/* version 2023-10-04 */

/* cbor format is https://datatracker.ietf.org/doc/html/rfc8949 */
/* qr code data is in format cose (itself using cbor) https://datatracker.ietf.org/doc/draft-ietf-cose-rfc8152bis-struct/15/ */
/* in my case it's tag 18, array of size 4
 * item 0 is a byte string, which is "protected header" which you can feed to
 *        cbor again, which gives a map of size 2. First item has key 1
 *        and value -7 which is COSE Algorithms -7 defined at
 *        https://www.iana.org/assignments/cose/cose.xhtml#algorithms
 *        it is : ES256 	-7 	ECDSA w/ SHA-256 	[kty] 		[RFC-ietf-cose-rfc8152bis-algs-12] 	Yes
 *        then second item has key 4 and a value as byte string of length 8
 *        which is a key identifier
 * item 1 is a pair map of size 0
 * item 2 contains the data of the qr code to be fed to cbor again
 *            you can use hex2bin for that, you copy the bytes as printed
 *            and you do: echo [the bytes] | ./hex2bin | ./cbor
 *        in my case, it's vaccine (field 'v') and has name/date of birth/date
 *        of injection/who issued the thing, etc.
 *        see https://blog.callicode.fr/post/2021/covid_pass.html (in french)
 *        in it: item with key 4 is a date (expiration date), for me it's a
 *        number and I do date -d@<number> to decode. Item with key 6 is also
 *        a date (issuing date), also a number, same command to decode.
 *        document for format is:
 *        https://ec.europa.eu/health/sites/default/files/ehealth/docs/digital-green-certificates_v3_en.pdf
 * item 3 is a byte string of length 64, the signature
 */

/* should not be here, but... The QR code data, once decoded is zipped and
 * saved in base45. So you do: ./base45 < qr_code.bin.z.b45 > qr_code.bin.z
 * then: ./zunlib qr_code.bin.z > qr_code.bin
 * and you good.
 *
 * ah, and to get the qr code from the image use external program zbarimg
 * you do: zbarimg image.jpg (or whatever image format zbarimg accepts)
 * you get the qr code printed in the terminal as a string starting
 * with QR-Code:HC1:
 * you copy this string (without QR-Code:HC1:) and you put it in the file
 * qr_code.bin.z.b45
 */

/* base45.c is at: http://sedcore.eu.org/base45.c
 * zunlib.c is at: http://sedcore.eu.org/zunlib.c
 * hex2bin.c is at http://sedcore.eu.org/hex2bin.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>

#define NORMAL     0
#define INDEFINITE 1
#define TERMINATE  2

#define Printf(...) do { {int i; for (i = 0; i < level; i++) putchar(' ');} printf(__VA_ARGS__); } while (0)

void decode_item(int level)
{
  int i;
  int c;
  int type;
  int value;
  uint64_t len;
  int special_len;

  c = getchar(); if (c == EOF) abort();
  type = c >> 5;
  value = c & 0x1f;
  len = value;
  special_len = NORMAL;
  switch (value) {
  case 24:
    c = getchar(); if (c == EOF) abort();
    len = c;
    break;
  case 25:
    len = 0;
    for (i = 0; i < 2; i++) {
      len <<= 8;
      c = getchar(); if (c == EOF) abort();
      len |= c;
    }
    break;
  case 26:
    len = 0;
    for (i = 0; i < 4; i++) {
      len <<= 8;
      c = getchar(); if (c == EOF) abort();
      len |= c;
    }
    break;
  case 27:
    len = 0;
    for (i = 0; i < 8; i++) {
      len <<= 8;
      c = getchar(); if (c == EOF) abort();
      len |= c;
    }
    break;
  case 28: case 29: case 30: abort();
  case 31:
    if (type == 0 || type == 1 || type == 6) abort();
    if (type >= 2 && type <= 5) special_len = INDEFINITE;
    if (type == 7) special_len = TERMINATE;
    break;
  }
  if (special_len) { printf("special len: todo\n"); exit(1); }
  switch (type) {
  case 0: Printf("number %"PRIu64"\n", len); break;
  case 1: Printf("number %"PRId64"\n", -1-len); break;
  case 2:
    Printf("byte string[%"PRIu64"]:", len);
    for (i = 0; i < len; i++) {
      c = getchar(); if (c == EOF) abort();
      printf(" %2.2x", c);
    }
    printf("\n");
    break;
  case 3:
    Printf("char string[%"PRIu64"]: '", len);
    for (i = 0; i < len; i++) {
      c = getchar(); if (c == EOF) abort();
      printf("%c", c);
    }
    printf("'\n");
    break;
  case 4:
    Printf("array [%"PRIu64"]\n", len);
    for (i = 0; i < len; i++) {
      Printf("  item %d:\n", i);
      decode_item(level + 4);
    }
    break;
  case 5:
    Printf("pair map [%"PRIu64"]\n", len);
    for (i = 0; i < len; i++) {
      Printf("  item %d:\n", i);
      Printf("    key: \n");
      decode_item(level + 6);
      Printf("    value: \n");
      decode_item(level + 6);
    }
    break;
  case 6: Printf("tag %"PRIu64"\n", len); decode_item(level + 2); break;
  case 7: Printf("float/simple value\n"); exit(1); break;
  }
}

int main(void)
{
  int c;
  while (1) {
    c = getchar(); if (c == EOF) break;
    ungetc(c, stdin);
    decode_item(0);
  }
  return 0;
}