Add leash events

src/main/java/xyz/nucleoid/stimuli/event/entity/EntityLeashEvent.java

@@ -0,0 +1,41 @@
+package xyz.nucleoid.stimuli.event.entity;
+
+import net.minecraft.entity.Entity;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.Hand;
+import net.minecraft.util.math.BlockPos;
+import org.jetbrains.annotations.Nullable;
+import xyz.nucleoid.stimuli.event.StimulusEvent;
+
+public class EntityLeashEvent {
+    /**
+     * Called when a leash is attached to either a holding {@link Entity} or a {@link BlockPos}.
+	 * 
+	 * <p>A leash holder can be either a player or an existing leash knot.
+     * A leash position may or may not contain a leash knot yet.
+     *
+     * <p>Upon return:
+     * <ul>
+     * <li>{@link ActionResult#SUCCESS} cancels further handlers and allows the leash to be attached.
+     * <li>{@link ActionResult#FAIL} cancels further handlers and prevents the leash from being attached.
+     * <li>{@link ActionResult#PASS} moves on to the next listener.</ul>
+     */
+    public static final StimulusEvent<Attach> ATTACH = StimulusEvent.create(Attach.class, ctx -> (entity, leashHolder, leashPos, player, hand) -> {
+        try {
+            for (var listener : ctx.getListeners()) {
+                var result = listener.onAttachLeash(entity, leashHolder, leashPos, player, hand);
+                if (result != ActionResult.PASS) {
+                    return result;
+                }
+            }
+        } catch (Throwable t) {
+            ctx.handleException(t);
+        }
+        return ActionResult.PASS;
+    });
+
+    public interface Attach {
+        ActionResult onAttachLeash(Entity entity, @Nullable Entity leashHolder, @Nullable BlockPos leashPos, ServerPlayerEntity player, @Nullable Hand hand);
+    }
+}

src/main/java/xyz/nucleoid/stimuli/mixin/entity/EntityMixin.java

@@ -0,0 +1,56 @@
+package xyz.nucleoid.stimuli.mixin.entity;
+
+import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
+import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
+import com.llamalad7.mixinextras.sugar.Local;
+import net.minecraft.entity.Entity;
+import net.minecraft.entity.Leashable;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.network.packet.s2c.play.ScreenHandlerSlotUpdateS2CPacket;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.Hand;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import xyz.nucleoid.stimuli.Stimuli;
+import xyz.nucleoid.stimuli.event.entity.EntityLeashEvent;
+
+@Mixin(Entity.class)
+public class EntityMixin {
+    @WrapOperation(
+            method = "interact",
+            at = @At(
+                value = "INVOKE",
+                target = "Lnet/minecraft/entity/Leashable;canLeashAttachTo()Z"
+            )
+    )
+    private static boolean onLeashAttach(Leashable leashable, Operation<Boolean> original, @Local(argsOnly = true) PlayerEntity player, @Local(argsOnly = true) Hand hand) {
+        if (!original.call(leashable)) {
+            return false;
+        }
+
+        // Leashable instance is the same as this entity
+        var entity = (Entity) leashable;
+
+        if (!entity.getWorld().isClient()) {
+            var serverPlayer = (ServerPlayerEntity) player;
+
+            var events = Stimuli.select();
+
+            try (var invokers = events.forEntity(serverPlayer)) {
+                var result = invokers.get(EntityLeashEvent.ATTACH).onAttachLeash(entity, serverPlayer, null, serverPlayer, hand);
+                if (result == ActionResult.FAIL) {
+                    var stack = player.getStackInHand(hand);
+
+                    // notify the client that this action did not go through
+                    int slot = hand == Hand.MAIN_HAND ? serverPlayer.getInventory().selectedSlot : 40;
+                    serverPlayer.networkHandler.sendPacket(new ScreenHandlerSlotUpdateS2CPacket(ScreenHandlerSlotUpdateS2CPacket.UPDATE_PLAYER_INVENTORY_SYNC_ID, 0, slot, stack));
+
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+}

src/main/java/xyz/nucleoid/stimuli/mixin/entity/LeadItemMixin.java

@@ -0,0 +1,51 @@
+package xyz.nucleoid.stimuli.mixin.entity;
+
+import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
+import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
+import com.llamalad7.mixinextras.sugar.Local;
+import net.minecraft.entity.Entity;
+import net.minecraft.entity.Leashable;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.item.LeadItem;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import xyz.nucleoid.stimuli.Stimuli;
+import xyz.nucleoid.stimuli.event.entity.EntityLeashEvent;
+
+import java.util.List;
+import java.util.function.Predicate;
+
+@Mixin(LeadItem.class)
+public class LeadItemMixin {
+    @WrapOperation(
+            method = "attachHeldMobsToBlock",
+            at = @At(
+                value = "INVOKE",
+                target = "Lnet/minecraft/item/LeadItem;collectLeashablesAround(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Ljava/util/function/Predicate;)Ljava/util/List;"
+            )
+    )
+    private static List<Leashable> onLeashAttachToBlock(World world, BlockPos pos, Predicate<Leashable> predicate, Operation<List<Leashable>> original, @Local(argsOnly = true) PlayerEntity player) {
+        return original.call(world, pos, predicate).stream()
+                .filter(leashable -> {
+                    // Leashable is a filtered Entity instance
+                    var entity = (Entity) leashable;
+                    var serverPlayer = (ServerPlayerEntity) player;
+
+                    var events = Stimuli.select();
+
+                    try (var invokers = events.forEntity(serverPlayer)) {
+                        var result = invokers.get(EntityLeashEvent.ATTACH).onAttachLeash(entity, null, pos, serverPlayer, null);
+                        if (result == ActionResult.FAIL) {
+                            return false;
+                        }
+                    }
+
+                    return true;
+                })
+                .toList();
+    }
+}

src/main/java/xyz/nucleoid/stimuli/mixin/entity/LeashKnotEntityMixin.java

@@ -0,0 +1,53 @@
+package xyz.nucleoid.stimuli.mixin.entity;
+
+import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
+import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
+import com.llamalad7.mixinextras.sugar.Local;
+import com.llamalad7.mixinextras.sugar.Share;
+import com.llamalad7.mixinextras.sugar.ref.LocalBooleanRef;
+import net.minecraft.entity.Entity;
+import net.minecraft.entity.Leashable;
+import net.minecraft.entity.decoration.LeashKnotEntity;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.Hand;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import xyz.nucleoid.stimuli.Stimuli;
+import xyz.nucleoid.stimuli.event.entity.EntityLeashEvent;
+
+@Mixin(LeashKnotEntity.class)
+public class LeashKnotEntityMixin {
+    @WrapOperation(
+            method = "interact",
+            at = @At(
+                value = "INVOKE",
+                target = "Lnet/minecraft/entity/Leashable;getLeashHolder()Lnet/minecraft/entity/Entity;",
+                ordinal = 0
+            )
+    )
+    private Entity onLeashAttachToKnot(Leashable leashable, Operation<Entity> original, @Local(argsOnly = true) PlayerEntity player, @Local(argsOnly = true) Hand hand, @Share("attached") LocalBooleanRef attached) {
+        // Leashable is a filtered Entity instance
+        var entity = (Entity) leashable;
+
+        var leashHolder = (Entity) (Object) this;
+        var currentHolder = original.call(leashable);
+
+        // Vanilla reattaches leashes already attached to this knot, so these cases must be filtered out
+        if (leashHolder != currentHolder) {
+            var serverPlayer = (ServerPlayerEntity) player;
+
+            var events = Stimuli.select();
+
+            try (var invokers = events.forEntity(serverPlayer)) {
+                var result = invokers.get(EntityLeashEvent.ATTACH).onAttachLeash(entity, leashHolder, null, serverPlayer, hand);
+                if (result == ActionResult.FAIL) {
+                    return null;
+                }
+            }
+        }
+
+        return currentHolder;
+    }
+}

src/main/resources/stimuli.mixins.json

@@ -16,6 +16,9 @@
         "block.FarmlandBlockMixin",
         "block.FlowerPotBlockMixin",
         "block.TurtleEggBlockMixin",
+        "entity.EntityMixin",
+        "entity.LeadItemMixin",
+        "entity.LeashKnotEntityMixin",
         "entity.LivingEntityMixin",
         "entity.ShearableEntityMixin",
         "entity.ShearsDispenserBehaviorMixin",

src/testmod/java/xyz/nucleoid/stimuli/test/StimuliInitializer.java

@@ -10,6 +10,7 @@
 import org.slf4j.Logger;
 import xyz.nucleoid.stimuli.Stimuli;
 import xyz.nucleoid.stimuli.event.block.FlowerPotModifyEvent;
+import xyz.nucleoid.stimuli.event.entity.EntityLeashEvent;
 import xyz.nucleoid.stimuli.event.entity.EntityShearEvent;
 import xyz.nucleoid.stimuli.event.projectile.ArrowFireEvent;
 import xyz.nucleoid.stimuli.event.world.ExplosionDetonatedEvent;
@@ -58,5 +59,31 @@ public void onInitialize() {
         Stimuli.global().listen(ExplosionDetonatedEvent.EVENT, (explosion, particles) -> {
             server.sendMessage(Text.literal("ExplosionDetonatedEvent: " + explosion.getDestructionType().name()));
         });
+        Stimuli.global().listen(EntityLeashEvent.ATTACH, (entity, leashHolder, leashPos, player, hand) -> {
+            var message = Text.literal("EntityLeashEvent.Attach: ")
+                    .append(entity.getName());
+
+            if (leashHolder != null) {
+                message
+                        .append(" to ")
+                        .append(leashHolder.getName());
+            }
+
+            if (hand != null) {
+                message.append(" with " + hand);
+            }
+
+            if (leashPos != null) {
+                message.append(" at " + leashPos);
+            }
+
+            if (player == null) {
+                server.sendMessage(message);
+            } else {
+                player.sendMessage(message);
+            }
+
+            return result;
+        });
     }
 }