tailscale-mcp 1.2.2

//! The `tailscale-mcp` binary.
//!
//! Everything interesting lives in the library; this is the wiring. The one
//! rule it exists to enforce is that standard output belongs to the protocol:
//! logs, startup notes and warnings all go to standard error, because a stray
//! line on standard output ends the session for a stdio client.

use anyhow::Context as _;
use clap::Parser as _;
use rmcp::ServiceExt as _;
use rmcp::transport::stdio;
use tailscale_mcp::config::{Cli, Command, Config, HttpConfig};
use tailscale_mcp::server::{self, Backends, Startup};
use tailscale_mcp::subcommands;

#[tokio::main]
async fn main() -> anyhow::Result<std::process::ExitCode> {
    let cli = Cli::parse();
    let asked = cli.command.clone();
    // Before the configuration is resolved, because this is the one question
    // worth asking of a server that will not start: a bad variable should not
    // stop it saying what it is.
    if matches!(asked, Some(Command::Version)) {
        return Ok(subcommands::version().emit());
    }
    let config = Config::resolve(cli)?;
    init_tracing(&config.log_filter);

    // A question, rather than a session. None of these starts a server, and
    // only the diagnosis touches the network.
    if let Some(command) = asked {
        return Ok(match command {
            Command::Diagnose { json } => {
                subcommands::diagnose(&config, Backends::discover(&config), json).await
            }
            Command::Tools { json } => subcommands::tools(&config, json),
            Command::Version => subcommands::version(),
            Command::Setup { client } => subcommands::setup(client, &config),
            Command::Policy { action } => {
                subcommands::policy(&config, Backends::discover(&config), &action).await
            }
        }
        .emit());
    }

    let backends = Backends::discover(&config);
    let startup = server::build(&config, tailscale_mcp::tools::entries(), backends).await?;
    for note in &startup.notes {
        eprintln!("tailscale-mcp: {note}");
    }

    match &config.http {
        Some(http) => serve_http(http, startup).await,
        None => serve_stdio(startup).await,
    }?;
    Ok(std::process::ExitCode::SUCCESS)
}

/// One client on a pipe the operating system already decided who may open.
async fn serve_stdio(startup: Startup) -> anyhow::Result<()> {
    let service = startup
        .server
        .serve(stdio())
        .await
        .context("could not start the stdio transport")?;
    service
        .waiting()
        .await
        .context("the session ended abnormally")?;
    Ok(())
}

/// Anything that can reach the socket, which is why there are checks in front.
async fn serve_http(settings: &HttpConfig, startup: Startup) -> anyhow::Result<()> {
    let guard = tailscale_mcp::http::Guard::for_session(
        settings,
        &startup.server.context().identity.last_known(),
        startup.peers.clone(),
    );
    eprintln!(
        "tailscale-mcp: serving HTTP on {} at {}, health at {}",
        settings.bind,
        tailscale_mcp::http::MCP_PATH,
        tailscale_mcp::http::HEALTH_PATH
    );
    tailscale_mcp::http::serve(settings, guard, startup.server.clone())
        .await
        .with_context(|| format!("could not serve HTTP on {}", settings.bind))
}

/// Logging, on standard error and nowhere else.
fn init_tracing(filter: &str) {
    use tracing_subscriber::EnvFilter;

    let filter = EnvFilter::try_new(filter).unwrap_or_else(|_| EnvFilter::new("warn"));
    tracing_subscriber::fmt()
        .with_env_filter(filter)
        .with_writer(std::io::stderr)
        .with_ansi(false)
        .init();
}