/*
  This file is part of TALER
  (C) 2014, 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 merchant/backend/taler-merchant-httpd.c
 * @brief HTTP serving layer intended to perform crypto-work and
 * communication with the exchange
 * @author Marcello Stanisci
 * @author Christian Grothoff
 */
#include "platform.h"
#include <microhttpd.h>
#include <jansson.h>
#include <gnunet/gnunet_util_lib.h>
#include <taler/taler_util.h>
#include <taler/taler_exchange_service.h>
#include "taler-merchant-httpd_parsing.h"
#include "taler-merchant-httpd_responses.h"
#include "taler_merchantdb_lib.h"
#include "taler-merchant-httpd.h"
#include "taler-merchant-httpd_mhd.h"
#include "taler-merchant-httpd_auditors.h"
#include "taler-merchant-httpd_exchanges.h"
#include "taler-merchant-httpd_contract.h"
#include "taler-merchant-httpd_pay.h"
#include "taler-merchant-httpd_util.h"



/**
 * Our wire format details in JSON format (with salt).
 */
struct json_t *j_wire;

/**
 * Hash of our wire format details as given in #j_wire.
 */
struct GNUNET_HashCode h_wire;

/**
 * Merchant's private key
 */
struct GNUNET_CRYPTO_EddsaPrivateKey *privkey;

/**
 * Merchant's public key
 */
struct TALER_MerchantPublicKeyP pubkey;

/**
 * Our hostname
 */
static char *hostname;

/**
 * The port we are running on
 */
static long long unsigned port;

/**
 * File holding the merchant's private key
 */
static char *keyfile;

/**
 * This value tells the exchange by which date this merchant would like
 * to receive the funds for a deposited payment
 */
struct GNUNET_TIME_Relative edate_delay;

/**
 * Which currency is supported by this merchant?
 */
char *TMH_merchant_currency_string;

/**
 * Shutdown task identifier
 */
static struct GNUNET_SCHEDULER_Task *shutdown_task;

/**
 * Task running the HTTP server.
 */
static struct GNUNET_SCHEDULER_Task *mhd_task;

/**
 * Should we do a dry run where temporary tables are used for storing the data.
 */
static int dry;

/**
 * Global return code
 */
static int result;

/**
 * Connection handle to the our database
 */
struct TALER_MERCHANTDB_Plugin *db;

/**
 * The MHD Daemon
 */
static struct MHD_Daemon *mhd;


/**
 * A client has requested the given url using the given method
 * (#MHD_HTTP_METHOD_GET, #MHD_HTTP_METHOD_PUT,
 * #MHD_HTTP_METHOD_DELETE, #MHD_HTTP_METHOD_POST, etc).  The callback
 * must call MHD callbacks to provide content to give back to the
 * client and return an HTTP status code (i.e. #MHD_HTTP_OK,
 * #MHD_HTTP_NOT_FOUND, etc.).
 *
 * @param cls argument given together with the function
 *        pointer when the handler was registered with MHD
 * @param url the requested url
 * @param method the HTTP method used (#MHD_HTTP_METHOD_GET,
 *        #MHD_HTTP_METHOD_PUT, etc.)
 * @param version the HTTP version string (i.e.
 *        #MHD_HTTP_VERSION_1_1)
 * @param upload_data the data being uploaded (excluding HEADERS,
 *        for a POST that fits into memory and that is encoded
 *        with a supported encoding, the POST data will NOT be
 *        given in upload_data and is instead available as
 *        part of #MHD_get_connection_values; very large POST
 *        data *will* be made available incrementally in
 *        @a upload_data)
 * @param upload_data_size set initially to the size of the
 *        @a upload_data provided; the method must update this
 *        value to the number of bytes NOT processed;
 * @param con_cls pointer that the callback can set to some
 *        address and that will be preserved by MHD for future
 *        calls for this request; since the access handler may
 *        be called many times (i.e., for a PUT/POST operation
 *        with plenty of upload data) this allows the application
 *        to easily associate some request-specific state.
 *        If necessary, this state can be cleaned up in the
 *        global #MHD_RequestCompletedCallback (which
 *        can be set with the #MHD_OPTION_NOTIFY_COMPLETED).
 *        Initially, `*con_cls` will be NULL.
 * @return #MHD_YES if the connection was handled successfully,
 *         #MHD_NO if the socket must be closed due to a serios
 *         error while handling the request
 */
static int
url_handler (void *cls,
             struct MHD_Connection *connection,
             const char *url,
             const char *method,
             const char *version,
             const char *upload_data,
             size_t *upload_data_size,
             void **con_cls)
{
  static struct TMH_RequestHandler handlers[] =
    {
      /* Landing page, tell humans to go away. */
      { "/", MHD_HTTP_METHOD_GET, "text/plain",
        "Hello, I'm a merchant's Taler backend. This HTTP server is not for humans.\n", 0,
        &TMH_MHD_handler_static_response, MHD_HTTP_OK },
      { "/hash-contract", MHD_HTTP_METHOD_POST, "application/json",
        NULL, 0,
        &MH_handler_hash_contract, MHD_HTTP_OK },
      { "/hash-contract", NULL, "text/plain",
        "Only POST is allowed", 0,
        &TMH_MHD_handler_send_json_pack_error, MHD_HTTP_METHOD_NOT_ALLOWED },
      { "/contract", MHD_HTTP_METHOD_POST, "application/json",
        NULL, 0,
        &MH_handler_contract, MHD_HTTP_OK },
      { "/contract", NULL, "text/plain",
        "Only POST is allowed", 0,
        &TMH_MHD_handler_send_json_pack_error, MHD_HTTP_METHOD_NOT_ALLOWED },

      { "/pay", MHD_HTTP_METHOD_POST, "application/json",
        NULL, 0,
        &MH_handler_pay, MHD_HTTP_OK },
      { "/pay", NULL, "text/plain",
        "Only POST is allowed", 0,
        &TMH_MHD_handler_send_json_pack_error, MHD_HTTP_METHOD_NOT_ALLOWED },

      {NULL, NULL, NULL, NULL, 0, 0 }
    };
  static struct TMH_RequestHandler h404 =
    {
      "", NULL, "text/html",
      "<html><title>404: not found</title></html>", 0,
      &TMH_MHD_handler_static_response, MHD_HTTP_NOT_FOUND
    };
  struct TMH_RequestHandler *rh;
  unsigned int i;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Handling request for URL `%s'\n",
              url);
  for (i=0;NULL != handlers[i].url;i++)
  {
    rh = &handlers[i];
    if ( (0 == strcasecmp (url,
                           rh->url)) &&
         ( (NULL == rh->method) ||
           (0 == strcasecmp (method,
                             rh->method)) ) )
      return rh->handler (rh,
                          connection,
                          con_cls,
                          upload_data,
                          upload_data_size);
  }
  return TMH_MHD_handler_static_response (&h404,
                                          connection,
                                          con_cls,
                                          upload_data,
                                          upload_data_size);
}


/**
 * Shutdown task (magically invoked when the application is being
 * quit)
 *
 * @param cls NULL
 * @param tc scheduler task context
 */
static void
do_shutdown (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  if (NULL != mhd_task)
  {
    GNUNET_SCHEDULER_cancel (mhd_task);
    mhd_task = NULL;
  }
  if (NULL != mhd)
  {
    MHD_stop_daemon (mhd);
    mhd = NULL;
  }
  if (NULL != db)
  {
    TALER_MERCHANTDB_plugin_unload (db);
    db = NULL;
  }
  TMH_EXCHANGES_done ();
  TMH_AUDITORS_done ();
  if (NULL != keyfile)
    GNUNET_free (privkey);
}


/**
 * Function called whenever MHD is done with a request.  If the
 * request was a POST, we may have stored a `struct Buffer *` in the
 * @a con_cls that might still need to be cleaned up.  Call the
 * respective function to free the memory.
 *
 * @param cls client-defined closure
 * @param connection connection handle
 * @param con_cls value as set by the last call to
 *        the #MHD_AccessHandlerCallback
 * @param toe reason for request termination
 * @see #MHD_OPTION_NOTIFY_COMPLETED
 * @ingroup request
 */
static void
handle_mhd_completion_callback (void *cls,
                                struct MHD_Connection *connection,
                                void **con_cls,
                                enum MHD_RequestTerminationCode toe)
{
  struct TM_HandlerContext *hc = *con_cls; /* 'hc' is also a 'struct PayContext' */

  if (NULL == hc)
    return;
  hc->cc (hc);
  *con_cls = NULL;
}


/**
 * Function that queries MHD's select sets and
 * starts the task waiting for them.
 */
static struct GNUNET_SCHEDULER_Task *
prepare_daemon (void);


/**
 * Call MHD to process pending requests and then go back
 * and schedule the next run.
 *
 * @param cls the `struct MHD_Daemon` of the HTTP server to run
 * @param tc scheduler context
 */
static void
run_daemon (void *cls,
            const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  mhd_task = NULL;
  GNUNET_assert (MHD_YES == MHD_run (mhd));
  mhd_task = prepare_daemon ();
}


/**
 * Kick MHD to run now, to be called after MHD_resume_connection().
 * Basically, we need to explicitly resume MHD's event loop whenever
 * we made progress serving a request.  This function re-schedules
 * the task processing MHD's activities to run immediately.
 */
void
TMH_trigger_daemon ()
{
  GNUNET_SCHEDULER_cancel (mhd_task);
  run_daemon (NULL, NULL);
}

/**
 * Parse the TEST wireformat information from the configuration.
 * If any of the required fields is missing return an error.
 *
 * @param cfg the configuration
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
static int
parse_wireformat_test (const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  unsigned long long account_number;
  
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number(cfg,
                                            "wire-test",
					    "ACCOUNT_NUMBER",
					    &account_number))
    return GNUNET_SYSERR;
  j_wire = json_pack("{s:s, s:I}",
                     "type", "TEST",
		     "account_number", (json_int_t) account_number);
  if (NULL == j_wire)
    return GNUNET_SYSERR;
  return GNUNET_OK;

}


/**
 * Parse the SEPA information from the configuration.  If any of the
 * required fields is missing return an error.
 *
 * @param cfg the configuration
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
static int
parse_wireformat_sepa (const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  unsigned long long salt;
  char *iban;
  char *name;
  char *address;
  char *bic;

  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number (cfg,
                                             "wire-sepa",
                                             "SALT",
                                             &salt))
  {
    salt = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_NONCE,
                                     UINT64_MAX);
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "No SALT option given in `wire-sepa`, using %llu\n",
                (unsigned long long) salt);
  }
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             "wire-sepa",
                                             "IBAN",
                                             &iban))
    return GNUNET_SYSERR;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             "wire-sepa",
                                             "NAME",
                                             &name))
  {
    GNUNET_free (iban);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             "wire-sepa",
                                             "ADDRESS",
                                             &address))
  {
    GNUNET_free (iban);
    GNUNET_free (name);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             "wire-sepa",
                                             "BIC",
                                             &bic))
  {
    GNUNET_free (iban);
    GNUNET_free (name);
    GNUNET_free (bic);
    GNUNET_free (address);
    return GNUNET_SYSERR;
  }
  j_wire = json_pack ("{s:s, s:s, s:s, s:s, s:o, s:s}",
                      "type", "SEPA",
                      "IBAN", iban,
                      "name", name,
                      "bic", bic,
                      "r", json_integer (salt),
		      "address", address);
  GNUNET_free (iban);
  GNUNET_free (name);
  GNUNET_free (address);
  GNUNET_free (bic);
  if (NULL == j_wire)
    return GNUNET_SYSERR;
  return GNUNET_OK;
}


/**
 * Verify that #j_wire contains a well-formed wire format, and
 * update #h_wire to match it (if successful).
 *
 * @param allowed which wire format is allowed/expected?
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
static int
validate_and_hash_wireformat (const char *allowed)
{
  const char *allowed_arr[] = {
    allowed,
    NULL
  };

  if (GNUNET_YES !=
      TALER_json_validate_wireformat (allowed_arr,
                                      j_wire))
    return GNUNET_SYSERR;
  if (GNUNET_SYSERR ==
      TALER_hash_json (j_wire,
                       &h_wire))
    return MHD_NO;
  return GNUNET_OK;
}


/**
 * Custom cleanup routine for a `struct PayContext`.
 *
 * @param hc the `struct PayContext` to clean up.
 */
void
TMH_json_parse_cleanup (struct TM_HandlerContext *hc)
{
  struct TMH_JsonParseContext *jpc = (struct TMH_JsonParseContext *) hc;

  TMH_PARSE_post_cleanup_callback (jpc->json_parse_context);
}


/**
 * Function that queries MHD's select sets and
 * starts the task waiting for them.
 *
 * @param daemon_handle HTTP server to prepare to run
 */
static struct GNUNET_SCHEDULER_Task *
prepare_daemon ()
{
  struct GNUNET_SCHEDULER_Task * ret;
  fd_set rs;
  fd_set ws;
  fd_set es;
  struct GNUNET_NETWORK_FDSet *wrs;
  struct GNUNET_NETWORK_FDSet *wws;
  int max;
  MHD_UNSIGNED_LONG_LONG timeout;
  int haveto;
  struct GNUNET_TIME_Relative tv;

  FD_ZERO (&rs);
  FD_ZERO (&ws);
  FD_ZERO (&es);
  wrs = GNUNET_NETWORK_fdset_create ();
  wws = GNUNET_NETWORK_fdset_create ();
  max = -1;
  GNUNET_assert (MHD_YES ==
                 MHD_get_fdset (mhd,
                                &rs,
                                &ws,
                                &es,
                                &max));
  haveto = MHD_get_timeout (mhd, &timeout);
  if (haveto == MHD_YES)
    tv.rel_value_us = (uint64_t) timeout * 1000LL;
  else
    tv = GNUNET_TIME_UNIT_FOREVER_REL;
  GNUNET_NETWORK_fdset_copy_native (wrs, &rs, max + 1);
  GNUNET_NETWORK_fdset_copy_native (wws, &ws, max + 1);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Adding run_daemon select task\n");
  ret =
      GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_HIGH,
				   tv, wrs, wws,
                                   &run_daemon,
                                   NULL);
  GNUNET_NETWORK_fdset_destroy (wrs);
  GNUNET_NETWORK_fdset_destroy (wws);
  return ret;
}


/**
 * Main function that will be run by the scheduler.
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be
 *        NULL!)
 * @param config configuration
 */
void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *config)
{
  char *wireformat;

  result = GNUNET_SYSERR;
  shutdown_task =
    GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
                                  &do_shutdown,
                                  NULL);
  EXITIF (GNUNET_SYSERR ==
          TMH_EXCHANGES_init (config));
  EXITIF (GNUNET_SYSERR ==
          TMH_AUDITORS_init (config));
  /* FIXME: for now, we just support SEPA here: */
  EXITIF (GNUNET_OK !=
          GNUNET_CONFIGURATION_get_value_string (config,
                                                 "merchant",
                                                 "WIREFORMAT",
                                                 &wireformat));

  if (0 == strcmp("SEPA", wireformat))
  {
    EXITIF (GNUNET_OK !=
            parse_wireformat_sepa (config));
    EXITIF (GNUNET_OK !=
            validate_and_hash_wireformat ("SEPA"));
  }
  else if (0 == strcmp("TEST", wireformat))
  {
    EXITIF (GNUNET_OK !=
            parse_wireformat_test (config));
    EXITIF (GNUNET_OK !=
            validate_and_hash_wireformat ("TEST"));
  }
  GNUNET_free (wireformat);

  EXITIF (GNUNET_OK !=
          GNUNET_CONFIGURATION_get_value_filename (config,
                                                   "merchant",
                                                   "KEYFILE",
                                                   &keyfile));
  EXITIF (NULL ==
          (privkey =
          GNUNET_CRYPTO_eddsa_key_create_from_file (keyfile)));
  GNUNET_CRYPTO_eddsa_key_get_public (privkey,
                                      &pubkey.eddsa_pub);
  EXITIF (NULL ==
          (db = TALER_MERCHANTDB_plugin_load (config)));
  EXITIF (GNUNET_OK !=
          db->initialize (db->cls, dry));
  EXITIF (GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_number (config,
                                                 "merchant",
                                                 "PORT",
                                                 &port));
  EXITIF (GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_string (config,
                                                 "merchant",
                                                 "HOSTNAME",
                                                 &hostname));
  EXITIF (GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_string (config,
                                                 "merchant",
                                                 "CURRENCY",
                                                 &TMH_merchant_currency_string));

  EXITIF (GNUNET_SYSERR ==
          GNUNET_CONFIGURATION_get_value_time (config,
                                               "merchant",
                                               "EDATE",
                                               &edate_delay));

  mhd = MHD_start_daemon (MHD_USE_SUSPEND_RESUME,
                          port,
                          NULL, NULL,
                          &url_handler, NULL,
			  MHD_OPTION_NOTIFY_COMPLETED,
			  &handle_mhd_completion_callback, NULL,
                          MHD_OPTION_END);
  EXITIF (NULL == mhd);
  result = GNUNET_OK;
  mhd_task = prepare_daemon ();

 EXITIF_exit:
  if (GNUNET_OK != result)
    GNUNET_SCHEDULER_shutdown ();
  GNUNET_free_non_null (keyfile);
  if (GNUNET_OK != result)
    GNUNET_SCHEDULER_shutdown ();
}


/**
 * The main function of the serve tool
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main (int argc, char *const *argv)
{
  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
    {'t', "temp", NULL,
     gettext_noop ("Use temporary database tables"), GNUNET_NO,
     &GNUNET_GETOPT_set_one, &dry},
    GNUNET_GETOPT_OPTION_END
  };

  if (GNUNET_OK !=
      GNUNET_PROGRAM_run (argc, argv,
                          "taler-merchant-httpd",
                          "Taler merchant's HTTP backend interface",
                          options, &run, NULL))
    return 3;
  return (GNUNET_OK == result) ? 0 : 1;
}