Make GameSpace attachment API strictly typed

src/main/java/xyz/nucleoid/plasmid/game/GameAttachment.java

@@ -0,0 +1,20 @@
+package xyz.nucleoid.plasmid.game;
+
+import net.minecraft.util.Identifier;
+
+public class GameAttachment<T> {
+    private final Identifier id;
+
+    private GameAttachment(Identifier id) {
+        this.id = id;
+    }
+
+    public static <T> GameAttachment<T> create(Identifier id) {
+        return new GameAttachment<>(id);
+    }
+
+    @Override
+    public String toString() {
+        return this.id.toString();
+    }
+}

src/main/java/xyz/nucleoid/plasmid/game/GameAttachmentHolder.java

@@ -0,0 +1,18 @@
+package xyz.nucleoid.plasmid.game;
+
+import org.jetbrains.annotations.Nullable;
+
+public interface GameAttachmentHolder {
+    @Nullable
+    <T> T getAttachment(GameAttachment<? extends T> attachment);
+
+    default <T> T getAttachmentOrThrow(GameAttachment<? extends T> attachment) {
+        T value = this.getAttachment(attachment);
+        if (value == null) {
+            throw new IllegalArgumentException("Missing attachment " + attachment + " on " + this);
+        }
+        return value;
+    }
+
+    <T> void setAttachment(GameAttachment<? super T> attachment, @Nullable T value);
+}

src/main/java/xyz/nucleoid/plasmid/game/GameSpace.java

@@ -23,7 +23,7 @@
  * @see GameType
  * @see GameActivity
  */
-public interface GameSpace {
+public interface GameSpace extends GameAttachmentHolder {
     /**
      * @return the host server of this {@link GameSpace}
      */
@@ -109,8 +109,4 @@ public interface GameSpace {
      * @return true if this GameSpace is closed, false otherwise
      */
     boolean isClosed();
-
-    @Nullable
-    <T> T getAttachment(String key);
-    void setAttachment(String key, @Nullable Object obj);
 }

src/main/java/xyz/nucleoid/plasmid/game/manager/ManagedGameSpace.java

@@ -1,13 +1,15 @@
 package xyz.nucleoid.plasmid.game.manager;
 
 import com.google.common.collect.Lists;
+import it.unimi.dsi.fastutil.objects.Reference2ObjectOpenHashMap;
 import me.lucko.fabric.api.permissions.v0.Permissions;
 import net.minecraft.registry.RegistryKey;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.text.Text;
 import net.minecraft.util.Formatting;
 import net.minecraft.world.World;
+import org.jetbrains.annotations.Nullable;
 import xyz.nucleoid.fantasy.RuntimeWorldHandle;
 import xyz.nucleoid.plasmid.Plasmid;
 import xyz.nucleoid.plasmid.event.GameEvents;
@@ -19,7 +21,6 @@
 import xyz.nucleoid.plasmid.game.player.PlayerOfferResult;
 
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Consumer;
 
@@ -40,7 +41,7 @@ public final class ManagedGameSpace implements GameSpace {
     private boolean closed;
 
     private final GameSpaceStatistics statistics = new GameSpaceStatistics();
-    private final Map<String, Object> attachments = new HashMap<>();
+    private final Map<GameAttachment<?>, Object> attachments = new Reference2ObjectOpenHashMap<>();
 
     ManagedGameSpace(MinecraftServer server, GameSpaceManager manager, GameSpaceMetadata metadata) {
         this.server = server;
@@ -171,18 +172,20 @@ public GameSpaceStatistics getStatistics() {
     public boolean isClosed() {
         return this.closed;
     }
+
     @Override
-    public <T> T getAttachment(String key) {
-        //noinspection unchecked
-        return (T) this.attachments.get(key);
+    @Nullable
+    @SuppressWarnings("unchecked")
+    public <T> T getAttachment(GameAttachment<? extends T> attachment) {
+        return (T) this.attachments.get(attachment);
     }
 
     @Override
-    public void setAttachment(String key, Object obj) {
-        if (obj == null) {
-            this.attachments.remove(key);
+    public <T> void setAttachment(GameAttachment<? super T> attachment, @Nullable T value) {
+        if (value == null) {
+            this.attachments.remove(attachment);
         } else {
-            this.attachments.put(key, obj);
+            this.attachments.put(attachment, value);
         }
     }
 

src/testmod/java/xyz/nucleoid/plasmid/test/TestGame.java

@@ -81,8 +81,10 @@ public static GameOpenProcedure open(GameOpenContext<TestConfig> context) {
         });
     }
 
+    private static final GameAttachment<Item> TEST = GameAttachment.create(new Identifier("plasmid", "test"));
+
     private static GameResult startGame(GameSpace gameSpace) {
-        gameSpace.setAttachment("test", Items.POTATO);
+        gameSpace.setAttachment(TEST, Items.POTATO);
 
         gameSpace.setActivity((activity) -> {
             long currentTime = gameSpace.getTime();
@@ -92,7 +94,7 @@ private static GameResult startGame(GameSpace gameSpace) {
 
             activity.deny(GameRuleType.INTERACTION).allow(GameRuleType.USE_BLOCKS);
 
-            Item potato = gameSpace.getAttachment("test");
+            Item potato = gameSpace.getAttachment(TEST);
 
             var teamManager = TeamManager.addTo(activity);
             teamManager.addTeam(TEAM);