package mekanism.api.gas;

import net.minecraft.nbt.NBTTagCompound;

/**
 * An optional way of managing and/or storing gasses. Would be very useful in TileEntity and Entity gas storage.
 * @author aidancbrady
 *
 */
public class GasTank
{
	public GasStack stored;
	
	private int maxGas;
	
	private GasTank() {}
	
	/**
	 * Creates a tank with a defined capacity.
	 * @param max - the maximum amount of gas this GasTank can hold
	 */
	public GasTank(int max)
	{
		maxGas = max;
	}
	
	/**
	 * Sets this tank's GasStack value to a new value. Will cap the amount to this GasTank's capacity.
	 * @param stack - value to set this tank's GasStack value to
	 */
	public void setGas(GasStack stack)
	{
		stored = stack;
		
		if(stored != null)
		{
			stored.amount = Math.min(getMaxGas(), stored.amount);
		}
	}
	
	/**
	 * Draws a specified amount of gas out of this tank.
	 * @param amount - amount to draw
	 * @param doDraw - if the gas should actually be removed from this tank
	 * @return gas taken from this GasTank as a GasStack value
	 */
	public GasStack draw(int amount, boolean doDraw)
	{
		if(stored == null || amount <= 0)
		{
			return null;
		}
		
		GasStack ret = new GasStack(getGas().getGas(), Math.min(getStored(), amount));
		
		if(ret.amount > 0)
		{
			if(doDraw)
			{
				stored.amount -= ret.amount;
				
				if(stored.amount <= 0)
				{
					stored = null;
				}
			}
			
			return ret;
		}
		
		return null;
	}
	
	/**
	 * Adds a specified amount of gas to this tank.
	 * @param amount - the GasStack for this tank to receive
	 * @param doReceive - if the gas should actually be added to this tank
	 * @return the amount of gas accepted by this tank
	 */
	public int receive(GasStack amount, boolean doReceive)
	{
		if(amount == null || (stored != null && stored.amount == getMaxGas()))
		{
			return 0;
		}
		
		int toFill = Math.min(getMaxGas()-getStored(), amount.amount);
		
		if(doReceive)
		{
			if(stored == null)
			{
				stored = amount;
			}
			else {
				stored.amount = Math.min(getMaxGas(), getStored()+amount.amount);
			}
		}
		
		return toFill;
	}
	
	/**
	 * If this GasTank can receive the specified type of gas. Will return false if this tank does not need anymore gas.
	 * @param gas - gas to check
	 * @return if this GasTank can accept the defined gas
	 */
	public boolean canReceive(Gas gas)
	{
		if(getNeeded() == 0 || stored != null && (gas != null && gas != stored.getGas()))
		{
			return false;
		}
		
		return true;
	}
	
	/**
	 * If this GasTank can be drawn of the specified type of gas. Will return false if this tank does not contain any gas.
	 * @param gas - gas to check
	 * @return if this GasTank can be drawn of the defined gas
	 */
	public boolean canDraw(Gas gas)
	{
		if(stored == null || (gas != null && gas != stored.getGas()))
		{
			return false;
		}
		
		return true;
	}
	
	/**
	 * Gets the amount of gas needed by this GasTank.
	 * @return
	 */
	public int getNeeded()
	{
		return getMaxGas()-getStored();
	}
	
	/**
	 * Gets the maximum amount of gas this tank can hold.
	 * @return - max gas
	 */
	public int getMaxGas()
	{
		return maxGas;
	}
	
	/**
	 * Gets the GasStack held by this GasTank.
	 * @return - GasStakc held by this tank
	 */
	public GasStack getGas()
	{
		return stored;
	}
	
	/**
	 * Gets the amount of gas stored by this GasTank.
	 * @return amount of gas stored
	 */
	public int getStored()
	{
		return stored != null ? stored.amount : 0;
	}
	
	/**
	 * Writes this tank to a defined tag compound.
	 * @param nbtTags - tag compound to write to
	 * @return tag compound with this tank's data
	 */
	public NBTTagCompound write(NBTTagCompound nbtTags)
	{
		if(stored != null)
		{
			nbtTags.setCompoundTag("stored", stored.write(new NBTTagCompound()));
		}
		
		nbtTags.setInteger("maxGas", maxGas);
		
		return nbtTags;
	}
	
	/**
	 * Reads this tank's data from a defined tag compound.
	 * @param nbtTags - tag compound to read from
	 */
	public void read(NBTTagCompound nbtTags)
	{
		if(nbtTags.hasKey("stored"))
		{
			stored = GasStack.readFromNBT(nbtTags.getCompoundTag("stored"));
		}
		
		maxGas = nbtTags.getInteger("maxGas");
	}
	
	/**
	 * Returns the tank stored in the defined tag compound, or null if it doesn't exist.
	 * @param nbtTags - tag compound to read from
	 * @return tank stored in the tag compound
	 */
	public static GasTank readFromNBT(NBTTagCompound nbtTags)
	{
		if(nbtTags == null || nbtTags.hasNoTags())
		{
			return null;
		}
		
		GasTank tank = new GasTank();
		tank.read(nbtTags);
		
		return tank;
	}
}