Added automatically starting server with local socket communication

Cargo.toml

@@ -8,4 +8,5 @@ edition = "2021"
 [dependencies]
 argh = "0.1.12"
 crossterm = "0.27.0"
+interprocess = "1.2.1"
 ratatui = "0.23.0"

src/client.rs

@@ -1,24 +1,16 @@
 use argh::FromArgs;
 use std::{error::Error, time::Duration};
 
+use crate::CliArgs;
+
 pub mod app;
 pub mod crossterm;
 pub mod ui;
 
-/// Demo
-#[derive(Debug, FromArgs)]
-struct Cli {
-    /// time in ms between two ticks.
-    #[argh(option, default = "250")]
-    tick_rate: u64,
-    /// whether unicode symbols are used to improve the overall look of the app
-    #[argh(option, default = "true")]
-    enhanced_graphics: bool,
-}
-
-pub fn run() -> Result<(), Box<dyn Error>> {
-    let cli: Cli = argh::from_env();
-    let tick_rate = Duration::from_millis(cli.tick_rate);
-    crossterm::run(tick_rate, cli.enhanced_graphics)?;
+pub fn run(args: CliArgs) -> Result<(), Box<dyn Error>> {
+    crossterm::run(
+        Duration::from_millis(args.tick_rate),
+        args.enhanced_graphics,
+    )?;
     Ok(())
 }

src/main.rs

@@ -1,4 +1,47 @@
+use argh::FromArgs;
+
 pub mod client;
 pub mod server;
 
-fn main() {}
+/// rmp: Rust Music Player
+#[derive(Debug, FromArgs)]
+pub struct CliArgs {
+    /// run the server
+    #[argh(switch, short = 's')]
+    server: bool,
+
+    /// kill server
+    #[argh(switch, short = 'x')]
+    exit: bool,
+
+    /// don't start server even if it's not running
+    #[argh(switch, short = 'c')]
+    client_only: bool,
+
+    /// time in ms between two ticks.
+    #[argh(option, default = "250")]
+    tick_rate: u64,
+
+    /// whether unicode symbols are used to improve the overall look of the app
+    #[argh(option, default = "true")]
+    enhanced_graphics: bool,
+}
+
+fn main() {
+    let args: CliArgs = argh::from_env();
+
+    if args.exit {
+        server::kill();
+        return;
+    }
+
+    if args.server {
+        server::run(args).unwrap();
+        return;
+    }
+
+    if !args.client_only && !server::is_running().unwrap() {
+        server::run_in_background();
+    }
+    client::run(args).map(|_| server::kill()).unwrap();
+}

src/server.rs

@@ -1,5 +1,203 @@
+use interprocess::local_socket::LocalSocketListener;
+use std::{fmt::Debug, fs, path::PathBuf, process};
+
+use crate::CliArgs;
+
 pub mod audio_backend;
 
-pub fn run() -> Result<(), ()> {
+#[derive(Debug)]
+pub enum ServerError {
+    Other(String),
+    Io(std::io::Error),
+    AlreadyStarted,
+    MissingRuntimeDir(PathBuf),
+}
+
+impl ServerError {
+    fn from_debuggable(err: impl Debug) -> Self {
+        Self::Other(format!("Unexpected error: {err:?}").to_string())
+    }
+}
+
+pub struct Server {
+    pub socket: LocalSocketListener,
+}
+
+impl Server {
+    pub fn new(socket_path: PathBuf) -> Result<Self, ServerError> {
+        Ok(Self {
+            socket: LocalSocketListener::bind(socket_path).map_err(|err| ServerError::Io(err))?,
+        })
+    }
+}
+
+pub fn run(args: CliArgs) -> Result<(), ServerError> {
+    if let Err(err) = os::reserve_pid() {
+        let exit_code = handle_error(err);
+        process::exit(exit_code);
+    }
+    serve()
+}
+
+pub fn kill() {
+    if let Err(err) = os::kill() {
+        let exit_code = handle_error(err);
+        process::exit(exit_code);
+    }
+}
+
+pub fn is_running() -> Result<bool, ServerError> {
+    match os::is_running() {
+        Ok(is_running) => Ok(is_running),
+        Err(err) => {
+            let exit_code = handle_error(err);
+            process::exit(exit_code);
+        }
+    }
+}
+
+pub fn run_in_background() {
+    if let Err(err) = os::run_in_background() {
+        let exit_code = handle_error(err);
+        process::exit(exit_code);
+    }
+}
+
+fn serve() -> Result<(), ServerError> {
+    let socket_path = os::get_socket_path()?;
+    if socket_path.exists() {
+        fs::remove_file(&socket_path).map_err(|err| ServerError::Io(err))?;
+    }
+    let server = Server::new(socket_path)?;
+    println!("Waiting for messages...");
+    for message in server.socket.incoming() {
+        match message {
+            Ok(stream) => {
+                println!("\tstream: {:?}", stream);
+            }
+            Err(err) => {
+                let exit_code = handle_error(ServerError::Io(err));
+                process::exit(exit_code);
+            }
+        }
+    }
+    println!("Reached the end of an infinite loop?");
     Ok(())
 }
+
+fn handle_error(err: ServerError) -> i32 {
+    match &err {
+        ServerError::Other(msg) => {
+            eprintln!("Unknown error: {msg}");
+            1
+        }
+        ServerError::Io(err) => {
+            eprintln!("IO error: {err}");
+            2
+        }
+        ServerError::AlreadyStarted => {
+            eprintln!("Server already running");
+            100
+        }
+        ServerError::MissingRuntimeDir(path) => {
+            eprintln!("Missing runtime directory: {}", path.to_string_lossy());
+            101
+        }
+    }
+}
+
+#[cfg(target_family = "unix")]
+mod os {
+    use std::{
+        fs,
+        path::{Path, PathBuf},
+        process::{id, Command, Stdio},
+    };
+
+    use super::ServerError;
+
+    pub fn reserve_pid() -> Result<(), ServerError> {
+        let pid_path = get_pid_path()?;
+        is_running()?;
+
+        fs::write(&pid_path, id().to_string()).map_err(|err| ServerError::Io(err))?;
+        Command::new("chmod")
+            .args(&["600", &pid_path.to_string_lossy()])
+            .output()
+            .map_err(|err| ServerError::Io(err))?;
+        Ok(())
+    }
+
+    pub fn is_running() -> Result<bool, ServerError> {
+        let pid_path = get_pid_path()?;
+
+        match fs::read(&pid_path) {
+            Ok(old_pid) => {
+                let old_pid =
+                    String::from_utf8(old_pid).map_err(|err| ServerError::from_debuggable(err))?;
+                let old_pid = old_pid.trim();
+                Ok(Command::new("ps")
+                    .args(&["-p", old_pid])
+                    .stdout(Stdio::null())
+                    .stderr(Stdio::null())
+                    .status()
+                    .map_err(|err| ServerError::Io(err))?
+                    .success())
+            }
+            _ => Ok(false),
+        }
+    }
+
+    pub fn run_in_background() -> Result<(), ServerError> {
+        let this = std::env::args().next().unwrap();
+        Command::new(this)
+            .stdout(Stdio::null())
+            .stderr(Stdio::null())
+            .args(&["-s"])
+            .spawn()
+            .map_err(|err| ServerError::Io(err))?;
+        Ok(())
+    }
+
+    pub fn kill() -> Result<(), ServerError> {
+        let pid_path = get_pid_path()?;
+        let socket_path = get_socket_path()?;
+        let pid = String::from_utf8(fs::read(&pid_path).map_err(|err| ServerError::Io(err))?)
+            .map_err(|err| ServerError::from_debuggable(err))?;
+        let pid = pid.trim();
+        Command::new("kill")
+            .arg(pid)
+            .spawn()
+            .map_err(|err| ServerError::Io(err))?;
+        Command::new("rm")
+            .args(&[
+                "-f",
+                &pid_path.to_string_lossy(),
+                &socket_path.to_string_lossy(),
+            ])
+            .spawn()
+            .map_err(|err| ServerError::Io(err))?;
+        Ok(())
+    }
+
+    pub fn get_socket_path() -> Result<PathBuf, ServerError> {
+        Ok(get_runtime_dir()?.join("rmp.socket"))
+    }
+
+    fn get_runtime_dir() -> Result<PathBuf, ServerError> {
+        let uid = String::from_utf8(
+            Command::new("id")
+                .arg("-u")
+                .output()
+                .map_err(|err| ServerError::Io(err))?
+                .stdout,
+        )
+        .map_err(|err| ServerError::from_debuggable(err))?;
+        let dir = Path::new("/run/user").join(uid.trim().to_string());
+        Ok(dir)
+    }
+
+    fn get_pid_path() -> Result<PathBuf, ServerError> {
+        Ok(get_runtime_dir()?.join("rmp.pid"))
+    }
+}