// has a rectangular window (visionW*visionH)
// walking range per frame is a circle with radius "range"
sclass G22Walker {
  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)
  Pt position; // current position (center), not null
  
  byte[] rememberedImage; // size visionW*visionH
  
  bool stuck; // can neither stay nor move anywhere for some reason
  int guessWork; // how many "optimal" new positions we chose from
  
  void move(BWImage 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;
    for (Pt newPos : allPointsInRect_virtual(movement))
      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, BWImage 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(BWImage 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++] = image.getByte(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);
  }
}