Fix item pickup events (#193)

Author: cittyinthecloud

patchwork-events-entity/src/main/java/net/patchworkmc/impl/event/entity/PlayerEvents.java

@@ -61,7 +61,7 @@ public static void firePlayerSmeltedEvent(PlayerEntity player, ItemStack smelted
 
 	/**
 	 *
-	 * @return -1 if the event was cancelled, 0 if the event was denied, 1 if the event was accepted
+	 * @return -1 if the event was canceled, 0 if the event was denied or had no result set, and 1 if the event was allowed
 	 */
 	public static int onItemPickup(PlayerEntity player, ItemEntity entityItem) {
 		Event event = new EntityItemPickupEvent(player, entityItem);

patchwork-events-entity/src/main/java/net/patchworkmc/mixin/event/entity/MixinItemEntity.java

@@ -20,6 +20,8 @@
 package net.patchworkmc.mixin.event.entity;
 
 import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.At.Shift;
 import org.spongepowered.asm.mixin.injection.Inject;
@@ -35,34 +37,73 @@
 
 @Mixin(ItemEntity.class)
 public abstract class MixinItemEntity {
-	@Inject(method = "onPlayerCollision",
-			at = @At(
-					value = "INVOKE",
-					shift = Shift.BEFORE,
-					ordinal = 0,
-					target = "net/minecraft/item/ItemStack.isEmpty()Z"
-					)
-	)
-	private void onPlayerPickUpItemEntity(PlayerEntity player, CallbackInfo ci) {
-		ItemEntity me = (ItemEntity) (Object) this;
-		PlayerEvents.firePlayerItemPickupEvent(player, me, me.getStack().copy());
-	}
+	@Shadow
+	public abstract ItemStack getStack();
+
+	@Shadow
+	private int pickupDelay;
 
-	int eventResult;
+	@Unique
+	private int eventResult;
+
+	@Unique
+	private int preEventStackCount;
+
+	@Unique
+	private ItemStack copy;
+
+	// Forge just returns early from the event if the item has pickup delay, presumably
+	// to keep it's events from being called. To maintain compatibility with potential
+	// Fabric mods that might want to still have this method called from items that can't
+	// be picked up yet, we'll just skip calling the events.
+	@Unique
+	private boolean hasPickupDelay;
+
+	@Inject(method = "onPlayerCollision", at = @At("HEAD"), cancellable = true)
+	private void patchwork_checkForPickupDelay(PlayerEntity player, CallbackInfo ci) {
+		hasPickupDelay = this.pickupDelay > 0;
+	}
 
 	@Inject(method = "onPlayerCollision",
-			at = @At(value = "INVOKE", target = "Lnet/minecraft/item/ItemStack;getCount()I"),
-			cancellable = true
+					at = @At(value = "INVOKE", target = "Lnet/minecraft/item/ItemStack;getCount()I"),
+					cancellable = true
 	)
-	void patchwork_fireItemPickupEvent(PlayerEntity player, CallbackInfo ci) {
-		eventResult = PlayerEvents.onItemPickup(player, (ItemEntity) (Object) this);
-		if (eventResult != 1) ci.cancel();
+	private void patchwork_fireItemPickupEvent(PlayerEntity player, CallbackInfo ci) {
+		if (!hasPickupDelay) {
+			preEventStackCount = getStack().getCount();
+			eventResult = PlayerEvents.onItemPickup(player, (ItemEntity) (Object) this);
+
+			if (eventResult < 0) {
+				ci.cancel();
+			}
+
+			copy = getStack().copy();
+		}
 	}
 
 	@Redirect(method = "onPlayerCollision",
-			at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/player/PlayerInventory;insertStack(Lnet/minecraft/item/ItemStack;)Z")
+					at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/player/PlayerInventory;insertStack(Lnet/minecraft/item/ItemStack;)Z")
+	)
+	private boolean patchwork_giveItemConditions(PlayerInventory playerInventory, ItemStack stack) {
+		if (hasPickupDelay) {
+			return playerInventory.insertStack(stack); // Haven't processed the event because Forge wouldn't.
+		} else {
+			return eventResult == 1 || preEventStackCount <= 0 || playerInventory.insertStack(stack);
+		}
+	}
+
+	@Inject(method = "onPlayerCollision",
+					at = @At(
+									value = "INVOKE",
+									shift = Shift.BEFORE,
+									ordinal = 0,
+									target = "net/minecraft/item/ItemStack.isEmpty()Z"
+					)
 	)
-	boolean patchwork_skipIfEventNotAllowed(PlayerInventory playerInventory, ItemStack stack) {
-		return eventResult == 1 || playerInventory.insertStack(stack);
+	private void patchwork_firePlayerItemPickupEvent(PlayerEntity player, CallbackInfo ci) {
+		if (!hasPickupDelay) {
+			copy.setCount(copy.getCount() - getStack().getCount());
+			PlayerEvents.firePlayerItemPickupEvent(player, (ItemEntity) (Object) this, copy);
+		}
 	}
 }