Add a MessageType for network messages

Everything old is new again!

CC's network message implementation has gone through several iterations:

 - Originally network messages were implemented with a single class,
   which held an packet id/type and and opaque blobs of data (as
   string/int/byte/NBT arrays), and a big switch statement to decode and
   process this data.

 - In 42d3901ee3, we split the messages
   into different classes all inheriting from NetworkMessage - this bit
   we've stuck with ever since.

   Each packet had a `getId(): int` method, which returned the
   discriminator for this packet.

 - However, getId() was only used when registering the packet, not when
   sending, and so in ce0685c31f we
   removed it, just passing in a constant integer at registration
   instead.

 - In 53abe5e56e, we made some relatively
   minor changes to make the code more multi-loader/split-source
   friendly. However, this meant when we finally came to add Fabric
   support (8152f19b6e), we had to
   re-implement a lot of Forge's network code.

In 1.20.4, Forge moves to a system much closer to Fabric's (and indeed,
Minecraft's own CustomPacketPayload), and so it makes sense to adapt to
that now. As such, we:

 - Add a new MessageType interface. This is implemented by the
   loader-specific modules, and holds whatever information is needed to
   register the packet (e.g. discriminator, reader function).

 - Each NetworkMessage now has a type(): MessageType<?> function. This
   is used by the Fabric networking code (and for NeoForge's on 1.20.4)
   instead of a class lookup.

 - NetworkMessages now creates/stores these MessageType<T>s (much like
   we'd do for registries), and provides getters for the
   clientbound/serverbound messages. Mod initialisers then call these
   getters to register packets.

 - For Forge, this is relatively unchanged. For Fabric, we now
   `FabricPacket`s.

projects/common/src/main/java/dan200/computercraft/shared/network/MessageType.java

@@ -0,0 +1,18 @@
+// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.network;
+
+/**
+ * A type of message to send over the network.
+ * <p>
+ * Much like recipe or argument serialisers, each type of {@link NetworkMessage} should have a unique type associated
+ * with it. This holds platform-specific information about how the packet should be sent over the network.
+ *
+ * @param <T> The type of message to send
+ * @see NetworkMessages
+ * @see NetworkMessage#type()
+ */
+public interface MessageType<T extends NetworkMessage<?>> {
+}

projects/common/src/main/java/dan200/computercraft/shared/network/NetworkMessage.java

@@ -17,6 +17,13 @@ import net.minecraft.network.FriendlyByteBuf;
  * @see ServerNetworkContext
  */
 public interface NetworkMessage<T> {
+    /**
+     * Get the type of this message.
+     *
+     * @return The type of this message.
+     */
+    MessageType<?> type();
+
     /**
      * Write this packet to a buffer.
      * <p>
@@ -24,7 +31,7 @@ public interface NetworkMessage<T> {
      *
      * @param buf The buffer to write data to.
      */
-    void toBytes(FriendlyByteBuf buf);
+    void write(FriendlyByteBuf buf);
 
     /**
      * Handle this {@link NetworkMessage}.

projects/common/src/main/java/dan200/computercraft/shared/network/NetworkMessages.java

@@ -4,48 +4,84 @@
 
 package dan200.computercraft.shared.network;
 
+import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.shared.network.client.*;
 import dan200.computercraft.shared.network.server.*;
 import dan200.computercraft.shared.platform.PlatformHelper;
+import it.unimi.dsi.fastutil.ints.IntOpenHashSet;
+import it.unimi.dsi.fastutil.ints.IntSet;
 import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.resources.ResourceLocation;
 
-import java.util.function.Function;
+import java.util.*;
 
 /**
- * Registry for all packets provided by CC: Tweaked.
+ * List of all {@link MessageType}s provided by CC: Tweaked.
  *
  * @see PlatformHelper The platform helper is used to send packets.
  */
 public final class NetworkMessages {
+    private static final IntSet seenIds = new IntOpenHashSet();
+    private static final Set<String> seenChannel = new HashSet<>();
+    private static final List<MessageType<? extends NetworkMessage<ServerNetworkContext>>> serverMessages = new ArrayList<>();
+    private static final List<MessageType<? extends NetworkMessage<ClientNetworkContext>>> clientMessages = new ArrayList<>();
+
+    public static final MessageType<ComputerActionServerMessage> COMPUTER_ACTION = registerServerbound(0, "computer_action", ComputerActionServerMessage.class, ComputerActionServerMessage::new);
+    public static final MessageType<QueueEventServerMessage> QUEUE_EVENT = registerServerbound(1, "queue_event", QueueEventServerMessage.class, QueueEventServerMessage::new);
+    public static final MessageType<KeyEventServerMessage> KEY_EVENT = registerServerbound(2, "key_event", KeyEventServerMessage.class, KeyEventServerMessage::new);
+    public static final MessageType<MouseEventServerMessage> MOUSE_EVENT = registerServerbound(3, "mouse_event", MouseEventServerMessage.class, MouseEventServerMessage::new);
+    public static final MessageType<UploadFileMessage> UPLOAD_FILE = registerServerbound(4, "upload_file", UploadFileMessage.class, UploadFileMessage::new);
+
+    public static final MessageType<ChatTableClientMessage> CHAT_TABLE = registerClientbound(10, "chat_table", ChatTableClientMessage.class, ChatTableClientMessage::new);
+    public static final MessageType<PocketComputerDataMessage> POCKET_COMPUTER_DATA = registerClientbound(11, "pocket_computer_data", PocketComputerDataMessage.class, PocketComputerDataMessage::new);
+    public static final MessageType<PocketComputerDeletedClientMessage> POCKET_COMPUTER_DELETED = registerClientbound(12, "pocket_computer_deleted", PocketComputerDeletedClientMessage.class, PocketComputerDeletedClientMessage::new);
+    public static final MessageType<ComputerTerminalClientMessage> COMPUTER_TERMINAL = registerClientbound(13, "computer_terminal", ComputerTerminalClientMessage.class, ComputerTerminalClientMessage::new);
+    public static final MessageType<PlayRecordClientMessage> PLAY_RECORD = registerClientbound(14, "play_record", PlayRecordClientMessage.class, PlayRecordClientMessage::new);
+    public static final MessageType<MonitorClientMessage> MONITOR_CLIENT = registerClientbound(15, "monitor_client", MonitorClientMessage.class, MonitorClientMessage::new);
+    public static final MessageType<SpeakerAudioClientMessage> SPEAKER_AUDIO = registerClientbound(16, "speaker_audio", SpeakerAudioClientMessage.class, SpeakerAudioClientMessage::new);
+    public static final MessageType<SpeakerMoveClientMessage> SPEAKER_MOVE = registerClientbound(17, "speaker_move", SpeakerMoveClientMessage.class, SpeakerMoveClientMessage::new);
+    public static final MessageType<SpeakerPlayClientMessage> SPEAKER_PLAY = registerClientbound(18, "speaker_play", SpeakerPlayClientMessage.class, SpeakerPlayClientMessage::new);
+    public static final MessageType<SpeakerStopClientMessage> SPEAKER_STOP = registerClientbound(19, "speaker_stop", SpeakerStopClientMessage.class, SpeakerStopClientMessage::new);
+    public static final MessageType<UploadResultMessage> UPLOAD_RESULT = registerClientbound(20, "upload_result", UploadResultMessage.class, UploadResultMessage::new);
+    public static final MessageType<UpgradesLoadedMessage> UPGRADES_LOADED = registerClientbound(21, "upgrades_loaded", UpgradesLoadedMessage.class, UpgradesLoadedMessage::new);
+
     private NetworkMessages() {
     }
 
-    public interface PacketRegistry {
-        <T extends NetworkMessage<ClientNetworkContext>> void registerClientbound(int id, Class<T> type, Function<FriendlyByteBuf, T> decoder);
-
-        <T extends NetworkMessage<ServerNetworkContext>> void registerServerbound(int id, Class<T> type, Function<FriendlyByteBuf, T> decoder);
+    private static <C, T extends NetworkMessage<C>> MessageType<T> register(
+        List<MessageType<? extends NetworkMessage<C>>> messages,
+        int id, String channel, Class<T> klass, FriendlyByteBuf.Reader<T> reader
+    ) {
+        if (!seenIds.add(id)) throw new IllegalArgumentException("Duplicate id " + id);
+        if (!seenChannel.add(channel)) throw new IllegalArgumentException("Duplicate channel " + channel);
+        var type = PlatformHelper.get().createMessageType(id, new ResourceLocation(ComputerCraftAPI.MOD_ID, channel), klass, reader);
+        messages.add(type);
+        return type;
     }
 
-    public static void register(PacketRegistry registry) {
-        // Server messages
-        registry.registerServerbound(0, ComputerActionServerMessage.class, ComputerActionServerMessage::new);
-        registry.registerServerbound(1, QueueEventServerMessage.class, QueueEventServerMessage::new);
-        registry.registerServerbound(2, KeyEventServerMessage.class, KeyEventServerMessage::new);
-        registry.registerServerbound(3, MouseEventServerMessage.class, MouseEventServerMessage::new);
-        registry.registerServerbound(4, UploadFileMessage.class, UploadFileMessage::new);
+    private static <T extends NetworkMessage<ServerNetworkContext>> MessageType<T> registerServerbound(int id, String channel, Class<T> klass, FriendlyByteBuf.Reader<T> reader) {
+        return register(serverMessages, id, channel, klass, reader);
+    }
 
-        // Client messages
-        registry.registerClientbound(10, ChatTableClientMessage.class, ChatTableClientMessage::new);
-        registry.registerClientbound(11, PocketComputerDataMessage.class, PocketComputerDataMessage::new);
-        registry.registerClientbound(12, PocketComputerDeletedClientMessage.class, PocketComputerDeletedClientMessage::new);
-        registry.registerClientbound(13, ComputerTerminalClientMessage.class, ComputerTerminalClientMessage::new);
-        registry.registerClientbound(14, PlayRecordClientMessage.class, PlayRecordClientMessage::new);
-        registry.registerClientbound(15, MonitorClientMessage.class, MonitorClientMessage::new);
-        registry.registerClientbound(16, SpeakerAudioClientMessage.class, SpeakerAudioClientMessage::new);
-        registry.registerClientbound(17, SpeakerMoveClientMessage.class, SpeakerMoveClientMessage::new);
-        registry.registerClientbound(18, SpeakerPlayClientMessage.class, SpeakerPlayClientMessage::new);
-        registry.registerClientbound(19, SpeakerStopClientMessage.class, SpeakerStopClientMessage::new);
-        registry.registerClientbound(20, UploadResultMessage.class, UploadResultMessage::new);
-        registry.registerClientbound(21, UpgradesLoadedMessage.class, UpgradesLoadedMessage::new);
+    private static <T extends NetworkMessage<ClientNetworkContext>> MessageType<T> registerClientbound(int id, String channel, Class<T> klass, FriendlyByteBuf.Reader<T> reader) {
+        return register(clientMessages, id, channel, klass, reader);
+    }
+
+    /**
+     * Get all serverbound message types.
+     *
+     * @return An unmodifiable sequence of all serverbound message types.
+     */
+    public static Collection<MessageType<? extends NetworkMessage<ServerNetworkContext>>> getServerbound() {
+        return Collections.unmodifiableCollection(serverMessages);
+    }
+
+    /**
+     * Get all clientbound message types.
+     *
+     * @return An unmodifiable sequence of all clientbound message types.
+     */
+    public static Collection<MessageType<? extends NetworkMessage<ClientNetworkContext>>> getClientbound() {
+        return Collections.unmodifiableCollection(clientMessages);
     }
 }

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

@@ -5,7 +5,9 @@
 package dan200.computercraft.shared.network.client;
 
 import dan200.computercraft.shared.command.text.TableBuilder;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.chat.Component;
 
@@ -43,7 +45,7 @@ public class ChatTableClientMessage implements NetworkMessage<ClientNetworkConte
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeUtf(table.getId(), MAX_LEN);
         buf.writeVarInt(table.getColumns());
         buf.writeBoolean(table.getHeaders() != null);
@@ -63,4 +65,9 @@ public class ChatTableClientMessage implements NetworkMessage<ClientNetworkConte
     public void handle(ClientNetworkContext context) {
         context.handleChatTable(table);
     }
+
+    @Override
+    public MessageType<ChatTableClientMessage> type() {
+        return NetworkMessages.CHAT_TABLE;
+    }
 }

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

@@ -5,7 +5,9 @@
 package dan200.computercraft.shared.network.client;
 
 import dan200.computercraft.shared.computer.terminal.TerminalState;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 
@@ -25,7 +27,7 @@ public class ComputerTerminalClientMessage implements NetworkMessage<ClientNetwo
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeVarInt(containerId);
         terminal.write(buf);
     }
@@ -34,4 +36,9 @@ public class ComputerTerminalClientMessage implements NetworkMessage<ClientNetwo
     public void handle(ClientNetworkContext context) {
         context.handleComputerTerminal(containerId, terminal);
     }
+
+    @Override
+    public MessageType<ComputerTerminalClientMessage> type() {
+        return NetworkMessages.COMPUTER_TERMINAL;
+    }
 }

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

@@ -5,7 +5,9 @@
 package dan200.computercraft.shared.network.client;
 
 import dan200.computercraft.shared.computer.terminal.TerminalState;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.core.BlockPos;
 import net.minecraft.network.FriendlyByteBuf;
 
@@ -25,7 +27,7 @@ public class MonitorClientMessage implements NetworkMessage<ClientNetworkContext
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeBlockPos(pos);
         state.write(buf);
     }
@@ -34,4 +36,9 @@ public class MonitorClientMessage implements NetworkMessage<ClientNetworkContext
     public void handle(ClientNetworkContext context) {
         context.handleMonitorData(pos, state);
     }
+
+    @Override
+    public MessageType<MonitorClientMessage> type() {
+        return NetworkMessages.MONITOR_CLIENT;
+    }
 }

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

@@ -4,7 +4,9 @@
 
 package dan200.computercraft.shared.network.client;
 
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.peripheral.diskdrive.DiskDriveBlockEntity;
 import net.minecraft.core.BlockPos;
 import net.minecraft.network.FriendlyByteBuf;
@@ -43,7 +45,7 @@ public class PlayRecordClientMessage implements NetworkMessage<ClientNetworkCont
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeBlockPos(pos);
         buf.writeNullable(soundEvent, (b, e) -> e.writeToNetwork(b));
         buf.writeNullable(name, FriendlyByteBuf::writeUtf);
@@ -53,4 +55,9 @@ public class PlayRecordClientMessage implements NetworkMessage<ClientNetworkCont
     public void handle(ClientNetworkContext context) {
         context.handlePlayRecord(pos, soundEvent, name);
     }
+
+    @Override
+    public MessageType<PlayRecordClientMessage> type() {
+        return NetworkMessages.PLAY_RECORD;
+    }
 }

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

@@ -7,7 +7,9 @@ package dan200.computercraft.shared.network.client;
 import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.terminal.NetworkedTerminal;
 import dan200.computercraft.shared.computer.terminal.TerminalState;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.pocket.core.PocketServerComputer;
 import net.minecraft.network.FriendlyByteBuf;
 
@@ -35,7 +37,7 @@ public class PocketComputerDataMessage implements NetworkMessage<ClientNetworkCo
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeVarInt(instanceId);
         buf.writeEnum(state);
         buf.writeVarInt(lightState);
@@ -46,4 +48,9 @@ public class PocketComputerDataMessage implements NetworkMessage<ClientNetworkCo
     public void handle(ClientNetworkContext context) {
         context.handlePocketComputerData(instanceId, state, lightState, terminal);
     }
+
+    @Override
+    public MessageType<PocketComputerDataMessage> type() {
+        return NetworkMessages.POCKET_COMPUTER_DATA;
+    }
 }

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

@@ -4,7 +4,9 @@
 
 package dan200.computercraft.shared.network.client;
 
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 
 
@@ -20,7 +22,7 @@ public class PocketComputerDeletedClientMessage implements NetworkMessage<Client
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeVarInt(instanceId);
     }
 
@@ -28,4 +30,9 @@ public class PocketComputerDeletedClientMessage implements NetworkMessage<Client
     public void handle(ClientNetworkContext context) {
         context.handlePocketComputerDeleted(instanceId);
     }
+
+    @Override
+    public MessageType<PocketComputerDeletedClientMessage> type() {
+        return NetworkMessages.POCKET_COMPUTER_DELETED;
+    }
 }

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

@@ -4,7 +4,9 @@
 
 package dan200.computercraft.shared.network.client;
 
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerBlockEntity;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerPosition;
 import net.minecraft.network.FriendlyByteBuf;
@@ -47,7 +49,7 @@ public class SpeakerAudioClientMessage implements NetworkMessage<ClientNetworkCo
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeUUID(source);
         pos.write(buf);
         buf.writeFloat(volume);
@@ -58,4 +60,9 @@ public class SpeakerAudioClientMessage implements NetworkMessage<ClientNetworkCo
     public void handle(ClientNetworkContext context) {
         context.handleSpeakerAudio(source, pos, volume);
     }
+
+    @Override
+    public MessageType<SpeakerAudioClientMessage> type() {
+        return NetworkMessages.SPEAKER_AUDIO;
+    }
 }

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

@@ -4,7 +4,9 @@
 
 package dan200.computercraft.shared.network.client;
 
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerBlockEntity;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerPosition;
 import net.minecraft.network.FriendlyByteBuf;
@@ -33,7 +35,7 @@ public class SpeakerMoveClientMessage implements NetworkMessage<ClientNetworkCon
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeUUID(source);
         pos.write(buf);
     }
@@ -42,4 +44,9 @@ public class SpeakerMoveClientMessage implements NetworkMessage<ClientNetworkCon
     public void handle(ClientNetworkContext context) {
         context.handleSpeakerMove(source, pos);
     }
+
+    @Override
+    public MessageType<SpeakerMoveClientMessage> type() {
+        return NetworkMessages.SPEAKER_MOVE;
+    }
 }

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

@@ -4,7 +4,9 @@
 
 package dan200.computercraft.shared.network.client;
 
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerBlockEntity;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerPosition;
 import net.minecraft.network.FriendlyByteBuf;
@@ -43,7 +45,7 @@ public class SpeakerPlayClientMessage implements NetworkMessage<ClientNetworkCon
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeUUID(source);
         pos.write(buf);
         buf.writeResourceLocation(sound);
@@ -55,4 +57,9 @@ public class SpeakerPlayClientMessage implements NetworkMessage<ClientNetworkCon
     public void handle(ClientNetworkContext context) {
         context.handleSpeakerPlay(source, pos, sound, volume, pitch);
     }
+
+    @Override
+    public MessageType<SpeakerPlayClientMessage> type() {
+        return NetworkMessages.SPEAKER_PLAY;
+    }
 }

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

@@ -4,7 +4,9 @@
 
 package dan200.computercraft.shared.network.client;
 
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.peripheral.speaker.SpeakerBlockEntity;
 import net.minecraft.network.FriendlyByteBuf;
 
@@ -29,7 +31,7 @@ public class SpeakerStopClientMessage implements NetworkMessage<ClientNetworkCon
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeUUID(source);
     }
 
@@ -37,4 +39,9 @@ public class SpeakerStopClientMessage implements NetworkMessage<ClientNetworkCon
     public void handle(ClientNetworkContext context) {
         context.handleSpeakerStop(source);
     }
+
+    @Override
+    public MessageType<SpeakerStopClientMessage> type() {
+        return NetworkMessages.SPEAKER_STOP;
+    }
 }

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

@@ -13,7 +13,9 @@ import dan200.computercraft.api.upgrades.UpgradeSerialiser;
 import dan200.computercraft.impl.PocketUpgrades;
 import dan200.computercraft.impl.TurtleUpgrades;
 import dan200.computercraft.impl.UpgradeManager;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.platform.PlatformHelper;
 import net.minecraft.core.Registry;
 import net.minecraft.network.FriendlyByteBuf;
@@ -27,7 +29,7 @@ import java.util.Objects;
 /**
  * Syncs turtle and pocket upgrades to the client.
  */
-public class UpgradesLoadedMessage implements NetworkMessage<ClientNetworkContext> {
+public final class UpgradesLoadedMessage implements NetworkMessage<ClientNetworkContext> {
     private final Map<String, UpgradeManager.UpgradeWrapper<TurtleUpgradeSerialiser<?>, ITurtleUpgrade>> turtleUpgrades;
     private final Map<String, UpgradeManager.UpgradeWrapper<PocketUpgradeSerialiser<?>, IPocketUpgrade>> pocketUpgrades;
 
@@ -65,7 +67,7 @@ public class UpgradesLoadedMessage implements NetworkMessage<ClientNetworkContex
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         toBytes(buf, TurtleUpgradeSerialiser.registryId(), turtleUpgrades);
         toBytes(buf, PocketUpgradeSerialiser.registryId(), pocketUpgrades);
     }
@@ -95,4 +97,9 @@ public class UpgradesLoadedMessage implements NetworkMessage<ClientNetworkContex
         TurtleUpgrades.instance().loadFromNetwork(turtleUpgrades);
         PocketUpgrades.instance().loadFromNetwork(pocketUpgrades);
     }
+
+    @Override
+    public MessageType<UpgradesLoadedMessage> type() {
+        return NetworkMessages.UPGRADES_LOADED;
+    }
 }

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

@@ -6,7 +6,9 @@ package dan200.computercraft.shared.network.client;
 
 import dan200.computercraft.core.util.Nullability;
 import dan200.computercraft.shared.computer.upload.UploadResult;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.chat.Component;
 import net.minecraft.world.inventory.AbstractContainerMenu;
@@ -43,7 +45,7 @@ public class UploadResultMessage implements NetworkMessage<ClientNetworkContext>
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeVarInt(containerId);
         buf.writeEnum(result);
         if (result == UploadResult.ERROR) buf.writeComponent(Nullability.assertNonNull(errorMessage));
@@ -53,4 +55,9 @@ public class UploadResultMessage implements NetworkMessage<ClientNetworkContext>
     public void handle(ClientNetworkContext context) {
         context.handleUploadResult(containerId, result, errorMessage);
     }
+
+    @Override
+    public MessageType<UploadResultMessage> type() {
+        return NetworkMessages.UPLOAD_RESULT;
+    }
 }

projects/common/src/main/java/dan200/computercraft/shared/network/server/ComputerActionServerMessage.java

@@ -5,6 +5,8 @@
 package dan200.computercraft.shared.network.server;
 
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
+import dan200.computercraft.shared.network.MessageType;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 
@@ -23,8 +25,8 @@ public class ComputerActionServerMessage extends ComputerServerMessage {
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
-        super.toBytes(buf);
+    public void write(FriendlyByteBuf buf) {
+        super.write(buf);
         buf.writeEnum(action);
     }
 
@@ -37,6 +39,11 @@ public class ComputerActionServerMessage extends ComputerServerMessage {
         }
     }
 
+    @Override
+    public MessageType<ComputerActionServerMessage> type() {
+        return NetworkMessages.COMPUTER_ACTION;
+    }
+
     public enum Action {
         TURN_ON,
         SHUTDOWN,

projects/common/src/main/java/dan200/computercraft/shared/network/server/ComputerServerMessage.java

@@ -28,7 +28,7 @@ public abstract class ComputerServerMessage implements NetworkMessage<ServerNetw
 
     @Override
     @OverridingMethodsMustInvokeSuper
-    public void toBytes(FriendlyByteBuf buf) {
+    public void write(FriendlyByteBuf buf) {
         buf.writeVarInt(containerId);
     }
 

projects/common/src/main/java/dan200/computercraft/shared/network/server/KeyEventServerMessage.java

@@ -5,6 +5,8 @@
 package dan200.computercraft.shared.network.server;
 
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
+import dan200.computercraft.shared.network.MessageType;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 
@@ -30,8 +32,8 @@ public class KeyEventServerMessage extends ComputerServerMessage {
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
-        super.toBytes(buf);
+    public void write(FriendlyByteBuf buf) {
+        super.write(buf);
         buf.writeByte(type);
         buf.writeVarInt(key);
     }
@@ -45,4 +47,9 @@ public class KeyEventServerMessage extends ComputerServerMessage {
             input.keyDown(key, type == TYPE_REPEAT);
         }
     }
+
+    @Override
+    public MessageType<KeyEventServerMessage> type() {
+        return NetworkMessages.KEY_EVENT;
+    }
 }

projects/common/src/main/java/dan200/computercraft/shared/network/server/MouseEventServerMessage.java

@@ -5,6 +5,8 @@
 package dan200.computercraft.shared.network.server;
 
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
+import dan200.computercraft.shared.network.MessageType;
+import dan200.computercraft.shared.network.NetworkMessages;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 
@@ -37,8 +39,8 @@ public class MouseEventServerMessage extends ComputerServerMessage {
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
-        super.toBytes(buf);
+    public void write(FriendlyByteBuf buf) {
+        super.write(buf);
         buf.writeByte(type);
         buf.writeVarInt(arg);
         buf.writeVarInt(x);
@@ -55,4 +57,9 @@ public class MouseEventServerMessage extends ComputerServerMessage {
             case TYPE_SCROLL -> input.mouseScroll(arg, x, y);
         }
     }
+
+    @Override
+    public MessageType<MouseEventServerMessage> type() {
+        return NetworkMessages.MOUSE_EVENT;
+    }
 }

projects/common/src/main/java/dan200/computercraft/shared/network/server/QueueEventServerMessage.java

@@ -7,6 +7,8 @@ package dan200.computercraft.shared.network.server;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
 import dan200.computercraft.shared.computer.menu.ServerInputHandler;
+import dan200.computercraft.shared.network.MessageType;
+import dan200.computercraft.shared.network.NetworkMessages;
 import dan200.computercraft.shared.util.NBTUtil;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.inventory.AbstractContainerMenu;
@@ -37,8 +39,8 @@ public class QueueEventServerMessage extends ComputerServerMessage {
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
-        super.toBytes(buf);
+    public void write(FriendlyByteBuf buf) {
+        super.write(buf);
         buf.writeUtf(event);
         buf.writeNbt(args == null ? null : NBTUtil.encodeObjects(args));
     }
@@ -47,4 +49,9 @@ public class QueueEventServerMessage extends ComputerServerMessage {
     protected void handle(ServerNetworkContext context, ComputerMenu container) {
         container.getInput().queueEvent(event, args);
     }
+
+    @Override
+    public MessageType<QueueEventServerMessage> type() {
+        return NetworkMessages.QUEUE_EVENT;
+    }
 }

projects/common/src/main/java/dan200/computercraft/shared/network/server/UploadFileMessage.java

@@ -9,6 +9,8 @@ import dan200.computercraft.shared.computer.menu.ComputerMenu;
 import dan200.computercraft.shared.computer.upload.FileSlice;
 import dan200.computercraft.shared.computer.upload.FileUpload;
 import dan200.computercraft.shared.config.Config;
+import dan200.computercraft.shared.network.MessageType;
+import dan200.computercraft.shared.network.NetworkMessages;
 import io.netty.handler.codec.DecoderException;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.inventory.AbstractContainerMenu;
@@ -91,8 +93,8 @@ public class UploadFileMessage extends ComputerServerMessage {
     }
 
     @Override
-    public void toBytes(FriendlyByteBuf buf) {
-        super.toBytes(buf);
+    public void write(FriendlyByteBuf buf) {
+        super.write(buf);
         buf.writeUUID(uuid);
         buf.writeByte(flag);
 
@@ -166,4 +168,9 @@ public class UploadFileMessage extends ComputerServerMessage {
         input.continueUpload(uuid, slices);
         if ((flag & FLAG_LAST) != 0) input.finishUpload(player, uuid);
     }
+
+    @Override
+    public MessageType<UploadFileMessage> type() {
+        return NetworkMessages.UPLOAD_FILE;
+    }
 }

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

@@ -10,6 +10,7 @@ import com.mojang.brigadier.arguments.ArgumentType;
 import dan200.computercraft.api.network.wired.WiredElement;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.shared.config.ConfigFile;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
 import dan200.computercraft.shared.network.client.ClientNetworkContext;
 import dan200.computercraft.shared.network.container.ContainerData;
@@ -164,6 +165,18 @@ public interface PlatformHelper extends dan200.computercraft.impl.PlatformHelper
      */
     void openMenu(Player player, MenuProvider owner, ContainerData menu);
 
+    /**
+     * Create a new {@link MessageType}.
+     *
+     * @param id      The descriminator for this message type.
+     * @param channel The channel name for this message type.
+     * @param klass   The type of this message.
+     * @param reader  The function which reads the packet from a buffer. Should be the inverse to {@link NetworkMessage#write(FriendlyByteBuf)}.
+     * @param <T>     The type of this message.
+     * @return The new {@link MessageType} instance.
+     */
+    <T extends NetworkMessage<?>> MessageType<T> createMessageType(int id, ResourceLocation channel, Class<T> klass, FriendlyByteBuf.Reader<T> reader);
+
     /**
      * Send a message to a specific player.
      *

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

@@ -13,6 +13,7 @@ import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.impl.AbstractComputerCraftAPI;
 import dan200.computercraft.impl.ComputerCraftAPIService;
 import dan200.computercraft.shared.config.ConfigFile;
+import dan200.computercraft.shared.network.MessageType;
 import dan200.computercraft.shared.network.NetworkMessage;
 import dan200.computercraft.shared.network.client.ClientNetworkContext;
 import dan200.computercraft.shared.network.container.ContainerData;
@@ -168,6 +169,13 @@ public class TestPlatformHelper extends AbstractComputerCraftAPI implements Plat
         throw new UnsupportedOperationException("Cannot open menu inside tests");
     }
 
+    @Override
+    public <T extends NetworkMessage<?>> MessageType<T> createMessageType(int id, ResourceLocation channel, Class<T> klass, FriendlyByteBuf.Reader<T> reader) {
+        record TypeImpl<T extends NetworkMessage<?>>(Function<FriendlyByteBuf, T> reader) implements MessageType<T> {
+        }
+        return new TypeImpl<>(reader);
+    }
+
     @Override
     public ComponentAccess<IPeripheral> createPeripheralAccess(Consumer<Direction> invalidate) {
         throw new UnsupportedOperationException("Cannot interact with the world inside tests");

projects/common/src/test/java/dan200/computercraft/shared/network/client/PlayRecordClientMessageTest.java

@@ -29,7 +29,7 @@ class PlayRecordClientMessageTest {
     @Property
     public void testRoundTrip(@ForAll("message") PlayRecordClientMessage message) {
         var buffer = new FriendlyByteBuf(Unpooled.directBuffer());
-        message.toBytes(buffer);
+        message.write(buffer);
 
         var converted = new PlayRecordClientMessage(buffer);
         assertEquals(buffer.readableBytes(), 0, "Whole packet was read");

projects/common/src/test/java/dan200/computercraft/shared/network/server/UploadFileMessageTest.java

@@ -63,7 +63,7 @@ public class UploadFileMessageTest {
     private static List<UploadFileMessage> roundtripPackets(List<UploadFileMessage> packets) {
         return packets.stream().map(packet -> {
             var buffer = new FriendlyByteBuf(Unpooled.directBuffer());
-            packet.toBytes(buffer);
+            packet.write(buffer);
             // We include things like file size in the packet, but not in the count, so grant a slightly larger threshold.
             assertThat("Packet is too large", buffer.writerIndex(), lessThanOrEqualTo(MAX_PACKET_SIZE + 128));
             if ((packet.flag & FLAG_LAST) == 0) {