package org.apidesign.gc;

import java.awt.Color;

import java.beans.PropertyChangeEvent;

import java.beans.PropertyChangeListener;

import java.lang.ref.WeakReference;

import javax.swing.JPanel;

import junit.framework.AssertionFailedError;

import org.junit.After;

import org.junit.AfterClass;

import org.junit.Before;

import org.junit.BeforeClass;

import org.junit.Test;

import org.netbeans.junit.NbTestCase;

import static org.junit.Assert.*;

public class WeakListenersTest {

    private static JPanel longLivingBean;

    public WeakListenersTest() {

    }

    @BeforeClass

    public static void setUpClass() throws Exception {

        longLivingBean = new JPanel();

    }

    @Before

    public void setUp() {

        longLivingBean.setBackground(Color.BLACK);

    }

    @Test

    public void listenWithoutWeakReference() {

        PropL listener = new PropL();

        longLivingBean.addPropertyChangeListener(listener);

        longLivingBean.setBackground(Color.WHITE);

        assertEquals("background property change notified", "background", listener.propName);

        WeakReference<Object> ref = new WeakReference<Object>(listener);

        listener = null;

        try {

            NbTestCase.assertGC(

                "Of course, this listener cannot disappear, because it is held from long living JavaBean", 

                ref

            );

        } catch (AssertionFailedError ex) {

            ex.printStackTrace();

            // of course it cannot be garbage collected. That is OK.

            return;

        } catch (OutOfMemoryError ex) {

            ex.printStackTrace();

            // sometimes the test fails on OOME, let's catch it

            // of course it cannot be garbage collected. That is OK.

            return;

        }

        fail("The listener cannot be GCed as it is held from long living JavaBean");

    }

    @Test

    public void listenViaWeakListener() {

        PropL listener = new PropL();

        PropertyChangeListener weakL = WeakListeners.create(PropertyChangeListener.class, listener, longLivingBean);

        longLivingBean.addPropertyChangeListener(weakL);

        longLivingBean.setBackground(Color.WHITE);

        assertEquals("background property change notified", "background", listener.propName);

        // BEGIN: gc.assertGC

        WeakReference<Object> ref = new WeakReference<Object>(listener);

        listener = null;

        NbTestCase.assertGC("This listener can disappear", ref);

        // END: gc.assertGC

    }

    private static class PropL implements PropertyChangeListener {

        String propName;

        public void propertyChange(PropertyChangeEvent evt) {

            propName = evt.getPropertyName();

        }

    }

}