betweenResult method

(String, String?)? betweenResult(String start, String end, { bool endOptional = false, bool trim = true, })

Extracts content between start and end delimiters.

Returns a tuple of (content between delimiters, remaining string after the closing delimiter). The second element is an empty string if nothing follows the closing delimiter.

Design: uses indexOf for start (first occurrence) and lastIndexOf for end (last occurrence). This intentionally returns the outermost match, so nested delimiters are included in the content: '(a(test)b)'.betweenResult('(',')') → ('a(test)b', '').

If you need the first balanced pair instead, use between() which uses indexOf for both delimiters.

Implementation

(String, String?)? betweenResult(
  String start,
  String end, {
  bool endOptional = false,
  bool trim = true,
}) {
  if (isEmpty || start.isEmpty || end.isEmpty) return null;
  final int startIndex = indexOf(start);
  if (startIndex == -1) {
    return null;
  }

  final int endIndex = lastIndexOf(end);
  if (endIndex == -1) {
    // If end is not found and it's optional, return the tail after start.
    if (endOptional) {
      final String content = substringSafe(startIndex + start.length);
      final String finalContent = trim ? content.trim() : content;
      return finalContent.isEmpty ? null : (finalContent, null);
    }
    return null;
  }

  if (startIndex >= endIndex || (startIndex + start.length) > endIndex) {
    return null;
  }

  final String found = substringSafe(startIndex + start.length, endIndex);

  final String remaining = substringSafe(0, startIndex) + substringSafe(endIndex + end.length);

  final String finalFound = trim ? found.trim() : found;

  final String finalRemaining = trim
      ? remaining.replaceAll(RegExp(r'\s+'), ' ').trim()
      : remaining;

  return (finalFound, finalRemaining.isEmpty ? '' : finalRemaining);
}