// type parameter is rect + FEN

// not persistable

sclass ChessOCR_TwoStageRecognizer extends SteppableAndBest<Pair<Rect, S>> {

  replace Segmenter with IF1<BufferedImage, L<Rect>>.

  // input

  BufferedImage inputImage;

  Iterator<? extends Segmenter> segmenterStream;

  ChessPieceRecognizer pieceRecognizer;

  bool verbose;

  // internal

  L<Rect> rectQueue = syncLinkedList();

  new Set<Rect> rectsTried;

  *() {}

  *(ChessPieceRecognizer *pieceRecognizer, BufferedImage *inputImage, Iterator<? extends Segmenter> *segmenterStream) {}

  public bool step() {

    if (nempty(rectQueue))

      ret true with tryRect(popFirst(rectQueue));

    if (segmenterStream.hasNext()) {

      Segmenter seg = segmenterStream.next();

      if (seg == null) true;

      L<Rect> rects = seg.get(inputImage);

      addAll(rectQueue, rects);

      if (verbose) print("Segmenter " + seg + " returned: " + rects);

      true;

    }

    false;

  }

  // returns true if rect not seen before

  bool tryRect(Rect r) {

    r = rectSetHeightToWidth(r); // square it

    if (!rectsTried.add(r)) false; // seen

    BufferedImage board = clipBufferedImage(inputImage, r);

    S fen, double score = unpair chessOCR_recognizeBoard_FENAndScore(board, pieceRecognizer);

    if (verbose) print("Score " + score + " for rect: " + r);

    best.put(pair(r, fen), score);

    true;

  }

  void verbose(bool verbose) {

    best.verboseNewBest = this.verbose = verbose;

  }

  Rect bestBoardLocation() { ret pairA(best!); }

  Pair<Rect, Double> boardLocationAndScore() { ret pair(pairA(best!), score()); }

}