japod@6: package org.apidesign.apifest08.currency;
japod@6: 
japod@17: import java.math.BigDecimal;
japod@6: import java.util.Currency;
japod@6: 
japod@6: 
japod@6: /**
japod@6:  * Create convertors using a flyweight to reduce the number of repetative creations of the same convertor.
japod@6:  * 
japod@6:  * @author D'Arcy Smith
japod@6:  * @version 1.0
japod@6:  */
japod@6: public final class ConvertorFactory
japod@6: {
japod@35:     /*
japod@6:      * flyweight so that only one vestion of each converter is created at a time.
japod@6:     private final static Map<String, WeakReference<Convertor>> convertors;
japod@6:     
japod@6:     static
japod@6:     {
japod@6:         convertors = new WeakHashMap<String, WeakReference<Convertor>>();
japod@6:     }
japod@35:     */
japod@6:     
japod@6:     /** 
japod@6:      * Prevent accidental construction.
japod@6:      */
japod@6:     private ConvertorFactory()
japod@6:     {        
japod@6:     }
japod@6:     
japod@6:     /**
japod@6:      * Get the convertor for the specified currencies.  The currency name format
japod@6:      * must be acceptable to java.util.Currency.getInstance(String)
japod@6:      * 
japod@6:      * @param a the currency to convert from.
japod@17:      * @param aRate the exchange rate for a to b.
japod@6:      * @param b the currency to convert to.
japod@17:      * @param bRate the echante rate for b to a.
japod@6:      * @return the convertor for the specified currencies.
japod@17:      * @throws IllegalArgumentException if any of the arguments are null.
japod@6:      */
japod@17:     public static Convertor getConvertor(final String     a,
japod@17:                                          final BigDecimal aRate,
japod@17:                                          final String     b,
japod@17:                                          final BigDecimal bRate)
japod@6:     {
japod@6:         final Currency  currencyA;
japod@6:         final Currency  currencyB;
japod@6:         final Convertor convertor;
japod@6:         
japod@6:         currencyA = Currency.getInstance(a);
japod@6:         currencyB = Currency.getInstance(b);        
japod@17:         convertor = getConvertor(currencyA, aRate, currencyB, bRate);
japod@6:         
japod@6:         return (convertor);
japod@6:     }
japod@6:     
japod@6:     /**
japod@6:      * Get the convertor for the specified currencies.
japod@6:      * 
japod@6:      * @param a the currency to convert from.
japod@17:      * @param aRate the exchange rate for a to b.
japod@6:      * @param b the currency to convert to.
japod@17:      * @param bRate the echante rate for b to a.
japod@6:      * @return the convertor for the specified currencies.
japod@17:      * @throws IllegalArgumentException if either any of the arguments are null or if either rate <= 0.
japod@6:      */
japod@17:     public static Convertor getConvertor(final Currency   a,
japod@17:                                          final BigDecimal aRate,
japod@17:                                          final Currency   b,
japod@17:                                          final BigDecimal bRate)
japod@6:     {
japod@35:         // final String key;        
japod@6:         Convertor    convertor;
japod@6: 
japod@6:         if(a == null)
japod@6:         {
japod@6:             throw new IllegalArgumentException("a cannot be null");
japod@6:         }
japod@6: 
japod@6:         if(b == null)
japod@6:         {
japod@6:             throw new IllegalArgumentException("b cannot be null");
japod@6:         }
japod@17:         
japod@17:         if(aRate == null)
japod@17:         {
japod@17:             throw new IllegalArgumentException("aRate cannot be null");
japod@17:         }
japod@17:         
japod@17:         if(bRate == null)
japod@17:         {
japod@17:             throw new IllegalArgumentException("bRate cannot be null");
japod@17:         }
japod@6: 
japod@35:         /*
japod@17:         key = a.getCurrencyCode() + aRate + b.getCurrencyCode() + bRate;
japod@6: 
japod@6:         // make sure that we don't try to overwrite one
japod@6:         synchronized(convertors)
japod@6:         {
japod@6:             if(!(convertors.containsKey(key)))
japod@6:             {        
japod@17:                 convertor = new ConvertorImpl(a, aRate, b, bRate);
japod@6:                 convertors.put(key, new WeakReference(convertor));
japod@6:             }
japod@35: 
japod@35:             convertor = convertors.get(key).get();
japod@6:         }
japod@35:         */
japod@35:         
japod@35:         convertor = new ConvertorImpl(a, aRate, b, bRate);
japod@35:                 
japod@35:         return (convertor);
japod@35:     }
japod@35:     
japod@55:     /**
japod@55:      * 
japod@55:      * @param cs
japod@55:      * @return
japod@55:      */
japod@35:     public static Convertor mergeConvertors(final Convertor ... cs)
japod@35:     {
japod@35:         Convertor convertor;
japod@35:         
japod@35:         /*
japod@35:         final String key;
japod@6: 
japod@35:         // ISSUE: only takes into account the names... not the rates...
japod@35:         key = getKey(cs);
japod@35: 
japod@35:         // make sure that we don't try to overwrite one
japod@35:         synchronized(convertors)
japod@35:         {
japod@35:             if(!(convertors.containsKey(key)))
japod@35:             {        
japod@35:                 convertor = new CompositeConvertorImpl(cs);
japod@35:                 convertors.put(key, new WeakReference(convertor));
japod@35:             }
japod@35: 
japod@35:             convertor = convertors.get(key).get();
japod@35:         }
japod@35:         */
japod@35:         
japod@35:         convertor = new CompositeConvertorImpl(cs);
japod@6:         
japod@6:         return (convertor);
japod@6:     }
japod@35: 
japod@35:     /*
japod@35:     private static String getKey(final Convertor ... cs)
japod@35:     {
japod@35:         final Set<Currency> currencies;
japod@35:         final StringBuilder builder;
japod@35:         
japod@35:         currencies = new HashSet<Currency>();
japod@35:         
japod@35:         for(final Convertor convertor : cs)
japod@35:         {
japod@35:             final Set<Currency> c;
japod@35:             
japod@35:             c = convertor.getCurrencies();
japod@35:             currencies.addAll(c);
japod@35:         }
japod@35:         
japod@35:         builder = new StringBuilder();
japod@35: 
japod@35:         for(final Currency currency : currencies)
japod@35:         {
japod@35:             builder.append(currency.getCurrencyCode());
japod@35:         }
japod@35:         
japod@35:         return (builder.toString());
japod@35:     }
japod@35:     */
japod@6: }