srecord noeq GridCodec1(BufferedImage stage0_image) is ToSourceCodec<BufferedImage> {
  settable int rows = 20;

  static GridCodec1 demo() { ret GridCodec1(defaultScreenshot()); }

  // interim data & searches 
  Matrix<Int> stage1_matrix;
  long dataBytes, dataChars;
  Matrix<Matrix<Int>> stage2_grid;
  
  JE_CompressEachElementIndividually<LInt> strat;
  CompressionSearch_AnyType<IJavaExpr, LLInt> search;

  void forward {
    assertNotNull(stage0_image);

    var m = stage1_matrix = imageToMatrix(stage0_image);
    dataBytes = m.nCells()*4+2;
    dataChars = dataBytes*2 + l("lInt(\"\")");
    print("Matrix ~ " + takeFirst_str(60, m));
    print("Trivial comp ~ " + (m.nCells()*8));
    stage2_grid = matrixToMNGrid_rows(m, rows);
    
    // list of lists
    LL<Int> stage3_cells = matrixOfMatricesToListOfLists(stage2_grid);
    
    search = jeCompressionSearch(stage3_cells, dataChars);
    strat = new JE_CompressEachElementIndividually<LInt>()
      .elementCompressionStrategy(-> new JE_RepElement)
      .onCompressionFail(ints -> javaObjectToIJavaExpr(ints);
    
    search.addStrategy(strat);
    
    runProbabilisticForNSeconds(5.0, search);
    print("Search stats. ", strat.stats());
    print(+winner);
  }
  
  void backward {
    todo();
  }
  
  CompressionSearch_AnyType<IJavaExpr, LLInt>.Submission winner() {
    ret search.bestSubmission();
  }
  
  S winnerCode() {
    ret winner == null ?: str(winner.decompressor());
  }
}