/* ***** 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 Bookmarks Sync.
 *
 * The Initial Developer of the Original Code is Mozilla.
 * Portions created by the Initial Developer are Copyright (C) 2008
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *  Anant Narayanan <anant@kix.in>
 *
 * 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 ***** */

const EXPORTED_SYMBOLS = ['Tracker'];

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results;
const Cu = Components.utils;

Cu.import("resource://weave/log4moz.js");
Cu.import("resource://weave/constants.js");
Cu.import("resource://weave/util.js");
Cu.import("resource://weave/ext/Observers.js");

/*
 * Trackers are associated with a single engine and deal with
 * listening for changes to their particular data type.
 *
 * There are two things they keep track of:
 * 1) A score, indicating how urgently the engine wants to sync
 * 2) A list of IDs for all the changed items that need to be synced
 * and updating their 'score', indicating how urgently they
 * want to sync.
 *
 */
function Tracker(name) {
  name = name || "Unnamed";
  this.name = this.file = name.toLowerCase();

  this._log = Log4Moz.repository.getLogger("Tracker." + name);
  let level = Svc.Prefs.get("log.logger.engine." + this.name, "Debug");
  this._log.level = Log4Moz.Level[level];

  this._score = 0;
  this._ignored = [];
  this.ignoreAll = false;
  this.changedIDs = {};
  this.loadChangedIDs();
}
Tracker.prototype = {
  /*
   * Score can be called as often as desired to decide which engines to sync
   *
   * Valid values for score:
   * -1: Do not sync unless the user specifically requests it (almost disabled)
   * 0: Nothing has changed
   * 100: Please sync me ASAP!
   *
   * Setting it to other values should (but doesn't currently) throw an exception
   */
  get score() {
    return this._score;
  },

  set score(value) {
    this._score = value;
    Observers.notify("weave:engine:score:updated", this.name);
  },

  // Should be called by service everytime a sync has been done for an engine
  resetScore: function T_resetScore() {
    this._score = 0;
  },

  saveChangedIDs: function T_saveChangedIDs() {
    Utils.delay(function() {
      Utils.jsonSave("changes/" + this.file, this, this.changedIDs);
    }, 1000, this, "_lazySave");
  },

  loadChangedIDs: function T_loadChangedIDs() {
    Utils.jsonLoad("changes/" + this.file, this, function(json) {
      this.changedIDs = json;
    });
  },

  // ignore/unignore specific IDs.  Useful for ignoring items that are
  // being processed, or that shouldn't be synced.
  // But note: not persisted to disk

  ignoreID: function T_ignoreID(id) {
    this.unignoreID(id);
    this._ignored.push(id);
  },

  unignoreID: function T_unignoreID(id) {
    let index = this._ignored.indexOf(id);
    if (index != -1)
      this._ignored.splice(index, 1);
  },

  addChangedID: function addChangedID(id, when) {
    if (!id) {
      this._log.warn("Attempted to add undefined ID to tracker");
      return false;
    }
    if (this.ignoreAll || (id in this._ignored))
      return false;

    // Default to the current time in seconds if no time is provided
    if (when == null)
      when = Math.floor(Date.now() / 1000);

    // Add/update the entry if we have a newer time
    if ((this.changedIDs[id] || -Infinity) < when) {
      this._log.trace("Adding changed ID: " + [id, when]);
      this.changedIDs[id] = when;
      this.saveChangedIDs();
    }
    return true;
  },

  removeChangedID: function T_removeChangedID(id) {
    if (!id) {
      this._log.warn("Attempted to remove undefined ID to tracker");
      return false;
    }
    if (this.ignoreAll || (id in this._ignored))
      return false;
    if (this.changedIDs[id] != null) {
      this._log.trace("Removing changed ID " + id);
      delete this.changedIDs[id];
      this.saveChangedIDs();
    }
    return true;
  },

  clearChangedIDs: function T_clearChangedIDs() {
    this._log.trace("Clearing changed ID list");
    this.changedIDs = {};
    this.saveChangedIDs();
  }
};