package org.apidesign.openfixed;

 import java.util.ArrayList;

 import java.util.List;

 import junit.framework.TestCase;

 public abstract class CalculatorBase extends TestCase {

     public CalculatorBase(String testName) {

         super(testName);

     }

     protected abstract Calculator create();

     public void testSumAndListeners() throws Exception {

         Calculator a = create();

         MockListener l = new MockListener();

         a.addModificationListener(l);

         a.add(5);

         a.add(10);

         a.add(20);

         int ch = allChanges(l.assertEvents("Three changes", 3));

         assertEquals("35 was the change", 35, ch);

         assertEquals("Current value", 35, a.getSum());

         a.add(-5);

         int ch2 = allChanges(l.assertEvents("One change", 1));

         assertEquals("minus five was the change", -5, ch2);

         assertEquals("Final value", 30, a.getSum());

     }

     private static int allChanges(List<ModificationEvent> events) {

         int changes = 0;

         for (ModificationEvent me : events) {

             changes += me.getChange();

         }

         return changes;

     }

     public static class MockListener implements ModificationListener {

         private List<ModificationEvent> events;

         @Override

         public synchronized void modification(ModificationEvent ev) {

             if (events == null) {

                 events = new ArrayList<ModificationEvent>();

             }

             events.add(ev);

         }

         public synchronized List<ModificationEvent> assertEvents(String msg, int cnt) 

         throws InterruptedException {

             for (int i = 0; i < 10; i++) {

                 if (events != null && events.size() >= cnt) {

                     break;

                 }

                 wait(1000);

             }

             assertEquals(msg + ":\n" + events, cnt, events.size());

             List<ModificationEvent> res = events;

             events = null;

             return res;

         }

     } // end of ModificationListener

 }