negateRanges function

Ranges negateRanges(Ranges ranges, { int maxValue = 0x10FFFF, int minValue = 0, })

Inverts ranges within the bounds from minValue to maxValue.

Returns a new list with inverted ranges.

Implementation

Ranges negateRanges(
  Ranges ranges, {
  int maxValue = 0x10FFFF,
  int minValue = 0,
}) {
  if (ranges.isEmpty) {
    return [(minValue, maxValue)];
  }

  final normalized = normalizeRanges(ranges);
  final first = normalized.first;
  final last = normalized.last;
  if (first.$1 < minValue) {
    throw ArgumentError(
      'The lowest range bound (${first.$1}) must not be less than minValue ($minValue)',
    );
  }
  if (last.$2 > maxValue) {
    throw ArgumentError(
      'The highest range bound (${last.$2}) must not be greater than maxValue ($maxValue)',
    );
  }

  final result = <Range>[];
  var currentStart = minValue;
  for (int i = 0; i < normalized.length; i++) {
    final range = normalized[i];
    final start = range.$1;
    final end = range.$2;

    if (start > currentStart) {
      result.add((currentStart, start - 1));
    }

    if (end >= currentStart) {
      currentStart = end + 1;
    }
  }

  if (currentStart <= maxValue) {
    result.add((currentStart, maxValue));
  }

  return result;
}