Computer components (#1915)

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.

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/shared/ModRegistry.java

@@ -6,6 +6,7 @@ package dan200.computercraft.shared;
 
 import com.mojang.brigadier.arguments.ArgumentType;
 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;
@@ -23,6 +24,7 @@ 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;
@@ -73,14 +76,17 @@ import dan200.computercraft.shared.recipe.CustomShapelessRecipe;
 import dan200.computercraft.shared.recipe.ImpostorShapedRecipe;
 import dan200.computercraft.shared.recipe.ImpostorShapelessRecipe;
 import dan200.computercraft.shared.turtle.FurnaceRefuelHandler;
+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.TurtleOverlayRecipe;
 import dan200.computercraft.shared.turtle.recipes.TurtleRecipe;
 import dan200.computercraft.shared.turtle.recipes.TurtleUpgradeRecipe;
 import dan200.computercraft.shared.turtle.upgrades.*;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.commands.CommandSourceStack;
 import net.minecraft.commands.synchronization.ArgumentTypeInfo;
 import net.minecraft.commands.synchronization.SingletonArgumentInfo;
@@ -102,6 +108,7 @@ import net.minecraft.world.level.block.state.BlockState;
 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;
 
@@ -447,6 +454,22 @@ 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
@@ -287,7 +289,7 @@ 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/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/core/ComputerSystem.java

@@ -4,28 +4,41 @@
 
 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.IComputerAccess;
 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 IComputerAccess}/{@link IComputerSystem} for usage by externally registered APIs.
+ * Implementation of {@link IComputerSystem} for usage by externally registered APIs.
  *
  * @see ILuaAPIFactory
  */
-class ComputerSystem extends ComputerAccess implements IComputerSystem, ApiLifecycle {
+final class ComputerSystem extends ComputerAccess implements IComputerSystem, ApiLifecycle {
+    private final ServerComputer computer;
     private final IAPIEnvironment environment;
+    private final ComponentMap components;
 
-    ComputerSystem(IAPIEnvironment environment) {
+    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
@@ -38,6 +51,31 @@ class ComputerSystem extends ComputerAccess implements IComputerSystem, ApiLifec
         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() {
@@ -55,4 +93,9 @@ class ComputerSystem extends ComputerAccess implements IComputerSystem, ApiLifec
     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/ServerComputer.java

@@ -5,8 +5,9 @@
 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;
@@ -14,7 +15,6 @@ import dan200.computercraft.core.computer.ComputerEnvironment;
 import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.core.metrics.MetricsObserver;
 import dan200.computercraft.impl.ApiFactories;
-import dan200.computercraft.shared.computer.apis.CommandAPI;
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
 import dan200.computercraft.shared.computer.terminal.NetworkedTerminal;
 import dan200.computercraft.shared.computer.terminal.TerminalState;
@@ -23,6 +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;
@@ -50,7 +51,8 @@ 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;
@@ -61,17 +63,27 @@ 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);
 
         // Load in the externally registered APIs.
         for (var factory : ApiFactories.getAll()) {
-            var system = new ComputerSystem(computer.getAPIEnvironment());
+            var system = new ComputerSystem(this, computer.getAPIEnvironment(), components);
             var api = factory.create(system);
-            if (api != null) computer.addApi(api, system);
-        }
+            if (api == null) continue;
 
-        if (family == ComputerFamily.COMMAND) addAPI(new CommandAPI(this));
+            system.activate();
+            computer.addApi(api, system);
+        }
     }
 
     public ComputerFamily getFamily() {
@@ -225,10 +237,6 @@ 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/pocket/core/PocketServerComputer.java

@@ -4,6 +4,7 @@
 
 package dan200.computercraft.shared.pocket.core;
 
+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;
@@ -12,6 +13,7 @@ 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 dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.level.ChunkPos;
 
@@ -40,7 +42,10 @@ public final class PocketServerComputer extends ServerComputer {
     private Set<ServerPlayer> tracking = Set.of();
 
     PocketServerComputer(PocketBrain brain, PocketHolder holder, int computerID, @Nullable String label, ComputerFamily family) {
-        super(holder.level(), holder.blockPos(), computerID, label, family, Config.pocketTermWidth, Config.pocketTermHeight);
+        super(
+            holder.level(), holder.blockPos(), computerID, label, family, Config.pocketTermWidth, Config.pocketTermHeight,
+            ComponentMap.builder().add(ComputerComponents.POCKET, brain).build()
+        );
         this.brain = brain;
     }
 

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

@@ -20,7 +20,6 @@ import dan200.computercraft.shared.computer.core.ServerContext;
 import dan200.computercraft.shared.computer.items.IComputerItem;
 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;
@@ -239,8 +238,6 @@ public class PocketComputerItem extends Item implements IComputerItem, IMedia, I
         tag.putInt(NBT_SESSION, registry.getSessionID());
         tag.putUUID(NBT_INSTANCE, computer.register());
 
-        computer.addAPI(new PocketAPI(brain));
-
         // Only turn on when initially creating the computer, rather than each tick.
         if (isMarkedOn(stack) && holder instanceof PocketHolder.PlayerHolder) computer.turnOn();
 

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;
@@ -17,9 +18,9 @@ import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.config.Config;
 import dan200.computercraft.shared.container.BasicContainer;
-import dan200.computercraft.shared.turtle.apis.TurtleAPI;
 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.NonNullList;
@@ -75,10 +76,9 @@ 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;
     }

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));
+        }
+    }
+}