japod@55: package org.apidesign.apifest08.currency;
japod@55: 
japod@55: 
japod@55: import java.math.BigDecimal;
japod@55: import java.util.Currency;
japod@55: import java.util.Set;
japod@55: 
japod@55: 
japod@55: /**
japod@55:  * A Convertor that looks up the exchange rate with each call to "convert".
japod@55:  *
japod@55:  * @author D'Arcy Smith
japod@55:  * @version 1.0
japod@55:  */
japod@55: public class OnlineConvertor
japod@55:     implements Convertor
japod@55: {
japod@55:     /**
japod@55:      * The currency to convert from.
japod@55:      */
japod@55:     private final Currency currencyA;
japod@55: 
japod@55:     /**
japod@55:      * The currency to convert to.
japod@55:      */
japod@55:     private final Currency currencyB;
japod@55: 
japod@55:     /**
japod@55:      * Used to find the current exchange rate.
japod@55:      */
japod@55:     private final ExchangeRateFinder finder;
japod@55:     
japod@55:     /**
japod@55:      * The convertor to perform the conversion.
japod@55:      */
japod@55:     private Convertor realConvertor;
japod@55: 
japod@55:     /**
japod@55:      * Constructs an OnlinConvertor with the specified currencies.
japod@55:      * 
japod@55:      * @param a the currency to convert from.
japod@55:      * @param b the currency to convert to.
japod@55:      * @param f the finder used to obtanin the current exchange rate.
japod@55:      * @throws IllegalArgumentException if either a or b are null.
japod@55:      */
japod@55:     public OnlineConvertor(final Currency           a,
japod@55:                            final Currency           b,
japod@55:                            final ExchangeRateFinder f)
japod@55:     {
japod@55:         if(a == null)        
japod@55:         {
japod@55:             throw new IllegalArgumentException("a cannot be null");
japod@55:         }
japod@55:         
japod@55:         if(b == null)
japod@55:         {
japod@55:             throw new IllegalArgumentException("b cannot be null");
japod@55:         }
japod@55:         
japod@55:         if(f == null)
japod@55:         {
japod@55:             throw new IllegalArgumentException("f cannot be null");
japod@55:         }
japod@55:         
japod@55:         currencyA     = a;
japod@55:         currencyB     = b;
japod@55:         finder        = f;
japod@55:         realConvertor = lookupRate();
japod@55:     }
japod@55: 
japod@55:     /**
japod@55:      * Convert an amount from one currency to another.  Before the conversion takes place 
japod@55:      * the current exchange rate is looked up.
japod@55:      *
japod@55:      * @param from the currency to convert from.
japod@55:      * @param to the currency to convert to.
japod@55:      * @param amount the amount to convert.
japod@55:      * @return the converted amount.
japod@55:      * @throws IllegalArgumentException if any of the arguments are null.
japod@55:      * @throws InvalidConversionException if either from or to are not equal to the currencies passed to the constructor.
japod@55:      */
japod@55:     public BigDecimal convert(final Currency   from, 
japod@55:                               final Currency   to, 
japod@55:                               final BigDecimal amount) 
japod@55:         throws InvalidConversionException
japod@55:     {
japod@55:         final BigDecimal value;
japod@55:         
japod@55:         synchronized(this)
japod@55:         {
japod@55:             realConvertor = lookupRate();
japod@55:             value         = realConvertor.convert(from, to, amount);
japod@55:         }
japod@55:         
japod@55:         return (value);
japod@55:     }
japod@55: 
japod@55:     /**
japod@55:      * Lookup the current exchange rate.
japod@55:      * 
japod@55:      * @return
japod@55:      */
japod@55:     private final Convertor lookupRate()
japod@55:     {
japod@55:         final Convertor convertor;
japod@55:         final ExchangeRate rate;
japod@55: 
japod@55:         rate      = finder.findRate(currencyA, currencyB);
japod@55:         convertor = ConvertorFactory.getConvertor(rate.getCurrencyA(), rate.getRateAtoB(), rate.getCurrencyB(), rate.getRateBtoA());
japod@55: 
japod@55:         return (convertor);
japod@55:     }
japod@55: 
japod@55:     /**
japod@55:      * Check to see if converting between the two currencies is possible.
japod@55:      * 
japod@55:      * @param from the currency to convert from.
japod@55:      * @param to the currency to convert to.
japod@55:      * @return true if the conversion is possible.
japod@55:      * @throws IllegalArgumentException if either from or to are null.
japod@55:      */
japod@55:     public boolean canConvert(final Currency from, 
japod@55:                               final Currency to) 
japod@55:     {
japod@55:         if(from == null)
japod@55:         {
japod@55:             throw new IllegalArgumentException("from cannot be null");
japod@55:         }
japod@55:         
japod@55:         if(to == null)
japod@55:         {
japod@55:             throw new IllegalArgumentException("to cannot be null");
japod@55:         }
japod@55:         
japod@55:         return (realConvertor.canConvert(from, to));
japod@55:     }
japod@55: 
japod@55:     /**
japod@55:      * Get the currencies that the convertor supports.
japod@55:      * 
japod@55:      * @return the supported currencies.
japod@55:      */
japod@55:     public Set<Currency> getCurrencies() 
japod@55:     {
japod@55:         return (realConvertor.getCurrencies());
japod@55:     }
japod@55: 
japod@55:     /**
japod@55:      * Get the conversion rate between two currencies.  This does not lookup the current
japod@55:      * conversion rate (it probably should, but given the way the contest works that might 
japod@55:      * not be a good idea - if it were the real world way it might be a good idea).
japod@55:      * 
japod@55:      * @param from the currency to convert from.
japod@55:      * @param to the currency to convert to.
japod@55:      * @return the conversion rate between the two currencies.
japod@55:      * @throws InvalidConversionException if canConvert would return false.
japod@55:      * @throws IllegalArgumentException if either from or to are null.
japod@55:      */
japod@55:     public BigDecimal getConversionRate(final Currency from, 
japod@55:                                         final Currency to) 
japod@55:         throws InvalidConversionException 
japod@55:     {        
japod@55:         if(from == null)
japod@55:         {
japod@55:             throw new IllegalArgumentException("from cannot be null");
japod@55:         }
japod@55:         
japod@55:         if(to == null)
japod@55:         {
japod@55:             throw new IllegalArgumentException("to cannot be null");
japod@55:         }
japod@55:         
japod@55:         return (realConvertor.getConversionRate(from, to));
japod@55:     }    
japod@55: }