Use Fabric's Item Lookup for registering media providers

We'll switch to capabilities on the (Neo)Forge side for 1.21, when the
capability system is less painful, and then fully deprecate in 1.21.4.

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

@@ -11,7 +11,6 @@ import dan200.computercraft.api.filesystem.Mount;
 import dan200.computercraft.api.filesystem.WritableMount;
 import dan200.computercraft.api.lua.GenericSource;
 import dan200.computercraft.api.lua.ILuaAPIFactory;
-import dan200.computercraft.api.media.MediaProvider;
 import dan200.computercraft.api.media.PrintoutContents;
 import dan200.computercraft.api.network.PacketNetwork;
 import dan200.computercraft.api.network.wired.WiredElement;
@@ -93,11 +92,6 @@ public abstract class AbstractComputerCraftAPI implements ComputerCraftAPIServic
         return BundledRedstone.getDefaultOutput(world, pos, side);
     }
 
-    @Override
-    public final void registerMediaProvider(MediaProvider provider) {
-        MediaProviders.register(provider);
-    }
-
     @Override
     public final PacketNetwork getWirelessNetwork(MinecraftServer server) {
         return ServerContext.get(server).wirelessNetwork();

projects/common/src/main/java/dan200/computercraft/shared/peripheral/diskdrive/DiskDriveBlock.java

@@ -4,9 +4,9 @@
 
 package dan200.computercraft.shared.peripheral.diskdrive;
 
-import dan200.computercraft.impl.MediaProviders;
 import dan200.computercraft.shared.ModRegistry;
 import dan200.computercraft.shared.common.HorizontalContainerBlock;
+import dan200.computercraft.shared.platform.PlatformHelper;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.world.InteractionHand;
@@ -50,7 +50,7 @@ public class DiskDriveBlock extends HorizontalContainerBlock {
             var disk = player.getItemInHand(hand);
             if (disk.isEmpty()) return InteractionResult.PASS;
 
-            if (!level.isClientSide && drive.getDiskStack().isEmpty() && MediaProviders.get(disk) != null) {
+            if (!level.isClientSide && drive.getDiskStack().isEmpty() && PlatformHelper.get().getMedia(disk) != null) {
                 drive.setDiskStack(disk.split(1));
             }
             return InteractionResult.sidedSuccess(level.isClientSide);

projects/common/src/main/java/dan200/computercraft/shared/peripheral/diskdrive/MediaStack.java

@@ -5,7 +5,7 @@
 package dan200.computercraft.shared.peripheral.diskdrive;
 
 import dan200.computercraft.api.media.IMedia;
-import dan200.computercraft.impl.MediaProviders;
+import dan200.computercraft.shared.platform.PlatformHelper;
 import net.minecraft.sounds.SoundEvent;
 import net.minecraft.world.item.ItemStack;
 import org.jspecify.annotations.Nullable;
@@ -23,7 +23,7 @@ record MediaStack(ItemStack stack, @Nullable IMedia media) {
         if (stack.isEmpty()) return EMPTY;
 
         var freshStack = stack.copy();
-        return new MediaStack(freshStack, MediaProviders.get(freshStack));
+        return new MediaStack(freshStack, PlatformHelper.get().getMedia(freshStack));
     }
 
     @Nullable

projects/common/src/main/java/dan200/computercraft/shared/platform/PlatformHelper.java

@@ -7,6 +7,7 @@ package dan200.computercraft.shared.platform;
 import com.google.gson.JsonObject;
 import com.mojang.authlib.GameProfile;
 import com.mojang.brigadier.arguments.ArgumentType;
+import dan200.computercraft.api.media.IMedia;
 import dan200.computercraft.api.network.wired.WiredElement;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.shared.config.ConfigFile;
@@ -424,4 +425,13 @@ public interface PlatformHelper extends dan200.computercraft.impl.PlatformHelper
     default boolean canClickRunClientCommand() {
         return true;
     }
+
+    /**
+     * Find a {@link IMedia} instance for an item stack.
+     *
+     * @param stack The stack to look up the media for.
+     * @return The media instance, or {@code null} if not found.
+     */
+    @Nullable
+    IMedia getMedia(ItemStack stack);
 }

projects/common/src/test/java/dan200/computercraft/TestPlatformHelper.java

@@ -8,6 +8,8 @@ import com.google.auto.service.AutoService;
 import com.google.gson.JsonObject;
 import com.mojang.authlib.GameProfile;
 import com.mojang.brigadier.arguments.ArgumentType;
+import dan200.computercraft.api.media.IMedia;
+import dan200.computercraft.api.media.MediaProvider;
 import dan200.computercraft.api.network.wired.WiredElement;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.impl.AbstractComputerCraftAPI;
@@ -227,6 +229,11 @@ public class TestPlatformHelper extends AbstractComputerCraftAPI implements Plat
         throw new UnsupportedOperationException("Cannot interact with the world inside tests");
     }
 
+    @Override
+    public @Nullable IMedia getMedia(ItemStack stack) {
+        return null;
+    }
+
     @Override
     public ContainerTransfer.Slotted wrapContainer(Container container) {
         throw new UnsupportedOperationException("Cannot wrap container");
@@ -248,6 +255,11 @@ public class TestPlatformHelper extends AbstractComputerCraftAPI implements Plat
         throw new UnsupportedOperationException("Cannot interact with the world inside tests");
     }
 
+    @Override
+    public void registerMediaProvider(MediaProvider provider) {
+        throw new UnsupportedOperationException("Cannot register media providers inside tests");
+    }
+
     @Override
     public String getInstalledVersion() {
         return "1.0";

projects/fabric-api/src/main/java/dan200/computercraft/api/media/MediaLookup.java

@@ -0,0 +1,32 @@
+// SPDX-FileCopyrightText: 2025 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.media;
+
+import dan200.computercraft.api.ComputerCraftAPI;
+import net.fabricmc.fabric.api.lookup.v1.item.ItemApiLookup;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.item.ItemStack;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * {@linkplain ItemApiLookup Item API lookup} for {@link IMedia}.
+ * <p>
+ * The returned {@link IMedia} instance should be a singleton, and not reference the passed {@link ItemStack}.
+ * <p>
+ * Registering a {@link MediaProvider} via {@link ComputerCraftAPI#registerMediaProvider(MediaProvider)} is equivalent
+ * to registering a {@linkplain ItemApiLookup#registerFallback(ItemApiLookup.ItemApiProvider) fallback provider}.
+ */
+public final class MediaLookup {
+    public static final ResourceLocation ID = new ResourceLocation(ComputerCraftAPI.MOD_ID, "media");
+
+    private static final ItemApiLookup<IMedia, @Nullable Void> lookup = ItemApiLookup.get(ID, IMedia.class, Void.class);
+
+    private MediaLookup() {
+    }
+
+    public static ItemApiLookup<IMedia, @Nullable Void> get() {
+        return lookup;
+    }
+}

projects/fabric/src/main/java/dan200/computercraft/impl/ComputerCraftAPIImpl.java

@@ -7,6 +7,8 @@ package dan200.computercraft.impl;
 import com.google.auto.service.AutoService;
 import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.detail.DetailRegistry;
+import dan200.computercraft.api.media.MediaLookup;
+import dan200.computercraft.api.media.MediaProvider;
 import dan200.computercraft.impl.detail.DetailRegistryImpl;
 import dan200.computercraft.shared.details.FluidDetails;
 import net.fabricmc.fabric.api.event.registry.FabricRegistryBuilder;
@@ -41,4 +43,9 @@ public final class ComputerCraftAPIImpl extends AbstractComputerCraftAPI impleme
     public DetailRegistry<StorageView<FluidVariant>> getFluidDetailRegistry() {
         return fluidDetails;
     }
+
+    @Override
+    public void registerMediaProvider(MediaProvider provider) {
+        MediaLookup.get().registerFallback((stack, ctx) -> provider.getMedia(stack));
+    }
 }

projects/fabric/src/main/java/dan200/computercraft/shared/platform/PlatformHelperImpl.java

@@ -10,6 +10,8 @@ import com.google.gson.JsonObject;
 import com.mojang.authlib.GameProfile;
 import com.mojang.brigadier.arguments.ArgumentType;
 import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.media.IMedia;
+import dan200.computercraft.api.media.MediaLookup;
 import dan200.computercraft.api.network.wired.WiredElement;
 import dan200.computercraft.api.node.wired.WiredElementLookup;
 import dan200.computercraft.api.peripheral.IPeripheral;
@@ -317,6 +319,12 @@ public class PlatformHelperImpl implements PlatformHelper {
         return new UseOnResult.Continue(true, true);
     }
 
+    @Override
+    @SuppressWarnings("NullAway") // NullAway doesn't like the null here.
+    public @Nullable IMedia getMedia(ItemStack stack) {
+        return MediaLookup.get().find(stack, null);
+    }
+
     private record RegistryWrapperImpl<T>(
         ResourceLocation name, Registry<T> registry
     ) implements RegistryWrappers.RegistryWrapper<T> {

projects/forge/src/main/java/dan200/computercraft/impl/ComputerCraftAPIImpl.java

@@ -7,6 +7,7 @@ package dan200.computercraft.impl;
 import com.google.auto.service.AutoService;
 import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.detail.DetailRegistry;
+import dan200.computercraft.api.media.MediaProvider;
 import dan200.computercraft.api.network.wired.WiredElement;
 import dan200.computercraft.api.peripheral.IPeripheralProvider;
 import dan200.computercraft.impl.detail.DetailRegistryImpl;
@@ -56,4 +57,9 @@ public final class ComputerCraftAPIImpl extends AbstractComputerCraftAPI impleme
     public DetailRegistry<FluidStack> getFluidStackDetailRegistry() {
         return fluidStackDetails;
     }
+
+    @Override
+    public void registerMediaProvider(MediaProvider provider) {
+        MediaProviders.register(provider);
+    }
 }

projects/forge/src/main/java/dan200/computercraft/shared/platform/PlatformHelperImpl.java

@@ -10,8 +10,10 @@ import com.google.gson.JsonObject;
 import com.mojang.authlib.GameProfile;
 import com.mojang.brigadier.arguments.ArgumentType;
 import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.media.IMedia;
 import dan200.computercraft.api.network.wired.WiredElement;
 import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.impl.MediaProviders;
 import dan200.computercraft.impl.Peripherals;
 import dan200.computercraft.shared.Capabilities;
 import dan200.computercraft.shared.config.ConfigFile;
@@ -348,6 +350,11 @@ public class PlatformHelperImpl implements PlatformHelper {
         return false;
     }
 
+    @Override
+    public @Nullable IMedia getMedia(ItemStack stack) {
+        return MediaProviders.get(stack);
+    }
+
     private record RegistryWrapperImpl<T>(
         ResourceLocation name, ForgeRegistry<T> registry
     ) implements RegistryWrappers.RegistryWrapper<T> {