[evolution-data-server] Introduce e_backend_is_destination_reachable()

[Milan Crha <mcrha src gnome org>]

commit 2bb944994cc72922d2c0e690416797415e5e64d0
Author: Milan Crha <mcrha redhat com>
Date:   Wed Feb 13 09:22:07 2013 +0100

    Introduce e_backend_is_destination_reachable()
    
    This new function, together with implementation of
    e_backend_get_destination_address() on the backend side,
    can be used to check whether the backend's destination
    is currently reachable. Default implementation reports
    backend as always reachable, aka local.

 configure.ac            |    2 +-
 libebackend/e-backend.c |  103 +++++++++++++++++++++++++++++++++++++++++++++++
 libebackend/e-backend.h |   14 ++++++
 3 files changed, 118 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 710fa98..4d8f986 100644
--- a/configure.ac
+++ b/configure.ac
@@ -130,7 +130,7 @@ LIBCAMEL_CURRENT=43
 LIBCAMEL_REVISION=0
 LIBCAMEL_AGE=0
 
-LIBEBACKEND_CURRENT=6
+LIBEBACKEND_CURRENT=7
 LIBEBACKEND_REVISION=0
 LIBEBACKEND_AGE=0
 
diff --git a/libebackend/e-backend.c b/libebackend/e-backend.c
index 3543a94..6705be7 100644
--- a/libebackend/e-backend.c
+++ b/libebackend/e-backend.c
@@ -256,6 +256,16 @@ backend_authenticate_finish (EBackend *backend,
 	return !g_simple_async_result_propagate_error (simple, error);
 }
 
+static gboolean
+backend_get_destination_address (EBackend *backend,
+				 gchar **host,
+				 guint16 *port)
+{
+	/* default implementation returns FALSE, indicating
+	   no remote destination being used for this backend */
+	return FALSE;
+}
+
 static void
 e_backend_class_init (EBackendClass *class)
 {
@@ -272,6 +282,7 @@ e_backend_class_init (EBackendClass *class)
 	class->authenticate_sync = backend_authenticate_sync;
 	class->authenticate = backend_authenticate;
 	class->authenticate_finish = backend_authenticate_finish;
+	class->get_destination_address = backend_get_destination_address;
 
 	g_object_class_install_property (
 		object_class,
@@ -644,3 +655,95 @@ e_backend_trust_prompt_finish (EBackend *backend,
 
 	return E_TRUST_PROMPT_RESPONSE_UNKNOWN;
 }
+
+/**
+ * e_backend_get_destination_address:
+ * @backend: an #EBackend instance
+ * @host: (out): destination server host name
+ * @port: (out): destination server port
+ *
+ * Provides destination server host name and port to which
+ * the backend connects. This is used to determine required
+ * connection point for e_backend_destination_is_reachable().
+ * The @host is a newly allocated string, which will be freed
+ * with g_free(). When @backend sets both @host and @port, then
+ * it should return %TRUE, indicating it's a remote backend.
+ * Default implementation returns %FALSE, which is treated
+ * like the backend is local, no checking for server reachability
+ * is possible.
+ *
+ * Returns: %TRUE, when it's a remote backend and provides both
+ *   @host and @port; %FALSE otherwise.
+ *
+ * Since: 3.8
+ **/
+gboolean
+e_backend_get_destination_address (EBackend *backend,
+				   gchar **host,
+				   guint16 *port)
+{
+	EBackendClass *klass;
+
+	g_return_val_if_fail (E_IS_BACKEND (backend), FALSE);
+	g_return_val_if_fail (host != NULL, FALSE);
+	g_return_val_if_fail (port != NULL, FALSE);
+
+	klass = E_BACKEND_GET_CLASS (backend);
+	g_return_val_if_fail (klass->get_destination_address != NULL, FALSE);
+
+	return klass->get_destination_address (backend, host, port);
+}
+
+/**
+ * e_backend_is_destination_reachable:
+ * @backend: an #EBackend instance
+ * @cancellable: a #GCancellable instance, or %NULL
+ * @error: a #GError for errors, or %NULL
+ *
+ * Checks whether the @backend<!-- -->'s destination server, as returned
+ * by e_backend_get_destination_address(), is reachable.
+ * If the e_backend_get_destination_address() returns %FALSE, this function
+ * returns %TRUE, meaning the destination is always reachable.
+ * This uses #GNetworkMonitor<!-- -->'s g_network_monitor_can_reach()
+ * for reachability tests.
+ *
+ * Returns: %TRUE, when destination server address is reachable or
+ *    the backend doesn't provide destination address; %FALSE if
+ *    the backend destination server cannot be reached currently.
+ *
+ * Since: 3.8
+ **/
+gboolean
+e_backend_is_destination_reachable (EBackend *backend,
+				    GCancellable *cancellable,
+				    GError **error)
+{
+	gboolean reachable = TRUE;
+	gchar *host = NULL;
+	guint16 port = 0;
+
+	g_return_val_if_fail (E_IS_BACKEND (backend), FALSE);
+
+	if (e_backend_get_destination_address (backend, &host, &port)) {
+		g_warn_if_fail (host != NULL);
+
+		if (host) {
+			GNetworkMonitor *network_monitor;
+			GSocketConnectable *connectable;
+
+			network_monitor = g_network_monitor_get_default ();
+
+			connectable = g_network_address_new (host, port);
+			if (connectable) {
+				reachable = g_network_monitor_can_reach (network_monitor, connectable, cancellable, error);
+				g_object_unref (connectable);
+			} else {
+				reachable = FALSE;
+			}
+		}
+	}
+
+	g_free (host);
+
+	return reachable;
+}
diff --git a/libebackend/e-backend.h b/libebackend/e-backend.h
index 65b8e8b..f7400c7 100644
--- a/libebackend/e-backend.h
+++ b/libebackend/e-backend.h
@@ -83,6 +83,11 @@ struct _EBackendClass {
 						 GAsyncResult *result,
 						 GError **error);
 
+	gboolean	(*get_destination_address)
+						(EBackend *backend,
+						 gchar **host,
+						 guint16 *port);
+
 	gpointer reserved[13];
 };
 
@@ -120,6 +125,15 @@ ETrustPromptResponse
 						 GAsyncResult *result,
 						 GError **error);
 
+gboolean	e_backend_get_destination_address
+						(EBackend *backend,
+						 gchar **host,
+						 guint16 *port);
+gboolean	e_backend_is_destination_reachable
+						(EBackend *backend,
+						 GCancellable *cancellable,
+						 GError **error);
+
 G_END_DECLS
 
 #endif /* E_BACKEND_H */