/*******************************************************************************
* Copyright (c) 2007, 2009 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 java.util.ArrayList;
import java.util.Iterator;
import java.util.ListIterator;
import org.eclipse.jpt.common.utility.internal.iterators.ReadOnlyListIterator;
import org.eclipse.jpt.common.utility.model.event.CollectionAddEvent;
import org.eclipse.jpt.common.utility.model.event.CollectionChangeEvent;
import org.eclipse.jpt.common.utility.model.event.CollectionClearEvent;
import org.eclipse.jpt.common.utility.model.event.CollectionRemoveEvent;
import org.eclipse.jpt.common.utility.model.listener.CollectionChangeListener;
import org.eclipse.jpt.common.utility.model.value.CollectionValueModel;
import org.eclipse.jpt.common.utility.model.value.ListValueModel;
/**
* An adapter that allows us to make a {@link CollectionValueModel} behave like
* a read-only {@link ListValueModel}, sorta.
* <p>
* To maintain a reasonably consistent appearance to client code, we
* keep an internal list somewhat in synch with the wrapped collection.
* <p>
* <strong>NB:</strong> Since we only listen to the wrapped collection when we have
* listeners ourselves and we can only stay in synch with the wrapped
* collection while we are listening to it, results to various methods
* (e.g. {@link #size()}, {@link #get(int)}) will be unpredictable whenever
* we do not have any listeners. This should not be too painful since,
* most likely, clients will also be listeners.
*/
public class CollectionListValueModelAdapter<E>
extends AbstractListValueModel
implements ListValueModel<E>
{
/** The wrapped collection value model. */
protected final CollectionValueModel<? extends E> collectionHolder;
/** A listener that forwards any events fired by the collection holder. */
protected final CollectionChangeListener collectionChangeListener;
/**
* Our internal list, which holds the same elements as
* the wrapped collection, but keeps them in order.
*/
// we declare this an ArrayList so we can use #clone() and #ensureCapacity(int)
protected final ArrayList<E> list;
// ********** constructors **********
/**
* Wrap the specified collection value model.
*/
public CollectionListValueModelAdapter(CollectionValueModel<? extends E> collectionHolder) {
super();
if (collectionHolder == null) {
throw new NullPointerException();
}
this.collectionHolder = collectionHolder;
this.collectionChangeListener = this.buildCollectionChangeListener();
this.list = new ArrayList<E>(collectionHolder.size());
// postpone building the list and listening to the underlying collection
// until we have listeners ourselves...
}
// ********** initialization **********
/**
* The wrapped collection has changed, forward an equivalent
* list change event to our listeners.
*/
protected CollectionChangeListener buildCollectionChangeListener() {
return new CollectionChangeListener() {
public void itemsAdded(CollectionAddEvent event) {
CollectionListValueModelAdapter.this.itemsAdded(event);
}
public void itemsRemoved(CollectionRemoveEvent event) {
CollectionListValueModelAdapter.this.itemsRemoved(event);
}
public void collectionCleared(CollectionClearEvent event) {
CollectionListValueModelAdapter.this.collectionCleared(event);
}
public void collectionChanged(CollectionChangeEvent event) {
CollectionListValueModelAdapter.this.collectionChanged(event);
}
@Override
public String toString() {
return "collection change listener"; //$NON-NLS-1$
}
};
}
// ********** ListValueModel implementation **********
public Iterator<E> iterator() {
return this.listIterator();
}
public ListIterator<E> listIterator() {
return new ReadOnlyListIterator<E>(this.list);
}
public E get(int index) {
return this.list.get(index);
}
public int size() {
return this.list.size();
}
public Object[] toArray() {
return this.list.toArray();
}
// ********** behavior **********
@Override
protected void engageModel() {
this.collectionHolder.addCollectionChangeListener(CollectionValueModel.VALUES, this.collectionChangeListener);
// synch our list *after* we start listening to the collection holder,
// since its value might change when a listener is added
this.buildList();
}
@Override
protected void disengageModel() {
this.collectionHolder.removeCollectionChangeListener(CollectionValueModel.VALUES, this.collectionChangeListener);
// clear out the list when we are not listening to the collection holder
this.list.clear();
}
protected void buildList() {
// if the new collection is empty, do nothing
int size = this.collectionHolder.size();
if (size != 0) {
this.buildList(size);
}
}
protected void buildList(int size) {
this.list.ensureCapacity(size);
for (E each : this.collectionHolder) {
this.list.add(each);
}
}
protected void itemsAdded(CollectionAddEvent event) {
this.addItemsToList(this.indexToAddItems(), this.getItems(event), this.list, LIST_VALUES);
}
protected int indexToAddItems() {
return this.list.size();
}
// minimize scope of suppressed warnings
@SuppressWarnings("unchecked")
protected Iterable<E> getItems(CollectionAddEvent event) {
return (Iterable<E>) event.getItems();
}
protected void itemsRemoved(CollectionRemoveEvent event) {
this.removeItemsFromList(this.getItems(event), this.list, LIST_VALUES);
}
// minimize scope of suppressed warnings
@SuppressWarnings("unchecked")
protected Iterable<E> getItems(CollectionRemoveEvent event) {
return (Iterable<E>) event.getItems();
}
protected void collectionCleared(@SuppressWarnings("unused") CollectionClearEvent event) {
this.clearList(this.list, LIST_VALUES);
}
/**
* synchronize our internal list with the wrapped collection
* and fire the appropriate events
*/
protected void collectionChanged(@SuppressWarnings("unused") CollectionChangeEvent event) {
int size = this.collectionHolder.size();
if (size == 0) {
if (this.list.isEmpty()) {
// no change
} else {
this.clearList(this.list, LIST_VALUES);
}
} else {
if (this.list.isEmpty()) {
this.buildList(size);
this.fireItemsAdded(LIST_VALUES, 0, this.list);
} else {
this.synchronizeList(this.buildSyncList(), this.list, LIST_VALUES);
}
}
}
protected Iterable<? extends E> buildSyncList() {
return this.collectionHolder;
}
@Override
public void toString(StringBuilder sb) {
sb.append(this.list);
}
}
