Add the stop spectating entity rule type

src/main/java/xyz/nucleoid/plasmid/api/game/rule/GameRuleType.java

@@ -111,6 +111,7 @@ public final class GameRuleType {
             .enforces(CoralDeathEvent.EVENT, result -> (world, pos, from, to) -> result);
 
     public static final GameRuleType DISMOUNT_VEHICLE = GameRuleType.create();
+    public static final GameRuleType STOP_SPECTATING_ENTITY = GameRuleType.create();
     public static final GameRuleType PLAYER_PROJECTILE_KNOCKBACK = GameRuleType.create();
     public static final GameRuleType TRIDENTS_LOYAL_IN_VOID = GameRuleType.create();
     public static final GameRuleType MODIFY_INVENTORY = GameRuleType.create();

src/main/java/xyz/nucleoid/plasmid/mixin/game/rule/ServerPlayerEntityMixin.java

@@ -1,6 +1,8 @@
 package xyz.nucleoid.plasmid.mixin.game.rule;
 
+import com.llamalad7.mixinextras.injector.v2.WrapWithCondition;
 import com.mojang.authlib.GameProfile;
+import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.util.math.BlockPos;
@@ -9,14 +11,32 @@
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+import xyz.nucleoid.plasmid.api.game.rule.GameRuleType;
 import xyz.nucleoid.plasmid.impl.game.manager.GameSpaceManagerImpl;
+import xyz.nucleoid.stimuli.event.EventResult;
 
 @Mixin(ServerPlayerEntity.class)
 public abstract class ServerPlayerEntityMixin extends PlayerEntity {
     private ServerPlayerEntityMixin(World world, BlockPos pos, float yaw, GameProfile profile) {
         super(world, pos, yaw, profile);
     }
 
+    @WrapWithCondition(
+            method = "tick",
+            // The targeted call handles shifting to stop spectating
+            // The other call handles dead entities, which should always stop being spectated
+            at = @At(value = "INVOKE", target = "Lnet/minecraft/server/network/ServerPlayerEntity;setCameraEntity(Lnet/minecraft/entity/Entity;)V", ordinal = 0)
+    )
+    private boolean preventStopSpectatingEntity(ServerPlayerEntity player, Entity entity) {
+        var gameSpace = GameSpaceManagerImpl.get().byPlayer(player);
+
+        if (gameSpace != null && gameSpace.getBehavior().testRule(GameRuleType.STOP_SPECTATING_ENTITY) == EventResult.DENY) {
+            return false;
+        }
+
+        return true;
+    }
+
     @Inject(method = "isPvpEnabled", at = @At("HEAD"), cancellable = true)
     private void allowPvPInGames(CallbackInfoReturnable<Boolean> cir) {
         var gameSpace = GameSpaceManagerImpl.get().byPlayer(this);

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

@@ -6,8 +6,10 @@
 import net.minecraft.block.ButtonBlock;
 import net.minecraft.block.LeavesBlock;
 import net.minecraft.block.enums.BlockFace;
+import net.minecraft.entity.EntityType;
 import net.minecraft.item.Item;
 import net.minecraft.item.Items;
+import net.minecraft.nbt.NbtCompound;
 import net.minecraft.scoreboard.AbstractTeam;
 import net.minecraft.screen.ScreenTexts;
 import net.minecraft.server.network.ServerPlayerEntity;
@@ -18,11 +20,13 @@
 import net.minecraft.util.Identifier;
 import net.minecraft.util.Util;
 import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Direction;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.GameMode;
 import net.minecraft.world.GameRules;
 import xyz.nucleoid.fantasy.RuntimeWorldConfig;
 import xyz.nucleoid.map_templates.BlockBounds;
+import xyz.nucleoid.map_templates.MapEntity;
 import xyz.nucleoid.map_templates.MapTemplate;
 import xyz.nucleoid.plasmid.api.game.*;
 import xyz.nucleoid.plasmid.api.game.common.team.*;
@@ -152,7 +156,7 @@ private static GameResult startGame(GameSpace gameSpace) {
             long currentTime = gameSpace.getTime();
             activity.deny(GameRuleType.PVP).allow(GameRuleType.MODIFY_ARMOR);
             activity.deny(GameRuleType.FALL_DAMAGE).deny(GameRuleType.HUNGER);
-            activity.deny(GameRuleType.THROW_ITEMS);
+            activity.deny(GameRuleType.THROW_ITEMS).deny(GameRuleType.STOP_SPECTATING_ENTITY);
 
             activity.deny(GameRuleType.INTERACTION).allow(GameRuleType.USE_BLOCKS);
 
@@ -214,6 +218,13 @@ private static MapTemplate generateMapTemplate(BlockState state) {
         var edge = new BlockPos(max.getX(), max.getY() + 1, max.getZ());
         template.setBlockState(edge, BUTTON);
 
+        var armorStandNbt = new NbtCompound();
+        armorStandNbt.putString("id", EntityType.getId(EntityType.ARMOR_STAND).toString());
+        armorStandNbt.putBoolean("NoGravity", true);
+
+        var armorStandPos = Vec3d.ofBottomCenter(edge.offset(Direction.WEST));
+        template.addEntity(new MapEntity(armorStandPos, armorStandNbt));
+
         for (var pos : bounds) {
             template.setBlockState(pos, state);
         }