// ==UserScript==

// @name          CVOX

// @description   Generic CVOX Script

// @author        Charles L. Chen

// @include       http://*

// ==/UserScript==



var currentElem = null;

var prevElem = null;

var inputFocused = false;



function getNextLeafNode(){

  prevElem = currentElem;

  if (currentElem == null){

    currentElem = document.body;

  } else {

    while (!currentElem.nextSibling){

    currentElem = currentElem.parentNode;

    if (currentElem == document.body){

      currentElem = null;

      return currentElem;

    }

  }

  currentElem = currentElem.nextSibling;

  }

  while (currentElem.firstChild){

    currentElem = currentElem.firstChild;

  }

  return currentElem;  

}



function getPrevLeafNode(){

  prevElem = currentElem;

  if (currentElem == null){

    currentElem = document.body;

  } else {

    while (!currentElem.previousSibling){

    currentElem = currentElem.parentNode;

    if (currentElem == document.body){

      currentElem = null;

      return currentElem;

    }

  }

  currentElem = currentElem.previousSibling;

  }

  while (currentElem.lastChild){

    currentElem = currentElem.lastChild;

  }

  return currentElem;  

}



function containsText(textStr){

  if (textStr === null){

    return false;

  }

  if (textStr.length < 1){

    return false;

  }

  var myregexp = new RegExp("[a-zA-Z0-9]");

  return myregexp.test(textStr);

}



function getLineage(targetNode){

  var lineage = new Array();

  while (targetNode){

    lineage.push(targetNode);      

    targetNode = targetNode.parentNode;

  }

  lineage.reverse();

  while(lineage.length && !lineage[0].tagName && !lineage[0].nodeValue){

    lineage.shift();

  }

  return lineage;

}



//Compares Lineage A with Lineage B and returns

//the index value in B at which B diverges from A.

//If there is no divergence, the result will be -1.

//Note that if B is the same as A except B has more nodes

//even after A has ended, that is considered a divergence.

//The first node that B has which A does not have will

//be treated as the divergence point.

//

function compareLineages(lina, linb){

  var i = 0;

  while( lina[i] && linb[i] && (lina[i] == linb[i]) ){

    i++;

  }

  if ( !lina[i] && !linb[i] ){

    i = -1;

  }

  return i;

}



function hasTagInLineage(elem, tag){

  var node = elem;

  while(node){

    if (node.tagName && node.tagName == tag){

      return true;

    }

    node = node.parentNode;

  }

  return false;

}



function getText(elem){

  if (elem.tagName && elem.tagName == 'IMG'){

    return elem.alt;

  }

  return elem.textContent;

}



var readingMode = 1; // 0 = detailed, 1 = skim, 2 = headings only



function isSkippable(elem){

  if (hasTagInLineage(elem, 'SCRIPT')){

    return true;

  }

  if (readingMode === 0){

    return false;

  } else if (readingMode == 1){

    if (hasTagInLineage(elem, 'P')){

      return false;

    }

    if (hasTagInLineage(elem, 'H1')){

      return false;

    }

    if (hasTagInLineage(elem, 'H2')){

      return false;

    }

    if (hasTagInLineage(elem, 'H3')){

      return false;

    }

    if (hasTagInLineage(elem, 'H4')){

      return false;

    }

    if (hasTagInLineage(elem, 'H5')){

      return false;

    }

    if (hasTagInLineage(elem, 'H6')){

      return false;

    }

    if (hasTagInLineage(elem, 'OL')){

      return false;

    }

    if (hasTagInLineage(elem, 'UL')){

      return false;

    }

    if (hasTagInLineage(elem, 'DL')){

      return false;

    }

    if (hasTagInLineage(elem, 'BLOCKQUOTE')){

      return false;

    }

    if (hasTagInLineage(elem, 'DIV')){

      return false;

    }

    return true;

  } else if (readingMode == 2) {

    if (hasTagInLineage(elem, 'H1')){

      return false;

    }

    if (hasTagInLineage(elem, 'H2')){

      return false;

    }

    if (hasTagInLineage(elem, 'H3')){

      return false;

    }

    if (hasTagInLineage(elem, 'H4')){

      return false;

    }

    if (hasTagInLineage(elem, 'H5')){

      return false;

    }

    if (hasTagInLineage(elem, 'H6')){

      return false;

    }

    return true;

  }  

}



function getInfoOnCurrentElem(){

  var currentLineage = getLineage(currentElem);

  var divergence = compareLineages(getLineage(prevElem), currentLineage);

  var infoStr = "";

  for (var i=divergence, elem; elem = currentLineage[i]; i++){

    if (elem.tagName){

    if (elem.tagName == 'H1'){

      infoStr = infoStr + 'H 1. ';

    } else if (elem.tagName == 'H2'){

      infoStr = infoStr + 'H 2. ';

    } else if (elem.tagName == 'H3'){

      infoStr = infoStr + 'H 3. ';

    } else if (elem.tagName == 'H4'){

      infoStr = infoStr + 'H 4. ';

    } else if (elem.tagName == 'H5'){

      infoStr = infoStr + 'H 5. ';

    } else if (elem.tagName == 'H6'){

      infoStr = infoStr + 'H 6. ';

    } else if (elem.tagName == 'A'){

      infoStr = infoStr + 'Link. ';

    }

  }

  }

  return infoStr;

}



function readNext(){

  getNextLeafNode();

  var textContent = getText(currentElem);

  while (!containsText(textContent)){

    getNextLeafNode();

    if (currentElem === null){

      speak("End of document", 0, null);

      return false;

    }

    textContent = getText(currentElem);

  }

  if (isSkippable(currentElem)){

    return readNext();

  } else {

    speak(getInfoOnCurrentElem() + ' ' + textContent, 0, null);

    scrollToElem(currentElem);

    return true;

  }

}



function readPrev(){

  getPrevLeafNode();

  var textContent = getText(currentElem);

  while (!containsText(textContent)){

    getPrevLeafNode();

    if (currentElem === null){

      speak("Beginning of document", 0, null);

      return false;

    }

    textContent = getText(currentElem);

  }

  if (isSkippable(currentElem)){

    return readPrev();

  } else {

    speak(getInfoOnCurrentElem() + ' ' + textContent, 0, null);

    scrollToElem(currentElem);

    return true;

  }

}



function scrollToElem(targetNode){

  while (!targetNode.offsetParent){

    targetNode = targetNode.parentNode;

  }

  var left = 0;

  var top = 0;

  while (targetNode.offsetParent) { 

    left += targetNode.offsetLeft;

    top += targetNode.offsetTop; 

    targetNode = targetNode.offsetParent;

  }

  left += targetNode.offsetLeft;

  top += targetNode.offsetTop;

  window.scrollTo(left, top);

}



function speak(textStr, queueMode, paramsArray){

  window.ttsHelper.speak(textStr, queueMode);

  //alert(textStr);

}



function isSpeaking(){

  return window.ttsHelper.isSpeaking();

}



var keepGoing = true;



function autoRead(){  

  if (!isSpeaking()){

    keepGoing = readNext();

  }

  if (keepGoing){

    window.setTimeout(autoRead, 1000);

  }

}



//TODO: Come up with a working escape sequence!

function keyPressHandler(evt){

  var keyCode = evt.keyCode;

  if (inputFocused){

    return true;

  }

  if (keyCode == 97) { // a

    keepGoing = true;

    autoRead();

    return false;

  }  

  if (keyCode == 106) { // j

    readNext();

    return false;

  }

  if (keyCode == 107) { // k

    readPrev();

    return false;

  } 

  if (keyCode == 104) { // h

    readingMode++;

    if (readingMode > 2){

      readingMode = 0;

    }

    if (readingMode == 0){

      speak("All", 0, null);

    } else if (readingMode == 1){

      speak("Quick", 0, null);

    } else if (readingMode == 2){

      speak("Headings", 0, null);

    } 

    return false;

  }   

  return true;

}



function keyDownHandler(evt){

  keepGoing = false;

  window.ttsHelper.stop();

  var keyCode = evt.keyCode;

  if (inputFocused){

    return true;

  }

  if ((keyCode == 32) || (keyCode == 13)) { // space or Enter (G1 enter key does not work)

    var targetElem = currentElem;

    while (targetElem){

	  if (targetElem.tagName == 'A'){

	    document.location = targetElem.href;

      return false;

	  }

	  targetElem = targetElem.parentNode;

	}

    return true;

  }

  return true;

}



function focusHandler(evt){

  if (evt.target.tagName && 

      evt.target.tagName == 'INPUT'){

      inputFocused = true;

      }

  return true;

}



function blurHandler(evt){

  inputFocused = false;

  return true;

}



if (document.location.toString().indexOf('http://www.google.com/m?') === 0){

  // Do nothing, rely on mgws script

} else 

if (document.location.toString().indexOf('http://www.google.com/search?') != 0){

  document.addEventListener('keypress', keyPressHandler, true);

  document.addEventListener('keydown', keyDownHandler, true);

  document.addEventListener('focus', focusHandler, true);

  document.addEventListener('blur', blurHandler, true);

  speak(document.title, 0, null);

}