/*
  This file is part of TALER
  (C) 2024 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 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_contract.c
 * @brief shared logic for contract terms handling
 * @author Christian Blättler
 */
#include "platform.h"
#include <gnunet/gnunet_common.h>
#include <jansson.h>
#include <stdint.h>
#include "taler-merchant-httpd_contract.h"


enum TALER_MerchantContractInputType
TMH_contract_input_type_from_string (const char *str)
{
  /* For now, only 'token' is the only supported option. */
  if (0 == strcmp ("token", str))
  {
    return TALER_MCIT_TOKEN;
  }

  return TALER_MCIT_INVALID;
}


enum TALER_MerchantContractOutputType
TMH_contract_output_type_from_string (const char *str)
{
  /* For now, only 'token' is the only supported option. */
  if (0 == strcmp ("token", str))
  {
    return TALER_MCOT_TOKEN;
  }
  return TALER_MCOT_INVALID;
}


const char *
TMH_string_from_contract_input_type (enum TALER_MerchantContractInputType t)
{
  switch (t)
  {
  case TALER_MCIT_TOKEN:
    return "token";
  case TALER_MCIT_COIN:
    return "coin";
  default:
    return "invalid";
  }
}


const char *
TMH_string_from_contract_output_type (enum TALER_MerchantContractOutputType t)
{
  switch (t)
  {
  case TALER_MCOT_TOKEN:
    return "token";
  case TALER_MCOT_COIN:
    return "coin";
  case TALER_MCOT_TAX_RECEIPT:
    return "tax_receipt";
  default:
    return "invalid";
  }
}


/**
 * Parse given JSON object to choices array.
 *
 * @param cls closure, pointer to array length
 * @param root the json array representing the choices
 * @param[out] ospec where to write the data
 * @return #GNUNET_OK upon successful parsing; #GNUNET_SYSERR upon error
 */
static enum GNUNET_GenericReturnValue
parse_choices (void *cls,
               json_t *root,
               struct GNUNET_JSON_Specification *ospec)
{
  struct TALER_MerchantContractChoice **choices = ospec->ptr;
  unsigned int *choices_len = cls;

  if (! json_is_array (root))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }

  GNUNET_array_grow (*choices,
                     *choices_len,
                     json_array_size (root));

  for (unsigned int i = 0; i<*choices_len; i++)
  {
    const json_t *jinputs;
    const json_t *joutputs;
    struct GNUNET_JSON_Specification spec[] = {
      GNUNET_JSON_spec_array_const ("inputs",
                                    &jinputs),
      GNUNET_JSON_spec_array_const ("outputs",
                                    &joutputs),
      GNUNET_JSON_spec_end ()
    };
    const char *error_name;
    unsigned int error_line;
    struct TALER_MerchantContractChoice *choice = &(*choices)[i];

    if (GNUNET_OK !=
        GNUNET_JSON_parse (json_array_get (root, i),
                           spec,
                           &error_name,
                           &error_line))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  "Failed to parse %s at %u: %s\n",
                  spec[error_line].field,
                  error_line,
                  error_name);
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }

    {
      const json_t *jinput;
      size_t idx;
      json_array_foreach ((json_t *) jinputs, idx, jinput)
      {
        struct TALER_MerchantContractInput input = {.details.token.count = 1};
        const char *kind;
        struct GNUNET_JSON_Specification ispec[] = {
          GNUNET_JSON_spec_string ("kind",
                                   &kind),
          GNUNET_JSON_spec_string ("token_family_slug",
                                   &input.details.token.token_family_slug),
          GNUNET_JSON_spec_timestamp ("valid_after",
                                      &input.details.token.valid_after),
          GNUNET_JSON_spec_mark_optional (
            GNUNET_JSON_spec_uint32 ("count",
                                     &input.details.token.count),
            NULL),
          GNUNET_JSON_spec_end ()
        };
        const char *ierror_name;
        unsigned int ierror_line;

        if (GNUNET_OK !=
            GNUNET_JSON_parse (jinput,
                               ispec,
                               &ierror_name,
                               &ierror_line))
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      "Failed to parse %s at %u: %s\n",
                      ispec[ierror_line].field,
                      ierror_line,
                      ierror_name);
          GNUNET_break_op (0);
          return GNUNET_SYSERR;
        }

        input.type = TMH_contract_input_type_from_string (kind);

        if (TALER_MCIT_INVALID == input.type)
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      "Field 'kind' invalid in input #%u\n",
                      (unsigned int) idx);
          GNUNET_break_op (0);
          return GNUNET_SYSERR;
        }

        if (0 == input.details.token.count)
        {
          /* Ignore inputs with 'number' field set to 0 */
          continue;
        }

        GNUNET_array_append (choice->inputs,
                             choice->inputs_len,
                             input);
      }
    }

    {
      const json_t *joutput;
      size_t idx;
      json_array_foreach ((json_t *) joutputs, idx, joutput)
      {
        struct TALER_MerchantContractOutput output = {
          .details.token.count = 1
        };
        const char *kind;
        struct GNUNET_JSON_Specification ispec[] = {
          GNUNET_JSON_spec_string ("kind",
                                   &kind),
          GNUNET_JSON_spec_string ("token_family_slug",
                                   &output.details.token.token_family_slug),
          GNUNET_JSON_spec_timestamp ("valid_after",
                                      &output.details.token.valid_after),
          GNUNET_JSON_spec_mark_optional (
            GNUNET_JSON_spec_uint32 ("count",
                                     &output.details.token.count),
            NULL),
          GNUNET_JSON_spec_end ()
        };
        const char *ierror_name;
        unsigned int ierror_line;

        if (GNUNET_OK !=
            GNUNET_JSON_parse (joutput,
                               ispec,
                               &ierror_name,
                               &ierror_line))
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      "Failed to parse %s at %u: %s\n",
                      ispec[ierror_line].field,
                      ierror_line,
                      ierror_name);
          GNUNET_break_op (0);
          return GNUNET_SYSERR;
        }

        output.type = TMH_contract_output_type_from_string (kind);

        if (TALER_MCOT_INVALID == output.type)
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      "Field 'kind' invalid in output #%u\n",
                      (unsigned int) idx);
          GNUNET_break_op (0);
          return GNUNET_SYSERR;
        }

        if (0 == output.details.token.count)
        {
          /* Ignore outputs with 'number' field set to 0 */
          continue;
        }

        GNUNET_array_append (choice->outputs,
                             choice->outputs_len,
                             output);
      }
    }
  }
  return GNUNET_OK;
}


struct GNUNET_JSON_Specification
TALER_JSON_spec_choices (const char *name,
                         struct TALER_MerchantContractChoice **choices,
                         unsigned int *choices_len)
{
  struct GNUNET_JSON_Specification ret = {
    .cls = (void *) choices_len,
    .parser = &parse_choices,
    .field = name,
    .ptr = choices,
  };

  return ret;
}


/**
 * Parse given JSON object to token families array.
 *
 * @param cls closure, pointer to array length
 * @param root the json object representing the token families. The keys are
 *             the token family slugs.
 * @param[out] ospec where to write the data
 * @return #GNUNET_OK upon successful parsing; #GNUNET_SYSERR upon error
 */
static enum GNUNET_GenericReturnValue
parse_token_families (void *cls,
                      json_t *root,
                      struct GNUNET_JSON_Specification *ospec)
{
  struct TALER_MerchantContractTokenFamily **families = ospec->ptr;
  unsigned int *families_len = cls;
  json_t *jfamily;
  const char *slug;

  if (! json_is_object (root))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  json_object_foreach (root, slug, jfamily)
  {
    const json_t *keys;
    struct TALER_MerchantContractTokenFamily family = {
      .slug = slug
    };

    struct GNUNET_JSON_Specification spec[] = {
      GNUNET_JSON_spec_array_const ("keys",
                                    &keys),
      GNUNET_JSON_spec_bool ("critical",
                             &family.critical),
      GNUNET_JSON_spec_end ()
      /* TODO: Figure out if these fields should be 'const' */
      // GNUNET_JSON_spec_string ("description",
      //                          &family.description),
      // GNUNET_JSON_spec_object_const ("description_i18n",
      //                                &family.description_i18n),
    };
    const char *error_name;
    unsigned int error_line;

    if (GNUNET_OK !=
        GNUNET_JSON_parse (jfamily,
                           spec,
                           &error_name,
                           &error_line))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  "Failed to parse %s at %u: %s\n",
                  spec[error_line].field,
                  error_line,
                  error_name);
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }

    GNUNET_array_grow (family.keys,
                       family.keys_len,
                       json_array_size (keys));

    for (unsigned int i = 0; i<family.keys_len; i++)
    {
      /* TODO: Move this to TALER_JSON_spec_token_issue_key */
      int64_t cipher;
      struct TALER_MerchantContractTokenFamilyKey *key = &family.keys[i];
      /* TODO: Free when not used anymore */

      key->pub.public_key
        = GNUNET_new (struct GNUNET_CRYPTO_BlindSignPublicKey);
      {
        struct GNUNET_JSON_Specification key_spec[] = {
          GNUNET_JSON_spec_fixed_auto (
            "h_pub",
            &key->pub.public_key->pub_key_hash),
          GNUNET_JSON_spec_rsa_public_key (
            "rsa_pub",
            &key->pub.public_key->details.rsa_public_key),
          // FIXME: sort out CS here!
          //   GNUNET_JSON_spec_fixed_auto ("cs_pub",
          //                               &key.pub.public_key->details.cs_public_key)),
          GNUNET_JSON_spec_int64 (
            "cipher",
            &cipher),
          GNUNET_JSON_spec_timestamp (
            "valid_after",
            &key->valid_after),
          GNUNET_JSON_spec_timestamp (
            "valid_before",
            &key->valid_before),
          GNUNET_JSON_spec_end ()
        };
        const char *ierror_name;
        unsigned int ierror_line;

        if (GNUNET_OK !=
            GNUNET_JSON_parse (json_array_get (keys,
                                               i),
                               key_spec,
                               &ierror_name,
                               &ierror_line))
        {
          GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                      "Failed to parse %s at %u: %s\n",
                      key_spec[ierror_line].field,
                      ierror_line,
                      ierror_name);
          GNUNET_break_op (0);
          return GNUNET_SYSERR;
        }
      }

      switch (cipher)
      {
      case GNUNET_CRYPTO_BSA_RSA:
        key->pub.public_key->cipher = GNUNET_CRYPTO_BSA_RSA;
        break;
      case GNUNET_CRYPTO_BSA_CS:
        key->pub.public_key->cipher = GNUNET_CRYPTO_BSA_CS;
        break;
      case GNUNET_CRYPTO_BSA_INVALID:
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    "Field 'cipher' invalid in key #%u\n",
                    i);
        GNUNET_break_op (0);
        return GNUNET_SYSERR;
      }
    }
    GNUNET_array_append (*families,
                         *families_len,
                         family);
  }

  return GNUNET_OK;
}


struct GNUNET_JSON_Specification
TALER_JSON_spec_token_families (
  const char *name,
  struct TALER_MerchantContractTokenFamily **families,
  unsigned int *families_len)
{
  struct GNUNET_JSON_Specification ret = {
    .cls = (void *) families_len,
    .parser = &parse_token_families,
    .field = name,
    .ptr = families,
  };

  return ret;
}


enum GNUNET_GenericReturnValue
TMH_find_token_family_key (
  const char *slug,
  struct GNUNET_TIME_Timestamp valid_after,
  const struct TALER_MerchantContractTokenFamily *families,
  unsigned int families_len,
  struct TALER_MerchantContractTokenFamily *family,
  struct TALER_MerchantContractTokenFamilyKey *key)
{
  for (unsigned int i = 0; i < families_len; i++)
  {
    const struct TALER_MerchantContractTokenFamily *fami
      = &families[i];

    if (0 != strcmp (fami->slug,
                     slug))
      continue;
    if (NULL != family)
      *family = *fami;
    for (unsigned int k = 0; k < fami->keys_len; k++)
    {
      struct TALER_MerchantContractTokenFamilyKey *ki = &fami->keys[k];

      if (GNUNET_TIME_timestamp_cmp (ki->valid_after,
                                     ==,
                                     valid_after))
      {
        if (NULL != key)
          *key = *ki;
        return GNUNET_OK;
      }
    }
    /* matching family found, but no key. */
    return GNUNET_NO;
  }

  /* no matching family found */
  return GNUNET_NO;
}