#include "lab_png.h"
#include "crc.h"
#include "crc.c"
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>

int is_png(U8 *buf) {
  int png_bytes[8] = {137, 80, 78, 71, 13, 10, 26, 10}; // png decimal signature

  for (int i = 0; i < 8; i++) {
    if (buf[i] != png_bytes[i]) {
      return 0;
    }
  }

  return 1;
}

int get_png_data_IHDR(struct data_IHDR *out, U8 *buf) {
  U32 *dimen_buf = (U32 *) (buf + 16 * sizeof(U8));
  out->width = ntohl(dimen_buf[0]);
  out->height = ntohl(dimen_buf[1]);

  dimen_buf = NULL;
  free(dimen_buf);
  return 0;
}

int main(int argc, char *argv[]) {
  long int f_size;
  FILE *f_ptr;
  U8 *buf;

  f_ptr = fopen(argv[1], "rb");

  fseek(f_ptr, 0, SEEK_END);
  f_size = ftell(f_ptr);
  rewind(f_ptr);

  buf = (U8 *)malloc((f_size + 1) * sizeof(U8));
  fread(buf, f_size, 1, f_ptr);
  rewind(f_ptr);

  if (!is_png(buf)) {
    printf("%s: Not a PNG file\n", argv[1]);
    return 0;
  }

  struct data_IHDR *ihdr = (struct data_IHDR*) malloc(sizeof(ihdr));
  get_png_data_IHDR(ihdr, buf);
  printf("%s: %d x %d\n", argv[1], ihdr->width, ihdr->height);

  buf = NULL;
  f_ptr = NULL;

  return 0;
}