Desktop: Add support for opening files through the already-running instance via a local socket (#4123)

* Desktop: Forward file-open args from a second launch to the running instance

Also adds socket infrastructure that can be used in the future to allow dispatching actions from another process

* Use socket instead of ipc terminologie

* Fix

* Fix

* Better pipe name on windows

desktop/src/socket.rs

@@ -0,0 +1,126 @@
+use interprocess::local_socket::{GenericFilePath, GenericNamespaced, ListenerNonblockingMode, ListenerOptions, Name, prelude::*};
+use std::io::{ErrorKind, Read, Write};
+use std::sync::mpsc;
+use std::thread;
+use std::time::Duration;
+
+use crate::consts::APP_SOCKET_FILE_NAME;
+use crate::event::{AppEvent, AppEventScheduler};
+
+// TODO: Needs to be integrated/replaced with the action system.
+// TODO: At that point this should just wrap the action, meaning all actions bindable by the user can also be accessed via the socket.
+#[derive(serde::Serialize, serde::Deserialize)]
+pub(crate) enum Message {
+	OpenFiles(Vec<std::path::PathBuf>),
+}
+
+fn handle_message(message: Message, app_event_scheduler: &AppEventScheduler) {
+	match message {
+		Message::OpenFiles(paths) => {
+			app_event_scheduler.schedule(AppEvent::OpenFiles(paths));
+		}
+	}
+}
+
+pub(crate) fn send(message: Message) -> std::io::Result<()> {
+	let data = ron::ser::to_string(&message).map_err(|error| std::io::Error::new(std::io::ErrorKind::InvalidData, error))?;
+	let mut connection = interprocess::local_socket::Stream::connect(socket_name())?;
+	connection.write_all(data.as_bytes())
+}
+
+pub(crate) struct SocketHandle {
+	thread: Option<thread::JoinHandle<()>>,
+	shutdown_sender: mpsc::Sender<()>,
+}
+impl Drop for SocketHandle {
+	fn drop(&mut self) {
+		let _ = self.shutdown_sender.send(());
+		let _ = self.thread.take().expect("SocketHandle can only be dropped once").join();
+	}
+}
+
+pub(crate) fn start(app_event_scheduler: AppEventScheduler) -> SocketHandle {
+	let (shutdown_sender, shutdown_receiver) = mpsc::channel();
+
+	let thread = thread::Builder::new()
+		.name("socket".to_string())
+		.spawn(move || run(app_event_scheduler, shutdown_receiver))
+		.expect("Failed to spawn socket thread");
+
+	SocketHandle {
+		shutdown_sender,
+		thread: Some(thread),
+	}
+}
+
+fn run(app_event_scheduler: AppEventScheduler, shutdown_receiver: mpsc::Receiver<()>) {
+	let listener = match ListenerOptions::new()
+		.name(socket_name())
+		.nonblocking(ListenerNonblockingMode::Accept)
+		.try_overwrite(true)
+		.max_spin_time(Duration::from_millis(100))
+		.create_sync()
+	{
+		Ok(listener) => listener,
+		Err(error) => {
+			tracing::error!("Failed to bind socket: {}", error);
+			return;
+		}
+	};
+
+	let max_backoff = Duration::from_millis(100);
+	let mut backoff = Duration::ZERO;
+
+	loop {
+		if backoff.is_zero() {
+			match shutdown_receiver.try_recv() {
+				Ok(()) | Err(mpsc::TryRecvError::Disconnected) => break,
+				Err(mpsc::TryRecvError::Empty) => {}
+			}
+			backoff = Duration::from_nanos(1);
+		} else {
+			match shutdown_receiver.recv_timeout(backoff) {
+				Ok(()) | Err(mpsc::RecvTimeoutError::Disconnected) => break,
+				Err(mpsc::RecvTimeoutError::Timeout) => {}
+			}
+			backoff = (backoff * 2).min(max_backoff);
+		}
+
+		match listener.accept() {
+			Ok(mut connection) => {
+				backoff = Duration::ZERO;
+
+				let app_event_scheduler = app_event_scheduler.clone();
+				let spawn_result = thread::Builder::new().name("socket-connection".to_string()).spawn(move || {
+					let mut data = String::new();
+					if let Err(error) = connection.read_to_string(&mut data) {
+						tracing::error!("Failed to read socket message: {}", error);
+						return;
+					}
+
+					match ron::de::from_str(&data) {
+						Ok(message) => handle_message(message, &app_event_scheduler),
+						Err(error) => tracing::error!("Failed to deserialize socket message: {}", error),
+					}
+				});
+				if let Err(error) = spawn_result {
+					tracing::error!("Failed to spawn socket connection thread: {}", error);
+				}
+			}
+			Err(error) if matches!(error.kind(), ErrorKind::WouldBlock | ErrorKind::Interrupted) => {}
+			Err(error) => {
+				tracing::error!("Failed to accept socket connection: {}", error);
+			}
+		}
+	}
+}
+
+fn socket_name() -> Name<'static> {
+	if cfg!(target_os = "windows") {
+		let user = std::env::var("USERNAME").unwrap_or_default();
+		let name = format!("{user}-{app}-{APP_SOCKET_FILE_NAME}", app = crate::consts::APP_NAME);
+		name.to_ns_name::<GenericNamespaced>().expect("valid named pipe name")
+	} else {
+		crate::dirs::app_data_dir().join(APP_SOCKET_FILE_NAME).to_fs_name::<GenericFilePath>().expect("valid socket path")
+	}
+}