var /* const */ TREETYPE = 0;
  var /* const */ PARENTCODE = 1;
  var /* const */ BOXCODE = 2;
  var /* const */ SPLITCHAR = '_';

  function applyhidden(treeType, hiddenElem)
  {
    var aInputs = document.getElementsByTagName('input');
    var codeCompare;
    var i;
    var hiddenValues = new Array();

    /* needed 'cause when split invoked on empty string, it returns array with 1 element that's empty */

    if (hiddenElem.value > '')
    {
      hiddenValues = hiddenElem.value.split(',')
    }
    else
    {
      return;
    }

    for(i = 0; i < aInputs.length; i++)
    {
      if (aInputs[i].type == 'checkbox' && aInputs[i].id.split(SPLITCHAR)[TREETYPE] == treeType)
      {
        codeCompare = aInputs[i].id.split(SPLITCHAR)[BOXCODE];
        if (arrayIndexOf(hiddenValues, codeCompare) >= 0)
        {
          aInputs[i].checked = true;
        }
      }
    }
  }

  function checksubs(cb)
  {
    var aInputs = document.getElementsByTagName('input');
    var cbState = cb.checked;
    var i, j, k;
    var aToCheck = new Array();
    var aToCheckUp = new Array();
    var treeType = cb.id.split(SPLITCHAR)[TREETYPE];
    var codeStart = cb.id.split(SPLITCHAR)[BOXCODE];
    var codeStartUp = cb.id.split(SPLITCHAR)[PARENTCODE];
    var codeCompare;
    
    var hiddenElem = getHiddenElement(treeType + 'Values');
    var hiddenValues = new Array();

    /* needed 'cause when split invoked on empty string, it returns array with 1 element that's empty */
    if (hiddenElem.value > '')
    {
      hiddenValues = hiddenElem.value.split(',');
    }

    /* 1st, make sure that the element clicked gets added/removed from the hidden input value */
    UpdateHidden(hiddenValues, cbState, codeStart);

    /* going down, initially, we're looking for sub-elements just one level below  
       the one clicked, whose parent code equals the code of the element clicked */
    j = 0;
    for (i = 0; i < aInputs.length; i++)
    {
      /* to qualify the input element, it must be a checkbox and its id must start with the same string as the element passed */
      if (aInputs[i].type == 'checkbox' && aInputs[i].id.split(SPLITCHAR)[TREETYPE] == treeType)
      {
        /* get this element's parent code */
        codeCompare = aInputs[ i ].id.split(SPLITCHAR)[PARENTCODE];
        if (codeCompare == codeStart)
        {
          /* if the clicked-element code matches the parent code of aInputs[i] element we will a) change its state,
             b) added to the list of items changed and c) make sure that hidden input is updated */
          aInputs[i].checked = cbState;
          aToCheck[j++] = aInputs[i];
          UpdateHidden(hiddenValues, cbState, aInputs[i].id.split(SPLITCHAR)[BOXCODE]);
        }
      }
    }
    
    j = 0;
    while (aToCheck.length > 0)
    {
      /* if any sub-elements were found earlier, we need to see if they "parent" any themselves
         for that, we will traverse array aToCheck, populated earlier. Any sub-element found here
         will also be added to the bottom of this array so the while-loop will continue until
         all aToCheck added before and all aToCheck added here have been processed */
      codeStart = aToCheck[j].id.split(SPLITCHAR)[BOXCODE];   
      for (i = 0; i < aInputs.length; i++)
      {
        if (aInputs[i].type == 'checkbox' && aInputs[i].id.split(SPLITCHAR)[TREETYPE] == treeType)
        {
          /* again, is this element's parent code equal to the code for aToCheck element? */
          codeCompare = aInputs[i].id.split(SPLITCHAR)[PARENTCODE];

          if (codeCompare == codeStart)
          {
            aInputs[i].checked = cbState;
            aToCheck[aToCheck.length] = aInputs[i];
            UpdateHidden(hiddenValues, cbState, aInputs[i].id.split(SPLITCHAR)[BOXCODE]);
          }
        }
      }

      j++;
      if (j >= aToCheck.length)
      {
        break;
      }
    }

    /* walk up - ONLY if cbState is checked. unchecking should not be propagated up */
    if (cbState)
    {
      /* in this "paragraph", we're looking for element "above" the one that was clicked, the elements
         above are those whose code matches the parent code of the clicked element */
      j = 0;
      for (i = 0; i < aInputs.length; i++)
      {
        if (aInputs[i].type == 'checkbox' && aInputs[i].id.split(SPLITCHAR)[TREETYPE] == treeType)
        {
          codeCompare = aInputs[i].id.split(SPLITCHAR)[BOXCODE];

          if (codeCompare == codeStartUp)
          {
            aInputs[i].checked = cbState;
            aToCheckUp[j++] = aInputs[i];
            UpdateHidden(hiddenValues, cbState, codeCompare);
          }
        }
      }

      /* this loop is similar to the one walking down and it, basically, continues the climb */  
      j = 0;
      while (aToCheckUp.length > 0)
      {
        codeStartUp = aToCheckUp[j].id.split(SPLITCHAR)[PARENTCODE];
        for (i = 0; i < aInputs.length; i++)
        {
          if (aInputs[i].type == 'checkbox' && aInputs[i].id.split(SPLITCHAR)[TREETYPE] == treeType)
          {
            codeCompare = aInputs[i].id.split(SPLITCHAR)[BOXCODE];
            if (codeCompare == codeStartUp)
            {
              aInputs[i].checked = cbState;
              aToCheckUp[aToCheckUp.length] = aInputs[i];
              UpdateHidden(hiddenValues, cbState, codeCompare);
            }
          }
        }

       j++;
       if (j >= aToCheckUp.length)
         break;
      }
    }

    /* make sure that string is sorted properly */
    hiddenValues.sort(sortNumber);
    /* ... and write the string array back to the input element */
    hiddenElem.value = hiddenValues.toString();
  }

  function getHiddenElement(elemID)
  {
    var aElems = document.getElementsByTagName('input');
    var i;
    var ret = null;

    for (i = 0; i < aElems.length; i++)
    {
      if (aElems[i].id.indexOf(elemID) >= 0)
      {
        ret = aElems[i];
        break;
      }
    }
    return ret;
  }

  function arrayIndexOf(arr, value)
  {
    var ret = -1;
    for (i = 0; i < arr.length; i++)
    {
      if (arr[i] == value)
      {
        ret = i;
        break;
      }
    }
    return ret;
  }
  function UpdateHidden(arr, state, code)
  {
    var k = arrayIndexOf(arr, code);
    if (state && k < 0)     // needs to be added to array
    {
      arr[arr.length] = code;
    }
    if (! state && k >= 0)  // exists but needs to be removed
    {
      arr.splice(k, 1);
    }
  }

  function sortNumber(a, b)
  {
    return a - b
  }

  function getElementByPartialName(elemID, elemType)
  {
    var i;
    var ret = null;
    var aElems = document.getElementsByTagName(elemType);

    for (i = 0; i < aElems.length; i++)
    {
      if (aElems[i].id.indexOf(elemID) >= 0)
      {
        ret = aElems[i];
        break;
      }
    }
    return ret;
  }