package org.apidesign.apifest08.currency;

import java.math.BigDecimal;

import java.util.Currency;

/**

 * The exchange rate between two currencies.

 *

 * @author D'Arcy Smith

 * @version 1.0

 */

public final class ExchangeRate

{

    /**

     * 

     */

    private final Currency currencyA;

    /**

     * 

     */

    private final Currency currencyB;

    /**

     * 

     */

    private final BigDecimal rateAtoB;

    /**

     * 

     */

    private final BigDecimal rateBtoA;

    /**

     * Construct an ExchangeRate with the specified values.

     * 

     * @param a the first currency

     * @param b the second currency

     * @param ra the rate to convert a to b

     * @param rb the rate to covertt b to a

     * @throws IllegalArgumentException if any parameter is null.

     */

    public ExchangeRate(final Currency   a,

                        final Currency   b,

                        final BigDecimal ra,

                        final BigDecimal rb)

    {

        if(a == null)

        {

            throw new IllegalArgumentException("a cannot be null");

        }

        if(b == null)

        {

            throw new IllegalArgumentException("b cannot be null");

        }

        if(ra == null)

        {

            throw new IllegalArgumentException("ra cannot be null");

        }

        if(rb == null)

        {

            throw new IllegalArgumentException("rb cannot be null");

        }

        if(ra.compareTo(BigDecimal.ZERO) <= 0)

        {

            throw new IllegalArgumentException("ra cannot be <= 0, was: " + ra);

        }

        if(rb.compareTo(BigDecimal.ZERO) <= 0)

        {

            throw new IllegalArgumentException("rb cannot be <= 0, was: " + ra);

        }

        currencyA = a;

        currencyB = b;

        rateAtoB  = ra;

        rateBtoA  = rb;

    }

    /**

     * Get the first currency.

     * 

     * @return the first currency.

     */

    public Currency getCurrencyA()

    {

        return currencyA;

    }

    /**

     * Get the second currency.

     * 

     * @return the second currency.

     */

    public Currency getCurrencyB()

    {

        return currencyB;

    }

    /**

     * Get the conversion rate from currencyA to currencyB.

     * 

     * @return the conversion rate from currencyA to currencyB.

     */

    public BigDecimal getRateAtoB()

    {

        return rateAtoB;

    }

    /**

     * Get the conversion rate from currencyB to currencyA.

     * 

     * @return the conversion rate from currencyB to currencyA.

     */

    public BigDecimal getRateBtoA()

    {

        return rateBtoA;

    }

}