AR Script: Insert Datetimeoriginal with counter & more

  // v1.0 | Add formatted DateTimeOriginal exif tag and file group counter. Author: glambany@gmail.com
  const GROUP_CNT =       true;  // Enable the incrementing number by file group. Each group is of all files with same filename but different extention.
  const CNT_START =             1;     // Value from where the group counter start counting
  const CNT_STEP =        1;     // Counter incrementing steps.
  const CNT_DIGIT_NB =      3;     // Number of digits, padded with zeros if necessary, that the counter number has
  const DTO =             true;  // Enable adding Datetimeoriginal to the filename
  const DTO_LOOKAROUND =  true;  // Enable the datetimeoriginal LOOKAROUND feature. It looks for a datetimeoriginal in other files around (1 up or down) if the current file hasn't any
  const KEEP_FILEN =        true;  // Enable keeping original filename in addition to the new stuff
  // Filename sep.: Date separator, Date prefix separator, Group counter prefix separator
  const DATE_SEP = "-", DATE_PREFIX = "_", CNT_PREFIX = "_";
  const NEWNAME_FOR_CNT = false;    // Check the new name the files have (modified by previous methods) to detect group of files for the counter. If disabled, use the original filename regardless of what was modified of it

  // Start of the stuff you shouldn't touch, unless you know what you are doing of course
  var final_filename = "";

  // first, try to rename if the file has it's own datetimeoriginal
  if ( get_datetimeoriginal(index) != null )  {
       final_filename = en(item.newBasename + DATE_PREFIX, KEEP_FILEN) + en(get_datetimeoriginal(index, DATE_SEP), DTO) + en(en(CNT_PREFIX, DTO) + zpad(String(counter + CNT_START), CNT_DIGIT_NB), GROUP_CNT);}
  // then, try to find a file around that has a datetimeoriginal, and use it
  else if ( DTO_LOOKAROUND ){
    if        ( index != 0 &&  get_datetimeoriginal(index - 1, DATE_SEP) != null && app.getItem(index - 1).name == item.name ) {
      final_filename = en(item.newBasename + DATE_PREFIX, KEEP_FILEN) + en(get_datetimeoriginal(index - 1, DATE_SEP), DTO) + en(en(CNT_PREFIX, DTO) + zpad(String(counter + CNT_START), CNT_DIGIT_NB), GROUP_CNT);}
    else if ( index != (app.itemcount - 1) &&  get_datetimeoriginal(index + 1, DATE_SEP) != null && app.getItem(index + 1).name == item.name ) {
      final_filename = en(item.newBasename + DATE_PREFIX, KEEP_FILEN) + en(get_datetimeoriginal(index + 1, DATE_SEP), DTO) + en(en(CNT_PREFIX, DTO) + zpad(String(counter + CNT_START), CNT_DIGIT_NB), GROUP_CNT);}
    // can't find a datetimeoriginal around, keep the original filename
    else { final_filename = item.newBasename + en(CNT_PREFIX + zpad(String(counter + CNT_START), CNT_DIGIT_NB), GROUP_CNT); }
  }
  // file doesn't have a datetimeoriginal, and the LOOKAROUND is off, so, keep the original filename
  else { final_filename = item.newBasename + en(CNT_PREFIX + zpad(String(counter + CNT_START), CNT_DIGIT_NB), GROUP_CNT); }

  // Make sure we aren't at the last file
  if ( index != (app.itemcount - 1) ){
    // Increase the counter if the next file has a different name
    if (NEWNAME_FOR_CNT) {
            if( app.getItem(index + 1).newBasename != item.newBasename ){
                counter+= CNT_STEP;}
        }
        else {
            if( app.getItem(index + 1).name != item.name ){
                counter+= CNT_STEP;}
        }
  }

  return final_filename;

// function to get datetimeoriginal from the file in the list with the given index.
function get_datetimeoriginal(idx, sep) {
    var DTO = "";
    var aDate = [];
    //regular expression to extract date from datetimeoriginal (which is a date and a time)
    var reDateTimeSplit = /(\d{4}):(\d{2}):(\d{2})\s(\d{2}):(\d{2}):(\d{2})/;
    //extract datetimeoriginal from file
    DTO = app.getItem(idx).exifToolValue("DateTimeOriginal");

    if ( DTO.length != 0 ) {
        aDate = reDateTimeSplit.exec(DTO);
        return aDate[1] + sep + aDate[2] + sep + aDate[3]
        }
    else{ return null   }
}

// Function that add leading zeros to any string
function zpad(str, nb_digits)
{
    if ( str.length < nb_digits )
        { return (Array(nb_digits - str.length + 1).join('0') + str); }
    else
        { return str; }
}

// return the string if enabled
function en(str, enabled){
  if (enabled) {return str}
  else { return "" }
}