/*
  This file is part of TALER
  (C) 2014-2020 Taler Systems SA

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

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

  You should have received a copy of the GNU General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file backend/taler-merchant-httpd_private-post-reserves-ID-authorize-tip.c
 * @brief implement API for authorizing tips to be paid to visitors
 * @author Christian Grothoff
 */
#include "platform.h"
#include <jansson.h>
#include <taler/taler_util.h>
#include <taler/taler_json_lib.h>
#include "taler-merchant-httpd.h"
#include "taler-merchant-httpd_mhd.h"
#include "taler-merchant-httpd_private-post-reserves-ID-authorize-tip.h"


/**
 * Handle a "tip-authorize" request.
 *
 * @param rh context of the handler
 * @param connection the MHD connection to handle
 * @param[in,out] hc context with further information about the request
 * @param reserve_pub reserve to use, or NULL for "any"
 * @return MHD result code
 */
static MHD_RESULT
authorize_tip (const struct TMH_RequestHandler *rh,
               struct MHD_Connection *connection,
               struct TMH_HandlerContext *hc,
               const struct TALER_ReservePublicKeyP *reserve_pub)
{
  enum TALER_ErrorCode ec;
  struct GNUNET_TIME_Absolute expiration;
  struct GNUNET_HashCode tip_id;
  const char *justification;
  const char *next_url;
  struct TALER_Amount amount;
  {
    struct GNUNET_JSON_Specification spec[] = {
      TALER_JSON_spec_amount ("amount", &amount),
      GNUNET_JSON_spec_string ("justification", &justification),
      GNUNET_JSON_spec_string ("next_url", &next_url),
      GNUNET_JSON_spec_end ()
    };
    enum GNUNET_GenericReturnValue res;

    res = TALER_MHD_parse_json_data (connection,
                                     hc->request_body,
                                     spec);
    if (GNUNET_YES != res)
    {
      GNUNET_break_op (0);
      return (GNUNET_NO == res)
             ? MHD_YES
             : MHD_NO;
    }
  }
  TMH_db->preflight (TMH_db->cls);
  ec = TMH_db->authorize_tip (TMH_db->cls,
                              hc->instance->settings.id,
                              reserve_pub,
                              &amount,
                              justification,
                              next_url,
                              &tip_id,
                              &expiration);
  /* handle errors */
  if (TALER_EC_NONE != ec)
  {
    unsigned int rc;
    const char *msg;

    switch (ec)
    {
    case TALER_EC_TIP_AUTHORIZE_INSUFFICIENT_FUNDS:
      rc = MHD_HTTP_PRECONDITION_FAILED;
      msg = "Failed to approve tip: merchant has insufficient tipping funds";
      break;
    case TALER_EC_TIP_AUTHORIZE_RESERVE_EXPIRED:
      msg = "Failed to approve tip: merchant's tipping reserve expired";
      rc = MHD_HTTP_GONE;
      break;
    case TALER_EC_TIP_AUTHORIZE_RESERVE_UNKNOWN:
      msg = "Failed to approve tip: merchant's tipping reserve does not exist";
      rc = MHD_HTTP_SERVICE_UNAVAILABLE;
      break;
    case TALER_EC_TIP_AUTHORIZE_DB_RESERVE_NOT_FOUND:
      msg = "Failed to approve tip: merchant's tipping reserve does not exist";
      rc = MHD_HTTP_NOT_FOUND;
      break;
    default:
      rc = MHD_HTTP_INTERNAL_SERVER_ERROR;
      msg = "Failed to approve tip: internal server error";
      break;
    }

    return TALER_MHD_reply_with_error (connection,
                                       rc,
                                       ec,
                                       msg);
  }

  /* generate success response */
  {
    char *taler_tip_uri;
    const char *host;
    const char *forwarded_host;
    const char *uri_path;
    struct GNUNET_CRYPTO_HashAsciiEncoded hash_enc;
    MHD_RESULT res;

    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 last the host header should be defined */
      GNUNET_break (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_INTERNAL_INVARIANT_FAILURE,
                                         "unable to identify backend host");
    }

    GNUNET_CRYPTO_hash_to_enc (&tip_id,
                               &hash_enc);
    GNUNET_assert (0 < GNUNET_asprintf (&taler_tip_uri,
                                        "taler://tip/%s/%s%sinstances/%s/%s",
                                        host,
                                        (NULL == uri_path) ? "" : uri_path,
                                        (NULL == uri_path) ? "" : "/",
                                        hc->instance->settings.id,
                                        hash_enc.encoding));
    GNUNET_TIME_round_abs (&expiration);
    res = TALER_MHD_reply_json_pack (connection,
                                     MHD_HTTP_OK,
                                     "{s:s, s:s, s:o}",
                                     "tip_id",
                                     hash_enc.encoding,
                                     "tip_redirect_url",
                                     taler_tip_uri,
                                     "tip_expiration",
                                     GNUNET_JSON_from_time_abs (expiration));
    GNUNET_free (taler_tip_uri);
    return res;
  }
}


/**
 * Handle a "/reserves/$ID/tip-authorize" request.
 *
 * @param rh context of the handler
 * @param connection the MHD connection to handle
 * @param[in,out] hc context with further information about the request
 * @return MHD result code
 */
MHD_RESULT
TMH_private_post_reserves_ID_authorize_tip (const struct TMH_RequestHandler *rh,
                                            struct MHD_Connection *connection,
                                            struct TMH_HandlerContext *hc)
{
  struct TALER_ReservePublicKeyP reserve_pub;

  if (GNUNET_OK !=
      GNUNET_STRINGS_string_to_data (hc->infix,
                                     strlen (hc->infix),
                                     &reserve_pub,
                                     sizeof (reserve_pub)))
  {
    GNUNET_break_op (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_RESERVES_INVALID_RESERVE_PUB,
                                       "reserve public key malformed");
  }
  return authorize_tip (rh,
                        connection,
                        hc,
                        &reserve_pub);
}


/**
 * Handle a POST "/tips" request.
 * Here the client does not specify the reserve public key, so we
 * are free to pick "any" available reserve.
 *
 * @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_tips (const struct TMH_RequestHandler *rh,
                       struct MHD_Connection *connection,
                       struct TMH_HandlerContext *hc)
{
  return authorize_tip (rh,
                        connection,
                        hc,
                        NULL);
}


/* end of taler-merchant-httpd_private-post-reserves-ID-authorize-tip.c */