/*******************************************************************************
 * Copyright (c) 2006, 2008 IBM Corporation and others.
 * 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:
 *     IBM Corporation - initial API and implementation
 *     Brad Reynolds - bug 164653
 *     Matthew Hall - bug 208332
 *******************************************************************************/

module org.eclipse.core.databinding.observable.value.AbstractObservableValue;

import java.lang.all;

import org.eclipse.core.databinding.observable.AbstractObservable;
import org.eclipse.core.databinding.observable.ObservableTracker;
import org.eclipse.core.databinding.observable.Realm;

/**
 * 
 * <p>
 * This class is thread safe. All state accessing methods must be invoked from
 * the {@link Realm#isCurrent() current realm}. Methods for adding and removing
 * listeners may be invoked from any thread.
 * </p>
 * @since 1.0
 * 
 */
abstract public class AbstractObservableValue : AbstractObservable , IObservableValue {
    /**
     * Constructs a new instance with the default realm.
     */
    public this() {
        this(Realm.getDefault());
    }

    /**
     * @param realm
     */
    public this(Realm realm) {
        super(realm);
    }

    public synchronized void addValueChangeListener(IValueChangeListener listener) {
        addListener(ValueChangeEvent.TYPE, listener);
    }

    public synchronized void removeValueChangeListener(IValueChangeListener listener) {
        removeListener(ValueChangeEvent.TYPE, listener);
    }

    final public void setValue(Object value) {
        checkRealm();
        doSetValue(value);
    }

    /**
     * Template method for setting the value of the observable. By default the
     * method throws an {@link UnsupportedOperationException}.
     * 
     * @param value
     */
    protected void doSetValue(Object value) {
        throw new UnsupportedOperationException();
    }

    protected void fireValueChange(ValueDiff diff) {
        // fire general change event first
        super.fireChange();
        fireEvent(new ValueChangeEvent(this, diff));
    }

    public final Object getValue() {
        getterCalled();
        return doGetValue();
    }

    abstract protected Object doGetValue();

    public bool isStale() {
        getterCalled();
        return false;
    }

    private void getterCalled() {
        ObservableTracker.getterCalled(this);
    }

    protected void fireChange() {
        throw new RuntimeException(
                "fireChange should not be called, use fireValueChange() instead"); //$NON-NLS-1$
    }

    public synchronized void dispose() {
        super.dispose();
    }
}