# HG changeset patch
# User japod@localhost
# Date 1223332977 -7200
# Node ID 5838e0aaa81f23f25f846bd0ce86c1bd5bea1525
# Parent  d333e45f6df14493ecefe1a0a304fae936c45e36
adding solution06 for task2

diff -r d333e45f6df1 -r 5838e0aaa81f task2/solution06/src/org/apidesign/apifest08/currency/Convertor.java
--- a/task2/solution06/src/org/apidesign/apifest08/currency/Convertor.java	Tue Oct 07 00:25:53 2008 +0200
+++ b/task2/solution06/src/org/apidesign/apifest08/currency/Convertor.java	Tue Oct 07 00:42:57 2008 +0200
@@ -4,23 +4,44 @@
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
+import java.util.ArrayList;
 import java.util.Currency;
+import java.util.List;
 
 public final class Convertor {
 	
-	private final Currency first;
-	private final Currency second;
-	private final BigDecimal rateValue; // a rate between the first currency and the second currency
-	public static final BigDecimal one = new BigDecimal(1);	
+	private List<ConvertorDelegate> convertorDelegates = new ArrayList<ConvertorDelegate>();
 	
+	
+	/**
+	 * Create new instance of the converter for the given currencies and its rate.
+	 * 
+	 * @param rateValue the rate between the first and the second currency
+	 * @param currencyFirst the first currency
+	 * @param currencySecond the second currency
+	 */
 	public Convertor(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
 		notNull(currencyFirst, "currencyFirst");
 		notNull(currencySecond, "currencySecond");		
-		notNull(rateValue, "rateValue");
+		notNull(rateValue, "rateValue");	
+		convertorDelegates.add(new ConvertorDelegate(rateValue, currencyFirst, currencySecond));
+	}
+	
+	/**
+	 * Create new instance of the convertor from the given convertors. 
+	 * @param convertors the convertors
+	 */
+	public Convertor(Convertor... convertors) {
+		notNull(convertors, "convertors");
+		if(convertors.length == 0) {
+			throw new IllegalArgumentException("There must be at least one converter.");
+		}
 		
-		this.rateValue = rateValue;
-		this.first = currencyFirst;
-		this.second = currencySecond;
+		for(Convertor convertor: convertors) {
+			if(convertor != null) {
+				convertorDelegates.addAll(convertor.convertorDelegates);
+			}
+		}
 	}
     	
 	/**
@@ -38,27 +59,66 @@
 		notNull(amount, "amount");
 		notNull(fromCurrency, "fromCurrency");
 		notNull(toCurrency, "toCurrency");
+		ConvertorDelegate appropriateDelegate = null;
 		
-		if((fromCurrency != first && fromCurrency != second) || (toCurrency != first && toCurrency != second)) {
+		//try find an appropriate delegate for conversion
+		for(ConvertorDelegate delegate : convertorDelegates) {
+			if(delegate.isConversionSupported(fromCurrency, toCurrency)) {
+				appropriateDelegate = delegate;
+				break;
+			}
+		}
+		
+		if(appropriateDelegate == null) {
 			throw new UnsupportedConversionException(fromCurrency, toCurrency);
-		}		
-
-		BigDecimal rateValue = getRateValue(fromCurrency, toCurrency);
-		BigDecimal result = rateValue.multiply(amount);			
-		return new Amount(result, toCurrency);	
+		}
+		
+		return appropriateDelegate.convert(amount, fromCurrency, toCurrency);	
 	}
 	
-	private BigDecimal getRateValue(Currency fromCurrency, Currency toCurrency) {		
+	/**
+	 * Internal delegate implements a logic for conversion between two currencies
+	 * and vice versa.
+	 * @see #isConversionSupported(Currency, Currency)
+	 */
+	private static class ConvertorDelegate {
+		private final Currency first;
+		private final Currency second;
+		private final BigDecimal rateValue; // a rate between the first currency and the second currency
+		public static final BigDecimal one = new BigDecimal(1);
 		
-		BigDecimal retVal;
-		
-		if(first == fromCurrency) {
-			retVal = rateValue;
-		} else {	
-			//reverse rate	
-			retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
+		private ConvertorDelegate(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
+			this.rateValue = rateValue;
+			this.first = currencyFirst;
+			this.second = currencySecond;
 		}
 		
-		return retVal;
+		private Amount convert(BigDecimal amount, Currency fromCurrency, Currency toCurrency) throws ConversionException {
+			BigDecimal rateValue = getRateValue(fromCurrency, toCurrency);
+			BigDecimal result = rateValue.multiply(amount);			
+			return new Amount(result, toCurrency);	
+		}
+		
+		private BigDecimal getRateValue(Currency fromCurrency, Currency toCurrency) {		
+			
+			BigDecimal retVal;
+			
+			if(first == fromCurrency) {
+				retVal = rateValue;
+			} else {	
+				//reverse rate	
+				retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
+			}
+			
+			return retVal;
+		}
+		
+		/**
+		 * @return <code>true</code> if the delegate is able to convert from the given currency
+		 * to the given currency and vice versa otherwise <code>false</code>.
+		 */
+		private boolean isConversionSupported(Currency fromCurrency, Currency toCurrency) {
+			return ((fromCurrency == first || fromCurrency == second) && (toCurrency == first || toCurrency == second));
+		}
 	}
 }