//! varde-daemon: content-addressed blob mirror daemon.

use std::path::PathBuf;

use anyhow::{bail, Context, Result};
use tracing::info;

use varde_daemon::config::{Config, Mode, Overrides};
use varde_daemon::{daemon, server};

const USAGE: &str = "\
varde-daemon — content-addressed blob mirror daemon

USAGE:
    varde-daemon [OPTIONS]

OPTIONS:
    --config <PATH>    Config file (default: /etc/varde/config.toml or
                       $XDG_CONFIG_HOME/varde/config.toml)
    --store <PATH>     Store directory override
    --socket <PATH>    API socket path override
    --system           Force system-mode default paths
    --user             Force user-mode default paths
    --version          Print version and exit
    --help             Print this help and exit
";

// The spec reserves clap for varde-ctl; the daemon takes five flags, which
// a hand parse covers without the dependency.
fn parse_args() -> Result<(Mode, Overrides)> {
    let mut overrides = Overrides::default();
    let mut mode = Mode::detect();
    let mut args = std::env::args().skip(1);
    while let Some(arg) = args.next() {
        let mut value = |name: &str| -> Result<PathBuf> {
            args.next()
                .map(PathBuf::from)
                .with_context(|| format!("{name} requires a value"))
        };
        match arg.as_str() {
            "--config" => overrides.config_path = Some(value("--config")?),
            "--store" => overrides.store_dir = Some(value("--store")?),
            "--socket" => overrides.socket_path = Some(value("--socket")?),
            "--system" => mode = Mode::System,
            "--user" => mode = Mode::User,
            "--version" => {
                println!("varde-daemon {}", env!("CARGO_PKG_VERSION"));
                std::process::exit(0);
            }
            "--help" | "-h" => {
                print!("{USAGE}");
                std::process::exit(0);
            }
            other => bail!("unknown argument {other:?}\n\n{USAGE}"),
        }
    }
    Ok((mode, overrides))
}

fn main() -> Result<()> {
    tracing_subscriber::fmt()
        .with_env_filter(
            tracing_subscriber::EnvFilter::try_from_default_env()
                .unwrap_or_else(|_| "varde_daemon=info".into()),
        )
        .init();

    let (mode, overrides) = parse_args()?;
    let config = Config::load(mode, &overrides)?;
    info!(store = %config.store_dir.display(), socket = %config.socket_path.display(), "starting");

    std::fs::create_dir_all(&config.store_dir)
        .with_context(|| format!("creating store directory {}", config.store_dir.display()))?;

    tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()
        .context("building tokio runtime")?
        .block_on(run(config))
}

async fn run(config: Config) -> Result<()> {
    let socket_path = config.socket_path.clone();
    let daemon = daemon::Daemon::open(config).await?;
    // Prefer a systemd activation socket; bind ourselves otherwise so
    // non-systemd distros work identically.
    let (listener, activated) = match server::activation_listener()? {
        Some(listener) => (listener, true),
        None => (server::bind_socket(&socket_path)?, false),
    };
    server::notify_ready();

    let result = tokio::select! {
        r = server::serve(listener, daemon.clone()) => r,
        r = shutdown_signal() => r.map(|signal| info!(signal, "shutting down")),
    };

    // Close the endpoint and flush the store. The socket file is ours to
    // remove only when we bound it (systemd owns activation sockets).
    daemon.shutdown().await;
    if !activated {
        let _ = std::fs::remove_file(&socket_path);
    }
    result
}

async fn shutdown_signal() -> Result<&'static str> {
    use tokio::signal::unix::{signal, SignalKind};
    let mut term = signal(SignalKind::terminate()).context("installing SIGTERM handler")?;
    let mut int = signal(SignalKind::interrupt()).context("installing SIGINT handler")?;
    tokio::select! {
        _ = term.recv() => Ok("SIGTERM"),
        _ = int.recv() => Ok("SIGINT"),
    }
}