// thread-safe except for analysis output fields
sclass ChessPieceRecognizer {
  MultiMap<S, ChessPieceProfile1> profiles;
  double magicCombineFactor = 0.0012589254117941495;
  int version = 1;
  
  // for analysis
  transient Pair<Pair<S, ChessPieceProfile1>, Double> best, runnerUp;
  
  void load {
    long time = sysNow();
    profiles = agiBlue_chessPieceProfiles(agiBlue_chessPieceImages_loadedMultiMap(), +version);
    compact();
    done2("Loading " + n2(l(profiles), "piece profile"), time);
  }
  
  void compact {
    int n = l(profiles);
    profiles = uniquifyMultiMapValues(profiles);
    int m = l(profiles);
    if (m < n)
      print("Compacted ChessPieceRecognizer " + n + " => " + m);
    internByteArrayField sideProfile(values(profiles));
  }
  
  Pair<S, Double> recognize(BufferedImage img) {
    ChessPieceProfile1 profile = chessOCR_pieceProfileFromRawImage_1(img);
    new Lowest_withRunnerUp<Pair<S, ChessPieceProfile1>> lowest;
    
    for (unpair S piece, ChessPieceProfile1 p : multiMapToPairs(profiles)) {
      float sideProfileDiff = floatRatio(byteArraysTotalDiff(profile.sideProfile, p.sideProfile), l(p.sideProfile));
      float fillGradeDiff = abs(profile.fillGrade-p.fillGrade);
      double score = magicCombine(sideProfileDiff, fillGradeDiff);
      lowest.put(pair(piece, p), score);
    }
    best = lowest.pair();
    runnerUp = lowest.runnerUpPair();
    ret !lowest.has() ? null : pair(pairA(lowest!), errorToPercent(lowest.score()));
  }
  
  // for humans
  double errorToPercent(double d) {
    ret 100-d;
  }
  
  double magicCombine(double sideProfileScore, double fillGradeScore) {
    double sum = sideProfileScore+fillGradeScore/magicCombineFactor;
    //print("magicCombine " + sideProfileScore + "*" + magicCombineFactor + "+" + fillGradeScore + " = " + sum);
    ret sum;
  }
  
  toString {
    ret shortClassName(this) + "(v" + version + ", " + nProfiles(l(profiles)) + ")";
  }
  
  ChessOCR_RecognizedBoard recognizeBoard(BufferedImage board) {
    new ChessOCR_RecognizedBoard out;
    LL<BufferedImage> squareImages = bufferedImageMNGrid(board, 8, 8);
    out.pieces = new L;
    for (BufferedImage img : concatLists(squareImages))
      out.pieces.add(recognize(img));
    out.score = doubleAvg(pairsB(out.pieces));
    out.fen = chess_makeFEN(listToChunks(8, pairsA(out.pieces)));
    ret out;
  }
}