//! `loopd`: the agent loop daemon. It has two commands: `selftest`, which runs the startup checks
//! before serving anyone, and `serve`, which runs those checks and then runs the channel server.

use std::os::unix::fs::PermissionsExt;
use std::os::unix::net::UnixListener;
use std::path::Path;
use std::process::ExitCode;
use std::sync::Arc;
use std::time::Duration;

use loopd::broker_port::{BrokerPort, NoBroker, not_configured_line};
use loopd::channel::{self, Context};
use loopd::config::Config;
use loopd::llama::Client;
use loopd::selftest::{SelfTestError, run};
use loopd::tools::{Registry, ToolPort};

fn main() -> ExitCode {
    // `args_os`: the config path need not be UTF-8, and `args` would panic on one that is not.
    let args: Vec<std::ffi::OsString> = std::env::args_os().skip(1).collect();
    let words: Vec<Option<&str>> = args.iter().map(|a| a.to_str()).collect();
    match (words.as_slice(), args.get(2)) {
        ([Some("selftest"), Some("--config"), _], Some(path)) => run_selftest(Path::new(path)),
        ([Some("serve"), Some("--config"), _], Some(path)) => run_serve(Path::new(path)),
        _ => {
            eprintln!("usage: loopd selftest --config <path>");
            eprintln!("usage: loopd serve --config <path>");
            ExitCode::from(2)
        }
    }
}

/// The startup checks, with the lines `loopd` prints. Shared by `selftest` and `serve`.
fn run_selftest_check(client: &Client) -> Result<(), SelfTestError> {
    let mut on_step = |step: &str| {
        eprintln!("selftest: {step}");
    };
    match run(client, &mut on_step) {
        Ok(()) => {
            eprintln!("selftest: ok");
            Ok(())
        }
        Err(e) => {
            eprintln!("selftest: FAILED: {e}; see docs/runbook.md#loopd-selftest-failed");
            Err(e)
        }
    }
}

fn run_selftest(path: &Path) -> ExitCode {
    let cfg = match Config::load(path) {
        Ok(cfg) => cfg,
        Err(e) => {
            eprintln!("loopd: {e}");
            return ExitCode::from(1);
        }
    };

    let client = Client::new(cfg);
    match run_selftest_check(&client) {
        Ok(()) => ExitCode::SUCCESS,
        Err(_) => ExitCode::from(1),
    }
}

fn run_serve(path: &Path) -> ExitCode {
    let cfg = match Config::load(path) {
        Ok(cfg) => cfg,
        Err(e) => {
            eprintln!("loopd: {e}");
            return ExitCode::from(1);
        }
    };

    let socket = cfg.channel_socket();
    if socket.exists()
        && let Err(e) = std::fs::remove_file(&socket)
    {
        eprintln!(
            "loopd: cannot remove the old socket at {}: {e}",
            socket.display()
        );
        return ExitCode::from(1);
    }

    let client = Client::new(cfg.clone());
    if run_selftest_check(&client).is_err() {
        return ExitCode::from(1);
    }

    if let Some(parent) = socket.parent()
        && let Err(e) = std::fs::create_dir_all(parent)
    {
        eprintln!("loopd: cannot create the socket directory: {e}");
        return ExitCode::from(1);
    }
    let listener = match UnixListener::bind(&socket) {
        Ok(listener) => listener,
        Err(e) => {
            eprintln!("loopd: cannot bind the socket at {}: {e}", socket.display());
            return ExitCode::from(1);
        }
    };
    if let Err(e) = std::fs::set_permissions(&socket, std::fs::Permissions::from_mode(0o600)) {
        eprintln!("loopd: cannot set the mode of {}: {e}", socket.display());
        return ExitCode::from(1);
    }
    eprintln!("loopd: serving on {}", socket.display());

    let port: Box<dyn ToolPort> = match &cfg.broker.socket {
        Some(socket) => Box::new(BrokerPort::new(
            socket.clone(),
            Duration::from_millis(cfg.broker.timeout_ms),
        )),
        None => {
            eprintln!("{}", not_configured_line());
            Box::new(NoBroker)
        }
    };
    let ctx = Arc::new(Context::new(cfg, client, port, Registry::m3a()));
    if let Err(e) = channel::serve(listener, ctx) {
        eprintln!("loopd: the channel server stopped: {e}");
        return ExitCode::from(1);
    }
    ExitCode::SUCCESS
}