formatNumberedLines function

String formatNumberedLines(String content, { required int offset, required int limit, })

Formats content like cat -n, starting at the 1-based offset.

Implementation

String formatNumberedLines(String content, {required int offset, required int limit}) {
  final lines = content.split('\n');
  if (lines.length > 1 && lines.last.isEmpty) {
    lines.removeLast();
  }

  final start = offset - 1;
  if (start >= lines.length) {
    return '(The file has ${lines.length} lines; offset $offset is past the end.)';
  }

  final end = (start + limit).clamp(0, lines.length);
  final width = '$end'.length;
  final buffer = StringBuffer();
  for (var index = start; index < end; index++) {
    var line = lines[index];
    if (line.length > _maxLineLength) {
      line = '${line.substring(0, _maxLineLength)}... [line truncated]';
    }
    buffer.writeln('${'${index + 1}'.padLeft(width)}\t$line');
  }
  if (end < lines.length) {
    buffer.writeln('\n(Showing lines ${start + 1}-$end of ${lines.length}. Use offset to read more.)');
  }
  return buffer.toString().trimRight();
}