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

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

use clap::{Parser, Subcommand};

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

const AFTER_HELP: &str = "\
status exit codes: 0 connected, 1 disconnected, 2 dongle missing/error

example:
  mmx150d daemon \\
    --on-connect 'wpctl set-default <mmx150-sink-id>' \\
    --on-disconnect 'wpctl set-default <speakers-sink-id>'

find sink ids with: wpctl status";

#[derive(Parser, Debug)]
#[command(
    name = "mmx150d",
    version,
    about = "Connection monitoring for the beyerdynamic MMX 150 wireless dongle",
    after_help = AFTER_HELP
)]
struct Cli {
    #[command(subcommand)]
    command: Command,
}

#[derive(Subcommand, Debug)]
enum Command {
    /// Print the current headset link state
    Status,
    /// Run hooks when the headset connects or disconnects
    Daemon {
        /// Run CMD (via sh -c) when the headset connects
        #[arg(long)]
        on_connect: Option<String>,
        /// Run CMD (via sh -c) when the headset disconnects
        #[arg(long)]
        on_disconnect: Option<String>,
        /// Poll interval in seconds
        #[arg(long, default_value_t = 2, value_parser = clap::value_parser!(u64).range(1..))]
        interval: u64,
        /// Do not fire a hook for the state found at startup
        #[arg(long)]
        no_initial: bool,
    },
}

fn main() -> ExitCode {
    let cli = Cli::parse();
    match cli.command {
        Command::Status => cmd_status(),
        Command::Daemon {
            on_connect,
            on_disconnect,
            interval,
            no_initial,
        } => cmd_daemon(
            on_connect.as_deref(),
            on_disconnect.as_deref(),
            interval,
            no_initial,
        ),
    }
}

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(
    on_connect: Option<&str>,
    on_disconnect: Option<&str>,
    interval_secs: u64,
    no_initial: bool,
) -> ExitCode {
    let interval = Duration::from_secs(interval_secs);

    let mut hid: Option<Hidraw> = None;
    let mut tracker = StateTracker::new(!no_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) = on_connect {
                    spawn_hook(cmd, &mut children);
                }
            }
            Some(Transition::ToDisconnected { initial }) => {
                log_state("disconnected", initial);
                if let Some(cmd) = on_disconnect {
                    spawn_hook(cmd, &mut children);
                }
            }
            None => {}
        }

        let elapsed = cycle.elapsed();
        if let Some(remaining) = interval.checked_sub(elapsed) {
            std::thread::sleep(remaining);
        }
    }
}

/// 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 std::process::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_or(0, |d| d.as_secs())
}

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

    #[test]
    fn daemon_args_defaults() {
        let cli = Cli::try_parse_from(["mmx150d", "daemon"]).unwrap();
        let Command::Daemon {
            on_connect,
            on_disconnect,
            interval,
            no_initial,
        } = cli.command
        else {
            panic!("expected daemon subcommand");
        };
        assert_eq!(interval, 2);
        assert!(!no_initial);
        assert_eq!(on_connect, None);
        assert_eq!(on_disconnect, None);
    }

    #[test]
    fn daemon_args_full_parse() {
        let cli = Cli::try_parse_from([
            "mmx150d",
            "daemon",
            "--on-connect",
            "echo up",
            "--on-disconnect",
            "echo down",
            "--interval",
            "5",
            "--no-initial",
        ])
        .unwrap();
        let Command::Daemon {
            on_connect,
            on_disconnect,
            interval,
            no_initial,
        } = cli.command
        else {
            panic!("expected daemon subcommand");
        };
        assert_eq!(on_connect.as_deref(), Some("echo up"));
        assert_eq!(on_disconnect.as_deref(), Some("echo down"));
        assert_eq!(interval, 5);
        assert!(no_initial);
    }

    #[test]
    fn daemon_args_rejects_bad_interval() {
        assert!(Cli::try_parse_from(["mmx150d", "daemon", "--interval", "0"]).is_err());
        assert!(Cli::try_parse_from(["mmx150d", "daemon", "--interval", "x"]).is_err());
        assert!(Cli::try_parse_from(["mmx150d", "daemon", "--interval", "1"]).is_ok());
    }

    #[test]
    fn daemon_args_rejects_unknown_option() {
        assert!(Cli::try_parse_from(["mmx150d", "daemon", "--wat"]).is_err());
    }

    #[test]
    fn status_subcommand_parses() {
        assert!(matches!(
            Cli::try_parse_from(["mmx150d", "status"]).unwrap().command,
            Command::Status
        ));
    }
}