redpower/src/main/java/com/eloraam/redpower/base/RecipeBag.java

package com.eloraam.redpower.base;

import com.eloraam.redpower.RedPowerBase;
import net.minecraft.init.Items;
import net.minecraft.inventory.InventoryCrafting;
import net.minecraft.item.ItemStack;
import net.minecraft.item.crafting.IRecipe;
import net.minecraft.world.World;

public class RecipeBag implements IRecipe {
   public int getRecipeSize() {
      return 2;
   }

   public ItemStack getRecipeOutput() {
      return new ItemStack(RedPowerBase.itemBag, 1, 0);
   }

   private ItemStack findResult(InventoryCrafting inv) {
      ItemStack bag = null;
      int color = -1;

      for(int i = 0; i < 3; ++i) {
         for(int j = 0; j < 3; ++j) {
            ItemStack ist = inv.getStackInRowAndColumn(i, j);
            if (ist != null) {
               if (ist.getItem() instanceof ItemBag) {
                  if (bag != null) {
                     return null;
                  }

                  bag = ist;
               } else {
                  if (ist.getItem() != Items.dye) {
                     return null;
                  }

                  if (color >= 0) {
                     return null;
                  }

                  color = 15 - ist.getItemDamage();
               }
            }
         }
      }

      if (bag == null || color < 0) {
         return null;
      } else if (bag.getItemDamage() == color) {
         return null;
      } else {
         bag = bag.copy();
         bag.setItemDamage(color);
         return bag;
      }
   }

   public ItemStack getCraftingResult(InventoryCrafting inv) {
      return this.findResult(inv).copy();
   }

   public boolean matches(InventoryCrafting inv, World world) {
      return this.findResult(inv) != null;
   }
}