/* includes */
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* internal protoypes */
static void print(void);

static void insert(const char *name, uint32_t index);

typedef struct cred {
  char name[16];
} cred_t;

static cred_t creds[8];

#define ADMIN "root"

// ./int03 huan 4294967296

/* entry point */
int main(int argc, char **argv) {
  if (argc < 3) {
    printf("usage: %s <name> <index>\n", argv[0]);
    return -1;
  }
  char *endptr;
  errno = 0;
  uint32_t index = (uint32_t)strtoull(argv[2], &endptr, 10);
  if (errno || *endptr) {
    fprintf(stderr, "Conversion error, non-convertible part: %s\n", endptr);
    exit(EXIT_FAILURE);
  }

  snprintf(creds[0].name, 16, "%s", ADMIN);
  if (index == 0) {
    fprintf(stderr, "ALERT: someone tried to overwrite admin account!\n");
    exit(EXIT_FAILURE);
  }

  insert(argv[1], index);
  print();
  return 0;
}

/* internal function definitions */
static void insert(const char *name, uint32_t index) {
  if (index > 7) {
    fprintf(stderr, "Invalid index\n");
    exit(EXIT_FAILURE);
  }
  if (strlen(name) > 15) {
    fprintf(stderr, "Name must not exceed 15 characters\n");
    exit(EXIT_FAILURE);
  }
  snprintf(creds[index].name, 16, "%s", name);
}

static void print(void) {
  for (int i = 0; i < 8; ++i) {
    if (i == 0) {
      printf("Admin: ");
    } else {
      printf("User: ");
    }
    if (strcmp(creds[i].name, "")) {
      printf("%s\n", creds[i].name);
    } else {
      printf("unknown\n");
    }
  }
}