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/*
  This file is part of TALER
  (C) 2014-2021 Taler Systems SA

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU Affero General Public License as published by the Free Software
  Foundation; either version 3, or (at your option) any later version.

  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file taler-merchant-httpd_private-post-orders-ID-refund.c
 * @brief Handle request to increase the refund for an order
 * @author Marcello Stanisci
 * @author Christian Grothoff
 */
#include "platform.h"
#include <jansson.h>
#include <taler/taler_dbevents.h>
#include <taler/taler_signatures.h>
#include <taler/taler_json_lib.h>
#include "taler-merchant-httpd_private-post-orders-ID-refund.h"
#include "taler-merchant-httpd_private-get-orders.h"


/**
 * How often do we retry the non-trivial refund INSERT database
 * transaction?
 */
#define MAX_RETRIES 5


/**
 * Use database to notify other clients about the
 * @a order_id being refunded
 *
 * @param order_id the order receiving a refund
 * @param amount the (total) refunded amount
 */
static void
trigger_refund_notification (const char *order_id,
                             const struct TALER_Amount *amount)
{
  const char *as;
  struct TMH_OrderRefundEvent refund_eh = {
    .header.size = htons (sizeof (refund_eh)),
    .header.type = htons (TALER_DBEVENT_MERCHANT_ORDER_REFUND)
  };

  as = TALER_amount2s (amount);
  GNUNET_CRYPTO_hash (order_id,
                      strlen (order_id),
                      &refund_eh.h_order_id);
  TMH_db->event_notify (TMH_db->cls,
                        &refund_eh.header,
                        as,
                        strlen (as));
}


/**
 * Make a taler://refund URI
 *
 * @param connection MHD connection to take host and path from
 * @param instance_id merchant's instance ID, must not be NULL
 * @param order_id order ID to show a refund for, must not be NULL
 * @returns the URI, must be freed with #GNUNET_free
 */
static char *
make_taler_refund_uri (struct MHD_Connection *connection,
                       const char *instance_id,
                       const char *order_id)
{
  const char *host;
  const char *forwarded_host;
  const char *uri_path;
  struct GNUNET_Buffer buf = { 0 };

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

  host = MHD_lookup_connection_value (connection,
                                      MHD_HEADER_KIND,
                                      "Host");
  forwarded_host = MHD_lookup_connection_value (connection,
                                                MHD_HEADER_KIND,
                                                "X-Forwarded-Host");
  uri_path = MHD_lookup_connection_value (connection,
                                          MHD_HEADER_KIND,
                                          "X-Forwarded-Prefix");
  if (NULL != forwarded_host)
    host = forwarded_host;
  if (NULL == host)
  {
    /* Should never happen, at least the host header should be defined */
    GNUNET_break (0);
    return NULL;
  }
  GNUNET_buffer_write_str (&buf, "taler");
  if (GNUNET_NO == TALER_mhd_is_https (connection))
    GNUNET_buffer_write_str (&buf, "+http");
  GNUNET_buffer_write_str (&buf, "://refund/");
  GNUNET_buffer_write_str (&buf, host);
  if (NULL != uri_path)
    GNUNET_buffer_write_path (&buf, uri_path);
  if (0 != strcmp ("default", instance_id))
  {
    GNUNET_buffer_write_path (&buf, "instances");
    GNUNET_buffer_write_path (&buf, instance_id);
  }
  GNUNET_buffer_write_path (&buf, order_id);
  GNUNET_buffer_write_path (&buf,
                            ""); /* Trailing slash */
  return GNUNET_buffer_reap_str (&buf);
}


/**
 * Handle request for increasing the refund associated with
 * a contract.
 *
 * @param rh context of the handler
 * @param connection the MHD connection to handle
 * @param[in,out] hc context with further information about the request
 * @return MHD result code
 */
MHD_RESULT
TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
                                   struct MHD_Connection *connection,
                                   struct TMH_HandlerContext *hc)
{
  struct TALER_Amount refund;
  const char *reason;
  struct GNUNET_JSON_Specification spec[] = {
    TALER_JSON_spec_amount ("refund",
                            TMH_currency,
                            &refund),
    GNUNET_JSON_spec_string ("reason",
                             &reason),
    GNUNET_JSON_spec_end ()
  };
  enum TALER_MERCHANTDB_RefundStatus rs;
  struct GNUNET_HashCode h_contract;

  {
    enum GNUNET_DB_QueryStatus qs;
    json_t *contract_terms;
    uint64_t order_serial;
    struct GNUNET_TIME_Absolute refund_deadline;
    struct GNUNET_TIME_Absolute timestamp;

    qs = TMH_db->lookup_contract_terms (TMH_db->cls,
                                        hc->instance->settings.id,
                                        hc->infix,
                                        &contract_terms,
                                        &order_serial,
                                        NULL);
    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
    {
      struct GNUNET_JSON_Specification spec[] = {
        TALER_JSON_spec_absolute_time ("refund_deadline",
                                       &refund_deadline),
        TALER_JSON_spec_absolute_time ("timestamp",
                                       &timestamp),
        GNUNET_JSON_spec_end ()
      };

      if (GNUNET_YES !=
          GNUNET_JSON_parse (contract_terms,
                             spec,
                             NULL, NULL))
      {
        GNUNET_break (0);
        GNUNET_JSON_parse_free (spec);
        json_decref (contract_terms);
        return TALER_MHD_reply_with_error (
          connection,
          MHD_HTTP_INTERNAL_SERVER_ERROR,
          TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
          "mandatory fields missing");
      }
      json_decref (contract_terms);
      if (timestamp.abs_value_us == refund_deadline.abs_value_us)
      {
        /* refund was never allowed, so we should refuse hard */
        return TALER_MHD_reply_with_error (
          connection,
          MHD_HTTP_FORBIDDEN,
          TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ID_REFUND_NOT_ALLOWED_BY_CONTRACT,
          NULL);
      }
      if (GNUNET_TIME_absolute_is_past (refund_deadline))
      {
        /* it is too late for refunds */
        /* NOTE: We MAY still be lucky that the exchange did not yet
           wire the funds, so we will try to give the refund anyway */
      }
    }
    else
    {
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_NOT_FOUND,
                                         TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                         hc->infix);
    }
  }

  {
    enum GNUNET_GenericReturnValue res;

    res = TALER_MHD_parse_json_data (connection,
                                     hc->request_body,
                                     spec);
    if (GNUNET_OK != res)
      return (GNUNET_NO == res)
             ? MHD_YES
             : MHD_NO;
  }

  TMH_db->preflight (TMH_db->cls);
  for (unsigned int i = 0; i<MAX_RETRIES; i++)
  {
    if (GNUNET_OK !=
        TMH_db->start (TMH_db->cls,
                       "increase refund"))
    {
      GNUNET_break (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_GENERIC_DB_START_FAILED,
                                         NULL);
    }
    rs = TMH_db->increase_refund (TMH_db->cls,
                                  hc->instance->settings.id,
                                  hc->infix,
                                  &refund,
                                  reason);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "increase refund returned %d\n",
                rs);
    if (TALER_MERCHANTDB_RS_SUCCESS != rs)
      TMH_db->rollback (TMH_db->cls);
    if (TALER_MERCHANTDB_RS_SOFT_ERROR == rs)
      continue;
    if (TALER_MERCHANTDB_RS_SUCCESS == rs)
    {
      enum GNUNET_DB_QueryStatus qs;

      trigger_refund_notification (hc->infix,
                                   &refund);
      qs = TMH_db->commit (TMH_db->cls);
      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      {
        GNUNET_break (0);
        rs = TALER_MERCHANTDB_RS_HARD_ERROR;
        break;
      }
      if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
        continue;
    }
    break;
  } /* retries loop */

  switch (rs)
  {
  case TALER_MERCHANTDB_RS_TOO_HIGH:
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Refusing refund amount %s that is larger than original payment\n",
                TALER_amount2s (&refund));
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_CONFLICT,
                                       TALER_EC_EXCHANGE_REFUND_INCONSISTENT_AMOUNT,
                                       "Amount above payment");
  case TALER_MERCHANTDB_RS_SOFT_ERROR:
  case TALER_MERCHANTDB_RS_HARD_ERROR:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                       NULL);
  case TALER_MERCHANTDB_RS_NO_SUCH_ORDER:
    {
      /* We know the order exists from the
         "lookup_contract_terms" at the beginning;
         so if we get 'no such order' here, it
         must be read as "no PAID order" */
      return TALER_MHD_reply_with_error (
        connection,
        MHD_HTTP_CONFLICT,
        TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ID_REFUND_ORDER_UNPAID,
        hc->infix);
    }
  case TALER_MERCHANTDB_RS_SUCCESS:
    {
      enum GNUNET_DB_QueryStatus qs;
      json_t *contract_terms;
      uint64_t order_serial;

      qs = TMH_db->lookup_contract_terms (TMH_db->cls,
                                          hc->instance->settings.id,
                                          hc->infix,
                                          &contract_terms,
                                          &order_serial,
                                          NULL);
      if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
      {
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_NOT_FOUND,
                                           TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                           hc->infix);
      }
      if (GNUNET_OK !=
          TALER_JSON_contract_hash (contract_terms,
                                    &h_contract))
      {
        GNUNET_break (0);
        json_decref (contract_terms);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
                                           "Could not hash contract terms");
      }
      json_decref (contract_terms);
    }
    break;
  }

  /* Resume clients that may wait for this refund */
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Awakeing clients on %s waiting for refund of less than %s\n",
              hc->infix,
              TALER_amount2s (&refund));
  TMH_long_poll_resume (hc->infix,
                        hc->instance,
                        &refund,
                        false);
  {
    struct GNUNET_TIME_Absolute timestamp;
    uint64_t order_serial;
    enum GNUNET_DB_QueryStatus qs;

    qs = TMH_db->lookup_order_summary (TMH_db->cls,
                                       hc->instance->settings.id,
                                       hc->infix,
                                       &timestamp,
                                       &order_serial);
    if (0 >= qs)
    {
      GNUNET_break (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
                                         NULL);
    }
    TMH_notify_order_change (hc->instance,
                             hc->infix,
                             true, /* paid */
                             true, /* refunded */
                             false, /* wired, cannot be if we could still do refunds */
                             timestamp,
                             order_serial);
  }
  {
    MHD_RESULT ret;
    char *taler_refund_uri;

    taler_refund_uri = make_taler_refund_uri (connection,
                                              hc->instance->settings.id,
                                              hc->infix);
    ret = TALER_MHD_REPLY_JSON_PACK (
      connection,
      MHD_HTTP_OK,
      GNUNET_JSON_pack_string ("taler_refund_uri",
                               taler_refund_uri),
      GNUNET_JSON_pack_data_auto ("h_contract",
                                  &h_contract));
    GNUNET_free (taler_refund_uri);
    return ret;
  }
}


/* end of taler-merchant-httpd_private-post-orders-ID-refund.c */