/*
  This file is part of TALER
  (C) 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-patch-orders-ID-forget.c
 * @brief implementing PATCH /orders/$ORDER_ID/forget request handling
 * @author Jonathan Buchanan
 */
#include "platform.h"
#include "taler-merchant-httpd_private-patch-instances-ID.h"
#include <taler/taler_json_lib.h>


/**
 * Parse a json path, using the syntax defined in the spec for this method.
 * @param obj the root object the path applies to.
 * @param path the path to find.
 *
 * @return the object pointed to by @e path if it exists, NULL otherwise.
 */
static int
forget_field (json_t *obj,
              json_t *prev,
              const char *field)
{
  /* FIXME: Handle nonexistent paths */
  /* FIXME: If prev is NULL, check that the string starts with $ */
  char *id = GNUNET_strdup (field);
  char *next_id = strchr (id,
                          '.');
  json_t *next_obj = NULL;
  int ret;

  if (NULL != next_id)
  {
    *next_id = '\0';
    next_id++;
  }
  else
  {
    return TALER_JSON_contract_part_forget (prev,
                                            id);
  }

  // Check for bracketed indices
  char *bracket = strchr (id,
                          '[');
  if (NULL != bracket)
  {
    char *end_bracket = strchr (bracket,
                                ']');
    if (NULL == end_bracket)
      return GNUNET_SYSERR;
    *end_bracket = '\0';

    *bracket = '\0';
    bracket++;

    json_t *arr = json_object_get (obj,
                                   id);
    if (0 == strcmp (bracket,
                     "*"))
    {
      /* FIXME: Handle wildcard expansion */
    }
    else
    {
      unsigned int index;
      if (1 != sscanf (bracket,
                       "%u",
                       &index))
        return GNUNET_SYSERR;

      next_obj = json_array_get (arr,
                                 index);
    }
  }
  else
  {
    // No brackets, so just fetch the object by name
    next_obj = json_object_get (obj,
                                next_id);
  }

  ret = forget_field (next_obj,
                      obj,
                      next_id);

  GNUNET_free (id);

  return ret;
}


/**
 * Forget fields of an order's contract terms.
 *
 * @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_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
                                    struct MHD_Connection *connection,
                                    struct TMH_HandlerContext *hc)
{
  const char *order_id = hc->infix;
  enum GNUNET_DB_QueryStatus qs;
  json_t *fields;
  json_t *contract_terms;
  uint64_t order_serial;

  qs = TMH_db->lookup_contract_terms (TMH_db->cls,
                                      hc->instance->settings.id,
                                      order_id,
                                      &contract_terms,
                                      &order_serial);
  switch (qs)
  {
  case GNUNET_DB_STATUS_HARD_ERROR:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_ORDERS_CLAIM_HARD_DB_ERROR,
                                       "Failed to run DB transaction to lookup order");
  case GNUNET_DB_STATUS_SOFT_ERROR:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_ORDERS_CLAIM_SOFT_DB_ERROR,
                                       "Failed to serialize DB transaction to lookup order");
  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_NOT_FOUND,
                                       TALER_EC_FORGET_ORDER_NOT_FOUND,
                                       "unknown order id");
  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
    GNUNET_assert (NULL != contract_terms);
    break;
  }

  {
    struct GNUNET_JSON_Specification spec[] = {
      GNUNET_JSON_spec_json ("fields",
                             &fields),
      GNUNET_JSON_spec_end ()
    };
    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;
  }
  if ( !(json_is_array (fields)))
  {
    json_decref (contract_terms);
    json_decref (fields);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_PARAMETER_MALFORMED,
                                       "paths");
  }

  {
    size_t index;
    json_t *value;
    json_array_foreach (fields, index, value) {
      int forget_status;
      if ( !(json_is_string (value)))
      {
        json_decref (contract_terms);
        json_decref (fields);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_BAD_REQUEST,
                                           TALER_EC_FORGET_PATH_SYNTAX_INCORRECT,
                                           "field isn't a string");
      }
      // Check that the field starts with "$."
      forget_status = forget_field (contract_terms,
                                    NULL,
                                    json_string_value (value));
      if (GNUNET_SYSERR == forget_status)
      {
        /* We tried to forget a field that isn't forgettable */
        json_decref (contract_terms);
        json_decref (fields);
        return TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_CONFLICT,
                                           TALER_EC_FORGET_PATH_NOT_FORGETTABLE,
                                           "field isn't forgettable");
      }
    }
  }

  qs = TMH_db->update_contract_terms (TMH_db->cls,
                                      hc->instance->settings.id,
                                      order_id,
                                      contract_terms);

  switch (qs)
  {
  case GNUNET_DB_STATUS_HARD_ERROR:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_ORDERS_CLAIM_HARD_DB_ERROR,
                                       "Failed to run DB transaction to update contract terms");
  case GNUNET_DB_STATUS_SOFT_ERROR:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_ORDERS_CLAIM_SOFT_DB_ERROR,
                                       "Failed to serialize DB transaction to update contract terms");
  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_NOT_FOUND,
                                       TALER_EC_FORGET_ORDER_NOT_FOUND,
                                       "unknown order id");
  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
    break;
  }

  json_decref (contract_terms);
  json_decref (fields);

  return TALER_MHD_reply_static (connection,
                                 MHD_HTTP_OK,
                                 NULL,
                                 NULL,
                                 0);
}