[shotwell/wip/phako/external-gstreamer: 38/43] wip: external helper launch helper

[Jens Georg <jensgeorg src gnome org>]

commit 03d9d6ee656df708c47db4c6631a0223693bc2b2
Author: Jens Georg <mail jensge org>
Date:   Sat May 11 17:25:29 2019 +0200

    wip: external helper launch helper

 src/ExternalHelper.vala | 94 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/meson.build         |  3 +-
 2 files changed, 96 insertions(+), 1 deletion(-)
---
diff --git a/src/ExternalHelper.vala b/src/ExternalHelper.vala
new file mode 100644
index 00000000..7002de53
--- /dev/null
+++ b/src/ExternalHelper.vala
@@ -0,0 +1,94 @@
+/*
+ * - Proxies interface access
+ */
+public class ExternalProxy<G> : Object, Initable {
+    private G remote;
+    private DBusServer server;
+    private Subprocess remote_process;
+    private SourceFunc saved_get_remote_callback;
+
+    public string dbus_path { get; construct set; }
+    public string remote_helper_path { get; construct set; }
+
+    public ExternalProxy(string dbus_path, string helper_path) throws Error {
+        Object(dbus_path: dbus_path, remote_helper_path : helper_path);
+        init();
+    }
+
+    public bool init(Cancellable? cancellable) throws GLib.Error {
+        var address = "unix:tmpdir=%s".printf(Environment.get_tmp_dir());
+        var observer = new DBusAuthObserver();
+        observer.authorize_authenticated_peer.connect(this.on_authorize_peer);
+
+        server = new DBusServer.sync(address, DBusServerFlags.NONE, DBus.generate_guid(), observer, 
cancellable);
+        server.new_connection.connect(on_new_connection);
+        server.start();
+
+        return true;
+    }
+
+    public async G get_remote() throws Error {
+        if (remote == null) {
+            yield launch_helper();
+        } else {
+            Idle.add(() => { get_remote.callback(); return false; });
+            yield;
+        }
+
+        return remote;
+    }
+
+    private bool on_authorize_peer(DBusAuthObserver observer, IOStream stream, Credentials? credentials) {
+        debug("Observer trying to authorize for %s", credentials.to_string());
+
+        if (credentials == null) {
+            return false;
+        }
+
+        try {
+            if (!credentials.is_same_user(new Credentials())) {
+                return false;
+            }
+
+            return true;
+        } catch (Error error) {
+            return false;
+        }
+    }
+
+    private bool on_new_connection(DBusServer server, DBusConnection connection) {
+        bool retval = true;
+        try {
+            remote = connection.get_proxy_sync(null, dbus_path, DBusProxyFlags.DO_NOT_LOAD_PROPERTIES |
+                                               DBusProxyFlags.DO_NOT_CONNECT_SIGNALS,
+                                               null);
+        } catch (Error error) {
+            critical("Failed to create DBus proxy: %s", error.message);
+            retval = false;
+        }
+
+        saved_get_remote_callback();
+
+        return retval;
+    }
+
+    private async void launch_helper() throws Error {
+        saved_get_remote_callback = launch_helper.callback;
+
+        if (remote_process == null) {
+            remote_process = new Subprocess(SubprocessFlags.NONE, remote_helper_path, "--address=" + 
server.get_client_address());
+            remote_process.wait_async.begin(null, on_process_exited);
+        }
+
+        yield;
+    }
+
+    private void on_process_exited(Object? source, AsyncResult res) {
+        try {
+            remote_process.wait_async.end(res);
+            remote_process = null;
+        } catch (Error error) { }
+
+        critical("Subprocess exited unexpectedly");
+    }
+}
diff --git a/src/meson.build b/src/meson.build
index 83b2a3b1..9709607f 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -267,7 +267,8 @@ executable(
         'video-support/VideoImportParams.vala',
         'video-support/Video.vala',
         'video-support/VideoSourceCollection.vala',
-        'video-support/VideoMetadata.vala'
+        'video-support/VideoMetadata.vala',
+        'ExternalHelper.vala'
     ] + shotwell_resources + face_sources,
     include_directories : vapi_incdir,
     dependencies : [