#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/gl.h>
#include <zoom/texture.h>
#include <png.h>


int nTex;
TEXLIST *texlist;


GLuint LoadTexture(char *filename) {
  FILE *file;
  GLuint tex;
  char *name;
  png_byte header[8];
  png_structp png_ptr;
  png_infop info_ptr;
  png_bytep *row_pointers;
  png_bytep data;
  png_uint_32 width, height;
  int bit_depth, color_type, i;
  GLenum format;
  
  
  for(i = 0; i < nTex; i++) {
    if(strcasecmp(filename, texlist[i].name) == 0) return texlist[i].id;
  }
  
  name = malloc(strlen(filename)+5);
  strcpy(name, "tex/");
  strcat(name, filename);
  
  file = fopen(name, "rb");
  
  free(name);
  
  if(!file) return 0;
  
  fread(&header, 1, sizeof(header), file);
  if(png_sig_cmp(header, 0, sizeof(header))) {
    fclose(file);
    return 0;
  }
  
  png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
  if(!png_ptr) {
    fclose(file);
    return 0;
  }
  
  info_ptr = png_create_info_struct(png_ptr);
  if(!info_ptr) {
    png_destroy_read_struct(&png_ptr, NULL, NULL);
    fclose(file);
    return 0;
  }
  
  if(setjmp(png_jmpbuf(png_ptr))) {
    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
    fclose(file);
    return 0;
  }
  
  png_init_io(png_ptr, file);
  png_set_sig_bytes(png_ptr, sizeof(header));
  
  png_read_info(png_ptr, info_ptr);
  
  width = png_get_image_width(png_ptr, info_ptr);
  height = png_get_image_height(png_ptr, info_ptr);
  bit_depth = png_get_bit_depth(png_ptr, info_ptr);
  color_type = png_get_color_type(png_ptr, info_ptr);
  
  if(color_type == PNG_COLOR_TYPE_PALETTE)
    png_set_palette_to_rgb(png_ptr);
  if(color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
    png_set_expand_gray_1_2_4_to_8(png_ptr);
  if(png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
    png_set_tRNS_to_alpha(png_ptr);
  if(bit_depth < 8)
    png_set_packing(png_ptr);
  
  png_read_update_info(png_ptr, info_ptr);
  
  bit_depth = png_get_bit_depth(png_ptr, info_ptr);
  color_type = png_get_color_type(png_ptr, info_ptr);
  
  if((bit_depth != 8 && bit_depth != 16) || color_type & PNG_COLOR_MASK_PALETTE) {
    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
    fclose(file);
    return 0;
  }
  
  data = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)*height);
  row_pointers = png_malloc(png_ptr, height*png_sizeof(png_bytep));
  for(i = 0; i < height; i++)
    row_pointers[i] = data + png_get_rowbytes(png_ptr, info_ptr)*i;
  
  png_read_image(png_ptr, row_pointers);
  
  switch(color_type) {
    case PNG_COLOR_TYPE_GRAY:
      format = GL_LUMINANCE;
      break;
    case PNG_COLOR_TYPE_GRAY_ALPHA:
      format = GL_LUMINANCE_ALPHA;
      break;
    case PNG_COLOR_TYPE_RGB:
      format = GL_RGB;
      break;
    case PNG_COLOR_TYPE_RGBA:
      format = GL_RGBA;
      break;
    default:
      png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
      fclose(file);
      return 0;
  }
  
  glGenTextures(1, &tex);
  glBindTexture(GL_TEXTURE_2D, tex);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexImage2D(GL_TEXTURE_2D, 0, png_get_channels(png_ptr, info_ptr), width, height, 0,
               format, (bit_depth == 8) ? GL_UNSIGNED_BYTE : GL_UNSIGNED_SHORT, data);
  
  png_free(png_ptr, row_pointers);
  png_free(png_ptr, data);
  
  png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
  
  fclose(file);
  
  nTex++;
  
  if(nTex == 1) texlist = malloc(sizeof(TEXLIST));
  else texlist = realloc(texlist, sizeof(TEXLIST)*nTex);
  
  strcpy(texlist[nTex-1].name, filename);
  texlist[nTex-1].id = tex;
  
  return tex;
}