/* -*- Mode: Javascript; indent-tabs-mode:nil; js-indent-level: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80: */

/*************************************************************
 *
 *  MathJax/extensions/AssistiveMML.js
 *  
 *  Implements an extension that inserts hidden MathML into the
 *  page for screen readers or other asistive technology.
 *  
 *  ---------------------------------------------------------------------
 *  
 *  Copyright (c) 2015 The MathJax Consortium
 * 
 *  Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

(function (AJAX,CALLBACK,HUB,HTML) {

  var AssistiveMML = MathJax.Extension["AssistiveMML"] = {
    version: "2.6",

    //
    //  For each jax in the state, look up the frame.
    //  If the jax doesn't use NativeMML and hasn't already been handled:
    //    Get the MathML for the jax, taking resets into account.
    //    Add a data-mathml attribute to the frame, and
    //    Create a span that is not visible on screen and put the MathML in it,
    //      and add it to the frame.
    //  When all the jax are processed, call the callback.
    //
    HandleMML: function (state) {
      var m = state.jax.length, jax, mml, frame, span;
      while (state.i < m) {
        jax = state.jax[state.i];
        frame = document.getElementById(jax.inputID+"-Frame");
        if (jax.outputJax !== "NativeMML" && frame && !frame.getAttribute("data-mathml")) {
          try {
            mml = jax.root.toMathML("").replace(/\n */g,"").replace(/<!--.*?-->/g,"");
          } catch (err) {
            if (!err.restart) throw err; // an actual error
            return MathJax.Callback.After(["HandleMML",this,state],err.restart);
          }
          frame.setAttribute("data-mathml",mml);
	  span = HTML.Element("span",{
	    isMathJax: true,
	    style:{
              position:"absolute",
              clip: (HUB.Browser.isMSIE && (document.documentMode||0) < 8 ?
                     "rect(1px 1px 1px 1px)" : "rect(1px, 1px, 1px, 1px)"),
              padding: "1 0 0 0",
              border: "0",
              height: "1px",
              width: "1px",
              overflow: "hidden",
              display:"block"
            }
	  });
	  span.innerHTML = mml;
	  frame.appendChild(span);
        }
        state.i++;
      }
      state.callback();
    },
    
    //
    //  The hook for the End Math signal.
    //  This sets up a state object that lists the jax and index into the jax,
    //    and a dummy callback that is used to synchronizing with MathJax.
    //    It will be called when the jax are all processed, and that will
    //    let the MathJax queue continue (it will block until then).
    //
    EndMathHook: function (node) {
      var state = {
        jax: HUB.getAllJax(node), i: 0,
        callback: MathJax.Callback(function () {
          console.log("MathML time: "+((new Date().getTime())-state.start));
        }),
        start: new Date().getTime()
      };
      this.HandleMML(state);
      return state.callback;
    }
    
  };

  //
  //  Call the hook when math has been processed.
  //
  HUB.Register.MessageHook("End Math",function (msg) {AssistiveMML.EndMathHook(msg[1])});

  HUB.Startup.signal.Post("AssistiveMML Ready");

})(MathJax.Ajax,MathJax.Callback,MathJax.Hub,MathJax.HTML);

//
//  Make sure the toMathML extension is loaded before we signal
//  the load complete for this extension.
//
MathJax.Callback.Queue(
  ["Require",MathJax.Ajax,"[MathJax]/extensions/toMathML.js"],
  ["loadComplete",MathJax.Ajax,"[MathJax]/extensions/AssistiveMML.js"]
);