/*
 * Secure X Message Passing Library tools.
 *
 * (c) Alexander Vdolainen 2016 <avdolainen@zoho.com>
 *
 * libsxmp is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * libsxmp is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.";
 *
 * sxtkeygen - sxt key container tool for generating the keys
 */

#include <stdio.h>
#include <dirent.h>
#define __USE_GNU
#include <stdlib.h>
#include <stdint.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>
#include <unistd.h>
#include <execinfo.h>
#include <getopt.h>
#include <string.h>
#include <errno.h>
#include <termios.h>

#include <sxt/errno.h>
#include <sxt/safebuf.h>
#include <ndbuf/ndbuf.h>
#include <sxt/sxtkey.h>
#include <sxt/socket.h>
#include <sxt/sxt.h>

#define MAX_PATHNAME    4096
#define MAX_FNAME       128
#define MAX_NAMEPREFIX  90

#define FULL_PROGRAM_NAME  "SXT key container generation tool"

static void __help_print(FILE *fso, const char *fmtname)
{
  fprintf(fso, "\n%s\n\n", FULL_PROGRAM_NAME);

  /* usage options */
  fprintf(fso, "Usage:\n");
  fprintf(fso, "\t%s [-t | --type <type>] [-n | --name <name-prefix>] [ -P | --path <path>]"
          " [-H | --hash <64bit hash>] [-p | --passphrase]\n", fmtname);

  /* defaults */
  fprintf(fso, "\t%s -h | --help\n", fmtname);
  fprintf(fso, "\t%s -v | --version\n", fmtname);

  /* options description */
  fprintf(fso, "\nOptions:\n");
  fprintf(fso, "\t%-25s Output key type:\n"
          "\t\t\t\t\t * ppkp-ed25519 (default)\n",
          "-t | --type <type>");
  fprintf(fso, "\t%-25s Prefix for the output file names.\n",
          "-n | --name <name-prefix>");
  fprintf(fso, "\t%-25s Directory path where keys will be located (defaults: ~).\n",
          "-P | --path <path>");
  fprintf(fso, "\t%-25s Include special custom 64bit hash (defaults: none).\n", "-H | --hash <64bit hash>");
  fprintf(fso, "\t%-25s Ask a passphrase to encrypt a private key (defaults: key not encrypted).\n",
          "-p | --passphrase");

  fprintf(fso, "\t%-25s Show help screen.\n", "-h | --help");
  fprintf(fso, "\t%-25s Print version information.\n", "-v | --version");

  return;
}

extern int passkey_promt(char *passbuf, size_t p_len, int cnf, void *priv);

int main(int argc, char **argv)
{
  uint64_t hash = 0;
  sxtkey_t *pair, *pubkey, *privkey;
  char *dir = NULL, *nameprefix = NULL, *keytype = NULL;
  char fullpath[MAX_PATHNAME];
  char privname[MAX_FNAME];
  char pubname[MAX_FNAME];
  struct stat statbuf;
  int encrypt = 0, opt, type = 0, r;

  pair = pubkey = privkey = NULL;

  while(1) {
    int option_index = 0;
    static struct option long_options[] = {
      /* These options a generic ones. */
      {"help", no_argument, NULL, 'h'}, /* print out help and version info */
      {"version", no_argument, NULL, 'v'}, /* just out a version info */
      /* key generation options */
      {"type", required_argument, NULL, 't'},
      {"name", required_argument, NULL, 'n'},
      {"path", required_argument, NULL, 'P'},
      {"hash", required_argument, NULL, 'H'},
      {"passphrase", no_argument, NULL, 'p'},
      /* termnil */
      {NULL, 0, NULL, 0},
    };

    if((opt = getopt_long(argc, argv, "hvt:n:P:H:p", long_options,
                          &option_index)) == -1) break;

    switch(opt) {
    case 'h':
      __help_print(stdout, argv[0]);
      return 0;
      break;
    case 'v':
      /* TODO: add version output */
      return 0;
      break;
    case 't': keytype = optarg; break;
    case 'n': nameprefix = optarg; break;
    case 'P': dir = optarg; break;
    case 'H': hash = strtoul(optarg, NULL, 0); break;
    case 'p': encrypt = 1; break;
    default:
      fprintf(stderr, "Aborting.\n");
      __help_print(stdout, argv[0]);
      abort();
    }
  }

  /* init library */
  if((r = sxt_init())) {
    fprintf(stderr, "Unable to init sxt library(%d).\nAborting.\n", r);
    abort();
  }

  /* check type */
  if(keytype) type = sxtkey_type_fname(keytype);
  else type = PPKP_ED25519;

  keytype = (char *)sxtkey_name(type);

  if(!type) {
    fprintf(stderr, "Illegal keytype.\nAborting.\n");
    abort();
  }

  /* going to check output directory */
  if(!dir) dir = getenv("HOME");
  if(!dir) {
    fprintf(stderr, "Cannot get output directory.\nAborting.\n");
    abort();
  }

  /* check if this is a directory */
  if(stat(dir, &statbuf)) {
    fprintf(stderr, "Cannot stat given directory (%s).\nAborting.\n",
            strerror(errno));
    abort();
  } else if(!S_ISDIR(statbuf.st_mode)) {
    fprintf(stderr, "Given path isn't a directory.\nAborting.\n");
    abort();
  }

  if(nameprefix) {
    if(strlen(nameprefix) > MAX_NAMEPREFIX) {
      fprintf(stderr, "Name prefix too long (max: %d).\nAborting.\n", MAX_NAMEPREFIX);
      abort();
    }
    snprintf(privname, MAX_FNAME, "%s-%s.ppkp", nameprefix, keytype);
    snprintf(pubname, MAX_FNAME, "%s-%s.pub", nameprefix, keytype);
  } else {
    snprintf(privname, MAX_FNAME, "%s.ppkp", keytype);
    snprintf(pubname, MAX_FNAME, "%s.pub", keytype);
  }

  /* ok let's deal with files */
  snprintf(fullpath, MAX_PATHNAME, "%s/%s", dir, privname); /* private key file output */
  if(!stat(fullpath, &statbuf)) {
    fprintf(stderr, "Private key file '%s' already exists.\nAborting.\n", fullpath);
    abort();
  }
  snprintf(fullpath, MAX_PATHNAME, "%s/%s", dir, pubname); /* public key file output */
  if(!stat(fullpath, &statbuf)) {
    fprintf(stderr, "Public key file '%s' already exists.\nAborting.\n", fullpath);
    abort();
  }

  /* looks like all is fine */
  fprintf(stdout, "Going to generate %s keys:\n", keytype);
  fprintf(stdout, "Output will located in '%s':\n", dir);
  fprintf(stdout, "\t * Private key: %s\n", privname);
  fprintf(stdout, "\t * Public key: %s\n", pubname);
  if(encrypt) {
    fprintf(stdout, "Private key going to be encrypted.\n");
    fprintf(stdout, "Passkey phrase will be asked later.\n");
  }

  /* generate a key first */
  if(!(pair = sxtkey_alloc())) {
    fprintf(stderr, "Not enough memory to allocate a key.\nAborting.\n");
    abort();
  }
  fprintf(stdout, "Generating key pair ...");
  if((r = sxtkey_generate(pair, type, 0)) != SXT_SUCCESS) {
    fprintf(stderr, "FAIL.\nError (%d).\nAborting.\n", r);
    sxtkey_free(pair);
    abort();
  } else fprintf(stdout, "DONE.\n");

  /* hash */
  if(hash) sxtkey_assign_hash(pair, hash);

  /* duplicate private */
  if((r = sxtkey_dup_private(pair, &privkey)) != SXT_SUCCESS) {
    fprintf(stderr, "Unable to duplicate private key(%d).\nAborting.\n", r);
    sxtkey_free(pair);
    abort();
  }
  /* get public duplicate */
  if((r = sxtkey_dup_public(pair, &pubkey)) != SXT_SUCCESS) {
    fprintf(stderr, "Unable to duplicate public key(%d).\nAborting.\n", r);
    sxtkey_free(pair);
    sxtkey_free(privkey);
    abort();
  }

  /* ok, output private key first */
  snprintf(fullpath, MAX_PATHNAME, "%s/%s", dir, privname);
  if(!encrypt) { /* will not encrypt */
    r = sxtkey_export_priv_file(privkey, fullpath, NULL, NULL, NULL);
  } else {
    r = sxtkey_export_priv_file(privkey, fullpath, NULL, passkey_promt,
                                (void *)"Enter passkey phrase:");
  }

  if(r != SXT_SUCCESS) {
  __failed_export:
    fprintf(stderr, "Unable to perform key export (%d).\nAborting.\n", r);
    sxtkey_burn(pair);
    sxtkey_burn(privkey);
    sxtkey_free(pair);
    sxtkey_free(privkey);
    abort();
  }

  /* ok, output public key */
  snprintf(fullpath, MAX_PATHNAME, "%s/%s", dir, pubname);
  r = sxtkey_export_public_file(pubkey, fullpath);
  if(r != SXT_SUCCESS) goto __failed_export;

  sxtkey_burn(pair);
  sxtkey_burn(privkey);
  sxtkey_burn(pubkey);
  sxtkey_free(pair);
  sxtkey_free(privkey);
  sxtkey_free(pubkey);

  return 0;
}