previousWordRangeFromReader function

({int end, int start})? previousWordRangeFromReader(
  1. int length,
  2. int offset, {
  3. required GraphemePredicate isWord,
  4. required GraphemeReader graphemeAt,
})

Implementation

({int start, int end})? previousWordRangeFromReader(
  int length,
  int offset, {
  required GraphemePredicate isWord,
  required GraphemeReader graphemeAt,
}) {
  if (offset <= 0 || length <= 0) {
    return null;
  }

  var position = offset.clamp(0, length) - 1;
  while (position >= 0) {
    final grapheme = graphemeAt(position);
    if (grapheme != null && isWord(grapheme)) {
      break;
    }
    position--;
  }
  if (position < 0) {
    return null;
  }

  final end = position + 1;
  while (position >= 0) {
    final grapheme = graphemeAt(position);
    if (grapheme == null || !isWord(grapheme)) {
      break;
    }
    position--;
  }
  return (start: position + 1, end: end);
}