#include <stdlib.h>
#include <libguile.h>
#include <cgif.h>
#include <cairo.h>

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

#define CAIRO_RED 0x00FF0000
#define CAIRO_BLACK 0x00FFFFFF

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) {
    unsigned char* pen = cairo_image_surface_get_data(surface);
    for (size_t i = 0; i < size; i++) {
      uint32_t cairo_color = (uint32_t)(*(pen + i * sizeof(uint32_t) * cairo_image_surface_get_stride(surface)));
      switch (cairo_color) {
      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;
  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;
    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);
}

void make_gif(SCM frames, SCM path) {
  size_t c_length = scm_c_array_length(frames);
  scm_t_array_handle c_array;
  scm_array_get_handle(frames, &c_array);
  cairo_surface_t **c_frames = scm_array_handle_uniform_elements(&c_array);
  const char* c_path = scm_to_locale_string(path);

  make_gif_inner(c_frames, c_length, c_path);

  scm_array_handle_release(&c_array);
}

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