# HG changeset patch
# User japod@localhost
# Date 1223668479 -7200
# Node ID c38391fb9b38633778d02684a83f512d6c90d9bd
# Parent  221f1930cbfbd24b86611860378a369255b004d6
solution06 task3

diff -r 221f1930cbfb -r c38391fb9b38 task3/solution06/src/org/apidesign/apifest08/currency/Convertor.java
--- a/task3/solution06/src/org/apidesign/apifest08/currency/Convertor.java	Fri Oct 10 21:48:49 2008 +0200
+++ b/task3/solution06/src/org/apidesign/apifest08/currency/Convertor.java	Fri Oct 10 21:54:39 2008 +0200
@@ -8,6 +8,9 @@
 import java.util.Currency;
 import java.util.List;
 
+/**
+ * Currency covertor.
+ */
 public final class Convertor {
 	
 	private List<ConvertorDelegate> convertorDelegates = new ArrayList<ConvertorDelegate>();
@@ -24,7 +27,22 @@
 		notNull(currencyFirst, "currencyFirst");
 		notNull(currencySecond, "currencySecond");		
 		notNull(rateValue, "rateValue");	
-		convertorDelegates.add(new ConvertorDelegate(rateValue, currencyFirst, currencySecond));
+		convertorDelegates.add(new ConvertorDelegate(new StaticRateProvider(rateValue), currencyFirst, currencySecond));
+	}
+	
+	/**
+	 * Create new instance of the converter for the given currencies and its rate. 
+	 * A rate value is provided by {@link RateProvider}.
+	 * 
+	 * @param rateProvider the rate provider
+	 * @param currencyFirst the first currency
+	 * @param currencySecond the second currency
+	 */
+	public Convertor(RateProvider rateProvider, Currency currencyFirst, Currency currencySecond) {
+		notNull(currencyFirst, "currencyFirst");
+		notNull(currencySecond, "currencySecond");		
+		notNull(rateProvider, "rateProvider");
+		convertorDelegates.add(new ConvertorDelegate(rateProvider, currencyFirst, currencySecond));
 	}
 	
 	/**
@@ -84,11 +102,12 @@
 	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
+		private final RateProvider rateProvider;
 		public static final BigDecimal one = new BigDecimal(1);
 		
-		private ConvertorDelegate(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
-			this.rateValue = rateValue;
+		
+		private ConvertorDelegate(RateProvider rateProvider, Currency currencyFirst, Currency currencySecond) {
+			this.rateProvider = rateProvider;
 			this.first = currencyFirst;
 			this.second = currencySecond;
 		}
@@ -104,8 +123,16 @@
 			BigDecimal retVal;
 			
 			if(first == fromCurrency) {
+				BigDecimal rateValue = rateProvider.getRate();
+				if(rateValue == null) {
+					throw new NullPointerException("Rate cannot be null!");
+				}
 				retVal = rateValue;
 			} else {	
+				BigDecimal rateValue = rateProvider.getRate();
+				if(rateValue == null) {
+					throw new NullPointerException("Rate cannot be null!");
+				}
 				//reverse rate	
 				retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
 			}
@@ -121,4 +148,29 @@
 			return ((fromCurrency == first || fromCurrency == second) && (toCurrency == first || toCurrency == second));
 		}
 	}
+	
+	/**
+	 * A rate provider. This class represents a way how could be "static" convertor
+	 * extended in order converts according to current rate.
+	 */
+	public static abstract class RateProvider { 
+		
+		/**
+		 * @return a rate between the from currency and the to currency associated with
+		 * a given convertor.
+		 */
+		public abstract BigDecimal getRate();
+	}
+	
+	private static class StaticRateProvider extends RateProvider{
+		private final BigDecimal rateValue;
+		
+		private StaticRateProvider(BigDecimal rateValue){
+			this.rateValue = rateValue;
+		}
+		
+		public BigDecimal getRate() {
+			return this.rateValue;
+		}
+	}
 }
diff -r 221f1930cbfb -r c38391fb9b38 task3/solution06/test/org/apidesign/apifest08/test/Task3Test.java
--- a/task3/solution06/test/org/apidesign/apifest08/test/Task3Test.java	Fri Oct 10 21:48:49 2008 +0200
+++ b/task3/solution06/test/org/apidesign/apifest08/test/Task3Test.java	Fri Oct 10 21:54:39 2008 +0200
@@ -1,7 +1,11 @@
 package org.apidesign.apifest08.test;
 
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
 import junit.framework.TestCase;
 import org.apidesign.apifest08.currency.Convertor;
+import static org.apidesign.apifest08.test.Currencies.*;
 
 /** The exchange rates are not always the same. They are changing. Day by day,
  * hour by hour, minute by minute. For every bank it is important to always
@@ -43,6 +47,21 @@
      * @return new instance of "online" USD and CZK convertor starting with rate 1USD = 16CZK
      */
     public static Convertor createOnlineCZKUSDConvertor() {
+    	Convertor.RateProvider rateProvider = new Convertor.RateProvider() {
+    		private BigDecimal seed = new BigDecimal("16.01").setScale(2);
+    		
+			@Override
+			public BigDecimal getRate() {
+				if(seed.equals(new BigDecimal("15").setScale(2))) {
+					seed = seed.add(new BigDecimal("0.01")).setScale(2);
+				} else {
+					seed = seed.subtract(new BigDecimal("0.01")).setScale(2);
+				}	
+				return seed;
+			}
+    		
+    	};
+    	
         // initial rate: 1USD = 16CZK
         // 2nd query 1USD = 15.99CZK
         // 3rd query 1USD = 15.98CZK
@@ -51,7 +70,7 @@
         // then 1USD = 15.02CZK
         // and so on and on up to 1USD = 16CZK
         // and then another round to 15, etc.
-        return null;
+        return new Convertor(rateProvider, USD, CZK);
     }
 
     public void testFewQueriesForOnlineConvertor() {
@@ -66,18 +85,16 @@
 
     static void doFewQueriesForOnlineConvertor(Convertor c) {
         // convert $5 to CZK using c:
-        //assertEquals("Result is 80 CZK");
+        assertEquals("Result is 80 CZK",80 ,c.convert(new BigDecimal(5), USD, CZK).getValue().intValue());
 
         // convert $8 to CZK using c:
-        //assertEquals("Result is 127.92 CZK");
+        assertEquals("Result is 127.92 CZK", 127.92d , c.convert(new BigDecimal(8), USD, CZK).getValue().doubleValue());
 
         // convert $1 to CZK using c:
-        //assertEquals("Result is 15.98 CZK");
+        assertEquals("Result is 15.98 CZK", 15.98d,  c.convert(new BigDecimal(1), USD, CZK).getValue().doubleValue());
 
         // convert 15.97CZK to USD using c:
-        //assertEquals("Result is 1$");
-
-        fail("Implement me!");
+        assertEquals("Result is 1$", 1, c.convert(new BigDecimal("15.97").setScale(2), CZK, USD).getValue().intValue());
     }
 
     /** Join the convertors and show they behave sane.
@@ -94,10 +111,10 @@
         );
 
         // convert 16CZK to SKK using c:
-        // assertEquals("Result is 20 SKK");
+        assertEquals("Result is 20 SKK", 20, c.convert(new BigDecimal(16), CZK, SKK).getValue().intValue());
 
         // convert 500SKK to CZK using c:
-        // assertEquals("Result is 400 CZK");
+        assertEquals("Result is 400 CZK", 400, c.convert(new BigDecimal(500), SKK, CZK).getValue().intValue());
 
         doFewQueriesForOnlineConvertor(c);
     }