// CONSTRUCTOR
// Pass in the name of the element, then the names of the lists it depends on
function DynamicOptionList() {
if (arguments.length < 2) { alert("Not enough arguments in DynamicOptionList()"); }
// Name of the list containing dynamic values
this.target = arguments[0];
// Set the lists that this dynamic list depends on
this.dependencies = new Array();
for (var i=1; i<arguments.length; i++) {
this.dependencies[this.dependencies.length] = arguments[i];
}
// The form this list belongs to
this.form = null;
// Place-holder for currently-selected values of dependent select lists
this.dependentValues = new Object();
// Hold default values to be selected for conditions
this.defaultValues = new Object();
// Storage for the dynamic values
this.options = new Object();
// Delimiter between dependent values
this.delimiter = "|";
// Logest string currently a potential options (for Netscape)
this.longestString = "";
// The total number of options that might be displayed, to build dummy options (for Netscape)
this.numberOfOptions = 0;
// Method mappings
this.addOptions = DynamicOptionList_addOptions;
this.populate = DynamicOptionList_populate;
this.setDelimiter = DynamicOptionList_setDelimiter;
this.setDefaultOption = DynamicOptionList_setDefaultOption;
this.printOptions = DynamicOptionList_printOptions;
this.init = DynamicOptionList_init;
}

// Set the delimiter to something other than | when defining condition values
function DynamicOptionList_setDelimiter(val) {
this.delimiter = val;
}

// Set the default option to be selected when the list is painted
function DynamicOptionList_setDefaultOption(condition, val) {
this.defaultValues[condition] = val;
}

// Init call to map the form to the object and populate it
function DynamicOptionList_init(theform) {
this.form = theform;
this.populate();
}

// Add options to the list.
// Pass the condition string, then the list of text/value pairs that populate the list
function DynamicOptionList_addOptions(dependentValue) {
if (typeof this.options[dependentValue] != "object") { this.options[dependentValue] = new Array(); }
for (var i=1; i<arguments.length; i+=2) {
// Keep track of the longest potential string, to draw the option list
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];
}
}

// Print dummy options so Netscape behaves nicely
function DynamicOptionList_printOptions() {
// Only need to write out "dummy" options for Netscape
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);
}
}

// Populate the list
function DynamicOptionList_populate() {
var theform = this.form;
var i,j,obj,obj2;
// Get the current value(s) of all select lists this list depends on
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 this is the first dependent list, just fill in the dependentValues
if (!dependentValuesInitialized) {
dependentValuesInitialized = true;
for (j=0; j<sel.options.length; j++) {
if (sel.options[j].selected) {
this.dependentValues[sel.options[j].value] = true;
}
}
}
// Otherwise, add new options for every existing option
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];

// Store the currently-selected values of the target list to maintain them (in case of multiple select lists)
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; // Clear all target options

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;

// Select the options that were selected before
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;
}
}
}