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

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU Lesser General Public License as published by the Free Software
  Foundation; either version 2.1, 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 Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License along with
  TALER; see the file COPYING.LGPL.  If not, see
  <http://www.gnu.org/licenses/>
*/
/**
 * @file lib/merchant_api_common.c
 * @brief Implementation of common logic for libtalermerchant
 * @author Christian Grothoff
 */
#include "platform.h"
#include <curl/curl.h>
#include <jansson.h>
#include <microhttpd.h> /* just for HTTP status codes */
#include <gnunet/gnunet_util_lib.h>
#include <gnunet/gnunet_curl_lib.h>
#include "taler_merchant_service.h"
#include <taler/taler_json_lib.h>


/**
 * Take a @a response from the merchant API that (presumably) contains
 * error details and setup the corresponding @a hr structure. Internally
 * used to convert merchant's responses in to @a hr.
 *
 * @param response, if NULL we will report #TALER_EC_INVALID_RESPONSE in `ec
 * @param http_status http status to use
 * @param[out] hr response object to initialize, fields will
 *        only be valid as long as @a response is valid as well
 */
void
TALER_MERCHANT_parse_error_details_ (const json_t *response,
                                     unsigned int http_status,
                                     struct TALER_MERCHANT_HttpResponse *hr)
{
  const json_t *jc;

  memset (hr, 0, sizeof (*hr));
  hr->reply = response;
  hr->http_status = http_status;
  if (NULL == response)
  {
    hr->ec = TALER_EC_INVALID_RESPONSE;
    return;
  }
  hr->ec = TALER_JSON_get_error_code (response);
  hr->hint = TALER_JSON_get_error_hint (response);

  /* handle 'exchange_http_status' */
  jc = json_object_get (response,
                        "exchange_http_status");
  /* The caller already knows that the JSON represents an error,
     so we are dealing with a missing error code here.  */
  if (NULL == jc)
    return; /* no need to bother with exchange_code/hint if we had no status */
  if (! json_is_integer (jc))
  {
    GNUNET_break_op (0);
    return;
  }
  hr->exchange_http_status = (unsigned int) json_integer_value (jc);

  /* handle 'exchange_reply' */
  jc = json_object_get (response,
                        "exchange_reply");
  if (! json_is_object (jc))
  {
    GNUNET_break_op (0);
  }
  else
  {
    hr->exchange_reply = jc;
  }

  /* handle 'exchange_code' */
  jc = json_object_get (response,
                        "exchange_code");
  /* The caller already knows that the JSON represents an error,
     so we are dealing with a missing error code here.  */
  if (NULL == jc)
    return; /* no need to bother with exchange-hint if we had no code */
  if (! json_is_integer (jc))
  {
    GNUNET_break_op (0);
    hr->exchange_code = TALER_EC_INVALID;
  }
  else
  {
    hr->exchange_code = (enum TALER_ErrorCode) json_integer_value (jc);
  }

  /* handle 'exchange-hint' */
  jc = json_object_get (response,
                        "exchange-hint");
  /* The caller already knows that the JSON represents an error,
     so we are dealing with a missing error code here.  */
  if (NULL == jc)
    return;
  if (! json_is_string (jc))
  {
    GNUNET_break_op (0);
  }
  else
  {
    hr->exchange_hint = json_string_value (jc);
  }
}


/**
 * Construct a new base URL using the existing @a base_url
 * and the given @a instance_id.  The result WILL end with
 * '/'.
 *
 * @param base_url a merchant base URL without "/instances/" in it,
 *         must not be the empty string; MAY end with '/'.
 * @param instance_id ID of an instance
 * @return "${base_url}/instances/${instance_id}/"
 */
char *
TALER_MERCHANT_baseurl_add_instance (const char *base_url,
                                     const char *instance_id)
{
  char *ret;
  bool end_sl;

  if ('\0' == *base_url)
  {
    GNUNET_break (0);
    return NULL;
  }
  end_sl = '/' == base_url[strlen (base_url) - 1];

  GNUNET_asprintf (&ret,
                   (end_sl)
                   ? "%sinstances/%s/"
                   : "%s/instances/%s/",
                   base_url,
                   instance_id);
  return ret;
}


/**
 * Parses the URI scheme and action of a URI. Ensures that the scheme is either
 * 'taler' or 'taler+http'.
 *
 * @param uri the uri to parse.
 * @param[out] action the action the URI is indicating.
 * @param[out] rest the substring of the URI following the action.
 * @return #GNUNET_SYSERR if the URI is malformed, #GNUNET_OK otherwise.
 */
static int
parse_taler_uri_scheme_action (const char *uri,
                               char **action,
                               char **rest)
{
  char *scheme = GNUNET_strdup (uri);
  /* Check that the uri starts with "taler://pay" or "taler+http://pay" and
     then remove it */
  char *path = strchr (scheme, ':');

  if ( (NULL == path) ||
       (strlen (path) < 3) )
  {
    GNUNET_free (scheme);
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  path += 3; /* make path point to 'pay' */

  {
    char path_begin = *path;

    *path = '\0';
    if ((0 != strcmp ("taler://",
                      scheme)) &&
        (0 != strcmp ("taler+http://",
                      scheme)))
    {
      GNUNET_free (scheme);
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    *path = path_begin;
  }

  {
    char *pqf = strchr (path, '/');

    if (NULL == pqf)
    {
      GNUNET_free (scheme);
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    *pqf = '\0';
    ++pqf;
    *rest = GNUNET_strdup (pqf);
  }
  *action = GNUNET_strdup (path);

  GNUNET_free (scheme);
  return GNUNET_OK;
}


/**
 * Extracts information from a taler://pay URI.
 *
 * @param pay_uri the URI to parse.
 * @param[out] parse_data data extracted from the URI. Must be free'd.
 * @return #GNUNET_SYSERR if @e pay_uri is malformed, #GNUNET_OK otherwise.
 */
int
TALER_MERCHANT_parse_pay_uri (const char *pay_uri,
                              struct TALER_MERCHANT_PayUriData *parse_data)
{
  char *path = NULL;
  {
    char *action = NULL;

    if ((GNUNET_OK !=
         parse_taler_uri_scheme_action (pay_uri,
                                        &action,
                                        &path)) ||
        (0 != strcmp ("pay",
                      action)))
    {
      GNUNET_break_op (0);
      GNUNET_free (action);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }
    GNUNET_free (action);
  }

  {
    char *mpp;
    char *order_id;
    char *session_id = strrchr (path,
                                '/');
    struct TALER_ClaimTokenP *claim_token = NULL;
    char *ssid;

    if (NULL == session_id)
    {
      GNUNET_break_op (0);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }
    *session_id = '\0';
    ++session_id;

    order_id = strrchr (path,
                        '/');
    if (NULL == order_id)
    {
      GNUNET_break_op (0);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }
    *order_id = '\0';
    ++order_id;

    {
      char *ct_str = strchr (session_id,
                             '?');
      char *ct_data;
      if (NULL != ct_str)
      {
        *ct_str = '\0';
        ++ct_str;
      }

      ssid = strchr (session_id,
                     '#');
      if (NULL != ssid)
      {
        *ssid = '\0';
        ++ssid;
      }

      if (NULL != ct_str)
      {
        ct_data = strchr (ct_str,
                          '=');
        if (NULL == ct_data)
        {
          GNUNET_break_op (0);
          GNUNET_free (path);
          return GNUNET_SYSERR;
        }
        *ct_data = '\0';
        ++ct_data;
        claim_token = GNUNET_new (struct TALER_ClaimTokenP);
        if ((0 != strcmp ("c",
                          ct_str)) ||
            (GNUNET_OK !=
             GNUNET_STRINGS_string_to_data (ct_data,
                                            strlen (ct_data),
                                            claim_token,
                                            sizeof (*claim_token))))
        {
          GNUNET_break_op (0);
          GNUNET_free (path);
          GNUNET_free (claim_token);
          return GNUNET_SYSERR;
        }
      }
    }

    mpp = strchr (path,
                  '/');
    if (NULL != mpp)
    {
      *mpp = '\0';
      ++mpp;
    }

    parse_data->merchant_host = GNUNET_strdup (path);
    parse_data->merchant_prefix_path =
      (NULL == mpp) ? NULL : GNUNET_strdup (mpp);
    parse_data->order_id = GNUNET_strdup (order_id);
    parse_data->session_id =
      (0 < strlen (session_id)) ? GNUNET_strdup (session_id) : NULL;
    parse_data->claim_token = claim_token;
    parse_data->ssid =
      (NULL == ssid) ? NULL : GNUNET_strdup (ssid);
  }
  GNUNET_free (path);
  return GNUNET_OK;
}


/**
 * Frees data contained in the result of parsing a taler://pay URI.
 *
 * @param parse_data the data to free.
 */
void
TALER_MERCHANT_parse_pay_uri_free (
  struct TALER_MERCHANT_PayUriData *parse_data)
{
  GNUNET_free (parse_data->merchant_host);
  GNUNET_free (parse_data->merchant_prefix_path);
  GNUNET_free (parse_data->order_id);
  GNUNET_free (parse_data->session_id);
  GNUNET_free (parse_data->claim_token);
  GNUNET_free (parse_data->ssid);
}


/**
 * Extracts information from a taler://refund URI.
 *
 * @param refund_uri the URI to parse.
 * @param[out] parse_data data extracted from the URI. Must be free'd.
 * @return #GNUNET_SYSERR if @e refund_uri is malformed, #GNUNET_OK otherwise.
 */
int
TALER_MERCHANT_parse_refund_uri (
  const char *refund_uri,
  struct TALER_MERCHANT_RefundUriData *parse_data)
{
  char *path = NULL;
  {
    char *action = NULL;

    if ((GNUNET_OK !=
         parse_taler_uri_scheme_action (refund_uri,
                                        &action,
                                        &path)) ||
        (0 != strcmp ("refund",
                      action)))
    {
      GNUNET_break_op (0);
      GNUNET_free (action);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }
    GNUNET_free (action);
  }

  {
    char *mpp;
    char *order_id;
    char *last_seg = strrchr (path,
                              '/');
    char *ssid;

    if (NULL == last_seg)
    {
      GNUNET_break_op (0);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }
    *last_seg = '\0';
    ++last_seg;

    order_id = strrchr (path,
                        '/');
    if (NULL == order_id)
    {
      GNUNET_break_op (0);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }
    *order_id = '\0';
    ++order_id;

    ssid = strchr (last_seg,
                   '#');
    if (NULL != ssid)
    {
      *ssid = '\0';
      ++ssid;
    }

    if (0 != strlen (last_seg))
    {
      GNUNET_break_op (0);
      GNUNET_free (path);
      return GNUNET_SYSERR;
    }

    mpp = strchr (path,
                  '/');
    if (NULL != mpp)
    {
      *mpp = '\0';
      ++mpp;
    }

    parse_data->merchant_host = GNUNET_strdup (path);
    parse_data->merchant_prefix_path =
      (NULL == mpp) ? NULL : GNUNET_strdup (mpp);
    parse_data->order_id = GNUNET_strdup (order_id);
    parse_data->ssid =
      (NULL == ssid) ? NULL : GNUNET_strdup (ssid);
  }
  GNUNET_free (path);
  return GNUNET_OK;
}


/**
 * Frees data contained in the result of parsing a taler://refund URI.
 *
 * @param parse_data the data to free.
 */
void
TALER_MERCHANT_parse_refund_uri_free (
  struct TALER_MERCHANT_RefundUriData *parse_data)
{
  GNUNET_free (parse_data->merchant_host);
  GNUNET_free (parse_data->merchant_prefix_path);
  GNUNET_free (parse_data->order_id);
  GNUNET_free (parse_data->ssid);
}