#include "shell-realm-tracker.h"
#include "shell-realms-private.h"

#define NUM_BUS_SIGNAL_IDS 5

#define REALMS_BUS_NAME "com.subgraph.realms"
#define REALMS_OBJECT_PATH "/com/subgraph/realms"
#define REALMS_MANAGER_INTERFACE "com.subgraph.realms.Manager"

struct _ShellRealmTracker {
    GObject parent;
    GDBusConnection *dbus;
    guint realms_watch_id;
    guint bus_signal_ids[NUM_BUS_SIGNAL_IDS];
    gboolean destroy_in_progress;
};

G_DEFINE_TYPE (ShellRealmTracker, shell_realm_tracker, G_TYPE_OBJECT);

static void
shell_realm_tracker_init (ShellRealmTracker *tracker)
{
  tracker->dbus = NULL;
  tracker->realms_watch_id = 0;
  tracker->destroy_in_progress = FALSE;
}

static void
shell_realm_tracker_class_init (ShellRealmTrackerClass *klass)
{
}

static void
on_realm_bus_signal(GDBusConnection *connection, 
                const gchar *sender_name, 
                const gchar *object_path, 
                const gchar *interface_name, 
                const gchar *signal_name,
                GVariant    *parameters,
                gpointer    user_data)
{
  ShellRealms *realms = shell_realms_get_default();

  const gchar *realm_name = NULL;
  const gchar *description = NULL;
  const gchar *namespace = NULL;
  guint8 status = 0;

  if (g_str_equal (signal_name, "RealmStarted")) {

    g_variant_get (parameters, "(&s&sy)", &realm_name, &namespace, &status);
    shell_realms_on_realm_started (realms, realm_name, namespace, status);

  } else if (g_str_equal (signal_name, "RealmStopped")) {

    g_variant_get (parameters, "(&sy)", &realm_name, &status);
    shell_realms_on_realm_stopped (realms, realm_name);

  } else if (g_str_equal (signal_name, "RealmRemoved")) {

    g_variant_get (parameters, "(&s)", &realm_name);
    shell_realms_on_realm_removed (realms, realm_name);

  } else if (g_str_equal (signal_name, "RealmCurrent")) {

    g_variant_get (parameters, "(&sy)", &realm_name, &status);
    shell_realms_on_realm_current (realms, realm_name);

  } else if (g_str_equal (signal_name, "RealmNew")) {

    g_variant_get (parameters, "(&s&sy)", &realm_name, &description, status);
    shell_realms_on_realm_new (realms, realm_name, description, status);

  } else {
    g_warning("Unexpected signal name '%s' received from realms manager DBUS", signal_name);
  }
}

static void
realm_state_process_elements (ShellRealmTracker *self, GVariant *response)
{

  GVariantIter *iter = NULL;
  const gchar *name = NULL;
  const gchar *description = NULL;
  const gchar *namespace = NULL;
  guchar status = 0;

  ShellRealms *realms = shell_realms_get_default();
  shell_realms_untag_all (realms);

  g_variant_get(response, "(a(ssssy))", &iter);

  // (name, desc, realmfs, namespace, status)
  while (g_variant_iter_next(iter, "(&s&ss&sy)", &name, &description, NULL, &namespace, &status)) {
    shell_realms_update_realm (realms, name, description, namespace, status);
  }

  shell_realms_remove_untagged (realms);
  g_variant_iter_free(iter);
}

static void
request_realm_state_finish(GObject *object, GAsyncResult *result, gpointer data) 
{
  ShellRealmTracker *self = data;

  GError *error = NULL;

  GVariant *response = g_dbus_connection_call_finish (G_DBUS_CONNECTION(object), result, &error);

  if (!response) {
    if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED)) {
      g_warning("MetaRealmDbus: Error calling 'List' bus method: %s", error->message);
    }
    g_clear_error (&error);
    return;
  }

  if (self->destroy_in_progress) {
    g_variant_unref (response);
    return;
  }

  realm_state_process_elements(self, response);
  g_variant_unref(response);
}

static void
set_realm_current_finish (GObject *object, GAsyncResult *result, gpointer data)
{
  GError *error = NULL;
  GVariant *response = g_dbus_connection_call_finish (G_DBUS_CONNECTION(object), result, &error);
  if (!response) {
    if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED)) {
      g_warning("MetaRealmDbus: Error calling 'SetCurrent' bus method: %s", error->message);
    }
    g_clear_error (&error);
    return;
  }
  g_variant_unref (response);
}

static void
call_dbus_method (ShellRealmTracker *self, const gchar *method, GVariant *parameters, GAsyncReadyCallback callback, gpointer user_data)
{
  if (!self->dbus) {
    g_warning("ShellRealmTracker: call_dbus_method(%s) called when no bus connection present", method);
    return;
  }

  g_dbus_connection_call(self->dbus,
                         REALMS_BUS_NAME,
                         REALMS_OBJECT_PATH,
                         REALMS_MANAGER_INTERFACE,
                         method,
                         parameters,
                         NULL,
                         G_DBUS_CALL_FLAGS_NO_AUTO_START,
                         -1,
                         NULL,
                         callback,
                         user_data);
}

static void
request_realm_state(ShellRealmTracker *self)
{
  call_dbus_method (self, "List", NULL, request_realm_state_finish, self);
}

void
shell_realm_tracker_call_set_current (ShellRealmTracker *self, const char *realm_name)
{
  call_dbus_method (self, "SetCurrent", g_variant_new("(s)", realm_name), set_realm_current_finish, NULL);
}


static void
unsubscribe_signals (ShellRealmTracker *self)
{
  for (int i = 0; i < NUM_BUS_SIGNAL_IDS; i++) {
    if (self->bus_signal_ids[i]) {
      if (self->dbus) {
        g_dbus_connection_signal_unsubscribe(self->dbus, self->bus_signal_ids[i]);
      }
      self->bus_signal_ids[i] = 0;
    }
  }
}

static guint
bus_signal_subscribe (ShellRealmTracker *self, const gchar *signal_name)
{
    g_assert(self->dbus);

    return g_dbus_connection_signal_subscribe(self->dbus,
            REALMS_BUS_NAME,
            REALMS_MANAGER_INTERFACE,
            signal_name,
            REALMS_OBJECT_PATH,
            NULL,
            G_DBUS_SIGNAL_FLAGS_NONE,
            on_realm_bus_signal,
            self,
            NULL);
}

static void
subscribe_bus_signals (ShellRealmTracker *self)
{
    if (self->dbus) {
        int idx = 0;
        self->bus_signal_ids[idx++] = bus_signal_subscribe(self, "RealmStarted");
        self->bus_signal_ids[idx++] = bus_signal_subscribe(self, "RealmStopped");
        self->bus_signal_ids[idx++] = bus_signal_subscribe(self, "RealmCurrent");
        self->bus_signal_ids[idx++] = bus_signal_subscribe(self, "RealmNew");
        self->bus_signal_ids[idx++] = bus_signal_subscribe(self, "RealmRemoved");
        g_assert(idx == NUM_BUS_SIGNAL_IDS);
    }
}

static void
on_realm_manager_appeared (GDBusConnection *connection, const gchar *name, const gchar *name_owner, gpointer user_data)
{
  ShellRealmTracker *self = user_data;

  // Avoid processing spurious events while destroying 'self'
  if (self->destroy_in_progress) {
      return;
  }

  if (!self->dbus) {
      self->dbus = g_object_ref(connection);
      subscribe_bus_signals (self);
  } else {
      g_warning("Realm tracker already has a connection in on_realm_manager_appeared()");
  }

  request_realm_state (self);
}


static void
on_realm_manager_vanished (GDBusConnection *connection, const gchar *name, gpointer user_data)
{
  ShellRealmTracker *self = user_data;

  // Avoid processing spurious events while destroying 'self'
  if (self->destroy_in_progress) {
    return;
  }

  if (!connection) {
    g_clear_object (&self->dbus);
  }

  unsubscribe_signals(self);
}

/**
 * shell_realm_tracker_get_default:
 *
 * Return Value: (transfer none): The global #ShellRealmTracker singleton
 */
ShellRealmTracker *
shell_realm_tracker_get_default(void)
{
  static ShellRealmTracker *instance;
  if (instance == NULL) {
    instance = g_object_new (SHELL_TYPE_REALM_TRACKER, NULL);
  }
  return instance;
}

void shell_realm_tracker_start ()
{
  ShellRealmTracker *tracker = shell_realm_tracker_get_default();

  if (tracker->realms_watch_id) {
    g_warning ("ShellRealmTracker: shell_realm_tracker_start() called when already started");
    return;
  }

  tracker->realms_watch_id = g_bus_watch_name(G_BUS_TYPE_SYSTEM,
                                           REALMS_BUS_NAME,
                                           G_BUS_NAME_WATCHER_FLAGS_NONE,
                                           on_realm_manager_appeared,
                                           on_realm_manager_vanished,
                                           tracker,
                                           g_free);

}

void
shell_realm_tracker_destroy(ShellRealmTracker *self)
{
  if (self->dbus) {
    unsubscribe_signals (self);
    g_clear_object (&self->dbus);
  }

  // event handlers check this and will bail early in case there are
  // any in queue. see docs for g_bus_unwatch_name()
  self->destroy_in_progress = TRUE;

  // frees 'self' in destroy notifier
  g_bus_unwatch_name(self->realms_watch_id);

}