try fix #13

src/api/java/jaquadro/storagedrawers/IItemRepository.java

@@ -0,0 +1,143 @@
+package com.jaquadro.minecraft.storagedrawers.api.capabilities;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.NonNullList;
+
+import javax.annotation.Nonnull;
+import java.util.function.Predicate;
+
+/**
+ * An interface for treating an inventory as a slotless, central repository of items.
+ *
+ * For all operations that accept a predicate, if a predicate is supplied, a stored ItemStack must pass the predicate
+ * in order to be considered for the given operation.
+ *
+ * An IItemRepository implementation MAY relax or eliminate its own internal tests when a predicate is supplied.  If
+ * the predicate is derived from DefaultPredicate, then the implementation MUST apply any tests it would have applied
+ * had no predicate been provided at all, in addition to testing the predicate itself.
+ */
+public interface IItemRepository
+{
+    /**
+     * Gets a list of all items in the inventory.  The same item may appear multiple times with varying counts.
+
+     * @return A list of zero or more items in the inventory.
+     */
+    @Nonnull
+    NonNullList<ItemRecord> getAllItems ();
+
+    /**
+     * Inserts an ItemStack into the inventory and returns the remainder.
+     *
+     * @param stack     ItemStack to insert.
+     * @param simulate  If true, the insertion is only simulated
+     * @param predicate See interface notes about predicates.  Passing null specifies default matching.
+     * @return The remaining ItemStack that was not inserted.  If the entire stack was accepted, returns
+     * ItemStack.EMPTY instead.
+     */
+    @Nonnull
+    ItemStack insertItem (@Nonnull ItemStack stack, boolean simulate, Predicate<ItemStack> predicate);
+
+    @Nonnull
+    default ItemStack insertItem (@Nonnull ItemStack stack, boolean simulate) {
+        return insertItem(stack, simulate, null);
+    }
+
+    /**
+     * Tries to extract the given ItemStack from the inventory.  The returned value will be a matching ItemStack
+     * with a stack size equal to or less than amount, or the empty ItemStack if the item could not be found at all.
+     * The returned stack size may exceed the ItemStack's getMaxStackSize() value.
+
+     * @param stack     The item to extract.  The stack size is ignored.
+     * @param amount    Amount to extract (may be greater than the stacks max limit)
+     * @param simulate  If true, the extraction is only simulated
+     * @param predicate See interface notes about predicates.  Passing null specifies default matching.
+     * @return ItemStack extracted from the inventory, or ItemStack.EMPTY if nothing could be extracted.
+     */
+    @Nonnull
+    ItemStack extractItem (@Nonnull ItemStack stack, int amount, boolean simulate, Predicate<ItemStack> predicate);
+
+    @Nonnull
+    default ItemStack extractItem (@Nonnull ItemStack stack, int amount, boolean simulate) {
+        return extractItem(stack, amount, simulate, null);
+    }
+
+    /**
+     * Gets the number of items matching the given ItemStack stored by the inventory.
+
+     * @param stack     ItemStack to query.
+     * @param predicate See interface notes about predicates.  Passing null specifies default matching.
+     * @return The number of stored matching items.  A value of Integer.MAX_VALUE may indicate an infinite item source.
+     */
+    default int getStoredItemCount (@Nonnull ItemStack stack, Predicate<ItemStack> predicate) {
+        ItemStack amount = extractItem(stack, Integer.MAX_VALUE, true, predicate);
+        return amount.getCount();
+    }
+
+    default int getStoredItemCount (@Nonnull ItemStack stack) {
+        return getStoredItemCount(stack, null);
+    }
+
+    /**
+     * Gets the number items matching the given ItemStack that additionally still be stored by the inventory.
+     * Remaining capacity may include space that is internally empty or unassigned to any given item.
+     *
+     * @param stack     ItemStack to query.
+     * @param predicate See interface notes about predicates.  Passing null specifies default matching.
+     * @return The available remaining space for matching items.
+     */
+    default int getRemainingItemCapacity (@Nonnull ItemStack stack, Predicate<ItemStack> predicate) {
+        stack = stack.copy();
+        stack.setCount(Integer.MAX_VALUE);
+        ItemStack remainder = insertItem(stack, true, predicate);
+        return Integer.MAX_VALUE - remainder.getCount();
+    }
+
+    default int getRemainingItemCapacity (@Nonnull ItemStack stack) {
+        return getRemainingItemCapacity(stack, null);
+    }
+
+    /**
+     * Gets the total inventory capacity for items matching the given ItemStack.
+     * Total capacity may include space that is internally empty or unassigned to any given item.
+     *
+     * @param stack     ItemStack to query.
+     * @param predicate See interface notes about predicates.  Passing null specifies default matching.
+     * @return The total capacity for matching items.
+     */
+    default int getItemCapacity (@Nonnull ItemStack stack, Predicate<ItemStack> predicate) {
+        long capacity = getStoredItemCount(stack, predicate) + getRemainingItemCapacity(stack, predicate);
+        if (capacity > Integer.MAX_VALUE)
+            return Integer.MAX_VALUE;
+        return (int)capacity;
+    }
+
+    default int getItemCapacity (@Nonnull ItemStack stack) {
+        return getItemCapacity(stack, null);
+    }
+
+    /**
+     * An item record representing an item and the amount stored.
+     *
+     * The ItemStack held by itemPrototype always reports a stack size of 1.
+     * IT IS IMPORTANT THAT YOU NEVER MODIFY itemPrototype.
+     */
+    class ItemRecord
+    {
+        @Nonnull
+        public final ItemStack itemPrototype;
+        public final int count;
+
+        public ItemRecord (@Nonnull ItemStack itemPrototype, int count) {
+            this.itemPrototype = itemPrototype;
+            this.count = count;
+        }
+    }
+
+    /**
+     * A variant of the standard Predicate interface that when passed to IItemRepository functions, will ask the
+     * internal default predicate to be tested in addition to the custom predicate.  An IItemRepository function
+     * may choose to enforce its own predicate regardless.
+     */
+    interface DefaultPredicate<T> extends Predicate<T> { }
+}