//! mmx150d — connection monitoring for the beyerdynamic MMX 150 wireless
//! dongle.

use std::process::{Child, Command, ExitCode, Stdio};
use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};

use mmx150::hid::{find_mmx150, Hidraw};
use mmx150::protocol::{self, LinkState, StateTracker, Transition};

fn main() -> ExitCode {
    let args: Vec<String> = std::env::args().skip(1).collect();
    match args.first().map(String::as_str) {
        Some("status") => cmd_status(),
        Some("daemon") => cmd_daemon(&args[1..]),
        _ => {
            print_usage();
            ExitCode::FAILURE
        }
    }
}

fn print_usage() {
    eprintln!(
        "usage: mmx150d <status|daemon>\n\
         \n\
         daemon options:\n\
         \x20 --on-connect CMD     run CMD (via sh -c) when the headset connects\n\
         \x20 --on-disconnect CMD  run CMD (via sh -c) when the headset disconnects\n\
         \x20 --interval SECS      poll interval (default: 2)\n\
         \x20 --no-initial         do not fire a hook for the state found at startup\n\
         \n\
         status exit codes: 0 connected, 1 disconnected, 2 dongle missing/error\n\
         \n\
         example:\n\
         \x20 mmx150d daemon \\\n\
         \x20   --on-connect 'wpctl set-default <mmx150-sink-id>' \\\n\
         \x20   --on-disconnect 'wpctl set-default <speakers-sink-id>'\n\
         \n\
         find sink ids with: wpctl status"
    );
}

fn cmd_status() -> ExitCode {
    let Some(dev) = find_mmx150().unwrap_or(None) else {
        eprintln!("dongle not found");
        return ExitCode::from(2);
    };
    let mut hid = match Hidraw::open(&dev.devnode) {
        Ok(h) => h,
        Err(e) => {
            eprintln!("error: {e}");
            return ExitCode::from(2);
        }
    };
    match protocol::link_status(&mut hid) {
        Ok(LinkState::Connected) => {
            println!("connected");
            ExitCode::SUCCESS
        }
        Ok(LinkState::Disconnected) => {
            println!("disconnected");
            ExitCode::from(1)
        }
        Err(e) => {
            eprintln!("error: {e}");
            ExitCode::from(2)
        }
    }
}
fn cmd_daemon(args: &[String]) -> ExitCode {
    let opts = match DaemonArgs::parse(args) {
        Ok(o) => o,
        Err(e) => {
            eprintln!("{e}");
            return ExitCode::FAILURE;
        }
    };

    let mut hid: Option<Hidraw> = None;
    let mut tracker = StateTracker::new(opts.fire_initial);
    let mut children: Vec<Child> = Vec::new();

    loop {
        let cycle = Instant::now();
        reap_children(&mut children);

        let link_up = poll(&mut hid);
        match tracker.update(link_up) {
            Some(Transition::ToConnected { initial }) => {
                log_state("connected", initial);
                if let Some(cmd) = &opts.on_connect {
                    spawn_hook(cmd, &mut children);
                }
            }
            Some(Transition::ToDisconnected { initial }) => {
                log_state("disconnected", initial);
                if let Some(cmd) = &opts.on_disconnect {
                    spawn_hook(cmd, &mut children);
                }
            }
            None => {}
        }

        let elapsed = cycle.elapsed();
        if elapsed < opts.interval {
            std::thread::sleep(opts.interval - elapsed);
        }
    }
}

/// One poll cycle: (re)open the dongle if needed, then query the link.
/// Returns `true` if the headset answered.
fn poll(hid: &mut Option<Hidraw>) -> bool {
    if hid.is_none() {
        match find_mmx150() {
            Ok(Some(dev)) => match Hidraw::open(&dev.devnode) {
                Ok(h) => *hid = Some(h),
                Err(_) => return false,
            },
            _ => return false,
        }
    }
    let Some(h) = hid.as_mut() else {
        return false;
    };
    match protocol::link_status(h) {
        Ok(LinkState::Connected) => true,
        Ok(LinkState::Disconnected) => false,
        Err(_) => {
            *hid = None;
            false
        }
    }
}

fn spawn_hook(cmd: &str, children: &mut Vec<Child>) {
    match Command::new("sh")
        .arg("-c")
        .arg(cmd)
        .stdin(Stdio::null())
        .stdout(Stdio::null())
        .stderr(Stdio::null())
        .spawn()
    {
        Ok(child) => children.push(child),
        Err(e) => eprintln!("[{}] hook spawn failed: {e}", timestamp()),
    }
}

/// Reap finished hook processes so they don't linger as zombies.
fn reap_children(children: &mut Vec<Child>) {
    children.retain_mut(|c| c.try_wait().map_or(true, |s| s.is_none()));
}

fn log_state(state: &str, initial: bool) {
    println!(
        "[{}] headset {}{}",
        timestamp(),
        state,
        if initial { " (initial)" } else { "" }
    );
}

fn timestamp() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0)
}

/// Parsed `mmx150 daemon` command line.
#[derive(Debug, PartialEq)]
struct DaemonArgs {
    on_connect: Option<String>,
    on_disconnect: Option<String>,
    interval: Duration,
    fire_initial: bool,
}

impl DaemonArgs {
    fn parse(args: &[String]) -> Result<DaemonArgs, String> {
        let mut on_connect = None;
        let mut on_disconnect = None;
        let mut interval = Duration::from_secs(2);
        let mut fire_initial = true;

        let mut it = args.iter();
        while let Some(arg) = it.next() {
            match arg.as_str() {
                "--on-connect" => {
                    on_connect = Some(it.next().ok_or("--on-connect needs an argument")?.clone())
                }
                "--on-disconnect" => {
                    on_disconnect = Some(
                        it.next()
                            .ok_or("--on-disconnect needs an argument")?
                            .clone(),
                    )
                }
                "--interval" => {
                    let secs = it
                        .next()
                        .and_then(|s| s.parse::<u64>().ok())
                        .filter(|&s| s > 0)
                        .ok_or("--interval needs a number of seconds > 0")?;
                    interval = Duration::from_secs(secs);
                }
                "--no-initial" => fire_initial = false,
                other => return Err(format!("unknown option: {other}")),
            }
        }
        Ok(DaemonArgs {
            on_connect,
            on_disconnect,
            interval,
            fire_initial,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn args(list: &[&str]) -> Vec<String> {
        list.iter().map(|s| s.to_string()).collect()
    }

    #[test]
    fn daemon_args_defaults() {
        let a = DaemonArgs::parse(&args(&[])).unwrap();
        assert_eq!(a.interval, Duration::from_secs(2));
        assert!(a.fire_initial);
        assert_eq!(a.on_connect, None);
        assert_eq!(a.on_disconnect, None);
    }

    #[test]
    fn daemon_args_full_parse() {
        let a = DaemonArgs::parse(&args(&[
            "--on-connect",
            "echo up",
            "--on-disconnect",
            "echo down",
            "--interval",
            "5",
            "--no-initial",
        ]))
        .unwrap();
        assert_eq!(a.on_connect.as_deref(), Some("echo up"));
        assert_eq!(a.on_disconnect.as_deref(), Some("echo down"));
        assert_eq!(a.interval, Duration::from_secs(5));
        assert!(!a.fire_initial);
    }

    #[test]
    fn daemon_args_rejects_missing_option_argument() {
        assert!(DaemonArgs::parse(&args(&["--on-connect"])).is_err());
        assert!(DaemonArgs::parse(&args(&["--on-disconnect"])).is_err());
        assert!(DaemonArgs::parse(&args(&["--interval"])).is_err());
    }

    #[test]
    fn daemon_args_rejects_bad_interval() {
        assert!(DaemonArgs::parse(&args(&["--interval", "0"])).is_err());
        assert!(DaemonArgs::parse(&args(&["--interval", "x"])).is_err());
    }

    #[test]
    fn daemon_args_rejects_unknown_option() {
        assert!(DaemonArgs::parse(&args(&["--wat"])).is_err());
    }
}