//! gen_server tests: call round-trip, cast, lifecycle callbacks, and the two
//! server-down detection paths (reply-channel close vs. inbox-send failure).

use smarm::gen_server::{start, CallError, GenServer, ServerBuilder};
use smarm::run;
use std::sync::{Arc, Mutex};

// ---------------------------------------------------------------------------
// A trivial counter server: casts mutate, calls read (or blow up).
// ---------------------------------------------------------------------------

struct Counter {
    n: i64,
}

enum Req {
    Get,
    Boom,
}

enum Op {
    Add(i64),
}

impl GenServer for Counter {
    type Call = Req;
    type Reply = i64;
    type Cast = Op;
    type Info = ();
    type Timer = ();

    fn handle_call(&mut self, req: Req) -> i64 {
        match req {
            Req::Get => self.n,
            Req::Boom => panic!("boom"),
        }
    }

    fn handle_cast(&mut self, op: Op) {
        match op {
            Op::Add(x) => self.n += x,
        }
    }
}

// Casts are applied in order and a later call observes the accumulated state.
#[test]
fn cast_then_call_roundtrip() {
    let got = Arc::new(Mutex::new(0i64));
    let got2 = got.clone();
    run(move || {
        let server = start(Counter { n: 0 });
        server.cast(Op::Add(5)).unwrap();
        server.cast(Op::Add(3)).unwrap();
        let n = server.call(Req::Get).unwrap();
        *got2.lock().unwrap() = n;
    });
    assert_eq!(*got.lock().unwrap(), 8);
}

// ---------------------------------------------------------------------------
// Lifecycle: init runs before the first message, terminate on graceful exit.
// ---------------------------------------------------------------------------

struct Lifecycle {
    log: Arc<Mutex<Vec<&'static str>>>,
}

impl GenServer for Lifecycle {
    type Call = ();
    type Reply = ();
    type Cast = ();
    type Info = ();
    type Timer = ();

    fn init(&mut self, _ctx: &smarm::gen_server::ServerCtx<Self>) {
        self.log.lock().unwrap().push("init");
    }

    fn handle_call(&mut self, _req: ()) {
        self.log.lock().unwrap().push("call");
    }

    fn handle_cast(&mut self, _req: ()) {}

    fn terminate(&mut self) {
        self.log.lock().unwrap().push("terminate");
    }
}

// init -> handle_call -> (drop last ref closes inbox) -> terminate.
#[test]
fn init_and_terminate_run() {
    let log = Arc::new(Mutex::new(Vec::new()));
    let log2 = log.clone();
    run(move || {
        let server = start(Lifecycle { log: log2 });
        server.call(()).unwrap();
        // Dropping the only ref closes the inbox; the server breaks out of its
        // recv loop and runs terminate. run() will not return until it has.
        drop(server);
    });
    assert_eq!(*log.lock().unwrap(), vec!["init", "call", "terminate"]);
}

// ---------------------------------------------------------------------------
// Server-down detection.
// ---------------------------------------------------------------------------

// The server dies *while* a call is in flight (handler panics): the reply
// sender drops on unwind, closing the reply channel, so the parked caller's
// recv returns Err -> ServerDown.
#[test]
fn call_to_panicking_handler_is_server_down() {
    let got = Arc::new(Mutex::new(None));
    let got2 = got.clone();
    run(move || {
        let server = start(Counter { n: 0 });
        let r = server.call(Req::Boom);
        *got2.lock().unwrap() = Some(r);
    });
    assert_eq!(*got.lock().unwrap(), Some(Err(CallError::ServerDown)));
}

// A call issued *after* the server is already gone: the inbox is closed, so the
// send itself fails -> ServerDown (the other detection path).
#[test]
fn call_after_server_gone_is_server_down() {
    let got = Arc::new(Mutex::new(None));
    let got2 = got.clone();
    run(move || {
        let server = start(Counter { n: 0 });
        let server2 = server.clone();
        // This kills the server (and is itself ServerDown).
        assert_eq!(server.call(Req::Boom), Err(CallError::ServerDown));
        // Inbox now closed; a fresh call can't even be enqueued.
        let r = server2.call(Req::Get);
        *got2.lock().unwrap() = Some(r);
    });
    assert_eq!(*got.lock().unwrap(), Some(Err(CallError::ServerDown)));
}

// ---------------------------------------------------------------------------
// call_timeout
// ---------------------------------------------------------------------------

use smarm::gen_server::CallTimeoutError;
use std::time::{Duration, Instant};

/// Replies after sleeping `delay_ms` (parking the server actor, not the OS
/// thread), so callers can race a deadline against the reply.
struct Slow;

impl GenServer for Slow {
    type Call = u64; // delay in ms
    type Reply = u64;
    type Cast = ();
    type Info = ();
    type Timer = ();

    fn handle_call(&mut self, delay_ms: u64) -> u64 {
        if delay_ms > 0 {
            smarm::sleep(Duration::from_millis(delay_ms));
        }
        delay_ms
    }

    fn handle_cast(&mut self, _: ()) {}
}

#[test]
fn call_timeout_returns_reply_within_deadline() {
    run(|| {
        let srv = start(Slow);
        assert_eq!(srv.call_timeout(0, Duration::from_secs(10)), Ok(0));
    });
}

#[test]
fn call_timeout_times_out_on_slow_handler() {
    run(|| {
        let srv = start(Slow);
        let start_t = Instant::now();
        let r = srv.call_timeout(500, Duration::from_millis(50));
        assert_eq!(r, Err(CallTimeoutError::Timeout));
        let elapsed = start_t.elapsed();
        // Gave up at the deadline, not at the reply.
        assert!(elapsed >= Duration::from_millis(50));
        assert!(elapsed < Duration::from_millis(500));
    });
}

#[test]
fn server_survives_an_abandoned_call_and_late_reply_is_discarded() {
    run(|| {
        let srv = start(Slow);
        assert_eq!(
            srv.call_timeout(100, Duration::from_millis(20)),
            Err(CallTimeoutError::Timeout)
        );
        // The timed-out request is still handled; its reply send fails
        // harmlessly (receiver dropped). The server must keep serving, and
        // the late reply must not leak into THIS call's reply channel.
        assert_eq!(srv.call_timeout(0, Duration::from_secs(10)), Ok(0));
        // Plain unbounded call still fine too.
        assert_eq!(srv.call(0), Ok(0));
    });
}

#[test]
fn call_timeout_to_dead_server_is_server_down_not_timeout() {
    struct Bomb;
    impl GenServer for Bomb {
        type Call = ();
        type Info = ();
        type Timer = ();
        type Reply = ();
        type Cast = ();
        fn handle_call(&mut self, _: ()) {
            panic!("kaboom");
        }
        fn handle_cast(&mut self, _: ()) {}
    }

    run(|| {
        let srv = start(Bomb);
        // Dies mid-call: reply channel closes -> ServerDown (even though the
        // generous deadline never fires).
        assert_eq!(
            srv.call_timeout((), Duration::from_secs(10)),
            Err(CallTimeoutError::ServerDown)
        );
        // Already gone: inbox send fails -> ServerDown.
        assert_eq!(
            srv.call_timeout((), Duration::from_secs(10)),
            Err(CallTimeoutError::ServerDown)
        );
    });
}

// ---------------------------------------------------------------------------
// handle_info: out-of-band channels selected alongside the inbox (v0.8)
// ---------------------------------------------------------------------------

/// Logs every message it handles, in order; a call reads the log back.
struct Logger {
    log: Vec<&'static str>,
}

impl GenServer for Logger {
    type Call = ();
    type Reply = Vec<&'static str>;
    type Cast = ();
    type Info = &'static str;
    type Timer = ();

    fn handle_call(&mut self, _: ()) -> Vec<&'static str> {
        self.log.clone()
    }

    fn handle_cast(&mut self, _: ()) {
        self.log.push("cast");
    }

    fn handle_info(&mut self, info: &'static str) {
        self.log.push(info);
    }
}

// An info message is dispatched to handle_info, interleaved with normal
// service.
#[test]
fn info_is_dispatched() {
    let got = Arc::new(Mutex::new(Vec::new()));
    let got2 = got.clone();
    run(move || {
        let (info_tx, info_rx) = smarm::channel::<&'static str>();
        let server = ServerBuilder::new(Logger { log: Vec::new() })
            .with_info(info_rx)
            .start();
        info_tx.send("info").unwrap();
        *got2.lock().unwrap() = server.call(()).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), vec!["info"]);
}

// Arm priority: with a cast AND an info both queued before the server first
// runs, the info is handled first — info arms outrank the inbox. Relies on
// run()'s deterministic single-thread ordering.
#[test]
fn info_outranks_inbox() {
    let got = Arc::new(Mutex::new(Vec::new()));
    let got2 = got.clone();
    run(move || {
        let (info_tx, info_rx) = smarm::channel::<&'static str>();
        let server = ServerBuilder::new(Logger { log: Vec::new() })
            .with_info(info_rx)
            .start();
        // The server actor hasn't run yet: both messages are queued before
        // its first select. Inbox first in *send* order, info first in *arm*
        // order — arm order must win.
        server.cast(()).unwrap();
        info_tx.send("info").unwrap();
        *got2.lock().unwrap() = server.call(()).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), vec!["info", "cast"]);
}

// Two info channels: declaration order is priority order.
#[test]
fn info_arms_keep_declaration_priority() {
    let got = Arc::new(Mutex::new(Vec::new()));
    let got2 = got.clone();
    run(move || {
        let (hi_tx, hi_rx) = smarm::channel::<&'static str>();
        let (lo_tx, lo_rx) = smarm::channel::<&'static str>();
        let server = ServerBuilder::new(Logger { log: Vec::new() })
            .with_info(hi_rx)
            .with_info(lo_rx)
            .start();
        // Sent low-priority first; handled high-priority first.
        lo_tx.send("lo").unwrap();
        hi_tx.send("hi").unwrap();
        *got2.lock().unwrap() = server.call(()).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), vec!["hi", "lo"]);
}

// A closed info arm is silently dropped and the server keeps serving; the
// closure does NOT reach handle_info and does NOT starve the inbox (the
// closed-arm-is-ready-forever gotcha).
#[test]
fn closed_info_arm_is_dropped_silently() {
    let got = Arc::new(Mutex::new(Vec::new()));
    let got2 = got.clone();
    run(move || {
        let (info_tx, info_rx) = smarm::channel::<&'static str>();
        let server = ServerBuilder::new(Logger { log: Vec::new() })
            .with_info(info_rx)
            .start();
        drop(info_tx); // closed before the server's first select
        server.cast(()).unwrap();
        *got2.lock().unwrap() = server.call(()).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), vec!["cast"]);
}

// ---------------------------------------------------------------------------
// handle_down: monitors handed to the loop via Watcher (v0.8)
// ---------------------------------------------------------------------------

use smarm::gen_server::Watcher;
use smarm::{monitor, spawn, DownReason, Pid};

/// The motivating pattern: a server that spawns workers from a handler,
/// watches them, and logs their deaths.
struct Pool {
    watcher: Option<Watcher<Self>>,
    log: Vec<DownReason>,
}

enum PoolCast {
    SpawnDoomedWorker,
    Watch(Pid),
}

impl GenServer for Pool {
    type Call = ();
    type Reply = Vec<DownReason>;
    type Cast = PoolCast;
    type Info = ();
    type Timer = ();

    fn init(&mut self, ctx: &smarm::gen_server::ServerCtx<Self>) {
        self.watcher = Some(ctx.watcher());
    }

    fn handle_call(&mut self, _: ()) -> Vec<DownReason> {
        self.log.clone()
    }

    fn handle_cast(&mut self, cast: PoolCast) {
        let watcher = self.watcher.as_ref().expect("init ran first");
        match cast {
            PoolCast::SpawnDoomedWorker => {
                let h = spawn(|| panic!("worker died"));
                watcher.watch(monitor(h.pid()));
            }
            PoolCast::Watch(pid) => watcher.watch(monitor(pid)),
        }
    }

    fn handle_down(&mut self, down: smarm::Down) {
        self.log.push(down.reason);
    }
}

// A worker spawned and watched from inside a handler delivers its Down to
// handle_down. Down arms outrank the inbox, so the death is in the log by
// the time the follow-up call is answered.
#[test]
fn worker_pool_down_reaches_handle_down() {
    let got = Arc::new(Mutex::new(Vec::new()));
    let got2 = got.clone();
    run(move || {
        let server = start(Pool { watcher: None, log: Vec::new() });
        server.cast(PoolCast::SpawnDoomedWorker).unwrap();
        let _ = server.call(()).unwrap(); // sync point: cast handled, worker live
        *got2.lock().unwrap() = server.call(()).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), vec![DownReason::Panic]);
}

// Watching an already-dead pid yields an immediate NoProc Down, and the down
// arm outranks the inbox: the call cast *after* the watch still observes it.
#[test]
fn watch_dead_pid_is_noproc_down() {
    let got = Arc::new(Mutex::new(Vec::new()));
    let got2 = got.clone();
    run(move || {
        let h = spawn(|| {});
        let dead = h.pid();
        h.join().unwrap();
        let server = start(Pool { watcher: None, log: Vec::new() });
        server.cast(PoolCast::Watch(dead)).unwrap();
        *got2.lock().unwrap() = server.call(()).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), vec![DownReason::NoProc]);
}

// A state that never clones the Watcher closes the control arm; the loop
// falls back to the plain-inbox park and keeps serving. (Every pre-v0.8 test
// in this file also exercises this path.)
#[test]
fn unused_ctx_closes_control_arm_silently() {
    let got = Arc::new(Mutex::new(0i64));
    let got2 = got.clone();
    run(move || {
        let server = start(Counter { n: 0 });
        server.cast(Op::Add(2)).unwrap();
        server.cast(Op::Add(40)).unwrap();
        *got2.lock().unwrap() = server.call(Req::Get).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), 42);
}

// ---------------------------------------------------------------------------
// RFC 015 — gen_server timers. A server that arms one-shot timers from a cast
// and records each fire's payload, plus the cancel race signal.
// ---------------------------------------------------------------------------
use smarm::gen_server::{ServerCtx, TimerHandle};
use smarm::TimerId;

enum TkCast {
    Arm(Duration),
    Tick(Duration),
    CancelLast,
}

struct Timed {
    timer: Option<TimerHandle<Self>>,
    fired: Arc<Mutex<Vec<u32>>>,
    cancel_won: Arc<Mutex<Option<bool>>>,
    last: Option<TimerId>,
}

impl GenServer for Timed {
    type Call = ();
    type Reply = usize; // count of fires so far (a sync read point)
    type Cast = TkCast;
    type Info = ();
    type Timer = u32;

    fn init(&mut self, ctx: &ServerCtx<Self>) {
        self.timer = Some(ctx.timer());
    }

    fn handle_call(&mut self, _: ()) -> usize {
        self.fired.lock().unwrap().len()
    }

    fn handle_cast(&mut self, c: TkCast) {
        let t = self.timer.as_ref().expect("init ran first");
        match c {
            TkCast::Arm(d) => self.last = Some(t.arm_after(d, 7)),
            TkCast::Tick(d) => self.last = Some(t.tick_every(d, 9)),
            TkCast::CancelLast => {
                let id = self.last.take().expect("a timer was armed");
                *self.cancel_won.lock().unwrap() = Some(t.cancel(id));
            }
        }
    }

    fn handle_timer(&mut self, msg: u32) {
        self.fired.lock().unwrap().push(msg);
    }
}

fn timed(fired: Arc<Mutex<Vec<u32>>>, cancel_won: Arc<Mutex<Option<bool>>>) -> Timed {
    Timed { timer: None, fired, cancel_won, last: None }
}

// A one-shot armed from a handler fires into handle_timer with its payload.
#[test]
fn arm_after_fires_into_handle_timer() {
    let fired = Arc::new(Mutex::new(Vec::new()));
    let f2 = fired.clone();
    run(move || {
        let cw = Arc::new(Mutex::new(None));
        let server = start(timed(f2, cw));
        server.cast(TkCast::Arm(Duration::from_millis(10))).unwrap();
        let _ = server.call(()).unwrap(); // sync: arm done
        smarm::sleep(Duration::from_millis(40)); // let the timer fire
        let count = server.call(()).unwrap(); // timer arm outranks this inbox call
        assert_eq!(count, 1, "the one-shot should have fired exactly once");
    });
    assert_eq!(*fired.lock().unwrap(), vec![7]);
}

// cancel before the deadline wins the race (returns true) and suppresses the
// fire entirely.
#[test]
fn cancel_before_fire_suppresses_it() {
    let fired = Arc::new(Mutex::new(Vec::new()));
    let cancel_won = Arc::new(Mutex::new(None));
    let f2 = fired.clone();
    let c2 = cancel_won.clone();
    run(move || {
        let server = start(timed(f2, c2));
        server.cast(TkCast::Arm(Duration::from_millis(50))).unwrap();
        server.cast(TkCast::CancelLast).unwrap();
        let _ = server.call(()).unwrap(); // sync: arm + cancel both handled
        smarm::sleep(Duration::from_millis(80)); // past the original deadline
        let count = server.call(()).unwrap();
        assert_eq!(count, 0, "cancelled timer must not fire");
    });
    assert_eq!(*cancel_won.lock().unwrap(), Some(true), "cancel beat the fire");
    assert!(fired.lock().unwrap().is_empty());
}

// tick_every re-arms: a periodic fires repeatedly off one arm, each tick
// carrying a fresh payload. (Timer fires outrank the inbox by arm position, so
// a periodic cannot be starved by userspace traffic — the same property the
// info_outranks_inbox test pins for infos.)
#[test]
fn tick_every_rearms_repeatedly() {
    let fired = Arc::new(Mutex::new(Vec::new()));
    let f2 = fired.clone();
    run(move || {
        let cw = Arc::new(Mutex::new(None));
        let server = start(timed(f2, cw));
        server.cast(TkCast::Tick(Duration::from_millis(20))).unwrap();
        let _ = server.call(()).unwrap(); // sync: periodic armed
        smarm::sleep(Duration::from_millis(130)); // ~6 periods
        let count = server.call(()).unwrap();
        assert!(count >= 3, "periodic should have re-armed several times, got {count}");
    });
    // Every tick delivered the same payload.
    assert!(fired.lock().unwrap().iter().all(|&v| v == 9));
}

// Cancelling a periodic stops the re-arm: no further ticks land after cancel.
#[test]
fn cancel_stops_a_periodic() {
    let fired = Arc::new(Mutex::new(Vec::new()));
    let cancel_won = Arc::new(Mutex::new(None));
    let f2 = fired.clone();
    let c2 = cancel_won.clone();
    run(move || {
        let server = start(timed(f2, c2));
        server.cast(TkCast::Tick(Duration::from_millis(20))).unwrap();
        let _ = server.call(()).unwrap();
        smarm::sleep(Duration::from_millis(70)); // a few ticks
        server.cast(TkCast::CancelLast).unwrap();
        let after_cancel = server.call(()).unwrap(); // sync: cancel handled
        smarm::sleep(Duration::from_millis(80)); // would be several more ticks
        let later = server.call(()).unwrap();
        assert_eq!(later, after_cancel, "no ticks may land after cancel");
    });
    // The periodic had fired at least once before being cancelled.
    assert!(!fired.lock().unwrap().is_empty());
}

// ---------------------------------------------------------------------------
// RFC 015 §4.4 — idle / receive timeout. A server that sets an idle window in
// init and counts handle_idle fires; casts are traffic that resets the window.
// ---------------------------------------------------------------------------
struct Idler {
    window: Duration,
    idles: Arc<Mutex<u32>>,
}

impl GenServer for Idler {
    type Call = ();
    type Reply = u32; // idle fire count
    type Cast = (); // a poke: traffic that resets the idle window
    type Info = ();
    type Timer = ();

    fn init(&mut self, ctx: &ServerCtx<Self>) {
        ctx.idle_after(self.window);
    }
    fn handle_call(&mut self, _: ()) -> u32 {
        *self.idles.lock().unwrap()
    }
    fn handle_cast(&mut self, _: ()) {}
    fn handle_idle(&mut self) {
        *self.idles.lock().unwrap() += 1;
    }
}

// A quiet inbox fires handle_idle, and the window re-arms (steady detector):
// several fires across a quiet span.
#[test]
fn idle_fires_repeatedly_on_quiet() {
    let idles = Arc::new(Mutex::new(0));
    let i2 = idles.clone();
    run(move || {
        let server = start(Idler { window: Duration::from_millis(25), idles: i2 });
        smarm::sleep(Duration::from_millis(130)); // quiet ⇒ ~5 windows
        drop(server); // keep the server alive across the quiet span
    });
    assert!(*idles.lock().unwrap() >= 2, "idle should re-arm and fire several times");
}

// Traffic within the window keeps idle from firing; only once the inbox goes
// quiet does handle_idle fire.
#[test]
fn traffic_resets_the_idle_window() {
    let idles = Arc::new(Mutex::new(0));
    let i2 = idles.clone();
    let before_quiet = Arc::new(Mutex::new(u32::MAX));
    let bq = before_quiet.clone();
    run(move || {
        let server = start(Idler { window: Duration::from_millis(60), idles: i2 });
        // Poke every 25ms (< 60ms window) for ~100ms: each cast resets the
        // window before it can elapse.
        for _ in 0..4 {
            server.cast(()).unwrap();
            smarm::sleep(Duration::from_millis(25));
        }
        *bq.lock().unwrap() = server.call(()).unwrap(); // count while traffic kept it quiet-free
        smarm::sleep(Duration::from_millis(140)); // now genuinely quiet
        drop(server);
    });
    assert_eq!(*before_quiet.lock().unwrap(), 0, "steady traffic must suppress idle");
    assert!(*idles.lock().unwrap() >= 1, "idle fires once the inbox falls quiet");
}