core.assertArrayEquals
 import dan200.computercraft.test.core.computer.LuaTaskContext
 import dan200.computercraft.test.core.computer.getApi
+import dan200.computercraft.test.shared.ItemStackMatcher.isStack
 import net.minecraft.core.BlockPos
 import net.minecraft.core.registries.Registries
 import net.minecraft.gametest.framework.GameTest
@@ -41,8 +45,7 @@ import net.minecraft.world.level.block.FenceBlock
 import net.minecraft.world.level.block.entity.BlockEntityType
 import net.minecraft.world.level.block.state.properties.BlockStateProperties
 import org.hamcrest.MatcherAssert.assertThat
-import org.hamcrest.Matchers.array
-import org.hamcrest.Matchers.instanceOf
+import org.hamcrest.Matchers.*
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertNotEquals
 import java.util.*
@@ -654,6 +657,27 @@ class Turtle_Test {
         }
     }
 
+    /**
+     * Loads a structure created on an older version of the game, and checks that data fixers have been applied.
+     */
+    @GameTest
+    fun Data_fixers(helper: GameTestHelper) = helper.sequence {
+        thenExecute {
+            val overlay = helper.level.registryAccess().registryOrThrow(TurtleOverlay.REGISTRY)
+                .get(ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "trans_flag"))!!
+            val upgrade = helper.level.registryAccess().registryOrThrow(ITurtleUpgrade.REGISTRY)
+                .get(ResourceLocation.withDefaultNamespace("diamond_pickaxe"))!!
+
+            val turtleBe = helper.getBlockEntity(BlockPos(1, 2, 1), ModRegistry.BlockEntities.TURTLE_NORMAL.get())
+            assertEquals(overlay, turtleBe.overlay)
+            assertEquals(upgrade, turtleBe.getUpgrade(TurtleSide.LEFT))
+
+            val turtleItem = turtleBe.getItem(0)
+            assertEquals(overlay, TurtleItem.getOverlay(turtleItem))
+            assertEquals(upgrade, TurtleItem.getUpgrade(turtleItem, TurtleSide.LEFT))
+        }
+    }
+
     /**
      * `turtle.suck` only pulls for the current side.
      */
@@ -669,6 +693,47 @@ class Turtle_Test {
         }
     }
 
+    /**
+     * `turtle.craft` works as expected
+     */
+    @GameTest
+    fun Craft(helper: GameTestHelper) = helper.sequence {
+        thenOnComputer {
+            callPeripheral("left", "craft", 1).assertArrayEquals(true)
+        }
+        thenExecute {
+            val turtle = helper.getBlockEntity(BlockPos(2, 2, 2), ModRegistry.BlockEntities.TURTLE_NORMAL.get())
+            assertThat(
+                "Inventory is as expected.",
+                turtle.items,
+                contains(
+                    isStack(Items.DIAMOND, 1), isStack(Items.DIAMOND, 1), isStack(Items.DIAMOND, 1), isStack(Items.DIAMOND_PICKAXE, 1),
+                    isStack(ItemStack.EMPTY), isStack(Items.STICK, 1), isStack(ItemStack.EMPTY), isStack(ItemStack.EMPTY),
+                    isStack(ItemStack.EMPTY), isStack(Items.STICK, 1), isStack(ItemStack.EMPTY), isStack(ItemStack.EMPTY),
+                    isStack(ItemStack.EMPTY), isStack(ItemStack.EMPTY), isStack(ItemStack.EMPTY), isStack(ItemStack.EMPTY),
+                ),
+            )
+        }
+    }
+
+    /**
+     * `turtle.equipLeft` equips a tool.
+     */
+    @GameTest
+    fun Equip_tool(helper: GameTestHelper) = helper.sequence {
+        thenOnComputer {
+            turtle.equipLeft().await().assertArrayEquals(true)
+        }
+        thenExecute {
+            val turtle = helper.getBlockEntity(BlockPos(2, 2, 2), ModRegistry.BlockEntities.TURTLE_NORMAL.get())
+            assertEquals(
+                helper.level.registryAccess().registryOrThrow(ITurtleUpgrade.REGISTRY)
+                    .get(ResourceLocation.withDefaultNamespace("diamond_pickaxe")),
+                turtle.getUpgrade(TurtleSide.LEFT),
+            )
+        }
+    }
+
     /**
      * Render turtles as an item.
      */

projects/common/src/testMod/kotlin/dan200/computercraft/gametest/api/TestExtensions.kt

@@ -179,7 +179,6 @@ fun <T : Comparable<T>> GameTestHelper.assertBlockHas(pos: BlockPos, property: P
 fun GameTestHelper.getContainerAt(pos: BlockPos): Container =
     when (val container: BlockEntity = getBlockEntity(pos)) {
         is Container -> container
-        null -> failVerbose("Expected a container at $pos, found nothing", pos)
         else -> failVerbose("Expected a container at $pos, found ${getName(container.type)}", pos)
     }
 

projects/common/src/testMod/resources/data/cctest/structures/turtle_test.craft.snbt

@@ -0,0 +1,137 @@
+{
+    DataVersion: 3465,
+    size: [5, 5, 5],
+    data: [
+        {pos: [0, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [0, 1, 0], state: "minecraft:air"},
+        {pos: [0, 1, 1], state: "minecraft:air"},
+        {pos: [0, 1, 2], state: "minecraft:air"},
+        {pos: [0, 1, 3], state: "minecraft:air"},
+        {pos: [0, 1, 4], state: "minecraft:air"},
+        {pos: [1, 1, 0], state: "minecraft:air"},
+        {pos: [1, 1, 1], state: "minecraft:air"},
+        {pos: [1, 1, 2], state: "minecraft:air"},
+        {pos: [1, 1, 3], state: "minecraft:air"},
+        {pos: [1, 1, 4], state: "minecraft:air"},
+        {pos: [2, 1, 0], state: "minecraft:air"},
+        {pos: [2, 1, 1], state: "minecraft:air"},
+        {pos: [2, 1, 2], state: "computercraft:turtle_normal{facing:north,waterlogged:false}", nbt: {ComputerId: 1, Fuel: 0, Items: [{Count: 2b, Slot: 0b, id: "minecraft:diamond"}, {Count: 2b, Slot: 1b, id: "minecraft:diamond"}, {Count: 2b, Slot: 2b, id: "minecraft:diamond"}, {Count: 2b, Slot: 5b, id: "minecraft:stick"}, {Count: 2b, Slot: 9b, id: "minecraft:stick"}], Label: "turtle_test.craft", LeftUpgrade: "minecraft:crafting_table", LeftUpgradeNbt: {}, On: 1b, Slot: 0, id: "computercraft:turtle_normal"}},
+        {pos: [2, 1, 3], state: "minecraft:air"},
+        {pos: [2, 1, 4], state: "minecraft:air"},
+        {pos: [3, 1, 0], state: "minecraft:air"},
+        {pos: [3, 1, 1], state: "minecraft:air"},
+        {pos: [3, 1, 2], state: "minecraft:air"},
+        {pos: [3, 1, 3], state: "minecraft:air"},
+        {pos: [3, 1, 4], state: "minecraft:air"},
+        {pos: [4, 1, 0], state: "minecraft:air"},
+        {pos: [4, 1, 1], state: "minecraft:air"},
+        {pos: [4, 1, 2], state: "minecraft:air"},
+        {pos: [4, 1, 3], state: "minecraft:air"},
+        {pos: [4, 1, 4], state: "minecraft:air"},
+        {pos: [0, 2, 0], state: "minecraft:air"},
+        {pos: [0, 2, 1], state: "minecraft:air"},
+        {pos: [0, 2, 2], state: "minecraft:air"},
+        {pos: [0, 2, 3], state: "minecraft:air"},
+        {pos: [0, 2, 4], state: "minecraft:air"},
+        {pos: [1, 2, 0], state: "minecraft:air"},
+        {pos: [1, 2, 1], state: "minecraft:air"},
+        {pos: [1, 2, 2], state: "minecraft:air"},
+        {pos: [1, 2, 3], state: "minecraft:air"},
+        {pos: [1, 2, 4], state: "minecraft:air"},
+        {pos: [2, 2, 0], state: "minecraft:air"},
+        {pos: [2, 2, 1], state: "minecraft:air"},
+        {pos: [2, 2, 2], state: "minecraft:air"},
+        {pos: [2, 2, 3], state: "minecraft:air"},
+        {pos: [2, 2, 4], state: "minecraft:air"},
+        {pos: [3, 2, 0], state: "minecraft:air"},
+        {pos: [3, 2, 1], state: "minecraft:air"},
+        {pos: [3, 2, 2], state: "minecraft:air"},
+        {pos: [3, 2, 3], state: "minecraft:air"},
+        {pos: [3, 2, 4], state: "minecraft:air"},
+        {pos: [4, 2, 0], state: "minecraft:air"},
+        {pos: [4, 2, 1], state: "minecraft:air"},
+        {pos: [4, 2, 2], state: "minecraft:air"},
+        {pos: [4, 2, 3], state: "minecraft:air"},
+        {pos: [4, 2, 4], state: "minecraft:air"},
+        {pos: [0, 3, 0], state: "minecraft:air"},
+        {pos: [0, 3, 1], state: "minecraft:air"},
+        {pos: [0, 3, 2], state: "minecraft:air"},
+        {pos: [0, 3, 3], state: "minecraft:air"},
+        {pos: [0, 3, 4], state: "minecraft:air"},
+        {pos: [1, 3, 0], state: "minecraft:air"},
+        {pos: [1, 3, 1], state: "minecraft:air"},
+        {pos: [1, 3, 2], state: "minecraft:air"},
+        {pos: [1, 3, 3], state: "minecraft:air"},
+        {pos: [1, 3, 4], state: "minecraft:air"},
+        {pos: [2, 3, 0], state: "minecraft:air"},
+        {pos: [2, 3, 1], state: "minecraft:air"},
+        {pos: [2, 3, 2], state: "minecraft:air"},
+        {pos: [2, 3, 3], state: "minecraft:air"},
+        {pos: [2, 3, 4], state: "minecraft:air"},
+        {pos: [3, 3, 0], state: "minecraft:air"},
+        {pos: [3, 3, 1], state: "minecraft:air"},
+        {pos: [3, 3, 2], state: "minecraft:air"},
+        {pos: [3, 3, 3], state: "minecraft:air"},
+        {pos: [3, 3, 4], state: "minecraft:air"},
+        {pos: [4, 3, 0], state: "minecraft:air"},
+        {pos: [4, 3, 1], state: "minecraft:air"},
+        {pos: [4, 3, 2], state: "minecraft:air"},
+        {pos: [4, 3, 3], state: "minecraft:air"},
+        {pos: [4, 3, 4], state: "minecraft:air"},
+        {pos: [0, 4, 0], state: "minecraft:air"},
+        {pos: [0, 4, 1], state: "minecraft:air"},
+        {pos: [0, 4, 2], state: "minecraft:air"},
+        {pos: [0, 4, 3], state: "minecraft:air"},
+        {pos: [0, 4, 4], state: "minecraft:air"},
+        {pos: [1, 4, 0], state: "minecraft:air"},
+        {pos: [1, 4, 1], state: "minecraft:air"},
+        {pos: [1, 4, 2], state: "minecraft:air"},
+        {pos: [1, 4, 3], state: "minecraft:air"},
+        {pos: [1, 4, 4], state: "minecraft:air"},
+        {pos: [2, 4, 0], state: "minecraft:air"},
+        {pos: [2, 4, 1], state: "minecraft:air"},
+        {pos: [2, 4, 2], state: "minecraft:air"},
+        {pos: [2, 4, 3], state: "minecraft:air"},
+        {pos: [2, 4, 4], state: "minecraft:air"},
+        {pos: [3, 4, 0], state: "minecraft:air"},
+        {pos: [3, 4, 1], state: "minecraft:air"},
+        {pos: [3, 4, 2], state: "minecraft:air"},
+        {pos: [3, 4, 3], state: "minecraft:air"},
+        {pos: [3, 4, 4], state: "minecraft:air"},
+        {pos: [4, 4, 0], state: "minecraft:air"},
+        {pos: [4, 4, 1], state: "minecraft:air"},
+        {pos: [4, 4, 2], state: "minecraft:air"},
+        {pos: [4, 4, 3], state: "minecraft:air"},
+        {pos: [4, 4, 4], state: "minecraft:air"}
+    ],
+    entities: [],
+    palette: [
+        "minecraft:polished_andesite",
+        "minecraft:air",
+        "computercraft:turtle_normal{facing:north,waterlogged:false}"
+    ]
+}

projects/common/src/testMod/resources/data/cctest/structures/turtle_test.data_fixers.snbt

@@ -0,0 +1,39 @@
+{
+    DataVersion: 3465,
+    size: [3, 3, 3],
+    data: [
+        {pos: [0, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [0, 1, 0], state: "minecraft:air"},
+        {pos: [0, 1, 1], state: "minecraft:air"},
+        {pos: [0, 1, 2], state: "minecraft:air"},
+        {pos: [1, 1, 0], state: "minecraft:air"},
+        {pos: [1, 1, 1], state: "computercraft:turtle_normal{facing:south,waterlogged:false}", nbt: {ComputerId: 123, Fuel: 0, Items: [{Count: 1b, Slot: 0b, id: "computercraft:turtle_normal", tag: {ComputerId: 123, LeftUpgrade: "minecraft:diamond_pickaxe", Overlay: "computercraft:block/turtle_trans_overlay"}}], LeftUpgrade: "minecraft:diamond_pickaxe", LeftUpgradeNbt: {}, On: 0b, Overlay: "computercraft:block/turtle_trans_overlay", Owner: {LowerId: -4770154215762454977L, Name: "Player436", UpperId: 114963728012426084L}, Slot: 0, id: "computercraft:turtle_normal"}},
+        {pos: [1, 1, 2], state: "minecraft:air"},
+        {pos: [2, 1, 0], state: "minecraft:air"},
+        {pos: [2, 1, 1], state: "minecraft:air"},
+        {pos: [2, 1, 2], state: "minecraft:air"},
+        {pos: [0, 2, 0], state: "minecraft:air"},
+        {pos: [0, 2, 1], state: "minecraft:air"},
+        {pos: [0, 2, 2], state: "minecraft:air"},
+        {pos: [1, 2, 0], state: "minecraft:air"},
+        {pos: [1, 2, 1], state: "minecraft:air"},
+        {pos: [1, 2, 2], state: "minecraft:air"},
+        {pos: [2, 2, 0], state: "minecraft:air"},
+        {pos: [2, 2, 1], state: "minecraft:air"},
+        {pos: [2, 2, 2], state: "minecraft:air"}
+    ],
+    entities: [],
+    palette: [
+        "minecraft:polished_andesite",
+        "minecraft:air",
+        "computercraft:turtle_normal{facing:south,waterlogged:false}"
+    ]
+}

projects/common/src/testMod/resources/data/cctest/structures/turtle_test.equip_tool.snbt

@@ -0,0 +1,137 @@
+{
+    DataVersion: 3465,
+    size: [5, 5, 5],
+    data: [
+        {pos: [0, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [0, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [1, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [2, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [3, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 0], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 1], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 2], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 3], state: "minecraft:polished_andesite"},
+        {pos: [4, 0, 4], state: "minecraft:polished_andesite"},
+        {pos: [0, 1, 0], state: "minecraft:air"},
+        {pos: [0, 1, 1], state: "minecraft:air"},
+        {pos: [0, 1, 2], state: "minecraft:air"},
+        {pos: [0, 1, 3], state: "minecraft:air"},
+        {pos: [0, 1, 4], state: "minecraft:air"},
+        {pos: [1, 1, 0], state: "minecraft:air"},
+        {pos: [1, 1, 1], state: "minecraft:air"},
+        {pos: [1, 1, 2], state: "minecraft:air"},
+        {pos: [1, 1, 3], state: "minecraft:air"},
+        {pos: [1, 1, 4], state: "minecraft:air"},
+        {pos: [2, 1, 0], state: "minecraft:air"},
+        {pos: [2, 1, 1], state: "minecraft:air"},
+        {pos: [2, 1, 2], state: "computercraft:turtle_normal{facing:north,waterlogged:false}", nbt: {ComputerId: 1, Fuel: 0, Items: [{Count: 1b, Slot: 0b, id: "minecraft:diamond_pickaxe"}], Label: "turtle_test.equip_tool", On: 1b, Slot: 0, id: "computercraft:turtle_normal"}},
+        {pos: [2, 1, 3], state: "minecraft:air"},
+        {pos: [2, 1, 4], state: "minecraft:air"},
+        {pos: [3, 1, 0], state: "minecraft:air"},
+        {pos: [3, 1, 1], state: "minecraft:air"},
+        {pos: [3, 1, 2], state: "minecraft:air"},
+        {pos: [3, 1, 3], state: "minecraft:air"},
+        {pos: [3, 1, 4], state: "minecraft:air"},
+        {pos: [4, 1, 0], state: "minecraft:air"},
+        {pos: [4, 1, 1], state: "minecraft:air"},
+        {pos: [4, 1, 2], state: "minecraft:air"},
+        {pos: [4, 1, 3], state: "minecraft:air"},
+        {pos: [4, 1, 4], state: "minecraft:air"},
+        {pos: [0, 2, 0], state: "minecraft:air"},
+        {pos: [0, 2, 1], state: "minecraft:air"},
+        {pos: [0, 2, 2], state: "minecraft:air"},
+        {pos: [0, 2, 3], state: "minecraft:air"},
+        {pos: [0, 2, 4], state: "minecraft:air"},
+        {pos: [1, 2, 0], state: "minecraft:air"},
+        {pos: [1, 2, 1], state: "minecraft:air"},
+        {pos: [1, 2, 2], state: "minecraft:air"},
+        {pos: [1, 2, 3], state: "minecraft:air"},
+        {pos: [1, 2, 4], state: "minecraft:air"},
+        {pos: [2, 2, 0], state: "minecraft:air"},
+        {pos: [2, 2, 1], state: "minecraft:air"},
+        {pos: [2, 2, 2], state: "minecraft:air"},
+        {pos: [2, 2, 3], state: "minecraft:air"},
+        {pos: [2, 2, 4], state: "minecraft:air"},
+        {pos: [3, 2, 0], state: "minecraft:air"},
+        {pos: [3, 2, 1], state: "minecraft:air"},
+        {pos: [3, 2, 2], state: "minecraft:air"},
+        {pos: [3, 2, 3], state: "minecraft:air"},
+        {pos: [3, 2, 4], state: "minecraft:air"},
+        {pos: [4, 2, 0], state: "minecraft:air"},
+        {pos: [4, 2, 1], state: "minecraft:air"},
+        {pos: [4, 2, 2], state: "minecraft:air"},
+        {pos: [4, 2, 3], state: "minecraft:air"},
+        {pos: [4, 2, 4], state: "minecraft:air"},
+        {pos: [0, 3, 0], state: "minecraft:air"},
+        {pos: [0, 3, 1], state: "minecraft:air"},
+        {pos: [0, 3, 2], state: "minecraft:air"},
+        {pos: [0, 3, 3], state: "minecraft:air"},
+        {pos: [0, 3, 4], state: "minecraft:air"},
+        {pos: [1, 3, 0], state: "minecraft:air"},
+        {pos: [1, 3, 1], state: "minecraft:air"},
+        {pos: [1, 3, 2], state: "minecraft:air"},
+        {pos: [1, 3, 3], state: "minecraft:air"},
+        {pos: [1, 3, 4], state: "minecraft:air"},
+        {pos: [2, 3, 0], state: "minecraft:air"},
+        {pos: [2, 3, 1], state: "minecraft:air"},
+        {pos: [2, 3, 2], state: "minecraft:air"},
+        {pos: [2, 3, 3], state: "minecraft:air"},
+        {pos: [2, 3, 4], state: "minecraft:air"},
+        {pos: [3, 3, 0], state: "minecraft:air"},
+        {pos: [3, 3, 1], state: "minecraft:air"},
+        {pos: [3, 3, 2], state: "minecraft:air"},
+        {pos: [3, 3, 3], state: "minecraft:air"},
+        {pos: [3, 3, 4], state: "minecraft:air"},
+        {pos: [4, 3, 0], state: "minecraft:air"},
+        {pos: [4, 3, 1], state: "minecraft:air"},
+        {pos: [4, 3, 2], state: "minecraft:air"},
+        {pos: [4, 3, 3], state: "minecraft:air"},
+        {pos: [4, 3, 4], state: "minecraft:air"},
+        {pos: [0, 4, 0], state: "minecraft:air"},
+        {pos: [0, 4, 1], state: "minecraft:air"},
+        {pos: [0, 4, 2], state: "minecraft:air"},
+        {pos: [0, 4, 3], state: "minecraft:air"},
+        {pos: [0, 4, 4], state: "minecraft:air"},
+        {pos: [1, 4, 0], state: "minecraft:air"},
+        {pos: [1, 4, 1], state: "minecraft:air"},
+        {pos: [1, 4, 2], state: "minecraft:air"},
+        {pos: [1, 4, 3], state: "minecraft:air"},
+        {pos: [1, 4, 4], state: "minecraft:air"},
+        {pos: [2, 4, 0], state: "minecraft:air"},
+        {pos: [2, 4, 1], state: "minecraft:air"},
+        {pos: [2, 4, 2], state: "minecraft:air"},
+        {pos: [2, 4, 3], state: "minecraft:air"},
+        {pos: [2, 4, 4], state: "minecraft:air"},
+        {pos: [3, 4, 0], state: "minecraft:air"},
+        {pos: [3, 4, 1], state: "minecraft:air"},
+        {pos: [3, 4, 2], state: "minecraft:air"},
+        {pos: [3, 4, 3], state: "minecraft:air"},
+        {pos: [3, 4, 4], state: "minecraft:air"},
+        {pos: [4, 4, 0], state: "minecraft:air"},
+        {pos: [4, 4, 1], state: "minecraft:air"},
+        {pos: [4, 4, 2], state: "minecraft:air"},
+        {pos: [4, 4, 3], state: "minecraft:air"},
+        {pos: [4, 4, 4], state: "minecraft:air"}
+    ],
+    entities: [],
+    palette: [
+        "minecraft:polished_andesite",
+        "minecraft:air",
+        "computercraft:turtle_normal{facing:north,waterlogged:false}"
+    ]
+}

projects/core-api/src/main/java/dan200/computercraft/api/lua/IComputerSystem.java

@@ -1,23 +0,0 @@
-// SPDX-FileCopyrightText: 2017 The CC: Tweaked Developers
-//
-// SPDX-License-Identifier: MPL-2.0
-
-package dan200.computercraft.api.lua;
-
-import dan200.computercraft.api.peripheral.IComputerAccess;
-
-import javax.annotation.Nullable;
-
-/**
- * An interface passed to {@link ILuaAPIFactory} in order to provide additional information
- * about a computer.
- */
-public interface IComputerSystem extends IComputerAccess {
-    /**
-     * Get the label for this computer.
-     *
-     * @return This computer's label, or {@code null} if it is not set.
-     */
-    @Nullable
-    String getLabel();
-}

projects/core/src/main/java/dan200/computercraft/core/ComputerContext.java

@@ -4,7 +4,6 @@
 
 package dan200.computercraft.core;
 
-import dan200.computercraft.api.lua.ILuaAPIFactory;
 import dan200.computercraft.core.asm.GenericMethod;
 import dan200.computercraft.core.asm.LuaMethodSupplier;
 import dan200.computercraft.core.asm.PeripheralMethodSupplier;
@@ -35,21 +34,19 @@ public final class ComputerContext {
     private final ComputerScheduler computerScheduler;
     private final MainThreadScheduler mainThreadScheduler;
     private final ILuaMachine.Factory luaFactory;
-    private final List<ILuaAPIFactory> apiFactories;
     private final MethodSupplier<LuaMethod> luaMethods;
     private final MethodSupplier<PeripheralMethod> peripheralMethods;
 
-    ComputerContext(
+    private ComputerContext(
         GlobalEnvironment globalEnvironment, ComputerScheduler computerScheduler,
         MainThreadScheduler mainThreadScheduler, ILuaMachine.Factory luaFactory,
-        List<ILuaAPIFactory> apiFactories, MethodSupplier<LuaMethod> luaMethods,
+        MethodSupplier<LuaMethod> luaMethods,
         MethodSupplier<PeripheralMethod> peripheralMethods
     ) {
         this.globalEnvironment = globalEnvironment;
         this.computerScheduler = computerScheduler;
         this.mainThreadScheduler = mainThreadScheduler;
         this.luaFactory = luaFactory;
-        this.apiFactories = apiFactories;
         this.luaMethods = luaMethods;
         this.peripheralMethods = peripheralMethods;
     }
@@ -91,15 +88,6 @@ public final class ComputerContext {
         return luaFactory;
     }
 
-    /**
-     * Additional APIs to inject into each computer.
-     *
-     * @return All available API factories.
-     */
-    public List<ILuaAPIFactory> apiFactories() {
-        return apiFactories;
-    }
-
     /**
      * Get the {@link MethodSupplier} used to find methods on Lua values.
      *
@@ -166,7 +154,6 @@ public final class ComputerContext {
         private @Nullable ComputerScheduler computerScheduler = null;
         private @Nullable MainThreadScheduler mainThreadScheduler;
         private @Nullable ILuaMachine.Factory luaFactory;
-        private @Nullable List<ILuaAPIFactory> apiFactories;
         private @Nullable List<GenericMethod> genericMethods;
 
         Builder(GlobalEnvironment environment) {
@@ -227,20 +214,6 @@ public final class ComputerContext {
             return this;
         }
 
-        /**
-         * Set the additional {@linkplain ILuaAPIFactory APIs} to add to each computer.
-         *
-         * @param apis A list of API factories.
-         * @return {@code this}, for chaining
-         * @see ComputerContext#apiFactories()
-         */
-        public Builder apiFactories(Collection<ILuaAPIFactory> apis) {
-            Objects.requireNonNull(apis);
-            if (apiFactories != null) throw new IllegalStateException("Main-thread scheduler already specified");
-            apiFactories = List.copyOf(apis);
-            return this;
-        }
-
         /**
          * Set the set of {@link GenericMethod}s used by the {@linkplain MethodSupplier method suppliers}.
          *
@@ -267,7 +240,6 @@ public final class ComputerContext {
                 computerScheduler == null ? new ComputerThread(1) : computerScheduler,
                 mainThreadScheduler == null ? new NoWorkMainThreadScheduler() : mainThreadScheduler,
                 luaFactory == null ? CobaltLuaMachine::new : luaFactory,
-                apiFactories == null ? List.of() : apiFactories,
                 LuaMethodSupplier.create(genericMethods == null ? List.of() : genericMethods),
                 PeripheralMethodSupplier.create(genericMethods == null ? List.of() : genericMethods)
             );

projects/core/src/main/java/dan200/computercraft/core/apis/ComputerAccess.java

@@ -21,7 +21,7 @@ public abstract class ComputerAccess implements IComputerAccess {
     private static final Logger LOG = LoggerFactory.getLogger(ComputerAccess.class);
 
     private final IAPIEnvironment environment;
-    private final Set<String> mounts = new HashSet<>();
+    private final Set<String> mounts = new HashSet<>(0);
 
     protected ComputerAccess(IAPIEnvironment environment) {
         this.environment = environment;

projects/core/src/main/java/dan200/computercraft/core/apis/OSAPI.java

@@ -175,9 +175,9 @@ public class OSAPI implements ILuaAPI {
     }
 
     /**
-     * Sets an alarm that will fire at the specified in-game time. When it
-     * fires, * an {@code alarm} event will be added to the event queue with the
-     * ID * returned from this function as the first parameter.
+     * Sets an alarm that will fire at the specified {@linkplain #time(IArguments) in-game time}.
+     * When it fires, an {@code alarm} event will be added to the event queue with the
+     * ID returned from this function as the first parameter.
      *
      * @param time The time at which to fire the alarm, in the range [0.0, 24.0).
      * @return The ID of the new alarm. This can be used to filter the

projects/core/src/main/java/dan200/computercraft/core/computer/ApiLifecycle.java

@@ -0,0 +1,28 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.core.computer;
+
+import dan200.computercraft.api.lua.ILuaAPI;
+
+/**
+ * Hooks for managing the lifecycle of an API. This allows adding additional logic to an API's {@link ILuaAPI#startup()}
+ * and {@link ILuaAPI#shutdown()} methods.
+ *
+ * @see ILuaAPI
+ * @see Computer#addApi(ILuaAPI, ApiLifecycle)
+ */
+public interface ApiLifecycle {
+    /**
+     * Called before the API's {@link ILuaAPI#startup()} method, may be used to set up resources.
+     */
+    default void startup() {
+    }
+
+    /**
+     * Called after the API's {@link ILuaAPI#shutdown()} method, may be used to tear down resources.
+     */
+    default void shutdown() {
+    }
+}

projects/core/src/main/java/dan200/computercraft/core/computer/ApiWrapper.java

@@ -9,18 +9,14 @@ import dan200.computercraft.api.lua.ILuaAPI;
 import javax.annotation.Nullable;
 
 /**
- * A wrapper for {@link ILuaAPI}s which optionally manages the lifecycle of a {@link ComputerSystem}.
+ * A wrapper for {@link ILuaAPI}s which provides an optional shutdown hook to clean up resources.
+ *
+ * @param api       The original API.
+ * @param lifecycle The optional lifecycle hooks for this API.
  */
-final class ApiWrapper {
-    private final ILuaAPI api;
-    private final @Nullable ComputerSystem system;
-
-    ApiWrapper(ILuaAPI api, @Nullable ComputerSystem system) {
-        this.api = api;
-        this.system = system;
-    }
-
+record ApiWrapper(ILuaAPI api, @Nullable ApiLifecycle lifecycle) {
     public void startup() {
+        if (lifecycle != null) lifecycle.startup();
         api.startup();
     }
 
@@ -30,7 +26,7 @@ final class ApiWrapper {
 
     public void shutdown() {
         api.shutdown();
-        if (system != null) system.unmountAll();
+        if (lifecycle != null) lifecycle.shutdown();
     }
 
     public ILuaAPI api() {