smarm/tests/gen_statem.rs

//! gen_statem behaviour tests, driven through the `gen_statem!` macro: cast/call
//! round-trip, `enter` firing on start and on every real transition (but not on
//! a stay), the machine-down path when a handler panics, and the timeout
//! surface (state-timeout firing + auto-reset across transitions; named
//! timeouts surviving transitions; cancellation).

use smarm::gen_statem;
use smarm::gen_statem::{CallError, Reply};
use smarm::run;
use std::sync::{Arc, Mutex};
use std::time::Duration;

// ===========================================================================
// Timeouts
// ===========================================================================
//
// A small timer machine. `Idle` is quiet; `Armed` arms a state-timeout on entry
// that — when it fires — bumps `st_fires` and returns to `Idle`. A named
// timeout ("ping") is armed independently, survives the Idle/Armed transition,
// and bumps `named_fires` when it fires. Counters are read back over calls.
//
// Durations are tiny and waits use `smarm::sleep` (parks the actor, leaves the
// timer wheel turning). These tests run against real time, so they are a touch
// slow; a controllable clock would tighten them.

#[derive(Clone, Copy, PartialEq, Eq, Debug)]
enum T {
    Idle,
    Armed,
}

struct TData {
    enters: u32,      // total state entries (incl. initial)
    st_fires: u32,    // state-timeout fires
    named_fires: u32, // named-timeout fires
    st_window: u64,   // ms for the Armed state-timeout (set per test intent)
}

enum TCast {
    Arm,        // Idle -> Armed
    Disarm,     // Armed -> Idle (a transition that should auto-reset the state-timeout)
    Ping(u64),  // arm a named "ping" timeout after the given ms
    CancelPing, // cancel the named "ping"
}

enum TCall {
    Enters(Reply<u32>),
    StFires(Reply<u32>),
    NamedFires(Reply<u32>),
    Boom(Reply<u32>), // panics, to exercise the call-to-dead-machine path
}

gen_statem! {
    machine: TimerSm { state: T, data: TData };
    event:   Ev2 { cast: TCast, call: TCall, info: () };
    context(data, prev, cx);

    enter {
        // On entering Armed, arm the state-timeout. On Idle, nothing — and the
        // loop has already auto-reset any pending state-timeout on the way in.
        T::Armed => { data.enters += 1; cx.state_timeout(Duration::from_millis(data.st_window)); },
        T::Idle  => data.enters += 1,
    }

    on T::Idle => {
        cast TCast::Arm    => T::Armed,
        cast TCast::Disarm => unhandled,
        state_timeout      => unhandled,
    }

    on T::Armed => {
        // The state-timeout elapsed while still Armed: count it and go Idle.
        state_timeout      => { data.st_fires += 1; T::Idle },
        cast TCast::Disarm => T::Idle,
        cast TCast::Arm    => unhandled,
    }

    // State-independent rows: the named-timeout (survives transitions), the
    // arm/cancel casts, the counter reads, and the panicking call.
    on _ => {
        cast TCast::Ping(ms)      => { cx.timeout("ping", Duration::from_millis(ms)); prev },
        cast TCast::CancelPing    => { cx.cancel_timeout("ping"); prev },
        timeout "ping"            => { data.named_fires += 1; prev },
        timeout _                 => unhandled,
        call TCall::Enters(r)     => { r.reply(data.enters); prev },
        call TCall::StFires(r)    => { r.reply(data.st_fires); prev },
        call TCall::NamedFires(r) => { r.reply(data.named_fires); prev },
        call TCall::Boom(_r)      => boom(),
    }
}

fn boom() -> T {
    panic!("boom")
}

// A state-timeout armed on entry to Armed fires after its window, bumping the
// counter and returning the machine to Idle on its own.
#[test]
fn state_timeout_fires() {
    let got = Arc::new(Mutex::new(0u32));
    let got2 = got.clone();
    run(move || {
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 5 });
        m.send(Ev2::Cast(TCast::Arm)).unwrap(); // -> Armed, arms 5ms state-timeout
        smarm::sleep(Duration::from_millis(40)); // let it fire
        *got2.lock().unwrap() = m.call(|r| Ev2::Call(TCall::StFires(r))).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), 1, "state-timeout fired exactly once");
}

// Leaving Armed before the window elapses auto-resets the state-timeout: it
// must not fire afterward, even though we wait well past its original window.
#[test]
fn state_timeout_auto_resets_on_transition() {
    let got = Arc::new(Mutex::new(99u32));
    let got2 = got.clone();
    run(move || {
        // Long window so the explicit Disarm beats it comfortably.
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 50 });
        m.send(Ev2::Cast(TCast::Arm)).unwrap(); // -> Armed, arms 50ms state-timeout
        m.send(Ev2::Cast(TCast::Disarm)).unwrap(); // -> Idle, auto-resets it
        smarm::sleep(Duration::from_millis(80)); // past the original window
        *got2.lock().unwrap() = m.call(|r| Ev2::Call(TCall::StFires(r))).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), 0, "auto-reset cancelled the pending state-timeout");
}

// A named timeout survives a state change: armed in Idle, it still fires after
// the machine has moved to Armed and back.
#[test]
fn named_timeout_survives_transition() {
    let got = Arc::new(Mutex::new(0u32));
    let got2 = got.clone();
    run(move || {
        // Armed's own state-timeout is long so it doesn't interfere.
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 200 });
        m.send(Ev2::Cast(TCast::Ping(20))).unwrap(); // arm "ping" for 20ms (in Idle)
        m.send(Ev2::Cast(TCast::Arm)).unwrap(); // -> Armed (ping must survive this)
        m.send(Ev2::Cast(TCast::Disarm)).unwrap(); // -> Idle (and this)
        smarm::sleep(Duration::from_millis(60)); // let "ping" fire
        *got2.lock().unwrap() = m.call(|r| Ev2::Call(TCall::NamedFires(r))).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), 1, "named timeout fired across the transitions");
}

// Cancelling a named timeout before its window prevents the fire.
#[test]
fn named_timeout_cancel() {
    let got = Arc::new(Mutex::new(99u32));
    let got2 = got.clone();
    run(move || {
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 200 });
        m.send(Ev2::Cast(TCast::Ping(30))).unwrap(); // arm "ping" for 30ms
        m.send(Ev2::Cast(TCast::CancelPing)).unwrap(); // cancel before it fires
        smarm::sleep(Duration::from_millis(60)); // past the original window
        *got2.lock().unwrap() = m.call(|r| Ev2::Call(TCall::NamedFires(r))).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), 0, "cancel prevented the named-timeout fire");
}

// ===========================================================================
// Core behaviour (cast/call round-trip, enter semantics, panic -> Down)
// ===========================================================================

// Casts are applied in order and a later call observes the resulting state via
// its counters: two Arm/Disarm round-trips leave the machine back in Idle.
#[test]
fn cast_then_call_roundtrip() {
    let got = Arc::new(Mutex::new(0u32));
    let got2 = got.clone();
    run(move || {
        // Long state-timeout window so it never fires during the test.
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 10_000 });
        m.send(Ev2::Cast(TCast::Arm)).unwrap();    // Idle  -> Armed (enter)
        m.send(Ev2::Cast(TCast::Disarm)).unwrap(); // Armed -> Idle  (enter)
        m.send(Ev2::Cast(TCast::Arm)).unwrap();    // Idle  -> Armed (enter)
        m.send(Ev2::Cast(TCast::Disarm)).unwrap(); // Armed -> Idle  (enter)
        // enters = 1 (start) + 4 transitions = 5.
        *got2.lock().unwrap() = m.call(|r| Ev2::Call(TCall::Enters(r))).unwrap();
    });
    assert_eq!(*got.lock().unwrap(), 5, "one enter on start, one per real transition");
}

// `enter` fires once on start and once per *real* transition; a stay (a call
// that returns the current tag) does not re-enter.
#[test]
fn enter_on_start_and_each_transition_but_not_stay() {
    let got = Arc::new(Mutex::new((0u32, 0u32, 0u32)));
    let got2 = got.clone();
    run(move || {
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 10_000 }); // enter -> 1
        let after_start = m.call(|r| Ev2::Call(TCall::Enters(r))).unwrap();
        // A stay (a counter read returns `prev`) must not bump enters.
        let _ = m.call(|r| Ev2::Call(TCall::StFires(r))).unwrap();
        let still = m.call(|r| Ev2::Call(TCall::Enters(r))).unwrap();
        m.send(Ev2::Cast(TCast::Arm)).unwrap(); // Idle -> Armed -> enter -> 2
        let after_arm = m.call(|r| Ev2::Call(TCall::Enters(r))).unwrap();
        *got2.lock().unwrap() = (after_start, still, after_arm);
    });
    assert_eq!(*got.lock().unwrap(), (1, 1, 2));
}

// A handler that panics tears the loop down; the in-flight call's reply channel
// closes as the stack unwinds, so the parked caller wakes with Down (mirrors
// gen_server's panicking-handler path).
#[test]
fn call_to_panicking_handler_is_down() {
    let got = Arc::new(Mutex::new(None::<Result<u32, CallError>>));
    let got2 = got.clone();
    run(move || {
        let m = TimerSm::start(T::Idle, TData { enters: 0, st_fires: 0, named_fires: 0, st_window: 10_000 });
        let r = m.call(|rep| Ev2::Call(TCall::Boom(rep)));
        *got2.lock().unwrap() = Some(r);
    });
    assert_eq!(*got.lock().unwrap(), Some(Err(CallError::Down)));
}