package org.apidesign.apifest08.currency;

import java.math.BigDecimal;

import java.math.MathContext;

import java.math.RoundingMode;

import java.util.Currency;

/**

 * Convert between two currencies.

 *

 * @author D'Arcy Smith

 * @version 1.0

 */

public final class Convertor

{

    /**

     * The currency to cvonvert from.

     */

    private final Currency currencyA;

    /**

     * The currency to cvonvert from.

     */

    private final Currency currencyB;

    /**

     * Constructs a convertor with the specified currencies.

     * 

     * @param a the currency to convert from.

     * @param b the currency to convert to.

     * @throws IllegalArgumentException if either a or b are null.

     */

    public Convertor(final Currency a,

                     final Currency b)

    {

        if(a == null)

        {

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

        }

        if(b == null)

        {

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

        }

        currencyA = a;

        currencyB = b;

    }

    /**

     * Convert from currency "b" to currency "a".

     * 

     * @param amount the amount to convert.

     * @return the converted amount.

     * @throws IllegalArgumentException if amount is null.

     */

    public BigDecimal convertFrom(final BigDecimal amount)

    {

        final BigDecimal aInUSD;

        final BigDecimal bInUSD;

        final BigDecimal temp;

        final BigDecimal result;

        if(amount == null)

        {

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

        }

        aInUSD = CurrencyValues.getValue(currencyA);

        bInUSD = CurrencyValues.getValue(currencyB);

        temp   = amount.divide(bInUSD, MathContext.DECIMAL32);

        result = temp.multiply(aInUSD);

        return (result.setScale(2, RoundingMode.HALF_DOWN));

    }

    /**

     * Convert from currency "a" to currency "b".

     * 

     * @param amount the amount to convert.

     * @return the converted amount.

     * @throws IllegalArgumentException if amount is null.

     */

    public BigDecimal convertTo(final BigDecimal amount)

    {

        final BigDecimal aInUSD;

        final BigDecimal bInUSD;

        final BigDecimal temp;

        final BigDecimal result;

        if(amount == null)

        {

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

        }

        aInUSD = CurrencyValues.getValue(currencyA);

        bInUSD = CurrencyValues.getValue(currencyB);

        temp      = amount.divide(aInUSD, MathContext.DECIMAL32);

        result = temp.multiply(bInUSD);

        return (result.setScale(2, RoundingMode.HALF_DOWN));

    }

}