/*
  This file is part of TALER
  (C) 2019-2021 Taler Systems SA

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU Affero 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_private-get-orders.c
 * @brief implement GET /orders
 * @author Christian Grothoff
 */
#include "platform.h"
#include "taler-merchant-httpd_private-get-orders.h"
#include <taler/taler_json_lib.h>
#include <taler/taler_dbevents.h>


/**
 * Sensible bound on TALER_MERCHANTDB_OrderFilter.delta
 */
#define MAX_DELTA 1024


/**
 * A pending GET /orders request.
 */
struct TMH_PendingOrder
{

  /**
   * Kept in a DLL.
   */
  struct TMH_PendingOrder *prev;

  /**
   * Kept in a DLL.
   */
  struct TMH_PendingOrder *next;

  /**
   * Which connection was suspended.
   */
  struct MHD_Connection *con;

  /**
   * Associated heap node.
   */
  struct GNUNET_CONTAINER_HeapNode *hn;

  /**
   * Which instance is this client polling? This also defines
   * which DLL this struct is part of.
   */
  struct TMH_MerchantInstance *mi;

  /**
   * At what time does this request expire? If set in the future, we
   * may wait this long for a payment to arrive before responding.
   */
  struct GNUNET_TIME_Absolute long_poll_timeout;

  /**
   * Filter to apply.
   */
  struct TALER_MERCHANTDB_OrderFilter of;

  /**
   * The array of orders.
   */
  json_t *pa;

  /**
   * The name of the instance we are querying for.
   */
  const char *instance_id;

  /**
   * The result after adding the orders (#TALER_EC_NONE for okay, anything else for an error).
   */
  enum TALER_ErrorCode result;

  /**
   * Is the structure in the DLL
   */
  bool in_dll;
};


/**
 * Task to timeout pending orders.
 */
static struct GNUNET_SCHEDULER_Task *order_timeout_task;

/**
 * Heap for orders in long polling awaiting timeout.
 */
static struct GNUNET_CONTAINER_Heap *order_timeout_heap;


/**
 * We are shutting down (or an instance is being deleted), force resume of all
 * GET /orders requests.
 *
 * @param mi instance to force resuming for
 */
void
TMH_force_get_orders_resume (struct TMH_MerchantInstance *mi)
{
  struct TMH_PendingOrder *po;

  while (NULL != (po = mi->po_head))
  {
    GNUNET_assert (po->in_dll);
    GNUNET_CONTAINER_DLL_remove (mi->po_head,
                                 mi->po_tail,
                                 po);
    GNUNET_assert (po ==
                   GNUNET_CONTAINER_heap_remove_root (order_timeout_heap));
    MHD_resume_connection (po->con);
    po->in_dll = false;
  }
  if (NULL != mi->po_eh)
  {
    TMH_db->event_listen_cancel (mi->po_eh);
    mi->po_eh = NULL;
  }
  if (NULL != order_timeout_task)
  {
    GNUNET_SCHEDULER_cancel (order_timeout_task);
    order_timeout_task = NULL;
  }
  if (NULL != order_timeout_heap)
  {
    GNUNET_CONTAINER_heap_destroy (order_timeout_heap);
    order_timeout_heap = NULL;
  }
}


/**
 * Task run to trigger timeouts on GET /orders requests with long polling.
 *
 * @param cls unused
 */
static void
order_timeout (void *cls)
{
  struct TMH_PendingOrder *po;
  struct TMH_MerchantInstance *mi;

  (void) cls;
  order_timeout_task = NULL;
  while (1)
  {
    po = GNUNET_CONTAINER_heap_peek (order_timeout_heap);
    if (NULL == po)
    {
      /* release data structure, we don't need it right now */
      GNUNET_CONTAINER_heap_destroy (order_timeout_heap);
      order_timeout_heap = NULL;
      return;
    }
    if (GNUNET_TIME_absolute_is_future (po->long_poll_timeout))
      break;
    GNUNET_assert (po ==
                   GNUNET_CONTAINER_heap_remove_root (order_timeout_heap));
    po->hn = NULL;
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Resuming long polled job due to timeout\n");
    mi = po->mi;
    GNUNET_assert (po->in_dll);
    GNUNET_CONTAINER_DLL_remove (mi->po_head,
                                 mi->po_tail,
                                 po);
    if ( (NULL == mi->po_head) &&
         (NULL != mi->po_eh) )
    {
      TMH_db->event_listen_cancel (mi->po_eh);
      mi->po_eh = NULL;
    }
    po->in_dll = false;
    MHD_resume_connection (po->con);
    TALER_MHD_daemon_trigger ();   /* we resumed, kick MHD */
  }
  order_timeout_task = GNUNET_SCHEDULER_add_at (po->long_poll_timeout,
                                                &order_timeout,
                                                NULL);
}


/**
 * Cleanup our "context", where we stored the JSON array
 * we are building for the response.
 *
 * @param ctx context to clean up, must be a `struct AddOrderState *`
 */
static void
cleanup (void *ctx)
{
  struct TMH_PendingOrder *po = ctx;

  if (po->in_dll)
  {
    struct TMH_MerchantInstance *mi = po->mi;

    GNUNET_CONTAINER_DLL_remove (mi->po_head,
                                 mi->po_tail,
                                 po);
  }
  if (NULL != po->hn)
    GNUNET_assert (po ==
                   GNUNET_CONTAINER_heap_remove_node (po->hn));
  json_decref (po->pa);
  GNUNET_free (po);
}


/**
 * Function called with information about a refund.
 * It is responsible for summing up the refund amount.
 *
 * @param cls closure
 * @param refund_serial unique serial number of the refund
 * @param timestamp time of the refund (for grouping of refunds in the wallet UI)
 * @param coin_pub public coin from which the refund comes from
 * @param exchange_url URL of the exchange that issued @a coin_pub
 * @param rtransaction_id identificator of the refund
 * @param reason human-readable explanation of the refund
 * @param refund_amount refund amount which is being taken from @a coin_pub
 * @param pending true if the this refund was not yet processed by the wallet/exchange
 */
static void
process_refunds_cb (void *cls,
                    uint64_t refund_serial,
                    struct GNUNET_TIME_Timestamp timestamp,
                    const struct TALER_CoinSpendPublicKeyP *coin_pub,
                    const char *exchange_url,
                    uint64_t rtransaction_id,
                    const char *reason,
                    const struct TALER_Amount *refund_amount,
                    bool pending)
{
  struct TALER_Amount *total_refund_amount = cls;

  GNUNET_assert (0 <=
                 TALER_amount_add (total_refund_amount,
                                   total_refund_amount,
                                   refund_amount));
}


/**
 * Add order details to our JSON array.
 *
 * @param cls some closure
 * @param orig_order_id the order this is about
 * @param order_serial serial ID of the order
 * @param creation_time when was the order created
 */
static void
add_order (void *cls,
           const char *orig_order_id,
           uint64_t order_serial,
           struct GNUNET_TIME_Timestamp creation_time)
{
  struct TMH_PendingOrder *po = cls;
  json_t *contract_terms = NULL;
  struct TALER_PrivateContractHashP h_contract_terms;
  enum GNUNET_DB_QueryStatus qs;
  const char *summary;
  char *order_id = NULL;
  bool refundable = false;
  bool paid;
  struct TALER_Amount order_amount;

  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Adding order `%s' (%llu) to result set\n",
              orig_order_id,
              (unsigned long long) order_serial);
  qs = TMH_db->lookup_order_status_by_serial (TMH_db->cls,
                                              po->instance_id,
                                              order_serial,
                                              &order_id,
                                              &h_contract_terms,
                                              &paid);
  if (qs < 0)
  {
    GNUNET_break (0);
    po->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
    return;
  }
  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
  {
    /* Contract terms don't exist, so the order cannot be paid. */
    paid = false;
    if (NULL == orig_order_id)
    {
      /* cannot be via DB trigger, and the other code
         path should have passed an orig_order_id */
      GNUNET_break (0);
      po->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
      return;
    }
    order_id = GNUNET_strdup (orig_order_id);
  }

  {
    /* First try to find the order in the contracts */
    uint64_t os;
    bool paid = false;

    qs = TMH_db->lookup_contract_terms (TMH_db->cls,
                                        po->instance_id,
                                        order_id,
                                        &contract_terms,
                                        &os,
                                        &paid,
                                        NULL);
    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
      GNUNET_break (os == order_serial);
  }
  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
  {
    /* Might still be unclaimed, so try order table */
    struct TALER_MerchantPostDataHashP unused;

    qs = TMH_db->lookup_order (TMH_db->cls,
                               po->instance_id,
                               order_id,
                               NULL,
                               &unused,
                               &contract_terms);
  }
  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Order %llu disappeared during iteration. Skipping.\n",
                (unsigned long long) order_serial);
    json_decref (contract_terms); /* should still be NULL */
    GNUNET_free (order_id);
    return;
  }
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
  {
    GNUNET_break (0);
    po->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
    json_decref (contract_terms);
    GNUNET_free (order_id);
    return;
  }

  {
    struct GNUNET_TIME_Timestamp rd;
    struct GNUNET_JSON_Specification spec[] = {
      TALER_JSON_spec_amount ("amount",
                              TMH_currency,
                              &order_amount),
      GNUNET_JSON_spec_timestamp ("refund_deadline",
                                  &rd),
      GNUNET_JSON_spec_string ("summary",
                               &summary),
      GNUNET_JSON_spec_end ()
    };

    if (GNUNET_OK !=
        GNUNET_JSON_parse (contract_terms,
                           spec,
                           NULL, NULL))
    {
      GNUNET_break (0);
      po->result = TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID;
      json_decref (contract_terms);
      GNUNET_free (order_id);
      return;
    }

    if (GNUNET_TIME_absolute_is_future (rd.abs_time) &&
        paid)
    {
      struct TALER_Amount refund_amount;

      GNUNET_assert (GNUNET_OK ==
                     TALER_amount_set_zero (TMH_currency,
                                            &refund_amount));
      qs = TMH_db->lookup_refunds_detailed (TMH_db->cls,
                                            po->instance_id,
                                            &h_contract_terms,
                                            &process_refunds_cb,
                                            &refund_amount);
      if (0 > qs)
      {
        GNUNET_break (0);
        po->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
        json_decref (contract_terms);
        GNUNET_free (order_id);
        return;
      }
      if (0 > TALER_amount_cmp (&refund_amount,
                                &order_amount))
        refundable = true;
    }
  }

  GNUNET_assert (0 ==
                 json_array_append_new (
                   po->pa,
                   GNUNET_JSON_PACK (
                     GNUNET_JSON_pack_string ("order_id",
                                              order_id),
                     GNUNET_JSON_pack_uint64 ("row_id",
                                              order_serial),
                     GNUNET_JSON_pack_timestamp ("timestamp",
                                                 creation_time),
                     TALER_JSON_pack_amount ("amount",
                                             &order_amount),
                     GNUNET_JSON_pack_string ("summary",
                                              summary),
                     GNUNET_JSON_pack_bool ("refundable",
                                            refundable),
                     GNUNET_JSON_pack_bool ("paid",
                                            paid))));
  json_decref (contract_terms);
  GNUNET_free (order_id);
}


/**
 * We have received a trigger from the database
 * that we should (possibly) resume some requests.
 *
 * @param cls a `struct TMH_MerchantInstance`
 * @param extra a `struct TMH_OrderChangeEventP`
 * @param extra_size number of bytes in @a extra
 */
static void
resume_by_event (void *cls,
                 const void *extra,
                 size_t extra_size)
{
  struct TMH_MerchantInstance *mi = cls;
  const struct TMH_OrderChangeEventDetailsP *oce = extra;
  struct TMH_PendingOrder *pn;
  enum TMH_OrderStateFlags osf;
  uint64_t order_serial_id;
  struct GNUNET_TIME_Timestamp date;

  if (sizeof (*oce) != extra_size)
  {
    GNUNET_break (0);
    return;
  }
  osf = (enum TMH_OrderStateFlags) ntohl (oce->order_state);
  order_serial_id = GNUNET_ntohll (oce->order_serial_id);
  date = GNUNET_TIME_timestamp_ntoh (oce->execution_date);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Received notification about new order %llu\n",
              (unsigned long long) order_serial_id);
  for (struct TMH_PendingOrder *po = mi->po_head;
       NULL != po;
       po = pn)
  {
    pn = po->next;
    if (! ( ( ((TALER_EXCHANGE_YNA_YES == po->of.paid) ==
               (0 != (osf & TMH_OSF_PAID))) ||
              (TALER_EXCHANGE_YNA_ALL == po->of.paid) ) &&
            ( ((TALER_EXCHANGE_YNA_YES == po->of.refunded) ==
               (0 != (osf & TMH_OSF_REFUNDED))) ||
              (TALER_EXCHANGE_YNA_ALL == po->of.refunded) ) &&
            ( ((TALER_EXCHANGE_YNA_YES == po->of.wired) ==
               (0 != (osf & TMH_OSF_WIRED))) ||
              (TALER_EXCHANGE_YNA_ALL == po->of.wired) ) ) )
    {
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "Client %p waits on different order type\n",
                  po);
      continue;
    }
    if (po->of.delta > 0)
    {
      if (order_serial_id < po->of.start_row)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Client %p waits on different order row\n",
                    po);
        continue;
      }
      if (GNUNET_TIME_timestamp_cmp (date,
                                     <,
                                     po->of.date))
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Client %p waits on different order date\n",
                    po);
        continue;
      }
      po->of.delta--;
    }
    else
    {
      if (order_serial_id > po->of.start_row)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Client %p waits on different order row\n",
                    po);
        continue;
      }
      if (GNUNET_TIME_timestamp_cmp (date,
                                     >,
                                     po->of.date))
      {
        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                    "Client %p waits on different order date\n",
                    po);
        continue;
      }
      po->of.delta++;
    }
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Waking up client %p!\n",
                po);
    add_order (po,
               NULL,
               order_serial_id,
               date);
    GNUNET_assert (po->in_dll);
    GNUNET_CONTAINER_DLL_remove (mi->po_head,
                                 mi->po_tail,
                                 po);
    po->in_dll = false;
    GNUNET_assert (po ==
                   GNUNET_CONTAINER_heap_remove_node (po->hn));
    po->hn = NULL;
    MHD_resume_connection (po->con);
    TALER_MHD_daemon_trigger ();   /* we resumed, kick MHD */
  }
  if (NULL == mi->po_head)
  {
    TMH_db->event_listen_cancel (mi->po_eh);
    mi->po_eh = NULL;
  }
}


/**
 * There has been a change or addition of a new @a order_id.  Wake up
 * long-polling clients that may have been waiting for this event.
 *
 * @param mi the instance where the order changed
 * @param osf order state flags
 * @param date execution date of the order
 * @param order_serial_id serial ID of the order in the database
 */
void
TMH_notify_order_change (struct TMH_MerchantInstance *mi,
                         enum TMH_OrderStateFlags osf,
                         struct GNUNET_TIME_Timestamp date,
                         uint64_t order_serial_id)
{
  struct TMH_OrderChangeEventDetailsP oce = {
    .order_serial_id = GNUNET_htonll (order_serial_id),
    .execution_date = GNUNET_TIME_timestamp_hton (date),
    .order_state = htonl (osf)
  };
  struct TMH_OrderChangeEventP eh = {
    .header.type = htons (TALER_DBEVENT_MERCHANT_ORDERS_CHANGE),
    .header.size = htons (sizeof (eh)),
    .merchant_pub = mi->merchant_pub
  };

  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Notifying clients of new order %llu at %s\n",
              (unsigned long long) order_serial_id,
              TALER_B2S (&mi->merchant_pub));
  TMH_db->event_notify (TMH_db->cls,
                        &eh.header,
                        &oce,
                        sizeof (oce));
}


/**
 * Handle a GET "/orders" request.
 *
 * @param rh context of the handler
 * @param connection the MHD connection to handle
 * @param[in,out] hc context with further information about the request
 * @return MHD result code
 */
MHD_RESULT
TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                        struct MHD_Connection *connection,
                        struct TMH_HandlerContext *hc)
{
  struct TMH_PendingOrder *po = hc->ctx;
  enum GNUNET_DB_QueryStatus qs;
  struct TALER_MERCHANTDB_OrderFilter of;

  if (NULL != po)
  {
    /* resumed from long-polling, return answer we already have
       in 'hc->ctx' */
    if (TALER_EC_NONE != po->result)
    {
      GNUNET_break (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         po->result,
                                         NULL);
    }
    return TALER_MHD_REPLY_JSON_PACK (
      connection,
      MHD_HTTP_OK,
      GNUNET_JSON_pack_array_incref ("orders",
                                     po->pa));
  }

  if (! (TALER_arg_to_yna (connection,
                           "paid",
                           TALER_EXCHANGE_YNA_ALL,
                           &of.paid)) )
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                       "paid");
  if (! (TALER_arg_to_yna (connection,
                           "refunded",
                           TALER_EXCHANGE_YNA_ALL,
                           &of.refunded)) )
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                       "refunded");
  if (! (TALER_arg_to_yna (connection,
                           "wired",
                           TALER_EXCHANGE_YNA_ALL,
                           &of.wired)) )
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                       "wired");
  {
    const char *delta_str;

    delta_str = MHD_lookup_connection_value (connection,
                                             MHD_GET_ARGUMENT_KIND,
                                             "delta");
    if (NULL == delta_str)
    {
      of.delta = -20;
    }
    else
    {
      char dummy;
      long long ll;

      if (1 !=
          sscanf (delta_str,
                  "%lld%c",
                  &ll,
                  &dummy))
      {
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "delta");
      }
      of.delta = (int64_t) ll;
      if ( (-MAX_DELTA > of.delta) ||
           (of.delta > MAX_DELTA) )
      {
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "delta");
      }
    }
  }
  {
    const char *date_s_str;

    date_s_str = MHD_lookup_connection_value (connection,
                                               MHD_GET_ARGUMENT_KIND,
                                               "date_s");
    if (NULL == date_s_str)
    {
      if (of.delta > 0)
        of.date = GNUNET_TIME_UNIT_ZERO_TS;
      else
        of.date = GNUNET_TIME_UNIT_FOREVER_TS;
    }
    else
    {
      char dummy;
      unsigned long long ll;

      if (1 !=
          sscanf (date_s_str,
                  "%llu%c",
                  &ll,
                  &dummy))
      {
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "date_ms");
      }

      of.date = GNUNET_TIME_absolute_to_timestamp (
        GNUNET_TIME_absolute_from_s (ll));
      if (GNUNET_TIME_absolute_is_never (of.date.abs_time))
      {
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "date_s");
      }
    }
  }
  {
    const char *start_row_str;

    start_row_str = MHD_lookup_connection_value (connection,
                                                 MHD_GET_ARGUMENT_KIND,
                                                 "start");
    if (NULL == start_row_str)
    {
      if (of.delta > 0)
        of.start_row = 0;
      else
        of.start_row = INT64_MAX;
    }
    else
    {
      char dummy;
      unsigned long long ull;

      if (1 !=
          sscanf (start_row_str,
                  "%llu%c",
                  &ull,
                  &dummy))
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "start");
      of.start_row = (uint64_t) ull;
      if (INT64_MAX < of.start_row)
      {
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "start");
      }
    }
  }
  {
    const char *timeout_ms_str;

    timeout_ms_str = MHD_lookup_connection_value (connection,
                                                  MHD_GET_ARGUMENT_KIND,
                                                  "timeout_ms");
    if (NULL == timeout_ms_str)
    {
      of.timeout = GNUNET_TIME_UNIT_ZERO;
    }
    else
    {
      char dummy;
      unsigned long long ull;

      if (1 !=
          sscanf (timeout_ms_str,
                  "%lld%c",
                  &ull,
                  &dummy))
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "timeout_ms");
      of.timeout = GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS,
                                                  ull);
      if (GNUNET_TIME_relative_is_forever (of.timeout))
      {
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                           "timeout_ms");
      }
    }

    if ( (0 >= of.delta) &&
         (! GNUNET_TIME_relative_is_zero (of.timeout)) )
    {
      GNUNET_break_op (0);
      of.timeout = GNUNET_TIME_UNIT_ZERO;
    }
  }

  po = GNUNET_new (struct TMH_PendingOrder);
  hc->ctx = po;
  hc->cc = &cleanup;
  po->con = connection;
  po->pa = json_array ();
  GNUNET_assert (NULL != po->pa);
  po->instance_id = hc->instance->settings.id;
  po->mi = hc->instance;
  qs = TMH_db->lookup_orders (TMH_db->cls,
                              po->instance_id,
                              &of,
                              &add_order,
                              po);
  if (0 > qs)
  {
    GNUNET_break (0);
    po->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
  }
  if (TALER_EC_NONE != po->result)
  {
    GNUNET_break (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       po->result,
                                       NULL);
  }
  if ( (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs) &&
       (! GNUNET_TIME_relative_is_zero (of.timeout)) )
  {
    struct TMH_MerchantInstance *mi = hc->instance;

    /* setup timeout heap (if not yet exists) */
    if (NULL == order_timeout_heap)
      order_timeout_heap
        = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
    po->hn = GNUNET_CONTAINER_heap_insert (order_timeout_heap,
                                           po,
                                           po->long_poll_timeout.abs_value_us);
    po->long_poll_timeout = GNUNET_TIME_relative_to_absolute (of.timeout);
    po->of = of;
    GNUNET_CONTAINER_DLL_insert (mi->po_head,
                                 mi->po_tail,
                                 po);
    po->in_dll = true;
    if (NULL == mi->po_eh)
    {
      struct TMH_OrderChangeEventP change_eh = {
        .header.type = htons (TALER_DBEVENT_MERCHANT_ORDERS_CHANGE),
        .header.size = htons (sizeof (change_eh)),
        .merchant_pub = mi->merchant_pub
      };

      mi->po_eh = TMH_db->event_listen (TMH_db->cls,
                                        &change_eh.header,
                                        GNUNET_TIME_UNIT_FOREVER_REL,
                                        &resume_by_event,
                                        mi);
    }
    MHD_suspend_connection (connection);
    {
      struct TMH_PendingOrder *pot;

      /* start timeout task */
      pot = GNUNET_CONTAINER_heap_peek (order_timeout_heap);
      if (NULL != order_timeout_task)
        GNUNET_SCHEDULER_cancel (order_timeout_task);
      order_timeout_task = GNUNET_SCHEDULER_add_at (pot->long_poll_timeout,
                                                    &order_timeout,
                                                    NULL);
    }
    return MHD_YES;
  }
  return TALER_MHD_REPLY_JSON_PACK (
    connection,
    MHD_HTTP_OK,
    GNUNET_JSON_pack_array_incref ("orders",
                                   po->pa));
}


/* end of taler-merchant-httpd_private-get-orders.c */