/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Android Sync Client.
 *
 * The Initial Developer of the Original Code is
 * the Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2011
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Richard Newman <rnewman@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.gecko.sync;

/**
 * A little class to allow us to maintain a count of extant
 * things (in our case, callbacks that need to fire), and
 * some work that we want done when that count hits 0.
 *
 * @author rnewman
 *
 */
public class DelayedWorkTracker {
  private static final String LOG_TAG = "DelayedWorkTracker";
  protected Runnable workItem = null;
  protected int outstandingCount = 0;

  public int incrementOutstanding() {
    Logger.trace(LOG_TAG, "Incrementing outstanding.");
    synchronized(this) {
      return ++outstandingCount;
    }
  }
  public int decrementOutstanding() {
    Logger.trace(LOG_TAG, "Decrementing outstanding.");
    Runnable job = null;
    int count;
    synchronized(this) {
      if ((count = --outstandingCount) == 0 &&
          workItem != null) {
        job = workItem;
        workItem = null;
      } else {
        return count;
      }
    }
    job.run();
    // In case it's changed.
    return getOutstandingOperations();
  }
  public int getOutstandingOperations() {
    synchronized(this) {
      return outstandingCount;
    }
  }
  public void delayWorkItem(Runnable item) {
    Logger.trace(LOG_TAG, "delayWorkItem.");
    boolean runnableNow = false;
    synchronized(this) {
      Logger.trace(LOG_TAG, "outstandingCount: " + outstandingCount);
      if (outstandingCount == 0) {
        runnableNow = true;
      } else {
        if (workItem != null) {
          throw new IllegalStateException("Work item already set!");
        }
        workItem = item;
      }
    }
    if (runnableNow) {
      Logger.trace(LOG_TAG, "Running item now.");
      item.run();
    }
  }
}