/*****************************************************************************
 * Copyright (c) 2013, 2017 CEA LIST and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *   CEA LIST - Initial API and implementation
 *   Christian W. Damus (CEA) - bug 432813
 *
 *****************************************************************************/
package org.eclipse.papyrus.cdo.core.resource;

import java.util.Collections;
import java.util.Set;

import org.eclipse.core.commands.operations.IOperationHistory;
import org.eclipse.core.commands.operations.IUndoContext;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.osgi.util.NLS;
import org.eclipse.papyrus.cdo.internal.core.l10n.Messages;

import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;


/**
 * A CDO-specific undo context that records at the level of objects the scope of what is affected by an operation.
 */
public final class CDOUndoContext implements IUndoContext {

	private static CDOUndoContext ALL_CDO = new CDOUndoContext();

	private final Set<EObject> affectedObjects;

	private String cachedLabel;

	/**
	 * Initializes me with a non-empty aggregate of affected objects.
	 *
	 * @param affectedObjects
	 *            the affected objects to record
	 *
	 * @throws IllegalArgumentException
	 *             if the {@code affectedObjects} is empty
	 */
	public CDOUndoContext(Iterable<? extends EObject> affectedObjects) {
		super();

		if (Iterables.isEmpty(affectedObjects)) {
			throw new IllegalArgumentException("affectedObjects is empty"); //$NON-NLS-1$
		}

		this.affectedObjects = ImmutableSet.copyOf(affectedObjects);
	}

	private CDOUndoContext() {
		super();

		this.affectedObjects = Collections.<EObject> emptySet();
	}

	/**
	 * Flushes all {@code CDOUndoContext}s from the specified operation {@code history}.
	 *
	 * @param history
	 *            a history to flush
	 */
	public static void flushAll(IOperationHistory history) {
		history.dispose(ALL_CDO, true, true, true);
	}

	/**
	 * Obtains an immutable set of the objects affected by the operation.
	 *
	 * @return my affected objects. This set is immutable
	 */
	public Set<EObject> getAffectedObjects() {
		return affectedObjects;
	}

	@Override
	public boolean matches(IUndoContext context) {
		return (context == ALL_CDO) || (context instanceof CDOUndoContext) && !Sets.intersection(getAffectedObjects(), ((CDOUndoContext) context).getAffectedObjects()).isEmpty();
	}

	@Override
	public String getLabel() {
		if (cachedLabel == null) {
			StringBuilder buf = new StringBuilder();
			Joiner.on(", ").appendTo(buf, Iterables.limit(affectedObjects, 3)); //$NON-NLS-1$
			if (affectedObjects.size() > 3) {
				buf.append(", ..."); //$NON-NLS-1$
			}

			cachedLabel = NLS.bind(Messages.CDOUndoContext_0, buf);
		}

		return cachedLabel;
	}

	@Override
	public String toString() {
		return getLabel();
	}
}