// fills transparent pixels in the image with
// the color of the (roughly) closest non-transparent neighbor pixel

sclass ImageInfiller {
  settable BufferedImage inputImage;
  
  // how far to infill (pixels)
  settable int maxDepth = 2;
  
  // whether to make the infilled pixels (semi-) transparent
  settable int infillOpacity = 255;
  
  int w, h;
  int[] pixels;
  PtBuffer queue;
  PtBuffer nextQueue;
  BufferedImage outputImage;
  gettable int rounds;
  gettable int filledPixels;
  
  *() {}
  *(BufferedImage *inputImage) {}
  
  run {
    prepare();
    do
      oneRound();
    while (!done());
  }
  
  bool prepared() { ret pixels != null; }
  
  bool done() {
    ret nextQueue != null && nextQueue.isEmpty()
      || rounds >= maxDepth;
  }
  
  BufferedImage get() {
    if (!prepared()) run();
    ret pixelsToBufferedImage(pixels, w);
  }
  
  void prepare {
    pixels = pixelsFromBufferedImage(inputImage);
    w = inputImage.getWidth();
    h = inputImage.getHeight();
  }
  
  void oneRound {
    ++rounds;
    queue = nextQueue;
    nextQueue = new PtBuffer;
    assertBetween("infillOpacity", 1, 255, infillOpacity);
    
    for (p : queue == null ? pixelsInImageIterator(w, h) : queue) {
      int x = p.x, y = p.y;
      int rgba = pixels[y*w+x];
      if (!isFullyTransparent(rgba)) continue;
      //new IntBuffer colors; // surrounding colors
      new MultiSet<Int> surroundingColors;
      for (int y2 = max(0, y-1); y2 < min(h, y+2); y2++)
        for (int x2 = max(0, x-1); x2 < min(w, x+2); x2++) {
          rgba = pixels[y2*w+x2];
          if (!isFullyTransparent(rgba)) surroundingColors.add(rgba);
        }
        
      if (!surroundingColors.isEmpty()) {
        // Surrounding color found, fill pixel
        pixels[y*w+x] = withOpacity(infillOpacity, surroundingColors.mostPopular());
        filledPixels++;
        // Schedule surrounding transparent pixels
        for (int y2 = max(0, y-1); y2 < min(h, y+2); y2++)
          for (int x2 = max(0, x-1); x2 < min(w, x+2); x2++)
            if (isFullyTransparent(pixels[y2*w+x2]))
              nextQueue.add(x2, y2);
      } else
        // No surrounding colors found, reschedule this pixel
        nextQueue.add(p);
    }
    
    print("Round " + rounds + " pixels filled: " + n2(filledPixels) + ", nextQueue: " + l(nextQueue));
  }
 
  selfType unlimited() {
    maxDepth(Int.MAX_VALUE);
    this;
  }
}