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var FileWatch = function(filename, duration) {
  this.file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsILocalFile);
  this.file.initWithPath(filename);
  this.duration = duration;
};

FileWatch.prototype = {
  iid: null,
  lastTime: null,
  watch: function() {
    this.lastTime = (new Date()).getTime();
    var self = this;
    this.iid = setInterval(function() { self.watchFile(); }, this.duration * 1000);
  },
  watchFile: function() {
    if (this.file.lastModifiedTime - this.lastTime > 0) {
      this.log("modified");
    }

    this.lastTime = (new Date()).getTime();
  },
  log: function(message) {
    Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService).logStringMessage(message);
  },
  unwatch: function() {
    clearInterval(this.iid);
  }
};