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

#pragma pack(1)

struct chunk_hdr
{
  unsigned short chunk_id;
  unsigned long chunk_offset;
};

struct point
{
  float p[3];
};

struct face
{
  unsigned short v[3];
  unsigned short flags;
};

struct mesh_matrix
{
  float matrix[4][3];
};


void print_zone(FILE *f, int length)
{
  unsigned char *buf = (unsigned char *)malloc(length + 1);

  fread(buf, length, 1, f);
  // Print HEX version
  for (int i = 0; i < length; i++)
  {
    printf(" %02x", buf[i]);
    if ((i+1) % 25 == 0)
      printf("\n");
  }
  printf("\n");
  // Print ASCII version
  for (int i = 0; i < length; i++)
  {
    printf("%c", (buf[i] == '\n')?' ':buf[i]);
    if ((i+1) % 25 == 0)
      printf("\n");
  }
  printf("\n");

  free(buf);
}


short read_short(FILE *f)
{
  unsigned short x;
  fread(&x, sizeof(unsigned short), 1, f);
  return x;
}


long read_long(FILE *f)
{
  unsigned long x;
  fread(&x, sizeof(unsigned long), 1, f);
  return x;
}


float read_float(FILE *f)
{
  float x;
  fread(&x, sizeof(float), 1, f);
  return x;
}


unsigned char *read_string(FILE *f)
{
  unsigned char s[201], *r;

  for (int i = 0; i < 200; i++)
  {
    fread(&s[i], 1, 1, f);
    if (s[i] == '\0')
      break;
  }

  r = (unsigned char *)calloc(strlen((char *)s) + 1, 1);
  strcpy((char *)r, (char *)s);
  return r;
}


struct chunk_hdr read_chunk_hdr(FILE *f)
{
  struct chunk_hdr hdr;
  fread(&hdr, 6, 1, f);
  printf("CHUNK:   %04x - %ld\n", hdr.chunk_id, hdr.chunk_offset);
  return hdr;
}


void unread_chunk_hdr(FILE *f)
{
  fseek(f, -6, SEEK_CUR);
}


void skip_chunk(FILE *f, struct chunk_hdr hdr)
{
  fseek(f, hdr.chunk_offset, SEEK_CUR);
}


int main (int argc, char **argv)
{
  struct chunk_hdr hdr;


  FILE *f = fopen("sphere04.3ds", "rb");

  // Read MAGIC header (offset = file size)
  hdr = read_chunk_hdr(f);

  // Read VERSION
  hdr = read_chunk_hdr(f);
  printf("Version: %u\n", read_long(f));
  
  // Read MESH DATA header
  hdr = read_chunk_hdr(f);

  // Read MESH VERSION header
  hdr = read_chunk_hdr(f);
  printf("Version: %u\n", read_long(f));

  // Read Master Scale
  hdr = read_chunk_hdr(f);
  printf("Scale: %f\n", read_float(f));

  // Read Name
  hdr = read_chunk_hdr(f);
  unsigned char *s = read_string(f);
  printf("Name:    %s\n", s);
  free(s);

  // Read TRIANGLE OBJECT header
  hdr = read_chunk_hdr(f);

  // Read POINT ARRAY
  hdr = read_chunk_hdr(f);
  unsigned short num_pts = read_short(f);
  printf("Size:    %u\n", num_pts);
  struct point *pts = (struct point *)calloc(num_pts, sizeof(struct point));
  fread(pts, sizeof(struct point), num_pts, f);

  // Read MESH MATRIX
  hdr = read_chunk_hdr(f);
  struct mesh_matrix mm;
  fread(&mm, sizeof(struct mesh_matrix), 1, f);
  for (int i = 0; i < 3; i++)
  {
    for (int j = 0; j < 4; j++)
      printf("%.2f ", mm.matrix[j][i]);
    printf("\n");
  }

  // Read FACE ARRAY
  hdr = read_chunk_hdr(f);
  unsigned short num_face = read_short(f);
  printf("Size:    %u\n", num_face);
  struct face *face = (struct face *)calloc(num_face, sizeof(struct face));
  fread(face, sizeof(struct face), num_face, f);

  // Read SMOOTH GROUP
  hdr = read_chunk_hdr(f);
  unread_chunk_hdr(f);
  skip_chunk(f, hdr);

  // Good Enough

  // Print next section
  print_zone(f, 500);


  fclose(f);
  char junk;
  scanf("%c", &junk);
  return 0;
}