//! `gatewayd serve --config <path>`: the Mattermost channel. It loads its configuration and its
//! token, prepares its directory, then serves until it must stop (exit 1).

use std::os::unix::fs::DirBuilderExt;
use std::path::Path;
use std::process::ExitCode;
use std::sync::Arc;
use std::sync::atomic::AtomicBool;

use bxcore::{instance, secrets};
use gatewayd::config::{Config, MATTERMOST_TOKEN};
use gatewayd::serve::{START_FAILED, Tuning, run};

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("serve"), Some("--config"), _], Some(path)) => serve(Path::new(path)),
        _ => {
            eprintln!("usage: gatewayd serve --config <path>");
            ExitCode::from(2)
        }
    }
}

fn serve(path: &Path) -> ExitCode {
    // Each failure prints its message with `eprintln!` and returns `ExitCode::from(1)`.
    // 1. `let config = match Config::load(path) { ... }`: an Err(e) prints
    //    "gatewayd: {e}\n{START_FAILED}".
    // 2. `let source = match config.token_source() { ... }`: an Err(why) prints
    //    "gatewayd: {}: {why}\n{START_FAILED}" with `path.display()`.
    // 3. `let env = |k: &str| std::env::var_os(k);`, then
    //    `let loaded = match secrets::load("gatewayd", MATTERMOST_TOKEN, &source, &env)`: an Err(e)
    //    prints "gatewayd: {e}" (the error carries its own pointer).
    //    Then `if let Some(warning) = &loaded.warning { eprintln!("{warning}"); }`.
    // 3b. The instance lock, `<home>/run/gatewayd.lock` (M5b spec, section 9a): after the secret,
    //    which is read before anything is made, and before the directory and the socket.
    // 4. The state file's directory:
    //    `let dir = config.state_path().parent().map(Path::to_path_buf).unwrap_or_default();`
    //    `std::fs::DirBuilder::new().recursive(true).mode(0o700).create(&dir)`: an Err(e) prints
    //    "gatewayd: cannot prepare {}: {e}\n{START_FAILED}" with `dir.display()`.
    // 5. `let log: gatewayd::serve::Log = Arc::new(|line: &str| eprintln!("{line}"));`
    //    `let stop = run(config, loaded.secret, Tuning::default(), log, &AtomicBool::new(false));`
    //    `eprintln!("{stop}");` and `ExitCode::from(1)`.
    let config = match Config::load(path) {
        Ok(config) => config,
        Err(e) => {
            eprintln!("gatewayd: {e}\n{START_FAILED}");
            return ExitCode::from(1);
        }
    };
    let source = match config.token_source() {
        Ok(source) => source,
        Err(why) => {
            eprintln!("gatewayd: {}: {why}\n{START_FAILED}", path.display());
            return ExitCode::from(1);
        }
    };
    let env = |k: &str| std::env::var_os(k);
    let loaded = match secrets::load("gatewayd", MATTERMOST_TOKEN, &source, &env) {
        Ok(loaded) => loaded,
        Err(e) => {
            eprintln!("gatewayd: {e}");
            return ExitCode::from(1);
        }
    };
    if let Some(warning) = &loaded.warning {
        eprintln!("{warning}");
    }
    let lock_path = config.paths.home.join("run/gatewayd.lock");
    let _instance = match instance::lock(&lock_path) {
        Ok(held) => held,
        Err(e) => {
            eprintln!("{}", e.line("gatewayd", &lock_path));
            return ExitCode::from(1);
        }
    };
    let dir = config
        .state_path()
        .parent()
        .map(Path::to_path_buf)
        .unwrap_or_default();
    if let Err(e) = std::fs::DirBuilder::new()
        .recursive(true)
        .mode(0o700)
        .create(&dir)
    {
        eprintln!(
            "gatewayd: cannot prepare {}: {e}\n{START_FAILED}",
            dir.display()
        );
        return ExitCode::from(1);
    }
    let log: gatewayd::serve::Log = Arc::new(|line: &str| eprintln!("{line}"));
    let stop = run(
        config,
        loaded.secret,
        Tuning::default(),
        log,
        &AtomicBool::new(false),
    );
    eprintln!("{stop}");
    ExitCode::from(1)
}