malcontent/libmalcontent/app-filter.c

/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
 *
 * Copyright © 2018 Endless Mobile, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Authors:
 *  - Philip Withnall <withnall@endlessm.com>
 */

#include "config.h"

#include <glib.h>
#include <glib-object.h>
#include <glib/gi18n-lib.h>
#include <gio/gdesktopappinfo.h>
#include <gio/gio.h>
#include <libmalcontent/app-filter.h>


G_DEFINE_QUARK (MctAppFilterError, mct_app_filter_error)

/**
 * MctAppFilterListType:
 * @MCT_APP_FILTER_LIST_BLACKLIST: Any program in the list is not allowed to
 *    be run.
 * @MCT_APP_FILTER_LIST_WHITELIST: Any program not in the list is not allowed
 *    to be run.
 *
 * Different semantics for interpreting an application list.
 *
 * Since: 0.2.0
 */
typedef enum
{
  MCT_APP_FILTER_LIST_BLACKLIST,
  MCT_APP_FILTER_LIST_WHITELIST,
} MctAppFilterListType;

struct _MctAppFilter
{
  gint ref_count;

  uid_t user_id;

  gchar **app_list;  /* (owned) (array zero-terminated=1) */
  MctAppFilterListType app_list_type;

  GVariant *oars_ratings;  /* (type a{ss}) (owned non-floating) */
  gboolean allow_user_installation;
  gboolean allow_system_installation;
};

G_DEFINE_BOXED_TYPE (MctAppFilter, mct_app_filter,
                     mct_app_filter_ref, mct_app_filter_unref)

/**
 * mct_app_filter_ref:
 * @filter: (transfer none): an #MctAppFilter
 *
 * Increment the reference count of @filter, and return the same pointer to it.
 *
 * Returns: (transfer full): the same pointer as @filter
 * Since: 0.2.0
 */
MctAppFilter *
mct_app_filter_ref (MctAppFilter *filter)
{
  g_return_val_if_fail (filter != NULL, NULL);
  g_return_val_if_fail (filter->ref_count >= 1, NULL);
  g_return_val_if_fail (filter->ref_count <= G_MAXINT - 1, NULL);

  filter->ref_count++;
  return filter;
}

/**
 * mct_app_filter_unref:
 * @filter: (transfer full): an #MctAppFilter
 *
 * Decrement the reference count of @filter. If the reference count reaches
 * zero, free the @filter and all its resources.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_unref (MctAppFilter *filter)
{
  g_return_if_fail (filter != NULL);
  g_return_if_fail (filter->ref_count >= 1);

  filter->ref_count--;

  if (filter->ref_count <= 0)
    {
      g_strfreev (filter->app_list);
      g_variant_unref (filter->oars_ratings);
      g_free (filter);
    }
}

/**
 * mct_app_filter_get_user_id:
 * @filter: an #MctAppFilter
 *
 * Get the user ID of the user this #MctAppFilter is for.
 *
 * Returns: user ID of the relevant user
 * Since: 0.2.0
 */
uid_t
mct_app_filter_get_user_id (MctAppFilter *filter)
{
  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);

  return filter->user_id;
}

/**
 * mct_app_filter_is_path_allowed:
 * @filter: an #MctAppFilter
 * @path: (type filename): absolute path of a program to check
 *
 * Check whether the program at @path is allowed to be run according to this
 * app filter. @path will be canonicalised without doing any I/O.
 *
 * Returns: %TRUE if the user this @filter corresponds to is allowed to run the
 *    program at @path according to the @filter policy; %FALSE otherwise
 * Since: 0.2.0
 */
gboolean
mct_app_filter_is_path_allowed (MctAppFilter *filter,
                                const gchar  *path)
{
  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);
  g_return_val_if_fail (path != NULL, FALSE);
  g_return_val_if_fail (g_path_is_absolute (path), FALSE);

  g_autofree gchar *canonical_path = g_canonicalize_filename (path, "/");
  gboolean path_in_list = g_strv_contains ((const gchar * const *) filter->app_list,
                                           canonical_path);

  switch (filter->app_list_type)
    {
    case MCT_APP_FILTER_LIST_BLACKLIST:
      return !path_in_list;
    case MCT_APP_FILTER_LIST_WHITELIST:
      return path_in_list;
    default:
      g_assert_not_reached ();
    }
}

/**
 * mct_app_filter_is_flatpak_ref_allowed:
 * @filter: an #MctAppFilter
 * @app_ref: flatpak ref for the app, for example `app/org.gnome.Builder/x86_64/master`
 *
 * Check whether the flatpak app with the given @app_ref is allowed to be run
 * according to this app filter.
 *
 * Returns: %TRUE if the user this @filter corresponds to is allowed to run the
 *    flatpak called @app_ref according to the @filter policy; %FALSE otherwise
 * Since: 0.2.0
 */
gboolean
mct_app_filter_is_flatpak_ref_allowed (MctAppFilter *filter,
                                       const gchar  *app_ref)
{
  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);
  g_return_val_if_fail (app_ref != NULL, FALSE);

  gboolean ref_in_list = g_strv_contains ((const gchar * const *) filter->app_list,
                                          app_ref);

  switch (filter->app_list_type)
    {
    case MCT_APP_FILTER_LIST_BLACKLIST:
      return !ref_in_list;
    case MCT_APP_FILTER_LIST_WHITELIST:
      return ref_in_list;
    default:
      g_assert_not_reached ();
    }
}

/**
 * mct_app_filter_is_flatpak_app_allowed:
 * @filter: an #MctAppFilter
 * @app_id: flatpak ID for the app, for example `org.gnome.Builder`
 *
 * Check whether the flatpak app with the given @app_id is allowed to be run
 * according to this app filter. This is a globbing match, matching @app_id
 * against potentially multiple entries in the blacklist, as the blacklist
 * contains flatpak refs (for example, `app/org.gnome.Builder/x86_64/master`)
 * which contain architecture and branch information. App IDs (for example,
 * `org.gnome.Builder`) do not contain architecture or branch information.
 *
 * Returns: %TRUE if the user this @filter corresponds to is allowed to run the
 *    flatpak called @app_id according to the @filter policy; %FALSE otherwise
 * Since: 0.2.0
 */
gboolean
mct_app_filter_is_flatpak_app_allowed (MctAppFilter *filter,
                                       const gchar  *app_id)
{
  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);
  g_return_val_if_fail (app_id != NULL, FALSE);

  gsize app_id_len = strlen (app_id);

  gboolean id_in_list = FALSE;
  for (gsize i = 0; filter->app_list[i] != NULL; i++)
    {
      /* Avoid using flatpak_ref_parse() to avoid a dependency on libflatpak
       * just for that one function. */
      if (g_str_has_prefix (filter->app_list[i], "app/") &&
          strncmp (filter->app_list[i] + strlen ("app/"), app_id, app_id_len) == 0 &&
          filter->app_list[i][strlen ("app/") + app_id_len] == '/')
        {
          id_in_list = TRUE;
          break;
        }
    }

  switch (filter->app_list_type)
    {
    case MCT_APP_FILTER_LIST_BLACKLIST:
      return !id_in_list;
    case MCT_APP_FILTER_LIST_WHITELIST:
      return id_in_list;
    default:
      g_assert_not_reached ();
    }
}

/**
 * mct_app_filter_is_appinfo_allowed:
 * @filter: an #MctAppFilter
 * @app_info: (transfer none): application information
 *
 * Check whether the app with the given @app_info is allowed to be run
 * according to this app filter. This matches on multiple keys potentially
 * present in the #GAppInfo, including the path of the executable.
 *
 * Returns: %TRUE if the user this @filter corresponds to is allowed to run the
 *    app represented by @app_info according to the @filter policy; %FALSE
 *    otherwise
 * Since: 0.2.0
 */
gboolean
mct_app_filter_is_appinfo_allowed (MctAppFilter *filter,
                                   GAppInfo     *app_info)
{
  g_autofree gchar *abs_path = NULL;

  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);
  g_return_val_if_fail (G_IS_APP_INFO (app_info), FALSE);

  abs_path = g_find_program_in_path (g_app_info_get_executable (app_info));

  if (abs_path != NULL &&
      !mct_app_filter_is_path_allowed (filter, abs_path))
    return FALSE;

  if (G_IS_DESKTOP_APP_INFO (app_info))
    {
      g_autofree gchar *flatpak_app = NULL;
      g_autofree gchar *old_flatpak_apps_str = NULL;

      /* This gives `org.gnome.Builder`. */
      flatpak_app = g_desktop_app_info_get_string (G_DESKTOP_APP_INFO (app_info), "X-Flatpak");
      if (flatpak_app != NULL)
        flatpak_app = g_strstrip (flatpak_app);

      if (flatpak_app != NULL &&
          !mct_app_filter_is_flatpak_app_allowed (filter, flatpak_app))
        return FALSE;

      /* FIXME: This could do with the g_desktop_app_info_get_string_list() API
       * from GLib 2.60. Gives `gimp.desktop;org.gimp.Gimp.desktop;`. */
      old_flatpak_apps_str = g_desktop_app_info_get_string (G_DESKTOP_APP_INFO (app_info), "X-Flatpak-RenamedFrom");
      if (old_flatpak_apps_str != NULL)
        {
          g_auto(GStrv) old_flatpak_apps = g_strsplit (old_flatpak_apps_str, ";", -1);

          for (gsize i = 0; old_flatpak_apps[i] != NULL; i++)
            {
              gchar *old_flatpak_app = g_strstrip (old_flatpak_apps[i]);

              if (g_str_has_suffix (old_flatpak_app, ".desktop"))
                old_flatpak_app[strlen (old_flatpak_app) - strlen (".desktop")] = '\0';
              old_flatpak_app = g_strstrip (old_flatpak_app);

              if (*old_flatpak_app != '\0' &&
                  !mct_app_filter_is_flatpak_app_allowed (filter, old_flatpak_app))
                return FALSE;
            }
        }
    }

  return TRUE;
}

static gint
strcmp_cb (gconstpointer a,
           gconstpointer b)
{
  const gchar *str_a = *((const gchar * const *) a);
  const gchar *str_b = *((const gchar * const *) b);

  return g_strcmp0 (str_a, str_b);
}

/**
 * mct_app_filter_get_oars_sections:
 * @filter: an #MctAppFilter
 *
 * List the OARS sections present in this app filter. The sections are returned
 * in lexicographic order. A section will be listed even if its stored value is
 * %MCT_APP_FILTER_OARS_VALUE_UNKNOWN. The returned list may be empty.
 *
 * Returns: (transfer container) (array zero-terminated=1): %NULL-terminated
 *    array of OARS sections
 * Since: 0.2.0
 */
const gchar **
mct_app_filter_get_oars_sections (MctAppFilter *filter)
{
  g_autoptr(GPtrArray) sections = g_ptr_array_new_with_free_func (NULL);
  GVariantIter iter;
  const gchar *oars_section;

  g_return_val_if_fail (filter != NULL, NULL);
  g_return_val_if_fail (filter->ref_count >= 1, NULL);

  g_variant_iter_init (&iter, filter->oars_ratings);

  while (g_variant_iter_loop (&iter, "{&s&s}", &oars_section, NULL))
    g_ptr_array_add (sections, (gpointer) oars_section);

  /* Sort alphabetically for easier comparisons later. */
  g_ptr_array_sort (sections, strcmp_cb);

  g_ptr_array_add (sections, NULL);  /* NULL terminator */

  return (const gchar **) g_ptr_array_free (g_steal_pointer (&sections), FALSE);
}

/**
 * mct_app_filter_get_oars_value:
 * @filter: an #MctAppFilter
 * @oars_section: name of the OARS section to get the value from
 *
 * Get the value assigned to the given @oars_section in the OARS filter stored
 * within @filter. If that section has no value explicitly defined,
 * %MCT_APP_FILTER_OARS_VALUE_UNKNOWN is returned.
 *
 * This value is the most intense value allowed for apps to have in this
 * section, inclusive. Any app with a more intense value for this section must
 * be hidden from the user whose @filter this is.
 *
 * This does not factor in mct_app_filter_is_system_installation_allowed().
 *
 * Returns: an #MctAppFilterOarsValue
 * Since: 0.2.0
 */
MctAppFilterOarsValue
mct_app_filter_get_oars_value (MctAppFilter *filter,
                               const gchar  *oars_section)
{
  const gchar *value_str;

  g_return_val_if_fail (filter != NULL, MCT_APP_FILTER_OARS_VALUE_UNKNOWN);
  g_return_val_if_fail (filter->ref_count >= 1,
                        MCT_APP_FILTER_OARS_VALUE_UNKNOWN);
  g_return_val_if_fail (oars_section != NULL && *oars_section != '\0',
                        MCT_APP_FILTER_OARS_VALUE_UNKNOWN);

  if (!g_variant_lookup (filter->oars_ratings, oars_section, "&s", &value_str))
    return MCT_APP_FILTER_OARS_VALUE_UNKNOWN;

  if (g_str_equal (value_str, "none"))
    return MCT_APP_FILTER_OARS_VALUE_NONE;
  else if (g_str_equal (value_str, "mild"))
    return MCT_APP_FILTER_OARS_VALUE_MILD;
  else if (g_str_equal (value_str, "moderate"))
    return MCT_APP_FILTER_OARS_VALUE_MODERATE;
  else if (g_str_equal (value_str, "intense"))
    return MCT_APP_FILTER_OARS_VALUE_INTENSE;
  else
    return MCT_APP_FILTER_OARS_VALUE_UNKNOWN;
}

/**
 * mct_app_filter_is_user_installation_allowed:
 * @filter: an #MctAppFilter
 *
 * Get whether the user is allowed to install to their flatpak user repository.
 * This should be queried in addition to the OARS values
 * (mct_app_filter_get_oars_value()) — if it returns %FALSE, the OARS values
 * should be ignored and app installation should be unconditionally disallowed.
 *
 * Returns: %TRUE if app installation is allowed to the user repository for
 *    this user; %FALSE if it is unconditionally disallowed for this user
 * Since: 0.2.0
 */
gboolean
mct_app_filter_is_user_installation_allowed (MctAppFilter *filter)
{
  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);

  return filter->allow_user_installation;
}

/**
 * mct_app_filter_is_system_installation_allowed:
 * @filter: an #MctAppFilter
 *
 * Get whether the user is allowed to install to the flatpak system repository.
 * This should be queried in addition to the OARS values
 * (mct_app_filter_get_oars_value()) — if it returns %FALSE, the OARS values
 * should be ignored and app installation should be unconditionally disallowed.
 *
 * Returns: %TRUE if app installation is allowed to the system repository for
 *    this user; %FALSE if it is unconditionally disallowed for this user
 * Since: 0.2.0
 */
gboolean
mct_app_filter_is_system_installation_allowed (MctAppFilter *filter)
{
  g_return_val_if_fail (filter != NULL, FALSE);
  g_return_val_if_fail (filter->ref_count >= 1, FALSE);

  return filter->allow_system_installation;
}

/**
 * _mct_app_filter_build_app_filter_variant:
 * @filter: an #MctAppFilter
 *
 * Build a #GVariant which contains the app filter from @filter, in the format
 * used for storing it in AccountsService.
 *
 * Returns: (transfer floating): a new, floating #GVariant containing the app
 *    filter
 * Since: 0.2.0
 */
static GVariant *
_mct_app_filter_build_app_filter_variant (MctAppFilter *filter)
{
  g_auto(GVariantBuilder) builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("(bas)"));

  g_return_val_if_fail (filter != NULL, NULL);
  g_return_val_if_fail (filter->ref_count >= 1, NULL);

  g_variant_builder_add (&builder, "b",
                         (filter->app_list_type == MCT_APP_FILTER_LIST_WHITELIST));
  g_variant_builder_open (&builder, G_VARIANT_TYPE ("as"));

  for (gsize i = 0; filter->app_list[i] != NULL; i++)
    g_variant_builder_add (&builder, "s", filter->app_list[i]);

  g_variant_builder_close (&builder);

  return g_variant_builder_end (&builder);
}

/* Check if @error is a D-Bus remote error matching @expected_error_name. */
static gboolean
bus_remote_error_matches (const GError *error,
                          const gchar  *expected_error_name)
{
  g_autofree gchar *error_name = NULL;

  if (!g_dbus_error_is_remote_error (error))
    return FALSE;

  error_name = g_dbus_error_get_remote_error (error);

  return g_str_equal (error_name, expected_error_name);
}

/* Convert a #GDBusError into a #MctAppFilter error. */
static GError *
bus_error_to_app_filter_error (const GError *bus_error,
                               uid_t         user_id)
{
  if (g_error_matches (bus_error, G_DBUS_ERROR, G_DBUS_ERROR_ACCESS_DENIED) ||
      bus_remote_error_matches (bus_error, "org.freedesktop.Accounts.Error.PermissionDenied"))
    return g_error_new (MCT_APP_FILTER_ERROR, MCT_APP_FILTER_ERROR_PERMISSION_DENIED,
                        _("Not allowed to query app filter data for user %u"),
                        (guint) user_id);
  else if (g_error_matches (bus_error, G_DBUS_ERROR, G_DBUS_ERROR_UNKNOWN_METHOD) ||
           bus_remote_error_matches (bus_error, "org.freedesktop.Accounts.Error.Failed"))
    return g_error_new (MCT_APP_FILTER_ERROR, MCT_APP_FILTER_ERROR_INVALID_USER,
                        _("User %u does not exist"), (guint) user_id);
  else
    return g_error_copy (bus_error);
}

/* Find the object path for the given @user_id on the accountsservice D-Bus
 * interface, by calling its FindUserById() method. This is a synchronous,
 * blocking function. */
static gchar *
accounts_find_user_by_id (GDBusConnection  *connection,
                          uid_t             user_id,
                          gboolean          allow_interactive_authorization,
                          GCancellable     *cancellable,
                          GError          **error)
{
  g_autofree gchar *object_path = NULL;
  g_autoptr(GVariant) result_variant = NULL;
  g_autoptr(GError) local_error = NULL;

  result_variant =
      g_dbus_connection_call_sync (connection,
                                   "org.freedesktop.Accounts",
                                   "/org/freedesktop/Accounts",
                                   "org.freedesktop.Accounts",
                                   "FindUserById",
                                   g_variant_new ("(x)", (gint64) user_id),
                                   G_VARIANT_TYPE ("(o)"),
                                   allow_interactive_authorization
                                     ? G_DBUS_CALL_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION
                                     : G_DBUS_CALL_FLAGS_NONE,
                                   -1,  /* timeout, ms */
                                   cancellable,
                                   &local_error);
  if (local_error != NULL)
    {
      g_autoptr(GError) app_filter_error = bus_error_to_app_filter_error (local_error,
                                                                          user_id);
      g_propagate_error (error, g_steal_pointer (&app_filter_error));
      return NULL;
    }

  g_variant_get (result_variant, "(o)", &object_path);

  return g_steal_pointer (&object_path);
}

/**
 * mct_get_app_filter:
 * @connection: (nullable): a #GDBusConnection to the system bus, or %NULL to
 *    use the default
 * @user_id: ID of the user to query, typically coming from getuid()
 * @flags: flags to affect the behaviour of the call
 * @cancellable: (nullable): a #GCancellable, or %NULL
 * @error: return location for a #GError, or %NULL
 *
 * Synchronous version of mct_get_app_filter_async().
 *
 * Returns: (transfer full): app filter for the queried user
 * Since: 0.3.0
 */
MctAppFilter *
mct_get_app_filter (GDBusConnection       *connection,
                    uid_t                  user_id,
                    MctGetAppFilterFlags   flags,
                    GCancellable          *cancellable,
                    GError               **error)
{
  g_autofree gchar *object_path = NULL;
  g_autoptr(GVariant) result_variant = NULL;
  g_autoptr(GVariant) properties = NULL;
  g_autoptr(GError) local_error = NULL;
  g_autoptr(MctAppFilter) app_filter = NULL;
  gboolean is_whitelist;
  g_auto(GStrv) app_list = NULL;
  const gchar *content_rating_kind;
  g_autoptr(GVariant) oars_variant = NULL;
  g_autoptr(GHashTable) oars_map = NULL;
  gboolean allow_user_installation;
  gboolean allow_system_installation;

  g_return_val_if_fail (connection == NULL || G_IS_DBUS_CONNECTION (connection), NULL);
  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), NULL);
  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

  if (connection == NULL)
    connection = g_bus_get_sync (G_BUS_TYPE_SYSTEM, cancellable, error);
  if (connection == NULL)
    return NULL;

  object_path = accounts_find_user_by_id (connection, user_id,
                                          (flags & MCT_GET_APP_FILTER_FLAGS_INTERACTIVE),
                                          cancellable, error);
  if (object_path == NULL)
    return NULL;

  result_variant =
      g_dbus_connection_call_sync (connection,
                                   "org.freedesktop.Accounts",
                                   object_path,
                                   "org.freedesktop.DBus.Properties",
                                   "GetAll",
                                   g_variant_new ("(s)", "com.endlessm.ParentalControls.AppFilter"),
                                   G_VARIANT_TYPE ("(a{sv})"),
                                   (flags & MCT_GET_APP_FILTER_FLAGS_INTERACTIVE)
                                     ? G_DBUS_CALL_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION
                                     : G_DBUS_CALL_FLAGS_NONE,
                                   -1,  /* timeout, ms */
                                   cancellable,
                                   &local_error);
  if (local_error != NULL)
    {
      g_autoptr(GError) app_filter_error = NULL;

      if (g_error_matches (local_error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS))
        {
          /* o.fd.D.GetAll() will return InvalidArgs errors if
           * accountsservice doesn’t have the com.endlessm.ParentalControls.AppFilter
           * extension interface installed. */
          app_filter_error = g_error_new_literal (MCT_APP_FILTER_ERROR,
                                                  MCT_APP_FILTER_ERROR_DISABLED,
                                                  _("App filtering is globally disabled"));
        }
      else
        {
          app_filter_error = bus_error_to_app_filter_error (local_error,
                                                            user_id);
        }

      g_propagate_error (error, g_steal_pointer (&app_filter_error));
      return NULL;
    }

  /* Extract the properties we care about. They may be silently omitted from the
   * results if we don’t have permission to access them. */
  properties = g_variant_get_child_value (result_variant, 0);
  if (!g_variant_lookup (properties, "AppFilter", "(b^as)",
                         &is_whitelist, &app_list))
    {
      g_set_error (error, MCT_APP_FILTER_ERROR,
                   MCT_APP_FILTER_ERROR_PERMISSION_DENIED,
                   _("Not allowed to query app filter data for user %u"),
                   (guint) user_id);
      return NULL;
    }

  if (!g_variant_lookup (properties, "OarsFilter", "(&s@a{ss})",
                         &content_rating_kind, &oars_variant))
    {
      /* Default value. */
      content_rating_kind = "oars-1.1";
      oars_variant = g_variant_new ("a{ss}", NULL);
    }

  /* Check that the OARS filter is in a format we support. Currently, that’s
   * only oars-1.0 and oars-1.1. */
  if (!g_str_equal (content_rating_kind, "oars-1.0") &&
      !g_str_equal (content_rating_kind, "oars-1.1"))
    {
      g_set_error (error, MCT_APP_FILTER_ERROR,
                   MCT_APP_FILTER_ERROR_INVALID_DATA,
                   _("OARS filter for user %u has an unrecognized kind ‘%s’"),
                   (guint) user_id, content_rating_kind);
      return NULL;
    }

  if (!g_variant_lookup (properties, "AllowUserInstallation", "b",
                         &allow_user_installation))
    {
      /* Default value. */
      allow_user_installation = TRUE;
    }

  if (!g_variant_lookup (properties, "AllowSystemInstallation", "b",
                         &allow_system_installation))
    {
      /* Default value. */
      allow_system_installation = FALSE;
    }

  /* Success. Create an #MctAppFilter object to contain the results. */
  app_filter = g_new0 (MctAppFilter, 1);
  app_filter->ref_count = 1;
  app_filter->user_id = user_id;
  app_filter->app_list = g_steal_pointer (&app_list);
  app_filter->app_list_type =
    is_whitelist ? MCT_APP_FILTER_LIST_WHITELIST : MCT_APP_FILTER_LIST_BLACKLIST;
  app_filter->oars_ratings = g_steal_pointer (&oars_variant);
  app_filter->allow_user_installation = allow_user_installation;
  app_filter->allow_system_installation = allow_system_installation;

  return g_steal_pointer (&app_filter);
}

static void get_app_filter_thread_cb (GTask        *task,
                                      gpointer      source_object,
                                      gpointer      task_data,
                                      GCancellable *cancellable);

typedef struct
{
  GDBusConnection *connection;  /* (nullable) (owned) */
  uid_t user_id;
  MctGetAppFilterFlags flags;
} GetAppFilterData;

static void
get_app_filter_data_free (GetAppFilterData *data)
{
  g_clear_object (&data->connection);
  g_free (data);
}

G_DEFINE_AUTOPTR_CLEANUP_FUNC (GetAppFilterData, get_app_filter_data_free)

/**
 * mct_get_app_filter_async:
 * @connection: (nullable): a #GDBusConnection to the system bus, or %NULL to
 *    use the default
 * @user_id: ID of the user to query, typically coming from getuid()
 * @flags: flags to affect the behaviour of the call
 * @cancellable: (nullable): a #GCancellable, or %NULL
 * @callback: a #GAsyncReadyCallback
 * @user_data: user data to pass to @callback
 *
 * Asynchronously get a snapshot of the app filter settings for the given
 * @user_id.
 *
 * @connection should be a connection to the system bus, where accounts-service
 * runs. It’s provided mostly for testing purposes, or to allow an existing
 * connection to be re-used. Pass %NULL to use the default connection.
 *
 * On failure, an #MctAppFilterError, a #GDBusError or a #GIOError will be
 * returned.
 *
 * Since: 0.3.0
 */
void
mct_get_app_filter_async  (GDBusConnection     *connection,
                           uid_t                user_id,
                           MctGetAppFilterFlags flags,
                           GCancellable        *cancellable,
                           GAsyncReadyCallback  callback,
                           gpointer             user_data)
{
  g_autoptr(GTask) task = NULL;
  g_autoptr(GetAppFilterData) data = NULL;

  g_return_if_fail (connection == NULL || G_IS_DBUS_CONNECTION (connection));
  g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));

  task = g_task_new (NULL, cancellable, callback, user_data);
  g_task_set_source_tag (task, mct_get_app_filter_async);

  data = g_new0 (GetAppFilterData, 1);
  data->connection = (connection != NULL) ? g_object_ref (connection) : NULL;
  data->user_id = user_id;
  data->flags = flags;
  g_task_set_task_data (task, g_steal_pointer (&data),
                        (GDestroyNotify) get_app_filter_data_free);

  g_task_run_in_thread (task, get_app_filter_thread_cb);
}

static void
get_app_filter_thread_cb (GTask        *task,
                          gpointer      source_object,
                          gpointer      task_data,
                          GCancellable *cancellable)
{
  g_autoptr(MctAppFilter) filter = NULL;
  GetAppFilterData *data = task_data;
  g_autoptr(GError) local_error = NULL;

  filter = mct_get_app_filter (data->connection, data->user_id,
                               data->flags,
                               cancellable, &local_error);

  if (local_error != NULL)
    g_task_return_error (task, g_steal_pointer (&local_error));
  else
    g_task_return_pointer (task, g_steal_pointer (&filter),
                           (GDestroyNotify) mct_app_filter_unref);
}

/**
 * mct_get_app_filter_finish:
 * @result: a #GAsyncResult
 * @error: return location for a #GError, or %NULL
 *
 * Finish an asynchronous operation to get the app filter for a user, started
 * with mct_get_app_filter_async().
 *
 * Returns: (transfer full): app filter for the queried user
 * Since: 0.2.0
 */
MctAppFilter *
mct_get_app_filter_finish (GAsyncResult  *result,
                           GError       **error)
{
  g_return_val_if_fail (g_task_is_valid (result, NULL), NULL);
  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

  return g_task_propagate_pointer (G_TASK (result), error);
}

/**
 * mct_set_app_filter:
 * @connection: (nullable): a #GDBusConnection to the system bus, or %NULL to
 *    use the default
 * @user_id: ID of the user to set the filter for, typically coming from getuid()
 * @app_filter: (transfer none): the app filter to set for the user
 * @flags: flags to affect the behaviour of the call
 * @cancellable: (nullable): a #GCancellable, or %NULL
 * @error: return location for a #GError, or %NULL
 *
 * Synchronous version of mct_set_app_filter_async().
 *
 * Returns: %TRUE on success, %FALSE otherwise
 * Since: 0.3.0
 */
gboolean
mct_set_app_filter (GDBusConnection       *connection,
                    uid_t                  user_id,
                    MctAppFilter          *app_filter,
                    MctSetAppFilterFlags   flags,
                    GCancellable          *cancellable,
                    GError               **error)
{
  g_autofree gchar *object_path = NULL;
  g_autoptr(GVariant) app_filter_variant = NULL;
  g_autoptr(GVariant) oars_filter_variant = NULL;
  g_autoptr(GVariant) allow_user_installation_variant = NULL;
  g_autoptr(GVariant) allow_system_installation_variant = NULL;
  g_autoptr(GVariant) app_filter_result_variant = NULL;
  g_autoptr(GVariant) oars_filter_result_variant = NULL;
  g_autoptr(GVariant) allow_user_installation_result_variant = NULL;
  g_autoptr(GVariant) allow_system_installation_result_variant = NULL;
  g_autoptr(GError) local_error = NULL;

  g_return_val_if_fail (connection == NULL || G_IS_DBUS_CONNECTION (connection), FALSE);
  g_return_val_if_fail (app_filter != NULL, FALSE);
  g_return_val_if_fail (app_filter->ref_count >= 1, FALSE);
  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);

  if (connection == NULL)
    connection = g_bus_get_sync (G_BUS_TYPE_SYSTEM, cancellable, error);
  if (connection == NULL)
    return FALSE;

  object_path = accounts_find_user_by_id (connection, user_id,
                                          (flags & MCT_SET_APP_FILTER_FLAGS_INTERACTIVE),
                                          cancellable, error);
  if (object_path == NULL)
    return FALSE;

  app_filter_variant = _mct_app_filter_build_app_filter_variant (app_filter);
  oars_filter_variant = g_variant_new ("(s@a{ss})", "oars-1.1",
                                       app_filter->oars_ratings);
  allow_user_installation_variant = g_variant_new_boolean (app_filter->allow_user_installation);
  allow_system_installation_variant = g_variant_new_boolean (app_filter->allow_system_installation);

  app_filter_result_variant =
      g_dbus_connection_call_sync (connection,
                                   "org.freedesktop.Accounts",
                                   object_path,
                                   "org.freedesktop.DBus.Properties",
                                   "Set",
                                   g_variant_new ("(ssv)",
                                                  "com.endlessm.ParentalControls.AppFilter",
                                                  "AppFilter",
                                                  g_steal_pointer (&app_filter_variant)),
                                   G_VARIANT_TYPE ("()"),
                                   (flags & MCT_SET_APP_FILTER_FLAGS_INTERACTIVE)
                                     ? G_DBUS_CALL_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION
                                     : G_DBUS_CALL_FLAGS_NONE,
                                   -1,  /* timeout, ms */
                                   cancellable,
                                   &local_error);
  if (local_error != NULL)
    {
      g_propagate_error (error, bus_error_to_app_filter_error (local_error, user_id));
      return FALSE;
    }

  oars_filter_result_variant =
      g_dbus_connection_call_sync (connection,
                                   "org.freedesktop.Accounts",
                                   object_path,
                                   "org.freedesktop.DBus.Properties",
                                   "Set",
                                   g_variant_new ("(ssv)",
                                                  "com.endlessm.ParentalControls.AppFilter",
                                                  "OarsFilter",
                                                  g_steal_pointer (&oars_filter_variant)),
                                   G_VARIANT_TYPE ("()"),
                                   (flags & MCT_SET_APP_FILTER_FLAGS_INTERACTIVE)
                                     ? G_DBUS_CALL_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION
                                     : G_DBUS_CALL_FLAGS_NONE,
                                   -1,  /* timeout, ms */
                                   cancellable,
                                   &local_error);
  if (local_error != NULL)
    {
      g_propagate_error (error, bus_error_to_app_filter_error (local_error, user_id));
      return FALSE;
    }

  allow_user_installation_result_variant =
      g_dbus_connection_call_sync (connection,
                                   "org.freedesktop.Accounts",
                                   object_path,
                                   "org.freedesktop.DBus.Properties",
                                   "Set",
                                   g_variant_new ("(ssv)",
                                                  "com.endlessm.ParentalControls.AppFilter",
                                                  "AllowUserInstallation",
                                                  g_steal_pointer (&allow_user_installation_variant)),
                                   G_VARIANT_TYPE ("()"),
                                   (flags & MCT_SET_APP_FILTER_FLAGS_INTERACTIVE)
                                     ? G_DBUS_CALL_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION
                                     : G_DBUS_CALL_FLAGS_NONE,
                                   -1,  /* timeout, ms */
                                   cancellable,
                                   &local_error);
  if (local_error != NULL)
    {
      g_propagate_error (error, bus_error_to_app_filter_error (local_error, user_id));
      return FALSE;
    }

  allow_system_installation_result_variant =
      g_dbus_connection_call_sync (connection,
                                   "org.freedesktop.Accounts",
                                   object_path,
                                   "org.freedesktop.DBus.Properties",
                                   "Set",
                                   g_variant_new ("(ssv)",
                                                  "com.endlessm.ParentalControls.AppFilter",
                                                  "AllowSystemInstallation",
                                                  g_steal_pointer (&allow_system_installation_variant)),
                                   G_VARIANT_TYPE ("()"),
                                   (flags & MCT_SET_APP_FILTER_FLAGS_INTERACTIVE)
                                     ? G_DBUS_CALL_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION
                                     : G_DBUS_CALL_FLAGS_NONE,
                                   -1,  /* timeout, ms */
                                   cancellable,
                                   &local_error);
  if (local_error != NULL)
    {
      g_propagate_error (error, bus_error_to_app_filter_error (local_error, user_id));
      return FALSE;
    }

  return TRUE;
}

static void set_app_filter_thread_cb (GTask        *task,
                                      gpointer      source_object,
                                      gpointer      task_data,
                                      GCancellable *cancellable);

typedef struct
{
  GDBusConnection *connection;  /* (nullable) (owned) */
  uid_t user_id;
  MctAppFilter *app_filter;  /* (owned) */
  MctSetAppFilterFlags flags;
} SetAppFilterData;

static void
set_app_filter_data_free (SetAppFilterData *data)
{
  g_clear_object (&data->connection);
  mct_app_filter_unref (data->app_filter);
  g_free (data);
}

G_DEFINE_AUTOPTR_CLEANUP_FUNC (SetAppFilterData, set_app_filter_data_free)

/**
 * mct_set_app_filter_async:
 * @connection: (nullable): a #GDBusConnection to the system bus, or %NULL to
 *    use the default
 * @user_id: ID of the user to set the filter for, typically coming from getuid()
 * @app_filter: (transfer none): the app filter to set for the user
 * @flags: flags to affect the behaviour of the call
 * @cancellable: (nullable): a #GCancellable, or %NULL
 * @callback: a #GAsyncReadyCallback
 * @user_data: user data to pass to @callback
 *
 * Asynchronously set the app filter settings for the given @user_id to the
 * given @app_filter instance. This will set all fields of the app filter.
 *
 * @connection should be a connection to the system bus, where accounts-service
 * runs. It’s provided mostly for testing purposes, or to allow an existing
 * connection to be re-used. Pass %NULL to use the default connection.
 *
 * On failure, an #MctAppFilterError, a #GDBusError or a #GIOError will be
 * returned. The user’s app filter settings will be left in an undefined state.
 *
 * Since: 0.3.0
 */
void
mct_set_app_filter_async (GDBusConnection      *connection,
                          uid_t                 user_id,
                          MctAppFilter         *app_filter,
                          MctSetAppFilterFlags  flags,
                          GCancellable         *cancellable,
                          GAsyncReadyCallback   callback,
                          gpointer              user_data)
{
  g_autoptr(GTask) task = NULL;
  g_autoptr(SetAppFilterData) data = NULL;

  g_return_if_fail (connection == NULL || G_IS_DBUS_CONNECTION (connection));
  g_return_if_fail (app_filter != NULL);
  g_return_if_fail (app_filter->ref_count >= 1);
  g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));

  task = g_task_new (NULL, cancellable, callback, user_data);
  g_task_set_source_tag (task, mct_set_app_filter_async);

  data = g_new0 (SetAppFilterData, 1);
  data->connection = (connection != NULL) ? g_object_ref (connection) : NULL;
  data->user_id = user_id;
  data->app_filter = mct_app_filter_ref (app_filter);
  data->flags = flags;
  g_task_set_task_data (task, g_steal_pointer (&data),
                        (GDestroyNotify) set_app_filter_data_free);

  g_task_run_in_thread (task, set_app_filter_thread_cb);
}

static void
set_app_filter_thread_cb (GTask        *task,
                          gpointer      source_object,
                          gpointer      task_data,
                          GCancellable *cancellable)
{
  gboolean success;
  SetAppFilterData *data = task_data;
  g_autoptr(GError) local_error = NULL;

  success = mct_set_app_filter (data->connection, data->user_id,
                                data->app_filter, data->flags,
                                cancellable, &local_error);

  if (local_error != NULL)
    g_task_return_error (task, g_steal_pointer (&local_error));
  else
    g_task_return_boolean (task, success);
}

/**
 * mct_set_app_filter_finish:
 * @result: a #GAsyncResult
 * @error: return location for a #GError, or %NULL
 *
 * Finish an asynchronous operation to set the app filter for a user, started
 * with mct_set_app_filter_async().
 *
 * Returns: %TRUE on success, %FALSE otherwise
 * Since: 0.2.0
 */
gboolean
mct_set_app_filter_finish (GAsyncResult  *result,
                           GError       **error)
{
  g_return_val_if_fail (g_task_is_valid (result, NULL), FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);

  return g_task_propagate_boolean (G_TASK (result), error);
}

/*
 * Actual implementation of #MctAppFilterBuilder.
 *
 * All members are %NULL if un-initialised, cleared, or ended.
 */
typedef struct
{
  GPtrArray *paths_blacklist;  /* (nullable) (owned) (element-type filename) */
  GHashTable *oars;  /* (nullable) (owned) (element-type utf8 MctAppFilterOarsValue) */
  gboolean allow_user_installation;
  gboolean allow_system_installation;

  /*< private >*/
  gpointer padding[2];
} MctAppFilterBuilderReal;

G_STATIC_ASSERT (sizeof (MctAppFilterBuilderReal) ==
                 sizeof (MctAppFilterBuilder));
G_STATIC_ASSERT (__alignof__ (MctAppFilterBuilderReal) ==
                 __alignof__ (MctAppFilterBuilder));

G_DEFINE_BOXED_TYPE (MctAppFilterBuilder, mct_app_filter_builder,
                     mct_app_filter_builder_copy, mct_app_filter_builder_free)

/**
 * mct_app_filter_builder_init:
 * @builder: an uninitialised #MctAppFilterBuilder
 *
 * Initialise the given @builder so it can be used to construct a new
 * #MctAppFilter. @builder must have been allocated on the stack, and must not
 * already be initialised.
 *
 * Construct the #MctAppFilter by calling methods on @builder, followed by
 * mct_app_filter_builder_end(). To abort construction, use
 * mct_app_filter_builder_clear().
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_init (MctAppFilterBuilder *builder)
{
  MctAppFilterBuilder local_builder = MCT_APP_FILTER_BUILDER_INIT ();
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);
  g_return_if_fail (_builder->paths_blacklist == NULL);
  g_return_if_fail (_builder->oars == NULL);

  memcpy (builder, &local_builder, sizeof (local_builder));
}

/**
 * mct_app_filter_builder_clear:
 * @builder: an #MctAppFilterBuilder
 *
 * Clear @builder, freeing any internal state in it. This will not free the
 * top-level storage for @builder itself, which is assumed to be allocated on
 * the stack.
 *
 * If called on an already-cleared #MctAppFilterBuilder, this function is
 * idempotent.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_clear (MctAppFilterBuilder *builder)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);

  g_clear_pointer (&_builder->paths_blacklist, g_ptr_array_unref);
  g_clear_pointer (&_builder->oars, g_hash_table_unref);
}

/**
 * mct_app_filter_builder_new:
 *
 * Construct a new #MctAppFilterBuilder on the heap. This is intended for
 * language bindings. The returned builder must eventually be freed with
 * mct_app_filter_builder_free(), but can be cleared zero or more times with
 * mct_app_filter_builder_clear() first.
 *
 * Returns: (transfer full): a new heap-allocated #MctAppFilterBuilder
 * Since: 0.2.0
 */
MctAppFilterBuilder *
mct_app_filter_builder_new (void)
{
  g_autoptr(MctAppFilterBuilder) builder = NULL;

  builder = g_new0 (MctAppFilterBuilder, 1);
  mct_app_filter_builder_init (builder);

  return g_steal_pointer (&builder);
}

/**
 * mct_app_filter_builder_copy:
 * @builder: an #MctAppFilterBuilder
 *
 * Copy the given @builder to a newly-allocated #MctAppFilterBuilder on the
 * heap. This is safe to use with cleared, stack-allocated
 * #MctAppFilterBuilders.
 *
 * Returns: (transfer full): a copy of @builder
 * Since: 0.2.0
 */
MctAppFilterBuilder *
mct_app_filter_builder_copy (MctAppFilterBuilder *builder)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;
  g_autoptr(MctAppFilterBuilder) copy = NULL;
  MctAppFilterBuilderReal *_copy;

  g_return_val_if_fail (builder != NULL, NULL);

  copy = mct_app_filter_builder_new ();
  _copy = (MctAppFilterBuilderReal *) copy;

  mct_app_filter_builder_clear (copy);
  if (_builder->paths_blacklist != NULL)
    _copy->paths_blacklist = g_ptr_array_ref (_builder->paths_blacklist);
  if (_builder->oars != NULL)
    _copy->oars = g_hash_table_ref (_builder->oars);
  _copy->allow_user_installation = _builder->allow_user_installation;
  _copy->allow_system_installation = _builder->allow_system_installation;

  return g_steal_pointer (&copy);
}

/**
 * mct_app_filter_builder_free:
 * @builder: a heap-allocated #MctAppFilterBuilder
 *
 * Free an #MctAppFilterBuilder originally allocated using
 * mct_app_filter_builder_new(). This must not be called on stack-allocated
 * builders initialised using mct_app_filter_builder_init().
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_free (MctAppFilterBuilder *builder)
{
  g_return_if_fail (builder != NULL);

  mct_app_filter_builder_clear (builder);
  g_free (builder);
}

/**
 * mct_app_filter_builder_end:
 * @builder: an initialised #MctAppFilterBuilder
 *
 * Finish constructing an #MctAppFilter with the given @builder, and return it.
 * The #MctAppFilterBuilder will be cleared as if mct_app_filter_builder_clear()
 * had been called.
 *
 * Returns: (transfer full): a newly constructed #MctAppFilter
 * Since: 0.2.0
 */
MctAppFilter *
mct_app_filter_builder_end (MctAppFilterBuilder *builder)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;
  g_autoptr(MctAppFilter) app_filter = NULL;
  g_auto(GVariantBuilder) oars_builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("a{ss}"));
  GHashTableIter iter;
  gpointer key, value;
  g_autoptr(GVariant) oars_variant = NULL;

  g_return_val_if_fail (_builder != NULL, NULL);
  g_return_val_if_fail (_builder->paths_blacklist != NULL, NULL);
  g_return_val_if_fail (_builder->oars != NULL, NULL);

  /* Ensure the paths list is %NULL-terminated. */
  g_ptr_array_add (_builder->paths_blacklist, NULL);

  /* Build the OARS variant. */
  g_hash_table_iter_init (&iter, _builder->oars);
  while (g_hash_table_iter_next (&iter, &key, &value))
    {
      const gchar *oars_section = key;
      MctAppFilterOarsValue oars_value = GPOINTER_TO_INT (value);
      const gchar *oars_value_strs[] =
        {
          NULL,  /* MCT_APP_FILTER_OARS_VALUE_UNKNOWN */
          "none",
          "mild",
          "moderate",
          "intense",
        };

      g_assert ((int) oars_value >= 0 &&
                (int) oars_value < (int) G_N_ELEMENTS (oars_value_strs));

      if (oars_value_strs[oars_value] != NULL)
        g_variant_builder_add (&oars_builder, "{ss}",
                               oars_section, oars_value_strs[oars_value]);
    }

  oars_variant = g_variant_ref_sink (g_variant_builder_end (&oars_builder));

  /* Build the #MctAppFilter. */
  app_filter = g_new0 (MctAppFilter, 1);
  app_filter->ref_count = 1;
  app_filter->user_id = -1;
  app_filter->app_list = (gchar **) g_ptr_array_free (g_steal_pointer (&_builder->paths_blacklist), FALSE);
  app_filter->app_list_type = MCT_APP_FILTER_LIST_BLACKLIST;
  app_filter->oars_ratings = g_steal_pointer (&oars_variant);
  app_filter->allow_user_installation = _builder->allow_user_installation;
  app_filter->allow_system_installation = _builder->allow_system_installation;

  mct_app_filter_builder_clear (builder);

  return g_steal_pointer (&app_filter);
}

/**
 * mct_app_filter_builder_blacklist_path:
 * @builder: an initialised #MctAppFilterBuilder
 * @path: (type filename): an absolute path to blacklist
 *
 * Add @path to the blacklist of app paths in the filter under construction. It
 * will be canonicalised (without doing any I/O) before being added.
 * The canonicalised @path will not be added again if it’s already been added.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_blacklist_path (MctAppFilterBuilder *builder,
                                       const gchar         *path)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);
  g_return_if_fail (_builder->paths_blacklist != NULL);
  g_return_if_fail (path != NULL);
  g_return_if_fail (g_path_is_absolute (path));

  g_autofree gchar *canonical_path = g_canonicalize_filename (path, "/");

  if (!g_ptr_array_find_with_equal_func (_builder->paths_blacklist,
                                         canonical_path, g_str_equal, NULL))
    g_ptr_array_add (_builder->paths_blacklist, g_steal_pointer (&canonical_path));
}

/**
 * mct_app_filter_builder_blacklist_flatpak_ref:
 * @builder: an initialised #MctAppFilterBuilder
 * @app_ref: a flatpak app ref to blacklist
 *
 * Add @app_ref to the blacklist of flatpak refs in the filter under
 * construction. The @app_ref will not be added again if it’s already been
 * added.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_blacklist_flatpak_ref (MctAppFilterBuilder *builder,
                                              const gchar         *app_ref)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);
  g_return_if_fail (_builder->paths_blacklist != NULL);
  g_return_if_fail (app_ref != NULL);

  if (!g_ptr_array_find_with_equal_func (_builder->paths_blacklist,
                                         app_ref, g_str_equal, NULL))
    g_ptr_array_add (_builder->paths_blacklist, g_strdup (app_ref));
}

/**
 * mct_app_filter_builder_set_oars_value:
 * @builder: an initialised #MctAppFilterBuilder
 * @oars_section: name of the OARS section to set the value for
 * @value: value to set for the @oars_section
 *
 * Set the OARS value for the given @oars_section, indicating the intensity of
 * content covered by that section which the user is allowed to see (inclusive).
 * Any apps which have more intense content in this section should not be usable
 * by the user.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_set_oars_value (MctAppFilterBuilder   *builder,
                                       const gchar           *oars_section,
                                       MctAppFilterOarsValue  value)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);
  g_return_if_fail (_builder->oars != NULL);
  g_return_if_fail (oars_section != NULL && *oars_section != '\0');

  g_hash_table_insert (_builder->oars, g_strdup (oars_section),
                       GUINT_TO_POINTER (value));
}

/**
 * mct_app_filter_builder_set_allow_user_installation:
 * @builder: an initialised #MctAppFilterBuilder
 * @allow_user_installation: %TRUE to allow app installation; %FALSE to
 *    unconditionally disallow it
 *
 * Set whether the user is allowed to install to their flatpak user repository.
 * If this is %TRUE, app installation is still subject to the OARS values
 * (mct_app_filter_builder_set_oars_value()). If it is %FALSE, app installation
 * is unconditionally disallowed for this user.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_set_allow_user_installation (MctAppFilterBuilder *builder,
                                                    gboolean             allow_user_installation)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);

  _builder->allow_user_installation = allow_user_installation;
}

/**
 * mct_app_filter_builder_set_allow_system_installation:
 * @builder: an initialised #MctAppFilterBuilder
 * @allow_system_installation: %TRUE to allow app installation; %FALSE to
 *    unconditionally disallow it
 *
 * Set whether the user is allowed to install to the flatpak system repository.
 * If this is %TRUE, app installation is still subject to the OARS values
 * (mct_app_filter_builder_set_oars_value()). If it is %FALSE, app installation
 * is unconditionally disallowed for this user.
 *
 * Since: 0.2.0
 */
void
mct_app_filter_builder_set_allow_system_installation (MctAppFilterBuilder *builder,
                                                      gboolean             allow_system_installation)
{
  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;

  g_return_if_fail (_builder != NULL);

  _builder->allow_system_installation = allow_system_installation;
}