/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/

/*
 *
 * @author Toni Kalajainen
 */
package org.simantics.utils.datastructures.disposable;

import java.lang.reflect.Method;

import org.simantics.utils.threads.IThreadWorkQueue;
import org.simantics.utils.threads.SyncListenerList;

/**
 * Base implementation of IDisposable. The subclass must implement doDispose()
 * method. It invoked at once in first dispose call. Subsequent calls to dispose
 * throws an AssertionError.
 * <p>
 * assertNotDisposed() ensures that the object has not beed disposed. If so,
 * AssertionError is thrown. assertNotDisposed() should be installed in all
 * public methods of subclass.
 * <p>
 * Object is disposed in finalize, if dispose has not been invoked explicitely.
 */
public abstract class AbstractDisposable implements IDisposable {

    SyncListenerList<IDisposeListener> disposeListeners = null;

    private DisposeState disposeStatus = DisposeState.Alive;

    protected void assertNotDisposed() {
        if (isDisposed())
            throw new AssertionError(this + " is disposed.");
    }

    @Override
    public DisposeState getDisposeState() {
        return disposeStatus;
    }
    
    public boolean isDisposed() {
        return disposeStatus == DisposeState.Disposed;
    }
    
    public boolean isAlive() {
        return disposeStatus == DisposeState.Alive;
    }
    
    @Override
    public void dispose() {
        try {
            synchronized (this) {
                if (disposeStatus == DisposeState.Disposing)
                    return;
                assertNotDisposed();
                disposeStatus = DisposeState.Disposing;
            }
            try {
                fireDisposed();
            } finally {
                doDispose();
            }
        } finally {
            synchronized(this) {
                disposeStatus = DisposeState.Disposed;
            }
        }
    }
    
    /**
     * Disposes if not disposed
     */
    public void safeDispose() {        
        try {
            synchronized (this) {
                if (disposeStatus != DisposeState.Alive)
                    return;
                disposeStatus = DisposeState.Disposing;
            }
            try {
                fireDisposed();
            } finally {
                doDispose();
            }
        } finally {
            synchronized(this) {
                disposeStatus = DisposeState.Disposed;
            }
        }
    }

    /**
     * Do dispose procedures. This method is invoked at most once.
     */
    protected abstract void doDispose();

    protected boolean hasDisposeListeners() {
        return disposeListeners!=null && !disposeListeners.isEmpty();
    }

    private final static Method onDisposed = SyncListenerList.getMethod(IDisposeListener.class, "onDisposed");

    private void fireDisposed() {
        if (disposeListeners==null) return;
        disposeListeners.fireEventSync(onDisposed, this);
    }

    @SuppressWarnings("unused")
    private void fireDisposedAsync() {
        if (disposeListeners==null) return;
        disposeListeners.fireEventAsync(onDisposed, this);
    }

    @Override
    public void addDisposeListener(IDisposeListener listener) {
        lazyGetListenerList().add(listener);
    }

    @Override
    public void addDisposeListener(IDisposeListener listener, IThreadWorkQueue thread) {
        lazyGetListenerList().add(thread, listener);
    }

    @Override
    public void removeDisposeListener(IDisposeListener listener) {
        if (disposeListeners==null) return;
        disposeListeners.remove(listener);
    }

    @Override
    public void removeDisposeListener(IDisposeListener listener, IThreadWorkQueue thread) {
        if (disposeListeners==null) return;
        disposeListeners.remove(thread, listener);
    }
    
    private synchronized SyncListenerList<IDisposeListener> lazyGetListenerList()
    {
        if (disposeListeners==null)
            disposeListeners = new SyncListenerList<IDisposeListener>(IDisposeListener.class);
        return disposeListeners;
    }
    
    /*
    @Override
    protected void finalize() throws Throwable {
        try {
            safeDispose();
        } finally {
            super.finalize();
        }
    }
    */
    
}