/*
     This file is part of GNUnet.
     Copyright (C) 2013-2019 GNUnet e.V.

     GNUnet 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 of the License,
     or (at your option) any later version.

     GNUnet 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 this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */
/**
 * @file util/gnunet-qr.c
 * @author Hartmut Goebel (original implementation)
 * @author Martin Schanzenbach (integrate gnunet-uri)
 * @author Christian Grothoff (error handling)
 */
#include <stdio.h>
#include <zbar.h>
#include <stdbool.h>
#include "platform.h"
#include "gnunet_util_lib.h"

#define LOG(fmt, ...)  \
  if (verbose) \
  printf (fmt, ## __VA_ARGS__)

/**
 * Video device to capture from. Sane default for GNU/Linux systems.
 */
static char *device = "/dev/video0";

/**
 * --verbose option
 */
static unsigned int verbose;

/**
 * --silent option
 */
static int silent = false;

/**
 * Handler exit code
 */
static long unsigned int exit_code = 1;

/**
 * Helper process we started.
 */
static struct GNUNET_OS_Process *p;

/**
 * Child signal handler.
 */
static struct GNUNET_SIGNAL_Context *shc_chld;

/**
 * Pipe used to communicate child death via signal.
 */
static struct GNUNET_DISK_PipeHandle *sigpipe;

/**
 * Process ID of this process at the time we installed the various
 * signal handlers.
 */
static pid_t my_pid;

/**
 * Task triggered whenever we receive a SIGCHLD (child
 * process died) or when user presses CTRL-C.
 *
 * @param cls closure, NULL
 */
static void
maint_child_death (void *cls)
{
  enum GNUNET_OS_ProcessStatusType type;

  if ((GNUNET_OK != GNUNET_OS_process_status (p, &type, &exit_code)) ||
      (type != GNUNET_OS_PROCESS_EXITED))
    GNUNET_break (0 == GNUNET_OS_process_kill (p, GNUNET_TERM_SIG));
  GNUNET_SIGNAL_handler_uninstall (shc_chld);
  shc_chld = NULL;
  if (NULL != sigpipe)
  {
    GNUNET_DISK_pipe_close (sigpipe);
    sigpipe = NULL;
  }
  GNUNET_OS_process_destroy (p);
}


/**
 * Signal handler called for signals that causes us to wait for the child process.
 */
static void
sighandler_chld ()
{
  static char c;
  int old_errno = errno;        /* backup errno */

  if (getpid () != my_pid)
    _exit (1);                   /* we have fork'ed since the signal handler was created,
                                  * ignore the signal, see https://gnunet.org/vfork discussion */
  GNUNET_DISK_file_write (GNUNET_DISK_pipe_handle
                            (sigpipe, GNUNET_DISK_PIPE_END_WRITE),
                          &c, sizeof(c));
  errno = old_errno;
}


/**
 * Dispatch URIs to the appropriate GNUnet helper process
 *
 * @param cls closure
 * @param uri uri to dispatch
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg configuration
 */
static void
gnunet_uri (void *cls,
            const char *uri,
            const char *cfgfile,
            const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  const char *orig_uri;
  const char *slash;
  char *subsystem;
  char *program;
  struct GNUNET_SCHEDULER_Task *rt;

  orig_uri = uri;
  if (0 != strncasecmp ("gnunet://", uri, strlen ("gnunet://")))
  {
    fprintf (stderr,
             _ ("Invalid URI: does not start with `%s'\n"),
             "gnunet://");
    return;
  }
  uri += strlen ("gnunet://");
  if (NULL == (slash = strchr (uri, '/')))
  {
    fprintf (stderr, _ ("Invalid URI: fails to specify subsystem\n"));
    return;
  }
  subsystem = GNUNET_strndup (uri, slash - uri);
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg, "uri", subsystem, &program))
  {
    fprintf (stderr, _ ("No handler known for subsystem `%s'\n"), subsystem);
    GNUNET_free (subsystem);
    return;
  }
  GNUNET_free (subsystem);
  sigpipe = GNUNET_DISK_pipe (GNUNET_DISK_PF_NONE);
  GNUNET_assert (NULL != sigpipe);
  rt = GNUNET_SCHEDULER_add_read_file (
    GNUNET_TIME_UNIT_FOREVER_REL,
    GNUNET_DISK_pipe_handle (sigpipe, GNUNET_DISK_PIPE_END_READ),
    &maint_child_death,
    NULL);
  my_pid = getpid ();
  shc_chld = GNUNET_SIGNAL_handler_install (SIGCHLD,
                                            &sighandler_chld);

  {
    char **argv = NULL;
    unsigned int argc = 0;
    char *u = GNUNET_strdup (program);

    for (const char *tok = strtok (u, " ");
         NULL != tok;
         tok = strtok (NULL, " "))
      GNUNET_array_append (argv,
                           argc,
                           GNUNET_strdup (tok));
    GNUNET_array_append (argv,
                         argc,
                         GNUNET_strdup (orig_uri));
    GNUNET_array_append (argv,
                         argc,
                         NULL);
    p = GNUNET_OS_start_process_vap (GNUNET_OS_INHERIT_STD_ALL,
                                     NULL,
                                     NULL,
                                     NULL,
                                     argv[0],
                                     argv);
    for (unsigned int i = 0; i<argc - 1; i++)
      GNUNET_free (argv[i]);
    GNUNET_array_grow (argv,
                       argc,
                       0);
    GNUNET_free (u);
  }
  if (NULL == p)
    GNUNET_SCHEDULER_cancel (rt);
  GNUNET_free (program);
}


/**
 * Obtain QR code 'symbol' from @a proc.
 *
 * @param proc zbar processor to use
 * @return NULL on error
 */
static const zbar_symbol_t *
get_symbol (zbar_processor_t *proc)
{
  const zbar_symbol_set_t *symbols;
  int rc;
  int n;

  if (0 != zbar_processor_parse_config (proc, "enable"))
  {
    GNUNET_break (0);
    return NULL;
  }

  /* initialize the Processor */
  if (0 != (rc = zbar_processor_init (proc, device, 1)))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to open device `%s': %d\n",
                device,
                rc);
    return NULL;
  }

  /* enable the preview window */
  if ((0 != (rc = zbar_processor_set_visible (proc, 1))) ||
      (0 != (rc = zbar_processor_set_active (proc, 1))))
  {
    GNUNET_break (0);
    return NULL;
  }

  /* read at least one barcode (or until window closed) */
  LOG ("Capturing\n");
  n = zbar_process_one (proc, -1);

  /* hide the preview window */
  (void) zbar_processor_set_active (proc, 0);
  (void) zbar_processor_set_visible (proc, 0);
  if (-1 == n)
    return NULL; /* likely user closed the window */
  LOG ("Got %i images\n", n);
  /* extract results */
  symbols = zbar_processor_get_results (proc);
  if (NULL == symbols)
  {
    GNUNET_break (0);
    return NULL;
  }
  return zbar_symbol_set_first_symbol (symbols);
}


/**
 * Run zbar QR code parser.
 *
 * @return NULL on error, otherwise the URI that we found
 */
static char *
run_zbar ()
{
  zbar_processor_t *proc;
  const char *data;
  char *ret;
  const zbar_symbol_t *symbol;

  /* configure the Processor */
  proc = zbar_processor_create (1);
  if (NULL == proc)
  {
    GNUNET_break (0);
    return NULL;
  }

  symbol = get_symbol (proc);
  if (NULL == symbol)
  {
    zbar_processor_destroy (proc);
    return NULL;
  }
  data = zbar_symbol_get_data (symbol);
  if (NULL == data)
  {
    GNUNET_break (0);
    zbar_processor_destroy (proc);
    return NULL;
  }
  LOG ("Found %s \"%s\"\n",
       zbar_get_symbol_name (zbar_symbol_get_type (symbol)),
       data);
  ret = GNUNET_strdup (data);
  /* clean up */
  zbar_processor_destroy (proc);
  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 cfg configuration
 */
static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  char *data;

  data = run_zbar ();
  if (NULL == data)
    return;
  gnunet_uri (cls, data, cfgfile, cfg);
  if (exit_code != 0)
  {
    printf ("Failed to add URI %s\n", data);
  }
  else
  {
    printf ("Added URI %s\n", data);
  }
  GNUNET_free (data);
};


int
main (int argc, char *const *argv)
{
  int ret;
  struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_option_string (
      'd',
      "device",
      "DEVICE",
      gettext_noop ("use video-device DEVICE (default: /dev/video0"),
      &device),
    GNUNET_GETOPT_option_verbose (&verbose),
    GNUNET_GETOPT_option_flag ('s',
                               "silent",
                               gettext_noop ("do not show preview windows"),
                               &silent),
    GNUNET_GETOPT_OPTION_END
  };

  ret = GNUNET_PROGRAM_run (
    argc,
    argv,
    "gnunet-qr",
    gettext_noop (
      "Scan a QR code using a video device and import the uri read"),
    options,
    &run,
    NULL);
  return ((GNUNET_OK == ret) && (0 == exit_code)) ? 0 : 1;
}