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/*******************************************************************************
* Copyright (c) 2012 Oracle. 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:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.common.utility.internal.model.value;
import org.eclipse.jpt.common.utility.model.event.PropertyChangeEvent;
import org.eclipse.jpt.common.utility.model.listener.PropertyChangeAdapter;
import org.eclipse.jpt.common.utility.model.listener.PropertyChangeListener;
import org.eclipse.jpt.common.utility.model.value.PropertyValueModel;
/**
* This property value model <em>wrapper</em> wraps another property value model
* and treats the <em>wrapped</em> model's value as the <em>wrapper</em>'s value.
* Any change events fired by the <em>wrapped</em> model are simply forwarded by
* the <em>wrapper</em> as its own.
* Similarly, changing the <em>wrapper</em>'s <em>wrapped</em> model can also
* trigger a change event
* (see {@link #wrappedValueChanged(PropertyValueModel, PropertyValueModel)}).
* That is, the <em>wrapped</em> model is held by yet another property value
* model!
* <p>
* <ul>
* <li>Double (<em>wrapper</em>) property value model - a client can listen to
* this model and receive the same change notification whether the
* <em>wrapped</em> model or the <em>wrapped</em> model's value changes;
* much like an {@link PropertyAspectAdapter aspect adapter} whose subject
* model is <em>not</em> another property value model
* <ul>
* <li><em>Wrapped</em> property value model - this model is built and
* maintained by the server that also builds the <em>wrapper</em> model
* (i.e. the server will monitor some other model that determines when
* the <em>wrapped</em> model is changed)
* <ul>
* <li>Original property value model - this model is the "original"
* model that contains the value of interest
* </ul>
* </ul>
* </ul>
* <p>
* This wrapper is useful when a change in the <em>wrapped</em> model is
* signaled by a non-value event and a third-party would like to change it.
*
* @param <V> the type of the both the <em>wrapped</em> and <em>wrapper</em>
* models' values
*/
public class DoublePropertyValueModel<V>
extends PropertyValueModelWrapper<PropertyValueModel<? extends V>>
implements PropertyValueModel<V>
{
/**
* The optionally present wrapped value model value; held by
* {@link #valueModel}. This may be <code>null</code>.
*/
protected volatile PropertyValueModel<? extends V> valueModelValueModel;
/**
* A listener that allows us to sync with changes to the wrapped value
* model model.
*/
protected final PropertyChangeListener valueModelValueListener;
// ********** constructors/initialization **********
/**
* Construct a double property value model for the specified
* wrapped property value model model.
*/
public DoublePropertyValueModel(PropertyValueModel<? extends PropertyValueModel<? extends V>> valueModel) {
super(valueModel);
this.valueModelValueListener = this.buildValueModelValueListener();
}
protected PropertyChangeListener buildValueModelValueListener() {
return new ValueModelListener();
}
/* CU private */ class ValueModelListener
extends PropertyChangeAdapter
{
@Override
public void propertyChanged(PropertyChangeEvent event) {
DoublePropertyValueModel.this.wrappedValueModelValueChanged(event);
}
}
// ********** PropertyValueModel implementation **********
public V getValue() {
return (this.valueModelValueModel == null) ? null : this.valueModelValueModel.getValue();
}
@Override
public void toString(StringBuilder sb) {
sb.append(this.getValue());
}
// ********** wrapped value model **********
/**
* The value model has changed.
* Move our value model listener and
* notify listeners that the value has changed.
*/
@Override
protected void wrappedValueChanged(PropertyValueModel<? extends V> oldValue, PropertyValueModel<? extends V> newValue) {
if (this.hasListeners()) {
V old = this.getValue();
this.disengageValueModel();
this.engageValueModel();
this.firePropertyChanged(VALUE, old, this.getValue());
}
}
// ********** wrapped value model value **********
/**
* The value of the wrapped value model's value model has changed.
* Forward the event as our own.
*/
protected void wrappedValueModelValueChanged(PropertyChangeEvent event) {
this.firePropertyChanged(event.clone(this));
}
/**
* Begin listening to the value model.
*/
@Override
protected void engageModel() {
super.engageModel();
this.engageValueModel();
}
protected void engageValueModel() {
this.valueModelValueModel = this.valueModel.getValue();
if (this.valueModelValueModel != null) {
this.valueModelValueModel.addPropertyChangeListener(VALUE, this.valueModelValueListener);
}
}
/**
* Stop listening to the value model.
*/
@Override
protected void disengageModel() {
this.disengageValueModel();
super.disengageModel();
}
protected void disengageValueModel() {
if (this.valueModelValueModel != null) {
this.valueModelValueModel.removePropertyChangeListener(VALUE, this.valueModelValueListener);
}
this.valueModelValueModel = null;
}
}
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