Add functionality in IItemHandler to test if a slot can accept an item (#5033)

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

@@ -19,7 +19,10 @@
 
 package net.minecraftforge.items;
 
+import net.minecraft.inventory.IInventory;
 import net.minecraft.item.ItemStack;
+import net.minecraftforge.fluids.FluidStack;
+import net.minecraftforge.fluids.capability.IFluidHandler;
 
 import javax.annotation.Nonnull;
 
@@ -35,16 +38,18 @@ public interface IItemHandler
     /**
      * Returns the ItemStack in a given slot.
      *
-     * The result's stack size may be greater than the itemstacks max size.
+     * The result's stack size may be greater than the itemstack's max size.
      *
      * If the result is empty, then the slot is empty.
      *
-     * <p/>
+     * <p>
-     * IMPORTANT: This ItemStack MUST NOT be modified. This method is not for
+     * <strong>IMPORTANT:</strong> This ItemStack <em>MUST NOT</em> be modified. This method is not for
-     * altering an inventories contents. Any implementers who are able to detect
+     * altering an inventory's contents. Any implementers who are able to detect
      * modification through this method should throw an exception.
-     * <p/>
+     * </p>
-     * SERIOUSLY: DO NOT MODIFY THE RETURNED ITEMSTACK
+     * <p>
+     * <strong><em>SERIOUSLY: DO NOT MODIFY THE RETURNED ITEMSTACK</em></strong>
+     * </p>
      *
      * @param slot Slot to query
      * @return ItemStack in given slot. Empty Itemstack if the slot is empty.
@@ -53,9 +58,11 @@ public interface IItemHandler
     ItemStack getStackInSlot(int slot);
 
     /**
+     * <p>
      * Inserts an ItemStack into the given slot and return the remainder.
-     * The ItemStack should not be modified in this function!
+     * The ItemStack <em>should not</em> be modified in this function!
-     * Note: This behaviour is subtly different from IFluidHandlers.fill()
+     * </p>
+     * Note: This behaviour is subtly different from {@link IFluidHandler#fill(FluidStack, boolean)}
      *
      * @param slot     Slot to insert into.
      * @param stack    ItemStack to insert. This must not be modified by the item handler.
@@ -69,11 +76,13 @@ public interface IItemHandler
 
     /**
      * Extracts an ItemStack from the given slot.
+     * <p>
      * The returned value must be empty if nothing is extracted,
-     * otherwise it's stack size must less than than amount and {@link ItemStack#getMaxStackSize()}.
+     * otherwise its stack size must be less than or equal to {@code amount} and {@link ItemStack#getMaxStackSize()}.
+     * </p>
      *
      * @param slot     Slot to extract from.
-     * @param amount   Amount to extract (may be greater than the current stacks max limit)
+     * @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.
@@ -88,4 +97,26 @@ public interface IItemHandler
      * @return     The maximum stack size allowed in the slot.
      */
     int getSlotLimit(int slot);
+
+    /**
+     * <p>
+     * This function re-implements the vanilla function {@link IInventory#isItemValidForSlot(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.
+     */
+    //todo Make non-default and/or replace in 1.13
+    default boolean isItemValid(int slot, @Nonnull ItemStack stack) { return true; }
 }

src/main/java/net/minecraftforge/items/ItemStackHandler.java

@@ -164,6 +164,12 @@ public class ItemStackHandler implements IItemHandler, IItemHandlerModifiable, I
         return Math.min(getSlotLimit(slot), stack.getMaxStackSize());
     }
 
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        return true;
+    }
+
     @Override
     public NBTTagCompound serializeNBT()
     {

src/main/java/net/minecraftforge/items/SlotItemHandler.java

@@ -46,24 +46,7 @@ public class SlotItemHandler extends Slot
         if (stack.isEmpty())
             return false;
 
-        IItemHandler handler = this.getItemHandler();
+        return itemHandler.isItemValid(index, stack);
-        ItemStack remainder;
-        if (handler instanceof IItemHandlerModifiable)
-        {
-            IItemHandlerModifiable handlerModifiable = (IItemHandlerModifiable) handler;
-            ItemStack currentStack = handlerModifiable.getStackInSlot(index);
-
-            handlerModifiable.setStackInSlot(index, ItemStack.EMPTY);
-
-            remainder = handlerModifiable.insertItem(index, stack, true);
-
-            handlerModifiable.setStackInSlot(index, currentStack);
-        }
-        else
-        {
-            remainder = handler.insertItem(index, stack, true);
-        }
-        return remainder.isEmpty() || remainder.getCount() < stack.getCount();
     }
 
     @Override

src/main/java/net/minecraftforge/items/VanillaDoubleChestItemHandler.java

@@ -187,6 +187,19 @@ public class VanillaDoubleChestItemHandler extends WeakReference<TileEntityChest
         return getChest(accessingUpperChest).getInventoryStackLimit();
     }
 
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        boolean accessingUpperChest = slot < 27;
+        int targetSlot = accessingUpperChest ? slot : slot - 27;
+        TileEntityChest chest = getChest(accessingUpperChest);
+        if (chest != null)
+        {
+            return chest.getSingleChestHandler().isItemValid(targetSlot, stack);
+        }
+        return true;
+    }
+
     @Override
     public boolean equals(Object o)
     {

src/main/java/net/minecraftforge/items/wrapper/CombinedInvWrapper.java

@@ -132,4 +132,13 @@ public class CombinedInvWrapper implements IItemHandlerModifiable
         int localSlot = getSlotFromIndex(slot, index);
         return handler.getSlotLimit(localSlot);
     }
+
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        int index = getIndexForSlot(slot);
+        IItemHandlerModifiable handler = getHandlerFromIndex(index);
+        int localSlot = getSlotFromIndex(slot, index);
+        return handler.isItemValid(localSlot, stack);
+    }
 }

src/main/java/net/minecraftforge/items/wrapper/EmptyHandler.java

@@ -67,4 +67,10 @@ public class EmptyHandler implements IItemHandlerModifiable
     {
         return 0;
     }
+
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        return false;
+    }
 }

src/main/java/net/minecraftforge/items/wrapper/EntityEquipmentInvWrapper.java

@@ -179,6 +179,12 @@ public abstract class EntityEquipmentInvWrapper implements IItemHandlerModifiabl
         entity.setItemStackToSlot(equipmentSlot, stack);
     }
 
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        return IItemHandlerModifiable.super.isItemValid(slot, stack);
+    }
+
     protected EntityEquipmentSlot validateSlotIndex(final int slot)
     {
         if (slot < 0 || slot >= slots.size())

src/main/java/net/minecraftforge/items/wrapper/InvWrapper.java

@@ -204,6 +204,12 @@ public class InvWrapper implements IItemHandlerModifiable
         return getInv().getInventoryStackLimit();
     }
 
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        return getInv().isItemValidForSlot(slot, stack);
+    }
+
     public IInventory getInv()
     {
         return inv;

src/main/java/net/minecraftforge/items/wrapper/RangedWrapper.java

@@ -105,6 +105,17 @@ public class RangedWrapper implements IItemHandlerModifiable {
         return 0;
     }
 
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        if (checkSlot(slot))
+        {
+            return compose.isItemValid(slot + minSlot, stack);
+        }
+
+        return false;
+    }
+
     private boolean checkSlot(int localSlot)
     {
         return localSlot + minSlot < maxSlot;

src/main/java/net/minecraftforge/items/wrapper/SidedInvWrapper.java

@@ -230,4 +230,10 @@ public class SidedInvWrapper implements IItemHandlerModifiable
     {
         return inv.getInventoryStackLimit();
     }
+
+    @Override
+    public boolean isItemValid(int slot, @Nonnull ItemStack stack)
+    {
+        return inv.isItemValidForSlot(slot, stack);
+    }
 }