// ===================================================================
// Author: Matt Kruse <matt@mattkruse.com>
// WWW: http://www.mattkruse.com/
//
// NOTICE: You may use this code for any purpose, commercial or
// private, without any further permission from the author. You may
// remove this notice from your final code if you wish, however it is
// appreciated by the author if at least my web site address is kept.
//
// You may *NOT* re-distribute this code in any way except through its
// use. That means, you can include it in your product, or your web
// site, or any other form where the code is actually being used. You
// may not put the plain javascript up on your site for download or
// include it in your javascript libraries for download. 
// If you wish to share this code with others, please just point them
// to the URL instead.
// Please DO NOT link directly to my .js files from your site. Copy
// the files to your server and use them there. Thank you.
// ===================================================================

function DynamicOptionList()
{
  if(arguments.length < 2)
  {
    alert("Not enough arguments in DynamicOptionList()");
  }
  this.target = arguments[0];
  this.dependencies = new Array();
  for(var i=1;i<arguments.length;i++)
  {
    this.dependencies[this.dependencies.length] = arguments[i];
  }
  this.form = null;
  this.dependentValues = new Object();
  this.defaultValues = new Object();
  this.options = new Object();
  this.delimiter = "|";
  this.longestString = "";
  this.numberOfOptions = 0;
  this.addOptions = DynamicOptionList_addOptions;
  this.populate = DynamicOptionList_populate;
  this.setDelimiter = DynamicOptionList_setDelimiter;
  this.setDefaultOption = DynamicOptionList_setDefaultOption;
  this.printOptions = DynamicOptionList_printOptions;
  this.init = DynamicOptionList_init;
}

function DynamicOptionList_setDelimiter(val)
{
  this.delimiter = val;
}

function DynamicOptionList_setDefaultOption(condition, val)
{
  this.defaultValues[condition] = val;
}

function DynamicOptionList_init(theform)
{
  this.form = theform;this.populate();
}

function DynamicOptionList_addOptions(dependentValue)
{
  if(typeof this.options[dependentValue] != "object")
  {
    this.options[dependentValue] = new Array();
  }
  for(var i=1;i<arguments.length;i+=2)
  {
    if(arguments[i].length > this.longestString.length)
    {
      this.longestString = arguments[i];
    }
    this.numberOfOptions++;
    this.options[dependentValue][this.options[dependentValue].length] = 
      arguments[i];
    this.options[dependentValue][this.options[dependentValue].length] = 
      arguments[i+1];
  }
}

function DynamicOptionList_printOptions()
{
  if((navigator.appName == 'Netscape') &&(parseInt(navigator.appVersion) <= 4))
  {
    var ret = "";
    for(var i=0;i<this.numberOfOptions;i++)
    {
      ret += "<OPTION>";
    }
    ret += "<OPTION>";

    for(var i=0;i<this.longestString.length;i++)
    {
      ret += "_";
    }
    document.writeln(ret);
  }
}

function DynamicOptionList_populate()
{
  var theform = this.form;
  var i,j,obj,obj2;
  this.dependentValues = new Object;
  var dependentValuesInitialized = false;
  for(i=0;i<this.dependencies.length;i++)
  {
    var sel = theform[this.dependencies[i]];
    var selName = sel.name;
    if(!dependentValuesInitialized)
    {
      dependentValuesInitialized = true;
      for(j=0;j<sel.options.length;j++)
      {
        if(sel.options[j].selected)
        {
          this.dependentValues[sel.options[j].value] = true;
        }
      }
    }
    else
    {
      var tmpList = new Object();
      var newList = new Object();
      for(j=0;j<sel.options.length;j++)
      {
        if(sel.options[j].selected)
        {
          tmpList[sel.options[j].value] = true;
        }
      }
      for(obj in this.dependentValues)
      {
        for(obj2 in tmpList)
        {
          newList[obj + this.delimiter + obj2] = true;
        }
      }
      this.dependentValues = newList;
    }
  }
  var targetSel = theform[this.target];
  var targetSelected = new Object();
  for(i=0;i<targetSel.options.length;i++)
  {
    if(targetSel.options[i].selected)
    {
      targetSelected[targetSel.options[i].value] = true;
    }
  }
  targetSel.options.length = 0;
  for(i in this.dependentValues)
  {
    if(typeof this.options[i] == "object")
    {
      var o = this.options[i];
      for(j=0;j<o.length;j+=2)
      {
        var text = o[j];
        var val = o[j+1];
        targetSel.options[targetSel.options.length] = new Option(text, val, false, false);
        if(this.defaultValues[i] == val)
        {
          targetSelected[val] = true;
        }
      }
    }
  }
  targetSel.selectedIndex=-1;
  for(i=0;i<targetSel.options.length;i++)
  {
    if(targetSelected[targetSel.options[i].value] != null && 
       targetSelected[targetSel.options[i].value]==true)
    {
      targetSel.options[i].selected = true;
    }
  }
}