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path: root/src/backend/taler-merchant-httpd_private-get-orders-ID.c
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/*
  This file is part of TALER
  (C) 2017, 2019, 2020 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 backend/taler-merchant-httpd_private-get-orders-ID.c
 * @brief implementation of GET /private/orders/ID handler
 * @author Florian Dold
 * @author Christian Grothoff
 */
#include "platform.h"
#include "taler-merchant-httpd_private-get-orders-ID.h"
#include "taler-merchant-httpd_get-orders-ID.h"
#include <taler/taler_json_lib.h>
#include "taler-merchant-httpd_mhd.h"
#include "taler-merchant-httpd_exchanges.h"
#include "taler-merchant-httpd_private-get-orders.h"


/**
 * How long do we wait on the exchange?
 */
#define EXCHANGE_TIMEOUT GNUNET_TIME_relative_multiply ( \
    GNUNET_TIME_UNIT_SECONDS, 30)


/**
 * Data structure we keep for a check payment request.
 */
struct GetOrderRequestContext;


/**
 * Request to an exchange for details about wire transfers
 * in response to a coin's deposit operation.
 */
struct TransferQuery
{

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

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

  /**
   * Handle to query exchange about deposit status.
   */
  struct TALER_EXCHANGE_DepositGetHandle *dgh;

  /**
   * Handle for ongoing exchange operation.
   */
  struct TMH_EXCHANGES_FindOperation *fo;

  /**
   * Overall request this TQ belongs with.
   */
  struct GetOrderRequestContext *gorc;

  /**
   * Hash of the merchant's bank account the transfer (presumably) went to.
   */
  struct GNUNET_HashCode h_wire;

  /**
   * Value deposited (including deposit fee).
   */
  struct TALER_Amount amount_with_fee;

  /**
   * Deposit fee paid for this coin.
   */
  struct TALER_Amount deposit_fee;

  /**
   * Public key of the coin this is about.
   */
  struct TALER_CoinSpendPublicKeyP coin_pub;

  /**
   * Which deposit operation is this about?
   */
  uint64_t deposit_serial;

};


/**
 * Data structure we keep for a check payment request.
 */
struct GetOrderRequestContext
{

  /**
   * Entry in the #resume_timeout_heap for this check payment, if we are
   * suspended.
   */
  struct TMH_SuspendedConnection sc;

  /**
   * Which merchant instance is this for?
   */
  struct TMH_HandlerContext *hc;

  /**
   * session of the client
   */
  const char *session_id;

  /**
   * Fulfillment URL extracted from the contract. For repurchase detection.
   * Only valid as long as @e contract_terms is valid!  NULL if there is
   * no fulfillment URL in the contract.
   */
  const char *fulfillment_url;

  /**
   * Kept in a DLL while suspended on exchange.
   */
  struct GetOrderRequestContext *next;

  /**
   * Kept in a DLL while suspended on exchange.
   */
  struct GetOrderRequestContext *prev;

  /**
   * Handle to the exchange, only valid while the @e fo succeeds.
   */
  struct TALER_EXCHANGE_Handle *eh;

  /**
   * Head of DLL of individual queries for transfer data.
   */
  struct TransferQuery *tq_head;

  /**
   * Tail of DLL of individual queries for transfer data.
   */
  struct TransferQuery *tq_tail;

  /**
   * Timeout task while waiting on exchange.
   */
  struct GNUNET_SCHEDULER_Task *tt;

  /**
   * Contract terms of the payment we are checking. NULL when they
   * are not (yet) known.
   */
  json_t *contract_terms;

  /**
   * Wire details for the payment, to be returned in the reply. NULL
   * if not available.
   */
  json_t *wire_details;

  /**
   * Problems we encountered when looking up Wire details
   * for the payment, to be returned.  NULL if not available.
   */
  json_t *wire_reports;

  /**
   * Details about refunds, NULL if there are no refunds.
   */
  json_t *refund_details;

  /**
   * Hash over the @e contract_terms.
   */
  struct GNUNET_HashCode h_contract_terms;

  /**
   * Total amount the exchange deposited into our bank account
   * (confirmed or unconfirmed), excluding fees.
   */
  struct TALER_Amount deposits_total;

  /**
   * Total amount in deposit fees we paid for all coins.
   */
  struct TALER_Amount deposit_fees_total;

  /**
   * Total value of the coins that the exchange deposited into our bank
   * account (confirmed or unconfirmed), including deposit fees.
   */
  struct TALER_Amount value_total;

  /**
   * Total we were to be paid under the contract, excluding refunds.
   */
  struct TALER_Amount contract_amount;

  /**
   * Serial ID of the order.
   */
  uint64_t order_serial;

  /**
   * Total refunds granted for this payment. Only initialized
   * if @e refunded is set to true.
   */
  struct TALER_Amount refund_amount;

  /**
   * Exchange HTTP error code encountered while trying to determine wire transfer
   * details. #TALER_EC_NONE for no error encountered.
   */
  unsigned int exchange_hc;

  /**
   * Exchange error code encountered while trying to determine wire transfer
   * details. #TALER_EC_NONE for no error encountered.
   */
  enum TALER_ErrorCode exchange_ec;

  /**
   * Error code encountered while trying to determine wire transfer
   * details. #TALER_EC_NONE for no error encountered.
   */
  enum TALER_ErrorCode wire_ec;

  /**
   * HTTP status to return with @e wire_ec, 0 if @e wire_ec is #TALER_EC_NONE.
   */
  unsigned int wire_hc;

  /**
   * Set to true if this payment has been refunded and
   * @e refund_amount is initialized.
   */
  bool refunded;

  /**
   * Did the client request us to fetch the wire transfer status?
   * If false, we may still return it if it is available.
   */
  bool transfer_status_requested;

};


/**
 * Head of list of suspended requests waiting on the exchange.
 */
static struct GetOrderRequestContext *gorc_head;

/**
 * Tail of list of suspended requests waiting on the exchange.
 */
static struct GetOrderRequestContext *gorc_tail;


/**
 * Resume processing the request, cancelling all pending asynchronous
 * operations.
 *
 * @param gorc request to resume
 * @param http_status HTTP status to return, 0 to continue with success
 * @param ec error code for the request, #TALER_EC_NONE on success
 */
static void
gorc_resume (struct GetOrderRequestContext *gorc,
             unsigned int http_status,
             enum TALER_ErrorCode ec)
{
  struct TransferQuery *tq;

  if (NULL != gorc->tt)
  {
    GNUNET_SCHEDULER_cancel (gorc->tt);
    gorc->tt = NULL;
  }
  while (NULL != (tq = gorc->tq_head))
  {
    if (NULL != tq->fo)
    {
      TMH_EXCHANGES_find_exchange_cancel (tq->fo);
      tq->fo = NULL;
    }
    if (NULL != tq->dgh)
    {
      TALER_EXCHANGE_deposits_get_cancel (tq->dgh);
      tq->dgh = NULL;
    }
  }
  gorc->wire_hc = http_status;
  gorc->wire_ec = ec;
  GNUNET_CONTAINER_DLL_remove (gorc_head,
                               gorc_tail,
                               gorc);
  MHD_resume_connection (gorc->sc.con);
  TMH_trigger_daemon ();   /* we resumed, kick MHD */
}


/**
 * Add a report about trouble obtaining wire transfer data to the reply.
 *
 * @param gorc request to add wire report to
 * @param ec error code to add
 * @param coin_pub public key of the affected coin
 * @param exchange_hr details from exchange, NULL if exchange is blameless
 */
static void
gorc_report (struct GetOrderRequestContext *gorc,
             enum TALER_ErrorCode ec,
             struct TALER_CoinSpendPublicKeyP *coin_pub,
             const struct TALER_EXCHANGE_HttpResponse *exchange_hr)
{
  if (NULL != exchange_hr)
    GNUNET_assert (0 ==
                   json_array_append_new (
                     gorc->wire_reports,
                     json_pack ("{s:I, s:s, s:I, s:I, s:o }",
                                "code",
                                (json_int_t) ec,
                                "hint",
                                TALER_ErrorCode_get_hint (ec),
                                "exchange_ec",
                                (json_int_t) exchange_hr->ec,
                                "exchange_hc",
                                (json_int_t) exchange_hr->http_status,
                                "coin_pub",
                                GNUNET_JSON_from_data_auto (coin_pub))));
  else
    GNUNET_assert (0 ==
                   json_array_append_new (
                     gorc->wire_reports,
                     json_pack ("{s:I, s:s, s:o }",
                                "code",
                                (json_int_t) ec,
                                "hint",
                                TALER_ErrorCode_get_hint (ec),
                                "coin_pub",
                                GNUNET_JSON_from_data_auto (coin_pub))));
}


/**
 * Timeout trying to get current wire transfer data from the exchange.
 * Clean up and continue.
 *
 * @param cls closure, must be a `struct GetOrderRequestContext *`
 */
static void
exchange_timeout_cb (void *cls)
{
  struct GetOrderRequestContext *gorc = cls;

  gorc->tt = NULL;
  gorc_resume (gorc,
               MHD_HTTP_REQUEST_TIMEOUT,
               TALER_EC_GET_ORDERS_EXCHANGE_TIMEOUT);
}


/**
 * Function called with detailed wire transfer data.
 *
 * @param cls closure with a `struct TransferQuery *`
 * @param hr HTTP response data
 * @param dd details about the deposit (NULL on errors)
 */
static void
deposit_get_cb (void *cls,
                const struct TALER_EXCHANGE_HttpResponse *hr,
                const struct TALER_EXCHANGE_DepositData *dd)
{
  struct TransferQuery *tq = cls;
  struct GetOrderRequestContext *gorc = tq->gorc;

  GNUNET_CONTAINER_DLL_remove (gorc->tq_head,
                               gorc->tq_tail,
                               tq);
  if (NULL == dd)
  {
    gorc_report (gorc,
                 TALER_EC_GET_ORDERS_EXCHANGE_TRACKING_FAILURE,
                 &tq->coin_pub,
                 hr);
    GNUNET_free (tq);
    if (NULL == gorc->tq_head)
      gorc_resume (gorc,
                   0,
                   TALER_EC_NONE);
    return;
  }
  else if (MHD_HTTP_OK == hr->http_status)
  {
    enum GNUNET_DB_QueryStatus qs;

    qs = TMH_db->insert_deposit_to_transfer (TMH_db->cls,
                                             tq->deposit_serial,
                                             dd);
    if (qs < 0)
    {
      gorc_report (gorc,
                   TALER_EC_GET_ORDERS_DB_STORE_TRACKING_FAILURE,
                   &tq->coin_pub,
                   NULL);
      GNUNET_free (tq);
      if (NULL == gorc->tq_head)
        gorc_resume (gorc,
                     0,
                     TALER_EC_NONE);
      return;
    }
    /* Compute total amount *wired* */
    if (0 >
        TALER_amount_add (&gorc->deposits_total,
                          &gorc->deposits_total,
                          &dd->coin_contribution))
    {
      gorc_report (gorc,
                   TALER_EC_GET_ORDERS_AMOUNT_ARITHMETIC_FAILURE,
                   &tq->coin_pub,
                   NULL);
      GNUNET_free (tq);
      if (NULL == gorc->tq_head)
        gorc_resume (gorc,
                     0,
                     TALER_EC_NONE);
      return;
    }
    if (0 >
        TALER_amount_add (&gorc->deposit_fees_total,
                          &gorc->deposit_fees_total,
                          &tq->deposit_fee))
    {
      gorc_report (gorc,
                   TALER_EC_GET_ORDERS_AMOUNT_ARITHMETIC_FAILURE,
                   &tq->coin_pub,
                   NULL);
      GNUNET_free (tq);
      if (NULL == gorc->tq_head)
        gorc_resume (gorc,
                     0,
                     TALER_EC_NONE);
      return;
    }
  }
  else
  {
    /* got a 'preliminary' reply from the exchange, simply skip */
    gorc_report (gorc,
                 TALER_EC_NONE,
                 &tq->coin_pub,
                 hr);
  }
  GNUNET_free (tq);
  if (NULL != gorc->tq_head)
    return;
  /* *all* are done, resume! */
  gorc_resume (gorc,
               0,
               TALER_EC_NONE);
}


/**
 * Function called with the result of a #TMH_EXCHANGES_find_exchange()
 * operation.
 *
 * @param cls closure with a `struct GetOrderRequestContext *`
 * @param hr HTTP response details
 * @param eh handle to the exchange context
 * @param payto_uri payto://-URI of the exchange
 * @param wire_fee current applicable wire fee for dealing with @a eh, NULL if not available
 * @param exchange_trusted true if this exchange is trusted by config
 */
static void
exchange_found_cb (void *cls,
                   const struct TALER_EXCHANGE_HttpResponse *hr,
                   struct TALER_EXCHANGE_Handle *eh,
                   const char *payto_uri,
                   const struct TALER_Amount *wire_fee,
                   bool exchange_trusted)
{
  struct TransferQuery *tq = cls;
  struct GetOrderRequestContext *gorc = tq->gorc;

  tq->fo = NULL;
  if (NULL == eh)
  {
    /* failed */
    GNUNET_CONTAINER_DLL_remove (gorc->tq_head,
                                 gorc->tq_tail,
                                 tq);
    GNUNET_free (tq);
    gorc->exchange_hc = hr->http_status;
    gorc->exchange_ec = hr->ec;
    gorc_resume (gorc,
                 MHD_HTTP_FAILED_DEPENDENCY,
                 TALER_EC_GET_ORDERS_EXCHANGE_LOOKUP_FAILURE);
    return;
  }
  tq->dgh = TALER_EXCHANGE_deposits_get (eh,
                                         &gorc->hc->instance->merchant_priv,
                                         &tq->h_wire,
                                         &gorc->h_contract_terms,
                                         &tq->coin_pub,
                                         &deposit_get_cb,
                                         tq);
  if (NULL == tq->dgh)
  {
    GNUNET_CONTAINER_DLL_remove (gorc->tq_head,
                                 gorc->tq_tail,
                                 tq);
    GNUNET_free (tq);
    gorc_resume (gorc,
                 MHD_HTTP_INTERNAL_SERVER_ERROR,
                 TALER_EC_GET_ORDERS_EXCHANGE_REQUEST_FAILURE);
  }
}


/**
 * Function called with each @a coin_pub that was deposited into the
 * @a h_wire account of the merchant for the @a deposit_serial as part
 * of the payment for the order identified by @a cls.
 *
 * Queries the exchange for the payment status associated with the
 * given coin.
 *
 * @param cls a `struct GetOrderRequestContext`
 * @param deposit_serial identifies the deposit operation
 * @param exchange_url URL of the exchange that issued @a coin_pub
 * @param amount_with_fee amount the exchange will deposit for this coin
 * @param deposit_fee fee the exchange will charge for this coin
 * @param h_wire hash of the merchant's wire account into which the deposit was made
 * @param coin_pub public key of the deposited coin
 */
static void
deposit_cb (void *cls,
            uint64_t deposit_serial,
            const char *exchange_url,
            const struct GNUNET_HashCode *h_wire,
            const struct TALER_Amount *amount_with_fee,
            const struct TALER_Amount *deposit_fee,
            const struct TALER_CoinSpendPublicKeyP *coin_pub)
{
  struct GetOrderRequestContext *gorc = cls;
  struct TransferQuery *tq;

  tq = GNUNET_new (struct TransferQuery);
  tq->gorc = gorc;
  tq->deposit_serial = deposit_serial;
  GNUNET_CONTAINER_DLL_insert (gorc->tq_head,
                               gorc->tq_tail,
                               tq);
  tq->coin_pub = *coin_pub;
  tq->h_wire = *h_wire;
  tq->amount_with_fee = *amount_with_fee;
  tq->deposit_fee = *deposit_fee;
  tq->fo = TMH_EXCHANGES_find_exchange (exchange_url,
                                        NULL,
                                        GNUNET_NO,
                                        &exchange_found_cb,
                                        tq);
  if (NULL == tq->fo)
  {
    gorc_resume (gorc,
                 MHD_HTTP_INTERNAL_SERVER_ERROR,
                 TALER_EC_GET_ORDERS_EXCHANGE_LOOKUP_START_FAILURE);
  }
}


/**
 * Clean up the session state for a GET /private/order/ID request.
 *
 * @param cls closure, must be a `struct GetOrderRequestContext *`
 */
static void
gorc_cleanup (void *cls)
{
  struct GetOrderRequestContext *gorc = cls;

  if (NULL != gorc->contract_terms)
    json_decref (gorc->contract_terms);
  if (NULL != gorc->wire_details)
    json_decref (gorc->wire_details);
  if (NULL != gorc->refund_details)
    json_decref (gorc->refund_details);
  if (NULL != gorc->wire_reports)
    json_decref (gorc->wire_reports);
  GNUNET_assert (NULL == gorc->tt);
  GNUNET_free (gorc);
}


/**
 * 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 timestamp when was the refund made
 * @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_Absolute 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 GetOrderRequestContext *gorc = cls;

  GNUNET_assert (0 ==
                 json_array_append_new (
                   gorc->refund_details,
                   json_pack ("{s:o, s:o, s:s}",
                              "amount",
                              TALER_JSON_from_amount (refund_amount),
                              "timestamp",
                              GNUNET_JSON_from_time_abs (timestamp),
                              "reason",
                              reason)));
  /* For refunded coins, we are not charged deposit fees, so subtract those
     again */
  for (struct TransferQuery *tq = gorc->tq_head;
       NULL != tq;
       tq = tq->next)
  {
    if (0 ==
        GNUNET_memcmp (&tq->coin_pub,
                       coin_pub))
    {
      GNUNET_assert (0 <=
                     TALER_amount_subtract (&gorc->deposit_fees_total,
                                            &gorc->deposit_fees_total,
                                            &tq->deposit_fee));
    }
  }
  GNUNET_assert (0 <=
                 TALER_amount_add (&gorc->refund_amount,
                                   &gorc->refund_amount,
                                   refund_amount));
  gorc->refunded = true;
}


/**
 * Function called with available wire details, to be added to
 * the response.
 *
 * @param cls a `struct GetOrderRequestContext`
 * @param wtid wire transfer subject of the wire transfer for the coin
 * @param exchange_url base URL of the exchange that made the payment
 * @param execution_time when was the payment made
 * @param deposit_value contribution of the coin to the total wire transfer value
 * @param deposit_fee deposit fee charged by the exchange for the coin
 * @param transfer_confirmed did the merchant confirm that a wire transfer with
 *        @a wtid over the total amount happened?
 */
static void
process_transfer_details (void *cls,
                          const struct TALER_WireTransferIdentifierRawP *wtid,
                          const char *exchange_url,
                          struct GNUNET_TIME_Absolute execution_time,
                          const struct TALER_Amount *deposit_value,
                          const struct TALER_Amount *deposit_fee,
                          bool transfer_confirmed)
{
  struct GetOrderRequestContext *gorc = cls;
  json_t *wire_details = gorc->wire_details;
  struct TALER_Amount wired;
  struct GNUNET_TIME_Absolute execution_time_round = execution_time;

  /* Compute total amount *wired* */
  GNUNET_assert (0 <
                 TALER_amount_add (&gorc->deposits_total,
                                   &gorc->deposits_total,
                                   deposit_value));
  GNUNET_assert (0 <
                 TALER_amount_add (&gorc->deposit_fees_total,
                                   &gorc->deposit_fees_total,
                                   deposit_fee));

  GNUNET_TIME_round_abs (&execution_time_round);
  GNUNET_assert
    (0 <= TALER_amount_subtract (&wired,
                                 deposit_value,
                                 deposit_fee));
  GNUNET_assert (0 ==
                 json_array_append_new (
                   wire_details,
                   json_pack ("{s:o, s:s, s:o, s:o, s:b}",
                              "wtid",
                              GNUNET_JSON_from_data_auto (wtid),
                              "exchange_url",
                              exchange_url,
                              "amount",
                              TALER_JSON_from_amount (&wired),
                              "execution_time",
                              GNUNET_JSON_from_time_abs (execution_time_round),
                              "confirmed",
                              transfer_confirmed)));
}


/**
 * Manages a GET /private/orders/ID call, checking the status of a payment and
 * refunds and, if necessary, constructing the URL for a payment redirect URL.
 *
 * @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_ID (const struct TMH_RequestHandler *rh,
                           struct MHD_Connection *connection,
                           struct TMH_HandlerContext *hc)
{
  struct GetOrderRequestContext *gorc = hc->ctx;
  enum GNUNET_DB_QueryStatus qs;
  bool paid;
  bool wired;
  bool order_only = false;
  struct TALER_ClaimTokenP claim_token = { 0 };

  if (NULL == gorc)
  {
    /* First time here, parse request and check order is known */
    GNUNET_assert (NULL != hc->infix);
    gorc = GNUNET_new (struct GetOrderRequestContext);
    hc->cc = &gorc_cleanup;
    hc->ctx = gorc;
    gorc->sc.con = connection;
    gorc->hc = hc;
    gorc->wire_details = json_array ();
    GNUNET_assert (NULL != gorc->wire_details);
    gorc->refund_details = json_array ();
    GNUNET_assert (NULL != gorc->refund_details);
    gorc->wire_reports = json_array ();
    GNUNET_assert (NULL != gorc->wire_reports);
    gorc->session_id = MHD_lookup_connection_value (connection,
                                                    MHD_GET_ARGUMENT_KIND,
                                                    "session_id");
    {
      const char *long_poll_timeout_s;

      long_poll_timeout_s = MHD_lookup_connection_value (connection,
                                                         MHD_GET_ARGUMENT_KIND,
                                                         "timeout_ms");
      if (NULL != long_poll_timeout_s)
      {
        unsigned long long timeout;

        if (1 != sscanf (long_poll_timeout_s,
                         "%llu",
                         &timeout))
        {
          GNUNET_break_op (0);
          return TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_BAD_REQUEST,
                                             TALER_EC_PARAMETER_MALFORMED,
                                             "timeout_ms must be non-negative number");
        }
        gorc->sc.long_poll_timeout
          = GNUNET_TIME_relative_to_absolute (GNUNET_TIME_relative_multiply (
                                                GNUNET_TIME_UNIT_MILLISECONDS,
                                                timeout));
      }
      else
      {
        gorc->sc.long_poll_timeout = GNUNET_TIME_UNIT_ZERO_ABS;
      }
    }

    {
      const char *transfer_s;

      transfer_s = MHD_lookup_connection_value (connection,
                                                MHD_GET_ARGUMENT_KIND,
                                                "transfer");
      if ( (NULL != transfer_s) &&
           (0 == strcasecmp (transfer_s,
                             "yes")) )
        gorc->transfer_status_requested = true;
    }
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Starting GET /private/orders/%s processing with timeout %s\n",
                hc->infix,
                GNUNET_STRINGS_absolute_time_to_string (
                  gorc->sc.long_poll_timeout));

    TMH_db->preflight (TMH_db->cls);
    qs = TMH_db->lookup_contract_terms (TMH_db->cls,
                                        hc->instance->settings.id,
                                        hc->infix,
                                        &gorc->contract_terms,
                                        &gorc->order_serial);
    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
    {
      struct GNUNET_HashCode unused;

      /* We don't have contract terms, but the order may still exist. */
      qs = TMH_db->lookup_order (TMH_db->cls,
                                 hc->instance->settings.id,
                                 hc->infix,
                                 &claim_token,
                                 &unused,
                                 &gorc->contract_terms);
      order_only = true;
    }
    if (0 > qs)
    {
      /* single, read-only SQL statements should never cause
         serialization problems */
      GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
      /* Always report on hard error as well to enable diagnostics */
      GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
                                         NULL);
    }
    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
    {
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_NOT_FOUND,
                                         TALER_EC_GET_ORDERS_ORDER_NOT_FOUND,
                                         hc->infix);
    }

    /* extract the fulfillment URL and total amount from the contract terms! */
    {
      struct GNUNET_JSON_Specification spec[] = {
        TALER_JSON_spec_amount ("amount",
                                &gorc->contract_amount),
        GNUNET_JSON_spec_end ()
      };

      if (GNUNET_OK !=
          GNUNET_JSON_parse (gorc->contract_terms,
                             spec,
                             NULL, NULL))
      {
        GNUNET_break (0);
        return TALER_MHD_reply_with_error (
          connection,
          MHD_HTTP_INTERNAL_SERVER_ERROR,
          TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
          hc->infix);
      }
      if (0 !=
          strcasecmp (TMH_currency,
                      gorc->contract_amount.currency))
      {
        GNUNET_break (0);
        return TALER_MHD_reply_with_error (
          connection,
          MHD_HTTP_INTERNAL_SERVER_ERROR,
          TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
          gorc->contract_amount.currency);
      }
    }
    gorc->fulfillment_url
      = json_string_value (json_object_get (gorc->contract_terms,
                                            "fulfillment_url"));

    if (! order_only)
    {
      if (GNUNET_OK !=
          TALER_JSON_contract_hash (gorc->contract_terms,
                                    &gorc->h_contract_terms))
      {
        GNUNET_break (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_GET_ORDERS_FAILED_COMPUTE_PROPOSAL_HASH,
                                           NULL);
      }
    }
  }
  if (TALER_EC_NONE != gorc->wire_ec)
  {
    return TALER_MHD_reply_with_error (connection,
                                       gorc->wire_hc,
                                       gorc->wire_ec,
                                       NULL);
  }

  GNUNET_assert (NULL != gorc->contract_terms);

  TMH_db->preflight (TMH_db->cls);
  if (order_only)
  {
    paid = false;
    wired = false;
  }
  else
  {
    qs = TMH_db->lookup_payment_status (TMH_db->cls,
                                        gorc->order_serial,
                                        gorc->session_id,
                                        &paid,
                                        &wired);
    if (0 > qs)
    {
      /* single, read-only SQL statements should never cause
         serialization problems, and the entry should exist as per above */
      GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_GET_ORDERS_DB_FETCH_PAYMENT_STATUS,
                                         NULL);
    }
  }
  if ( (! paid) &&
       (NULL != gorc->fulfillment_url) &&
       (NULL != gorc->session_id) )
  {
    char *already_paid_order_id;

    qs = TMH_db->lookup_order_by_fulfillment (TMH_db->cls,
                                              hc->instance->settings.id,
                                              gorc->fulfillment_url,
                                              gorc->session_id,
                                              &already_paid_order_id);
    if (0 > qs)
    {
      /* single, read-only SQL statements should never cause
         serialization problems, and the entry should exist as per above */
      GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_GET_ORDERS_DB_FETCH_PAYMENT_STATUS,
                                         NULL);
    }
    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
    {
      /* User did pay for this order, but under a different session; ask wallet
         to switch order ID */
      char *taler_pay_uri;
      char *order_status_url;
      MHD_RESULT ret;

      taler_pay_uri = TMH_make_taler_pay_uri (connection,
                                              hc->infix,
                                              gorc->session_id,
                                              hc->instance->settings.id,
                                              &claim_token);
      order_status_url = TMH_make_order_status_url (connection,
                                                    hc->infix,
                                                    gorc->session_id,
                                                    hc->instance->settings.id,
                                                    &claim_token);
      ret = TALER_MHD_reply_json_pack (connection,
                                       MHD_HTTP_OK,
                                       "{s:s, s:s, s:s, s:s, s:s?}",
                                       "taler_pay_uri",
                                       taler_pay_uri,
                                       "order_status_url",
                                       order_status_url,
                                       "order_status",
                                       "unpaid",
                                       "already_paid_order_id",
                                       already_paid_order_id,
                                       "already_paid_fulfillment_url",
                                       gorc->fulfillment_url);
      GNUNET_free (taler_pay_uri);
      GNUNET_free (already_paid_order_id);
      return ret;
    }
  }

  if (paid &&
      (! wired) &&
      gorc->transfer_status_requested)
  {
    /* suspend connection, wait for exchange to check wire transfer status there */
    gorc->transfer_status_requested = false;   /* only try ONCE */
    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_get_zero (TMH_currency,
                                          &gorc->deposits_total));
    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_get_zero (TMH_currency,
                                          &gorc->deposit_fees_total));
    TMH_db->lookup_deposits_by_order (TMH_db->cls,
                                      gorc->order_serial,
                                      &deposit_cb,
                                      gorc);
    if (NULL != gorc->tq_head)
    {
      GNUNET_CONTAINER_DLL_insert (gorc_head,
                                   gorc_tail,
                                   gorc);
      gorc->tt = GNUNET_SCHEDULER_add_delayed (EXCHANGE_TIMEOUT,
                                               &exchange_timeout_cb,
                                               gorc);
      MHD_suspend_connection (connection);
      return MHD_YES;
    }
  }

  if ( (! paid) &&
       (0 != gorc->sc.long_poll_timeout.abs_value_us) )
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Suspending GET /private/orders/%s\n",
                hc->infix);
    TMH_long_poll_suspend (hc->infix,
                           hc->instance,
                           &gorc->sc,
                           NULL);
    return MHD_YES;
  }

  if (! paid)
  {
    /* User never paid for this order */
    char *taler_pay_uri;
    char *order_status_url;
    MHD_RESULT ret;

    taler_pay_uri = TMH_make_taler_pay_uri (connection,
                                            hc->infix,
                                            gorc->session_id,
                                            hc->instance->settings.id,
                                            &claim_token);
    order_status_url = TMH_make_order_status_url (connection,
                                                  hc->infix,
                                                  gorc->session_id,
                                                  hc->instance->settings.id,
                                                  &claim_token);
    ret = TALER_MHD_reply_json_pack (connection,
                                     MHD_HTTP_OK,
                                     "{s:s, s:s, s:s}",
                                     "taler_pay_uri",
                                     taler_pay_uri,
                                     "order_status_url",
                                     order_status_url,
                                     "order_status",
                                     "unpaid");
    GNUNET_free (taler_pay_uri);
    GNUNET_free (order_status_url);
    return ret;
  }

  /* Here we know the user DID pay, compute refunds... */
  GNUNET_assert (! order_only);
  GNUNET_assert (paid);
  /* Accumulate refunds, if any. */
  {
    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_get_zero (TMH_currency,
                                          &gorc->refund_amount));
    qs = TMH_db->lookup_refunds_detailed (TMH_db->cls,
                                          hc->instance->settings.id,
                                          &gorc->h_contract_terms,
                                          &process_refunds_cb,
                                          gorc);
  }
  if (0 > qs)
  {
    GNUNET_break (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_GET_ORDERS_DB_FETCH_TRANSACTION_ERROR,
                                       NULL);
  }

  /* Generate final reply, including wire details if we have them */
  {
    MHD_RESULT ret;
    char *order_status_url;

    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_get_zero (TMH_currency,
                                          &gorc->deposits_total));
    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_get_zero (TMH_currency,
                                          &gorc->deposit_fees_total));
    qs = TMH_db->lookup_transfer_details_by_order (TMH_db->cls,
                                                   gorc->order_serial,
                                                   &process_transfer_details,
                                                   gorc);
    if (0 > qs)
    {
      GNUNET_break (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_PAY_DB_FETCH_TRANSACTION_ERROR,
                                         NULL);
    }

    if (! wired)
    {
      /* we believe(d) the wire transfer did not happen yet, check if maybe
         in light of new evidence it did */
      struct TALER_Amount expect_total;

      if (0 >
          TALER_amount_subtract (&expect_total,
                                 &gorc->contract_amount,
                                 &gorc->refund_amount))
      {
        GNUNET_break (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_GET_ORDERS_CONTRACT_CONTENT_INVALID,
                                           "refund exceeds contract value");
      }
      if (0 >
          TALER_amount_subtract (&expect_total,
                                 &expect_total,
                                 &gorc->deposit_fees_total))
      {
        GNUNET_break (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_GET_ORDERS_CONTRACT_CONTENT_INVALID,
                                           "deposit fees exceed total minus refunds");
      }
      if (0 >=
          TALER_amount_cmp (&expect_total,
                            &gorc->deposits_total))
      {
        struct GNUNET_TIME_Absolute timestamp;

        /* expect_total <= gorc->deposits_total: good: we got paid */
        wired = true;
        qs = TMH_db->mark_order_wired (TMH_db->cls,
                                       gorc->order_serial);
        GNUNET_break (qs >= 0); /* just warn if transaction failed */
        {
          struct GNUNET_JSON_Specification spec[] = {
            TALER_JSON_spec_absolute_time ("timestamp",
                                           &timestamp),
            GNUNET_JSON_spec_end ()
          };
          enum GNUNET_GenericReturnValue res;

          res = TALER_MHD_parse_internal_json_data (connection,
                                                    gorc->contract_terms,
                                                    spec);
          if (GNUNET_YES != res)
          {
            GNUNET_break (0);
            return res;
          }
        }
        TMH_notify_order_change (hc->instance,
                                 hc->infix,
                                 true, /* paid */
                                 false, /* technically unknown, but OK here */
                                 true, /* wired */
                                 timestamp,
                                 gorc->order_serial);
      }
    }

    order_status_url = TMH_make_order_status_url (connection,
                                                  hc->infix,
                                                  gorc->session_id,
                                                  hc->instance->settings.id,
                                                  &claim_token);

    ret = TALER_MHD_reply_json_pack (connection,
                                     MHD_HTTP_OK,
                                     "{s:o, s:I, s:I, s:o, s:O,"
                                     " s:s, s:b, s:b, s:o, s:o, s:o, s:s}",
                                     "wire_reports",
                                     gorc->wire_reports,
                                     "exchange_ec",
                                     (json_int_t) gorc->exchange_ec,
                                     "exchange_hc",
                                     (json_int_t) gorc->exchange_hc,
                                     "deposit_total",
                                     TALER_JSON_from_amount (
                                       &gorc->deposits_total),
                                     "contract_terms",
                                     gorc->contract_terms,
                                     "order_status",
                                     "paid",
                                     "refunded",
                                     gorc->refunded,
                                     "wired",
                                     wired,
                                     "refund_amount",
                                     TALER_JSON_from_amount (
                                       &gorc->refund_amount),
                                     "wire_details",
                                     gorc->wire_details,
                                     "refund_details",
                                     gorc->refund_details,
                                     "order_status_url",
                                     order_status_url);
    GNUNET_free (order_status_url);
    gorc->wire_details = NULL;
    gorc->wire_reports = NULL;
    gorc->refund_details = NULL;
    return ret;
  }
}