/*
   This file is part of TALER
   Copyright (C) 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 backenddb/pg_authorize_reward.c
 * @brief Implementation of the authorize_reward function for Postgres
 * @author Christian Grothoff
 */
#include "platform.h"
#include <taler/taler_error_codes.h>
#include <taler/taler_dbevents.h>
#include <taler/taler_pq_lib.h>
#include "pg_authorize_reward.h"
#include "pg_helper.h"


/**
 * How often do we re-try if we run into a DB serialization error?
 */
#define MAX_RETRIES 3


/**
 * Closure for #lookup_reserve_for_reward_cb().
 */
struct LookupReserveForRewardContext
{
  /**
   * Postgres context.
   */
  struct PostgresClosure *pg;

  /**
   * Public key of the reserve we found.
   */
  struct TALER_ReservePublicKeyP reserve_pub;

  /**
   * How much money must be left in the reserve.
   */
  struct TALER_Amount required_amount;

  /**
   * Set to the expiration time of the reserve we found.
   * #GNUNET_TIME_UNIT_FOREVER_ABS if we found none.
   */
  struct GNUNET_TIME_Timestamp expiration;

  /**
   * Error status.
   */
  enum TALER_ErrorCode ec;

  /**
   * Did we find a good reserve?
   */
  bool ok;
};


/**
 * How long must a reserve be at least still valid before we use
 * it for a reward?
 */
#define MIN_EXPIRATION GNUNET_TIME_UNIT_HOURS


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results about accounts.
 *
 * @param[in,out] cls of type `struct LookupReserveForRewardContext *`
 * @param result the postgres result
 * @param num_results the number of results in @a result
 */
static void
lookup_reserve_for_reward_cb (void *cls,
                              PGresult *result,
                              unsigned int num_results)
{
  struct LookupReserveForRewardContext *lac = cls;

  for (unsigned int i = 0; i < num_results; i++)
  {
    struct TALER_ReservePublicKeyP reserve_pub;
    struct TALER_Amount committed_amount;
    struct TALER_Amount remaining;
    struct TALER_Amount initial_balance;
    struct GNUNET_TIME_Timestamp expiration;
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_auto_from_type ("reserve_pub",
                                            &reserve_pub),
      TALER_PQ_result_spec_amount_with_currency ("exchange_initial_balance",
                                                 &initial_balance),
      TALER_PQ_result_spec_amount_with_currency ("rewards_committed",
                                                 &committed_amount),
      GNUNET_PQ_result_spec_timestamp ("expiration",
                                       &expiration),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      lac->ec = TALER_EC_GENERIC_DB_FETCH_FAILED;
      return;
    }
    if (0 >
        TALER_amount_subtract (&remaining,
                               &initial_balance,
                               &committed_amount))
    {
      GNUNET_break (0);
      continue;
    }
    if (0 >
        TALER_amount_cmp (&remaining,
                          &lac->required_amount))
    {
      /* insufficient balance */
      if (lac->ok)
        continue;  /* got another reserve */
      lac->ec =
        TALER_EC_MERCHANT_PRIVATE_POST_REWARD_AUTHORIZE_INSUFFICIENT_FUNDS;
      continue;
    }
    if ( (! GNUNET_TIME_absolute_is_never (lac->expiration.abs_time)) &&
         GNUNET_TIME_timestamp_cmp (expiration,
                                    >,
                                    lac->expiration) &&
         GNUNET_TIME_relative_cmp (
           GNUNET_TIME_absolute_get_remaining (lac->expiration.abs_time),
           >,
           MIN_EXPIRATION) )
    {
      /* reserve expired */
      if (lac->ok)
        continue; /* got another reserve */
      lac->ec = TALER_EC_MERCHANT_PRIVATE_POST_REWARD_AUTHORIZE_RESERVE_EXPIRED;
      continue;
    }
    lac->ok = true;
    lac->ec = TALER_EC_NONE;
    lac->expiration = expiration;
    lac->reserve_pub = reserve_pub;
  }
}


enum TALER_ErrorCode
TMH_PG_authorize_reward (void *cls,
                         const char *instance_id,
                         const struct TALER_ReservePublicKeyP *reserve_pub,
                         const struct TALER_Amount *amount,
                         const char *justification,
                         const char *next_url,
                         struct TALER_RewardIdentifierP *reward_id,
                         struct GNUNET_TIME_Timestamp *expiration)
{
  struct PostgresClosure *pg = cls;
  unsigned int retries = 0;
  enum GNUNET_DB_QueryStatus qs;
  struct TALER_Amount rewards_committed;
  struct TALER_Amount exchange_initial_balance;
  const struct TALER_ReservePublicKeyP *reserve_pubp;
  struct LookupReserveForRewardContext lac = {
    .pg = pg,
    .required_amount = *amount,
    .expiration = GNUNET_TIME_UNIT_FOREVER_TS
  };

  check_connection (pg);
  PREPARE (pg,
           "lookup_reserve_for_reward",
           "SELECT"
           " reserve_pub"
           ",expiration"
           ",exchange_initial_balance"
           ",rewards_committed"
           " FROM merchant_reward_reserves"
           " WHERE"
           "   merchant_serial ="
           "     (SELECT merchant_serial"
           "        FROM merchant_instances"
           "       WHERE merchant_id=$1)");
  PREPARE (pg,
           "lookup_reserve_status",
           "SELECT"
           " expiration"
           ",exchange_initial_balance"
           ",rewards_committed"
           " FROM merchant_reward_reserves"
           " WHERE reserve_pub = $2"
           "   AND merchant_serial ="
           "     (SELECT merchant_serial"
           "        FROM merchant_instances"
           "       WHERE merchant_id=$1)");
  PREPARE (pg,
           "update_reserve_rewards_committed",
           "UPDATE merchant_reward_reserves SET"
           " rewards_committed=$3"
           " WHERE reserve_pub=$2"
           "   AND merchant_serial ="
           "     (SELECT merchant_serial"
           "        FROM merchant_instances"
           "       WHERE merchant_id=$1)");
  PREPARE (pg,
           "insert_reward",
           "INSERT INTO merchant_rewards"
           "(reserve_serial"
           ",reward_id"
           ",justification"
           ",next_url"
           ",expiration"
           ",amount"
           ",picked_up"
           ") "
           "SELECT"
           " reserve_serial, $3, $4, $5, $6, $7, $8"
           " FROM merchant_reward_reserves"
           " WHERE reserve_pub=$2"
           "  AND merchant_serial = "
           "     (SELECT merchant_serial"
           "        FROM merchant_instances"
           "       WHERE merchant_id=$1)");
RETRY:
  reserve_pubp = reserve_pub;
  if (MAX_RETRIES < ++retries)
  {
    GNUNET_break (0);
    return
      TALER_EC_GENERIC_DB_SOFT_FAILURE;
  }
  if (GNUNET_OK !=
      TMH_PG_start (pg,
                    "authorize reward"))
  {
    GNUNET_break (0);
    return TALER_EC_GENERIC_DB_START_FAILED;
  }
  if (NULL == reserve_pubp)
  {
    struct GNUNET_PQ_QueryParam params[] = {
      GNUNET_PQ_query_param_string (instance_id),
      GNUNET_PQ_query_param_end
    };

    qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
                                               "lookup_reserve_for_reward",
                                               params,
                                               &lookup_reserve_for_reward_cb,
                                               &lac);
    switch (qs)
    {
    case GNUNET_DB_STATUS_SOFT_ERROR:
      TMH_PG_rollback (pg);
      goto RETRY;
    case GNUNET_DB_STATUS_HARD_ERROR:
      GNUNET_break (0);
      TMH_PG_rollback (pg);
      return TALER_EC_GENERIC_DB_FETCH_FAILED;
    case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
      TMH_PG_rollback (pg);
      return TALER_EC_MERCHANT_PRIVATE_POST_REWARD_AUTHORIZE_RESERVE_NOT_FOUND;
    case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
    default:
      break;
    }
    if (TALER_EC_NONE  != lac.ec)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  "Enabling reward reserved failed with status %d\n",
                  lac.ec);
      TMH_PG_rollback (pg);
      return lac.ec;
    }
    GNUNET_assert (lac.ok);
    reserve_pubp = &lac.reserve_pub;
  }

  {
    struct GNUNET_PQ_QueryParam params[] = {
      GNUNET_PQ_query_param_string (instance_id),
      GNUNET_PQ_query_param_auto_from_type (reserve_pubp),
      GNUNET_PQ_query_param_end
    };
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_timestamp ("expiration",
                                       expiration),
      TALER_PQ_result_spec_amount_with_currency ("rewards_committed",
                                                 &rewards_committed),
      TALER_PQ_result_spec_amount_with_currency ("exchange_initial_balance",
                                                 &exchange_initial_balance),
      GNUNET_PQ_result_spec_end
    };

    qs = GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
                                                   "lookup_reserve_status",
                                                   params,
                                                   rs);
    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
    {
      TMH_PG_rollback (pg);
      goto RETRY;
    }
    if (qs < 0)
    {
      GNUNET_break (0);
      TMH_PG_rollback (pg);
      return TALER_EC_GENERIC_DB_FETCH_FAILED;
    }
    if (0 == qs)
    {
      TMH_PG_rollback (pg);
      return TALER_EC_MERCHANT_PRIVATE_POST_REWARD_AUTHORIZE_RESERVE_NOT_FOUND;
    }
  }
  {
    struct TALER_Amount remaining;

    if (0 >
        TALER_amount_subtract (&remaining,
                               &exchange_initial_balance,
                               &rewards_committed))
    {
      GNUNET_break (0);
      TMH_PG_rollback (pg);
      return TALER_EC_GENERIC_DB_INVARIANT_FAILURE;
    }
    if (0 >
        TALER_amount_cmp (&remaining,
                          amount))
    {
      TMH_PG_rollback (pg);
      return TALER_EC_MERCHANT_PRIVATE_POST_REWARD_AUTHORIZE_INSUFFICIENT_FUNDS;
    }
  }
  GNUNET_assert (0 <=
                 TALER_amount_add (&rewards_committed,
                                   &rewards_committed,
                                   amount));
  {
    struct GNUNET_PQ_QueryParam params[] = {
      GNUNET_PQ_query_param_string (instance_id),
      GNUNET_PQ_query_param_auto_from_type (reserve_pubp),
      TALER_PQ_query_param_amount_with_currency (pg->conn,
                                                 &rewards_committed),
      GNUNET_PQ_query_param_end
    };

    qs = GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                             "update_reserve_rewards_committed",
                                             params);
    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
    {
      TMH_PG_rollback (pg);
      goto RETRY;
    }
    if (qs < 0)
    {
      GNUNET_break (0);
      TMH_PG_rollback (pg);
      return TALER_EC_GENERIC_DB_STORE_FAILED;
    }
  }
  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_NONCE,
                              reward_id,
                              sizeof (*reward_id));
  {
    struct TALER_Amount zero;
    struct GNUNET_PQ_QueryParam params[] = {
      GNUNET_PQ_query_param_string (instance_id),
      GNUNET_PQ_query_param_auto_from_type (reserve_pubp),
      GNUNET_PQ_query_param_auto_from_type (reward_id),
      GNUNET_PQ_query_param_string (justification),
      GNUNET_PQ_query_param_string (next_url),
      GNUNET_PQ_query_param_timestamp (expiration),
      TALER_PQ_query_param_amount_with_currency (pg->conn,
                                                 amount),
      TALER_PQ_query_param_amount_with_currency (pg->conn,
                                                 &zero),
      GNUNET_PQ_query_param_end
    };

    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_set_zero (amount->currency,
                                          &zero));
    qs = GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                             "insert_reward",
                                             params);
    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
    {
      TMH_PG_rollback (pg);
      goto RETRY;
    }
    if (qs < 0)
    {
      GNUNET_break (0);
      TMH_PG_rollback (pg);
      return TALER_EC_GENERIC_DB_STORE_FAILED;
    }
  }
  qs = TMH_PG_commit (pg);
  if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
    goto RETRY;
  if (qs < 0)
  {
    GNUNET_break (0);
    TMH_PG_rollback (pg);
    return TALER_EC_GENERIC_DB_COMMIT_FAILED;
  }
  return TALER_EC_NONE;
}