/*
  This file is part of TALER
  Copyright (C) 2015 GNUnet e.V.

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU 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, If not, see
  <http://www.gnu.org/licenses/>
*/
/**
 * @file exchange-lib/exchange_api_common.c
 * @brief common functions for the exchange API
 * @author Christian Grothoff
 */
#include "platform.h"
#include "exchange_api_common.h"
#include "taler_json_lib.h"
#include "exchange_api_context.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"


/**
 * Verify a coins transaction history as returned by the exchange.
 *
 * @param currency expected currency for the coin
 * @param coin_pub public key of the coin
 * @param history history of the coin in json encoding
 * @param[out] total how much of the coin has been spent according to @a history
 * @return #GNUNET_OK if @a history is valid, #GNUNET_SYSERR if not
 */
int
TALER_EXCHANGE_verify_coin_history_ (const char *currency,
                                 const struct TALER_CoinSpendPublicKeyP *coin_pub,
                                 json_t *history,
                                 struct TALER_Amount *total)
{
  size_t len;
  size_t off;

  if (NULL == history)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  len = json_array_size (history);
  if (0 == len)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  TALER_amount_get_zero (currency,
                         total);
  for (off=0;off<len;off++)
  {
    json_t *transaction;
    struct TALER_Amount amount;
    struct TALER_CoinSpendSignatureP sig;
    void *details;
    size_t details_size;
    const char *type;
    struct GNUNET_JSON_Specification spec[] = {
      TALER_JSON_spec_amount ("amount",
                       &amount),
      GNUNET_JSON_spec_string ("type",
                       &type),
      GNUNET_JSON_spec_fixed_auto ("signature",
                           &sig),
      GNUNET_JSON_spec_varsize ("details",
                        &details,
                        &details_size),
      GNUNET_JSON_spec_end()
    };

    transaction = json_array_get (history,
                                  off);
    if (GNUNET_OK !=
        GNUNET_JSON_parse (transaction,
                           spec,
                           NULL, NULL))
    {
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    if (0 == strcasecmp (type,
                         "DEPOSIT"))
    {
      const struct TALER_DepositRequestPS *dr;
      struct TALER_Amount dr_amount;

      if (details_size != sizeof (struct TALER_DepositRequestPS))
      {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }
      dr = (const struct TALER_DepositRequestPS *) details;
      if (details_size != ntohl (dr->purpose.size))
      {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }
      if (GNUNET_OK !=
          GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_DEPOSIT,
                                      &dr->purpose,
                                      &sig.eddsa_signature,
                                      &coin_pub->eddsa_pub))
        {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }

       // FIXME: check sig!
      TALER_amount_ntoh (&dr_amount,
                         &dr->amount_with_fee);
      if (0 != TALER_amount_cmp (&dr_amount,
                                 &amount))
        {
          GNUNET_break (0);
          GNUNET_JSON_parse_free (spec);
          return GNUNET_SYSERR;
        }
    }
    else if (0 == strcasecmp (type,
                              "MELT"))
    {
      const struct TALER_RefreshMeltCoinAffirmationPS *rm;
      struct TALER_Amount rm_amount;

      if (details_size != sizeof (struct TALER_RefreshMeltCoinAffirmationPS))
      {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }
      rm = (const struct TALER_RefreshMeltCoinAffirmationPS *) details;
      if (details_size != ntohl (rm->purpose.size))
      {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }
      if (GNUNET_OK !=
          GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_MELT,
                                      &rm->purpose,
                                      &sig.eddsa_signature,
                                      &coin_pub->eddsa_pub))
      {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }
      TALER_amount_ntoh (&rm_amount,
                         &rm->amount_with_fee);
      if (0 != TALER_amount_cmp (&rm_amount,
                                 &amount))
      {
        GNUNET_break_op (0);
        GNUNET_JSON_parse_free (spec);
        return GNUNET_SYSERR;
      }
    }
    else
    {
      /* signature not supported, new version on server? */
      GNUNET_break_op (0);
      GNUNET_JSON_parse_free (spec);
      return GNUNET_SYSERR;
    }
    if (GNUNET_OK !=
        TALER_amount_add (total,
                          total,
                          &amount))
    {
      /* overflow in history already!? inconceivable! Bad exchange! */
      GNUNET_break_op (0);
      GNUNET_JSON_parse_free (spec);
      return GNUNET_SYSERR;
    }
    GNUNET_JSON_parse_free (spec);
  }
  return GNUNET_OK;
}


/* end of exchange_api_common.c */