/**
 * <copyright>
 * 
 * Copyright (c) 2005, 2008 IBM Corporation, Zeligsoft Inc. 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 - Initial API and implementation
 * Zeligsoft - Bug 233004
 * 
 * </copyright>
 * 
 * $Id: SynchRequest.java,v 1.3 2008/08/13 13:24:44 cdamus Exp $
 */
package org.eclipse.egf.core.workspace;

import org.eclipse.emf.ecore.resource.Resource;

/**
 * Abstract definition of a single request to synchronize a workspace
 * resource change with the EMF resource representation in the editing
 * domain.
 * 
 * @author Christian W. Damus (cdamus)
 */
abstract class EGFSynchRequest {

  protected final EGFWorkspaceSynchronizer synch;

  protected final Resource resource;

  /**
   * Initializes me with the synchronizer on whose behalf I perform a
   * synchronization and the resource whose workspace partner is changed.
   * 
   * @param synch
   *          the workspace synchronizer
   * @param resource
   *          the resource that has changed
   */
  EGFSynchRequest(EGFWorkspaceSynchronizer synch, Resource resource) {
    this.synch = synch;
    this.resource = resource;
  }

  /**
   * Performs the synchronization on the synchronizer's behalf.
   * Clients must hold my {@linkplain #getLock() synchronization lock} when
   * calling this method.
   * 
   * @throws InterruptedException
   *           if the job thread is interrupted while
   *           attempting to start a read-only transaction in the editing domain
   * 
   * @see #getLock()
   */
  public final void perform() throws InterruptedException {
    synch.getEditingDomain().runExclusive(new Runnable() {
      public void run() {
        doPerform();
      }
    });
  }

  /**
   * Implemented by subclasses to actually perform their synchronization
   * by delegation to the synchronizer's delegate.
   */
  protected abstract void doPerform();

  /**
   * Queries whether I am disposed. If I am disposed, then I should not
   * be performed. Clients must hold my {@linkplain #getLock() synchronization lock} when calling this method.
   * 
   * @return whether I am disposed
   * 
   * @see #getLock()
   * @since 1.2.1
   */
  protected final boolean isDisposed() {
    return synch.isDisposed();
  }

  /**
   * My synchronization lock, for external synchronization of calls to
   * such methods as {@link #isDisposed()} and {@link #perform()}.
   * Note that this lock is held while the request is being performed, but
   * that this still allows the delegate (if any) to dispose its synchronizer
   * during its invocation.
   * 
   * @return my external lock object
   */
  final Object getLock() {
    return synch;
  }
}