BloodMagic/src/main/java/WayofTime/bloodmagic/compress/BaseCompressionHandler.java

package WayofTime.bloodmagic.compress;

import net.minecraft.item.ItemStack;
import net.minecraft.world.World;

public class BaseCompressionHandler extends CompressionHandler {
    private final ItemStack required;
    private final ItemStack result;
    private final int leftover;

    public BaseCompressionHandler(ItemStack requested, ItemStack result, int leftover) {
        super();
        this.required = requested;
        this.result = result;
        this.leftover = leftover;
    }

    public ItemStack getResultStack() {
        return this.result.copy();
    }

    public ItemStack getRequiredStack() {
        return this.required.copy();
    }

    @Override
    public ItemStack compressInventory(ItemStack[] inv, World world) {
        int remaining = this.getRemainingNeeded(inv);
        if (remaining <= 0) {
            this.drainInventory(inv);
            return this.getResultStack();
        }

        return ItemStack.EMPTY;
    }

    public int getRemainingNeeded(ItemStack[] inv) {
        return iterateThroughInventory(inv, false);
    }

    public int drainInventory(ItemStack[] inv) {
        return iterateThroughInventory(inv, true);
    }

    public int iterateThroughInventory(ItemStack[] inv, boolean doDrain) {
        int needed = this.required.getCount();
        int kept = this.getLeftover();
        int i = -1;

        for (ItemStack invStack : inv) {
            i++;

            if (invStack == null) {
                continue;
            }

            if (invStack.isItemEqual(this.required) && (invStack.getTagCompound() == null ? this.required.getTagCompound() == null : invStack.getTagCompound().equals(this.required.getTagCompound()))) {
                int stackSize = invStack.getCount();
                int used = 0;
                if (kept > 0) {
                    int remainingFromStack = Math.max(stackSize - kept, 0);
                    used += stackSize - remainingFromStack;
                }

                kept -= used;

                if (kept <= 0 && needed > 0) {
                    int remainingFromStack = Math.max(stackSize - used - needed, 0);
                    if (doDrain) {
                        invStack.setCount(remainingFromStack + used);
                        if (invStack.isEmpty()) {
                            inv[i] = ItemStack.EMPTY;
                        }
                    }

                    needed -= (stackSize - used - remainingFromStack);
                }

                if (needed <= 0) {
                    return 0;
                }
            }
        }

        return needed;
    }

    public int getLeftover() {
        return this.leftover;
    }
}