/*
  This file is part of TALER
  Copyright (C) 2020 Taler Systems SA

  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, see <http://www.gnu.org/licenses/>
*/
/**
 * @file taler-exchange-offline.c
 * @brief Support for operations involving the exchange's offline master key.
 * @author Christian Grothoff
 */
#include <platform.h>
#include "taler_exchange_service.h"


/**
 * Our context for making HTTP requests.
 */
static struct GNUNET_CURL_Context *ctx;

/**
 * Reschedule context for #ctx.
 */
static struct GNUNET_CURL_RescheduleContext *rc;

/**
 * Handle to the exchange's configuration
 */
static const struct GNUNET_CONFIGURATION_Handle *kcfg;

/**
 * Return value from main().
 */
static int global_ret;


/**
 * A subcommand supported by this program.
 */
struct SubCommand
{
  /**
   * Name of the command.
   */
  const char *name;

  /**
   * Help text for the command.
   */
  const char *help;

  /**
   * Function implementing the command.
   *
   * @param args subsequent command line arguments (char **)
   */
  void (*cb)(char *const *args);
};


/**
 * Next work item to perform.
 */
static struct GNUNET_SCHEDULER_Task *nxt;

/**
 * Handle for #do_download.
 */
static struct TALER_EXCHANGE_ManagementGetKeysHandle *mgkh;


/**
 * Shutdown task. Invoked when the application is being terminated.
 *
 * @param cls NULL
 */
static void
do_shutdown (void *cls)
{
  (void) cls;
  if (NULL != nxt)
  {
    GNUNET_SCHEDULER_cancel (nxt);
    nxt = NULL;
  }
  if (NULL != mgkh)
  {
    TALER_EXCHANGE_get_management_keys_cancel (mgkh);
    mgkh = NULL;
  }
  if (NULL != ctx)
  {
    GNUNET_CURL_fini (ctx);
    ctx = NULL;
  }
  if (NULL != rc)
  {
    GNUNET_CURL_gnunet_rc_destroy (rc);
    rc = NULL;
  }
}


/**
 * Function to continue processing the next command.
 *
 * @param cls must be a `char *const*` with the array of
 *        command-line arguments to process next
 */
static void
work (void *cls);


/**
 * Function to schedule job to process the next command.
 *
 * @param args the array of command-line arguments to process next
 */
static void
next (char *const *args)
{
  GNUNET_assert (NULL == nxt);
  nxt = GNUNET_SCHEDULER_add_now (&work,
                                  (void *) args);
}


/**
 * Function called with information about future keys.  Dumps the JSON output
 * (on success), either into an internal buffer or to stdout (depending on
 * whether there are subsequent commands).
 *
 * @param cls closure with the `char **` remaining args
 * @param hr HTTP response data
 * @param keys information about the various keys used
 *        by the exchange, NULL if /management/keys failed
 */
static void
download_cb (void *cls,
             const struct TALER_EXCHANGE_HttpResponse *hr,
             const struct TALER_EXCHANGE_FutureKeys *keys)
{
  char *const *args = cls;

  mgkh = NULL;
  fprintf (stderr,
           "FIXME: dump!\n");
  next (args);
}


/**
 * Download future keys.
 *
 * @param args the array of command-line arguments to process next
 */
static void
do_download (char *const *args)
{
  char *exchange_url;

  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (kcfg,
                                             "exchange",
                                             "BASE_URL",
                                             &exchange_url))
  {
    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                               "exchange",
                               "BASE_URL");
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  mgkh = TALER_EXCHANGE_get_management_keys (ctx,
                                             exchange_url,
                                             &download_cb,
                                             (void *) args);
  GNUNET_free (exchange_url);
}


static void
work (void *cls)
{
  char *const *args = cls;
  struct SubCommand cmds[] = {
    {
      .name = "download",
      .help =
        "obtain future public keys from exchange (to be performed online!)",
      .cb = &do_download
    },
    /* list terminator */
    {
      .name = NULL,
    }
  };
  (void) cls;

  nxt = NULL;
  for (unsigned int i = 0; NULL != cmds[i].name; i++)
  {
    if (0 == strcasecmp (cmds[i].name,
                         args[0]))
    {
      cmds[i].cb (&args[1]);
      return;
    }
  }

  if (0 != strcasecmp ("help",
                       args[0]))
    fprintf (stderr,
             "Unexpected command `%s'\n",
             args[0]);
  fprintf (stderr,
           "Supported subcommands:");
  for (unsigned int i = 0; NULL != cmds[i].name; i++)
  {
    fprintf (stderr,
             "%s - %s\n",
             cmds[i].name,
             cmds[i].help);
  }
}


/**
 * Main function that will be run.
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg configuration
 */
static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  kcfg = cfg;
  ctx = GNUNET_CURL_init (&GNUNET_CURL_gnunet_scheduler_reschedule,
                          &rc);
  rc = GNUNET_CURL_gnunet_rc_create (ctx);
  GNUNET_SCHEDULER_add_shutdown (&do_shutdown,
                                 NULL);
  next (args);
}


/**
 * The main function of the taler-exchange-keyup tool.  This tool is used to
 * create the signing and denomination keys for the exchange.  It uses the
 * long-term offline private key and writes the (additional) key files to the
 * respective exchange directory (from where they can then be copied to the
 * online server).  Note that we need (at least) the most recent generated
 * previous keys to align the validity periods.
 *
 * @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)
{
  struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_OPTION_END
  };

  /* force linker to link against libtalerutil; if we do
     not do this, the linker may "optimize" libtalerutil
     away and skip #TALER_OS_init(), which we do need */
  (void) TALER_project_data_default ();
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_log_setup ("taler-exchange-offline",
                                   "WARNING",
                                   NULL));
  if (GNUNET_OK !=
      GNUNET_PROGRAM_run (argc, argv,
                          "taler-exchange-offline",
                          "Operations for offline signing for a Taler exchange",
                          options,
                          &run, NULL))
    return 1;
  return global_ret;
}


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