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

}