path: root/src/goabackend/goaprovider.c

/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/*
 * Copyright (C) 2011 Red Hat, 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 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., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Author: David Zeuthen <davidz@redhat.com>
 */

#include "config.h"
#include <glib/gi18n-lib.h>
#include <gnome-keyring.h>

#include "goaprovider.h"
#include "goagoogleprovider.h"
#include "goafacebookprovider.h"
#include "goayahooprovider.h"
#include "goatwitterprovider.h"
#include "goagenericmailprovider.h"

#include "goaeditablelabel.h"

/**
 * SECTION:goaprovider
 * @title: GoaProvider
 * @short_description: Abstract base class for providers
 *
 * #GoaProvider is the base type for all providers.
 */

static gboolean goa_provider_ensure_credentials_sync_real (GoaProvider   *provider,
                                                           GoaObject     *object,
                                                           gint          *out_expires_in,
                                                           GCancellable  *cancellable,
                                                           GError       **error);

static gboolean goa_provider_build_object_real (GoaProvider         *provider,
                                                GoaObjectSkeleton   *object,
                                                GKeyFile            *key_file,
                                                const gchar         *group,
                                                GError             **error);

static void goa_provider_show_account_real (GoaProvider         *provider,
                                            GoaClient           *client,
                                            GoaObject           *object,
                                            GtkBox              *vbox,
                                            GtkTable            *table);

G_DEFINE_ABSTRACT_TYPE (GoaProvider, goa_provider, G_TYPE_OBJECT);

static void
goa_provider_init (GoaProvider *client)
{
}

static void
goa_provider_class_init (GoaProviderClass *klass)
{
  klass->build_object = goa_provider_build_object_real;
  klass->ensure_credentials_sync = goa_provider_ensure_credentials_sync_real;
  klass->show_account = goa_provider_show_account_real;
}

/**
 * goa_provider_get_provider_type:
 * @provider: A #GoaProvider.
 *
 * Gets the type of @provider.
 *
 * This is a pure virtual method - a subclass must provide an
 * implementation.
 *
 * Returns: (transfer none): A string owned by @provider, do not free.
 */
const gchar *
goa_provider_get_provider_type (GoaProvider *provider)
{
  g_return_val_if_fail (GOA_IS_PROVIDER (provider), NULL);
  return GOA_PROVIDER_GET_CLASS (provider)->get_provider_type (provider);
}

/**
 * goa_provider_get_name:
 * @provider: A #GoaProvider.
 *
 * Gets a localized name for @provider that is suitable for display in
 * an user interface.
 *
 * This is a pure virtual method - a subclass must provide an
 * implementation.
 *
 * Returns: (transfer none): A string owned by @provider, do not free.
 */
const gchar *
goa_provider_get_name (GoaProvider *provider)
{
  g_return_val_if_fail (GOA_IS_PROVIDER (provider), NULL);
  return GOA_PROVIDER_GET_CLASS (provider)->get_name (provider);
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_add_account:
 * @provider: A #GoaProvider.
 * @client: A #GoaClient.
 * @dialog: A #GtkDialog.
 * @vbox: A vertically oriented #GtkBox to put content in.
 * @error: Return location for error or %NULL.
 *
 * This method brings up the user interface necessary to create a new
 * account on @client of the type for @provider, interacts with the
 * user to get all information needed and creates the account.
 *
 * The passed in @dialog widget is guaranteed to be visible with @vbox
 * being empty and the only visible widget in @dialog's content
 * area. The dialog has exactly one action widget, a cancel button
 * with response id GTK_RESPONSE_CANCEL. Implementations are free to
 * add additional action widgets, as needed.
 *
 * If an account was successfully created, a #GoaObject for the
 * created account is returned. If @dialog is dismissed, %NULL is
 * returned and @error is set to %GOA_ERROR_DIALOG_DISMISSED. If an
 * account couldn't be created then @error is set.
 *
 * The caller will always show an error dialog if @error is set unless
 * the error is %GOA_ERROR_DIALOG_DISMISSED.
 *
 * Implementations should run the <link
 * linkend="g_main_context_default">default main loop</link> while
 * interacting with the user and may do so using e.g. gtk_dialog_run()
 * on @dialog.
 *
 * This is a pure virtual method - a subclass must provide an
 * implementation.
 *
 * Returns: The #GoaObject for the created account (must be relased
 *   with g_object_unref()) or %NULL if @error is set.
 */
GoaObject *
goa_provider_add_account (GoaProvider  *provider,
                          GoaClient    *client,
                          GtkDialog    *dialog,
                          GtkBox       *vbox,
                          GError      **error)
{
  GoaObject *ret;

  g_return_val_if_fail (GOA_IS_PROVIDER (provider), NULL);
  g_return_val_if_fail (GOA_IS_CLIENT (client), NULL);
  g_return_val_if_fail (GTK_IS_DIALOG (dialog), NULL);
  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

  ret = GOA_PROVIDER_GET_CLASS (provider)->add_account (provider, client, dialog, vbox, error);

  g_warn_if_fail ((ret == NULL && (error == NULL || *error != NULL)) || GOA_IS_OBJECT (ret));

  return ret;
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_refresh_account:
 * @provider: A #GoaProvider.
 * @client: A #GoaClient.
 * @object: A #GoaObject with a #GoaAccount interface.
 * @parent: (allow-none): Transient parent of dialogs or %NULL.
 * @error: Return location for error or %NULL.
 *
 * This method brings up the user interface necessary for refreshing
 * the credentials for the account specified by @object. This
 * typically involves having the user log in to the account again.
 *
 * Implementations should use @parent (unless %NULL) as the transient
 * parent of any created windows/dialogs.
 *
 * Implementations should run the <link
 * linkend="g_main_context_default">default main loop</link> while
 * interacting with the user.
 *
 * This is a pure virtual method - a subclass must provide an
 * implementation.
 *
 * Returns: %TRUE if the account has been refreshed, %FALSE if @error
 * is set.
 */
gboolean
goa_provider_refresh_account (GoaProvider  *provider,
                              GoaClient    *client,
                              GoaObject    *object,
                              GtkWindow    *parent,
                              GError      **error)
{
  g_return_val_if_fail (GOA_IS_PROVIDER (provider), FALSE);
  g_return_val_if_fail (GOA_IS_CLIENT (client), FALSE);
  g_return_val_if_fail (GOA_IS_OBJECT (object) && goa_object_peek_account (object) != NULL, FALSE);
  g_return_val_if_fail (parent == NULL || GTK_IS_WINDOW (parent), FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);

  return GOA_PROVIDER_GET_CLASS (provider)->refresh_account (provider, client, object, parent, error);
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_show_account:
 * @provider: A #GoaProvider.
 * @client: A #GoaClient.
 * @object: A #GoaObject with a #GoaAccount interface.
 * @dialog: A #GtkDialog.
 * @vbox: A vertically oriented #GtkBox to put content in.
 * @table: A table which is the first element of vbox.
 *
 * Method used to add widgets in the control panel for the account
 * represented by @object.
 *
 * This is a virtual method with an implementation that adds widgets
 * for editing the name and the icon. A subclass should chain up
 * (before adding their own widgets to @vbox and @table) if they want
 * to expose such functionality.
 */
void
goa_provider_show_account (GoaProvider         *provider,
                           GoaClient           *client,
                           GoaObject           *object,
                           GtkBox              *vbox,
                           GtkTable            *table)
{
  g_return_if_fail (GOA_IS_PROVIDER (provider));
  g_return_if_fail (GOA_IS_CLIENT (client));
  g_return_if_fail (GOA_IS_OBJECT (object) && goa_object_peek_account (object) != NULL);
  g_return_if_fail (GTK_IS_BOX (vbox));
  g_return_if_fail (GTK_IS_TABLE (table));

  GOA_PROVIDER_GET_CLASS (provider)->show_account (provider, client, object, vbox, table);
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_util_add_row_widget:
 * @table: A #GtkTable.
 * @label_text: The text to insert on the left side.
 * @widget: A widget to insert on the right side.
 *
 * Utility function to add @label_text and @widget to @table.
 */
void
goa_util_add_row_widget (GtkTable     *table,
                         const gchar  *label_text,
                         GtkWidget    *widget)
{
  GtkWidget *label;
  gchar *s;
  guint num_rows;

  g_return_if_fail (GTK_IS_TABLE (table));
  g_return_if_fail (label_text != NULL);
  g_return_if_fail (GTK_IS_WIDGET (widget));

  s = g_strdup_printf ("<span foreground=\"#555555\">%s</span>", label_text);

  gtk_table_get_size (table, &num_rows, NULL);

  label = gtk_label_new (NULL);
  gtk_label_set_markup (GTK_LABEL (label), s);
  gtk_misc_set_alignment (GTK_MISC (label), 1.0, 0.5);
  gtk_table_attach (table, label,
                    0, 1,
                    num_rows, num_rows + 1,
                    GTK_FILL, GTK_FILL, 0, 0);
  gtk_table_attach (table, widget,
                    1, 2,
                    num_rows, num_rows + 1,
                    GTK_FILL, GTK_FILL, 0, 0);

  g_free (s);
}

/**
 * goa_util_add_row:
 * @table: A #GtkTable.
 * @label_text: The text to insert on the left side.
 * @value_markup: The markup to insert on the right side.
 *
 * Utility function to add @label_text and @value_text to @table.
 */
void
goa_util_add_row (GtkTable     *table,
                  const gchar  *label_text,
                  const gchar  *value_markup)
{
  GtkWidget *label;
  label = gtk_label_new (NULL);
  gtk_label_set_markup (GTK_LABEL (label), value_markup);
  gtk_misc_set_alignment (GTK_MISC (label), 0.0, 0.5);
  gtk_label_set_selectable (GTK_LABEL (label), TRUE);
  goa_util_add_row_widget (table, label_text, label);
}

static void
on_name_editing_done (GoaEditableLabel *editable_label,
                      gpointer          user_data)
{
  GoaObject *object = GOA_OBJECT (user_data);
  GoaAccount *account;

  account = goa_object_peek_account (object);
  goa_account_call_set_name (account,
                             goa_editable_label_get_text (editable_label),
                             NULL, /* GCancellable */
                             NULL, NULL); /* callback, user_data */
}

static void
goa_provider_show_account_real (GoaProvider         *provider,
                                GoaClient           *client,
                                GoaObject           *object,
                                GtkBox              *vbox,
                                GtkTable            *table)
{
  GoaAccount *account;
  GtkWidget *elabel;
  guint num_rows;

  account = goa_object_peek_account (object);

  gtk_table_get_size (table, &num_rows, NULL);

  elabel = goa_editable_label_new ();
  goa_editable_label_set_text (GOA_EDITABLE_LABEL (elabel), goa_account_get_name (account));
  goa_editable_label_set_editable (GOA_EDITABLE_LABEL (elabel), TRUE);
  goa_editable_label_set_scale (GOA_EDITABLE_LABEL (elabel), 1.2);
  goa_editable_label_set_weight (GOA_EDITABLE_LABEL (elabel), 700);
  g_signal_connect (elabel, "editing-done", G_CALLBACK (on_name_editing_done), object);

  gtk_table_attach (table, elabel,
                    1, 2,
                    num_rows, num_rows + 1,
                    GTK_FILL, GTK_FILL, 0, 0);
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_build_object:
 * @provider: A #GoaProvider.
 * @object: The #GoaObjectSkeleton that is being built.
 * @key_file: The #GKeyFile with configuation data.
 * @group: The group in @key_file to get data from.
 * @error: Return location for error or %NULL.
 *
 * This method is called when construction account #GoaObject<!-- -->
 * from configuration data - it basically provides a way to add
 * provider-specific information.
 *
 * The passed in @object will have a #GoaAccount interface
 * set. Implementations should validate and use data from @key_file to
 * add more interfaces to @object.
 *
 * Note that this may be called on already exported objects - for
 * example on configuration files reload.
 *
 * This is a pure virtual method - a subclass must provide an
 * implementation.
 *
 * Returns: %TRUE if data was valid, %FALSE if @error is set.
 */
gboolean
goa_provider_build_object (GoaProvider         *provider,
                           GoaObjectSkeleton   *object,
                           GKeyFile            *key_file,
                           const gchar         *group,
                           GError             **error)
{
  g_return_val_if_fail (GOA_IS_PROVIDER (provider), FALSE);
  g_return_val_if_fail (GOA_IS_OBJECT_SKELETON (object) && goa_object_peek_account (GOA_OBJECT (object)) != NULL, FALSE);
  g_return_val_if_fail (key_file != NULL, FALSE);
  g_return_val_if_fail (group != NULL, FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
  return GOA_PROVIDER_GET_CLASS (provider)->build_object (provider, object, key_file, group, error);
}

/* ---------------------------------------------------------------------------------------------------- */

typedef struct
{
  GoaObject *object;
  gint expires_in;
} EnsureCredentialsData;

static EnsureCredentialsData *
ensure_credentials_data_new (GoaObject *object)
{
  EnsureCredentialsData *data;
  data = g_new0 (EnsureCredentialsData, 1);
  data->object = g_object_ref (object);
  return data;
}

static void
ensure_credentials_data_free (EnsureCredentialsData *data)
{
  g_object_unref (data->object);
  g_free (data);
}

static void
ensure_credentials_in_thread_func (GSimpleAsyncResult *simple,
                                   GObject            *object,
                                   GCancellable       *cancellable)
{
  EnsureCredentialsData *data;
  GError *error;

  data = g_simple_async_result_get_op_res_gpointer (simple);

  error = NULL;
  if (!goa_provider_ensure_credentials_sync (GOA_PROVIDER (object),
                                             data->object,
                                             &data->expires_in,
                                             cancellable,
                                             &error))
    g_simple_async_result_take_error (simple, error);
}


/**
 * goa_provider_ensure_credentials:
 * @provider: A #GoaProvider.
 * @object: A #GoaObject with a #GoaAccount interface.
 * @cancellable: (allow-none): A #GCancellable or %NULL.
 * @callback: The function to call when the request is satisfied.
 * @user_data: Pointer to pass to @callback.
 *
 * Ensures that credentials for @object are still valid.
 *
 * When the result is ready, @callback will be called in the the <link
 * linkend="g-main-context-push-thread-default">thread-default main
 * loop</link> this function was called from. You can then call
 * goa_provider_ensure_credentials_finish() to get the result
 * of the operation.
 *
 * This is a virtual method where the default implemention simply returns
 * the %GOA_ERROR_NOT_SUPPORTED error. A subclass may provide
 * another implementation.
 */
void
goa_provider_ensure_credentials (GoaProvider          *provider,
                                 GoaObject            *object,
                                 GCancellable         *cancellable,
                                 GAsyncReadyCallback   callback,
                                 gpointer              user_data)
{
  GSimpleAsyncResult *simple;

  g_return_if_fail (GOA_IS_PROVIDER (provider));
  g_return_if_fail (GOA_IS_OBJECT (object));
  g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));

  simple = g_simple_async_result_new (G_OBJECT (provider),
                                      callback,
                                      user_data,
                                      goa_provider_ensure_credentials);
  g_simple_async_result_set_op_res_gpointer (simple,
                                             ensure_credentials_data_new (object),
                                             (GDestroyNotify) ensure_credentials_data_free);
  g_simple_async_result_run_in_thread (simple,
                                       ensure_credentials_in_thread_func,
                                       G_PRIORITY_DEFAULT,
                                       cancellable);
  g_object_unref (simple);
}

/**
 * goa_provider_ensure_credentials_finish:
 * @provider: A #GoaProvider.
 * @out_expires_in: (out): Return location for how long the expired credentials are good for (0 if unknown) or %NULL.
 * @res: A #GAsyncResult obtained from the #GAsyncReadyCallback passed to goa_provider_ensure_credentials().
 * @error: Return location for error or %NULL.
 *
 * Finishes an operation started with goa_provider_ensure_credentials().
 *
 * Returns: %TRUE if the credentials for the passed #GoaObject are valid, %FALSE if @error is set.
 */
gboolean
goa_provider_ensure_credentials_finish (GoaProvider  *provider,
                                                gint                *out_expires_in,
                                                GAsyncResult        *res,
                                                GError             **error)
{
  GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
  gboolean ret;
  EnsureCredentialsData *data;

  ret = FALSE;

  g_return_val_if_fail (GOA_IS_PROVIDER (provider), FALSE);
  g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);

  g_warn_if_fail (g_simple_async_result_get_source_tag (simple) == goa_provider_ensure_credentials);

  if (g_simple_async_result_propagate_error (simple, error))
    goto out;

  ret = TRUE;
  data = g_simple_async_result_get_op_res_gpointer (simple);
  if (out_expires_in != NULL)
    *out_expires_in = data->expires_in;

 out:
  return ret;
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_ensure_credentials_sync:
 * @provider: A #GoaProvider.
 * @object: A #GoaObject with a #GoaAccount interface.
 * @out_expires_in: (out): Return location for how long the expired credentials are good for (0 if unknown) or %NULL.
 * @cancellable: (allow-none): A #GCancellable or %NULL.
 * @error: Return location for error or %NULL.
 *
 * Like goa_provider_ensure_credentials() but blocks the
 * calling thread until an answer is received.
 *
 * Returns: %TRUE if the credentials for the passed #GoaObject are valid, %FALSE if @error is set.
 */
gboolean
goa_provider_ensure_credentials_sync (GoaProvider     *provider,
                                      GoaObject       *object,
                                      gint            *out_expires_in,
                                      GCancellable    *cancellable,
                                      GError         **error)
{
  g_return_val_if_fail (GOA_IS_PROVIDER (provider), FALSE);
  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
  return GOA_PROVIDER_GET_CLASS (provider)->ensure_credentials_sync (provider, object, out_expires_in, cancellable, error);
}

static gboolean
goa_provider_ensure_credentials_sync_real (GoaProvider   *provider,
                                           GoaObject     *object,
                                           gint          *out_expires_in,
                                           GCancellable  *cancellable,
                                           GError       **error)
{
  g_set_error (error,
               GOA_ERROR,
               GOA_ERROR_NOT_SUPPORTED,
               _("ensure_credentials_sync not been implemented on type %s"),
               g_type_name (G_TYPE_FROM_INSTANCE (provider)));
  return FALSE;
}

static gboolean
goa_provider_build_object_real (GoaProvider         *provider,
                                GoaObjectSkeleton   *object,
                                GKeyFile            *key_file,
                                const gchar         *group,
                                GError             **error)
{
  /* does nothing */
  return TRUE;
}

/* ---------------------------------------------------------------------------------------------------- */

static void
ensure_ep_and_builtins (void)
{
  static gsize once_init_value = 0;

  if (g_once_init_enter (&once_init_value))
    {
      GIOExtensionPoint *extension_point;
      static volatile GType type = 0;

      extension_point = g_io_extension_point_register (GOA_PROVIDER_EXTENSION_POINT_NAME);
      g_io_extension_point_set_required_type (extension_point, GOA_TYPE_PROVIDER);

      type = GOA_TYPE_GOOGLE_PROVIDER;
      type = GOA_TYPE_FACEBOOK_PROVIDER;
      type = GOA_TYPE_YAHOO_PROVIDER;
      type = GOA_TYPE_TWITTER_PROVIDER;
      type = GOA_TYPE_GENERIC_MAIL_PROVIDER;
      type = type; /* for -Wunused-but-set-variable */

      g_once_init_leave (&once_init_value, 1);
    }
}


/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_get_for_provider_type:
 * @provider_type: A provider type.
 *
 * Looks up the %GOA_PROVIDER_EXTENSION_POINT_NAME extension
 * point and returns a newly created #GoaProvider for
 * @provider_type, if any.
 *
 * Returns: (transfer full): A #GoaProvider (that must be freed
 * with g_object_unref()) or %NULL if not found.
 */
GoaProvider *
goa_provider_get_for_provider_type (const gchar *provider_type)
{
  GIOExtension *extension;
  GIOExtensionPoint *extension_point;
  GoaProvider *ret;

  ensure_ep_and_builtins ();

  ret = NULL;

  extension_point = g_io_extension_point_lookup (GOA_PROVIDER_EXTENSION_POINT_NAME);
  extension = g_io_extension_point_get_extension_by_name (extension_point, provider_type);
  if (extension != NULL)
    ret = GOA_PROVIDER (g_object_new (g_io_extension_get_type (extension), NULL));
  return ret;
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_get_all:
 *
 * Looks up the %GOA_PROVIDER_EXTENSION_POINT_NAME extension
 * point and returns a newly created #GoaProvider for each
 * provider type encountered.
 *
 * Returns: (transfer full) (element-type GoaProvider): A list
 *   of element providers that should be freed with g_list_free()
 *   after each element has been freed with g_object_unref().
 */
GList *
goa_provider_get_all (void)
{
  GList *ret;
  GList *extensions;
  GList *l;
  GIOExtensionPoint *extension_point;

  ensure_ep_and_builtins ();

  ret = NULL;
  extension_point = g_io_extension_point_lookup (GOA_PROVIDER_EXTENSION_POINT_NAME);
  extensions = g_io_extension_point_get_extensions (extension_point);
  /* TODO: what if there are two extensions with the same name? */
  for (l = extensions; l != NULL; l = l->next)
    {
      GIOExtension *extension = l->data;
      ret = g_list_prepend (ret, g_object_new (g_io_extension_get_type (extension), NULL));
    }
  ret = g_list_reverse (ret);
  return ret;
}

/* ---------------------------------------------------------------------------------------------------- */

static const GnomeKeyringPasswordSchema keyring_password_schema =
{
  GNOME_KEYRING_ITEM_GENERIC_SECRET,
  {
    { "goa-identity", GNOME_KEYRING_ATTRIBUTE_TYPE_STRING },
    { NULL, 0 }
  }
};

/**
 * goa_provider_store_credentials_sync:
 * @provider: A #GoaProvider.
 * @object: The account to store credentials for.
 * @credentials: The credentials to store.
 * @cancellable: (allow-none): A #GCancellable or %NULL.
 * @error: Return location for error or %NULL.
 *
 * Stores @credentials for @identity in the key-ring. If @credentials
 * is floating, it is consumed.
 *
 * The calling thread is blocked while waiting for a reply.
 *
 * This is a convenience method (not virtual) that subclasses can use.
 *
 * Returns: %TRUE if the credentials was successfully stored, %FALSE
 * if @error is set.
 */
gboolean
goa_provider_store_credentials_sync (GoaProvider   *provider,
                                     GoaObject     *object,
                                     GVariant      *credentials,
                                     GCancellable  *cancellable,
                                     GError       **error)
{
  gboolean ret;
  gchar *credentials_str;
  gchar *password_description;
  gchar *password_key;
  GnomeKeyringResult result;
  const gchar *identity;

  g_return_val_if_fail (GOA_IS_PROVIDER (provider), FALSE);
  g_return_val_if_fail (GOA_IS_OBJECT (object) && goa_object_peek_account (object) != NULL, FALSE);
  g_return_val_if_fail (credentials != NULL, FALSE);
  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), FALSE);
  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);

  /* TODO: use GCancellable */
  ret = FALSE;

  identity = goa_account_get_id (goa_object_peek_account (object));

  credentials_str = g_variant_print (credentials, TRUE);
  g_variant_ref_sink (credentials);
  g_variant_unref (credentials);

  password_key = g_strdup_printf ("%s:%s",
                                  goa_provider_get_provider_type (GOA_PROVIDER (provider)),
                                  identity);
  password_description = g_strdup_printf (_("GOA %s credentials for identity %s"),
                                          goa_provider_get_provider_type (GOA_PROVIDER (provider)),
                                          identity);
  result = gnome_keyring_store_password_sync (&keyring_password_schema,
                                              NULL, /* default keyring */
                                              password_description,
                                              credentials_str,
                                              "goa-identity", password_key,
                                              NULL);
  if (result != GNOME_KEYRING_RESULT_OK)
    {
      g_set_error (error,
                   GOA_ERROR,
                   GOA_ERROR_FAILED, /* TODO: more specific */
                   _("Failed to store credentials in the keyring: %s"),
                   gnome_keyring_result_to_message (result));
      goto out;
    }

  ret = TRUE;

 out:
  g_free (credentials_str);
  g_free (password_key);
  g_free (password_description);
  return ret;
}

/* ---------------------------------------------------------------------------------------------------- */

/**
 * goa_provider_lookup_credentials_sync:
 * @provider: A #GoaProvider.
 * @object: The account to store credentials for.
 * @cancellable: (allow-none): A #GCancellable or %NULL.
 * @error: Return location for error or %NULL.
 *
 * Looks up credentials in the keyring for @identity previously stored
 * with goa_provider_store_credentials().
 *
 * The calling thread is blocked while waiting for a reply.
 *
 * This is a convenience method (not virtual) that subclasses can use.
 *
 * Returns: (transfer full): A #GVariant (never floating)
 * with credentials or %NULL if @error is set. Free with
 * g_variant_unref().
 */
GVariant *
goa_provider_lookup_credentials_sync (GoaProvider   *provider,
                                      GoaObject     *object,
                                      GCancellable  *cancellable,
                                      GError       **error)
{
  gchar *password_key;
  GVariant *ret;
  GnomeKeyringResult result;
  gchar *returned_password;
  const gchar *identity;

  g_return_val_if_fail (GOA_IS_PROVIDER (provider), NULL);
  g_return_val_if_fail (GOA_IS_OBJECT (object) && goa_object_peek_account (object) != NULL, FALSE);
  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), NULL);
  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

  ret = NULL;
  password_key = NULL;
  returned_password = NULL;

  identity = goa_account_get_id (goa_object_peek_account (object));

  password_key = g_strdup_printf ("%s:%s",
                                  goa_provider_get_provider_type (GOA_PROVIDER (provider)),
                                  identity);

  result = gnome_keyring_find_password_sync (&keyring_password_schema,
                                             &returned_password,
                                             "goa-identity", password_key,
                                             NULL);
  if (result != GNOME_KEYRING_RESULT_OK)
    {
      g_set_error (error,
                   GOA_ERROR,
                   GOA_ERROR_FAILED, /* TODO: more specific */
                   _("Failed to retrieve credentials from the keyring: %s"),
                   gnome_keyring_result_to_message (result));
      goto out;
    }

  ret = g_variant_parse (NULL, /* GVariantType */
                         returned_password,
                         NULL, /* limit */
                         NULL, /* endptr */
                         error);
  if (ret == NULL)
    {
      g_prefix_error (error, _("Error parsing result obtained from the keyring: "));
      goto out;
    }

  if (g_variant_is_floating (ret))
    g_variant_ref_sink (ret);

 out:
  gnome_keyring_free_password (returned_password);
  g_free (password_key);
  return ret;
}