// $Id: common.js,v 1.4 2003/01/28 22:57:31 don Exp $
// mathquiz.js | 2004-01-20 | Andrew Mathas | version 3.0
// common.js   | 2002-09-29 | Don Taylor    | version 2.0

// 27 Jan 03
// At the moment this is a mix of old code that works
// for NN4 and IE4+ together with new code for browsers
// such as NN6+ that support the Document Object Model.
// It may be possible to improve the code somewhat by
// removing some of the 'eval's.
// Note.  getObject() is only called when isDOM is true.
// - it should be possible to use it for other browser
// types.

var isDOM = false
var layerRef, styleRef
var currentQ, totalQ
var currentRLayer
var answered = new Array()
var correct  = new Array()

function getObject(str) {
  retval = null
  if (document.getElementById) {
    retval = document.getElementById(str).style
  }
  else if (document.layers) {
    retval = document.layers[str]
  }
  else if (document.all) {
    retval = document.all(str).style
  }
  return retval
}

// image arrays
var Images       = "/img/"
var currentImage = new Array()
var untouched    = new Array()
var ticked       = new Array()
var starred      = new Array()
var crossed      = new Array()

// QList will be an array of the expected responses for each question
var QList = new Array()

function init(num) {
  if (navigator.appName=="Netscape" && parseFloat(navigator.appVersion)<5) {
    alert("Your browser version is " + navigator.appVersion +
     ".\nThis quiz is unlikely to work unless your browser version is at least 5.")
  }
  // distinguish between various object models
  if (document.getElementById) {
    layerRef = ""
    styleRef = ".style"
    isDOM = true
  }
  else {
    if (document.layers) {  // e.g. NN4
      layerRef = "document.layers"
      styleRef = ""
    }
    else {
      if (document.all) { // e.g. IE4+
        layerRef = "document.all"
        styleRef = ".style"
      } 
      else {
        alert('Cannot determine object model.  Perhaps the browser version is too old')
      }
    }
  }
  totalQ = num
  currentRLayer = null // Points to the current response layer

  var i
  for ( i = 0; i < num; i++ ) {
    answered[i] = 0     // the number of times the question has been attempted
    correct[i] = false  // whether or not the supplied answer is correct
  }

  // preload the images
  for ( i = 1; i <= num; i++ ) {
    currentImage[i-1] = new Image(31,31)
    currentImage[i-1].src = Images+"border"+i+".gif"
    untouched[i-1] = new Image(31,31)
    untouched[i-1].src = Images+"clear"+i+".gif"
    ticked[i-1] = new Image(31,31)
    ticked[i-1].src = Images+"tick"+i+".gif"
    starred[i-1] = new Image(31,31)
    starred[i-1].src = Images+"star"+i+".gif"
    crossed[i-1] = new Image(31,31)
    crossed[i-1].src = Images+"cross"+i+".gif"
  }
}

// Code to hide/show questions

function showQLayer(newQ) { // newQ is an integer
  hideRLayer()
  if (isDOM) {
    getObject('question'+currentQ).visibility = 'hidden'
    currentQ = newQ
    getObject('question'+currentQ).visibility = 'visible'
  }
  else {
    eval(layerRef + "['question" + currentQ + "']" + styleRef + ".visibility = 'hidden'");
    currentQ = newQ
    eval(layerRef + "['question" + currentQ + "']" + styleRef + ".visibility = 'visible'");
  }
}

// Code to hide/show responses

function hideRLayer() {
  if (currentRLayer != null) {
    if (isDOM)
      currentRLayer.visibility = 'hidden'
    else
      eval(currentRLayer + styleRef + ".visibility = 'hidden'");
  }
}

function showRLayer(tag) {
  hideRLayer()
  if (isDOM) {
    currentRLayer = getObject(tag)
    currentRLayer.visibility = 'visible'
  } 
  else {
    currentRLayer = layerRef+"['question"+currentQ+"']."+layerRef+"['answer"+currentQ+"']."
      +layerRef+"['"+tag+"']"
    eval(currentRLayer + styleRef + ".visibility = 'visible'");
  }
}

// if increment==+1 we find the next questions which has not 
// been correctly answered; if increment==-1 we find the last 
// such question
function nextQuestion (increment) {
  if ( currentQ<0 ) {
    if ( increment==1 ) gotoQuestion(1); 
    else gotoQuestion(totalQ)
  }
  var q = currentQ 
  do {
    q=q+increment
    if (q==0) q=totalQ
    else if (q>totalQ) q=1
  } while (q!=currentQ && correct[q-1] )   
  if (q==currentQ) 
    alert("There are no more unanswered questions")
  else {
    if ( increment==1 ) {
      self.status = 'Question '+q+' is the next unanswered question'
    } else {
      self.status = 'Question '+q+' was the last unanswered question'
    }
    gotoQuestion( q )
  }
}

// nextQuestion + calls to navOver and navOut
function NextQuestion(increment) {
  var q=currentQ+increment
  if (increment==1) { image='nextpage'; msg='Next Question'
  } else { image ='prevpage'; msg='Previous Question' 
  }
  navOut(image)
  nextQuestion(increment)
  setTimeout("navOver(image,msg);", 1000);
}
    
function showProgress() {
  var qnum = currentQ - 1 
  if (currentQ<0) return true // nothing to change in this case
  if (isDOM) {
    var imageref = document.images['progress'+currentQ]
    if (answered[qnum] > 0) {
      if (correct[qnum]) {
        if (answered[qnum] == 1)
          imageref.src = starred[currentQ-1].src
        else
          imageref.src = ticked[currentQ-1].src
      } 
      else
        imageref.src = crossed[currentQ-1].src
    } 
    else
      imageref.src = untouched[currentQ-1].src 
  }
  else {
    var stem = layerRef+"['progress'].document.progress"+currentQ
    if (answered[qnum] > 0) {
      if (correct[qnum]) {
        if (answered[qnum] == 1)
          eval(stem+".src='"+Images+"star"+currentQ+".gif'");
        else
          eval(stem+".src='"+Images+"tick"+currentQ+".gif'");
      }
      else
        eval(stem+".src='"+Images+"cross"+currentQ+".gif'");
    }
    else
      eval(stem+".src='"+Images+"clear"+currentQ+".gif'");
  }
}

function gotoQuestion(qnum) {
  var oldcurrentQ=currentQ
  showProgress()
  showQLayer(qnum)
  if ( oldcurrentQ<0 ) return true;
  if (isDOM)
    document.images['progress'+currentQ].src = currentImage[currentQ-1].src
  else
    eval(layerRef+"['progress'].document.progress"+currentQ+".src='"+Images+"border"+currentQ+".gif'");
}

function checkAnswer() { 
  var qnum = currentQ - 1
  var responsePattern = QList[qnum]
  if (isDOM)
    var formObject = document.forms["Q"+currentQ+"Form"]
  else
    var formObject = eval(layerRef + "['question"+currentQ+"'].document.Q" + currentQ + "Form");

  answered[qnum] += 1

  if (responsePattern.type == "input") {
    if (responsePattern.value == parseFloat(formObject.elements[0].value)) {
      correct[qnum] = true
      showRLayer(eval("'q'+currentQ+'true';"));
    }
    else {
      correct[qnum] = false
      showRLayer(eval("'q'+currentQ+'false';"));
    }
  }
  else if (responsePattern.type == "single") {
    var checkedAnswer = 0
    for  (var i = 0; i < responsePattern.length; i++ ) {
      if (formObject.elements[i].checked) {
        correct[qnum] = responsePattern[i]
        checkedAnswer = i+1
        break
      }
    }
    showRLayer(eval("'q'+currentQ+'response'+checkedAnswer;"));
  }
  else { // type is "multiple"
    var badAnswer = 0
    for  (var i = 0; i < responsePattern.length; i++ ) {
      if (formObject.elements[i].checked != responsePattern[i]) {
        badAnswer = i+1
        break
      }
    }
//    correct[qnum] = (badAnswer == 0)
    if (badAnswer > 0) {
      correct[qnum] = false
      showRLayer(eval("'q'+currentQ+'response'+badAnswer;"));
    }
    else {
      correct[qnum] = true
      showRLayer(eval("'q'+currentQ+'response0';"));
    }
  }
  showProgress()
}

function navOver(name, descr) {
    var highlight_img = Images+"h-"+name+".gif";
    document[name].src = highlight_img;
    self.status = descr;
    return true;
}

function navOut(name) {
    var normal_img = Images+"n-"+name+".gif";
    document[name].src = normal_img;
    self.status = "";
    return true;
}
function menuOver(quiznum, descr) {
    document['quiztitle'+quiznum].src = Images+"red_arrow.gif"
    self.status = descr;
    return true;
}

function menuOut(quiznum) {
    document['quiztitle'+quiznum].src = Images+"arrow.gif"
    self.status = "";
    return true;
}