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 Convertor, Serializable {

	private static final long serialVersionUID = -1754789142402148099L;

	/**

	 * 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(BigDecimal sourceEquivalent, BigDecimal destinationEquivalent, Currency sourceCurrency, Currency destinationCurrency) {

		super();

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

		{

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

		}

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

		{

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

		}

		this.sourceEquivalent = sourceEquivalent;

		this.destinationEquivalent = destinationEquivalent;

		this.sourceCurrency = sourceCurrency;

		this.destinationCurrency = destinationCurrency;

	}

	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 (isConversionInOpositeDirection(amount, destinationCurrency))

		{

			return revert().convert(amount, destinationCurrency);

		}

		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());

	}

	/**

	 * Returns true, if the conversion is in oposit direction.

	 * @param amount

	 * @param destinationCurrency

	 * @return

	 */

	private boolean isConversionInOpositeDirection(Money amount,	Currency destinationCurrency) {

		return amount.getCurrency().equals(getDestinationCurrency()) && destinationCurrency.equals(getSourceCurrency());

	}

	public Convertor revert() {

		return new DefaultConvertor(destinationEquivalent, sourceEquivalent, destinationCurrency, sourceCurrency);

	}

	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();

	}

	@Override

	public int hashCode() {

		final int prime = 31;

		int result = 1;

		result = prime

				* result

				+ ((destinationCurrency == null) ? 0 : destinationCurrency

						.hashCode());

		result = prime

				* result

				+ ((destinationEquivalent == null) ? 0 : destinationEquivalent

						.hashCode());

		result = prime * result

				+ ((sourceCurrency == null) ? 0 : sourceCurrency.hashCode());

		result = prime

				* result

				+ ((sourceEquivalent == null) ? 0 : sourceEquivalent.hashCode());

		return result;

	}

	@Override

	public boolean equals(Object obj) {

		if (this == obj)

			return true;

		if (obj == null)

			return false;

		if (!(obj instanceof DefaultConvertor))

			return false;

		DefaultConvertor other = (DefaultConvertor) obj;

		if (destinationCurrency == null) {

			if (other.destinationCurrency != null)

				return false;

		} else if (!destinationCurrency.equals(other.destinationCurrency))

			return false;

		if (destinationEquivalent == null) {

			if (other.destinationEquivalent != null)

				return false;

		} else if (!destinationEquivalent.equals(other.destinationEquivalent))

			return false;

		if (sourceCurrency == null) {

			if (other.sourceCurrency != null)

				return false;

		} else if (!sourceCurrency.equals(other.sourceCurrency))

			return false;

		if (sourceEquivalent == null) {

			if (other.sourceEquivalent != null)

				return false;

		} else if (!sourceEquivalent.equals(other.sourceEquivalent))

			return false;

		return true;

	}

}