common/plugins/org.eclipse.jpt.common.utility/src/org/eclipse/jpt/common/utility/internal/model/value/SortedListValueModelAdapter.java

/*******************************************************************************
 * Copyright (c) 2007, 2015 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.Collections;
import java.util.Comparator;
import java.util.List;

import org.eclipse.jpt.common.utility.internal.Range;
import org.eclipse.jpt.common.utility.internal.collection.CollectionTools;
import org.eclipse.jpt.common.utility.internal.collection.ListTools;
import org.eclipse.jpt.common.utility.model.event.CollectionAddEvent;
import org.eclipse.jpt.common.utility.model.value.CollectionValueModel;

/**
 * An adapter that allows us to make a {@link CollectionValueModel}
 * (or {@link org.eclipse.jpt.common.utility.model.value.ListValueModel ListValueModel})
 * behave like a {@link org.eclipse.jpt.common.utility.model.value.ListValueModel ListValueModel}
 * that keeps its contents sorted and notifies listeners appropriately.
 * <p>
 * The {@link Comparator} can be changed at any time; allowing the same
 * adapter to be used with different sort criteria (e.g. when the user
 * wants to sort a list of files first by name, then by date, then by size).
 * <p>
 * <strong>NB:</strong> Since we only listen to the wrapped collection when we have
 * listeners ourselves and we can only stay in sync 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, client objects will also be listeners.
 * 
 * @see SortedListValueModelWrapper
 */
public class SortedListValueModelAdapter<E>
	extends CollectionListValueModelAdapter<E>
{
	/**
	 * A comparator used for sorting the elements;
	 * if it is null, we use "natural ordering".
	 */
	protected Comparator<E> comparator;


	// ********** constructors **********

	/**
	 * Wrap the specified collection value model and sort its contents
	 * using the specified comparator.
	 */
	public SortedListValueModelAdapter(CollectionValueModel<? extends E> collectionHolder, Comparator<E> comparator) {
		super(collectionHolder);
		this.comparator = comparator;
	}

	/**
	 * Wrap the specified collection value model and sort its contents
	 * based on the elements' "natural ordering".
	 */
	public SortedListValueModelAdapter(CollectionValueModel<? extends E> collectionHolder) {
		this(collectionHolder, null);
	}


	// ********** accessors **********

	public void setComparator(Comparator<E> comparator) {
		this.comparator = comparator;
		this.sortList();
	}


	// ********** behavior **********

	/**
	 * Sort the internal list before the superclass
	 * sends out change notification.
	 */
	@Override
	protected void buildList(int size) {
		super.buildList(size);
		Collections.sort(this.list, this.comparator);
	}

	/**
	 * Sort the list after adding the items.
	 */
	@Override
	protected void itemsAdded(CollectionAddEvent event) {
		@SuppressWarnings("unchecked")
		ArrayList<E> newList = (ArrayList<E>) this.list.clone();
		newList.ensureCapacity(newList.size() + event.getItemsSize());
		CollectionTools.addAll(newList, this.getItems(event));
		Collections.sort(newList, this.comparator);
		this.synchronizeList(newList, this.list, LIST_VALUES);
	}

	@Override
	protected Iterable<? extends E> buildSyncList() {
		return CollectionTools.treeSet(this.collectionHolder, this.comparator, this.collectionHolder.size());
	}

	/**
	 * sort the list and notify our listeners, if necessary;
	 */
	protected void sortList() {
		// save the unsorted state of the sorted list so we can minimize the number of "replaced" items
		@SuppressWarnings("unchecked")
		ArrayList<E> unsortedList = (ArrayList<E>) this.list.clone();
		Collections.sort(this.list, this.comparator);
		Range diffRange = ListTools.identityDifferenceRange(unsortedList, this.list);
		if (diffRange != null) {
			List<E> unsortedItems = unsortedList.subList(diffRange.start, diffRange.end + 1);
			List<E> sortedItems = this.list.subList(diffRange.start, diffRange.end + 1);
			this.fireItemsReplaced(LIST_VALUES, diffRange.start, sortedItems, unsortedItems);
		}
	}
}