/*
  This file is part of TALER
  (C) 2017-2023 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 taler-merchant-httpd_get-rewards-ID.c
 * @brief implementation of a GET /rewards/ID handler
 * @author Christian Grothoff
 */
#include "platform.h"
#include <microhttpd.h>
#include <jansson.h>
#include <taler/taler_dbevents.h>
#include <taler/taler_json_lib.h>
#include <taler/taler_signatures.h>
#include "taler-merchant-httpd.h"
#include "taler-merchant-httpd_mhd.h"
#include "taler-merchant-httpd_exchanges.h"


/**
 * Information we keep per /kyc request.
 */
struct RewardContext
{
  /**
   * Stored in a DLL.
   */
  struct RewardContext *next;

  /**
   * Stored in a DLL.
   */
  struct RewardContext *prev;

  /**
   * Connection we are handling.
   */
  struct MHD_Connection *connection;

  /**
   * Our handler context.
   */
  struct TMH_HandlerContext *hc;

  /**
   * Database event we are waiting on to be resuming.
   */
  struct GNUNET_DB_EventHandler *eh;

  /**
   * Response to return, NULL if we don't have one yet.
   */
  struct MHD_Response *response;

  /**
   * When does this request time out?
   */
  struct GNUNET_TIME_Absolute timeout;

  /**
   * ID of the reward being queried.
   */
  struct TALER_RewardIdentifierP reward_id;

  /**
   * Minimum reward amount picked up we should return to the
   * client.
   */
  struct TALER_Amount min_amount;

  /**
   * #GNUNET_NO if the @e connection was not suspended,
   * #GNUNET_YES if the @e connection was suspended,
   * #GNUNET_SYSERR if @e connection was resumed to as
   * part of #MH_force_pc_resume during shutdown.
   */
  enum GNUNET_GenericReturnValue suspended;

  /**
   * Is the "pickups" argument set to "yes"?
   */
  bool fpu;

  /**
   * True if @e min_amount was provided.
   */
  bool have_min_amount;
};


/**
 * Head of DLL.
 */
static struct RewardContext *tc_head;

/**
 * Tail of DLL.
 */
static struct RewardContext *tc_tail;


void
TMH_force_reward_resume ()
{
  for (struct RewardContext *tc = tc_head;
       NULL != tc;
       tc = tc->next)
  {
    if (GNUNET_YES == tc->suspended)
    {
      tc->suspended = GNUNET_SYSERR;
      MHD_resume_connection (tc->connection);
    }
  }
}


/**
 * Custom cleanup routine for a `struct RewardContext`.
 *
 * @param cls the `struct RewardContext` to clean up.
 */
static void
reward_context_cleanup (void *cls)
{
  struct RewardContext *tc = cls;

  if (NULL != tc->response)
  {
    MHD_destroy_response (tc->response);
    tc->response = NULL;
  }
  if (NULL != tc->eh)
  {
    TMH_db->event_listen_cancel (tc->eh);
    tc->eh = NULL;
  }
  GNUNET_CONTAINER_DLL_remove (tc_head,
                               tc_tail,
                               tc);
  GNUNET_free (tc);
}


/**
 * We have received a trigger from the database
 * that we should (possibly) resume the request.
 *
 * @param cls a `struct RewardContext` to resume
 * @param extra usually NULL
 * @param extra_size number of bytes in @a extra
 */
static void
resume_by_event (void *cls,
                 const void *extra,
                 size_t extra_size)
{
  struct RewardContext *tc = cls;

  (void) extra;
  (void) extra_size;
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Resuming request %p by trigger\n",
              tc);
  if (GNUNET_NO == tc->suspended)
    return; /* duplicate event is possible */
  tc->suspended = GNUNET_NO;
  GNUNET_CONTAINER_DLL_remove (tc_head,
                               tc_tail,
                               tc);
  MHD_resume_connection (tc->connection);
  TALER_MHD_daemon_trigger ();   /* we resumed, kick MHD */
}


MHD_RESULT
TMH_private_get_rewards_ID (const struct TMH_RequestHandler *rh,
                            struct MHD_Connection *connection,
                            struct TMH_HandlerContext *hc)
{
  struct RewardContext *tc = hc->ctx;
  struct TALER_Amount total_authorized;
  struct TALER_Amount total_picked_up;
  char *reason;
  struct GNUNET_TIME_Timestamp expiration;
  struct TALER_ReservePublicKeyP reserve_pub;
  unsigned int pickups_length = 0;
  struct TALER_MERCHANTDB_PickupDetails *pickups = NULL;
  enum GNUNET_DB_QueryStatus qs;
  json_t *pickups_json = NULL;

  (void) rh;
  if (NULL == tc)
  {
    tc = GNUNET_new (struct RewardContext);
    hc->ctx = tc;
    hc->cc = &reward_context_cleanup;
    GNUNET_CONTAINER_DLL_insert (tc_head,
                                 tc_tail,
                                 tc);
    tc->connection = connection;
    tc->hc = hc;
    GNUNET_assert (NULL != hc->infix);
    if (GNUNET_OK !=
        GNUNET_CRYPTO_hash_from_string (hc->infix,
                                        &tc->reward_id.hash))
    {
      /* reward_id has wrong encoding */
      GNUNET_break_op (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_BAD_REQUEST,
                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                         hc->infix);
    }
    {
      const char *pstr;

      pstr = MHD_lookup_connection_value (connection,
                                          MHD_GET_ARGUMENT_KIND,
                                          "pickups");
      tc->fpu = (NULL != pstr)
        ? 0 == strcasecmp (pstr, "yes")
        : false;
    }
    {
      const char *min_amount;

      min_amount = MHD_lookup_connection_value (connection,
                                                MHD_GET_ARGUMENT_KIND,
                                                "min_amount");
      if (NULL != min_amount)
      {
        if (GNUNET_OK !=
            TALER_string_to_amount (min_amount,
                                    &tc->min_amount))
        {
          GNUNET_break_op (0);
          return TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_BAD_REQUEST,
                                             TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                             "min_amount");
        }
        tc->have_min_amount = true;
      }
    }
    TALER_MHD_parse_request_timeout (connection,
                                     &tc->timeout);
    if (! GNUNET_TIME_absolute_is_future (tc->timeout))
    {
      struct TMH_RewardPickupEventP reward_eh = {
        .header.size = htons (sizeof (reward_eh)),
        .header.type = htons (TALER_DBEVENT_MERCHANT_REWARD_PICKUP),
        .reward_id = tc->reward_id
      };

      GNUNET_CRYPTO_hash (hc->instance->settings.id,
                          strlen (hc->instance->settings.id),
                          &reward_eh.h_instance);
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "Subscribing to payment triggers for %p\n",
                  tc);
      tc->eh = TMH_db->event_listen (
        TMH_db->cls,
        &reward_eh.header,
        GNUNET_TIME_absolute_get_remaining (tc->timeout),
        &resume_by_event,
        tc);
    }
  }

  GNUNET_assert (GNUNET_YES != tc->suspended);
  TMH_db->preflight (TMH_db->cls);
  qs = TMH_db->lookup_reward_details (TMH_db->cls,
                                      hc->instance->settings.id,
                                      &tc->reward_id,
                                      tc->fpu,
                                      &total_authorized,
                                      &total_picked_up,
                                      &reason,
                                      &expiration,
                                      &reserve_pub,
                                      &pickups_length,
                                      &pickups);
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
  {
    unsigned int response_code;
    enum TALER_ErrorCode ec;

    switch (qs)
    {
    case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
      ec = TALER_EC_MERCHANT_GENERIC_REWARD_ID_UNKNOWN;
      response_code = MHD_HTTP_NOT_FOUND;
      break;
    case GNUNET_DB_STATUS_SOFT_ERROR:
      ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
      response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
      break;
    case GNUNET_DB_STATUS_HARD_ERROR:
      ec = TALER_EC_GENERIC_DB_COMMIT_FAILED;
      response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
      break;
    default:
      GNUNET_break (0);
      ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
      response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
      break;
    }
    return TALER_MHD_reply_with_error (connection,
                                       response_code,
                                       ec,
                                       NULL);
  }
  /* do not allow timeout above reward expiration */
  tc->timeout = GNUNET_TIME_absolute_min (tc->timeout,
                                          expiration.abs_time);
  if ( (NULL != tc->eh) &&
       (GNUNET_TIME_absolute_is_future (tc->timeout)) &&
       (tc->have_min_amount) &&
       (GNUNET_YES ==
        TALER_amount_cmp_currency (&tc->min_amount,
                                   &total_picked_up)) &&
       (1 == TALER_amount_cmp (&tc->min_amount,
                               &total_picked_up)) )
  {
    MHD_suspend_connection (connection);
    tc->suspended = GNUNET_YES;
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Suspending REWARD request handling as pickup is below threshold requested by client\n");
    GNUNET_array_grow (pickups,
                       pickups_length,
                       0);
    GNUNET_free (reason);
    return MHD_YES;
  }
  if (tc->fpu)
  {
    pickups_json = json_array ();
    GNUNET_assert (NULL != pickups_json);
    for (unsigned int i = 0; i<pickups_length; i++)
    {
      GNUNET_assert (0 ==
                     json_array_append_new (
                       pickups_json,
                       GNUNET_JSON_PACK (
                         GNUNET_JSON_pack_data_auto ("pickup_id",
                                                     &pickups[i].pickup_id),
                         GNUNET_JSON_pack_uint64 ("num_planchets",
                                                  pickups[i].num_planchets),
                         TALER_JSON_pack_amount ("requested_amount",
                                                 &pickups[i].requested_amount))));
    }
  }
  GNUNET_array_grow (pickups,
                     pickups_length,
                     0);
  {
    MHD_RESULT ret;

    ret = TALER_MHD_REPLY_JSON_PACK (
      connection,
      MHD_HTTP_OK,
      TALER_JSON_pack_amount ("total_authorized",
                              &total_authorized),
      TALER_JSON_pack_amount ("total_picked_up",
                              &total_picked_up),
      GNUNET_JSON_pack_string ("reason",
                               reason),
      GNUNET_JSON_pack_timestamp ("expiration",
                                  expiration),
      GNUNET_JSON_pack_data_auto ("reserve_pub",
                                  &reserve_pub),
      GNUNET_JSON_pack_allow_null (
        GNUNET_JSON_pack_array_steal ("pickups",
                                      pickups_json)));
    GNUNET_free (reason);
    return ret;
  }
}