/*
     This file is part of GNUnet.
     Copyright (C) 2014 GNUnet e.V.

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet 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 GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA 02110-1301, USA.
*/
/**
 * @file util/gnunet-scrypt.c
 * @brief tool to manipulate SCRYPT proofs of work.
 * @author Bart Polot
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include <gcrypt.h>

/**
 * Amount of work required (W-bit collisions) for NSE proofs, in collision-bits.
 */
static unsigned long long nse_work_required;

/**
 * Interval between proof find runs.
 */
static struct GNUNET_TIME_Relative proof_find_delay;

static struct GNUNET_CRYPTO_EddsaPublicKey pub;

static uint64_t proof;

static struct GNUNET_SCHEDULER_Task *proof_task;

static const struct GNUNET_CONFIGURATION_Handle *cfg;

static char *pkfn;

static char *pwfn;


/**
 * Write our current proof to disk.
 *
 * @param cls closure
 */
static void
shutdown_task (void *cls)
{
  if (sizeof (proof) !=
      GNUNET_DISK_fn_write (pwfn,
			    &proof,
			    sizeof (proof),
                            GNUNET_DISK_PERM_USER_READ |
                            GNUNET_DISK_PERM_USER_WRITE))
    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
			      "write",
			      pwfn);
}


/**
 * Calculate the 'proof-of-work' hash (an expensive hash).
 *
 * @param buf data to hash
 * @param buf_len number of bytes in @a buf
 * @param result where to write the resulting hash
 */
static void
pow_hash (const void *buf,
          size_t buf_len,
          struct GNUNET_HashCode *result)
{
  GNUNET_break (0 ==
  gcry_kdf_derive (buf, buf_len,
                   GCRY_KDF_SCRYPT,
                   1 /* subalgo */,
                   "gnunet-proof-of-work", strlen ("gnunet-proof-of-work"),
                   2 /* iterations; keep cost of individual op small */,
                   sizeof (struct GNUNET_HashCode), result));
}


/**
 * Count the leading zeroes in hash.
 *
 * @param hash to count leading zeros in
 * @return the number of leading zero bits.
 */
static unsigned int
count_leading_zeroes (const struct GNUNET_HashCode *hash)
{
  unsigned int hash_count;

  hash_count = 0;
  while (0 == GNUNET_CRYPTO_hash_get_bit (hash, hash_count))
    hash_count++;
  return hash_count;
}


/**
 * Find our proof of work.
 *
 * @param cls closure (unused)
 * @param tc task context
 */
static void
find_proof (void *cls)
{
  #define ROUND_SIZE 10
  uint64_t counter;
  char buf[sizeof (struct GNUNET_CRYPTO_EddsaPublicKey) +
           sizeof (uint64_t)] GNUNET_ALIGN;
  struct GNUNET_HashCode result;
  unsigned int i;
  struct GNUNET_TIME_Absolute timestamp;
  struct GNUNET_TIME_Relative elapsed;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
	      "Got Proof of Work %llu\n",
	      (unsigned long long) proof);
  proof_task = NULL;
  GNUNET_memcpy (&buf[sizeof (uint64_t)], &pub,
          sizeof (struct GNUNET_CRYPTO_EddsaPublicKey));
  i = 0;
  counter = proof;
  timestamp = GNUNET_TIME_absolute_get ();
  while ((counter != UINT64_MAX) && (i < ROUND_SIZE))
  {
    GNUNET_memcpy (buf, &counter, sizeof (uint64_t));
    pow_hash (buf, sizeof (buf), &result);
    if (nse_work_required <= count_leading_zeroes (&result))
    {
      proof = counter;
      FPRINTF (stdout, "Proof of work found: %llu!\n",
               (unsigned long long) proof);
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    counter++;
    i++;
  }
  elapsed = GNUNET_TIME_absolute_get_duration (timestamp);
  elapsed = GNUNET_TIME_relative_divide (elapsed, ROUND_SIZE);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Current: %llu [%s/proof]\n",
              (unsigned long long) counter,
              GNUNET_STRINGS_relative_time_to_string (elapsed, 0));
  if (proof / (100 * ROUND_SIZE) < counter / (100 * ROUND_SIZE))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Testing proofs currently at %llu\n",
                (unsigned long long) counter);
    /* remember progress every 100 rounds */
    proof = counter;
    shutdown_task (NULL);
  }
  else
  {
    proof = counter;
  }
  proof_task =
    GNUNET_SCHEDULER_add_delayed_with_priority (proof_find_delay,
						GNUNET_SCHEDULER_PRIORITY_IDLE,
						&find_proof, NULL);
}


/**
 * Main function that will be run by the scheduler.
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg configuration
 */
static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *config)
{
  struct GNUNET_CRYPTO_EddsaPrivateKey *pk;
  char *pids;

  cfg = config;
  /* load proof of work */
  if (NULL == pwfn)
  {
    if (GNUNET_OK !=
        GNUNET_CONFIGURATION_get_value_filename (cfg,
						 "NSE",
                                                 "PROOFFILE",
                                                 &pwfn))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "NSE",
				 "PROOFFILE");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
  }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Proof of Work file: %s\n",
              pwfn);
  if ( (GNUNET_YES != GNUNET_DISK_file_test (pwfn)) ||
       (sizeof (proof) !=
        GNUNET_DISK_fn_read (pwfn, &proof, sizeof (proof))))
    proof = 0;

  /* load private key */
  if (NULL == pkfn)
  {
    if (GNUNET_OK !=
	GNUNET_CONFIGURATION_get_value_filename (cfg,
						 "PEER",
						 "PRIVATE_KEY",
						 &pkfn))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "PEER",
				 "PRIVATE_KEY");
      return;
    }
  }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
	      "Private Key file: %s\n",
	      pkfn);
  if (NULL == (pk = GNUNET_CRYPTO_eddsa_key_create_from_file (pkfn)))
  {
    FPRINTF (stderr,
	     _("Loading hostkey from `%s' failed.\n"),
	     pkfn);
    GNUNET_free (pkfn);
    return;
  }
  GNUNET_free (pkfn);
  GNUNET_CRYPTO_eddsa_key_get_public (pk, &pub);
  GNUNET_free (pk);
  pids = GNUNET_CRYPTO_eddsa_public_key_to_string (&pub);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Peer ID: %s\n",
              pids);
  GNUNET_free (pids);

  /* get target bit amount */
  if (0 == nse_work_required)
  {
    if (GNUNET_OK !=
        GNUNET_CONFIGURATION_get_value_number (cfg,
					       "NSE",
					       "WORKBITS",
                                               &nse_work_required))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
				 "NSE",
				 "WORKBITS");
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    if (nse_work_required >= sizeof (struct GNUNET_HashCode) * 8)
    {
      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
				 "NSE",
				 "WORKBITS",
                                _("Value is too large.\n"));
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
    else if (0 == nse_work_required)
    {
      GNUNET_SCHEDULER_shutdown ();
      return;
    }
  }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Bits: %llu\n",
              nse_work_required);

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Delay between tries: %s\n",
              GNUNET_STRINGS_relative_time_to_string (proof_find_delay, 1));
  proof_task =
    GNUNET_SCHEDULER_add_with_priority (GNUNET_SCHEDULER_PRIORITY_IDLE,
					&find_proof,
					NULL);
  GNUNET_SCHEDULER_add_shutdown (&shutdown_task,
				 NULL);
}


/**
 * Program to manipulate ECC key files.
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main (int argc, char *const *argv)
{
  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
    { 'b', "bits", "BITS",
      gettext_noop ("number of bits to require for the proof of work"),
      1, &GNUNET_GETOPT_set_ulong, &nse_work_required },
    { 'k', "keyfile", "FILE",
      gettext_noop ("file with private key, otherwise default is used"),
      1, &GNUNET_GETOPT_set_filename, &pkfn },
    { 'o', "outfile", "FILE",
      gettext_noop ("file with proof of work, otherwise default is used"),
      1, &GNUNET_GETOPT_set_filename, &pwfn },
    { 't', "timeout", "TIME",
      gettext_noop ("time to wait between calculations"),
      1, &GNUNET_GETOPT_set_relative_time, &proof_find_delay },
    GNUNET_GETOPT_OPTION_END
  };
  int ret;

  if (GNUNET_OK !=
      GNUNET_STRINGS_get_utf8_args (argc, argv, &argc, &argv))
    return 2;

  ret = (GNUNET_OK ==
         GNUNET_PROGRAM_run (argc, argv,
                             "gnunet-scrypt [OPTIONS] prooffile",
                             gettext_noop ("Manipulate GNUnet proof of work files"),
                             options, &run, NULL)) ? 0 : 1;
  GNUNET_free ((void*) argv);
  GNUNET_free_non_null (pwfn);
  return ret;
}

/* end of gnunet-scrypt.c */
