ExtensionMsgBridge

var ExtensionMsgBridge = {
   callbacks: ["null"],
   listen_event:'ext_1',
   send_event:'ext_2',
   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 = ExtensionMsgBridge.callbacks.length;
         ExtensionMsgBridge.callbacks.push(function (response) {
            ExtensionMsgBridge.callbacks[callback_idx] = 'done';
            //alert('Before callback');
            return callback(response);
         });
         set_data(request, "callback", callback_idx);
         document.addEventListener(ExtensionMsgBridge.send_event+"-response", function (event) {
            var node = event.target,
               callback = ExtensionMsgBridge.callbacks[get_data(node, "callback")],
               response = get_data(node, "response");
            if (node.parentNode) node.parentNode.removeChild(node);
            document.removeEventListener(ExtensionMsgBridge.send_event+"-response", arguments.callee, false);
            return callback(response);
         }, false);
      }
      document.documentElement.appendChild(request);
      var sender = document.createEvent("HTMLEvents");
      sender.initEvent(ExtensionMsgBridge.send_event+"-query", true, false);
      return request.dispatchEvent(sender);
   },
   listen_request: function (callback) {
      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(ExtensionMsgBridge.listen_event+"-query", function (event) {
         var node = event.target,
            doc = node.ownerDocument;
         return callback(get_data(node, "data"), doc, function (data) {
            if(!get_data(node, "callback")) {
               if (node.parentNode) node.parentNode.removeChild(node);
               return
            }
            set_data(node, "response", data)
            var listener = doc.createEvent("HTMLEvents");
            listener.initEvent(ExtensionMsgBridge.listen_event+"-response", true, false);
            return node.dispatchEvent(listener);
         });
      }, false, true);
   },
   listen_handler: function (request, sender, callback) {
      console.log('on message '+ExtensionMsgBridge.listen_event, request,sender);
      callback({
         response: 'params:'+JSON.stringify(request)
      });
   }
}



// Set event id for extension content script side
ExtensionMsgBridge.listen_event='ext_side2';
ExtensionMsgBridge.send_event='ext_side1';
ExtensionMsgBridge.listen_request(ExtensionMsgBridge.listen_handler);


/*
// Set event id for injected script side
ExtensionMsgBridge.listen_event='ext_side1';
ExtensionMsgBridge.send_event='ext_side2';
ExtensionMsgBridge.listen_request(ExtensionMsgBridge.listen_handler);
*/