package org.apidesign.apifest08.currency;

import java.io.Serializable;

import java.math.BigDecimal;

import java.math.RoundingMode;

import java.util.Currency;

/**

 * Default {@link Convertor} implementation. Exchange rate is stored as equivalents. It means if we have USD to CZK convertor and USD1 = CZK17 

 * we store 1 in sourceEquivalent and 17 in destinationEquivalent. This class is immutable.

 * @author lukas

 *

 */

class DefaultConvertor implements ExtendedConvertor, Serializable {

	private static final long serialVersionUID = 6660014633685135034L;

	/**

	 * Equivalent in source currency.

	 */

	private final BigDecimal sourceEquivalent;

	/**

	 * Equivalent in destination currency.

	 */

	private final BigDecimal destinationEquivalent;

	private final Currency sourceCurrency;

	private final Currency destinationCurrency;

	public DefaultConvertor(Money sourceEquivalent, Money destinationEquivalent) {

		super();

		if (BigDecimal.ZERO.compareTo(sourceEquivalent.getAmount())==0)

		{

			throw new IllegalArgumentException("Source equivalent amount can not be 0.");

		}

		if (BigDecimal.ZERO.compareTo(destinationEquivalent.getAmount())==0)

		{

			throw new IllegalArgumentException("Destination equivalent amount can not be 0.");

		}

		this.sourceEquivalent = sourceEquivalent.getAmount();

		this.destinationEquivalent = destinationEquivalent.getAmount();

		this.sourceCurrency = sourceEquivalent.getCurrency();

		this.destinationCurrency = destinationEquivalent.getCurrency();

	}

	public Money convert(Money amount, Currency destinationCurrency) {

		if (amount==null)

		{

			throw new NullPointerException("Money is null");

		}

		if (destinationCurrency==null)

		{

			throw new NullPointerException("destionationCurrency is null");

		}

		if (!amount.getCurrency().equals(getSourceCurrency()))

		{

			throw new IllegalArgumentException("Can not convert from "+amount.getCurrency()+". Converts between "+getSourceCurrency()+" and "+getDestinationCurrency());

		}

		if (!getDestinationCurrency().equals(destinationCurrency))

		{

			throw new IllegalArgumentException("Can not convert to "+destinationCurrency+". Converts between "+getSourceCurrency()+" and "+getDestinationCurrency());

		}

		BigDecimal sourceAmount = amount.getAmount();

		BigDecimal destinationAmount = sourceAmount.multiply(destinationEquivalent).divide(sourceEquivalent, 2, RoundingMode.HALF_UP);

		return new MoneyImpl(destinationAmount, getDestinationCurrency());

	}

	public boolean isConversionSupported(Currency from, Currency to) {

		return sourceCurrency.equals(from) && destinationCurrency.equals(to);

	}

	public BigDecimal getSourceEquivalent() {

		return sourceEquivalent;

	}

	public BigDecimal getDestinationEquivalent() {

		return destinationEquivalent;

	}

	public Currency getSourceCurrency() {

		return sourceCurrency;

	}

	public Currency getDestinationCurrency() {

		return destinationCurrency;

	}

	@Override

	public String toString() {

		return getClass().getName()+" converts "+getSourceCurrency()+" to "+getDestinationCurrency()+" "

			+getSourceCurrency()+getSourceEquivalent()+"="+getDestinationCurrency()+getDestinationEquivalent();

	}

}