#include <stdlib.h>
#include <guile-cairo.h>
#include <cgif.h>
#include <string.h>

const uint8_t PALETTE[] = {
  0xFF, 0xFF, 0xFF, // WHITE
  0x00, 0x00, 0x00, // BLACK
  0xFF, 0x00, 0x00  // RED
};

#define CAIRO_RED   0x00FF0000
#define CAIRO_BLACK 0x00000000

void encode_frame(cairo_surface_t *surface, CGIF_FrameConfig *frameconfig) {
  // TODO pull colors from cairo
  size_t size = cairo_image_surface_get_width(surface) * cairo_image_surface_get_height(surface);
  frameconfig->pLocalPalette = (uint8_t*) &PALETTE;
  frameconfig->numLocalPaletteEntries = 3;
  frameconfig->pImageData = (uint8_t*)calloc(size, sizeof(uint8_t));

  if (cairo_image_surface_get_format(surface) == CAIRO_FORMAT_RGB24) {
    uint32_t* pen = (uint32_t*) cairo_image_surface_get_data(surface);
    for (size_t i = 0; i < size; i++) {
      uint32_t cairo_color = pen[i];
      switch (cairo_color & 0x00FFFFFF) {
      case CAIRO_BLACK:
	frameconfig->pImageData[i] = 1;
	break;
      case CAIRO_RED:
	frameconfig->pImageData[i] = 2;
	break;
      }
    }
  }
}

void make_gif_inner(cairo_surface_t *frames[], size_t n_frames, const char* path) {
  CGIF_Config cgif_config;
  memset(&cgif_config, 0, sizeof(CGIF_Config));
  cgif_config.path = path;
  cgif_config.attrFlags = CGIF_ATTR_IS_ANIMATED | CGIF_ATTR_NO_GLOBAL_TABLE;
  cgif_config.width = cairo_image_surface_get_width(frames[0]);
  cgif_config.height = cairo_image_surface_get_height(frames[0]);

  CGIF *cgif = cgif_newgif(&cgif_config);

  for (size_t i = 0; i < n_frames; i++) {
    cairo_surface_t *frame = frames[i];
    // Flush pending writes
    cairo_surface_flush(frame);

    CGIF_FrameConfig cgif_frameconfig;
    memset(&cgif_frameconfig, 0, sizeof(CGIF_FrameConfig));
    cgif_frameconfig.attrFlags = CGIF_FRAME_ATTR_USE_LOCAL_TABLE;
    cgif_frameconfig.delay = 100;

    encode_frame(frame, &cgif_frameconfig);
    cgif_addframe(cgif, &cgif_frameconfig);
  }

  cgif_close(cgif);
}

SCM make_gif(SCM frames, SCM path) {
  size_t n_frames = scm_to_size_t(scm_length(frames));
  cairo_surface_t **c_frames = (cairo_surface_t **) malloc(sizeof(cairo_surface_t*) * n_frames);
  for (size_t i = 0; i < n_frames; i++) {
    c_frames[i] = scm_to_cairo_surface(scm_list_ref(frames, scm_from_size_t(i)));
  }
  const char* c_path = scm_to_locale_string(path);

  make_gif_inner(c_frames, n_frames, c_path);
  return SCM_UNSPECIFIED;
}

void init_cgif() {
  scm_c_define_gsubr("make-gif", 2, 0, 0, &make_gif);
}