// has a rectangular window (visionW*visionH)

// walking range per frame is a circle with radius "range"

sclass G22Walker {

  // configuration (set)

  int range = 1; // how far we can walk in each frame

  double roundingPolicy = .9; // for making the range circle (between 0 and 1)

  int visionW = 3, visionH = 3; // window rectangle size (both should be odd)

  // current position (set/get)

  Pt position; // current position (center), not null

  // the ideal image it is looking for (set/get)

  byte[] rememberedImage; // size visionW*visionH

  // status variables (read)

  bool stuck; // can neither stay nor move anywhere for some reason

  int guessWork; // how many "optimal" new positions we chose from

  void move(IBWImage image) {

    stuck = false;

    guessWork = 0;

    // How far can I move until I hit the image's borders

    Rect movement1 = rectFromPoints(visionW/2, visionH/2,

      image.getWidth()-(visionW+1)/2, (visionH+1)/2);

    // How far can I walk in one frame

    Rect movement2 = rectAroundPt(position, range*2+1);

    Rect movement = intersectRects(movement1, movement2);

    if (empty(movement)) ret with set stuck;

    printVars(+movement, +movement1, +movement2);

    if (rememberedImage == null)

      ret with rememberImage(image);

    Rect r = window_uncropped();

    new MultiBest<Pt> bestPositions;

    int mx1 = movement.x1(), mx2 = movement.x2();

    int my1 = movement.y1(), my2 = movement.y2();

    for (int y = my1; y < my2; y++)

      for (int x = mx1; x < mx2; x++) {

        var newPos = pt(x, y);

        bestPositions.put(newPos, scorePosition(newPos, image));

      }

    var best = bestPositions!;

    guessWork = l(best);

    position = random(best);

    // It's actually a question how often we grab a fresh image.

    // For now, every time.

    rememberImage(image);

  }

  // only works when we already have a rememberedImage

  double scorePosition(Pt pos, IBWImage image) {

    int vx = pos.x-visionW, vy = pos.y-visionH, i = 0;

    int diff = 0;

    for y to visionH:

      for x to visionW:

        diff += abs(ubyteToInt(rememberedImage[i++])-image.getInt(vx+x, vy+y));

    ret -diff;

  }

  void rememberImage(IBWImage image) {

    if (rememberedImage == null)

      rememberedImage = new byte[visionW*visionH];

    int vx = visionX1(), vy = visionY1(), i = 0;

    for y to visionH:

      for x to visionW:

        rememberedImage[i++] = clampToUByte(image.getInt(vx+x, vy+y));

  }

  int visionX1() { ret position.x-visionW; }

  int visionY1() { ret position.y-visionH; }

  Rect window_uncropped(Pt center default position) {

    ret rectAroundPt(center, visionW, visionH);

  }

}