package org.apidesign.apifest08.currency;

 import java.math.BigDecimal;

 import java.util.Currency;

 import java.util.Date;

 /**

  * Create convertors using a flyweight to reduce the number of repetative creations of the same convertor.

  * 

  * @author D'Arcy Smith

  * @version 1.2

  */

 public final class ConvertorFactory

 {

     /** 

      * Prevent accidental construction.

      */

     private ConvertorFactory()

     {        

     }

     /**

      * Get the convertor for the specified currencies.  The currency name format

      * must be acceptable to java.util.Currency.getInstance(String)

      * 

      * @param a the currency to convert from.

      * @param aRate the exchange rate for a to b.

      * @param b the currency to convert to.

      * @param bRate the echante rate for b to a.

      * @return the convertor for the specified currencies.

      * @throws IllegalArgumentException if any of the arguments are null.

      */

     public static Convertor getConvertor(final String     a,

                                          final BigDecimal aRate,

                                          final String     b,

                                          final BigDecimal bRate)

     {

         final Currency  currencyA;

         final Currency  currencyB;

         final Convertor convertor;

         currencyA = Currency.getInstance(a);

         currencyB = Currency.getInstance(b);        

         convertor = getConvertor(currencyA, aRate, currencyB, bRate);

         return (convertor);

     }

     /**

      * Get the convertor for the specified currencies.

      * 

      * @param a the currency to convert from.

      * @param aRate the exchange rate for a to b.

      * @param b the currency to convert to.

      * @param bRate the echante rate for b to a.

      * @return the convertor for the specified currencies.

      * @throws IllegalArgumentException if either any of the arguments are null or if either rate <= 0.

      */

     public static Convertor getConvertor(final Currency   a,

                                          final BigDecimal aRate,

                                          final Currency   b,

                                          final BigDecimal bRate)

     {

         Convertor          convertor;

         final ExchangeRate rate;

         if(a == null)

         {

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

         }

         if(b == null)

         {

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

         }

         if(aRate == null)

         {

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

         }

         if(bRate == null)

         {

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

         }

         rate      = ExchangeRate.getExchangeRate(a, b, aRate, bRate);

         convertor = getConvertor(rate);

         return (convertor);

     }

     public static Convertor getConvertor(final ExchangeRate rate)

     {

         final ConvertorImpl convertor;

         if(rate == null)

         {

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

         }

         convertor = new ConvertorImpl(rate);

         return (convertor);        

     }

     public static DatedConvertor getConvertor(final Date      from,

                                               final Date      till,

                                               final Convertor convertor)

     {

         final DateRange      range;

         final ExchangeRate   rate;

         final DatedConvertor datedConvertor;

         if(from == null)

         {

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

         }

         if(till == null)

         {

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

         }

         if(convertor == null)

         {

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

         }

         if(from.after(till))

         {

             throw new IllegalArgumentException(from + " cannot be after " + till);

         }

         if(convertor instanceof ExchangeRateConvertor)

         {

             rate = ((ExchangeRateConvertor)convertor).getExchangeRate();

         }

         else

         {

             throw new Error();

         }

         range          = new DateRange(from, till);

         datedConvertor = new DatedConvertorImpl(range, rate);

         return (datedConvertor);

     }

     /**

      * 

      * @param cs

      * @return

      */

     public static Convertor mergeConvertors(final Convertor ... cs)

     {

         Convertor convertor;

         int       dated;

         int       nonDated;

         dated    = 0;

         nonDated = 0;

         for(final Convertor c : cs)

         {

             if(c instanceof DatedConvertor)

             {

                 dated++;

             }

             else

             {

                 nonDated++;

             }

         }

         if(dated != 0 && nonDated != 0)

         {

             throw new IllegalArgumentException("cannot mix DatedConvertors and non-DatedConvertors");

         }

         if(dated != 0)

         {

             convertor = new DatedCompositeConvertorImpl(cs);

         }

         else

         {

             convertor = new CompositeConvertorImpl(cs);

         }

         return (convertor);

     }

 }