/*
  This file is part of TALER
  Copyright (C) 2018-2022 Taler Systems SA

  TALER 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.

  TALER 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 TALER; see the file COPYING.  If not, see
  <http://www.gnu.org/licenses/>
*/
/**
 * @file testing/testing_api_cmd_refresh.c
 * @brief commands for testing all "refresh" features.
 * @author Marcello Stanisci
 */
#include "platform.h"
#include "taler_json_lib.h"
#include <gnunet/gnunet_curl_lib.h>
#include "taler_testing_lib.h"
#include "taler_signatures.h"
#include "backoff.h"

/**
 * How long do we wait AT MOST when retrying?
 */
#define MAX_BACKOFF GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_MILLISECONDS, 100)

/**
 * How often do we retry before giving up?
 */
#define NUM_RETRIES 5

/**
 * How long do we wait AT MOST when retrying?
 */
#define MAX_BACKOFF GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_MILLISECONDS, 100)

/**
 * Information about a fresh coin generated by the refresh
 * operation.
 */
struct TALER_TESTING_FreshCoinData
{

  /**
   * If @e amount is NULL, this specifies the denomination key to
   * use.  Otherwise, this will be set (by the interpreter) to the
   * denomination PK matching @e amount.
   */
  const struct TALER_EXCHANGE_DenomPublicKey *pk;

  /**
   * Set (by the interpreter) to the exchange's signature over the
   * coin's public key.
   */
  struct TALER_DenominationSignature sig;

  /**
   * Set (by the interpreter) to the coin's private key.
   */
  struct TALER_CoinSpendPrivateKeyP coin_priv;

  /*
   * Age commitment for the coin, NULL if not applicable.
   */
  struct TALER_AgeCommitment *age_commitment;

  /**
   * The blinding key (needed for recoup operations).
   */
  union TALER_DenominationBlindingKeyP blinding_key;

};


/**
 * State for a "refresh melt" command.
 */
struct RefreshMeltState
{

  /**
   * Reference to reserve_withdraw operations for coin to
   * be used for the /refresh/melt operation.
   */
  const char *coin_reference;

  /**
   * Data used in the refresh operation.
   */
  struct TALER_EXCHANGE_RefreshData refresh_data;

  /**
   * Reference to a previous melt command.
   */
  const char *melt_reference;

  /**
   * Melt handle while operation is running.
   */
  struct TALER_EXCHANGE_MeltHandle *rmh;

  /**
   * Interpreter state.
   */
  struct TALER_TESTING_Interpreter *is;

  /**
   * Array of the denomination public keys
   * corresponding to the @e num_fresh_coins;
   */
  struct TALER_EXCHANGE_DenomPublicKey *fresh_pks;

  /**
   * Array of @e num_fresh_coins of results from
   * the melt operation.
   */
  struct TALER_EXCHANGE_MeltBlindingDetail *mbds;

  /**
   * Entropy seed for the refresh-melt operation.
   */
  struct TALER_RefreshMasterSecretP rms;

  /**
   * Private key of the dirty coin being melted.
   */
  const struct TALER_CoinSpendPrivateKeyP *melt_priv;

  /*
   * Age commitment for the coin, NULL if not applicable.
   */
  struct TALER_AgeCommitment *age_commitment;

  /**
   * Task scheduled to try later.
   */
  struct GNUNET_SCHEDULER_Task *retry_task;

  /**
   * How long do we wait until we retry?
   */
  struct GNUNET_TIME_Relative backoff;

  /**
   * How long did we wait in total for retries?
   */
  struct GNUNET_TIME_Relative total_backoff;

  /**
   * Amounts to be generated during melt.
   */
  const char **melt_fresh_amounts;

  /**
   * Number of fresh coins generated by the melt.
   */
  unsigned int num_fresh_coins;

  /**
   * Expected HTTP response code.
   */
  unsigned int expected_response_code;

  /**
   * if set to #GNUNET_YES, then two /refresh/melt operations
   * will be performed.  This is needed to trigger the logic
   * that manages those already-made requests.  Note: it
   * is not possible to just copy-and-paste a test refresh melt
   * CMD to have the same effect, because every data preparation
   * generates new planchets that (in turn) make the whole "hash"
   * different from any previous one, therefore NOT allowing the
   * exchange to pick any previous /rerfesh/melt operation from
   * the database.
   */
  bool double_melt;

  /**
   * How often should we retry on (transient) failures?
   */
  unsigned int do_retry;

  /**
   * Set by the melt callback as it comes from the exchange.
   */
  uint16_t noreveal_index;
};


/**
 * State for a "refresh reveal" CMD.
 */
struct RefreshRevealState
{
  /**
   * Link to a "refresh melt" command.
   */
  const char *melt_reference;

  /**
   * Reveal handle while operation is running.
   */
  struct TALER_EXCHANGE_RefreshesRevealHandle *rrh;

  /**
   * Convenience struct to keep in one place all the
   * data related to one fresh coin, set by the reveal callback
   * as it comes from the exchange.
   */
  struct TALER_TESTING_FreshCoinData *fresh_coins;

  /**
   * Array of @e num_fresh_coins planchet secrets derived
   * from the transfer secret per fresh coin.
   */
  struct TALER_PlanchetMasterSecretP *psa;

  /**
   * Interpreter state.
   */
  struct TALER_TESTING_Interpreter *is;

  /**
   * Task scheduled to try later.
   */
  struct GNUNET_SCHEDULER_Task *retry_task;

  /**
   * How long do we wait until we retry?
   */
  struct GNUNET_TIME_Relative backoff;

  /**
   * How long did we wait in total for retries?
   */
  struct GNUNET_TIME_Relative total_backoff;

  /**
   * Number of fresh coins withdrawn, set by the
   * reveal callback as it comes from the exchange,
   * it is the length of the @e fresh_coins array.
   */
  unsigned int num_fresh_coins;

  /**
   * Expected HTTP response code.
   */
  unsigned int expected_response_code;

  /**
   * How often should we retry on (transient) failures?
   */
  unsigned int do_retry;

};


/**
 * State for a "refresh link" CMD.
 */
struct RefreshLinkState
{
  /**
   * Link to a "refresh reveal" command.
   */
  const char *reveal_reference;

  /**
   * Handle to the ongoing operation.
   */
  struct TALER_EXCHANGE_LinkHandle *rlh;

  /**
   * Interpreter state.
   */
  struct TALER_TESTING_Interpreter *is;

  /**
   * Task scheduled to try later.
   */
  struct GNUNET_SCHEDULER_Task *retry_task;

  /**
   * How long do we wait until we retry?
   */
  struct GNUNET_TIME_Relative backoff;

  /**
   * How long did we wait in total for retries?
   */
  struct GNUNET_TIME_Relative total_backoff;

  /**
   * Expected HTTP response code.
   */
  unsigned int expected_response_code;

  /**
   * How often should we retry on (transient) failures?
   */
  unsigned int do_retry;

};


/**
 * Run the command.
 *
 * @param cls closure.
 * @param cmd the command to execute.
 * @param is the interpreter state.
 */
static void
refresh_reveal_run (void *cls,
                    const struct TALER_TESTING_Command *cmd,
                    struct TALER_TESTING_Interpreter *is);


/**
 * Task scheduled to re-try #refresh_reveal_run.
 *
 * @param cls a `struct RefreshRevealState`
 */
static void
do_reveal_retry (void *cls)
{
  struct RefreshRevealState *rrs = cls;

  rrs->retry_task = NULL;
  rrs->is->commands[rrs->is->ip].last_req_time
    = GNUNET_TIME_absolute_get ();
  refresh_reveal_run (rrs,
                      NULL,
                      rrs->is);
}


/**
 * "refresh reveal" request callback; it checks that the response
 * code is expected and copies into its command's state the data
 * coming from the exchange, namely the fresh coins.
 *
 * @param cls closure, a `struct RefreshRevealState`
 * @param hr HTTP response details
 * @param num_coins number of fresh coins created, length of the
 *        @a sigs and @a coin_privs arrays, 0 if the operation
 *        failed.
 * @param coin_privs array of @a num_coins private keys for the
 *        coins that were created, NULL on error.
 * @param psa array of @a num_coins planchet secrets (derived from the transfer secret) for each of the coins
 * @param sigs array of signature over @a num_coins coins,
 *        NULL on error.
 */
static void
reveal_cb (void *cls,
           const struct TALER_EXCHANGE_RevealResult *rr)
{
  struct RefreshRevealState *rrs = cls;
  const struct TALER_EXCHANGE_HttpResponse *hr = &rr->hr;
  const struct TALER_TESTING_Command *melt_cmd;

  rrs->rrh = NULL;
  if (rrs->expected_response_code != hr->http_status)
  {
    if (0 != rrs->do_retry)
    {
      rrs->do_retry--;
      if ( (0 == hr->http_status) ||
           (TALER_EC_GENERIC_DB_SOFT_FAILURE == hr->ec) ||
           (MHD_HTTP_INTERNAL_SERVER_ERROR == hr->http_status) )
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Retrying refresh reveal failed with %u/%d\n",
                    hr->http_status,
                    (int) hr->ec);
        /* on DB conflicts, do not use backoff */
        if (TALER_EC_GENERIC_DB_SOFT_FAILURE == hr->ec)
          rrs->backoff = GNUNET_TIME_UNIT_ZERO;
        else
          rrs->backoff = GNUNET_TIME_randomized_backoff (rrs->backoff,
                                                         MAX_BACKOFF);
        rrs->total_backoff = GNUNET_TIME_relative_add (rrs->total_backoff,
                                                       rrs->backoff);
        rrs->is->commands[rrs->is->ip].num_tries++;
        rrs->retry_task = GNUNET_SCHEDULER_add_delayed (rrs->backoff,
                                                        &do_reveal_retry,
                                                        rrs);
        return;
      }
    }
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u/%d to command %s in %s:%u\n",
                hr->http_status,
                (int) hr->ec,
                rrs->is->commands[rrs->is->ip].label,
                __FILE__,
                __LINE__);
    json_dumpf (hr->reply,
                stderr,
                0);
    TALER_TESTING_interpreter_fail (rrs->is);
    return;
  }
  melt_cmd = TALER_TESTING_interpreter_lookup_command (rrs->is,
                                                       rrs->melt_reference);
  if (NULL == melt_cmd)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rrs->is);
    return;
  }
  switch (hr->http_status)
  {
  case MHD_HTTP_OK:
    rrs->num_fresh_coins = rr->details.success.num_coins;
    rrs->psa = GNUNET_new_array (rrs->num_fresh_coins,
                                 struct TALER_PlanchetMasterSecretP);
    rrs->fresh_coins = GNUNET_new_array (rrs->num_fresh_coins,
                                         struct TALER_TESTING_FreshCoinData);
    for (unsigned int i = 0; i<rrs->num_fresh_coins; i++)
    {
      const struct TALER_EXCHANGE_RevealedCoinInfo *coin
        = &rr->details.success.coins[i];
      struct TALER_TESTING_FreshCoinData *fc = &rrs->fresh_coins[i];

      rrs->psa[i] = coin->ps;
      fc->blinding_key = coin->bks;
      if (GNUNET_OK !=
          TALER_TESTING_get_trait_denom_pub (melt_cmd,
                                             i,
                                             &fc->pk))
      {
        GNUNET_break (0);
        TALER_TESTING_interpreter_fail (rrs->is);
        return;
      }
      fc->coin_priv = coin->coin_priv;

      TALER_denom_sig_deep_copy (&fc->sig,
                                 &coin->sig);
    }
    if (0 != rrs->total_backoff.rel_value_us)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "Total reveal backoff for %s was %s\n",
                  rrs->is->commands[rrs->is->ip].label,
                  GNUNET_STRINGS_relative_time_to_string (rrs->total_backoff,
                                                          GNUNET_YES));
    }
    break;
  default:
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Unknown HTTP status %u/%d\n",
                hr->http_status,
                (int) hr->ec);
  }
  TALER_TESTING_interpreter_next (rrs->is);
}


/**
 * Run the command.
 *
 * @param cls closure.
 * @param cmd the command to execute.
 * @param is the interpreter state.
 */
static void
refresh_reveal_run (void *cls,
                    const struct TALER_TESTING_Command *cmd,
                    struct TALER_TESTING_Interpreter *is)
{
  struct RefreshRevealState *rrs = cls;
  struct RefreshMeltState *rms;
  const struct TALER_TESTING_Command *melt_cmd;

  rrs->is = is;
  melt_cmd = TALER_TESTING_interpreter_lookup_command (is,
                                                       rrs->melt_reference);
  if (NULL == melt_cmd)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rrs->is);
    return;
  }
  // FIXME: use trait for 'rms'!
  rms = melt_cmd->cls;
  {
    struct TALER_ExchangeWithdrawValues alg_values[rms->num_fresh_coins];

    for (unsigned int i = 0; i<rms->num_fresh_coins; i++)
      alg_values[i] = rms->mbds[i].alg_value;
    rrs->rrh = TALER_EXCHANGE_refreshes_reveal (is->exchange,
                                                &rms->rms,
                                                &rms->refresh_data,
                                                rms->num_fresh_coins,
                                                alg_values,
                                                rms->noreveal_index,
                                                &reveal_cb,
                                                rrs);
  }
  if (NULL == rrs->rrh)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (is);
    return;
  }
}


/**
 * Free the state from a "refresh reveal" CMD, and possibly
 * cancel a pending operation thereof.
 *
 * @param cls closure.
 * @param cmd the command which is being cleaned up.
 */
static void
refresh_reveal_cleanup (void *cls,
                        const struct TALER_TESTING_Command *cmd)
{
  struct RefreshRevealState *rrs = cls;

  (void) cmd;
  if (NULL != rrs->rrh)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Command %u (%s) did not complete\n",
                rrs->is->ip,
                cmd->label);
    TALER_EXCHANGE_refreshes_reveal_cancel (rrs->rrh);
    rrs->rrh = NULL;
  }
  if (NULL != rrs->retry_task)
  {
    GNUNET_SCHEDULER_cancel (rrs->retry_task);
    rrs->retry_task = NULL;
  }

  for (unsigned int j = 0; j < rrs->num_fresh_coins; j++)
    TALER_denom_sig_free (&rrs->fresh_coins[j].sig);

  GNUNET_free (rrs->fresh_coins);
  GNUNET_free (rrs->psa);
  rrs->num_fresh_coins = 0;
  GNUNET_free (rrs);
}


/**
 * Run the command.
 *
 * @param cls closure.
 * @param cmd the command to execute.
 * @param is the interpreter state.
 */
static void
refresh_link_run (void *cls,
                  const struct TALER_TESTING_Command *cmd,
                  struct TALER_TESTING_Interpreter *is);


/**
 * Task scheduled to re-try #refresh_link_run.
 *
 * @param cls a `struct RefreshLinkState`
 */
static void
do_link_retry (void *cls)
{
  struct RefreshLinkState *rls = cls;

  rls->retry_task = NULL;
  rls->is->commands[rls->is->ip].last_req_time
    = GNUNET_TIME_absolute_get ();
  refresh_link_run (rls,
                    NULL,
                    rls->is);
}


/**
 * "refresh link" operation callback, checks that HTTP response
 * code is expected _and_ that all the linked coins were actually
 * withdrawn by the "refresh reveal" CMD.
 *
 * @param cls closure.
 * @param hr HTTP response details
 * @param num_coins number of fresh coins created, length of the
 *        @a sigs and @a coin_privs arrays, 0 if the operation
 *        failed.
 * @param coin_privs array of @a num_coins private keys for the
 *        coins that were created, NULL on error.
 * @param sigs array of signature over @a num_coins coins, NULL on
 *        error.
 * @param pubs array of public keys for the @a sigs,
 *        NULL on error.
 */
static void
link_cb (void *cls,
         const struct TALER_EXCHANGE_LinkResult *lr)
{
  struct RefreshLinkState *rls = cls;
  const struct TALER_EXCHANGE_HttpResponse *hr = &lr->hr;
  const struct TALER_TESTING_Command *reveal_cmd;
  struct TALER_TESTING_Command *link_cmd = &rls->is->commands[rls->is->ip];
  unsigned int found;
  const unsigned int *num_fresh_coins;

  rls->rlh = NULL;
  if (rls->expected_response_code != hr->http_status)
  {
    if (0 != rls->do_retry)
    {
      rls->do_retry--;
      if ( (0 == hr->http_status) ||
           (TALER_EC_GENERIC_DB_SOFT_FAILURE == hr->ec) ||
           (MHD_HTTP_INTERNAL_SERVER_ERROR == hr->http_status) )
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Retrying refresh link failed with %u/%d\n",
                    hr->http_status,
                    (int) hr->ec);
        /* on DB conflicts, do not use backoff */
        if (TALER_EC_GENERIC_DB_SOFT_FAILURE == hr->ec)
          rls->backoff = GNUNET_TIME_UNIT_ZERO;
        else
          rls->backoff = GNUNET_TIME_randomized_backoff (rls->backoff,
                                                         MAX_BACKOFF);
        rls->total_backoff = GNUNET_TIME_relative_add (rls->total_backoff,
                                                       rls->backoff);
        rls->is->commands[rls->is->ip].num_tries++;
        rls->retry_task = GNUNET_SCHEDULER_add_delayed (rls->backoff,
                                                        &do_link_retry,
                                                        rls);
        return;
      }
    }
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u/%d to command %s in %s:%u\n",
                hr->http_status,
                (int) hr->ec,
                link_cmd->label,
                __FILE__,
                __LINE__);
    json_dumpf (hr->reply,
                stderr,
                0);
    TALER_TESTING_interpreter_fail (rls->is);
    return;
  }
  reveal_cmd = TALER_TESTING_interpreter_lookup_command (rls->is,
                                                         rls->reveal_reference);
  if (NULL == reveal_cmd)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rls->is);
    return;
  }

  switch (hr->http_status)
  {
  case MHD_HTTP_OK:
    /* check that number of coins returned matches */
    if (GNUNET_OK !=
        TALER_TESTING_get_trait_array_length (reveal_cmd,
                                              &num_fresh_coins))
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rls->is);
      return;
    }
    if (lr->details.success.num_coins != *num_fresh_coins)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "Unexpected number of fresh coins: %d vs %d in %s:%u\n",
                  lr->details.success.num_coins,
                  *num_fresh_coins,
                  __FILE__,
                  __LINE__);
      TALER_TESTING_interpreter_fail (rls->is);
      return;
    }
    /* check that the coins match */
    for (unsigned int i = 0; i<lr->details.success.num_coins; i++)
      for (unsigned int j = i + 1; j<lr->details.success.num_coins; j++)
        if (0 ==
            GNUNET_memcmp (&lr->details.success.coins[i].coin_priv,
                           &lr->details.success.coins[j].coin_priv))
          GNUNET_break (0);
    /* Note: coins might be legitimately permutated in here... */
    found = 0;

    /* Will point to the pointer inside the cmd state. */
    {
      const struct TALER_TESTING_FreshCoinData **fc = NULL;

      if (GNUNET_OK !=
          TALER_TESTING_get_trait_fresh_coins (reveal_cmd,
                                               &fc))
      {
        GNUNET_break (0);
        TALER_TESTING_interpreter_fail (rls->is);
        return;
      }

      for (unsigned int i = 0; i<lr->details.success.num_coins; i++)
      {
        const struct TALER_EXCHANGE_LinkedCoinInfo *lci_i
          = &lr->details.success.coins[i];

        for (unsigned int j = 0; j<lr->details.success.num_coins; j++)
        {
          const struct TALER_TESTING_FreshCoinData *fcj
            = &(*fc)[j];

          if ( (0 ==
                GNUNET_memcmp (&fcj->coin_priv,
                               &lci_i->coin_priv)) &&
               (0 ==
                TALER_denom_sig_cmp (&fcj->sig,
                                     &lci_i->sig)) &&
               (0 ==
                TALER_denom_pub_cmp (&fcj->pk->key,
                                     &lci_i->pub)) )
          {
            found++;
            break;
          }
        } /* for j*/
      } /* for i */
    }
    if (found != lr->details.success.num_coins)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "Only %u/%u coins match expectations\n",
                  found,
                  lr->details.success.num_coins);
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rls->is);
      return;
    }
    if (0 != rls->total_backoff.rel_value_us)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "Total link backoff for %s was %s\n",
                  rls->is->commands[rls->is->ip].label,
                  GNUNET_STRINGS_relative_time_to_string (rls->total_backoff,
                                                          GNUNET_YES));
    }
    break;
  default:
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unknown HTTP response code %u/%d.\n",
                hr->http_status,
                hr->ec);
  }
  TALER_TESTING_interpreter_next (rls->is);
}


/**
 * Run the command.
 *
 * @param cls closure.
 * @param cmd the command to execute.
 * @param is the interpreter state.
 */
static void
refresh_link_run (void *cls,
                  const struct TALER_TESTING_Command *cmd,
                  struct TALER_TESTING_Interpreter *is)
{
  struct RefreshLinkState *rls = cls;
  struct RefreshRevealState *rrs;
  struct RefreshMeltState *rms;
  const struct TALER_TESTING_Command *reveal_cmd;
  const struct TALER_TESTING_Command *melt_cmd;
  const struct TALER_TESTING_Command *coin_cmd;

  (void) cmd;
  rls->is = is;
  reveal_cmd = TALER_TESTING_interpreter_lookup_command (rls->is,
                                                         rls->reveal_reference);
  if (NULL == reveal_cmd)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rls->is);
    return;
  }
  rrs = reveal_cmd->cls;
  melt_cmd = TALER_TESTING_interpreter_lookup_command (rls->is,
                                                       rrs->melt_reference);
  if (NULL == melt_cmd)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rls->is);
    return;
  }

  /* find reserve_withdraw command */
  {
    // FIXME: use trait!
    rms = melt_cmd->cls;
    coin_cmd = TALER_TESTING_interpreter_lookup_command (rls->is,
                                                         rms->coin_reference);
    if (NULL == coin_cmd)
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rls->is);
      return;
    }
  }

  const struct TALER_CoinSpendPrivateKeyP *coin_priv;
  if (GNUNET_OK !=
      TALER_TESTING_get_trait_coin_priv (coin_cmd,
                                         0,
                                         &coin_priv))
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rls->is);
    return;
  }

  /* finally, use private key from withdraw sign command */
  rls->rlh = TALER_EXCHANGE_link (is->exchange,
                                  coin_priv,
                                  rms->age_commitment,
                                  &link_cb,
                                  rls);

  if (NULL == rls->rlh)
  {
    GNUNET_break (0);
    TALER_TESTING_interpreter_fail (rls->is);
    return;
  }
}


/**
 * Free the state of the "refresh link" CMD, and possibly
 * cancel a operation thereof.
 *
 * @param cls closure
 * @param cmd the command which is being cleaned up.
 */
static void
refresh_link_cleanup (void *cls,
                      const struct TALER_TESTING_Command *cmd)
{
  struct RefreshLinkState *rls = cls;

  if (NULL != rls->rlh)
  {

    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Command %u (%s) did not complete\n",
                rls->is->ip,
                cmd->label);
    TALER_EXCHANGE_link_cancel (rls->rlh);
    rls->rlh = NULL;
  }
  if (NULL != rls->retry_task)
  {
    GNUNET_SCHEDULER_cancel (rls->retry_task);
    rls->retry_task = NULL;
  }
  GNUNET_free (rls);
}


/**
 * Run the command.
 *
 * @param cls closure.
 * @param cmd the command to execute.
 * @param is the interpreter state.
 */
static void
melt_run (void *cls,
          const struct TALER_TESTING_Command *cmd,
          struct TALER_TESTING_Interpreter *is);


/**
 * Task scheduled to re-try #melt_run.
 *
 * @param cls a `struct RefreshMeltState`
 */
static void
do_melt_retry (void *cls)
{
  struct RefreshMeltState *rms = cls;

  rms->retry_task = NULL;
  rms->is->commands[rms->is->ip].last_req_time
    = GNUNET_TIME_absolute_get ();
  melt_run (rms,
            NULL,
            rms->is);
}


/**
 * Callback for a "refresh melt" operation; checks if the HTTP
 * response code is okay and re-run the melt operation if the
 * CMD was set to do so.
 *
 * @param cls closure.
 * @param mr melt response details
 */
static void
melt_cb (void *cls,
         const struct TALER_EXCHANGE_MeltResponse *mr)
{
  struct RefreshMeltState *rms = cls;
  const struct TALER_EXCHANGE_HttpResponse *hr = &mr->hr;

  rms->rmh = NULL;
  if (rms->expected_response_code != hr->http_status)
  {
    if (0 != rms->do_retry)
    {
      rms->do_retry--;
      if ( (0 == hr->http_status) ||
           (TALER_EC_GENERIC_DB_SOFT_FAILURE == hr->ec) ||
           (MHD_HTTP_INTERNAL_SERVER_ERROR == hr->http_status) )
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Retrying refresh melt failed with %u/%d\n",
                    hr->http_status,
                    (int) hr->ec);
        /* on DB conflicts, do not use backoff */
        if (TALER_EC_GENERIC_DB_SOFT_FAILURE == hr->ec)
          rms->backoff = GNUNET_TIME_UNIT_ZERO;
        else
          rms->backoff = GNUNET_TIME_randomized_backoff (rms->backoff,
                                                         MAX_BACKOFF);
        rms->total_backoff = GNUNET_TIME_relative_add (rms->total_backoff,
                                                       rms->backoff);
        rms->is->commands[rms->is->ip].num_tries++;
        rms->retry_task = GNUNET_SCHEDULER_add_delayed (rms->backoff,
                                                        &do_melt_retry,
                                                        rms);
        return;
      }
    }
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u/%d to command %s in %s:%u\n",
                hr->http_status,
                (int) hr->ec,
                rms->is->commands[rms->is->ip].label,
                __FILE__,
                __LINE__);
    json_dumpf (hr->reply,
                stderr,
                0);
    TALER_TESTING_interpreter_fail (rms->is);
    return;
  }
  if (MHD_HTTP_OK == hr->http_status)
  {
    rms->noreveal_index = mr->details.success.noreveal_index;
    if (mr->details.success.num_mbds != rms->num_fresh_coins)
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }
    GNUNET_free (rms->mbds);
    rms->mbds = GNUNET_memdup (mr->details.success.mbds,
                               mr->details.success.num_mbds
                               * sizeof (struct
                                         TALER_EXCHANGE_MeltBlindingDetail));
  }
  if (0 != rms->total_backoff.rel_value_us)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Total melt backoff for %s was %s\n",
                rms->is->commands[rms->is->ip].label,
                GNUNET_STRINGS_relative_time_to_string (rms->total_backoff,
                                                        GNUNET_YES));
  }
  if (rms->double_melt)
  {
    TALER_LOG_DEBUG ("Doubling the melt (%s)\n",
                     rms->is->commands[rms->is->ip].label);
    rms->rmh = TALER_EXCHANGE_melt (rms->is->exchange,
                                    &rms->rms,
                                    &rms->refresh_data,
                                    &melt_cb,
                                    rms);
    rms->double_melt = false;
    return;
  }
  TALER_TESTING_interpreter_next (rms->is);
}


/**
 * Run the command.
 *
 * @param cls closure.
 * @param cmd the command to execute.
 * @param is the interpreter state.
 */
static void
melt_run (void *cls,
          const struct TALER_TESTING_Command *cmd,
          struct TALER_TESTING_Interpreter *is)
{
  struct RefreshMeltState *rms = cls;
  unsigned int num_fresh_coins;
  const char *default_melt_fresh_amounts[] = {
    "EUR:1", "EUR:1", "EUR:1", "EUR:0.1",
    NULL
  };
  const char **melt_fresh_amounts;

  (void) cmd;
  if (NULL == (melt_fresh_amounts = rms->melt_fresh_amounts))
    melt_fresh_amounts = default_melt_fresh_amounts;
  rms->is = is;
  rms->noreveal_index = UINT16_MAX;
  TALER_refresh_master_setup_random (&rms->rms);
  for (num_fresh_coins = 0;
       NULL != melt_fresh_amounts[num_fresh_coins];
       num_fresh_coins++)
    ;
  rms->num_fresh_coins = num_fresh_coins;
  rms->fresh_pks = GNUNET_new_array (
    num_fresh_coins,
    struct TALER_EXCHANGE_DenomPublicKey);
  {
    struct TALER_Amount melt_amount;
    struct TALER_Amount fresh_amount;
    const struct TALER_DenominationSignature *melt_sig;
    const struct TALER_EXCHANGE_DenomPublicKey *melt_denom_pub;
    const struct TALER_TESTING_Command *coin_command;
    bool age_restricted;

    if (NULL == (coin_command
                   = TALER_TESTING_interpreter_lookup_command (
                       is,
                       rms->coin_reference)))
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }

    if (GNUNET_OK !=
        TALER_TESTING_get_trait_coin_priv (coin_command,
                                           0,
                                           &rms->melt_priv))
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }
    if (GNUNET_OK !=
        TALER_TESTING_get_trait_age_commitment (coin_command,
                                                0,
                                                &rms->age_commitment))
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }

    if (GNUNET_OK !=
        TALER_TESTING_get_trait_denom_sig (coin_command,
                                           0,
                                           &melt_sig))
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }

    if (GNUNET_OK !=
        TALER_TESTING_get_trait_denom_pub (coin_command,
                                           0,
                                           &melt_denom_pub))
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }

    /* Melt amount starts with the melt fee of the old coin; we'll add the
       values and withdraw fees of the fresh coins next */
    melt_amount = melt_denom_pub->fees.refresh;
    age_restricted = melt_denom_pub->key.age_mask.mask != 0;
    for (unsigned int i = 0; i<num_fresh_coins; i++)
    {
      const struct TALER_EXCHANGE_DenomPublicKey *fresh_pk;

      if (GNUNET_OK !=
          TALER_string_to_amount (melt_fresh_amounts[i],
                                  &fresh_amount))
      {
        GNUNET_break (0);
        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                    "Failed to parse amount `%s' at index %u\n",
                    melt_fresh_amounts[i],
                    i);
        TALER_TESTING_interpreter_fail (rms->is);
        return;
      }
      fresh_pk = TALER_TESTING_find_pk (TALER_EXCHANGE_get_keys (is->exchange),
                                        &fresh_amount,
                                        age_restricted);
      if (NULL == fresh_pk)
      {
        GNUNET_break (0);
        /* Subroutine logs specific error */
        TALER_TESTING_interpreter_fail (rms->is);
        return;
      }
      GNUNET_assert (0 <=
                     TALER_amount_add (&melt_amount,
                                       &melt_amount,
                                       &fresh_amount));
      GNUNET_assert (0 <=
                     TALER_amount_add (&melt_amount,
                                       &melt_amount,
                                       &fresh_pk->fees.withdraw));
      rms->fresh_pks[i] = *fresh_pk;
      /* Make a deep copy of the RSA key */
      TALER_denom_pub_deep_copy (&rms->fresh_pks[i].key,
                                 &fresh_pk->key);
    } /* end for */

    rms->refresh_data.melt_priv = *rms->melt_priv;
    rms->refresh_data.melt_amount = melt_amount;
    rms->refresh_data.melt_sig = *melt_sig;
    rms->refresh_data.melt_pk = *melt_denom_pub;
    rms->refresh_data.fresh_pks = rms->fresh_pks;
    rms->refresh_data.fresh_pks_len = num_fresh_coins;
    rms->refresh_data.age_commitment = NULL;

    GNUNET_assert (age_restricted ==
                   (NULL != rms->age_commitment));

    if (NULL != rms->age_commitment)
    {
      struct TALER_AgeCommitment *ac;
      uint32_t seed;

      ac = GNUNET_new (struct TALER_AgeCommitment);
      seed  = GNUNET_CRYPTO_random_u32 (
        GNUNET_CRYPTO_QUALITY_WEAK,
        UINT32_MAX);

      GNUNET_assert (GNUNET_OK ==
                     TALER_age_commitment_derive (
                       rms->age_commitment,
                       seed,
                       ac));

      rms->refresh_data.age_commitment = ac;
    }

    rms->rmh = TALER_EXCHANGE_melt (is->exchange,
                                    &rms->rms,
                                    &rms->refresh_data,
                                    &melt_cb,
                                    rms);

    if (NULL == rms->rmh)
    {
      GNUNET_break (0);
      TALER_TESTING_interpreter_fail (rms->is);
      return;
    }
  }
}


/**
 * Free the "refresh melt" CMD state, and possibly cancel a
 * pending operation thereof.
 *
 * @param cls closure, must be a `struct RefreshMeltState`.
 * @param cmd the command which is being cleaned up.
 */
static void
melt_cleanup (void *cls,
              const struct TALER_TESTING_Command *cmd)
{
  struct RefreshMeltState *rms = cls;

  (void) cmd;
  if (NULL != rms->rmh)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Command %u (%s) did not complete\n",
                rms->is->ip,
                rms->is->commands[rms->is->ip].label);
    TALER_EXCHANGE_melt_cancel (rms->rmh);
    rms->rmh = NULL;
  }
  if (NULL != rms->retry_task)
  {
    GNUNET_SCHEDULER_cancel (rms->retry_task);
    rms->retry_task = NULL;
  }
  if (NULL != rms->fresh_pks)
  {
    for (unsigned int i = 0; i < rms->num_fresh_coins; i++)
      TALER_denom_pub_free (&rms->fresh_pks[i].key);
    GNUNET_free (rms->fresh_pks);
  }
  GNUNET_free (rms->mbds);
  GNUNET_free (rms->melt_fresh_amounts);
  GNUNET_free (rms);
}


/**
 * Offer internal data to the "refresh melt" CMD.
 *
 * @param cls closure.
 * @param[out] ret result (could be anything).
 * @param trait name of the trait.
 * @param index index number of the object to offer.
 * @return #GNUNET_OK on success.
 */
static enum GNUNET_GenericReturnValue
melt_traits (void *cls,
             const void **ret,
             const char *trait,
             unsigned int index)
{
  struct RefreshMeltState *rms = cls;

  if (index >= rms->num_fresh_coins)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  {
    struct TALER_TESTING_Trait traits[] = {
      TALER_TESTING_make_trait_denom_pub (index,
                                          &rms->fresh_pks[index]),
      TALER_TESTING_make_trait_coin_priv (0,
                                          rms->melt_priv),
      TALER_TESTING_make_trait_age_commitment (index,
                                               rms->age_commitment),
      TALER_TESTING_make_trait_exchange_wd_value (index,
                                                  &rms->mbds[index].alg_value),
      TALER_TESTING_make_trait_refresh_secret (&rms->rms),
      TALER_TESTING_trait_end ()
    };

    return TALER_TESTING_get_trait (traits,
                                    ret,
                                    trait,
                                    index);
  }
}


/**
 * Parse list of amounts for melt operation.
 *
 * @param[in,out] rms where to store the list
 * @param ap NULL-termianted list of amounts to be melted (one per fresh coin)
 * @return #GNUNET_OK on success
 */
static enum GNUNET_GenericReturnValue
parse_amounts (struct RefreshMeltState *rms,
               va_list ap)
{
  unsigned int len;
  unsigned int off;
  const char *amount;

  len = 0;
  off = 0;
  while (NULL != (amount = va_arg (ap, const char *)))
  {
    if (len == off)
    {
      struct TALER_Amount a;

      GNUNET_array_grow (rms->melt_fresh_amounts,
                         len,
                         off + 16);
      if (GNUNET_OK !=
          TALER_string_to_amount (amount, &a))
      {
        GNUNET_break (0);
        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                    "Failed to parse amount `%s' at index %u\n",
                    amount, off);
        GNUNET_free (rms->melt_fresh_amounts);
        rms->melt_fresh_amounts = NULL;
        return GNUNET_SYSERR;
      }
      rms->melt_fresh_amounts[off++] = amount;
    }
  }
  if (0 == off)
    return GNUNET_OK; /* no amounts given == use defaults! */
  /* ensure NULL-termination */
  GNUNET_array_grow (rms->melt_fresh_amounts,
                     len,
                     off + 1);
  return GNUNET_OK;
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_melt (const char *label,
                        const char *coin_reference,
                        unsigned int expected_response_code,
                        ...)
{
  struct RefreshMeltState *rms;
  va_list ap;

  rms = GNUNET_new (struct RefreshMeltState);
  rms->coin_reference = coin_reference;
  rms->expected_response_code = expected_response_code;
  va_start (ap,
            expected_response_code);
  GNUNET_assert (GNUNET_OK ==
                 parse_amounts (rms, ap));
  va_end (ap);
  {
    struct TALER_TESTING_Command cmd = {
      .label = label,
      .cls = rms,
      .run = &melt_run,
      .cleanup = &melt_cleanup,
      .traits = &melt_traits
    };

    return cmd;
  }
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_melt_double (const char *label,
                               const char *coin_reference,
                               unsigned int expected_response_code,
                               ...)
{
  struct RefreshMeltState *rms;
  va_list ap;

  rms = GNUNET_new (struct RefreshMeltState);
  rms->coin_reference = coin_reference;
  rms->expected_response_code = expected_response_code;
  rms->double_melt = true;
  va_start (ap,
            expected_response_code);
  GNUNET_assert (GNUNET_OK ==
                 parse_amounts (rms, ap));
  va_end (ap);
  {
    struct TALER_TESTING_Command cmd = {
      .label = label,
      .cls = rms,
      .run = &melt_run,
      .cleanup = &melt_cleanup,
      .traits = &melt_traits
    };

    return cmd;
  }
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_melt_with_retry (struct TALER_TESTING_Command cmd)
{
  struct RefreshMeltState *rms;

  GNUNET_assert (&melt_run == cmd.run);
  rms = cmd.cls;
  rms->do_retry = NUM_RETRIES;
  return cmd;
}


/**
 * Offer internal data from a "refresh reveal" CMD.
 *
 * @param cls closure.
 * @param[out] ret result (could be anything).
 * @param trait name of the trait.
 * @param index index number of the object to offer.
 * @return #GNUNET_OK on success.
 */
static enum GNUNET_GenericReturnValue
refresh_reveal_traits (void *cls,
                       const void **ret,
                       const char *trait,
                       unsigned int index)
{
  struct RefreshRevealState *rrs = cls;

  if (index >= rrs->num_fresh_coins)
    return GNUNET_SYSERR;
  {
    struct TALER_TESTING_Trait traits[] = {
      TALER_TESTING_make_trait_coin_priv (
        index,
        &rrs->fresh_coins[index].coin_priv),
      TALER_TESTING_make_trait_age_commitment (
        index,
        rrs->fresh_coins[index].age_commitment),
      TALER_TESTING_make_trait_denom_pub (
        index,
        rrs->fresh_coins[index].pk),
      TALER_TESTING_make_trait_denom_sig (
        index,
        &rrs->fresh_coins[index].sig),
      TALER_TESTING_make_trait_blinding_key (
        index,
        &rrs->fresh_coins[index].blinding_key),
      TALER_TESTING_make_trait_array_length (
        &rrs->num_fresh_coins),
      TALER_TESTING_make_trait_fresh_coins (
        (const struct TALER_TESTING_FreshCoinData **) &rrs->fresh_coins),
      TALER_TESTING_make_trait_planchet_secrets (index,
                                                 &rrs->psa[index]),
      TALER_TESTING_trait_end ()
    };

    return TALER_TESTING_get_trait (traits,
                                    ret,
                                    trait,
                                    index);
  }
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_refresh_reveal (const char *label,
                                  const char *melt_reference,
                                  unsigned int expected_response_code)
{
  struct RefreshRevealState *rrs;

  rrs = GNUNET_new (struct RefreshRevealState);
  rrs->melt_reference = melt_reference;
  rrs->expected_response_code = expected_response_code;
  {
    struct TALER_TESTING_Command cmd = {
      .cls = rrs,
      .label = label,
      .run = &refresh_reveal_run,
      .cleanup = &refresh_reveal_cleanup,
      .traits = &refresh_reveal_traits
    };

    return cmd;
  }
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_refresh_reveal_with_retry (struct TALER_TESTING_Command cmd)
{
  struct RefreshRevealState *rrs;

  GNUNET_assert (&refresh_reveal_run == cmd.run);
  rrs = cmd.cls;
  rrs->do_retry = NUM_RETRIES;
  return cmd;
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_refresh_link (const char *label,
                                const char *reveal_reference,
                                unsigned int expected_response_code)
{
  struct RefreshLinkState *rrs;

  rrs = GNUNET_new (struct RefreshLinkState);
  rrs->reveal_reference = reveal_reference;
  rrs->expected_response_code = expected_response_code;
  {
    struct TALER_TESTING_Command cmd = {
      .cls = rrs,
      .label = label,
      .run = &refresh_link_run,
      .cleanup = &refresh_link_cleanup
    };

    return cmd;
  }
}


struct TALER_TESTING_Command
TALER_TESTING_cmd_refresh_link_with_retry (struct TALER_TESTING_Command cmd)
{
  struct RefreshLinkState *rls;

  GNUNET_assert (&refresh_link_run == cmd.run);
  rls = cmd.cls;
  rls->do_retry = NUM_RETRIES;
  return cmd;
}