/*
  This file is part of TALER
  (C) 2014-2020 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_get-orders-ID.c
 * @brief implementation of GET /orders/$ID
 * @author Marcello Stanisci
 * @author Christian Grothoff
 */
#include "platform.h"
#include <jansson.h>
#include <taler/taler_signatures.h>
#include <taler/taler_json_lib.h>
#include <taler/taler_exchange_service.h>
#include "taler-merchant-httpd_exchanges.h"
#include "taler-merchant-httpd_get-orders-ID.h"
#include "taler-merchant-httpd_mhd.h"
#include "taler-merchant-httpd_qr.h"
#include "taler-merchant-httpd_templating.h"

/**
 * How often do we retry DB transactions on serialization failures?
 */
#define MAX_RETRIES 5


/**
 * Context for the operation.
 */
struct GetOrderData
{

  /**
   * Hashed version of contract terms. All zeros if not provided.
   */
  struct GNUNET_HashCode h_contract_terms;

  /**
   * Claim token used for access control. All zeros if not provided.
   */
  struct TALER_ClaimTokenP claim_token;

  /**
   * DLL of (suspended) requests.
   */
  struct GetOrderData *next;

  /**
   * DLL of (suspended) requests.
   */
  struct GetOrderData *prev;

  /**
   * Context of the request.
   */
  struct TMH_HandlerContext *hc;

  /**
   * 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 MerchantInstance *mi;

  /**
   * order ID for the payment
   */
  const char *order_id;

  /**
   * Where to get the contract
   */
  const char *contract_url;

  /**
   * fulfillment URL of the contract (valid as long as @e contract_terms is
   * valid; but can also be NULL if the contract_terms does not come with
   * a fulfillment URL).
   */
  const char *fulfillment_url;

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

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

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

  /**
   * Did we suspend @a connection?
   */
  bool suspended;

  /**
   * Return code: #TALER_EC_NONE if successful.
   */
  enum TALER_ErrorCode ec;

  /**
   * Set to true if we are dealing with an unclaimed order
   * (and thus @e h_contract_terms is not set, and certain
   * DB queries will not work).
   */
  bool unclaimed;

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

  /**
   * Set to true if a refund is still available for the
   * wallet for this payment.
   */
  bool refund_available;

  /**
   * Set to true if the client requested HTML, otherwise we generate JSON.
   */
  bool generate_html;

};


/**
 * Head of DLL of (suspended) requests.
 */
static struct GetOrderData *god_head;

/**
 * Tail of DLL of (suspended) requests.
 */
static struct GetOrderData *god_tail;


/**
 * Force resuming all suspended order lookups, needed during shutdown.
 */
void
TMH_force_wallet_get_order_resume (void)
{
  struct GetOrderData *god;

  while (NULL != (god = god_head))
  {
    GNUNET_CONTAINER_DLL_remove (god_head,
                                 god_tail,
                                 god);
    GNUNET_assert (god->suspended);
    god->suspended = false;
    MHD_resume_connection (god->sc.con);
  }
}


/**
 * Suspend this @a god until the trigger is satisfied.
 *
 * @param god request to suspend
 */
static void
suspend_god (struct GetOrderData *god)
{
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Suspending GET /orders/%s\n",
              god->order_id);
  TMH_long_poll_suspend (god->order_id,
                         god->session_id,
                         god->fulfillment_url,
                         god->hc->instance,
                         &god->sc,
                         god->sc.awaiting_refund
                         ? &god->sc.refund_expected
                         : NULL);
}


/**
 * Create a taler://refund/ URI for the given @a con and @a order_id
 *  and @a instance_id.
 *
 * @param con HTTP connection
 * @param order_id the order id
 * @param instance_id instance, may be "default"
 * @return corresponding taler://refund/ URI, or NULL on missing "host"
 */
static char *
make_taler_refund_uri (struct MHD_Connection *con,
                       const char *order_id,
                       const char *instance_id)
{
  const char *host;
  const char *forwarded_host;
  const char *uri_path;
  struct GNUNET_Buffer buf = { 0 };

  host = MHD_lookup_connection_value (con,
                                      MHD_HEADER_KIND,
                                      "Host");
  forwarded_host = MHD_lookup_connection_value (con,
                                                MHD_HEADER_KIND,
                                                "X-Forwarded-Host");

  uri_path = MHD_lookup_connection_value (con,
                                          MHD_HEADER_KIND,
                                          "X-Forwarded-Prefix");
  if (NULL != forwarded_host)
    host = forwarded_host;
  if (NULL == host)
  {
    GNUNET_break (0);
    return NULL;
  }

  GNUNET_assert (NULL != instance_id);
  GNUNET_assert (NULL != order_id);

  GNUNET_buffer_write_str (&buf,
                           "taler");
  if (GNUNET_NO == TALER_mhd_is_https (con))
    GNUNET_buffer_write_str (&buf,
                             "+http");
  GNUNET_buffer_write_str (&buf,
                           "://refund/");
  GNUNET_buffer_write_str (&buf,
                           host);
  if (NULL != uri_path)
    GNUNET_buffer_write_path (&buf,
                              uri_path);
  if (0 != strcmp ("default",
                   instance_id))
  {
    GNUNET_buffer_write_path (&buf,
                              "instances");
    GNUNET_buffer_write_path (&buf,
                              instance_id);
  }
  GNUNET_buffer_write_path (&buf,
                            order_id);
  GNUNET_buffer_write_path (&buf,
                            ""); // Trailing slash
  return GNUNET_buffer_reap_str (&buf);
}


/**
 * Create a http(s) URL for the given @a con and @a order_id
 * and @a instance_id to display the /orders/{order_id} page.
 *
 * @param con HTTP connection
 * @param order_id the order id
 * @param session_id the session id
 * @param instance_id instance, may be "default"
 * @param claim_token claim token for the order, may be NULL
 * @param h_contract contract hash for authentication, may be NULL
 * @return corresponding http(s):// URL, or NULL on missing "host"
 */
char *
TMH_make_order_status_url (struct MHD_Connection *con,
                           const char *order_id,
                           const char *session_id,
                           const char *instance_id,
                           struct TALER_ClaimTokenP *claim_token,
                           struct GNUNET_HashCode *h_contract)
{
  const char *host;
  const char *forwarded_host;
  const char *uri_path;
  struct GNUNET_Buffer buf = { 0 };
  /* Number of query parameters written so far */
  unsigned int num_qp = 0;

  host = MHD_lookup_connection_value (con,
                                      MHD_HEADER_KIND,
                                      "Host");
  forwarded_host = MHD_lookup_connection_value (con,
                                                MHD_HEADER_KIND,
                                                "X-Forwarded-Host");

  uri_path = MHD_lookup_connection_value (con,
                                          MHD_HEADER_KIND,
                                          "X-Forwarded-Prefix");
  if (NULL != forwarded_host)
    host = forwarded_host;

  if (NULL == host)
  {
    GNUNET_break (0);
    return NULL;
  }

  GNUNET_assert (NULL != instance_id);
  GNUNET_assert (NULL != order_id);

  if (GNUNET_NO == TALER_mhd_is_https (con))
    GNUNET_buffer_write_str (&buf,
                             "http://");
  else
    GNUNET_buffer_write_str (&buf,
                             "https://");

  GNUNET_buffer_write_str (&buf,
                           host);
  if (NULL != uri_path)
    GNUNET_buffer_write_path (&buf,
                              uri_path);
  if (0 != strcmp ("default",
                   instance_id))
  {
    GNUNET_buffer_write_path (&buf,
                              "instances");
    GNUNET_buffer_write_path (&buf,
                              instance_id);
  }
  GNUNET_buffer_write_path (&buf,
                            "/orders");
  GNUNET_buffer_write_path (&buf,
                            order_id);
  if ((NULL != claim_token) &&
      (GNUNET_NO == GNUNET_is_zero (claim_token)))
  {
    GNUNET_buffer_write_str (&buf,
                             "?token=");
    GNUNET_buffer_write_data_encoded (&buf,
                                      (char *) claim_token,
                                      sizeof (struct TALER_ClaimTokenP));
    num_qp++;
  }

  if (NULL != session_id)
  {
    if (num_qp > 0)
      GNUNET_buffer_write_str (&buf,
                               "&session_id=");
    else
      GNUNET_buffer_write_str (&buf,
                               "?session_id=");
    GNUNET_buffer_write_str (&buf,
                             session_id);
    num_qp++;
  }

  if (NULL != h_contract)
  {
    if (num_qp > 0)
      GNUNET_buffer_write_str (&buf,
                               "&h_contract=");
    else
      GNUNET_buffer_write_str (&buf,
                               "?h_contract=");
    GNUNET_buffer_write_data_encoded (&buf,
                                      (char *) h_contract,
                                      sizeof (struct GNUNET_HashCode));
  }

  return GNUNET_buffer_reap_str (&buf);
}


/**
 * Create a taler://pay/ URI for the given @a con and @a order_id
 * and @a session_id and @a instance_id.
 *
 * @param con HTTP connection
 * @param order_id the order id
 * @param session_id session, may be NULL
 * @param instance_id instance, may be "default"
 * @param claim_token claim token for the order, may be NULL
 * @return corresponding taler://pay/ URI, or NULL on missing "host"
 */
char *
TMH_make_taler_pay_uri (struct MHD_Connection *con,
                        const char *order_id,
                        const char *session_id,
                        const char *instance_id,
                        struct TALER_ClaimTokenP *claim_token)
{
  const char *host;
  const char *forwarded_host;
  const char *uri_path;
  struct GNUNET_Buffer buf = { 0 };

  host = MHD_lookup_connection_value (con,
                                      MHD_HEADER_KIND,
                                      "Host");
  forwarded_host = MHD_lookup_connection_value (con,
                                                MHD_HEADER_KIND,
                                                "X-Forwarded-Host");

  uri_path = MHD_lookup_connection_value (con,
                                          MHD_HEADER_KIND,
                                          "X-Forwarded-Prefix");
  if (NULL != forwarded_host)
    host = forwarded_host;

  if (NULL == host)
  {
    GNUNET_break (0);
    return NULL;
  }

  GNUNET_assert (NULL != instance_id);
  GNUNET_assert (NULL != order_id);

  GNUNET_buffer_write_str (&buf,
                           "taler");
  if (GNUNET_NO == TALER_mhd_is_https (con))
    GNUNET_buffer_write_str (&buf,
                             "+http");
  GNUNET_buffer_write_str (&buf,
                           "://pay/");
  GNUNET_buffer_write_str (&buf,
                           host);
  if (NULL != uri_path)
    GNUNET_buffer_write_path (&buf,
                              uri_path);
  if (0 != strcmp ("default",
                   instance_id))
  {
    GNUNET_buffer_write_path (&buf,
                              "instances");
    GNUNET_buffer_write_path (&buf,
                              instance_id);
  }
  GNUNET_buffer_write_path (&buf,
                            order_id);
  GNUNET_buffer_write_path (&buf,
                            (session_id == NULL) ? "" : session_id);
  if ((NULL != claim_token) &&
      (GNUNET_NO == GNUNET_is_zero (claim_token)))
  {
    GNUNET_buffer_write_str (&buf,
                             "?c=");
    GNUNET_buffer_write_data_encoded (&buf,
                                      (char *) claim_token,
                                      sizeof (struct TALER_ClaimTokenP));
  }

  return GNUNET_buffer_reap_str (&buf);
}


/**
 * Return the order summary of the contract of @a god in the
 * preferred language of the HTTP client.
 *
 * @param god order to extract summary from
 * @return NULL if no summary was provided in the contract
 */
static const char *
get_order_summary (struct GetOrderData *god)
{
  const char *language_pattern;
  const char *ret;

  language_pattern = MHD_lookup_connection_value (god->sc.con,
                                                  MHD_HEADER_KIND,
                                                  MHD_HTTP_HEADER_ACCEPT_LANGUAGE);
  if (NULL == language_pattern)
    language_pattern = "en";
  ret = json_string_value (TALER_JSON_extract_i18n (god->contract_terms,
                                                    language_pattern,
                                                    "summary"));
  if (NULL == ret)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "No order summary found!\n");
    ret = "<bug: no summary>";
  }
  return ret;
}


/**
 * The client did not yet pay, send it the payment request.
 *
 * @param god check pay request context
 * @param already_paid_order_id if for the fulfillment URI there is
 *          already a paid order, this is the order ID to redirect
 *          the wallet to; NULL if not applicable
 * @return #MHD_YES on success
 */
static MHD_RESULT
send_pay_request (struct GetOrderData *god,
                  const char *already_paid_order_id)
{
  MHD_RESULT ret;
  char *taler_pay_uri;
  char *order_status_url;
  struct GNUNET_TIME_Relative remaining;

  remaining = GNUNET_TIME_absolute_get_remaining (god->sc.long_poll_timeout);
  if ( (0 != remaining.rel_value_us) &&
       ( (NULL == already_paid_order_id) ||
         (NULL == god->fulfillment_url) ) )
  {
    /* long polling: do not queue a response, suspend connection instead */
    suspend_god (god);
    return MHD_YES;
  }

  /* Check if resource_id has been paid for in the same session
   * with another order_id.
   */
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Sending payment request in /poll-payment\n");
  taler_pay_uri = TMH_make_taler_pay_uri (god->sc.con,
                                          god->order_id,
                                          god->session_id,
                                          god->hc->instance->settings.id,
                                          &god->claim_token);
  order_status_url = TMH_make_order_status_url (god->sc.con,
                                                god->order_id,
                                                god->session_id,
                                                god->hc->instance->settings.id,
                                                &god->claim_token,
                                                NULL);
  if (god->generate_html)
  {
    char *qr;

    if ( (NULL != already_paid_order_id) &&
         (NULL != god->fulfillment_url) )
    {
      struct MHD_Response *reply;
      MHD_RESULT ret;

      reply = MHD_create_response_from_buffer (0,
                                               NULL,
                                               MHD_RESPMEM_PERSISTENT);
      if (NULL == reply)
      {
        GNUNET_break (0);
        return MHD_NO;
      }
      GNUNET_break (MHD_YES ==
                    MHD_add_response_header (reply,
                                             MHD_HTTP_HEADER_LOCATION,
                                             god->fulfillment_url));
      ret = MHD_queue_response (god->sc.con,
                                MHD_HTTP_FOUND,
                                reply);
      MHD_destroy_response (reply);
      return ret;
    }

    qr = TMH_create_qrcode (taler_pay_uri);
    if (NULL == qr)
    {
      GNUNET_break (0);
      return MHD_NO;
    }
    {
      enum GNUNET_GenericReturnValue res;
      json_t *context;

      context = json_pack ("{s:s, s:s, s:s, s:s}",
                           "taler_pay_uri",
                           taler_pay_uri,
                           "order_status_url",
                           order_status_url,
                           "taler_pay_qrcode_svg",
                           qr,
                           "order_summary",
                           get_order_summary (god));
      GNUNET_assert (NULL != context);
      res = TMH_return_from_template (god->sc.con,
                                      MHD_HTTP_PAYMENT_REQUIRED,
                                      "request_payment",
                                      taler_pay_uri,
                                      context);
      if (GNUNET_SYSERR == res)
      {
        GNUNET_break (0);
        ret = MHD_NO;
      }
      ret = MHD_YES;
      json_decref (context);
    }
    GNUNET_free (qr);
  }
  else
  {
    ret = TALER_MHD_reply_json_pack (god->sc.con,
                                     MHD_HTTP_PAYMENT_REQUIRED,
                                     "{s:s, s:s?, s:s?}",
                                     "taler_pay_uri",
                                     taler_pay_uri,
                                     "fulfillment_url",
                                     god->fulfillment_url,
                                     "already_paid_order_id",
                                     already_paid_order_id);

  }
  GNUNET_free (taler_pay_uri);
  GNUNET_free (order_status_url);
  return ret;
}


/**
 * Function called with detailed information about a refund.
 * It is responsible for packing up the data to return.
 *
 * @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_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 GetOrderData *god = cls;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Found refund of %s for coin %s with reason `%s' in database\n",
              TALER_amount2s (refund_amount),
              TALER_B2S (coin_pub),
              reason);
  if (god->refunded)
  {
    GNUNET_assert (0 <=
                   TALER_amount_add (&god->refund_amount,
                                     &god->refund_amount,
                                     refund_amount));
    return;
  }
  god->refund_amount = *refund_amount;
  god->refunded = true;
  god->refund_available |= pending;
}


/**
 * Clean up the session state for a GET /orders/$ID request.
 *
 * @param cls must be a `struct GetOrderData *`
 */
static void
god_cleanup (void *cls)
{
  struct GetOrderData *god = cls;

  if (NULL != god->contract_terms)
    json_decref (god->contract_terms);
  GNUNET_free (god);
}


/**
 * Handle a GET "/orders/$ID" 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_get_orders_ID (const struct TMH_RequestHandler *rh,
                   struct MHD_Connection *connection,
                   struct TMH_HandlerContext *hc)
{
  struct GetOrderData *god = hc->ctx;
  const char *order_id = hc->infix;
  enum GNUNET_DB_QueryStatus qs;
  bool contract_match = false;
  bool token_match = false;
  bool contract_available = false;

  if (NULL == god)
  {
    god = GNUNET_new (struct GetOrderData);
    hc->ctx = god;
    hc->cc = &god_cleanup;
    god->sc.con = connection;
    god->hc = hc;
    god->order_id = order_id;

    {
      const char *ct;

      ct = MHD_lookup_connection_value (connection,
                                        MHD_GET_ARGUMENT_KIND,
                                        "token");
      if ( (NULL != ct) &&
           (GNUNET_OK !=
            GNUNET_STRINGS_string_to_data (ct,
                                           strlen (ct),
                                           &god->claim_token,
                                           sizeof (god->claim_token))) )
      {
        /* ct has wrong encoding */
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_PARAMETER_MALFORMED,
                                           "token");
      }
    }

    {
      const char *cts;

      cts = MHD_lookup_connection_value (connection,
                                         MHD_GET_ARGUMENT_KIND,
                                         "h_contract");
      if ( (NULL != cts) &&
           (GNUNET_OK !=
            GNUNET_CRYPTO_hash_from_string (cts,
                                            &god->h_contract_terms)) )
      {
        /* cts has wrong encoding */
        GNUNET_break_op (0);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_PARAMETER_MALFORMED,
                                           "h_contract");
      }
    }

    god->generate_html = TMH_MHD_test_html_desired (connection);
    {
      const char *long_poll_timeout_ms;

      long_poll_timeout_ms = MHD_lookup_connection_value (connection,
                                                          MHD_GET_ARGUMENT_KIND,
                                                          "timeout_ms");
      if ((NULL != long_poll_timeout_ms) &&
          ! god->generate_html)
      {
        unsigned int timeout;

        if (1 != sscanf (long_poll_timeout_ms,
                         "%u",
                         &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)");
        }
        god->sc.long_poll_timeout
          = GNUNET_TIME_relative_to_absolute (GNUNET_TIME_relative_multiply (
                                                GNUNET_TIME_UNIT_MILLISECONDS,
                                                timeout));
      }
      else
      {
        god->sc.long_poll_timeout = GNUNET_TIME_UNIT_ZERO_ABS;
      }
    }

    {
      const char *await_refund_obtained_s;

      await_refund_obtained_s =
        MHD_lookup_connection_value (connection,
                                     MHD_GET_ARGUMENT_KIND,
                                     "await_refund_obtained");

      god->sc.awaiting_refund_obtained =
        (NULL != await_refund_obtained_s)
        ? 0 == strcasecmp (await_refund_obtained_s, "yes")
        : false;
    }

    {
      const char *min_refund;

      min_refund = MHD_lookup_connection_value (connection,
                                                MHD_GET_ARGUMENT_KIND,
                                                "refund");
      if (NULL != min_refund)
      {
        if ( (GNUNET_OK !=
              TALER_string_to_amount (min_refund,
                                      &god->sc.refund_expected)) ||
             (0 != strcasecmp (god->sc.refund_expected.currency,
                               TMH_currency) ) )
        {
          GNUNET_break_op (0);
          return TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_BAD_REQUEST,
                                             TALER_EC_PARAMETER_MALFORMED,
                                             "refund");
        }
        god->sc.awaiting_refund = true;
      }
    }

    god->session_id = MHD_lookup_connection_value (connection,
                                                   MHD_GET_ARGUMENT_KIND,
                                                   "session_id");
  } /* end of first-time initialization / sanity checks */

  /* Convert order_id to h_contract_terms */
  TMH_db->preflight (TMH_db->cls);
  if (NULL == god->contract_terms)
  {
    uint64_t order_serial;

    qs = TMH_db->lookup_contract_terms (TMH_db->cls,
                                        hc->instance->settings.id,
                                        order_id,
                                        &god->contract_terms,
                                        &order_serial);
    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_LOOKUP_ERROR,
                                         NULL);
    }
  }

  /* Check client provided the right hash code of the contract terms */
  if (NULL != god->contract_terms)
  {
    struct GNUNET_HashCode h;

    contract_available = true;
    if (GNUNET_OK !=
        TALER_JSON_contract_hash (god->contract_terms,
                                  &h))
    {
      GNUNET_break (0);
      GNUNET_free (god);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_INTERNAL_LOGIC_ERROR,
                                         "could not hash contract terms");
    }
    contract_match = (0 ==
                      GNUNET_memcmp (&h,
                                     &god->h_contract_terms));
    if ( (GNUNET_NO ==
          GNUNET_is_zero (&god->h_contract_terms)) &&
         (! contract_match) )
    {
      GNUNET_break_op (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_FORBIDDEN,
                                         TALER_EC_GET_ORDER_WRONG_CONTRACT,
                                         NULL);
    }
  }

  if (! contract_match)
  {
    struct TALER_ClaimTokenP db_claim_token;
    struct GNUNET_HashCode unused;

    qs = TMH_db->lookup_order (TMH_db->cls,
                               hc->instance->settings.id,
                               order_id,
                               &db_claim_token,
                               &unused,
                               (NULL == god->contract_terms)
                               ? &god->contract_terms
                               : NULL);
    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_LOOKUP_ERROR,
                                         NULL);
    }
    god->unclaimed = (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs) &&
                     ! contract_available;
    if ( (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs) &&
         (NULL == god->contract_terms) )
    {
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "Unknown order id given: `%s'\n",
                  order_id);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_NOT_FOUND,
                                         TALER_EC_GET_ORDERS_ID_UNKNOWN,
                                         order_id);
    }
    token_match = (0 == GNUNET_memcmp (&db_claim_token,
                                       &god->claim_token));
  }   /* end unclaimed order logic */

  if (NULL == god->fulfillment_url)
    god->fulfillment_url = json_string_value (json_object_get (
                                                god->contract_terms,
                                                "fulfillment_url"));
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Token match: %d, contract match: %d, unclaimed: %d\n",
              token_match,
              contract_match,
              god->unclaimed);
  if ( (god->unclaimed) &&
       (! token_match) )
  {
    /* Token wrong, and required because contract is unclaimed */
    GNUNET_break_op (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_FORBIDDEN,
                                       TALER_EC_MERCHANT_GET_ORDER_INVALID_TOKEN,
                                       NULL);
  }
  if ( ( (! token_match) ||
         (GNUNET_YES == GNUNET_is_zero (&god->claim_token)) ) &&
       (! contract_match) )
  {
    if (NULL == god->fulfillment_url)
    {
      if (GNUNET_NO ==
          GNUNET_is_zero (&god->h_contract_terms))
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_FORBIDDEN,
                                           TALER_EC_GET_ORDER_WRONG_CONTRACT,
                                           NULL);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_FORBIDDEN,
                                         TALER_EC_MERCHANT_GET_ORDER_INVALID_TOKEN,
                                         NULL);
    }
    if (god->generate_html)
    {
      /* Contract was claimed (maybe by another device), so this client
         cannot get the status information. Redirect to fulfillment page,
         where the client may be able to pickup a fresh order -- or might
         be able authenticate via session ID */
      struct MHD_Response *reply;
      MHD_RESULT ret;

      reply = MHD_create_response_from_buffer (0,
                                               NULL,
                                               MHD_RESPMEM_PERSISTENT);
      if (NULL == reply)
      {
        GNUNET_break (0);
        return MHD_NO;
      }
      GNUNET_break (MHD_YES ==
                    MHD_add_response_header (reply,
                                             MHD_HTTP_HEADER_LOCATION,
                                             god->fulfillment_url));
      ret = MHD_queue_response (connection,
                                MHD_HTTP_FOUND,
                                reply);
      MHD_destroy_response (reply);
      return ret;
    }
    /* Need to generate JSON reply */
    return TALER_MHD_reply_json_pack (connection,
                                      MHD_HTTP_ACCEPTED,
                                      "{s:s}",
                                      "fulfillment_url",
                                      god->fulfillment_url);
  }

  if (god->unclaimed)
  {
    /* Order is unclaimed, no need to check for payments or even
       refunds, simply always generate payment request */
    return send_pay_request (god,
                             NULL);
  }

  if ( (NULL != god->session_id) &&
       (NULL != god->fulfillment_url) )
  {
    /* Check if paid within a session. */
    char *already_paid_order_id = NULL;

    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Running re-purchase detection for %s/%s\n",
                god->session_id,
                god->fulfillment_url);
    qs = TMH_db->lookup_order_by_fulfillment (TMH_db->cls,
                                              hc->instance->settings.id,
                                              god->fulfillment_url,
                                              god->session_id,
                                              &already_paid_order_id);
    if (qs < 0)
    {
      /* 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_LOOKUP_ERROR,
                                         NULL);
    }
    if ( (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs) ||
         (0 != strcmp (order_id,
                       already_paid_order_id)) )
    {
      MHD_RESULT ret;

      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Sending pay request for order %s (already paid: %s)\n",
                  order_id,
                  already_paid_order_id);
      ret = send_pay_request (god,
                              already_paid_order_id);
      GNUNET_free (already_paid_order_id);
      return ret;
    }
    GNUNET_break (1 == qs);
    GNUNET_free (already_paid_order_id);
  }

  {
    /* Check if paid. */
    struct GNUNET_HashCode h_contract;
    bool paid;

    qs = TMH_db->lookup_order_status (TMH_db->cls,
                                      hc->instance->settings.id,
                                      order_id,
                                      &h_contract,
                                      &paid);
    if (0 >= 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_LOOKUP_ERROR,
                                         NULL);
    }
    GNUNET_break (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs);
    GNUNET_break (0 ==
                  GNUNET_memcmp (&h_contract,
                                 &god->h_contract_terms));
    if (! paid)
    {
      return send_pay_request (god,
                               NULL);
    }
  }

  /* At this point, we know the contract was paid. Let's check for
     refunds. First, clear away refunds found from previous invocations. */
  GNUNET_assert (GNUNET_OK ==
                 TALER_amount_get_zero (TMH_currency,
                                        &god->refund_amount));
  qs = TMH_db->lookup_refunds_detailed (TMH_db->cls,
                                        hc->instance->settings.id,
                                        &god->h_contract_terms,
                                        &process_refunds_cb,
                                        god);
  if (0 > qs)
  {
    GNUNET_break (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
                                       NULL);
  }

  if ( ((god->sc.awaiting_refund) &&
        ( (! god->refunded) ||
          (1 != TALER_amount_cmp (&god->refund_amount,
                                  &god->sc.refund_expected)) )) ||
       ((god->sc.awaiting_refund_obtained) &&
        (god->refund_available)) )
  {
    /* Client is waiting for a refund larger than what we have, suspend
       until timeout */
    struct GNUNET_TIME_Relative remaining;

    remaining = GNUNET_TIME_absolute_get_remaining (god->sc.long_poll_timeout);
    if (0 != remaining.rel_value_us)
    {
      /* yes, indeed suspend */
      if (god->sc.awaiting_refund)
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                    "Awaiting refund exceeding %s\n",
                    TALER_amount2s (&god->sc.refund_expected));
      if (god->sc.awaiting_refund_obtained)
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                    "Awaiting pending refunds\n");
      suspend_god (god);
      return MHD_YES;
    }
  }

  /* All operations done, build final response */
  {
    if (god->generate_html)
    {
      enum GNUNET_GenericReturnValue res;

      if (god->refund_available)
      {
        char *qr;
        char *uri;

        GNUNET_assert (NULL != god->contract_terms);
        uri = make_taler_refund_uri (god->sc.con,
                                     order_id,
                                     hc->instance->settings.id);
        if (NULL == uri)
        {
          GNUNET_break (0);
          return TALER_MHD_reply_with_error (god->sc.con,
                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
                                             TALER_EC_ALLOCATION_FAILURE,
                                             "refund URI");
        }
        qr = TMH_create_qrcode (uri);
        if (NULL == qr)
        {
          GNUNET_break (0);
          GNUNET_free (uri);
          return TALER_MHD_reply_with_error (god->sc.con,
                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
                                             TALER_EC_ALLOCATION_FAILURE,
                                             "qr code");
        }
        {
          json_t *context;

          context = json_pack ("{s:s, s:s, s:s, s:s}",
                               "order_summary",
                               get_order_summary (god),
                               "refund_amount",
                               TALER_amount2s (&god->refund_amount),
                               "taler_refund_uri",
                               uri,
                               "taler_refund_qrcode_svg",
                               qr);
          GNUNET_assert (NULL != context);
          res = TMH_return_from_template (god->sc.con,
                                          MHD_HTTP_OK,
                                          "offer_refund",
                                          uri,
                                          context);
          json_decref (context);
        }
        GNUNET_free (uri);
        GNUNET_free (qr);
      }
      else
      {
        json_t *context;

        context = json_pack ("{s:O, s:s, s:s}",
                             "contract_terms",
                             god->contract_terms,
                             "order_summary",
                             get_order_summary (god),
                             "refund_amount",
                             TALER_amount2s (&god->refund_amount));
        GNUNET_assert (NULL != context);
        res = TMH_return_from_template (god->sc.con,
                                        MHD_HTTP_OK,
                                        "show_order_details",
                                        NULL,
                                        context);
        json_decref (context);
      }
      if (GNUNET_SYSERR == res)
      {
        GNUNET_break (0);
        return MHD_NO;
      }
      return MHD_YES;
    }
    else
    {
      return TALER_MHD_reply_json_pack (
        connection,
        MHD_HTTP_OK,
        "{s:b, s:b, s:o}",
        "refunded", god->refunded,
        "refund_pending", god->refund_available,
        "refund_amount",
        TALER_JSON_from_amount (&god->refund_amount));
    }
  }
}


/* end of taler-merchant-httpd_get-orders-ID.c */