merchant

taler-merchant-httpd_post-private-orders.c (132860B)

---

 /*
   This file is part of TALER
   (C) 2014-2025 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 src/backend/taler-merchant-httpd_post-private-orders.c
  * @brief the POST /orders handler
  * @author Christian Grothoff
  * @author Marcello Stanisci
  * @author Christian Blättler
  */
 #include "platform.h"
 #include <gnunet/gnunet_common.h>
 #include <gnunet/gnunet_db_lib.h>
 #include <gnunet/gnunet_json_lib.h>
 #include <gnunet/gnunet_time_lib.h>
 #include <jansson.h>
 #include <microhttpd.h>
 #include <string.h>
 #include <taler/taler_error_codes.h>
 #include <taler/taler_signatures.h>
 #include <taler/taler_json_lib.h>
 #include <taler/taler_dbevents.h>
 #include <taler/taler_util.h>
 #include <taler/taler_merchant_util.h>
 #include <time.h>
 #include "taler-merchant-httpd.h"
 #include "taler-merchant-httpd_exchanges.h"
 #include "taler-merchant-httpd_post-private-orders.h"
 #include "taler-merchant-httpd_get-exchanges.h"
 #include "taler-merchant-httpd_contract.h"
 #include "taler-merchant-httpd_helper.h"
 #include "taler-merchant-httpd_get-private-orders.h"
 #include "merchantdb_lib.h"
 #include "merchant-database/start.h"
 #include "merchant-database/event_listen.h"
 #include "merchant-database/event_notify.h"
 #include "merchant-database/preflight.h"
 #include "merchant-database/do_expire_locks.h"
 #include "merchant-database/get_missing_money_pot.h"
 #include "merchant-database/insert_order.h"
 #include "merchant-database/insert_order_lock.h"
 #include "merchant-database/insert_token_family_key.h"
 #include "merchant-database/get_order.h"
 #include "merchant-database/get_order_summary.h"
 #include "merchant-database/get_product.h"
 #include "merchant-database/get_token_family_key.h"
 #include "merchant-database/update_token_family_key_expiration.h"
 #include "merchant-database/iterate_token_family_keys.h"
 #include "merchant-database/iterate_donau_instances_filtered.h"
 #include "merchant-database/get_otp_device.h"
 #include "merchant-database/delete_inventory_lock.h"
 
 
 /**
  * How often do we retry the simple INSERT database transaction?
  */
 #define MAX_RETRIES 3
 
 /**
  * Maximum number of inventory products per order.
  */
 #define MAX_PRODUCTS 1024
 
 /**
  * What is the label under which we find/place the merchant's
  * jurisdiction in the locations list by default?
  */
 #define STANDARD_LABEL_MERCHANT_JURISDICTION "_mj"
 
 /**
  * What is the label under which we find/place the merchant's
  * address in the locations list by default?
  */
 #define STANDARD_LABEL_MERCHANT_ADDRESS "_ma"
 
 /**
  * How long do we wait at most for /keys from the exchange(s)?
  * Ensures that we do not block forever just because some exchange
  * fails to respond *or* because our taler-merchant-keyscheck
  * refuses a forced download.
  */
 #define MAX_KEYS_WAIT \
         GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 2500)
 
 /**
  * Generate the base URL for the given merchant instance.
  *
  * @param connection the MHD connection
  * @param instance_id the merchant instance ID
  * @returns the merchant instance's base URL
  */
 static char *
 make_merchant_base_url (struct MHD_Connection *connection,
                         const char *instance_id)
 {
   struct GNUNET_Buffer buf;
 
   if (GNUNET_OK !=
       TMH_base_url_by_connection (connection,
                                   instance_id,
                                   &buf))
     return NULL;
   GNUNET_buffer_write_path (&buf,
                             "");
   return GNUNET_buffer_reap_str (&buf);
 }
 
 
 /**
  * Information about a product we are supposed to add to the order
  * based on what we know it from our inventory.
  */
 struct InventoryProduct
 {
   /**
    * Identifier of the product in the inventory.
    */
   const char *product_id;
 
   /**
    * Number of units of the product to add to the order (integer part).
    */
   uint64_t quantity;
 
   /**
    * Fractional part of the quantity in units of 1/1000000 of the base value.
    */
   uint32_t quantity_frac;
 
   /**
    * True if the integer quantity field was missing in the request.
    */
   bool quantity_missing;
 
   /**
    * String representation of the quantity, if supplied.
    */
   const char *unit_quantity;
 
   /**
    * True if the string quantity field was missing in the request.
    */
   bool unit_quantity_missing;
 
   /**
    * Money pot associated with the product. 0 for none.
    */
   uint64_t product_money_pot;
 
 };
 
 
 /**
  * Handle for a rekey operation where we (re)request
  * the /keys from the exchange.
  */
 struct RekeyExchange
 {
   /**
    * Kept in a DLL.
    */
   struct RekeyExchange *prev;
 
   /**
    * Kept in a DLL.
    */
   struct RekeyExchange *next;
 
   /**
    * order this is for.
    */
   struct OrderContext *oc;
 
   /**
    * Base URL of the exchange.
    */
   char *url;
 
   /**
    * Request for keys.
    */
   struct TMH_EXCHANGES_KeysOperation *fo;
 
 };
 
 
 /**
  * Data structure where we evaluate the viability of a given
  * wire method for this order.
  */
 struct WireMethodCandidate
 {
   /**
    * Kept in a DLL.
    */
   struct WireMethodCandidate *next;
 
   /**
    * Kept in a DLL.
    */
   struct WireMethodCandidate *prev;
 
   /**
    * The wire method we are evaluating.
    */
   const struct TMH_WireMethod *wm;
 
   /**
    * List of exchanges to use when we use this wire method.
    */
   json_t *exchanges;
 
   /**
    * Set of maximum amounts that could be paid over all available exchanges
    * for this @a wm. Used to determine if this order creation requests exceeds
    * legal limits.
    */
   struct TALER_AmountSet total_exchange_limits;
 
 };
 
 
 /**
  * Information we keep per order we are processing.
  */
 struct OrderContext
 {
   /**
    * Information set in the #ORDER_PHASE_PARSE_REQUEST phase.
    */
   struct
   {
     /**
      * Order field of the request
      */
     json_t *order;
 
     /**
      * Set to how long refunds will be allowed.
      */
     struct GNUNET_TIME_Relative refund_delay;
 
     /**
      * RFC8905 payment target type to find a matching merchant account
      */
     const char *payment_target;
 
     /**
      * Shared key to use with @e pos_algorithm.
      */
     char *pos_key;
 
     /**
      * Selected algorithm (by template) when we are to
      * generate an OTP code for payment confirmation.
      */
     enum TALER_MerchantConfirmationAlgorithm pos_algorithm;
 
     /**
      * Hash of the POST request data, used to detect
      * idempotent requests.
      */
     struct TALER_MerchantPostDataHashP h_post_data;
 
     /**
      * Length of the @e inventory_products array.
      */
     unsigned int inventory_products_length;
 
     /**
      * Specifies that some products are to be included in the
      * order from the inventory. For these inventory management
      * is performed (so the products must be in stock).
      */
     struct InventoryProduct *inventory_products;
 
     /**
      * Length of the @e uuids array.
      */
     unsigned int uuids_length;
 
     /**
      * array of UUIDs used to reserve products from @a inventory_products.
      */
     struct GNUNET_Uuid *uuids;
 
     /**
      * Claim token for the request.
      */
     struct TALER_ClaimTokenP claim_token;
 
     /**
      * Session ID (optional) to use for the order.
      */
     const char *session_id;
 
   } parse_request;
 
   /**
    * Information set in the #ORDER_PHASE_PARSE_ORDER phase.
    */
   struct
   {
 
     /**
      * The main order data as provided by the client.
      */
     struct TALER_MERCHANT_Order *order;
 
     /**
      * Base URL of this merchant.
      */
     char *merchant_base_url;
 
     /**
      * Wire transfer round-up interval to apply.
      */
     enum GNUNET_TIME_RounderInterval wire_deadline_rounder;
 
   } parse_order;
 
   /**
    * Information set in the #ORDER_PHASE_PARSE_CHOICES phase.
    */
   struct
   {
     /**
      * Array of possible specific contracts the wallet/customer may choose
      * from by selecting the respective index when signing the deposit
      * confirmation.
      */
     struct TALER_MERCHANT_ContractChoice *choices;
 
     /**
      * Length of the @e choices array.
      */
     unsigned int choices_len;
 
     /**
      * Array of token families referenced in the contract.
      */
     struct TALER_MERCHANT_ContractTokenFamily *token_families;
 
     /**
      * Length of the @e token_families array.
      */
     unsigned int token_families_len;
   } parse_choices;
 
   /**
    * Information set in the #ORDER_PHASE_MERGE_INVENTORY phase.
    */
   struct
   {
     /**
      * Merged array of products in the @e order.
      */
     json_t *products;
   } merge_inventory;
 
   /**
    * Information set in the #ORDER_PHASE_ADD_PAYMENT_DETAILS phase.
    */
   struct
   {
 
     /**
      * DLL of wire methods under evaluation.
      */
     struct WireMethodCandidate *wmc_head;
 
     /**
      * DLL of wire methods under evaluation.
      */
     struct WireMethodCandidate *wmc_tail;
 
     /**
      * Array of maximum amounts that appear in the contract choices
      * per currency.
      * Determines the maximum amounts that a client could pay for this
      * order and which we must thus make sure is acceptable for the
      * selected wire method/account if possible.
      */
     struct TALER_Amount *max_choice_limits;
 
     /**
      * Length of the @e max_choice_limits array.
      */
     unsigned int num_max_choice_limits;
 
     /**
      * Set to true if we may need an exchange. True if any amount is non-zero.
      */
     bool need_exchange;
 
   } add_payment_details;
 
   /**
    * Information set in the #ORDER_PHASE_SELECT_WIRE_METHOD phase.
    */
   struct
   {
 
     /**
      * Array of exchanges we find acceptable for this order and wire method.
      */
     json_t *exchanges;
 
     /**
      * Wire method (and our bank account) we have selected
      * to be included for this order.
      */
     const struct TMH_WireMethod *wm;
 
   } select_wire_method;
 
   /**
    * Information set in the #ORDER_PHASE_SET_EXCHANGES phase.
    */
   struct
   {
 
     /**
      * Forced requests to /keys to update our exchange
      * information.
      */
     struct RekeyExchange *pending_reload_head;
 
     /**
      * Forced requests to /keys to update our exchange
      * information.
      */
     struct RekeyExchange *pending_reload_tail;
 
     /**
      * How long do we wait at most until giving up on getting keys?
      */
     struct GNUNET_TIME_Absolute keys_timeout;
 
     /**
      * Task to wake us up on @e keys_timeout.
      */
     struct GNUNET_SCHEDULER_Task *wakeup_task;
 
     /**
      * Array of reasons why a particular exchange may be
      * limited or not be eligible.
      */
     json_t *exchange_rejections;
 
     /**
      * Did we previously force reloading of /keys from
      * all exchanges? Set to 'true' to prevent us from
      * doing it again (and again...).
      */
     bool forced_reload;
 
     /**
      * Did we find a working exchange?
      */
     bool exchange_ok;
 
     /**
      * Did we find an exchange that justifies
      * reloading keys?
      */
     bool promising_exchange;
 
     /**
      * Set to true once we have attempted to load exchanges
      * for the first time.
      */
     bool exchanges_tried;
 
     /**
      * Details depending on the contract version.
      */
     union
     {
 
       /**
        * Details for contract v0.
        */
       struct
       {
         /**
          * Maximum fee for @e order based on STEFAN curves.
          * Used to set @e max_fee if not provided as part of
          * @e order.
          */
         struct TALER_Amount max_stefan_fee;
 
       } v0;
 
       /**
        * Details for contract v1.
        */
       struct
       {
         /**
          * Maximum fee for @e order based on STEFAN curves by
          * contract choice.
          * Used to set @e max_fee if not provided as part of
          * @e order.
          */
         struct TALER_Amount *max_stefan_fees;
 
       } v1;
 
     } details;
 
   } set_exchanges;
 
   /**
    * Information set in the #ORDER_PHASE_SET_MAX_FEE phase.
    */
   struct
   {
 
     /**
      * Details depending on the contract version.
      */
     union
     {
 
       /**
        * Details for contract v0.
        */
       struct
       {
         /**
          * Maximum fee
          */
         struct TALER_Amount max_fee;
       } v0;
 
       /**
        * Details for contract v1.
        */
       struct
       {
         /**
          * Maximum fees by contract choice.
          */
         struct TALER_Amount *max_fees;
 
       } v1;
 
     } details;
   } set_max_fee;
 
   /**
    * Information set in the #ORDER_PHASE_EXECUTE_ORDER phase.
    */
   struct
   {
     /**
      * Which product (by offset) is out of stock, UINT_MAX if all were in-stock.
      */
     unsigned int out_of_stock_index;
 
     /**
      * Set to a previous claim token *if* @e idempotent
      * is also true.
      */
     struct TALER_ClaimTokenP token;
 
     /**
      * Set to true if the order was idempotent and there
      * was an equivalent one before.
      */
     bool idempotent;
 
     /**
      * Set to true if the order is in conflict with a
      * previous order with the same order ID.
      */
     bool conflict;
   } execute_order;
 
   struct
   {
     /**
      * Contract terms to store in the database.
      */
     json_t *contract;
   } serialize_order;
 
   /**
    * Connection of the request.
    */
   struct MHD_Connection *connection;
 
   /**
    * Kept in a DLL while suspended.
    */
   struct OrderContext *next;
 
   /**
    * Kept in a DLL while suspended.
    */
   struct OrderContext *prev;
 
   /**
    * Handler context for the request.
    */
   struct TMH_HandlerContext *hc;
 
   /**
    * #GNUNET_YES if suspended.
    */
   enum GNUNET_GenericReturnValue suspended;
 
   /**
    * Current phase of setting up the order.
    */
   enum
   {
     ORDER_PHASE_PARSE_REQUEST,
     ORDER_PHASE_PARSE_ORDER,
     ORDER_PHASE_PARSE_CHOICES,
     ORDER_PHASE_MERGE_INVENTORY,
     ORDER_PHASE_ADD_PAYMENT_DETAILS,
     ORDER_PHASE_SET_EXCHANGES,
     ORDER_PHASE_SELECT_WIRE_METHOD,
     ORDER_PHASE_SET_MAX_FEE,
     ORDER_PHASE_SERIALIZE_ORDER,
     ORDER_PHASE_SALT_FORGETTABLE,
     ORDER_PHASE_CHECK_CONTRACT,
     ORDER_PHASE_EXECUTE_ORDER,
 
     /**
      * Processing is done, we should return #MHD_YES.
      */
     ORDER_PHASE_FINISHED_MHD_YES,
 
     /**
      * Processing is done, we should return #MHD_NO.
      */
     ORDER_PHASE_FINISHED_MHD_NO
   } phase;
 
 
 };
 
 
 /**
  * Kept in a DLL while suspended.
  */
 static struct OrderContext *oc_head;
 
 /**
  * Kept in a DLL while suspended.
  */
 static struct OrderContext *oc_tail;
 
 
 void
 TMH_force_orders_resume ()
 {
   struct OrderContext *oc;
 
   while (NULL != (oc = oc_head))
   {
     GNUNET_CONTAINER_DLL_remove (oc_head,
                                  oc_tail,
                                  oc);
     oc->suspended = GNUNET_SYSERR;
     MHD_resume_connection (oc->connection);
   }
 }
 
 
 /**
  * Update the phase of @a oc based on @a mret.
  *
  * @param[in,out] oc order to update phase for
  * @param mret #MHD_NO to close with #MHD_NO
  *             #MHD_YES to close with #MHD_YES
  */
 static void
 finalize_order (struct OrderContext *oc,
                 enum MHD_Result mret)
 {
   oc->phase = (MHD_YES == mret)
     ? ORDER_PHASE_FINISHED_MHD_YES
     : ORDER_PHASE_FINISHED_MHD_NO;
 }
 
 
 /**
  * Update the phase of @a oc based on @a ret.
  *
  * @param[in,out] oc order to update phase for
  * @param ret #GNUNET_SYSERR to close with #MHD_NO
  *            #GNUNET_NO to close with #MHD_YES
  *            #GNUNET_OK is not allowed!
  */
 static void
 finalize_order2 (struct OrderContext *oc,
                  enum GNUNET_GenericReturnValue ret)
 {
   GNUNET_assert (GNUNET_OK != ret);
   oc->phase = (GNUNET_NO == ret)
     ? ORDER_PHASE_FINISHED_MHD_YES
     : ORDER_PHASE_FINISHED_MHD_NO;
 }
 
 
 /**
  * Generate an error response for @a oc.
  *
  * @param[in,out] oc order context to respond to
  * @param http_status HTTP status code to set
  * @param ec error code to set
  * @param detail error message detail to set
  */
 static void
 reply_with_error (struct OrderContext *oc,
                   unsigned int http_status,
                   enum TALER_ErrorCode ec,
                   const char *detail)
 {
   enum MHD_Result mret;
 
   mret = TALER_MHD_reply_with_error (oc->connection,
                                      http_status,
                                      ec,
                                      detail);
   finalize_order (oc,
                   mret);
 }
 
 
 /**
  * Clean up memory used by @a wmc.
  *
  * @param[in,out] oc order context the WMC is part of
  * @param[in] wmc wire method candidate to free
  */
 static void
 free_wmc (struct OrderContext *oc,
           struct WireMethodCandidate *wmc)
 {
   GNUNET_CONTAINER_DLL_remove (oc->add_payment_details.wmc_head,
                                oc->add_payment_details.wmc_tail,
                                wmc);
   TALER_amount_set_free (&wmc->total_exchange_limits);
   json_decref (wmc->exchanges);
   GNUNET_free (wmc);
 }
 
 
 /**
  * Clean up memory used by @a cls.
  *
  * @param[in] cls the `struct OrderContext` to clean up
  */
 static void
 clean_order (void *cls)
 {
   struct OrderContext *oc = cls;
   struct RekeyExchange *rx;
 
   while (NULL != oc->add_payment_details.wmc_head)
     free_wmc (oc,
               oc->add_payment_details.wmc_head);
   while (NULL != (rx = oc->set_exchanges.pending_reload_head))
   {
     GNUNET_CONTAINER_DLL_remove (oc->set_exchanges.pending_reload_head,
                                  oc->set_exchanges.pending_reload_tail,
                                  rx);
     TMH_EXCHANGES_keys4exchange_cancel (rx->fo);
     GNUNET_free (rx->url);
     GNUNET_free (rx);
   }
   GNUNET_array_grow (oc->add_payment_details.max_choice_limits,
                      oc->add_payment_details.num_max_choice_limits,
                      0);
   if (NULL != oc->set_exchanges.wakeup_task)
   {
     GNUNET_SCHEDULER_cancel (oc->set_exchanges.wakeup_task);
     oc->set_exchanges.wakeup_task = NULL;
   }
   if (NULL != oc->select_wire_method.exchanges)
   {
     json_decref (oc->select_wire_method.exchanges);
     oc->select_wire_method.exchanges = NULL;
   }
   if (NULL != oc->set_exchanges.exchange_rejections)
   {
     json_decref (oc->set_exchanges.exchange_rejections);
     oc->set_exchanges.exchange_rejections = NULL;
   }
   if (NULL != oc->parse_order.order)
   {
     switch (oc->parse_order.order->base->version)
     {
     case TALER_MERCHANT_CONTRACT_VERSION_0:
       break;
     case TALER_MERCHANT_CONTRACT_VERSION_1:
       GNUNET_free (oc->set_max_fee.details.v1.max_fees);
       GNUNET_free (oc->set_exchanges.details.v1.max_stefan_fees);
       break;
     }
     TALER_MERCHANT_order_free (oc->parse_order.order);
     oc->parse_order.order = NULL;
     GNUNET_free (oc->parse_order.merchant_base_url);
   }
   if (NULL != oc->merge_inventory.products)
   {
     json_decref (oc->merge_inventory.products);
     oc->merge_inventory.products = NULL;
   }
   for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
   {
     TALER_MERCHANT_contract_choice_free (&oc->parse_choices.choices[i]);
   }
   GNUNET_array_grow (oc->parse_choices.choices,
                      oc->parse_choices.choices_len,
                      0);
   for (unsigned int i = 0; i<oc->parse_choices.token_families_len; i++)
   {
     TALER_MERCHANT_contract_token_family_free (
       &oc->parse_choices.token_families[i]);
   }
   GNUNET_array_grow (oc->parse_choices.token_families,
                      oc->parse_choices.token_families_len,
                      0);
   GNUNET_array_grow (oc->parse_request.inventory_products,
                      oc->parse_request.inventory_products_length,
                      0);
   GNUNET_array_grow (oc->parse_request.uuids,
                      oc->parse_request.uuids_length,
                      0);
   GNUNET_free (oc->parse_request.pos_key);
   json_decref (oc->parse_request.order);
   json_decref (oc->serialize_order.contract);
   GNUNET_free (oc);
 }
 
 
 /* ***************** ORDER_PHASE_EXECUTE_ORDER **************** */
 
 /**
  * Compute the quantity (integer and fractional parts) of a product that is
  * actually available for a new order.  This excludes units already sold,
  * lost, or currently reserved by locks (shopping carts and unpaid orders).
  *
  * @param pd product details with current totals/sold/lost/locked
  * @param[out] available_value remaining whole units (normalized, non-negative)
  * @param[out] available_frac remaining fractional units (0..TALER_MERCHANT_UNIT_FRAC_BASE-1)
  */
 static void
 compute_available_quantity (
   const struct TALER_MERCHANTDB_ProductDetails *pd,
   uint64_t *available_value,
   uint32_t *available_frac)
 {
   int64_t value;
   int64_t frac;
 
   GNUNET_assert (NULL != available_value);
   GNUNET_assert (NULL != available_frac);
 
   if ( (INT64_MAX == pd->total_stock) &&
        (INT32_MAX == pd->total_stock_frac) )
   {
     *available_value = pd->total_stock;
     *available_frac = pd->total_stock_frac;
     return;
   }
 
   value = (int64_t) pd->total_stock
           - (int64_t) pd->total_sold
           - (int64_t) pd->total_lost
           - (int64_t) pd->total_locked;
   frac = (int64_t) pd->total_stock_frac
          - (int64_t) pd->total_sold_frac
          - (int64_t) pd->total_lost_frac
          - (int64_t) pd->total_locked_frac;
 
   if (frac < 0)
   {
     int64_t borrow = ((-frac) + TALER_MERCHANT_UNIT_FRAC_BASE - 1)
                      / TALER_MERCHANT_UNIT_FRAC_BASE;
 
     value -= borrow;
     frac += borrow * (int64_t) TALER_MERCHANT_UNIT_FRAC_BASE;
   }
   else if (frac >= TALER_MERCHANT_UNIT_FRAC_BASE)
   {
     int64_t carry = frac / TALER_MERCHANT_UNIT_FRAC_BASE;
 
     value += carry;
     frac -= carry * (int64_t) TALER_MERCHANT_UNIT_FRAC_BASE;
   }
 
   if (value < 0)
   {
     GNUNET_break (0);
     value = 0;
     frac = 0;
   }
 
   *available_value = (uint64_t) value;
   *available_frac = (uint32_t) frac;
 }
 
 
 /**
  * Execute the database transaction to setup the order.
  *
  * @param[in,out] oc order context
  * @return transaction status, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if @a uuids were insufficient to reserve required inventory
  */
 static enum GNUNET_DB_QueryStatus
 execute_transaction (struct OrderContext *oc)
 {
   enum GNUNET_DB_QueryStatus qs;
   struct GNUNET_TIME_Timestamp timestamp;
   uint64_t order_serial;
 
   if (GNUNET_OK !=
       TALER_MERCHANTDB_start (TMH_db,
                               "insert_order"))
   {
     GNUNET_break (0);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
 
   /* Test if we already have an order with this id */
   {
     json_t *contract_terms;
     struct TALER_MerchantPostDataHashP orig_post;
 
     qs = TALER_MERCHANTDB_get_order (TMH_db,
                                      oc->hc->instance->settings.id,
                                      oc->parse_order.order->order_id,
                                      &oc->execute_order.token,
                                      &orig_post,
                                      &contract_terms);
     /* If yes, check for idempotency */
     if (0 > qs)
     {
       GNUNET_break (0);
       TALER_MERCHANTDB_rollback (TMH_db);
       return qs;
     }
     if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
     {
       TALER_MERCHANTDB_rollback (TMH_db);
       json_decref (contract_terms);
       /* Comparing the contract terms is sufficient because all the other
          params get added to it at some point. */
       if (0 == GNUNET_memcmp (&orig_post,
                               &oc->parse_request.h_post_data))
       {
         GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                     "Order creation idempotent\n");
         oc->execute_order.idempotent = true;
         return qs;
       }
       GNUNET_break_op (0);
       oc->execute_order.conflict = true;
       return qs;
     }
   }
 
   /* Setup order */
   qs = TALER_MERCHANTDB_insert_order (TMH_db,
                                       oc->hc->instance->settings.id,
                                       oc->parse_order.order->order_id,
                                       oc->parse_request.session_id,
                                       &oc->parse_request.h_post_data,
                                       oc->parse_order.order->pay_deadline,
                                       &oc->parse_request.claim_token,
                                       oc->serialize_order.contract, /* called 'contract terms' at database. */
                                       oc->parse_request.pos_key,
                                       oc->parse_request.pos_algorithm);
   if (qs <= 0)
   {
     /* qs == 0: probably instance does not exist (anymore) */
     TALER_MERCHANTDB_rollback (TMH_db);
     return qs;
   }
   /* Migrate locks from UUIDs to new order: first release old locks */
   for (unsigned int i = 0; i<oc->parse_request.uuids_length; i++)
   {
     qs = TALER_MERCHANTDB_delete_inventory_lock (TMH_db,
                                                  &oc->parse_request.uuids[i]);
     if (qs < 0)
     {
       TALER_MERCHANTDB_rollback (TMH_db);
       return qs;
     }
     /* qs == 0 is OK here, that just means we did not HAVE any lock under this
        UUID */
   }
   /* Migrate locks from UUIDs to new order: acquire new locks
      (note: this can basically ONLY fail on serializability OR
      because the UUID locks were insufficient for the desired
      quantities). */
   for (unsigned int i = 0; i<oc->parse_request.inventory_products_length; i++)
   {
     qs = TALER_MERCHANTDB_insert_order_lock (
       TMH_db,
       oc->hc->instance->settings.id,
       oc->parse_order.order->order_id,
       oc->parse_request.inventory_products[i].product_id,
       oc->parse_request.inventory_products[i].quantity,
       oc->parse_request.inventory_products[i].quantity_frac);
     if (qs < 0)
     {
       TALER_MERCHANTDB_rollback (TMH_db);
       return qs;
     }
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
     {
       /* qs == 0: lock acquisition failed due to insufficient stocks */
       TALER_MERCHANTDB_rollback (TMH_db);
       oc->execute_order.out_of_stock_index = i; /* indicate which product is causing the issue */
       return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
     }
   }
   oc->execute_order.out_of_stock_index = UINT_MAX;
 
   /* Get the order serial and timestamp for the order we just created to
      update long-poll clients. */
   qs = TALER_MERCHANTDB_get_order_summary (
     TMH_db,
     oc->hc->instance->settings.id,
     oc->parse_order.order->order_id,
     &timestamp,
     &order_serial);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
   {
     TALER_MERCHANTDB_rollback (TMH_db);
     return qs;
   }
 
   {
     json_t *jhook;
 
     jhook = GNUNET_JSON_PACK (
       GNUNET_JSON_pack_string ("order_id",
                                oc->parse_order.order->order_id),
       GNUNET_JSON_pack_object_incref ("contract",
                                       oc->serialize_order.contract),
       GNUNET_JSON_pack_string ("instance_id",
                                oc->hc->instance->settings.id)
       );
     GNUNET_assert (NULL != jhook);
     qs = TMH_trigger_webhook (oc->hc->instance->settings.id,
                               "order_created",
                               jhook);
     json_decref (jhook);
     if (0 > qs)
     {
       TALER_MERCHANTDB_rollback (TMH_db);
       if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
         return qs;
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_STORE_FAILED,
                         "failed to trigger webhooks");
       return qs;
     }
   }
 
   TMH_notify_order_change (oc->hc->instance,
                            TMH_OSF_NONE,
                            timestamp,
                            order_serial);
   /* finally, commit transaction (note: if it fails, we ALSO re-acquire
      the UUID locks, which is exactly what we want) */
   qs = TALER_MERCHANTDB_commit (TMH_db);
   if (0 > qs)
     return qs;
   return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;   /* 1 == success! */
 }
 
 
 /**
  * The request was successful, generate the #MHD_HTTP_OK response.
  *
  * @param[in,out] oc context to update
  * @param claim_token claim token to use, NULL if none
  */
 static void
 yield_success_response (struct OrderContext *oc,
                         const struct TALER_ClaimTokenP *claim_token)
 {
   enum MHD_Result ret;
 
   ret = TALER_MHD_REPLY_JSON_PACK (
     oc->connection,
     MHD_HTTP_OK,
     GNUNET_JSON_pack_string ("order_id",
                              oc->parse_order.order->order_id),
     GNUNET_JSON_pack_timestamp ("pay_deadline",
                                 oc->parse_order.order->pay_deadline),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_data_auto (
         "token",
         claim_token)));
   finalize_order (oc,
                   ret);
 }
 
 
 /**
  * Transform an order into a proposal and store it in the
  * database. Write the resulting proposal or an error message
  * of a MHD connection.
  *
  * @param[in,out] oc order context
  */
 static void
 phase_execute_order (struct OrderContext *oc)
 {
   const struct TALER_MERCHANTDB_InstanceSettings *settings =
     &oc->hc->instance->settings;
   enum GNUNET_DB_QueryStatus qs;
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Executing database transaction to create order '%s' for instance '%s'\n",
               oc->parse_order.order->order_id,
               settings->id);
   for (unsigned int i = 0; i<MAX_RETRIES; i++)
   {
     TALER_MERCHANTDB_preflight (TMH_db);
     qs = execute_transaction (oc);
     if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
       break;
   }
   if (0 >= qs)
   {
     /* Special report if retries insufficient */
     if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
     {
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_SOFT_FAILURE,
                         NULL);
       return;
     }
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
     {
       /* should be: contract (!) with same order ID
          already exists */
       reply_with_error (
         oc,
         MHD_HTTP_CONFLICT,
         TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ALREADY_EXISTS,
         oc->parse_order.order->order_id);
       return;
     }
     /* Other hard transaction error (disk full, etc.) */
     GNUNET_break (0);
     reply_with_error (
       oc,
       MHD_HTTP_INTERNAL_SERVER_ERROR,
       TALER_EC_GENERIC_DB_COMMIT_FAILED,
       NULL);
     return;
   }
 
   /* DB transaction succeeded, check for idempotent */
   if (oc->execute_order.idempotent)
   {
     yield_success_response (oc,
                             GNUNET_is_zero (&oc->execute_order.token)
                             ? NULL
                             : &oc->execute_order.token);
     return;
   }
   if (oc->execute_order.conflict)
   {
     reply_with_error (
       oc,
       MHD_HTTP_CONFLICT,
       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ALREADY_EXISTS,
       oc->parse_order.order->order_id);
     return;
   }
 
   /* DB transaction succeeded, check for out-of-stock */
   if (oc->execute_order.out_of_stock_index < UINT_MAX)
   {
     /* We had a product that has insufficient quantities,
        generate the details for the response. */
     struct TALER_MERCHANTDB_ProductDetails pd;
     enum MHD_Result ret;
     const struct InventoryProduct *ip;
     size_t num_categories = 0;
     uint64_t *categories = NULL;
     uint64_t available_quantity;
     uint32_t available_quantity_frac;
     char requested_quantity_buf[64];
     char available_quantity_buf[64];
 
     ip = &oc->parse_request.inventory_products[
       oc->execute_order.out_of_stock_index];
     memset (&pd,
             0,
             sizeof (pd));
     qs = TALER_MERCHANTDB_get_product (
       TMH_db,
       oc->hc->instance->settings.id,
       ip->product_id,
       &pd,
       &num_categories,
       &categories);
     switch (qs)
     {
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
       GNUNET_free (categories);
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Order creation failed: product out of stock\n");
 
       compute_available_quantity (&pd,
                                   &available_quantity,
                                   &available_quantity_frac);
       TALER_MERCHANT_vk_format_fractional_string (
         TALER_MERCHANT_VK_QUANTITY,
         ip->quantity,
         ip->quantity_frac,
         sizeof (requested_quantity_buf),
         requested_quantity_buf);
       TALER_MERCHANT_vk_format_fractional_string (
         TALER_MERCHANT_VK_QUANTITY,
         available_quantity,
         available_quantity_frac,
         sizeof (available_quantity_buf),
         available_quantity_buf);
       ret = TALER_MHD_REPLY_JSON_PACK (
         oc->connection,
         MHD_HTTP_GONE,
         GNUNET_JSON_pack_string (
           "product_id",
           ip->product_id),
         GNUNET_JSON_pack_uint64 (
           "requested_quantity",
           ip->quantity),
         GNUNET_JSON_pack_string (
           "unit_requested_quantity",
           requested_quantity_buf),
         GNUNET_JSON_pack_uint64 (
           "available_quantity",
           available_quantity),
         GNUNET_JSON_pack_string (
           "unit_available_quantity",
           available_quantity_buf),
         GNUNET_JSON_pack_allow_null (
           GNUNET_JSON_pack_timestamp (
             "restock_expected",
             pd.next_restock)));
       TALER_MERCHANTDB_product_details_free (&pd);
       finalize_order (oc,
                       ret);
       return;
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Order creation failed: unknown product out of stock\n");
       finalize_order (oc,
                       TALER_MHD_REPLY_JSON_PACK (
                         oc->connection,
                         MHD_HTTP_GONE,
                         GNUNET_JSON_pack_string (
                           "product_id",
                           ip->product_id),
                         GNUNET_JSON_pack_uint64 (
                           "requested_quantity",
                           ip->quantity),
                         GNUNET_JSON_pack_uint64 (
                           "available_quantity",
                           0)));
       return;
     case GNUNET_DB_STATUS_SOFT_ERROR:
       GNUNET_break (0);
       reply_with_error (
         oc,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
         TALER_EC_GENERIC_DB_SOFT_FAILURE,
         NULL);
       return;
     case GNUNET_DB_STATUS_HARD_ERROR:
       GNUNET_break (0);
       reply_with_error (
         oc,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
         TALER_EC_GENERIC_DB_FETCH_FAILED,
         NULL);
       return;
     }
     GNUNET_break (0);
     oc->phase = ORDER_PHASE_FINISHED_MHD_NO;
     return;
   } /* end 'out of stock' case */
 
   /* Everything in-stock, generate positive response */
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Order creation succeeded\n");
   yield_success_response (oc,
                           GNUNET_is_zero (&oc->parse_request.claim_token)
                           ? NULL
                           : &oc->parse_request.claim_token);
 }
 
 
 /* ***************** ORDER_PHASE_CHECK_CONTRACT **************** */
 
 
 /**
  * Check that the contract is now well-formed. Upon success, continue
  * processing with execute_order().
  *
  * @param[in,out] oc order context
  */
 static void
 phase_check_contract (struct OrderContext *oc)
 {
   struct TALER_PrivateContractHashP h_control;
 
   switch (TALER_JSON_contract_hash (oc->serialize_order.contract,
                                     &h_control))
   {
   case GNUNET_SYSERR:
     GNUNET_break (0);
     reply_with_error (
       oc,
       MHD_HTTP_INTERNAL_SERVER_ERROR,
       TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
       "could not compute hash of serialized order");
     return;
   case GNUNET_NO:
     GNUNET_break_op (0);
     reply_with_error (
       oc,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
       "order contained unallowed values");
     return;
   case GNUNET_OK:
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Contract hash is %s\n",
                 GNUNET_h2s (&h_control.hash));
     oc->phase++;
     return;
   }
   GNUNET_assert (0);
 }
 
 
 /* ***************** ORDER_PHASE_SALT_FORGETTABLE **************** */
 
 
 /**
  * Modify the final contract terms adding salts for
  * items that are forgettable.
  *
  * @param[in,out] oc order context
  */
 static void
 phase_salt_forgettable (struct OrderContext *oc)
 {
   if (GNUNET_OK !=
       TALER_JSON_contract_seed_forgettable (oc->parse_request.order,
                                             oc->serialize_order.contract))
   {
     GNUNET_break_op (0);
     reply_with_error (
       oc,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_GENERIC_JSON_INVALID,
       "could not compute hash of order due to bogus forgettable fields");
     return;
   }
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_SERIALIZE_ORDER **************** */
 
 /**
  * Get rounded time interval. @a start is calculated by rounding
  * @a ts down to the nearest multiple of @a precision.
  *
  * @param precision rounding precision.
  *        year, month, day, hour, minute are supported.
  * @param ts timestamp to round
  * @param[out] start start of the interval
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static enum GNUNET_GenericReturnValue
 get_rounded_time_interval_down (struct GNUNET_TIME_Relative precision,
                                 struct GNUNET_TIME_Timestamp ts,
                                 struct GNUNET_TIME_Timestamp *start)
 {
   enum GNUNET_TIME_RounderInterval ri;
 
   ri = GNUNET_TIME_relative_to_round_interval (precision);
   if ( (GNUNET_TIME_RI_NONE == ri) &&
        (! GNUNET_TIME_relative_is_zero (precision)) )
   {
     *start = ts;
     return GNUNET_SYSERR;
   }
   *start = GNUNET_TIME_absolute_to_timestamp (
     GNUNET_TIME_round_down (ts.abs_time,
                             ri));
   return GNUNET_OK;
 }
 
 
 /**
  * Get rounded time interval. @a start is calculated by rounding
  * @a ts up to the nearest multiple of @a precision.
  *
  * @param precision rounding precision.
  *        year, month, day, hour, minute are supported.
  * @param ts timestamp to round
  * @param[out] start start of the interval
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static enum GNUNET_GenericReturnValue
 get_rounded_time_interval_up (struct GNUNET_TIME_Relative precision,
                               struct GNUNET_TIME_Timestamp ts,
                               struct GNUNET_TIME_Timestamp *start)
 {
   enum GNUNET_TIME_RounderInterval ri;
 
   ri = GNUNET_TIME_relative_to_round_interval (precision);
   if ( (GNUNET_TIME_RI_NONE == ri) &&
        (! GNUNET_TIME_relative_is_zero (precision)) )
   {
     *start = ts;
     return GNUNET_SYSERR;
   }
   *start = GNUNET_TIME_absolute_to_timestamp (
     GNUNET_TIME_round_up (ts.abs_time,
                           ri));
   return GNUNET_OK;
 }
 
 
 /**
  * Find the family entry for the family of the given @a slug
  * in @a oc.
  *
  * @param[in] oc order context to search
  * @param slug slug to search for
  * @return NULL if @a slug was not found
  */
 static struct TALER_MERCHANT_ContractTokenFamily *
 find_family (const struct OrderContext *oc,
              const char *slug)
 {
   for (unsigned int i = 0; i<oc->parse_choices.token_families_len; i++)
   {
     if (0 == strcmp (oc->parse_choices.token_families[i].slug,
                      slug))
     {
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Token family %s already in order\n",
                   slug);
       return &oc->parse_choices.token_families[i];
     }
   }
   return NULL;
 }
 
 
 /**
  * Function called with each applicable family key that should
  * be added to the respective token family of the order.
  *
  * @param cls a `struct OrderContext *` to expand
  * @param tfkd token family key details to add to the contract
  */
 static void
 add_family_key (void *cls,
                 const struct TALER_MERCHANTDB_TokenFamilyKeyDetails *tfkd)
 {
   struct OrderContext *oc = cls;
   const struct TALER_MERCHANTDB_TokenFamilyDetails *tf = &tfkd->token_family;
   struct TALER_MERCHANT_ContractTokenFamily *family;
 
   family = find_family (oc,
                         tf->slug);
   if (NULL == family)
   {
     /* Family not yet in our contract terms, create new entry */
     struct TALER_MERCHANT_ContractTokenFamily new_family = {
       .slug = GNUNET_strdup (tf->slug),
       .name = GNUNET_strdup (tf->name),
       .description = GNUNET_strdup (tf->description),
       .description_i18n = json_incref (tf->description_i18n),
     };
 
     switch (tf->kind)
     {
     case TALER_MERCHANTDB_TFK_Subscription:
       {
         json_t *tdomains = json_object_get (tf->extra_data,
                                             "trusted_domains");
         json_t *dom;
         size_t i;
 
         new_family.kind = TALER_MERCHANT_CONTRACT_TOKEN_KIND_SUBSCRIPTION;
         new_family.critical = true;
         new_family.details.subscription.trusted_domains_len
           = json_array_size (tdomains);
         GNUNET_assert (new_family.details.subscription.trusted_domains_len
                        < UINT_MAX);
         new_family.details.subscription.trusted_domains
           = GNUNET_new_array (
               new_family.details.subscription.trusted_domains_len,
               char *);
         json_array_foreach (tdomains, i, dom)
         {
           const char *val;
 
           val = json_string_value (dom);
           GNUNET_break (NULL != val);
           if (NULL != val)
             new_family.details.subscription.trusted_domains[i]
               = GNUNET_strdup (val);
         }
         break;
       }
     case TALER_MERCHANTDB_TFK_Discount:
       {
         json_t *edomains = json_object_get (tf->extra_data,
                                             "expected_domains");
         json_t *dom;
         size_t i;
 
         new_family.kind = TALER_MERCHANT_CONTRACT_TOKEN_KIND_DISCOUNT;
         new_family.critical = false;
         new_family.details.discount.expected_domains_len
           = json_array_size (edomains);
         GNUNET_assert (new_family.details.discount.expected_domains_len
                        < UINT_MAX);
         new_family.details.discount.expected_domains
           = GNUNET_new_array (
               new_family.details.discount.expected_domains_len,
               char *);
         json_array_foreach (edomains, i, dom)
         {
           const char *val;
 
           val = json_string_value (dom);
           GNUNET_break (NULL != val);
           if (NULL != val)
             new_family.details.discount.expected_domains[i]
               = GNUNET_strdup (val);
         }
         break;
       }
     }
     GNUNET_array_append (oc->parse_choices.token_families,
                          oc->parse_choices.token_families_len,
                          new_family);
     family = &oc->parse_choices.token_families[
       oc->parse_choices.token_families_len - 1];
   }
   if (NULL == tfkd->pub.public_key)
     return;
   for (unsigned int i = 0; i<family->keys_len; i++)
   {
     /* Note: cmp() returns 0 when the keys are EQUAL (memcmp-style). */
     if (0 == TALER_token_issue_pub_cmp (&family->keys[i].pub,
                                         &tfkd->pub))
     {
       /* A matching key is already in the list. */
       return;
     }
   }
 
   {
     struct TALER_MERCHANT_ContractTokenFamilyKey key;
 
     TALER_token_issue_pub_copy (&key.pub,
                                 &tfkd->pub);
     key.valid_after = tfkd->signature_validity_start;
     key.valid_before = tfkd->signature_validity_end;
     GNUNET_array_append (family->keys,
                          family->keys_len,
                          key);
   }
 }
 
 
 /**
  * Check if the token family with the given @a slug is already present in the
  * list of token families for this order. If not, fetch its details and add it
  * to the list.
  *
  * @param[in,out] oc order context
  * @param slug slug of the token family
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static enum GNUNET_GenericReturnValue
 add_input_token_family (struct OrderContext *oc,
                         const char *slug)
 {
   struct GNUNET_TIME_Timestamp now = GNUNET_TIME_timestamp_get ();
   struct GNUNET_TIME_Timestamp end = oc->parse_order.order->pay_deadline;
   enum GNUNET_DB_QueryStatus qs;
   enum TALER_ErrorCode ec = TALER_EC_INVALID; /* make compiler happy */
   unsigned int http_status = 0; /* make compiler happy */
 
   qs = TALER_MERCHANTDB_iterate_token_family_keys (
     TMH_db,
     oc->hc->instance->settings.id,
     slug,
     now,
     end,
     &add_family_key,
     oc);
   switch (qs)
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
     GNUNET_break (0);
     http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
     ec = TALER_EC_GENERIC_DB_FETCH_FAILED;
     break;
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
     ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
     break;
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Input token family slug %s unknown\n",
                 slug);
     http_status = MHD_HTTP_NOT_FOUND;
     ec = TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_TOKEN_FAMILY_SLUG_UNKNOWN;
     break;
   default: /* one or more results are all OK */
     return GNUNET_OK;
   }
   reply_with_error (oc,
                     http_status,
                     ec,
                     slug);
   return GNUNET_SYSERR;
 }
 
 
 /**
  * Find the index of a key in the @a family that is valid at
  * the time @a valid_at.
  *
  * @param family to search
  * @param valid_at time when the key must be valid
  * @param[out] key_index index to initialize
  * @return #GNUNET_OK if a matching key was found
  */
 static enum GNUNET_GenericReturnValue
 find_key_index (struct TALER_MERCHANT_ContractTokenFamily *family,
                 struct GNUNET_TIME_Timestamp valid_at,
                 unsigned int *key_index)
 {
   for (unsigned int i = 0; i<family->keys_len; i++)
   {
     if ( (GNUNET_TIME_timestamp_cmp (family->keys[i].valid_after,
                                      <=,
                                      valid_at)) &&
          (GNUNET_TIME_timestamp_cmp (family->keys[i].valid_before,
                                      >=,
                                      valid_at)) )
     {
       /* The token family and a matching key already exist. */
       *key_index = i;
       return GNUNET_OK;
     }
   }
   return GNUNET_NO;
 }
 
 
 /**
  * Create fresh key pair based on @a cipher_spec.
  *
  * @param cipher_spec which kind of key pair should we generate
  * @param[out] priv set to new private key
  * @param[out] pub set to new public key
  * @return #GNUNET_OK on success
  */
 static enum GNUNET_GenericReturnValue
 create_key (const char *cipher_spec,
             struct TALER_TokenIssuePrivateKey *priv,
             struct TALER_TokenIssuePublicKey *pub)
 {
   unsigned int len;
   char dummy;
 
   if (0 == strcmp ("cs",
                    cipher_spec))
   {
     GNUNET_CRYPTO_blind_sign_keys_create (
       &priv->private_key,
       &pub->public_key,
       GNUNET_CRYPTO_BSA_CS);
     return GNUNET_OK;
   }
   if (1 ==
       sscanf (cipher_spec,
               "rsa(%u)%c",
               &len,
               &dummy))
   {
     GNUNET_CRYPTO_blind_sign_keys_create (
       &priv->private_key,
       &pub->public_key,
       GNUNET_CRYPTO_BSA_RSA,
       len);
     return GNUNET_OK;
   }
   return GNUNET_SYSERR;
 }
 
 
 /**
  * Check if the token family with the given @a slug is already present in the
  * list of token families for this order. If not, fetch its details and add it
  * to the list. Also checks if there is a public key with that expires after
  * the payment deadline.  If a key covering @a valid_at exists but its private
  * key would be deleted before the payment deadline, the lifetime of that
  * private key is extended; only if no key covers @a valid_at at all do we
  * generate a new key pair and store it in the database.
  *
  * @param[in,out] oc order context
  * @param slug slug of the token family
  * @param valid_at time when the token returned must be valid
  * @param[out] key_index set to the index of the respective public
  *    key in the @a slug's token family keys array.
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static enum GNUNET_GenericReturnValue
 add_output_token_family (struct OrderContext *oc,
                          const char *slug,
                          struct GNUNET_TIME_Timestamp valid_at,
                          unsigned int *key_index)
 {
   struct TALER_MERCHANTDB_TokenFamilyKeyDetails key_details;
   struct TALER_MERCHANT_ContractTokenFamily *family;
   enum GNUNET_DB_QueryStatus qs;
 
   /* We are about to promise a token of this family, so the private key
      covering @a valid_at must survive until we sign at the pay deadline.  If
      an existing key covers the validity period but was minted for an order
      with an earlier pay deadline, extend its lifetime instead of minting a
      second key for the very same validity period: the key lookups below (and
      find_key_index()) would otherwise consider that key missing and we would
      end up listing two keys for one validity period in the contract terms.  */
   qs = TALER_MERCHANTDB_update_token_family_key_expiration (
     TMH_db,
     oc->hc->instance->settings.id,
     slug,
     valid_at,
     oc->parse_order.order->pay_deadline);
   switch (qs)
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
     GNUNET_break (0);
     reply_with_error (oc,
                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                       TALER_EC_GENERIC_DB_STORE_FAILED,
                       "update_token_family_key_expiration");
     return GNUNET_SYSERR;
   case GNUNET_DB_STATUS_SOFT_ERROR:
     /* Single-statement transaction shouldn't possibly cause serialization errors.
        Thus treating like a hard error. */
     GNUNET_break (0);
     reply_with_error (oc,
                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                       TALER_EC_GENERIC_DB_SOFT_FAILURE,
                       "update_token_family_key_expiration");
     return GNUNET_SYSERR;
   default:
     /* No key needed extending, or one/more were extended; either is fine. */
     break;
   }
   family = find_family (oc,
                         slug);
   if ( (NULL != family) &&
        (GNUNET_OK ==
         find_key_index (family,
                         valid_at,
                         key_index)) )
     return GNUNET_OK;
   qs = TALER_MERCHANTDB_get_token_family_key (
     TMH_db,
     oc->hc->instance->settings.id,
     slug,
     valid_at,
     oc->parse_order.order->pay_deadline,
     &key_details);
   switch (qs)
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
     GNUNET_break (0);
     reply_with_error (oc,
                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                       TALER_EC_GENERIC_DB_FETCH_FAILED,
                       "get_token_family_key");
     return GNUNET_SYSERR;
   case GNUNET_DB_STATUS_SOFT_ERROR:
     /* Single-statement transaction shouldn't possibly cause serialization errors.
        Thus treating like a hard error. */
     GNUNET_break (0);
     reply_with_error (oc,
                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                       TALER_EC_GENERIC_DB_SOFT_FAILURE,
                       "get_token_family_key");
     return GNUNET_SYSERR;
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Output token family slug %s unknown at %llu for %llu for instance %s\n",
                 slug,
                 (unsigned long long) valid_at.abs_time.abs_value_us,
                 (unsigned long long) oc->parse_order.order->pay_deadline.abs_time.abs_value_us,
                 oc->hc->instance->settings.id);
     reply_with_error (oc,
                       MHD_HTTP_NOT_FOUND,
                       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_TOKEN_FAMILY_SLUG_UNKNOWN,
                       slug);
     return GNUNET_SYSERR;
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     break;
   }
 
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Lookup of token family %s at %llu yielded %s\n",
               slug,
               (unsigned long long) valid_at.abs_time.abs_value_us,
               NULL == key_details.pub.public_key ? "no key" : "a key");
 
   /* add_family_key() must run even if the family already exists, else a
      DB-only key would never reach the in-memory family and the
      find_key_index() assertion below aborts the backend (SIGABRT). */
   add_family_key (oc,
                   &key_details);
   if (NULL == family)
   {
     family = find_family (oc,
                           slug);
     GNUNET_assert (NULL != family);
   }
   /* we don't need the full family details anymore */
   GNUNET_free (key_details.token_family.slug);
   GNUNET_free (key_details.token_family.name);
   GNUNET_free (key_details.token_family.description);
   json_decref (key_details.token_family.description_i18n);
   json_decref (key_details.token_family.extra_data);
 
   if (NULL != key_details.pub.public_key)
   {
     /* get_token_family_key must have found a matching key,
        and it must have been added. Find and use the index. */
     GNUNET_CRYPTO_blind_sign_pub_decref (key_details.pub.public_key);
     GNUNET_CRYPTO_blind_sign_priv_decref (key_details.priv.private_key);
     GNUNET_free (key_details.token_family.cipher_spec);
     GNUNET_assert (GNUNET_OK ==
                    find_key_index (family,
                                    valid_at,
                                    key_index));
     return GNUNET_OK;
   }
 
   /* No suitable key exists, create one! */
   {
     struct TALER_MERCHANT_ContractTokenFamilyKey key;
     enum GNUNET_DB_QueryStatus iqs;
     struct TALER_TokenIssuePrivateKey token_priv;
     struct GNUNET_TIME_Timestamp key_expires;
     struct GNUNET_TIME_Timestamp round_start;
 
     if (GNUNET_OK !=
         get_rounded_time_interval_down (
           key_details.token_family.validity_granularity,
           GNUNET_TIME_absolute_to_timestamp (
             GNUNET_TIME_absolute_subtract (
               valid_at.abs_time,
               key_details.token_family.start_offset)),
           &round_start))
     {
       GNUNET_break (0);
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                   "Unsupported validity granularity interval %s found in database for token family %s!\n",
                   GNUNET_TIME_relative2s (
                     key_details.token_family.validity_granularity,
                     false),
                   slug);
       GNUNET_free (key_details.token_family.cipher_spec);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                         "get_rounded_time_interval_down failed");
       return GNUNET_SYSERR;
     }
     if (GNUNET_TIME_relative_cmp (
           key_details.token_family.duration,
           <,
           GNUNET_TIME_relative_add (
             key_details.token_family.validity_granularity,
             key_details.token_family.start_offset)))
     {
       GNUNET_break (0);
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                   "Inconsistent duration %s found in database for token family %s (below validity granularity plus start_offset)!\n",
                   GNUNET_TIME_relative2s (key_details.token_family.duration,
                                           false),
                   slug);
       GNUNET_free (key_details.token_family.cipher_spec);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                         "duration, validity_granularity and start_offset inconsistent for token family");
       return GNUNET_SYSERR;
     }
     key.valid_after
       = GNUNET_TIME_timestamp_max (
           GNUNET_TIME_absolute_to_timestamp (
             GNUNET_TIME_absolute_subtract (
               round_start.abs_time,
               key_details.token_family.start_offset)),
           key_details.token_family.valid_after);
     key.valid_before
       = GNUNET_TIME_timestamp_min (
           GNUNET_TIME_absolute_to_timestamp (
             GNUNET_TIME_absolute_add (
               key.valid_after.abs_time,
               key_details.token_family.duration)),
           key_details.token_family.valid_before);
     GNUNET_assert (GNUNET_OK ==
                    get_rounded_time_interval_down (
                      key_details.token_family.validity_granularity,
                      key.valid_before,
                      &key_expires));
     /* Make sure key never expires before the payment deadline */
     key_expires = GNUNET_TIME_timestamp_max (
       oc->parse_order.order->pay_deadline,
       key_expires);
     if (GNUNET_TIME_timestamp_cmp (
           key_expires,
           ==,
           round_start))
     {
       /* valid_before does not actually end after the
          next rounded validity period would start;
          determine next rounded validity period
          start point and extend valid_before to cover
          the full validity period */
       GNUNET_assert (
         GNUNET_OK ==
         get_rounded_time_interval_up (
           key_details.token_family.validity_granularity,
           key.valid_before,
           &key_expires));
       /* This should basically always end up being key_expires */
       key.valid_before = GNUNET_TIME_timestamp_max (key.valid_before,
                                                     key_expires);
     }
     if (GNUNET_OK !=
         create_key (key_details.token_family.cipher_spec,
                     &token_priv,
                     &key.pub))
     {
       GNUNET_break (0);
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                   "Unsupported cipher family %s found in database for token family %s!\n",
                   key_details.token_family.cipher_spec,
                   slug);
       GNUNET_free (key_details.token_family.cipher_spec);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                         "invalid cipher stored in local database for token family");
       return GNUNET_SYSERR;
     }
     GNUNET_free (key_details.token_family.cipher_spec);
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Storing new key for slug %s of %s\n",
                 slug,
                 oc->hc->instance->settings.id);
     iqs = TALER_MERCHANTDB_insert_token_family_key (TMH_db,
                                                     oc->hc->instance->settings.id,
                                                     slug,
                                                     &key.pub,
                                                     &token_priv,
                                                     key_expires,
                                                     key.valid_after,
                                                     key.valid_before);
     GNUNET_CRYPTO_blind_sign_priv_decref (token_priv.private_key);
     switch (iqs)
     {
     case GNUNET_DB_STATUS_HARD_ERROR:
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_STORE_FAILED,
                         NULL);
       return GNUNET_SYSERR;
     case GNUNET_DB_STATUS_SOFT_ERROR:
       /* Single-statement transaction shouldn't possibly cause serialization errors.
          Thus treating like a hard error. */
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_SOFT_FAILURE,
                         NULL);
       return GNUNET_SYSERR;
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_STORE_FAILED,
                         NULL);
       return GNUNET_SYSERR;
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
       break;
     }
     *key_index = family->keys_len;
     GNUNET_array_append (family->keys,
                          family->keys_len,
                          key);
   }
   return GNUNET_OK;
 }
 
 
 /**
  * Build JSON array that represents all of the token families
  * in the contract.
  *
  * @param[in] oc v1-style order context
  * @return JSON array with token families for the contract
  */
 static json_t *
 output_token_families (struct OrderContext *oc)
 {
   json_t *token_families = json_object ();
 
   GNUNET_assert (NULL != token_families);
   for (unsigned int i = 0; i<oc->parse_choices.token_families_len; i++)
   {
     const struct TALER_MERCHANT_ContractTokenFamily *family
       = &oc->parse_choices.token_families[i];
     json_t *jfamily;
 
     jfamily = TALER_MERCHANT_json_from_token_family (family);
 
     GNUNET_assert (jfamily != NULL);
 
     GNUNET_assert (0 ==
                    json_object_set_new (token_families,
                                         family->slug,
                                         jfamily));
   }
   return token_families;
 }
 
 
 /**
  * Build JSON array that represents all of the contract choices
  * in the contract.
  *
  * @param[in] oc v1-style order context
  * @return JSON array with token families for the contract
  */
 static json_t *
 output_contract_choices (struct OrderContext *oc)
 {
   json_t *choices = json_array ();
 
   GNUNET_assert (NULL != choices);
   for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
   {
     oc->parse_choices.choices[i].max_fee =
       oc->set_max_fee.details.v1.max_fees[i];
     GNUNET_assert (0 == json_array_append_new (
                      choices,
                      TALER_MERCHANT_json_from_contract_choice (
                        &oc->parse_choices.choices[i])));
   }
   return choices;
 }
 
 
 /**
  * Serialize order into @a oc->serialize_order.contract,
  * ready to be stored in the database. Upon success, continue
  * processing with check_contract().
  *
  * @param[in,out] oc order context
  */
 static void
 phase_serialize_order (struct OrderContext *oc)
 {
   const struct TALER_MERCHANTDB_InstanceSettings *settings =
     &oc->hc->instance->settings;
   json_t *merchant;
 
   merchant = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_string ("name",
                              settings->name),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("website",
                                settings->website)),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("email",
                                settings->email)),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("logo",
                                settings->logo)));
   GNUNET_assert (NULL != merchant);
   {
     json_t *loca;
 
     /* Handle merchant address */
     loca = settings->address;
     if (NULL != loca)
     {
       loca = json_deep_copy (loca);
       GNUNET_assert (NULL != loca);
       GNUNET_assert (0 ==
                      json_object_set_new (merchant,
                                           "address",
                                           loca));
     }
   }
   {
     json_t *juri;
 
     /* Handle merchant jurisdiction */
     juri = settings->jurisdiction;
     if (NULL != juri)
     {
       juri = json_deep_copy (juri);
       GNUNET_assert (NULL != juri);
       GNUNET_assert (0 ==
                      json_object_set_new (merchant,
                                           "jurisdiction",
                                           juri));
     }
   }
 
   oc->serialize_order.contract = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_string (
       "order_id",
       oc->parse_order.order->order_id),
     GNUNET_JSON_pack_object_steal (
       NULL,
       TALER_MERCHANT_base_terms_serialize (oc->parse_order.order->base)),
     GNUNET_JSON_pack_array_incref (
       "products",
       oc->merge_inventory.products),
     GNUNET_JSON_pack_data_auto (
       "h_wire",
       &oc->select_wire_method.wm->h_wire),
     GNUNET_JSON_pack_string (
       "wire_method",
       oc->select_wire_method.wm->wire_method),
     GNUNET_JSON_pack_timestamp (
       "timestamp",
       oc->parse_order.order->timestamp),
     GNUNET_JSON_pack_timestamp (
       "pay_deadline",
       oc->parse_order.order->pay_deadline),
     GNUNET_JSON_pack_timestamp (
       "wire_transfer_deadline",
       oc->parse_order.order->wire_transfer_deadline),
     GNUNET_JSON_pack_string (
       "merchant_base_url",
       oc->parse_order.merchant_base_url),
     GNUNET_JSON_pack_object_steal (
       "merchant",
       merchant),
     GNUNET_JSON_pack_data_auto (
       "merchant_pub",
       &oc->hc->instance->merchant_pub),
     GNUNET_JSON_pack_array_incref (
       "exchanges",
       oc->select_wire_method.exchanges));
 
   {
     json_t *xtra;
 
     switch (oc->parse_order.order->base->version)
     {
     case TALER_MERCHANT_CONTRACT_VERSION_0:
       xtra = GNUNET_JSON_PACK (
         TALER_JSON_pack_amount ("max_fee",
                                 &oc->set_max_fee.details.v0.max_fee),
         GNUNET_JSON_pack_allow_null (
           TALER_JSON_pack_amount (
             "tip",
             oc->parse_order.order->details.v0.no_tip
                                   ? NULL
                                   : &oc->parse_order.order->details.v0.tip)),
         TALER_JSON_pack_amount (
           "amount",
           &oc->parse_order.order->details.v0.brutto));
       break;
     case TALER_MERCHANT_CONTRACT_VERSION_1:
       {
         json_t *token_families = output_token_families (oc);
         json_t *choices = output_contract_choices (oc);
 
         if ( (NULL == token_families) ||
              (NULL == choices) )
         {
           GNUNET_break (0);
           return;
         }
         xtra = GNUNET_JSON_PACK (
           GNUNET_JSON_pack_array_steal ("choices",
                                         choices),
           GNUNET_JSON_pack_object_steal ("token_families",
                                          token_families));
         break;
       }
     default:
       GNUNET_assert (0);
     }
     GNUNET_assert (0 ==
                    json_object_update (oc->serialize_order.contract,
                                        xtra));
     json_decref (xtra);
   }
 
 
   /* Pack does not work here, because it doesn't set zero-values for timestamps */
   GNUNET_assert (0 ==
                  json_object_set_new (
                    oc->serialize_order.contract,
                    "refund_deadline",
                    GNUNET_JSON_from_timestamp (
                      oc->parse_order.order->refund_deadline)));
   /* auto_refund should only be set if it is not 0 */
   if (! GNUNET_TIME_relative_is_zero (
         oc->parse_order.order->base->auto_refund))
   {
     /* Pack does not work here, because it sets zero-values for relative times */
     GNUNET_assert (0 ==
                    json_object_set_new (
                      oc->serialize_order.contract,
                      "auto_refund",
                      GNUNET_JSON_from_time_rel (
                        oc->parse_order.order->base->auto_refund)));
   }
 
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_SET_MAX_FEE **************** */
 
 
 /**
  * Set @a max_fee in @a oc based on @a max_stefan_fee value if not overridden
  * by @a client_fee.  If neither is set, set the fee to zero using currency
  * from @a brutto.
  *
  * @param[in,out] oc order context
  * @param brutto brutto amount to compute fee for
  * @param client_fee client-given fee override (or invalid)
  * @param max_stefan_fee maximum STEFAN fee of any exchange
  * @param max_fee set to the maximum stefan fee
  */
 static void
 compute_fee (struct OrderContext *oc,
              const struct TALER_Amount *brutto,
              const struct TALER_Amount *client_fee,
              const struct TALER_Amount *max_stefan_fee,
              struct TALER_Amount *max_fee)
 {
   const struct TALER_MERCHANTDB_InstanceSettings *settings
     = &oc->hc->instance->settings;
 
   if (GNUNET_OK ==
       TALER_amount_is_valid (client_fee))
   {
     *max_fee = *client_fee;
     return;
   }
   if ( (settings->use_stefan) &&
        (NULL != max_stefan_fee) &&
        (GNUNET_OK ==
         TALER_amount_is_valid (max_stefan_fee)) )
   {
     *max_fee = *max_stefan_fee;
     return;
   }
   GNUNET_assert (
     GNUNET_OK ==
     TALER_amount_set_zero (brutto->currency,
                            max_fee));
 }
 
 
 /**
  * Initialize "set_max_fee" in @a oc based on STEFAN value or client
  * preference. Upon success, continue processing in next phase.
  *
  * @param[in,out] oc order context
  */
 static void
 phase_set_max_fee (struct OrderContext *oc)
 {
   switch (oc->parse_order.order->base->version)
   {
   case TALER_MERCHANT_CONTRACT_VERSION_0:
     compute_fee (oc,
                  &oc->parse_order.order->details.v0.brutto,
                  &oc->parse_order.order->details.v0.max_fee,
                  &oc->set_exchanges.details.v0.max_stefan_fee,
                  &oc->set_max_fee.details.v0.max_fee);
     break;
   case TALER_MERCHANT_CONTRACT_VERSION_1:
     oc->set_max_fee.details.v1.max_fees
       = GNUNET_new_array (oc->parse_choices.choices_len,
                           struct TALER_Amount);
     for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
       compute_fee (oc,
                    &oc->parse_choices.choices[i].amount,
                    &oc->parse_choices.choices[i].max_fee,
                    NULL != oc->set_exchanges.details.v1.max_stefan_fees
                    ? &oc->set_exchanges.details.v1.max_stefan_fees[i]
                    : NULL,
                    &oc->set_max_fee.details.v1.max_fees[i]);
     break;
   default:
     GNUNET_break (0);
     break;
   }
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_SELECT_WIRE_METHOD **************** */
 
 /**
  * Phase to select a wire method that will be acceptable for the order.
  * If none is "perfect" (allows all choices), might jump back to the
  * previous phase to force "/keys" downloads to see if that helps.
  *
  * @param[in,out] oc order context
  */
 static void
 phase_select_wire_method (struct OrderContext *oc)
 {
   const struct TALER_Amount *ea;
   struct WireMethodCandidate *best = NULL;
   unsigned int max_choices = 0;
   unsigned int want_choices = 0;
   bool zero_amount = false;
 
   switch (oc->parse_order.order->base->version)
   {
   case TALER_MERCHANT_CONTRACT_VERSION_0:
     ea = &oc->parse_order.order->details.v0.brutto;
     if (TALER_amount_is_zero (ea))
       zero_amount = true;
     break;
   case TALER_MERCHANT_CONTRACT_VERSION_1:
     for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
     {
       ea = &oc->parse_choices.choices[i].amount;
       if (TALER_amount_is_zero (ea))
         zero_amount = true;
     }
     break;
   default:
     GNUNET_assert (0);
   }
 
   for (struct WireMethodCandidate *wmc = oc->add_payment_details.wmc_head;
        NULL != wmc;
        wmc = wmc->next)
   {
     unsigned int num_choices = 0;
 
     switch (oc->parse_order.order->base->version)
     {
     case TALER_MERCHANT_CONTRACT_VERSION_0:
       want_choices = 1;
       ea = &oc->parse_order.order->details.v0.brutto;
       if (TALER_amount_is_zero (ea) ||
           TALER_amount_set_test_above (&wmc->total_exchange_limits,
                                        ea))
         num_choices++;
       break;
     case TALER_MERCHANT_CONTRACT_VERSION_1:
       want_choices = oc->parse_choices.choices_len;
       for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
       {
         ea = &oc->parse_choices.choices[i].amount;
         if (TALER_amount_is_zero (ea) ||
             TALER_amount_set_test_above (&wmc->total_exchange_limits,
                                          ea))
           num_choices++;
       }
       break;
     default:
       GNUNET_assert (0);
     }
     if (num_choices > max_choices)
     {
       best = wmc;
       max_choices = num_choices;
     }
   }
 
   if ( (want_choices > max_choices) &&
        (oc->set_exchanges.promising_exchange) &&
        (! oc->set_exchanges.forced_reload) )
   {
     oc->set_exchanges.exchange_ok = false;
     /* Not all choices in the contract can work with these
        exchanges, try again with forcing /keys download */
     for (struct WireMethodCandidate *wmc = oc->add_payment_details.wmc_head;
          NULL != wmc;
          wmc = wmc->next)
     {
       json_array_clear (wmc->exchanges);
       TALER_amount_set_free (&wmc->total_exchange_limits);
     }
     oc->phase = ORDER_PHASE_SET_EXCHANGES;
     return;
   }
 
   if ( (NULL == best) &&
        (! zero_amount) &&
        (NULL != oc->parse_request.payment_target) )
   {
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Cannot create order: lacking suitable exchanges for payment target `%s'\n",
                 oc->parse_request.payment_target);
     reply_with_error (
       oc,
       MHD_HTTP_CONFLICT,
       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_NO_EXCHANGES_FOR_WIRE_METHOD,
       oc->parse_request.payment_target);
     return;
   }
 
   if ( (NULL == best) &&
        (! zero_amount) )
   {
     enum MHD_Result mret;
 
     /* We actually do not have ANY workable exchange(s) */
     mret = TALER_MHD_reply_json_steal (
       oc->connection,
       GNUNET_JSON_PACK (
         TALER_JSON_pack_ec (
           TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_AMOUNT_EXCEEDS_LEGAL_LIMITS),
         GNUNET_JSON_pack_allow_null (
           GNUNET_JSON_pack_array_incref (
             "exchange_rejections",
             oc->set_exchanges.exchange_rejections))),
       MHD_HTTP_UNAVAILABLE_FOR_LEGAL_REASONS);
     finalize_order (oc,
                     mret);
     return;
   }
 
   if (want_choices > max_choices)
   {
     /* Some choices are unpayable */
     GNUNET_log (
       GNUNET_ERROR_TYPE_WARNING,
       "Creating order, but some choices do not work with the selected wire method\n");
   }
   if ( (0 == json_array_size (best->exchanges)) &&
        (oc->add_payment_details.need_exchange) )
   {
     /* We did not find any reasonable exchange */
     GNUNET_log (
       GNUNET_ERROR_TYPE_WARNING,
       "Creating order, but only for choices without payment\n");
   }
 
   oc->select_wire_method.wm
     = best->wm;
   oc->select_wire_method.exchanges
     = json_incref (best->exchanges);
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_SET_EXCHANGES **************** */
 
 /**
  * Exchange `/keys` processing is done, resume handling
  * the order.
  *
  * @param[in,out] oc context to resume
  */
 static void
 resume_with_keys (struct OrderContext *oc)
 {
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Resuming order processing after /keys downloads\n");
   GNUNET_assert (GNUNET_YES == oc->suspended);
   GNUNET_CONTAINER_DLL_remove (oc_head,
                                oc_tail,
                                oc);
   oc->suspended = GNUNET_NO;
   MHD_resume_connection (oc->connection);
   TALER_MHD_daemon_trigger (); /* we resumed, kick MHD */
 }
 
 
 /**
  * Given a @a brutto amount for exchange with @a keys, set the
  * @a stefan_fee. Note that @a stefan_fee is updated to the maximum
  * of the input and the computed fee.
  *
  * @param[in,out] keys exchange keys
  * @param brutto some brutto amount the client is to pay
  * @param[in,out] stefan_fee set to STEFAN fee to be paid by the merchant
  */
 static void
 compute_stefan_fee (const struct TALER_EXCHANGE_Keys *keys,
                     const struct TALER_Amount *brutto,
                     struct TALER_Amount *stefan_fee)
 {
   struct TALER_Amount net;
 
   if (GNUNET_SYSERR !=
       TALER_EXCHANGE_keys_stefan_b2n (keys,
                                       brutto,
                                       &net))
   {
     struct TALER_Amount fee;
 
     TALER_EXCHANGE_keys_stefan_round (keys,
                                       &net);
     if (-1 == TALER_amount_cmp (brutto,
                                 &net))
     {
       /* brutto < netto! */
       /* => after rounding, there is no real difference */
       net = *brutto;
     }
     GNUNET_assert (0 <=
                    TALER_amount_subtract (&fee,
                                           brutto,
                                           &net));
     if ( (GNUNET_OK !=
           TALER_amount_is_valid (stefan_fee)) ||
          (-1 == TALER_amount_cmp (stefan_fee,
                                   &fee)) )
     {
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Updated STEFAN-based fee to %s\n",
                   TALER_amount2s (&fee));
       *stefan_fee = fee;
     }
   }
 }
 
 
 /**
  * Update MAX STEFAN fees based on @a keys.
  *
  * @param[in,out] oc order context to update
  * @param keys keys to derive STEFAN fees from
  */
 static void
 update_stefan (struct OrderContext *oc,
                const struct TALER_EXCHANGE_Keys *keys)
 {
   switch (oc->parse_order.order->base->version)
   {
   case TALER_MERCHANT_CONTRACT_VERSION_0:
     compute_stefan_fee (keys,
                         &oc->parse_order.order->details.v0.brutto,
                         &oc->set_exchanges.details.v0.max_stefan_fee);
     break;
   case TALER_MERCHANT_CONTRACT_VERSION_1:
     oc->set_exchanges.details.v1.max_stefan_fees
       = GNUNET_new_array (oc->parse_choices.choices_len,
                           struct TALER_Amount);
     for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
       if (0 == strcasecmp (keys->currency,
                            oc->parse_choices.choices[i].amount.currency))
         compute_stefan_fee (keys,
                             &oc->parse_choices.choices[i].amount,
                             &oc->set_exchanges.details.v1.max_stefan_fees[i]);
     break;
   default:
     GNUNET_assert (0);
   }
 }
 
 
 /**
  * Check our KYC status at all exchanges as our current limit is
  * too low and we failed to create an order.
  *
  * @param oc order context
  * @param wmc wire method candidate to notify for
  * @param exchange_url exchange to notify about
  */
 static void
 notify_kyc_required (const struct OrderContext *oc,
                      const struct WireMethodCandidate *wmc,
                      const char *exchange_url)
 {
   struct GNUNET_DB_EventHeaderP es = {
     .size = htons (sizeof (es)),
     .type = htons (TALER_DBEVENT_MERCHANT_EXCHANGE_KYC_RULE_TRIGGERED)
   };
   char *hws;
   char *extra;
 
   hws = GNUNET_STRINGS_data_to_string_alloc (
     &wmc->wm->h_wire,
     sizeof (wmc->wm->h_wire));
 
   GNUNET_asprintf (&extra,
                    "%s %s",
                    hws,
                    exchange_url);
   TALER_MERCHANTDB_event_notify (TMH_db,
                                  &es,
                                  extra,
                                  strlen (extra) + 1);
   GNUNET_free (extra);
   GNUNET_free (hws);
 }
 
 
 /**
  * Add a reason why a particular exchange was rejected to our
  * response data.
  *
  * @param[in,out] oc order context to update
  * @param exchange_url exchange this is about
  * @param ec error code to set for the exchange
  */
 static void
 add_rejection (struct OrderContext *oc,
                const char *exchange_url,
                enum TALER_ErrorCode ec)
 {
   if (NULL == oc->set_exchanges.exchange_rejections)
   {
     oc->set_exchanges.exchange_rejections = json_array ();
     GNUNET_assert (NULL != oc->set_exchanges.exchange_rejections);
   }
   GNUNET_assert (0 ==
                  json_array_append_new (
                    oc->set_exchanges.exchange_rejections,
                    GNUNET_JSON_PACK (
                      GNUNET_JSON_pack_string ("exchange_url",
                                               exchange_url),
                      TALER_JSON_pack_ec (ec))));
 }
 
 
 /**
  * Checks the limits that apply for this @a exchange and
  * the @a wmc and if the exchange is acceptable at all, adds it
  * to the list of exchanges for the @a wmc.
  *
  * @param oc context of the order
  * @param exchange internal handle for the exchange
  * @param exchange_url base URL of this exchange
  * @param wmc wire method to evaluate this exchange for
  * @return true if the exchange is acceptable for the contract
  */
 static bool
 get_acceptable (struct OrderContext *oc,
                 const struct TMH_Exchange *exchange,
                 const char *exchange_url,
                 struct WireMethodCandidate *wmc)
 {
   const struct TALER_Amount *max_needed = NULL;
   unsigned int priority = 42; /* make compiler happy */
   json_t *j_exchange;
   enum TMH_ExchangeStatus res;
   struct TALER_Amount max_amount;
 
   for (unsigned int i = 0;
        i<oc->add_payment_details.num_max_choice_limits;
        i++)
   {
     const struct TALER_Amount *val
       = &oc->add_payment_details.max_choice_limits[i];
 
     if (0 == strcasecmp (val->currency,
                          TMH_EXCHANGES_get_currency (exchange)))
     {
       max_needed = val;
       break;
     }
   }
   if (NULL == max_needed)
   {
     /* exchange currency not relevant for any of our choices, skip it */
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Exchange %s with currency `%s' is not applicable to this order\n",
                 exchange_url,
                 TMH_EXCHANGES_get_currency (exchange));
     add_rejection (oc,
                    exchange_url,
                    TALER_EC_MERCHANT_GENERIC_CURRENCY_MISMATCH);
     return false;
   }
 
   max_amount = *max_needed;
   res = TMH_exchange_check_debit (
     oc->hc->instance->settings.id,
     exchange,
     wmc->wm,
     &max_amount);
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Exchange %s evaluated at %d with max %s\n",
               exchange_url,
               res,
               TALER_amount2s (&max_amount));
   if (TALER_amount_is_zero (&max_amount))
   {
     if (! TALER_amount_is_zero (max_needed))
     {
       /* Trigger re-checking the current deposit limit when
        * paying non-zero amount with zero deposit limit */
       notify_kyc_required (oc,
                            wmc,
                            exchange_url);
     }
     /* If deposit is impossible, we don't list the
      * exchange in the contract terms. */
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Exchange %s deposit limit is zero, skipping it\n",
                 exchange_url);
     add_rejection (oc,
                    exchange_url,
                    TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_EXCHANGE_LEGALLY_REFUSED);
     return false;
   }
   switch (res)
   {
   case TMH_ES_OK:
   case TMH_ES_RETRY_OK:
     priority = 1024;   /* high */
     oc->set_exchanges.exchange_ok = true;
     break;
   case TMH_ES_NO_ACC:
     if (oc->set_exchanges.forced_reload)
       priority = 0;   /* fresh negative response */
     else
       priority = 512; /* stale negative response */
     break;
   case TMH_ES_NO_CURR:
     if (oc->set_exchanges.forced_reload)
       priority = 0;   /* fresh negative response */
     else
       priority = 512; /* stale negative response */
     break;
   case TMH_ES_NO_KEYS:
     if (oc->set_exchanges.forced_reload)
       priority = 256;   /* fresh, no accounts yet */
     else
       priority = 768;  /* stale, no accounts yet */
     break;
   case TMH_ES_NO_ACC_RETRY_OK:
     if (oc->set_exchanges.forced_reload)
     {
       priority = 0;   /* fresh negative response */
     }
     else
     {
       oc->set_exchanges.promising_exchange = true;
       priority = 512; /* stale negative response */
     }
     break;
   case TMH_ES_NO_CURR_RETRY_OK:
     if (oc->set_exchanges.forced_reload)
       priority = 0;   /* fresh negative response */
     else
       priority = 512; /* stale negative response */
     break;
   case TMH_ES_NO_KEYS_RETRY_OK:
     if (oc->set_exchanges.forced_reload)
     {
       priority = 256;   /* fresh, no accounts yet */
     }
     else
     {
       oc->set_exchanges.promising_exchange = true;
       priority = 768;  /* stale, no accounts yet */
     }
     break;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Exchange %s deposit limit is %s, adding it!\n",
               exchange_url,
               TALER_amount2s (&max_amount));
 
   j_exchange = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_string ("url",
                              exchange_url),
     GNUNET_JSON_pack_uint64 ("priority",
                              priority),
     TALER_JSON_pack_amount ("max_contribution",
                             &max_amount),
     GNUNET_JSON_pack_data_auto ("master_pub",
                                 TMH_EXCHANGES_get_master_pub (exchange)));
   GNUNET_assert (NULL != j_exchange);
   /* Add exchange to list of exchanges for this wire method
      candidate */
   GNUNET_assert (0 ==
                  json_array_append_new (wmc->exchanges,
                                         j_exchange));
   GNUNET_assert (0 <=
                  TALER_amount_set_add (&wmc->total_exchange_limits,
                                        &max_amount,
                                        max_needed));
   return true;
 }
 
 
 /**
  * Function called with the result of a #TMH_EXCHANGES_keys4exchange()
  * operation.
  *
  * @param cls closure with our `struct RekeyExchange *`
  * @param keys the keys of the exchange
  * @param exchange representation of the exchange
  */
 static void
 keys_cb (
   void *cls,
   struct TALER_EXCHANGE_Keys *keys,
   struct TMH_Exchange *exchange)
 {
   struct RekeyExchange *rx = cls;
   struct OrderContext *oc = rx->oc;
   const struct TALER_MERCHANTDB_InstanceSettings *settings =
     &oc->hc->instance->settings;
   bool applicable = false;
 
   rx->fo = NULL;
   GNUNET_CONTAINER_DLL_remove (oc->set_exchanges.pending_reload_head,
                                oc->set_exchanges.pending_reload_tail,
                                rx);
   if (NULL == keys)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Failed to download %skeys\n",
                 rx->url);
     oc->set_exchanges.promising_exchange = true;
     add_rejection (oc,
                    rx->url,
                    TALER_EC_MERCHANT_GENERIC_EXCHANGE_KEYS_FAILURE);
     goto cleanup;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Got response for %skeys\n",
               rx->url);
 
   /* Evaluate the use of this exchange for each wire method candidate.
      Note that the exchange may have *several* accounts sharing the same
      wire method; as get_acceptable() judges the exchange as a whole (and
      not the individual account), it must be called at most once per wire
      method candidate, or we would list the exchange more than once in the
      contract terms and count its deposit limit more than once. */
   for (struct WireMethodCandidate *wmc = oc->add_payment_details.wmc_head;
        NULL != wmc;
        wmc = wmc->next)
   {
     bool matches = false;
 
     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                 "Order could use wire method `%s'\n",
                 wmc->wm->wire_method);
     for (unsigned int j = 0; j<keys->accounts_len; j++)
     {
       struct TALER_FullPayto full_payto = keys->accounts[j].fpayto_uri;
       char *wire_method = TALER_payto_get_method (full_payto.full_payto);
 
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   "Exchange `%s' has wire method `%s'\n",
                   rx->url,
                   wire_method);
       matches = (0 == strcmp (wmc->wm->wire_method,
                               wire_method));
       GNUNET_free (wire_method);
       if (matches)
         break;
     }
     if (matches)
       applicable |= get_acceptable (oc,
                                     exchange,
                                     rx->url,
                                     wmc);
   }
   if ( (! applicable) &&
        (! oc->set_exchanges.forced_reload) )
   {
     /* Checks for 'forced_reload' to not log the error *again*
        if we forced a re-load and are encountering the
        applicability error a 2nd time */
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Exchange `%s' %u wire methods are not applicable to this order\n",
                 rx->url,
                 keys->accounts_len);
     add_rejection (oc,
                    rx->url,
                    TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_WIRE_METHOD_UNSUPPORTED);
   }
   if (applicable &&
       settings->use_stefan)
     update_stefan (oc,
                    keys);
 cleanup:
   GNUNET_free (rx->url);
   GNUNET_free (rx);
   if (NULL != oc->set_exchanges.pending_reload_head)
     return;
   resume_with_keys (oc);
 }
 
 
 /**
  * Force re-downloading of /keys from @a exchange,
  * we currently have no acceptable exchange, so we
  * should try to get one.
  *
  * @param cls closure with our `struct OrderContext`
  * @param url base URL of the exchange
  * @param exchange internal handle for the exchange
  */
 static void
 get_exchange_keys (void *cls,
                    const char *url,
                    const struct TMH_Exchange *exchange)
 {
   struct OrderContext *oc = cls;
   struct RekeyExchange *rx;
 
   rx = GNUNET_new (struct RekeyExchange);
   rx->oc = oc;
   rx->url = GNUNET_strdup (url);
   GNUNET_CONTAINER_DLL_insert (oc->set_exchanges.pending_reload_head,
                                oc->set_exchanges.pending_reload_tail,
                                rx);
   if (oc->set_exchanges.forced_reload)
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Forcing download of %skeys\n",
                 url);
   rx->fo = TMH_EXCHANGES_keys4exchange (url,
                                         oc->set_exchanges.forced_reload,
                                         &keys_cb,
                                         rx);
 }
 
 
 /**
  * Task run when we are timing out on /keys and will just
  * proceed with what we got.
  *
  * @param cls our `struct OrderContext *` to resume
  */
 static void
 wakeup_timeout (void *cls)
 {
   struct OrderContext *oc = cls;
 
   oc->set_exchanges.wakeup_task = NULL;
   GNUNET_assert (GNUNET_YES == oc->suspended);
   GNUNET_CONTAINER_DLL_remove (oc_head,
                                oc_tail,
                                oc);
   MHD_resume_connection (oc->connection);
   oc->suspended = GNUNET_NO;
   TALER_MHD_daemon_trigger (); /* we resumed, kick MHD */
 }
 
 
 /**
  * Set list of acceptable exchanges in @a oc. Upon success, continues
  * processing with add_payment_details().
  *
  * @param[in,out] oc order context
  * @return true to suspend execution
  */
 static bool
 phase_set_exchanges (struct OrderContext *oc)
 {
   if (NULL != oc->set_exchanges.wakeup_task)
   {
     GNUNET_SCHEDULER_cancel (oc->set_exchanges.wakeup_task);
     oc->set_exchanges.wakeup_task = NULL;
   }
 
   if (! oc->add_payment_details.need_exchange)
   {
     /* Total amount is zero, so we don't actually need exchanges! */
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Order total is zero, no need for exchanges\n");
     oc->select_wire_method.exchanges = json_array ();
     GNUNET_assert (NULL != oc->select_wire_method.exchanges);
     /* Pick first one, doesn't matter as the amount is zero */
     oc->select_wire_method.wm = oc->hc->instance->wm_head;
     oc->phase = ORDER_PHASE_SET_MAX_FEE;
     return false;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Trying to find exchanges\n");
   if (NULL == oc->set_exchanges.pending_reload_head)
   {
     if (! oc->set_exchanges.exchanges_tried)
     {
       oc->set_exchanges.exchanges_tried = true;
       oc->set_exchanges.keys_timeout
         = GNUNET_TIME_relative_to_absolute (MAX_KEYS_WAIT);
       TMH_exchange_get_trusted (&get_exchange_keys,
                                 oc);
     }
     else if ( (! oc->set_exchanges.forced_reload) &&
               (oc->set_exchanges.promising_exchange) &&
               (! oc->set_exchanges.exchange_ok) )
     {
       for (struct WireMethodCandidate *wmc = oc->add_payment_details.wmc_head;
            NULL != wmc;
            wmc = wmc->next)
         GNUNET_break (0 ==
                       json_array_clear (wmc->exchanges));
       /* Try one more time with forcing /keys download */
       oc->set_exchanges.forced_reload = true;
       TMH_exchange_get_trusted (&get_exchange_keys,
                                 oc);
     }
   }
   if (GNUNET_TIME_absolute_is_past (oc->set_exchanges.keys_timeout))
   {
     struct RekeyExchange *rx;
 
     while (NULL != (rx = oc->set_exchanges.pending_reload_head))
     {
       GNUNET_CONTAINER_DLL_remove (oc->set_exchanges.pending_reload_head,
                                    oc->set_exchanges.pending_reload_tail,
                                    rx);
       TMH_EXCHANGES_keys4exchange_cancel (rx->fo);
       GNUNET_free (rx->url);
       GNUNET_free (rx);
     }
   }
   if (NULL != oc->set_exchanges.pending_reload_head)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Still trying to (re)load %skeys\n",
                 oc->set_exchanges.pending_reload_head->url);
     oc->set_exchanges.wakeup_task
       = GNUNET_SCHEDULER_add_at (oc->set_exchanges.keys_timeout,
                                  &wakeup_timeout,
                                  oc);
     MHD_suspend_connection (oc->connection);
     oc->suspended = GNUNET_YES;
     GNUNET_CONTAINER_DLL_insert (oc_head,
                                  oc_tail,
                                  oc);
     return true; /* reloads pending */
   }
   oc->phase++;
   return false;
 }
 
 
 /* ***************** ORDER_PHASE_ADD_PAYMENT_DETAILS **************** */
 
 /**
  * Process the @a payment_target and add the details of how the
  * order could be paid to @a order. On success, continue
  * processing with add_payment_fees().
  *
  * @param[in,out] oc order context
  */
 static void
 phase_add_payment_details (struct OrderContext *oc)
 {
   /* First, determine the maximum amounts that could be paid per currency */
   switch (oc->parse_order.order->base->version)
   {
   case TALER_MERCHANT_CONTRACT_VERSION_0:
     GNUNET_array_append (oc->add_payment_details.max_choice_limits,
                          oc->add_payment_details.num_max_choice_limits,
                          oc->parse_order.order->details.v0.brutto);
     if (! TALER_amount_is_zero (
           &oc->parse_order.order->details.v0.brutto))
     {
       oc->add_payment_details.need_exchange = true;
     }
     break;
   case TALER_MERCHANT_CONTRACT_VERSION_1:
     for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
     {
       const struct TALER_Amount *amount
         = &oc->parse_choices.choices[i].amount;
       bool found = false;
 
       if (! TALER_amount_is_zero (amount))
       {
         oc->add_payment_details.need_exchange = true;
       }
       for (unsigned int j = 0;
            j<oc->add_payment_details.num_max_choice_limits;
            j++)
       {
         struct TALER_Amount *mx = &oc->add_payment_details.max_choice_limits[j];
         if (GNUNET_YES ==
             TALER_amount_cmp_currency (mx,
                                        amount))
         {
           TALER_amount_max (mx,
                             mx,
                             amount);
           found = true;
           break;
         }
       }
       if (! found)
       {
         GNUNET_array_append (oc->add_payment_details.max_choice_limits,
                              oc->add_payment_details.num_max_choice_limits,
                              *amount);
       }
     }
     break;
   default:
     GNUNET_assert (0);
   }
 
   /* Then, create a candidate for each available wire method */
   for (struct TMH_WireMethod *wm = oc->hc->instance->wm_head;
        NULL != wm;
        wm = wm->next)
   {
     struct WireMethodCandidate *wmc;
 
     /* Locate wire method that has a matching payment target */
     if (! wm->active)
       continue; /* ignore inactive methods */
     if ( (NULL != oc->parse_request.payment_target) &&
          (0 != strcasecmp (oc->parse_request.payment_target,
                            wm->wire_method) ) )
       continue; /* honor client preference */
     wmc = GNUNET_new (struct WireMethodCandidate);
     wmc->wm = wm;
     wmc->exchanges = json_array ();
     GNUNET_assert (NULL != wmc->exchanges);
     GNUNET_CONTAINER_DLL_insert (oc->add_payment_details.wmc_head,
                                  oc->add_payment_details.wmc_tail,
                                  wmc);
   }
 
   if (NULL == oc->add_payment_details.wmc_head)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "No wire method available for instance '%s'\n",
                 oc->hc->instance->settings.id);
     reply_with_error (oc,
                       MHD_HTTP_NOT_FOUND,
                       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_INSTANCE_CONFIGURATION_LACKS_WIRE,
                       oc->parse_request.payment_target);
     return;
   }
 
   /* next, we'll evaluate available exchanges */
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_MERGE_INVENTORY **************** */
 
 
 /**
  * Helper function to sort uint64_t array with qsort().
  *
  * @param a pointer to element to compare
  * @param b pointer to element to compare
  * @return 0 on equal, -1 on smaller, 1 on larger
  */
 static int
 uint64_cmp (const void *a,
             const void *b)
 {
   uint64_t ua = *(const uint64_t *) a;
   uint64_t ub = *(const uint64_t *) b;
 
   if (ua < ub)
     return -1;
   if (ua > ub)
     return 1;
   return 0;
 }
 
 
 /**
  * Merge the inventory products into products, querying the
  * database about the details of those products. Upon success,
  * continue processing by calling add_payment_details().
  *
  * @param[in,out] oc order context to process
  */
 static void
 phase_merge_inventory (struct OrderContext *oc)
 {
   uint64_t pots[oc->parse_order.order->products_len + 1];
   size_t pots_off = 0;
 
   if (0 != oc->parse_order.order->base->default_money_pot)
     pots[pots_off++] = oc->parse_order.order->base->default_money_pot;
   /**
    * parse_request.inventory_products => instructions to add products to contract terms
    * parse_order.products => contains products that are not from the backend-managed inventory.
    */
   oc->merge_inventory.products = json_array ();
   for (size_t i = 0; i<oc->parse_order.order->products_len; i++)
   {
     GNUNET_assert (
       0 ==
       json_array_append_new (
         oc->merge_inventory.products,
         TALER_MERCHANT_product_sold_serialize (
           &oc->parse_order.order->products[i])));
     if (0 != oc->parse_order.order->products[i].product_money_pot)
       pots[pots_off++] = oc->parse_order.order->products[i].product_money_pot;
   }
 
   /* make sure pots array only has distinct elements */
   qsort (pots,
          pots_off,
          sizeof (uint64_t),
          &uint64_cmp);
   {
     size_t e = 0;
 
     for (size_t i = 1; i<pots_off; i++)
     {
       if (pots[e] != pots[i])
         pots[++e] = pots[i];
     }
     if (pots_off > 0)
       e++;
     pots_off = e;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Found %u unique money pots in order\n",
               (unsigned int) pots_off);
 
   /* check if all money pots exist; note that we do NOT treat
      the inventory products to this check, as (1) the foreign key
      constraint should ensure this, and (2) if the money pot
      were deleted (concurrently), the value is specified to be
      considered 0 (aka none) and so we can proceed anyway. */
   if (pots_off > 0)
   {
     enum GNUNET_DB_QueryStatus qs;
     uint64_t pot_missing;
 
     qs = TALER_MERCHANTDB_get_missing_money_pot (TMH_db,
                                                  oc->hc->instance->settings.id,
                                                  pots_off,
                                                  pots,
                                                  &pot_missing);
     switch (qs)
     {
     case GNUNET_DB_STATUS_HARD_ERROR:
     case GNUNET_DB_STATUS_SOFT_ERROR:
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_FETCH_FAILED,
                         "get_missing_money_pot");
       return;
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
       /* great, good case! */
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "All money pots exist\n");
       break;
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
       {
         char mstr[32];
 
         GNUNET_snprintf (mstr,
                          sizeof (mstr),
                          "%llu",
                          (unsigned long long) pot_missing);
         reply_with_error (oc,
                           MHD_HTTP_NOT_FOUND,
                           TALER_EC_MERCHANT_GENERIC_MONEY_POT_UNKNOWN,
                           mstr);
         return;
       }
     }
   }
 
   /* Populate products from inventory product array and database */
   {
     GNUNET_assert (NULL != oc->merge_inventory.products);
     for (unsigned int i = 0; i<oc->parse_request.inventory_products_length; i++)
     {
       struct InventoryProduct *ip
         = &oc->parse_request.inventory_products[i];
       struct TALER_MERCHANTDB_ProductDetails pd;
       enum GNUNET_DB_QueryStatus qs;
       size_t num_categories = 0;
       uint64_t *categories = NULL;
 
       qs = TALER_MERCHANTDB_get_product (TMH_db,
                                          oc->hc->instance->settings.id,
                                          ip->product_id,
                                          &pd,
                                          &num_categories,
                                          &categories);
       if (qs <= 0)
       {
         enum TALER_ErrorCode ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
         unsigned int http_status = 0;
 
         switch (qs)
         {
         case GNUNET_DB_STATUS_HARD_ERROR:
           GNUNET_break (0);
           http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
           ec = TALER_EC_GENERIC_DB_FETCH_FAILED;
           break;
         case GNUNET_DB_STATUS_SOFT_ERROR:
           GNUNET_break (0);
           http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
           ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
           break;
         case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
           GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                       "Product %s from order unknown\n",
                       ip->product_id);
           http_status = MHD_HTTP_NOT_FOUND;
           ec = TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN;
           break;
         case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
           /* case listed to make compilers happy */
           GNUNET_assert (0);
         }
         reply_with_error (oc,
                           http_status,
                           ec,
                           ip->product_id);
         return;
       }
       GNUNET_free (categories);
       oc->parse_order.order->base->minimum_age
         = GNUNET_MAX (oc->parse_order.order->base->minimum_age,
                       pd.minimum_age);
       {
         const char *eparam;
 
         if ( (! ip->quantity_missing) &&
              (ip->quantity > (uint64_t) INT64_MAX) )
         {
           GNUNET_break_op (0);
           reply_with_error (oc,
                             MHD_HTTP_BAD_REQUEST,
                             TALER_EC_GENERIC_PARAMETER_MALFORMED,
                             "quantity");
           TALER_MERCHANTDB_product_details_free (&pd);
           return;
         }
         if (GNUNET_OK !=
             TALER_MERCHANT_vk_process_quantity_inputs (
               TALER_MERCHANT_VK_QUANTITY,
               pd.allow_fractional_quantity,
               ip->quantity_missing,
               (int64_t) ip->quantity,
               ip->unit_quantity_missing,
               ip->unit_quantity,
               &ip->quantity,
               &ip->quantity_frac,
               &eparam))
         {
           GNUNET_break_op (0);
           reply_with_error (oc,
                             MHD_HTTP_BAD_REQUEST,
                             TALER_EC_GENERIC_PARAMETER_MALFORMED,
                             eparam);
           TALER_MERCHANTDB_product_details_free (&pd);
           return;
         }
       }
       {
         struct TALER_MERCHANT_ProductSold ps = {
           .product_id = (char *) ip->product_id,
           .product_name = pd.product_name,
           .description = pd.description,
           .description_i18n = pd.description_i18n,
           .unit_quantity.integer = ip->quantity,
           .unit_quantity.fractional = ip->quantity_frac,
           .prices_length = pd.price_array_length,
           .prices = GNUNET_new_array (pd.price_array_length,
                                       struct TALER_Amount),
           .prices_are_net = pd.price_is_net,
           .image = pd.image,
           .taxes = pd.taxes,
           .delivery_date = oc->parse_order.order->base->delivery_date,
           .product_money_pot = pd.money_pot_id,
           .unit = pd.unit,
 
         };
         json_t *p;
         char unit_quantity_buf[64];
 
         for (size_t j = 0; j<pd.price_array_length; j++)
         {
           struct TALER_Amount atomic_amount;
 
           GNUNET_assert (
             GNUNET_OK ==
             TALER_amount_set_zero (pd.price_array[j].currency,
                                    &atomic_amount));
           atomic_amount.fraction = 1;
           GNUNET_assert (
             GNUNET_OK ==
             TALER_MERCHANT_amount_multiply_by_quantity (
               &ps.prices[j],
               &pd.price_array[j],
               &ps.unit_quantity,
               TALER_MERCHANT_ROUND_UP,
               &atomic_amount));
         }
 
         TALER_MERCHANT_vk_format_fractional_string (
           TALER_MERCHANT_VK_QUANTITY,
           ip->quantity,
           ip->quantity_frac,
           sizeof (unit_quantity_buf),
           unit_quantity_buf);
         if (0 != pd.money_pot_id)
           pots[pots_off++] = pd.money_pot_id;
         p = TALER_MERCHANT_product_sold_serialize (&ps);
         GNUNET_assert (NULL != p);
         GNUNET_free (ps.prices);
         GNUNET_assert (0 ==
                        json_array_append_new (oc->merge_inventory.products,
                                               p));
       }
       TALER_MERCHANTDB_product_details_free (&pd);
     }
   }
 
   /* check if final product list is well-formed */
   if (! TMH_products_array_valid (oc->merge_inventory.products))
   {
     GNUNET_break_op (0);
     reply_with_error (oc,
                       MHD_HTTP_BAD_REQUEST,
                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                       "order:products");
     return;
   }
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_PARSE_CHOICES **************** */
 
 /**
  * Callback function that is called for each donau instance.
  * It simply adds the provided donau_url to the json.
  *
  * @param cls closure with our `struct TALER_MERCHANT_ContractOutput *`
  * @param donau_url the URL of the donau instance
  */
 static void
 add_donau_url (void *cls,
                const char *donau_url)
 {
   struct TALER_MERCHANT_ContractOutput *output = cls;
 
   GNUNET_array_append (output->details.donation_receipt.donau_urls,
                        output->details.donation_receipt.donau_urls_len,
                        GNUNET_strdup (donau_url));
 }
 
 
 /**
  * Add the donau output to the contract output.
  *
  * @param oc order context
  * @param output contract output to add donau URLs to
  */
 static bool
 add_donau_output (struct OrderContext *oc,
                   struct TALER_MERCHANT_ContractOutput *output)
 {
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TALER_MERCHANTDB_iterate_donau_instances_filtered (
     TMH_db,
     output->details.donation_receipt.amount.currency,
     &add_donau_url,
     output);
   if (qs < 0)
   {
     GNUNET_break (0);
     reply_with_error (oc,
                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                       TALER_EC_GENERIC_DB_FETCH_FAILED,
                       "donau url parsing db call");
     for (unsigned int i = 0;
          i < output->details.donation_receipt.donau_urls_len;
          i++)
       GNUNET_free (output->details.donation_receipt.donau_urls[i]);
     GNUNET_array_grow (output->details.donation_receipt.donau_urls,
                        output->details.donation_receipt.donau_urls_len,
                        0);
     return false;
   }
   return true;
 }
 
 
 /**
  * Parse contract choices. Upon success, continue
  * processing with merge_inventory().
  *
  * @param[in,out] oc order context
  */
 static void
 phase_parse_choices (struct OrderContext *oc)
 {
   switch (oc->parse_order.order->base->version)
   {
   case TALER_MERCHANT_CONTRACT_VERSION_0:
     oc->phase++;
     return;
   case TALER_MERCHANT_CONTRACT_VERSION_1:
     /* handle below */
     break;
   default:
     GNUNET_assert (0);
   }
 
   /* Convert order choices to contract choices */
   GNUNET_array_grow (oc->parse_choices.choices,
                      oc->parse_choices.choices_len,
                      oc->parse_order.order->details.v1.choices_len);
   for (unsigned int i = 0; i<oc->parse_choices.choices_len; i++)
   {
     const struct TALER_MERCHANT_OrderChoice *ochoice
       = &oc->parse_order.order->details.v1.choices[i];
     struct TALER_MERCHANT_ContractChoice *cchoice
       = &oc->parse_choices.choices[i];
     unsigned int off;
 
     if (! TMH_test_exchange_configured_for_currency (
           ochoice->amount.currency))
     {
       GNUNET_break_op (0);
       reply_with_error (oc,
                         MHD_HTTP_CONFLICT,
                         TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_NO_EXCHANGE_FOR_CURRENCY,
                         ochoice->amount.currency);
       return;
     }
     cchoice->amount = ochoice->amount;
     cchoice->tip = ochoice->tip;
     cchoice->no_tip = ochoice->no_tip;
     if (NULL != ochoice->description)
       cchoice->description = GNUNET_strdup (ochoice->description);
     if (NULL != ochoice->description_i18n)
       cchoice->description_i18n = json_incref (ochoice->description_i18n);
     cchoice->max_fee = ochoice->max_fee;
 
     /* convert inputs */
     GNUNET_array_grow (cchoice->inputs,
                        cchoice->inputs_len,
                        ochoice->inputs_len);
     off = 0;
     for (unsigned int j = 0; j < ochoice->inputs_len; j++)
     {
       const struct TALER_MERCHANT_OrderInput *order_input
         = &ochoice->inputs[j];
       struct TALER_MERCHANT_ContractInput *contract_input
         = &cchoice->inputs[off];
 
       contract_input->type = order_input->type;
       switch (order_input->type)
       {
       case TALER_MERCHANT_CONTRACT_INPUT_TYPE_INVALID:
         GNUNET_assert (0);
         break;
       case TALER_MERCHANT_CONTRACT_INPUT_TYPE_TOKEN:
         /* Ignore inputs tokens with 'count' field set to 0 */
         if (0 == order_input->details.token.count)
           continue;
         contract_input->details.token.count
           = order_input->details.token.count;
         contract_input->details.token.token_family_slug
           = order_input->details.token.token_family_slug;
         if (GNUNET_OK !=
             add_input_token_family (oc,
                                     contract_input->details.token.token_family_slug))
         {
           GNUNET_break_op (0);
           return;
         }
         off++;
         continue;
       } /* switch input type */
       GNUNET_assert (0);
     } /* for all inputs */
     GNUNET_array_grow (cchoice->inputs,
                        cchoice->inputs_len,
                        off);
 
     /* convert outputs */
     GNUNET_array_grow (cchoice->outputs,
                        cchoice->outputs_len,
                        ochoice->outputs_len);
     off = 0;
     for (unsigned int j = 0; j < ochoice->outputs_len; j++)
     {
       const struct TALER_MERCHANT_OrderOutput *order_output
         = &ochoice->outputs[j];
       struct TALER_MERCHANT_ContractOutput *contract_output
         = &cchoice->outputs[off];
 
       contract_output->type = order_output->type;
       switch (order_output->type)
       {
       case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_INVALID:
         GNUNET_assert (0);
         break;
       case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_DONATION_RECEIPT:
         if (order_output->details.donation_receipt.no_amount)
         {
           contract_output->details.donation_receipt.amount
             = ochoice->amount;
         }
         else
         {
           contract_output->details.donation_receipt.amount
             = order_output->details.donation_receipt.amount;
         }
         if (! add_donau_output (oc,
                                 contract_output))
         {
           GNUNET_break (0);
           return;
         }
         off++;
         continue;
       case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_TOKEN:
         /* Ignore inputs tokens with 'count' field set to 0 */
         if (0 == order_output->details.token.count)
           continue;
 
         contract_output->details.token.token_family_slug
           = order_output->details.token.token_family_slug;
         contract_output->details.token.count
           = order_output->details.token.count;
         if (0 == order_output->details.token.valid_at.abs_time.abs_value_us)
           contract_output->details.token.valid_at
             = GNUNET_TIME_timestamp_get ();
         else
           contract_output->details.token.valid_at
             = order_output->details.token.valid_at;
         if (GNUNET_OK !=
             add_output_token_family (
               oc,
               contract_output->details.token.token_family_slug,
               contract_output->details.token.valid_at,
               &contract_output->details.token.key_index))
 
         {
           /* note: reply_with_error() was already called */
           GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                       "Could not handle output token family `%s'\n",
                       contract_output->details.token.token_family_slug);
           return;
         }
         off++;
         continue;
       } /* end switch */
       GNUNET_assert (0);
     } /* for outputs */
     GNUNET_array_grow (cchoice->outputs,
                        cchoice->outputs_len,
                        off);
   } /* for all choices */
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_PARSE_ORDER **************** */
 
 
 /**
  * Parse the order field of the request. Upon success, continue
  * processing with parse_choices().
  *
  * @param[in,out] oc order context
  */
 static void
 phase_parse_order (struct OrderContext *oc)
 {
   const struct TALER_MERCHANTDB_InstanceSettings *settings =
     &oc->hc->instance->settings;
   bool computed_refund_deadline = false;
 
   oc->parse_order.order
     = TALER_MERCHANT_order_parse (
         oc->parse_request.order);
   if (NULL == oc->parse_order.order)
   {
     GNUNET_break_op (0);
     reply_with_error (oc,
                       MHD_HTTP_BAD_REQUEST,
                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                       "order");
     return;
   }
 
   switch (oc->parse_order.order->base->version)
   {
   case TALER_MERCHANT_CONTRACT_VERSION_0:
     if (! TMH_test_exchange_configured_for_currency (
           oc->parse_order.order->details.v0.brutto.currency))
     {
       GNUNET_break_op (0);
       reply_with_error (
         oc,
         MHD_HTTP_CONFLICT,
         TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_NO_EXCHANGE_FOR_CURRENCY,
         oc->parse_order.order->details.v0.brutto.currency);
       return;
     }
     break;
   case TALER_MERCHANT_CONTRACT_VERSION_1:
     break;
   default:
     GNUNET_break_op (0);
     reply_with_error (oc,
                       MHD_HTTP_BAD_REQUEST,
                       TALER_EC_GENERIC_VERSION_MALFORMED,
                       "invalid version specified in order, supported are null, '0' or '1'");
     return;
   }
 
   /* Add order_id if it doesn't exist. */
   if (NULL == oc->parse_order.order->order_id)
   {
     char buf[256];
     time_t timer;
     struct tm *tm_info;
     size_t off;
     uint64_t rand;
     char *last;
 
     time (&timer);
     tm_info = localtime (&timer);
     if (NULL == tm_info)
     {
       reply_with_error (
         oc,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
         TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_NO_LOCALTIME,
         NULL);
       return;
     }
     off = strftime (buf,
                     sizeof (buf) - 1,
                     "%Y.%j",
                     tm_info);
     /* Check for error state of strftime */
     GNUNET_assert (0 != off);
     buf[off++] = '-';
     rand = GNUNET_CRYPTO_random_u64 (UINT64_MAX);
     last = GNUNET_STRINGS_data_to_string (&rand,
                                           sizeof (uint64_t),
                                           &buf[off],
                                           sizeof (buf) - off);
     GNUNET_assert (NULL != last);
     *last = '\0';
 
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Assigning order ID `%s' server-side\n",
                 buf);
     oc->parse_order.order->order_id = GNUNET_strdup (buf);
   }
 
   /* Patch fulfillment URL with order_id (implements #6467). */
   if (NULL != oc->parse_order.order->base->fulfillment_url)
   {
     const char *pos;
 
     pos = strstr (oc->parse_order.order->base->fulfillment_url,
                   "${ORDER_ID}");
     if (NULL != pos)
     {
       /* replace ${ORDER_ID} with the real order_id */
       char *nurl;
 
       /* We only allow one placeholder */
       if (strstr (pos + strlen ("${ORDER_ID}"),
                   "${ORDER_ID}"))
       {
         GNUNET_break_op (0);
         reply_with_error (oc,
                           MHD_HTTP_BAD_REQUEST,
                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                           "fulfillment_url");
         return;
       }
 
       GNUNET_asprintf (
         &nurl,
         "%.*s%s%s",
         /* first output URL until ${ORDER_ID} */
         (int) (pos - oc->parse_order.order->base->fulfillment_url),
         oc->parse_order.order->base->fulfillment_url,
         /* replace ${ORDER_ID} with the right order_id */
         oc->parse_order.order->order_id,
         /* append rest of original URL */
         pos + strlen ("${ORDER_ID}"));
       oc->parse_order.order->base->fulfillment_url = GNUNET_strdup (nurl);
       GNUNET_free (nurl);
     }
   }
 
   if ( (GNUNET_TIME_absolute_is_zero (
           oc->parse_order.order->pay_deadline.abs_time)) ||
        (GNUNET_TIME_absolute_is_never (
           oc->parse_order.order->pay_deadline.abs_time)) )
   {
     oc->parse_order.order->pay_deadline
       = GNUNET_TIME_relative_to_timestamp (
           settings->default_pay_delay);
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Pay deadline was zero (or never), setting to %s\n",
                 GNUNET_TIME_timestamp2s (
                   oc->parse_order.order->pay_deadline));
   }
   else if (GNUNET_TIME_absolute_is_past (
              oc->parse_order.order->pay_deadline.abs_time))
   {
     GNUNET_break_op (0);
     reply_with_error (
       oc,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_PAY_DEADLINE_IN_PAST,
       NULL);
     return;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Pay deadline is %s\n",
               GNUNET_TIME_timestamp2s (
                 oc->parse_order.order->pay_deadline));
 
   /* Check soundness of refund deadline, and that a timestamp
    * is actually present.  */
   {
     struct GNUNET_TIME_Timestamp now = GNUNET_TIME_timestamp_get ();
 
     /* Add timestamp if it doesn't exist (or is zero) */
     if (GNUNET_TIME_absolute_is_zero (
           oc->parse_order.order->timestamp.abs_time))
     {
       oc->parse_order.order->timestamp = now;
     }
 
     /* If no refund_deadline given, set one based on refund_delay.  */
     if (GNUNET_TIME_absolute_is_never (
           oc->parse_order.order->refund_deadline.abs_time))
     {
       if (GNUNET_TIME_relative_is_zero (
             oc->parse_request.refund_delay))
       {
         GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                     "Refund delay is zero, no refunds are possible for this order\n");
         oc->parse_order.order->refund_deadline = GNUNET_TIME_UNIT_ZERO_TS;
       }
       else
       {
         computed_refund_deadline = true;
         oc->parse_order.order->refund_deadline
           = GNUNET_TIME_absolute_to_timestamp (
               GNUNET_TIME_absolute_add (
                 oc->parse_order.order->pay_deadline.abs_time,
                 oc->parse_request.refund_delay));
       }
     }
 
     if ( (! GNUNET_TIME_absolute_is_zero (
             oc->parse_order.order->base->delivery_date.abs_time)) &&
          (GNUNET_TIME_absolute_is_past (
             oc->parse_order.order->base->delivery_date.abs_time)) )
     {
       GNUNET_break_op (0);
       reply_with_error (
         oc,
         MHD_HTTP_BAD_REQUEST,
         TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_DELIVERY_DATE_IN_PAST,
         NULL);
       return;
     }
   }
 
   if ( (! GNUNET_TIME_absolute_is_zero (
           oc->parse_order.order->refund_deadline.abs_time)) &&
        (GNUNET_TIME_absolute_is_past (
           oc->parse_order.order->refund_deadline.abs_time)) )
   {
     GNUNET_break_op (0);
     reply_with_error (
       oc,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_REFUND_DEADLINE_IN_PAST,
       NULL);
     return;
   }
 
   if (GNUNET_TIME_absolute_is_never (
         oc->parse_order.order->wire_transfer_deadline.abs_time))
   {
     struct GNUNET_TIME_Absolute start;
 
     start = GNUNET_TIME_absolute_max (
       oc->parse_order.order->refund_deadline.abs_time,
       oc->parse_order.order->pay_deadline.abs_time);
     oc->parse_order.order->wire_transfer_deadline
       = GNUNET_TIME_absolute_to_timestamp (
           GNUNET_TIME_round_up (
             GNUNET_TIME_absolute_add (
               start,
               settings->default_wire_transfer_delay),
             settings->default_wire_transfer_rounding_interval));
     if (GNUNET_TIME_absolute_is_never (
           oc->parse_order.order->wire_transfer_deadline.abs_time))
     {
       GNUNET_break_op (0);
       reply_with_error (
         oc,
         MHD_HTTP_BAD_REQUEST,
         TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_WIRE_DEADLINE_IS_NEVER,
         "order:wire_transfer_deadline");
       return;
     }
   }
   else if (computed_refund_deadline)
   {
     /* if we computed the refund_deadline from default settings
        and did have a configured wire_deadline, make sure that
        the refund_deadline is at or below the wire_deadline. */
     oc->parse_order.order->refund_deadline
       = GNUNET_TIME_timestamp_min (
           oc->parse_order.order->refund_deadline,
           oc->parse_order.order->wire_transfer_deadline);
   }
   if (GNUNET_TIME_timestamp_cmp (
         oc->parse_order.order->wire_transfer_deadline,
         <,
         oc->parse_order.order->refund_deadline))
   {
     GNUNET_break_op (0);
     reply_with_error (
       oc,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_REFUND_AFTER_WIRE_DEADLINE,
       "order:wire_transfer_deadline;order:refund_deadline");
     return;
   }
 
   {
     char *url;
 
     url = make_merchant_base_url (oc->connection,
                                   settings->id);
     if (NULL == url)
     {
       GNUNET_break_op (0);
       reply_with_error (
         oc,
         MHD_HTTP_BAD_REQUEST,
         TALER_EC_GENERIC_PARAMETER_MISSING,
         "order:merchant_base_url");
       return;
     }
     oc->parse_order.merchant_base_url = url;
   }
 
   // FIXME: move to util during parsing!
   if ( (NULL != oc->parse_order.order->base->delivery_location) &&
        (! TMH_location_object_valid (oc->parse_order.order->base->delivery_location)) )
   {
     GNUNET_break_op (0);
     reply_with_error (oc,
                       MHD_HTTP_BAD_REQUEST,
                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                       "delivery_location");
     return;
   }
 
   oc->phase++;
 }
 
 
 /* ***************** ORDER_PHASE_PARSE_REQUEST **************** */
 
 /**
  * Parse the client request. Upon success,
  * continue processing by calling parse_order().
  *
  * @param[in,out] oc order context to process
  */
 static void
 phase_parse_request (struct OrderContext *oc)
 {
   const json_t *ip = NULL;
   const json_t *uuid = NULL;
   const char *otp_id = NULL;
   bool create_token = true; /* default */
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_json ("order",
                            &oc->parse_request.order),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_relative_time ("refund_delay",
                                       &oc->parse_request.refund_delay),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_string ("payment_target",
                                &oc->parse_request.payment_target),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_array_const ("inventory_products",
                                     &ip),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_string ("session_id",
                                &oc->parse_request.session_id),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_array_const ("lock_uuids",
                                     &uuid),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_bool ("create_token",
                              &create_token),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_string ("otp_id",
                                &otp_id),
       NULL),
     GNUNET_JSON_spec_end ()
   };
   enum GNUNET_GenericReturnValue ret;
 
   oc->parse_request.refund_delay
     = oc->hc->instance->settings.default_refund_delay;
   ret = TALER_MHD_parse_json_data (oc->connection,
                                    oc->hc->request_body,
                                    spec);
   if (GNUNET_OK != ret)
   {
     GNUNET_break_op (0);
     finalize_order2 (oc,
                      ret);
     return;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Refund delay is %s\n",
               GNUNET_TIME_relative2s (oc->parse_request.refund_delay,
                                       false));
   TALER_MERCHANTDB_do_expire_locks (TMH_db);
   if (NULL != otp_id)
   {
     struct TALER_MERCHANTDB_OtpDeviceDetails td;
     enum GNUNET_DB_QueryStatus qs;
 
     memset (&td,
             0,
             sizeof (td));
     qs = TALER_MERCHANTDB_get_otp_device (TMH_db,
                                           oc->hc->instance->settings.id,
                                           otp_id,
                                           &td);
     switch (qs)
     {
     case GNUNET_DB_STATUS_HARD_ERROR:
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_FETCH_FAILED,
                         "get_otp_device");
       return;
     case GNUNET_DB_STATUS_SOFT_ERROR:
       GNUNET_break (0);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_DB_SOFT_FAILURE,
                         "get_otp_device");
       return;
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
       reply_with_error (oc,
                         MHD_HTTP_NOT_FOUND,
                         TALER_EC_MERCHANT_GENERIC_OTP_DEVICE_UNKNOWN,
                         otp_id);
       return;
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
       break;
     }
     oc->parse_request.pos_key = td.otp_key;
     oc->parse_request.pos_algorithm = td.otp_algorithm;
     GNUNET_free (td.otp_description);
   }
   if (create_token)
   {
     GNUNET_CRYPTO_random_block (&oc->parse_request.claim_token,
                                 sizeof (oc->parse_request.claim_token));
   }
   /* Compute h_post_data (for idempotency check) */
   {
     char *req_body_enc;
 
     /* Dump normalized JSON to string. */
     if (NULL == (req_body_enc
                    = json_dumps (oc->hc->request_body,
                                  JSON_ENCODE_ANY
                                  | JSON_COMPACT
                                  | JSON_SORT_KEYS)))
     {
       GNUNET_break (0);
       GNUNET_JSON_parse_free (spec);
       reply_with_error (oc,
                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                         TALER_EC_GENERIC_ALLOCATION_FAILURE,
                         "request body normalization for hashing");
       return;
     }
     GNUNET_CRYPTO_hash (req_body_enc,
                         strlen (req_body_enc),
                         &oc->parse_request.h_post_data.hash);
     GNUNET_free (req_body_enc);
   }
 
   /* parse the inventory_products (optionally given) */
   if (NULL != ip)
   {
     unsigned int ipl = (unsigned int) json_array_size (ip);
 
     if ( (json_array_size (ip) != (size_t) ipl) ||
          (ipl > MAX_PRODUCTS) )
     {
       GNUNET_break_op (0);
       GNUNET_JSON_parse_free (spec);
       reply_with_error (oc,
                         MHD_HTTP_BAD_REQUEST,
                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                         "inventory_products (too many)");
       return;
     }
     GNUNET_array_grow (oc->parse_request.inventory_products,
                        oc->parse_request.inventory_products_length,
                        (unsigned int) json_array_size (ip));
     for (unsigned int i = 0; i<oc->parse_request.inventory_products_length; i++)
     {
       struct InventoryProduct *ipr = &oc->parse_request.inventory_products[i];
       const char *error_name;
       unsigned int error_line;
       struct GNUNET_JSON_Specification ispec[] = {
         GNUNET_JSON_spec_string ("product_id",
                                  &ipr->product_id),
         GNUNET_JSON_spec_mark_optional (
           GNUNET_JSON_spec_uint64 ("quantity",
                                    &ipr->quantity),
           &ipr->quantity_missing),
         GNUNET_JSON_spec_mark_optional (
           GNUNET_JSON_spec_string ("unit_quantity",
                                    &ipr->unit_quantity),
           &ipr->unit_quantity_missing),
         GNUNET_JSON_spec_mark_optional (
           GNUNET_JSON_spec_uint64 ("product_money_pot",
                                    &ipr->product_money_pot),
           NULL),
         GNUNET_JSON_spec_end ()
       };
 
       ret = GNUNET_JSON_parse (json_array_get (ip,
                                                i),
                                ispec,
                                &error_name,
                                &error_line);
       if (GNUNET_OK != ret)
       {
         GNUNET_break_op (0);
         GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                     "Product parsing failed at #%u: %s:%u\n",
                     i,
                     error_name,
                     error_line);
         reply_with_error (oc,
                           MHD_HTTP_BAD_REQUEST,
                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                           "inventory_products");
         return;
       }
       if (ipr->quantity_missing && ipr->unit_quantity_missing)
       {
         ipr->quantity = 1;
         ipr->quantity_missing = false;
       }
     }
   }
 
   /* parse the lock_uuids (optionally given) */
   if (NULL != uuid)
   {
     GNUNET_array_grow (oc->parse_request.uuids,
                        oc->parse_request.uuids_length,
                        json_array_size (uuid));
     for (unsigned int i = 0; i<oc->parse_request.uuids_length; i++)
     {
       json_t *ui = json_array_get (uuid,
                                    i);
 
       if (! json_is_string (ui))
       {
         GNUNET_break_op (0);
         GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                     "UUID parsing failed at #%u\n",
                     i);
         reply_with_error (oc,
                           MHD_HTTP_BAD_REQUEST,
                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                           "lock_uuids");
         return;
       }
       TMH_uuid_from_string (json_string_value (ui),
                             &oc->parse_request.uuids[i]);
     }
   }
   oc->phase++;
 }
 
 
 /* ***************** Main handler **************** */
 
 
 enum MHD_Result
 TMH_private_post_orders (
   const struct TMH_RequestHandler *rh,
   struct MHD_Connection *connection,
   struct TMH_HandlerContext *hc)
 {
   struct OrderContext *oc = hc->ctx;
 
   if (NULL == oc)
   {
     oc = GNUNET_new (struct OrderContext);
     hc->ctx = oc;
     hc->cc = &clean_order;
     oc->connection = connection;
     oc->hc = hc;
   }
   while (1)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Processing order in phase %d\n",
                 oc->phase);
     switch (oc->phase)
     {
     case ORDER_PHASE_PARSE_REQUEST:
       phase_parse_request (oc);
       break;
     case ORDER_PHASE_PARSE_ORDER:
       phase_parse_order (oc);
       break;
     case ORDER_PHASE_PARSE_CHOICES:
       phase_parse_choices (oc);
       break;
     case ORDER_PHASE_MERGE_INVENTORY:
       phase_merge_inventory (oc);
       break;
     case ORDER_PHASE_ADD_PAYMENT_DETAILS:
       phase_add_payment_details (oc);
       break;
     case ORDER_PHASE_SET_EXCHANGES:
       if (phase_set_exchanges (oc))
         return MHD_YES;
       break;
     case ORDER_PHASE_SELECT_WIRE_METHOD:
       phase_select_wire_method (oc);
       break;
     case ORDER_PHASE_SET_MAX_FEE:
       phase_set_max_fee (oc);
       break;
     case ORDER_PHASE_SERIALIZE_ORDER:
       phase_serialize_order (oc);
       break;
     case ORDER_PHASE_CHECK_CONTRACT:
       phase_check_contract (oc);
       break;
     case ORDER_PHASE_SALT_FORGETTABLE:
       phase_salt_forgettable (oc);
       break;
     case ORDER_PHASE_EXECUTE_ORDER:
       phase_execute_order (oc);
       break;
     case ORDER_PHASE_FINISHED_MHD_YES:
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Finished processing order (1)\n");
       return MHD_YES;
     case ORDER_PHASE_FINISHED_MHD_NO:
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Finished processing order (0)\n");
       return MHD_NO;
     }
   }
 }
 
 
 /* end of taler-merchant-httpd_post-private-orders.c */