/*
  This file is part of TALER
  Copyright (C) 2022 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 Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file taler-exchange-httpd_purses_create.c
 * @brief Handle /purses/$PID/create requests; parses the POST and JSON and
 *        verifies the coin signature before handing things off
 *        to the database.
 * @author Christian Grothoff
 */
#include "platform.h"
#include <gnunet/gnunet_util_lib.h>
#include <gnunet/gnunet_json_lib.h>
#include <jansson.h>
#include <microhttpd.h>
#include <pthread.h>
#include "taler_json_lib.h"
#include "taler_mhd_lib.h"
#include "taler-exchange-httpd_purses_create.h"
#include "taler-exchange-httpd_responses.h"
#include "taler_exchangedb_lib.h"
#include "taler-exchange-httpd_keys.h"


/**
 * Information about an individual coin being deposited.
 */
struct Coin
{
  /**
   * Public information about the coin.
   */
  struct TALER_CoinPublicInfo cpi;

  /**
   * Signature affirming spending the coin.
   */
  struct TALER_CoinSpendSignatureP coin_sig;

  /**
   * Amount to be put into the purse from this coin.
   */
  struct TALER_Amount amount;

  /**
   * Deposit fee applicable for this coin.
   */
  struct TALER_Amount deposit_fee;
};


/**
 * Closure for #create_transaction.
 */
struct PurseCreateContext
{
  /**
   * Public key of the purse we are creating.
   */
  const struct TALER_PurseContractPublicKeyP *purse_pub;

  /**
   * Total amount to be put into the purse.
   */
  struct TALER_Amount amount;

  /**
   * Total actually deposited by all the coins.
   */
  struct TALER_Amount deposit_total;

  /**
   * When should the purse expire.
   */
  struct GNUNET_TIME_Timestamp purse_expiration;

  /**
   * Our current time.
   */
  struct GNUNET_TIME_Timestamp exchange_timestamp;

  /**
   * Merge key for the purse.
   */
  struct TALER_PurseMergePublicKeyP merge_pub;

  /**
   * Contract decryption key for the purse.
   */
  struct TALER_ContractDiffiePublicP contract_pub;

  /**
   * Signature of the client affiming this request.
   */
  struct TALER_PurseContractSignatureP purse_sig;

  /**
   * Hash of the contract terms of the purse.
   */
  struct TALER_PrivateContractHashP h_contract_terms;

  /**
   * Array of coins being deposited.
   */
  struct Coin *coins;

  /**
   * Encrypted contract, can be NULL.
   */
  void *econtract;

  /**
   * Number of bytes in @e econtract.
   */
  size_t econtract_size;

  /**
   * Length of the @e coins array.
   */
  unsigned int num_coins;

};


/**
 * Send confirmation of purse creation success to client.
 *
 * @param connection connection to the client
 * @param pcc details about the request that succeeded
 * @return MHD result code
 */
static MHD_RESULT
reply_create_success (struct MHD_Connection *connection,
                      const struct PurseCreateContext *pcc)
{
  struct TALER_ExchangePublicKeyP pub;
  struct TALER_ExchangeSignatureP sig;
  // FIXME: define what exactly we sign over!
  struct TALER_DepositConfirmationPS dc = {
    .purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_CREATION),
    .purpose.size = htonl (sizeof (dc)),
    .h_contract_terms = pcc->h_contract_terms,
    .purse_pub = *pcc->purse_pub
  };
  enum TALER_ErrorCode ec;

  TALER_amount_hton (&dc.amount_without_fee,
                     &pcc->amount);
  if (TALER_EC_NONE !=
      (ec = TEH_keys_exchange_sign (&dc,
                                    &pub,
                                    &sig)))
  {
    return TALER_MHD_reply_with_ec (connection,
                                    ec,
                                    NULL);
  }
  return TALER_MHD_REPLY_JSON_PACK (
    connection,
    MHD_HTTP_OK,
    // GNUNET_JSON_pack_timestamp ("exchange_timestamp",
    // pcc->exchange_timestamp),
    GNUNET_JSON_pack_data_auto ("exchange_sig",
                                &sig),
    GNUNET_JSON_pack_data_auto ("exchange_pub",
                                &pub));
}


/**
 * Execute database transaction for /purses/$PID/create.  Runs the transaction
 * logic; IF it returns a non-error code, the transaction logic MUST NOT queue
 * a MHD response.  IF it returns an hard error, the transaction logic MUST
 * queue a MHD response and set @a mhd_ret.  IF it returns the soft error
 * code, the function MAY be called again to retry and MUST not queue a MHD
 * response.
 *
 * @param cls a `struct PurseCreateContext`
 * @param connection MHD request context
 * @param[out] mhd_ret set to MHD status on error
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
create_transaction (void *cls,
                    struct MHD_Connection *connection,
                    MHD_RESULT *mhd_ret)
{
  struct PurseCreateContext *pcc = cls;
  enum GNUNET_DB_QueryStatus qs;
  bool balance_ok;
  bool in_conflict;

  // 1) create purse
  // 2) deposit all coins
  // 3) if present, persist contract
  // Also: nicely report errors...
  qs = TEH_plugin->XXX (TEH_plugin->cls, ...);
  if (qs < 0)
  {
    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
      return qs;
    TALER_LOG_WARNING ("Failed to store purse information in database\n");
    *mhd_ret = TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_GENERIC_DB_STORE_FAILED,
                                           "purse create");
    return qs;
  }
  if (in_conflict)
  {
    TEH_plugin->rollback (TEH_plugin->cls);
    *mhd_ret
      = TEH_RESPONSE_reply_coin_insufficient_funds (
          connection,
          TALER_EC_EXCHANGE_PURSE_CREATE_CONFLICTING_CONTRACT,
          &coin->pci.coin_pub);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  if (! balance_ok)
  {
    TEH_plugin->rollback (TEH_plugin->cls);
    *mhd_ret
      = TEH_RESPONSE_reply_coin_insufficient_funds (
          connection,
          TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS,
          &coin->pci.coin_pub);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  return qs;
}


/**
 * Parse a coin and check signature of the coin and the denomination
 * signature over the coin.
 *
 * @param[in,out] our HTTP connection
 * @param[in,out] request context
 * @param[out] coin coin to initialize
 * @param jcoin coin to parse
 * @return #GNUNET_OK on success, #GNUNET_NO if an error was returned,
 *         #GNUNET_SYSERR on failure and no error could be returned
 */
static enum GNUNET_GenericReturnValue
parse_coin (struct MHD_Connection *connection,
            struct PurseCreateContext *pcc,
            struct Coin *coin,
            const json_t *jcoin)
{
  struct GNUNET_JSON_Specification spec[] = {
    TALER_JSON_spec_amount ("amount",
                            TEH_currency,
                            &coin->amount),
    GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
                                 &coin->cpi.denom_pub_hash),
    TALER_JSON_spec_denom_sig ("ub_sig",
                               &coin->cpi.denom_sig),
    GNUNET_JSON_spec_mark_optional (
      GNUNET_JSON_spec_fixed_auto ("h_age_commitment",
                                   &coin->cpi.h_age_commitment)),
    &coin->cpi.no_age_commitment),
    GNUNET_JSON_spec_fixed_auto ("coin_sig",
                                 &coin->coin_sig),
    GNUNET_JSON_spec_fixed_auto ("coin_pub",
                                 &coin->cpi.coin_pub),
    GNUNET_JSON_spec_end ()
  };

  {
    enum GNUNET_GenericReturnValue res;

    res = TALER_MHD_parse_json_data (connection,
                                     jcoin,
                                     spec);
    if (GNUNET_OK != res)
      return res;
  }

  if (GNUNET_OK !=
      TALER_wallet_purse_deposit_verify ("http://FIXME-URL",
                                         &pcc->purse_pub,
                                         &pcc->amount,
                                         &coin->coin_pub,
                                         &coin->csig))
  {
    TALER_LOG_WARNING ("Invalid signature on /purses/$PID/create request\n");
    GNUNET_JSON_parse_free (spec);
    return (MHD_YES ==
            TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_UNAUTHORIZED,
                                        TALER_EC_EXCHANGE_PURSE_CREATE_COIN_SIGNATURE_INVALID,
                                        NULL))
           ? GNUNET_NO : GNUNET_SYSERR;
  }
  /* check denomination exists and is valid */
  {
    struct TEH_DenominationKey *dk;
    MHD_RESULT mret;

    dk = TEH_keys_denomination_by_hash (&coin->denom_pub_hash,
                                        connection,
                                        &mret);
    if (NULL == dk)
    {
      GNUNET_JSON_parse_free (spec);
      return (MHD_YES == mret) ? GNUNET_NO : GNUNET_SYSERR:
    }
    if (GNUNET_TIME_absolute_is_past (dk->meta.expire_deposit.abs_time))
    {
      /* This denomination is past the expiration time for deposits */
      GNUNET_JSON_parse_free (spec);
      return (MHD_YES ==
              TEH_RESPONSE_reply_expired_denom_pub_hash (
                connection,
                &coin->denom_pub_hash,
                TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
                "PURSE CREATE"))
             ? GNUNET_NO : GNUNET_SYSERR:
    }
    if (GNUNET_TIME_absolute_is_future (dk->meta.start.abs_time))
    {
      /* This denomination is not yet valid */
      GNUNET_JSON_parse_free (spec);
      return (MHD_YES ==
              TEH_RESPONSE_reply_expired_denom_pub_hash (
                connection,
                &coin->denom_pub_hash,
                TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
                "PURSE CREATE"))
             ? GNUNET_NO : GNUNET_SYSERR;
    }
    if (dk->recoup_possible)
    {
      /* This denomination has been revoked */
      GNUNET_JSON_parse_free (spec);
      return (MHD_YES ==
              TEH_RESPONSE_reply_expired_denom_pub_hash (
                connection,
                &deposit.coin.denom_pub_hash,
                TALER_EC_EXCHANGE_GENERIC_DENOMINATION_REVOKED,
                "PURSE CREATE"))
             ? GNUNET_NO : GNUNET_SYSERR;
    }
    if (dk->denom_pub.cipher != deposit.coin.denom_sig.cipher)
    {
      /* denomination cipher and denomination signature cipher not the same */
      GNUNET_JSON_parse_free (spec);
      return (MHD_YES ==
              TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
                                          TALER_EC_EXCHANGE_GENERIC_CIPHER_MISMATCH,
                                          NULL))
             ? GNUNET_NO : GNUNET_SYSERR;
    }

    coin->deposit_fee = dk->meta.fees.deposit;
    /* check coin signature */
    switch (dk->denom_pub.cipher)
    {
    case TALER_DENOMINATION_RSA:
      TEH_METRICS_num_verifications[TEH_MT_SIGNATURE_RSA]++;
      break;
    case TALER_DENOMINATION_CS:
      TEH_METRICS_num_verifications[TEH_MT_SIGNATURE_CS]++;
      break;
    default:
      break;
    }
    if (GNUNET_YES !=
        TALER_test_coin_valid (&deposit.coin,
                               &dk->denom_pub))
    {
      TALER_LOG_WARNING ("Invalid coin passed for /deposit\n");
      GNUNET_JSON_parse_free (spec);
      return (MHD_YES ==
              TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_UNAUTHORIZED,
                                          TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
                                          NULL))
             ? GNUNET_NO : GNUNET_SYSERR;
    }
  }
  {
    MHD_RESULT mhd_ret = MHD_NO;
    enum GNUNET_DB_QueryStatus qs;

    /* make sure coin is 'known' in database */
    for (unsigned int tries = 0; tries<MAX_TRANSACTION_COMMIT_RETRIES; tries++)
    {
      qs = TEH_make_coin_known (&deposit.coin,
                                connection,
                                &pcc.known_coin_id,
                                &mhd_ret);
      /* no transaction => no serialization failures should be possible */
      if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
        break;
    }
    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
    {
      GNUNET_break (0);
      return (MHD_YES ==
              TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
                                          TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                          "make_coin_known"))
             ? GNUNET_NO : GNUNET_SYSERR;
    }
    if (qs < 0)
      return (MHD_YES == mhd_ret) ? GNUNET_NO : GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


MHD_RESULT
TEH_handler_purses_create (struct MHD_Connection *connection,
                           const struct
                           TALER_PurseContractPublicKeyP *purse_pub,
                           const json_t *root)
{
  struct PurseCreateContext pcc = {
    .purse_pub = purse_pub,
    .exchange_timestamp = GNUNET_TIME_timestamp_get ();
  };
  json_t *deposits;
  json_t *deposit;
  unsigned int idx;
  struct GNUNET_JSON_Specification spec[] = {
    TALER_JSON_spec_amount ("amount",
                            TEH_currency,
                            &pcc.amount),
    GNUNET_JSON_spec_uint32 ("min_age",
                             &pcc.min_age),
    GNUNET_JSON_spec_mark_optional (
      GNUNET_JSON_spec_var_size ("econtract",
                                 &pcc.econtract,
                                 &pcc.ecotract_size)),
    GNUNET_JSON_spec_fixed_auto ("contract_pub",
                                 &pcc.contract_pub),
    GNUNET_JSON_spec_fixed_auto ("merge_pub",
                                 &pcc.merge_pub),
    GNUNET_JSON_spec_fixed_auto ("purse_sig",
                                 &pcc.purse_sig),
    GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
                                 &pcc.h_contract_terms),
    GNUNET_JSON_spec_json ("deposits",
                           &deposits),
    GNUNET_JSON_spec_timestamp ("purse_expiration",
                                &pcc.purse_expiration),
    GNUNET_JSON_spec_end ()
  };

  {
    enum GNUNET_GenericReturnValue res;

    res = TALER_MHD_parse_json_data (connection,
                                     root,
                                     spec);
    if (GNUNET_SYSERR == res)
    {
      GNUNET_break (0);
      return MHD_NO; /* hard failure */
    }
    if (GNUNET_NO == res)
    {
      GNUNET_break_op (0);
      return MHD_YES; /* failure */
    }
  }

  if (GNUNET_TIME_timestamp_cmp (pcc.purse_expiration,
                                 <,
                                 pcc.exchange_timestamp))
  {
    GNUNET_break_op (0);
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_EXCHANGE_PURSE_CREATE_EXPIRATION_BEFORE_NOW,
                                       NULL);
  }
  if (GNUNET_TIME_absolute_is_never (pcc.purse_expiration.abs_time))
  {
    GNUNET_break_op (0);
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_EXCHANGE_PURSE_CREATE_EXPIRATION_IS_NEVER,
                                       NULL);
  }
  pcc.num_coins = json_array_size (deposits);
  if ( (0 == pcc.num_coins) ||
       (pcc.num_coins > TALER_MAX_FRESH_COINS) )
  {
    GNUNET_break_op (0);
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_EXCHANGE_GENERIC_PARAMETER_MALFORMED,
                                       "deposits");
  }
  /* parse deposits */
  pcc.coins = GNUNET_new_array (struct Coin,
                                pcc.num_coins);
  json_array_foreach (deposits, idx, deposit)
  {
    enum GNUNET_GenericReturnValue res;
    struct Coin *coin = &pcc.coins[idx];

    res = parse_coin (connection,
                      &pcc,
                      coin,
                      deposit);
    if (GNUNET_OK != res)
    {
      GNUNET_JSON_parse_free (spec);
      GNUNET_free (pcc.coins);
      return (GNUNET_NO == res) ? MHD_YES : MHD_NO;
    }
  }

  // FIXME: get purse_fee!
  if (0 < TALER_amount_cmp (&purse_fee,
                            &pcc.deposit_total))
  {
    GNUNET_break_op (0);
    GNUNET_JSON_parse_free (spec);
    GNUNET_free (pcc.coins);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_EXCHANGE_CREATE_PURSE_NEGATIVE_VALUE_AFTER_FEE,
                                       NULL);
  }

  TEH_METRICS_num_verifications[TEH_MT_SIGNATURE_EDDSA]++;

  if (GNUNET_OK !=
      TALER_wallet_purse_create_verify (&pcc.purse_expiration,
                                        &pcc.h_contract_terms,
                                        &pcc.merge_pub,
                                        pcc.min_age,
                                        &pcc.amount,
                                        &pcc.purse_pub,
                                        &pcc.purse_sig))
  {
    TALER_LOG_WARNING ("Invalid signature on /purses/$PID/create request\n");
    GNUNET_JSON_parse_free (spec);
    GNUNET_free (pcc.coins);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_UNAUTHORIZED,
                                       TALER_EC_EXCHANGE_PURSE_CREATE_COIN_SIGNATURE_INVALID,
                                       NULL);
  }

  if (GNUNET_SYSERR ==
      TEH_plugin->preflight (TEH_plugin->cls))
  {
    GNUNET_break (0);
    GNUNET_free (pcc.coins);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_GENERIC_DB_START_FAILED,
                                       "preflight failure");
  }

  /* execute transaction */
  {
    MHD_RESULT mhd_ret;

    if (GNUNET_OK !=
        TEH_DB_run_transaction (connection,
                                "execute purse create",
                                TEH_MT_REQUEST_PURSE_CREATE,
                                &mhd_ret,
                                &create_transaction,
                                &pcc))
    {
      GNUNET_JSON_parse_free (spec);
      GNUNET_free (pcc.coins);
      return mhd_ret;
    }
  }

  /* generate regular response */
  {
    MHD_RESULT res;

    res = reply_create_success (connection,
                                &pcc);
    GNUNET_free (pcc.coins);
    GNUNET_JSON_parse_free (spec);
    return res;
  }
}


/* end of taler-exchange-httpd_purses_create.c */