/*
  This file is part of TALER
  Copyright (C) 2014-2017 GNUnet e.V.

  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 taler-exchange-httpd_db.c
 * @brief Generic database operations for the exchange.
 * @author Christian Grothoff
 */
#include "platform.h"
#include <pthread.h>
#include <jansson.h>
#include <gnunet/gnunet_json_lib.h>
#include "taler_json_lib.h"
#include "taler-exchange-httpd_responses.h"
#include "taler-exchange-httpd_keystate.h"

/**
 * How often should we retry a transaction before giving up
 * (for transactions resulting in serialization/dead locks only).
 */
#define MAX_TRANSACTION_COMMIT_RETRIES 100


/**
 * Execute database transaction to ensure coin is known. Run the transaction
 * logic; IF it returns a non-error code, the transaction logic MUST
 * NOT queue a MHD response.  IF it returns an hard error, the
 * transaction logic MUST queue a MHD response and set @a mhd_ret.  IF
 * it returns the soft error code, the function MAY be called again to
 * retry and MUST not queue a MHD response.
 *
 * @param cls a `struct DepositContext`
 * @param connection MHD request context
 * @param session database session and transaction to use
 * @param[out] mhd_ret set to MHD status on error
 * @return transaction status
 */
enum GNUNET_DB_QueryStatus
TEH_DB_know_coin_transaction (void *cls,
                              struct MHD_Connection *connection,
                              struct TALER_EXCHANGEDB_Session *session,
                              int *mhd_ret)
{
  struct TEH_DB_KnowCoinContext *kcc = cls;
  enum GNUNET_DB_QueryStatus qs;

  qs = TEH_plugin->ensure_coin_known (TEH_plugin->cls,
                                      session,
                                      kcc->coin);
  if (GNUNET_DB_STATUS_HARD_ERROR == qs)
  {
    *mhd_ret
      = TEH_RESPONSE_reply_internal_db_error (connection,
                                              TALER_EC_DB_COIN_HISTORY_STORE_ERROR);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  return qs;
}


/**
 * Run a database transaction for @a connection.
 * Starts a transaction and calls @a cb.  Upon success,
 * attempts to commit the transaction.  Upon soft failures,
 * retries @a cb a few times.  Upon hard or persistent soft
 * errors, generates an error message for @a connection.
 *
 * @param connection MHD connection to run @a cb for
 * @param name name of the transaction (for debugging)
 * @param[out] set to MHD response code, if transaction failed
 * @param cb callback implementing transaction logic
 * @param cb_cls closure for @a cb, must be read-only!
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
 */
int
TEH_DB_run_transaction (struct MHD_Connection *connection,
                        const char *name,
                        int *mhd_ret,
                        TEH_DB_TransactionCallback cb,
                        void *cb_cls)
{
  struct TALER_EXCHANGEDB_Session *session;

  if (NULL != mhd_ret)
    *mhd_ret = -1; /* invalid value */
  if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
  {
    GNUNET_break (0);
    if (NULL != mhd_ret)
      *mhd_ret = TEH_RESPONSE_reply_internal_db_error (connection,
                                                       TALER_EC_DB_SETUP_FAILED);
    return GNUNET_SYSERR;
  }
  TEH_plugin->preflight (TEH_plugin->cls,
                         session);
  for (unsigned int retries = 0; retries < MAX_TRANSACTION_COMMIT_RETRIES;
       retries++)
  {
    enum GNUNET_DB_QueryStatus qs;

    if (GNUNET_OK !=
        TEH_plugin->start (TEH_plugin->cls,
                           session,
                           name))
    {
      GNUNET_break (0);
      if (NULL != mhd_ret)
        *mhd_ret = TEH_RESPONSE_reply_internal_db_error (connection,
                                                         TALER_EC_DB_START_FAILED);
      return GNUNET_SYSERR;
    }
    qs = cb (cb_cls,
             connection,
             session,
             mhd_ret);
    if (0 > qs)
      TEH_plugin->rollback (TEH_plugin->cls,
                            session);
    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      return GNUNET_SYSERR;
    if (0 <= qs)
      qs = TEH_plugin->commit (TEH_plugin->cls,
                               session);
    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
    {
      if (NULL != mhd_ret)
        *mhd_ret = TEH_RESPONSE_reply_commit_error (connection,
                                                    TALER_EC_DB_COMMIT_FAILED_HARD);
      return GNUNET_SYSERR;
    }
    /* make sure callback did not violate invariants! */
    GNUNET_assert ( (NULL == mhd_ret) ||
                    (-1 == *mhd_ret) );
    if (0 <= qs)
      return GNUNET_OK;
  }
  TALER_LOG_ERROR ("Transaction `%s' commit failed %u times\n",
                   name,
                   MAX_TRANSACTION_COMMIT_RETRIES);
  if (NULL != mhd_ret)
    *mhd_ret = TEH_RESPONSE_reply_commit_error (connection,
                                                TALER_EC_DB_COMMIT_FAILED_ON_RETRY);
  return GNUNET_SYSERR;
}


/**
 * Calculate the total value of all transactions performed.
 * Stores @a off plus the cost of all transactions in @a tl
 * in @a ret.
 *
 * @param tl transaction list to process
 * @param off offset to use as the starting value
 * @param[out] ret where the resulting total is to be stored
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on errors
 */
// FIXME: maybe move to another module, i.e. exchangedb???
int
TEH_DB_calculate_transaction_list_totals (struct
                                          TALER_EXCHANGEDB_TransactionList *tl,
                                          const struct TALER_Amount *off,
                                          struct TALER_Amount *ret)
{
  struct TALER_Amount spent = *off;
  struct TALER_Amount refunded;

  GNUNET_assert (GNUNET_OK ==
                 TALER_amount_get_zero (spent.currency,
                                        &refunded));
  for (struct TALER_EXCHANGEDB_TransactionList *pos = tl; NULL != pos; pos =
         pos->next)
  {
    switch (pos->type)
    {
    case TALER_EXCHANGEDB_TT_DEPOSIT:
      /* spent += pos->amount_with_fee */
      if (GNUNET_OK !=
          TALER_amount_add (&spent,
                            &spent,
                            &pos->details.deposit->amount_with_fee))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      break;
    case TALER_EXCHANGEDB_TT_REFRESH_MELT:
      /* spent += pos->amount_with_fee */
      if (GNUNET_OK !=
          TALER_amount_add (&spent,
                            &spent,
                            &pos->details.melt->session.amount_with_fee))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      break;
    case TALER_EXCHANGEDB_TT_REFUND:
      /* refunded += pos->refund_amount - pos->refund_fee */
      if (GNUNET_OK !=
          TALER_amount_add (&refunded,
                            &refunded,
                            &pos->details.refund->refund_amount))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      if (GNUNET_OK !=
          TALER_amount_subtract (&refunded,
                                 &refunded,
                                 &pos->details.refund->refund_fee))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      break;
    case TALER_EXCHANGEDB_TT_OLD_COIN_PAYBACK:
      /* refunded += pos->value */
      if (GNUNET_OK !=
          TALER_amount_add (&refunded,
                            &refunded,
                            &pos->details.old_coin_payback->value))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      break;
    case TALER_EXCHANGEDB_TT_PAYBACK:
      /* spent += pos->value */
      if (GNUNET_OK !=
          TALER_amount_add (&spent,
                            &spent,
                            &pos->details.payback->value))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      break;
    case TALER_EXCHANGEDB_TT_PAYBACK_REFRESH:
      /* spent += pos->value */
      if (GNUNET_OK !=
          TALER_amount_add (&spent,
                            &spent,
                            &pos->details.payback_refresh->value))
      {
        GNUNET_break (0);
        return GNUNET_SYSERR;
      }
      break;
    }
  }
  /* spent = spent - refunded */
  if (GNUNET_SYSERR ==
      TALER_amount_subtract (&spent,
                             &spent,
                             &refunded))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }

  *ret = spent;
  return GNUNET_OK;
}


/* end of taler-exchange-httpd_db.c */