/*
     This file is part of GNUnet
     Copyright (C) 2013, 2014, 2016 GNUnet e.V.

     GNUnet 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 of the License,
     or (at your option) any later version.

     GNUnet 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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file reclaim/plugin_reclaim_w3c_verfiable_credential.c
 * @brief reclaim-w3c-verifiable-credential-plugin attribute plugin to provide the API for
 *                                      W3C credentials.
 * @author Tristan Schwieren
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_reclaim_plugin.h"
#include <inttypes.h>
#include <jansson.h>

/**
   * Convert the 'value' of an verifiable credential to a string.
   *
   * @param cls closure
   * @param type type of the credential
   * @param data value in binary encoding
   * @param data_size number of bytes in @a data
   * @return NULL on error, otherwise human-readable representation of the value
   */
static char *
vc_value_to_string (void *cls,
                     uint32_t type,
                     const void *data,
                     size_t data_size)
{
  switch (type)
  {
  case GNUNET_RECLAIM_CREDENTIAL_TYPE_VC:
    return GNUNET_strndup (data, data_size);
    //return "A super cool verifiable credential\n";
  default:
    return NULL;
  }
}


/**
 * Convert human-readable version of a 'value' of an credential to the binary
 * representation.
 *
 * @param cls closure
 * @param type type of the credential
 * @param s human-readable string
 * @param data set to value in binary encoding (will be allocated)
 * @param data_size set to number of bytes in @a data
 * @return #GNUNET_OK on success
 */
static int
vc_string_to_value (void *cls,
                     uint32_t type,
                     const char *s,
                     void **data,
                     size_t *data_size)
{
  if (NULL == s)
    return GNUNET_SYSERR;

  switch (type)
  {
  case GNUNET_RECLAIM_CREDENTIAL_TYPE_VC:
    *data = GNUNET_strdup (s);
    *data_size = strlen (s) + 1;
    return GNUNET_OK;

  default:
    return GNUNET_SYSERR;
  }
}


/**
 * Mapping of credential type numbers to human-readable
 * credential type names.
 */
static struct
{
  const char *name;
  uint32_t number;
} vc_cred_name_map[] = { { "VC", GNUNET_RECLAIM_CREDENTIAL_TYPE_VC},
                          { NULL, UINT32_MAX } };

/**
   * Convert a type name to the corresponding number.
   *
   * @param cls closure, unused
   * @param vc_typename name to convert
   * @return corresponding number, UINT32_MAX on error
   */
static uint32_t
vc_typename_to_number (void *cls, const char *vc_typename)
{
  unsigned int i;

  i = 0;
  while ((NULL != vc_cred_name_map[i].name) &&
         (0 != strcasecmp (vc_typename, vc_cred_name_map[i].name)))
    i++;
  return vc_cred_name_map[i].number;
}


/**
 * Convert a type number to the corresponding type string (e.g. 1 to "A")
 *
 * @param cls closure, unused
 * @param type number of a type to convert
 * @return corresponding typestring, NULL on error
 */
static const char *
vc_number_to_typename (void *cls, uint32_t type)
{
  unsigned int i;

  i = 0;
  while ((NULL != vc_cred_name_map[i].name) && (type !=
                                                 vc_cred_name_map[i].
                                                 number))
    i++;
  return vc_cred_name_map[i].name;
}


/**
 * Parse a W3C Verifiable Credential and return the respective claim value as Attribute
 * Only Works for single subject verifiable credentials
 *
 * @param cls the plugin
 * @param cred the W3C Verifiable credential
 * @return a GNUNET_RECLAIM_Attribute, containing the new value
 */
struct GNUNET_RECLAIM_AttributeList *
vc_parse_attributes (void *cls,
                      const char *cred,
                      size_t data_size)
{
  struct GNUNET_RECLAIM_AttributeList *attrs = GNUNET_new (struct GNUNET_RECLAIM_AttributeList);

  json_t * root;
  json_t * subject;
  const char * key;
  json_t * value;
  const char * value_str;

  root = json_loads(cred, JSON_DECODE_ANY, NULL);
  subject = json_object_get(root, "credentialSubject");

  if(subject == NULL)
  {
    printf("The verifiable credential has to contain a Subject\n");
    return NULL;
  }

  json_object_foreach(subject, key, value) {
      if (json_is_string(value))
      {
        value_str = json_string_value(value);

        GNUNET_RECLAIM_attribute_list_add (attrs,
                                           key,
                                           NULL,
                                           GNUNET_RECLAIM_ATTRIBUTE_TYPE_STRING,
                                           value_str,
                                           (strlen(value_str) + 1));
      }
  }

  return attrs;
}


/**
 * Parse a W3C verifiable credential and return the respective claim value as Attribute
 *
 * @param cls the plugin
 * @param cred the w3cvc credential
 * @return a GNUNET_RECLAIM_Attribute, containing the new value
 */
struct GNUNET_RECLAIM_AttributeList *
vc_parse_attributes_c (void *cls,
                        const struct GNUNET_RECLAIM_Credential *cred)
{
  if (cred->type != GNUNET_RECLAIM_CREDENTIAL_TYPE_VC)
    return NULL;
  return vc_parse_attributes (cls, cred->data, cred->data_size);
}


/**
 * Parse a W3C verifiable presentation and return the respective claim value as Attribute
 *
 * @param cls the plugin
 * @param cred the w3cvc credential
 * @return a GNUNET_RECLAIM_Attribute, containing the new value
 */
struct GNUNET_RECLAIM_AttributeList *
vc_parse_attributes_p (void *cls,
                        const struct GNUNET_RECLAIM_Presentation *cred)
{
  if (cred->type != GNUNET_RECLAIM_CREDENTIAL_TYPE_VC)
    return NULL;
  return vc_parse_attributes (cls, cred->data, cred->data_size);
}


/**
 * Parse a VC and return the issuer
 * Does not work for URI Issuer. https://www.w3.org/TR/vc-data-model/#issuer
 *
 * @param cls the plugin
 * @param cred the verifiable credential
 * @return a string, containing the isser
 */
char *
vc_get_issuer (void *cls,
                const char *cred,
                size_t data_size)
{
  json_t * root;
  json_t * issuer;
  json_t * issuer_id;
  char * issuer_id_str;

  root = json_loads(cred, JSON_DECODE_ANY, NULL);
  issuer = json_object_get(root, "credentialSubject");

  if(issuer == NULL)
  {
    printf("The verifiable credential has to contain an issuer\n");
    return NULL;
  }

  issuer_id = json_object_get(issuer, "id");

  if(issuer_id == NULL){
    printf("The issuer object of the verifiable credential has to contain an id\n");
    return NULL;
  }

  issuer_id_str = json_string_value(issuer_id);
  return GNUNET_strndup(issuer_id_str, strlen(issuer_id_str));
}


/**
 * Parse a Verifiable Credential and return the issuer
 *
 * @param cls the plugin
 * @param cred the verifiable credential
 * @return a string, containing the isser
 */
char *
vc_get_issuer_c (void *cls,
                  const struct GNUNET_RECLAIM_Credential *cred)
{
  if (GNUNET_RECLAIM_CREDENTIAL_TYPE_VC != cred->type)
    return NULL;
  return vc_get_issuer (cls, cred->data, cred->data_size);
}


/**
 * Parse a Verifiable Presentation and return the issuer
 *
 * @param cls the plugin
 * @param cred the w3cvc credential
 * @return a string, containing the isser
 */
char *
vc_get_issuer_p (void *cls,
                  const struct GNUNET_RECLAIM_Presentation *cred)
{
  if (GNUNET_RECLAIM_CREDENTIAL_TYPE_VC != cred->type)
    return NULL;
  return vc_get_issuer (cls, cred->data, cred->data_size);
}


/**
 * Parse a Verifiable Credential and return the expiration
 *
 * @param cls the plugin
 * @param cred the w3cvc credential
 * @return a string, containing the expiration
 */
enum GNUNET_GenericReturnValue
vc_get_expiration (void *cls,
                    const char *cred,
                    size_t data_size,
                    struct GNUNET_TIME_Absolute *exp)
{
  json_t * root;
  json_t * expiration_date_json;
  char * expiration_date_str;

  root = json_loads(cred, JSON_DECODE_ANY, NULL);
  expiration_date_json = json_object_get(root, "issuanceDate");

  if(expiration_date_json == NULL)
  {
    return GNUNET_NO;
  }

  // TODO: Cacluate GNUNET_TIME based on W3C datetime
  // expiration_date_str = json_string_value(expiration_date_json);
  // return GNUNET_strndup(expiration_date_str, strlen(expiration_date_str));

  exp->abs_value_us = UINT64_MAX;
  return GNUNET_OK;
}


/**
 * Parse a Verifiable Credential and return the expiration
 *
 * @param cls the plugin
 * @param cred the w3cvc credential
 * @return the expirati
 */
enum GNUNET_GenericReturnValue
vc_get_expiration_c (void *cls,
                      const struct GNUNET_RECLAIM_Credential *cred,
                      struct GNUNET_TIME_Absolute *exp)
{
  if (GNUNET_RECLAIM_CREDENTIAL_TYPE_VC != cred->type)
    return GNUNET_NO;
  return vc_get_expiration (cls, cred->data, cred->data_size, exp);
}


/**
 * Parse a verifiable credential and return the expiration
 *
 * @param cls the plugin
 * @param cred the w3cvc credential
 * @return a string, containing the isser
 */
enum GNUNET_GenericReturnValue
vc_get_expiration_p (void *cls,
                      const struct GNUNET_RECLAIM_Presentation *cred,
                      struct GNUNET_TIME_Absolute *exp)
{
  if (GNUNET_RECLAIM_CREDENTIAL_TYPE_VC  != cred->type)
    return GNUNET_NO;
  return vc_get_expiration (cls, cred->data, cred->data_size, exp);
}


enum GNUNET_GenericReturnValue
vc_create_presentation (void *cls,
                         const struct GNUNET_RECLAIM_Credential *cred,
                         const struct GNUNET_RECLAIM_AttributeList *attrs,
                         struct GNUNET_RECLAIM_Presentation **presentation)
{
  if (GNUNET_RECLAIM_CREDENTIAL_TYPE_VC != cred->type)
    return GNUNET_NO;
  *presentation = GNUNET_RECLAIM_presentation_new (
    GNUNET_RECLAIM_CREDENTIAL_TYPE_VC,
    cred->data,
    cred->data_size);
  return GNUNET_OK;
}


/**
 * Entry point for the plugin.
 *
 * @param cls NULL
 * @return the exported block API
 */
void *
libgnunet_plugin_reclaim_credential_vc_init (void *cls)
{
  struct GNUNET_RECLAIM_CredentialPluginFunctions *api;

  api = GNUNET_new (struct GNUNET_RECLAIM_CredentialPluginFunctions);
  api->value_to_string = &vc_value_to_string;
  api->string_to_value = &vc_string_to_value;
  api->typename_to_number = &vc_typename_to_number; // done
  api->number_to_typename = &vc_number_to_typename; // done
  api->get_attributes = &vc_parse_attributes_c;
  api->get_issuer = &vc_get_issuer_c;
  api->get_expiration = &vc_get_expiration_c; // not needed
  api->value_to_string_p = &vc_value_to_string;
  api->string_to_value_p = &vc_string_to_value;
  api->typename_to_number_p = &vc_typename_to_number; // done
  api->number_to_typename_p = &vc_number_to_typename; // done
  api->get_attributes_p = &vc_parse_attributes_p;
  api->get_issuer_p = &vc_get_issuer_p;
  api->get_expiration_p = &vc_get_expiration_p;
  api->create_presentation = &vc_create_presentation;
  return api;
}


/**
 * Exit point from the plugin.
 *
 * @param cls the return value from #libgnunet_plugin_block_test_init()
 * @return NULL
 */
void *
libgnunet_plugin_reclaim_credential_vc_done (void *cls)
{
  struct GNUNET_RECLAIM_CredentialPluginFunctions *api = cls;

  GNUNET_free (api);
  return NULL;
}


/* end of plugin_reclaim_w3c_verifiable_credential_type.c */