getBlockMarkers function

List<WordMarker> getBlockMarkers(List<WordMarker> rawMarkers)

Revises the given rawMarkers, merges overlapping or embedded words to one big "block" and returns a list of WordMarkers which represents such "clean" word blocks.
Sorts the given rawMarkers by their index from lowest to highest.

Implementation

List<WordMarker> getBlockMarkers(final List<WordMarker> rawMarkers) {
  final List<WordMarker> revisedMarkers = <WordMarker>[];

  // Sort raw markers by index, ascending.
  // Combine neighboring or overlapping blocks to one large block.
  rawMarkers.sort(sortByIndex);

  /// Counts the number of open blocks.
  /// When a start marker changes this value from 0 to 1, a new block starts.
  /// When an  end marker changes this value from 1 to 0, a block ends.
  /// All other constellations are ignored,
  /// as they mean overlapping or embedded blocks.
  int openCount = 0;
  for (WordMarker rawMarker in rawMarkers) {
    openCount += rawMarker.type == MarkerType.start ? 1 : -1;

    if (openCount < 0) {
      throw Exception('There cannot be less than 0 open blocks');
    }

    // value changes from 0 to 1 by start marker
    if (openCount == 1 && rawMarker.type == MarkerType.start) {
      revisedMarkers.add(rawMarker);
    }

    // value changes from 1 to 0 by end marker
    if (openCount == 0 && rawMarker.type == MarkerType.end) {
      revisedMarkers.add(rawMarker);
    }
  }

  return revisedMarkers;
}