/// Compares dotted numeric versions, e.g. "1.0.14" vs "1.0.2".
///
/// Returns a negative number when [a] is older than [b], 0 when they are
/// equivalent, and a positive number when [a] is newer. Missing segments count
/// as 0, so "1.0" and "1.0.0" are equivalent. Returns null when either side
/// cannot be parsed.
int? compareVersions(String? a, String? b) {
  final left = _segments(a);
  final right = _segments(b);
  if (left == null || right == null) return null;

  final length = left.length > right.length ? left.length : right.length;
  for (var i = 0; i < length; i++) {
    final l = i < left.length ? left[i] : 0;
    final r = i < right.length ? right[i] : 0;
    if (l != r) return l - r;
  }
  return 0;
}

/// Whether [current] is strictly older than [minimum].
///
/// Deliberately fails open: a missing or unparseable value returns false, so a
/// backend misconfiguration can never lock users out of the app behind the
/// blocking "you must update" dialog. Equal or newer versions are fine too — a
/// build ahead of the configured minimum is not out of date.
bool isUpdateRequired(String? current, String? minimum) {
  final result = compareVersions(current, minimum);
  if (result == null) return false;
  return result < 0;
}

List<int>? _segments(String? version) {
  if (version == null) return null;
  final trimmed = version.trim();
  if (trimmed.isEmpty) return null;

  // Tolerate build suffixes such as "1.0.14+14" or "1.0.14-beta".
  final core = trimmed.split(RegExp(r'[+\-]')).first;
  final parts = core.split('.');
  final segments = <int>[];
  for (final part in parts) {
    final value = int.tryParse(part.trim());
    if (value == null) return null;
    segments.add(value);
  }
  return segments.isEmpty ? null : segments;
}