#include <renderd7/bmpconverter.hpp>

namespace BitmapConverter {

// returns 0 if all went ok, non-0 if error
// output image is always given in RGBA (with alpha channel), even if it's a BMP
// without alpha channel
unsigned decodeBMP(std::vector<unsigned char> &image, unsigned &w, unsigned &h,
                   const std::vector<unsigned char> &bmp) {
  static const unsigned MINHEADER = 54; // minimum BMP header size

  if (bmp.size() < MINHEADER)
    return -1;
  if (bmp[0] != 'B' || bmp[1] != 'M')
    return 1; // It's not a BMP file if it doesn't start with marker 'BM'
  unsigned pixeloffset = bmp[10] + 256 * bmp[11]; // where the pixel data starts
  // read width and height from BMP header
  w = bmp[18] + bmp[19] * 256;
  h = bmp[22] + bmp[23] * 256;
  // read number of channels from BMP header
  if (bmp[28] != 24 && bmp[28] != 32)
    return 2; // only 24-bit and 32-bit BMPs are supported.
  unsigned numChannels = bmp[28] / 8;

  // The amount of scanline bytes is width of image times channels, with extra
  // bytes added if needed to make it a multiple of 4 bytes.
  unsigned scanlineBytes = w * numChannels;
  if (scanlineBytes % 4 != 0)
    scanlineBytes = (scanlineBytes / 4) * 4 + 4;

  unsigned dataSize = scanlineBytes * h;
  if (bmp.size() < dataSize + pixeloffset)
    return 3; // BMP file too small to contain all pixels

  image.resize(w * h * 4);

  /*
  There are 3 differences between BMP and the raw image buffer for LodePNG:
  -it's upside down
  -it's in BGR instead of RGB format (or BRGA instead of RGBA)
  -each scanline has padding bytes to make it a multiple of 4 if needed
  The 2D for loop below does all these 3 conversions at once.
  */
  for (unsigned y = 0; y < h; y++)
    for (unsigned x = 0; x < w; x++) {
      // pixel start byte position in the BMP
      unsigned bmpos =
          pixeloffset + (h - y - 1) * scanlineBytes + numChannels * x;
      // pixel start byte position in the new raw image
      unsigned newpos = 4 * y * w + 4 * x;
      if (numChannels == 3) {
        image[newpos + 0] = bmp[bmpos + 2]; // R
        image[newpos + 1] = bmp[bmpos + 1]; // G
        image[newpos + 2] = bmp[bmpos + 0]; // B
        image[newpos + 3] = 255;            // A
      } else {
        image[newpos + 0] = bmp[bmpos + 2]; // R
        image[newpos + 1] = bmp[bmpos + 1]; // G
        image[newpos + 2] = bmp[bmpos + 0]; // B
        image[newpos + 3] = bmp[bmpos + 3]; // A
      }
    }
  return 0;
}

std::vector<unsigned char> ConvertFile(std::string filename) {

  std::vector<unsigned char> bmp;
  lodepng::load_file(bmp, filename);

  std::vector<unsigned char> image;
  unsigned w, h;
  unsigned error = BitmapConverter::decodeBMP(image, w, h, bmp);

  if (error) {
    std::cout << "BMP decoding error " << error << std::endl;
  }

  std::vector<unsigned char> png;
  error = lodepng::encode(png, image, w, h);

  if (error) {
    std::cout << "PNG encoding error " << error << ": "
              << lodepng_error_text(error) << std::endl;
  }

  return png;
}

std::vector<unsigned char> ConvertData(std::vector<unsigned char> data) {

  std::vector<unsigned char> image;
  unsigned w, h;
  unsigned error = BitmapConverter::decodeBMP(image, w, h, data);

  if (error) {
    std::cout << "BMP decoding error " << error << std::endl;
  }

  std::vector<unsigned char> png;
  error = lodepng::encode(png, image, w, h);

  if (error) {
    std::cout << "PNG encoding error " << error << ": "
              << lodepng_error_text(error) << std::endl;
  }

  return png;
}
} // namespace BitmapConverter