var FORM_MANAGER_CONDITION_SEPARATOR = " AND ";

var FORM_MANAGER_POSSIBILITY_SEPARATOR = " OR ";

var FORM_MANAGER_NAME_VALUE_SEPARATOR = " BEING ";

var FORM_MANAGER_DEPENDS = "DEPENDS ON ";

var FORM_MANAGER_CONFLICTS = "CONFLICTS WITH ";

var FORM_MANAGER_EMPTY = "EMPTY";



function addEvent(el, ev, f) {

  if(el.addEventListener)

    el.addEventListener(ev, f, false);

  else if(el.attachEvent) {

    var t = function() {

      f.apply(el);

    };

    addEvent.events.push({'element': el, 'event': ev, 'handler': f});

    el.attachEvent("on" + ev, t);

  } else

    el['on' + ev] = f;

}



function addEvents(els, evs, f) {

  for(var i = 0; i < els.length; ++i)

    for(var j = 0; j < evs.length; ++j)

      addEvent(els[i], evs[j], f);

}



addEvent.events = [];



if(typeof window.event !== "undefined")

  addEvent(window, "unload", function() {

      for(var i = 0, e = addEvent.events; i < e.length; ++i)

        e[i].element.detachEvent("on" + e[i].event, e[i].handler);

    }

  );



function getRadioValue(el) {

  if(!el.length) return null;

  for(var i = 0; i < el.length; ++i)

    if(el[i].checked) return el[i].value;

  return null;

}



function getSelectValue(el) {

  if(!el.tagName  || el.tagName.toLowerCase() !== "select")

    return null;

  return el.options[el.selectedIndex].value;

}



function isElementValue(el, v) {

  if(v === FORM_MANAGER_EMPTY) v = '';

  return (

    getRadioValue(el) == v ||

    getSelectValue(el) == v ||

    (

      el.tagName &&

      el.tagName.toLowerCase() !== "select" &&

      el.value == v

    )

  );

}



function setupDependencies() {

  var showEl = function() {

    this.style.display = "";

    if(this.parentNode.tagName.toLowerCase() == "label")

      this.parentNode.style.display = "";

  };

  var hideEl = function() {

    this.style.display = "none";

    if(this.parentNode.tagName.toLowerCase() == "label")

      this.parentNode.style.display = "none";

    this.hidden = true;

  };

  var calcDeps = function() {

    for(var i = 0, e = this.elements; i < e.length; ++i) {

      e[i].hidden = false;

      for(var j = 0, f = e[i].className.split(FORM_MANAGER_CONDITION_SEPARATOR); j < f.length; ++j)

        if(f[j].indexOf(FORM_MANAGER_DEPENDS) === 0) {

          for(var k = 0, g = f[j].substr(FORM_MANAGER_DEPENDS.length).split(FORM_MANAGER_POSSIBILITY_SEPARATOR); k < g.length; ++k)

            if(g[k].indexOf(FORM_MANAGER_NAME_VALUE_SEPARATOR) === -1) {

	      if(e[g[k]] && e[g[k]].checked) break;

            else if(k + 1 == g.length)

                e[i].hide();

            } else {

              var n = g[k].split(FORM_MANAGER_NAME_VALUE_SEPARATOR),

                v = n[1];

              n = n[0];

	      if(e[n])

	        if(isElementValue(e[n], v)) break;

	        else if(k + 1 == g.length) e[i].hide();

	    }

        } else if(f[j].indexOf(FORM_MANAGER_CONFLICTS) === 0) {

          if(f[j].indexOf(FORM_MANAGER_NAME_VALUE_SEPARATOR) === -1) {

	    if(e[f[j].substr(FORM_MANAGER_CONFLICTS.length)] && e[f[j].substr(FORM_MANAGER_CONFLICTS.length)].checked) {

              e[i].hide();

              break;

            }

          } else {

            var n = f[j].substr(FORM_MANAGER_CONFLICTS.length).split(FORM_MANAGER_NAME_VALUE_SEPARATOR),

              v = n[1];

            n = n[0];

            if(e[n]) {

              if(isElementValue(e[n], v)) {

                e[i].hide();

                break;

              }

            }

          }

        }

      if(!e[i].hidden) e[i].show();

    }

  };

  var changeHandler = function() {

    this.form.calculateDependencies();

    return true;

  };

  for(var i = 0; i < arguments.length; ++i) {

    for(var j = 0, e = window.document.forms[arguments[i]].elements; j < e.length; ++j) {

      addEvents([e[j]], ["change", "keyup", "focus", "click", "keydown"], changeHandler);

      e[j].hide = hideEl;

      e[j].show = showEl;

    }



    (e = window.document.forms[arguments[i]]).calculateDependencies = calcDeps;

    e.calculateDependencies();

  }

}