get_disambiguator method

String get_disambiguator(Move move)

This function is used to uniquely identify ambiguous moves.

Implementation

String get_disambiguator(Move move) {
  var moves = generate_moves();

  var from = move.from;
  var to = move.to;
  var piece = move.piece;

  var ambiguities = 0;
  var same_rank = 0;
  var same_file = 0;

  for (var i = 0, len = moves.length; i < len; i++) {
    var ambig_from = moves[i].from;
    var ambig_to = moves[i].to;
    var ambig_piece = moves[i].piece;

    /* if a move of the same piece type ends on the same to square, we'll
     * need to add a disambiguator to the algebraic notation
     */
    if (piece == ambig_piece && from != ambig_from && to == ambig_to) {
      ambiguities++;

      if (rank(from) == rank(ambig_from)) {
        same_rank++;
      }

      if (file(from) == file(ambig_from)) {
        same_file++;
      }
    }
  }

  if (ambiguities > 0) {
    /* if there exists a similar moving piece on the same rank and file as
     * the move in question, use the square as the disambiguator
     */
    if (same_rank > 0 && same_file > 0) {
      return algebraic(from);
    } /* if the moving piece rests on the same file, use the rank symbol as the
     * disambiguator
     */
    else if (same_file > 0) {
      return algebraic(from)[1];
    } /* else use the file symbol */
    else {
      return algebraic(from)[0];
    }
  }

  return '';
}