Extesion bridge

// INJECTED SCRIPT
var vkMozExtension = {
   callbacks: [],
   send_request: function (data, callback) { // analogue of chrome.extension.sendRequest
      var set_data = function (el, field, data) {
         if(el.setUserData) {
            el.setUserData(field, data, null);
         } else {
            el.dataset[field] = JSON.stringify(data);
         }
      }
      var get_data = function (el, field) {
         if(el.getUserData) {
            return el.getUserData(field);
         } else {
            return JSON.parse(el.dataset[field]);
         }
      }
      var request = null;
      request = document.createElement("div");
      set_data(request, "data", data);
      if(callback) {
         var callback_idx = vkMozExtension.callbacks.length;
         vkMozExtension.callbacks.push(function (response) {
            vkMozExtension.callbacks[callback_idx] = null;
            //alert('Before callback');
            return callback(response);
         });
         set_data(request, "callback", callback_idx);
         document.addEventListener("mozext-response", function (event) {
            var node = event.target,
               callback = vkMozExtension.callbacks[get_data(node, "callback")],
               response = get_data(node, "response");
            document.documentElement.removeChild(node);
            document.removeEventListener("mozext-response", arguments.callee, false);
            return callback(response);
         }, false);
      }
      document.documentElement.appendChild(request);
      var sender = document.createEvent("HTMLEvents");
      sender.initEvent("mozext-query", true, false);
      return request.dispatchEvent(sender);
   },
   callback: function (response) {
      return alert("response: " + (response && response.toSource ? response.toSource() : response));
   }
}
// USE: vkMozExtension.send_request({download:1,url:'http://vk.me/xxx.jpg',name:'qwe.jpg'},function(){alert(arguments[0])});




// CONTENT SCRIPT
var vkMozExtension = {
   listen_request: function (callback) { // analogue of chrome.extension.onRequest.addListener
      var set_data = function (el, field, data) {
         if(el.setUserData) {
            el.setUserData(field, data, null);
         } else {
            el.dataset[field] = JSON.stringify(data);
         }
      }
      var get_data = function (el, field) {
         if(el.getUserData) {
            return el.getUserData(field);
         } else {
            return JSON.parse(el.dataset[field]);
         }
      }
      return document.addEventListener("mozext-query", function (event) {
         var node = event.target,
            doc = node.ownerDocument;
         return callback(get_data(node, "data"), doc, function (data) {
            if(!get_data(node, "callback")) {
               return doc.documentElement.removeChild(node);
            }
            set_data(node, "response", data)
            var listener = doc.createEvent("HTMLEvents");
            listener.initEvent("mozext-response", true, false);
            return node.dispatchEvent(listener);
         });
      }, false, true);
   },
   callback: function (request, sender, callback) {
      if(request.download) {
         vkDownloadFile(sender.defaultView, request.url, request.name);// function in content/background script
         return setTimeout(function () {
            callback({
               ok: 1
            });
         }, 1000);
      }
      return callback(null);
   }
}
vkMozExtension.listen_request(vkMozExtension.callback);