IItemHandler support (#142)

* IItemHandler support

* Remove a sneaky debug print

* Apparently this can cause a memory leak, TIL

* Update patchwork-items/src/main/java/net/minecraftforge/items/ItemHandlerHelper.java

Co-authored-by: Glitch <glitchieproductionsofficial@gmail.com>

Author: cittyinthecloud

patchwork-items/build.gradle

@@ -0,0 +1,6 @@
+archivesBaseName = "patchwork-items"
+version = getSubprojectVersion(project, "0.1.0")
+
+dependencies {
+	compile project(path: ':patchwork-capabilities', configuration: 'dev')
+}

patchwork-items/src/main/java/net/minecraftforge/items/CapabilityItemHandler.java

@@ -0,0 +1,79 @@
+/*
+ * Minecraft Forge, Patchwork Project
+ * Copyright (c) 2016-2020, 2019-2020
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.items;
+
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.CapabilityManager;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.Tag;
+import net.minecraft.util.math.Direction;
+
+import net.patchworkmc.api.capability.CapabilityRegisteredCallback;
+
+public class CapabilityItemHandler {
+	public static Capability<IItemHandler> ITEM_HANDLER_CAPABILITY = null;
+
+	public static void register() {
+		CapabilityRegisteredCallback.event(IItemHandler.class).register(cap -> ITEM_HANDLER_CAPABILITY = cap);
+
+		CapabilityManager.INSTANCE.register(IItemHandler.class, new Capability.IStorage<IItemHandler>() {
+			@Override
+			public Tag writeNBT(Capability<IItemHandler> capability, IItemHandler instance, Direction side) {
+				ListTag nbtTagList = new ListTag();
+				int size = instance.getSlots();
+
+				for (int i = 0; i < size; i++) {
+					ItemStack stack = instance.getStackInSlot(i);
+
+					if (!stack.isEmpty()) {
+						CompoundTag itemTag = new CompoundTag();
+						itemTag.putInt("Slot", i);
+						stack.toTag(itemTag);
+						nbtTagList.add(itemTag);
+					}
+				}
+
+				return nbtTagList;
+			}
+
+			@Override
+			public void readNBT(Capability<IItemHandler> capability, IItemHandler instance, Direction side, Tag base) {
+				if (!(instance instanceof IItemHandlerModifiable)) {
+					throw new RuntimeException("IItemHandler instance does not implement IItemHandlerModifiable");
+				}
+
+				IItemHandlerModifiable itemHandlerModifiable = (IItemHandlerModifiable) instance;
+				ListTag tagList = (ListTag) base;
+
+				for (int i = 0; i < tagList.size(); i++) {
+					CompoundTag itemTags = tagList.getCompound(i);
+					int j = itemTags.getInt("Slot");
+
+					if (j >= 0 && j < instance.getSlots()) {
+						itemHandlerModifiable.setStackInSlot(j, ItemStack.fromTag(itemTags));
+					}
+				}
+			}
+		}, ItemStackHandler::new);
+	}
+}

patchwork-items/src/main/java/net/minecraftforge/items/IItemHandler.java

@@ -0,0 +1,112 @@
+/*
+ * Minecraft Forge, Patchwork Project
+ * Copyright (c) 2016-2020, 2019-2020
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.items;
+
+import javax.annotation.Nonnull;
+
+import net.minecraft.inventory.Inventory;
+import net.minecraft.item.ItemStack;
+
+public interface IItemHandler {
+	/**
+	 * Returns the number of slots available.
+	 *
+	 * @return The number of slots available
+	 */
+	int getSlots();
+
+	/**
+	 * Returns the ItemStack in a given slot.
+	 *
+	 * <p>The result's stack size may be greater than the itemstack's max size.
+	 *
+	 * <p>If the result is empty, then the slot is empty.
+	 *
+	 * <p><strong>IMPORTANT:</strong> This ItemStack <em>MUST NOT</em> be modified. This method is not for
+	 * altering an inventory's contents. Any implementers who are able to detect
+	 * modification through this method should throw an exception.
+	 *
+	 * <p><strong><em>SERIOUSLY: DO NOT MODIFY THE RETURNED ITEMSTACK</em></strong>
+	 *
+	 * @param slot Slot to query
+	 * @return ItemStack in given slot. Empty Itemstack if the slot is empty.
+	 */
+	@Nonnull
+	ItemStack getStackInSlot(int slot);
+
+	/**
+	 * <p>Inserts an ItemStack into the given slot and return the remainder.
+	 * The ItemStack <em>should not</em> be modified in this function!
+	 * </p>
+	 * Note: This behaviour is subtly different from net.minecraftforge.fluids.capability.IFluidHandler#fill(net.minecraftforge.fluids.FluidStack, boolean)
+	 *
+	 * @param slot     Slot to insert into.
+	 * @param stack    ItemStack to insert. This must not be modified by the item handler.
+	 * @param simulate If true, the insertion is only simulated
+	 * @return The remaining ItemStack that was not inserted (if the entire stack is accepted, then return an empty ItemStack).
+	 * May be the same as the input ItemStack if unchanged, otherwise a new ItemStack.
+	 * The returned ItemStack can be safely modified after.
+	 */
+	@Nonnull
+	ItemStack insertItem(int slot, @Nonnull ItemStack stack, boolean simulate);
+
+	/**
+	 * Extracts an ItemStack from the given slot.
+	 * <p>The returned value must be empty if nothing is extracted,
+	 * otherwise its stack size must be less than or equal to {@code amount} and {@link ItemStack#getMaxCount()} ()}.
+	 * </p>
+	 *
+	 * @param slot     Slot to extract from.
+	 * @param amount   Amount to extract (may be greater than the current stack's max limit)
+	 * @param simulate If true, the extraction is only simulated
+	 * @return ItemStack extracted from the slot, must be empty if nothing can be extracted.
+	 * The returned ItemStack can be safely modified after, so item handlers should return a new or copied stack.
+	 */
+	@Nonnull
+	ItemStack extractItem(int slot, int amount, boolean simulate);
+
+	/**
+	 * Retrieves the maximum stack size allowed to exist in the given slot.
+	 *
+	 * @param slot Slot to query.
+	 * @return The maximum stack size allowed in the slot.
+	 */
+	int getSlotLimit(int slot);
+
+	/**
+	 * <p>This function re-implements the vanilla function {@link Inventory#isValidInvStack(int, ItemStack)}.
+	 * It should be used instead of simulated insertions in cases where the contents and state of the inventory are
+	 * irrelevant, mainly for the purpose of automation and logic (for instance, testing if a minecart can wait
+	 * to deposit its items into a full inventory, or if the items in the minecart can never be placed into the
+	 * inventory and should move on).
+	 * </p>
+	 * <ul>
+	 * <li>isItemValid is false when insertion of the item is never valid.</li>
+	 * <li>When isItemValid is true, no assumptions can be made and insertion must be simulated case-by-case.</li>
+	 * <li>The actual items in the inventory, its fullness, or any other state are <strong>not</strong> considered by isItemValid.</li>
+	 * </ul>
+	 *
+	 * @param slot  Slot to query for validity
+	 * @param stack Stack to test with for validity
+	 * @return true if the slot can insert the ItemStack, not considering the current state of the inventory.
+	 * false if the slot can never insert the ItemStack in any situation.
+	 */
+	boolean isItemValid(int slot, @Nonnull ItemStack stack);
+}

patchwork-items/src/main/java/net/minecraftforge/items/IItemHandlerModifiable.java

@@ -0,0 +1,39 @@
+/*
+ * Minecraft Forge, Patchwork Project
+ * Copyright (c) 2016-2020, 2019-2020
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.items;
+
+import javax.annotation.Nonnull;
+
+import net.minecraft.item.ItemStack;
+
+public interface IItemHandlerModifiable extends IItemHandler {
+	/**
+	 * Overrides the stack in the given slot. This method is used by the
+	 * standard Forge helper methods and classes. It is not intended for
+	 * general use by other mods, and the handler may throw an error if it
+	 * is called unexpectedly.
+	 *
+	 * @param slot  Slot to modify
+	 * @param stack ItemStack to set slot to (may be empty).
+	 * @throws RuntimeException if the handler is called in a way that the handler
+	 *                          was not expecting.
+	 */
+	void setStackInSlot(int slot, @Nonnull ItemStack stack);
+}