/*
 * This file is part of Applied Energistics 2.
 * Copyright (c) 2013 - 2014, AlgorithmX2, All rights reserved.
 *
 * Applied Energistics 2 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Applied Energistics 2 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 Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
 */

package appeng.util.item;

import java.util.Objects;

import com.google.common.base.Preconditions;

import net.minecraft.item.ItemStack;


final class AESharedItemStack
{

	private final ItemStack itemStack;
	private final int itemDamage;
	private final int hashCode;

	public AESharedItemStack( final ItemStack itemStack )
	{
		this( itemStack, itemStack.getItemDamage() );
	}

	/**
	 * A constructor to explicitly set the damage value and not fetch it from the {@link ItemStack}
	 *
	 * @param itemStack The {@link ItemStack} to filter
	 * @param damage    The damage of the item
	 */
	private AESharedItemStack( ItemStack itemStack, int damage )
	{
		this.itemStack = itemStack;
		this.itemDamage = damage;

		// Ensure this is always called last.
		this.hashCode = this.makeHashCode();
	}

	ItemStack getDefinition()
	{
		return this.itemStack;
	}

	int getItemDamage()
	{
		return this.itemDamage;
	}

	@Override
	public int hashCode()
	{
		return this.hashCode;
	}

	@Override
	public boolean equals( final Object obj )
	{
		if( this == obj )
		{
			return true;
		}
		if( !( obj instanceof AESharedItemStack ) )
		{
			return false;
		}

		final AESharedItemStack other = (AESharedItemStack) obj;
		Preconditions.checkState( this.itemStack.getCount() == 1, "ItemStack#getCount() has to be 1" );
		Preconditions.checkArgument( other.getDefinition().getCount() == 1, "ItemStack#getCount() has to be 1" );

		if( this.itemStack == other.itemStack )
		{
			return true;
		}
		return ItemStack.areItemStacksEqual( this.itemStack, other.itemStack );
	}

	private int makeHashCode()
	{
		return Objects.hash( this.itemStack.getItem(), this.itemDamage, this.itemStack.hasTagCompound() ? this.itemStack.getTagCompound() : 0 );
	}

}