firstPositionWord function

Position? firstPositionWord(String? str, String? word, { String? leftOvers = '', bool? continues = false, bool? ignorePunctuation = false, })

Returns the first Position of word in the str.

The default behavior of the function is to count the last substring beginning with white space as a word even if it ends without a whitespace or punctuation mark. leftOvers and continues allows for incremental counting of a string over multiple calls. leftOvers is what remained of a word from a previous string and continues indicates that the string will continue, preventing the count of the last whitespace lead substring.

ignorePunctuation facilitates checking words that include symbols.

Implementation

Position? firstPositionWord(String? str, String? word,
    {String? leftOvers = '',
    bool? continues = false,
    bool? ignorePunctuation = false}) {
  final sb = StringBuffer();
  sb.write(leftOvers);
  final chars = str!.split('');
  var start = 0;
  for (var i = 0; i < chars.length; i++) {
    final ch = chars[i];
    if (ch.isWhiteSpace || (!ignorePunctuation! && ch.isPunctuation)) {
      if (!continues! && sb.isNotEmpty) {
        final sbString = sb.toString();
        if (sbString == word) {
          return Position(start, i - 1);
        }
      }
      start = i + 1;
      sb.clear();
    } else {
      sb.write(ch);
    }
  }
  return null;
}