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));

     }

 }