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

int main(int argc, char **argv) {
  char *char_map = calloc(256, sizeof(char));
  char *back_map = calloc(256, sizeof(char));

  if (argc != 3) {
    fprintf(stderr, "%s: Must provide two arguments.\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  char *s = argv[1];
  char *t = argv[2];

  while (*s && *t) {
    if (char_map[(size_t)*s] && char_map[(size_t)*s] != *t) {
      fprintf(stderr,
              "%s: Character `%c` cannot be remapped from `%c` to `%c`.\n",
              argv[0], *s, char_map[(size_t)*s], *t);
      exit(EXIT_FAILURE);
    }

    if (back_map[(size_t)*t] && back_map[(size_t)*t] != *s) {
      fprintf(stderr,
              "%s: Mapping to `%c` cannot be assigned to both `%c` and `%c`.\n",
              argv[0], *t, back_map[(size_t)*t], *s);
      exit(EXIT_FAILURE);
    }

    char_map[(size_t)*s] = *t;
    back_map[(size_t)*t] = *s;
    s++;
    t++;
  }

  if (*s || *t) {
    fprintf(stderr, "%s: Arguments do not have the same length.\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  return 0;
}