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;

 	}

 }