#include"png_cache.h"
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

/* Read image and add to cache. */
ImageCache *LoadImage(const char *filename, ImageCache **cache)
{
   ImageCache *node, **previous;
   int size;

   /* Return existing file if it has already been loaded. */
   previous = cache;
   for(node = *cache; node != NULL; node = node->next)
   {
      if( strcmp(filename, node->filename) == 0 )
         return node;
      previous = &(node->next);
   }

   /* Allocate new node. */
   node = (ImageCache*)calloc(1, sizeof(ImageCache));
   if( node == NULL )
   {
      fputs("Out of memory.\n", stderr);
      return NULL;
   }

   /* Load image header. */
   node->filename = filename;
   node->image.version = PNG_IMAGE_VERSION;
   if( strcmp(filename, "-") == 0 )
   {
      if( !png_image_begin_read_from_stdio(&(node->image), stdin) )
      {
         fputs("-: error reading from stdin.\n", stderr);
         free(node);
         return NULL;
      }
   }
   else
   {
      if( !png_image_begin_read_from_file(&(node->image), filename) )
      {
         fprintf(stderr, "%s: error reading from file.\n", filename);
         free(node);
         return NULL;
      }
   }

   /* Drop images that are too small or too large. */
   if( node->image.width < 1 || node->image.width >= 0x8000 ||
       node->image.height < 1 || node->image.height >= 0x8000 )
   {
      fprintf(stderr, "%s: unacceptable image size (%u,%u)\n",
              filename, node->image.width, node->image.height);
      free(node);
      return NULL;
   }

   /* Load pixel data. */
   node->image.format = PNG_FORMAT_RGBA;
   size = PNG_IMAGE_SIZE(node->image);
   node->pixels = (png_bytep)malloc(size);
   if( node->pixels == NULL )
   {
      fputs("Out of memory.\n", stderr);
      free(node);
      return NULL;
   }
   if( !png_image_finish_read(&(node->image), NULL, node->pixels, 0, NULL) )
   {
      fprintf(stderr, "%s: error loading file.\n", filename);
      free(node->pixels);
      free(node);
      return NULL;
   }

   /* Add node to list. */
   *previous = node;
   return node;
}

/* Release memory. */
void FreeImageCache(ImageCache **cache)
{
   ImageCache *next;

   for(; *cache != NULL; *cache = next)
   {
      next = (*cache)->next;
      free((*cache)->pixels);
      free(*cache);
   }
}