//! Timer / sleep tests. These are time-sensitive and use generous
//! tolerances — we care about ordering and "didn't return instantly /
//! didn't take forever," not microsecond-precise scheduling.

use smarm::{run, sleep, spawn};
use std::sync::Arc;
use std::sync::Mutex;
use std::time::{Duration, Instant};

#[test]
fn sleep_returns_after_at_least_the_requested_duration() {
    run(|| {
        let t0 = Instant::now();
        sleep(Duration::from_millis(50));
        let elapsed = t0.elapsed();
        assert!(
            elapsed >= Duration::from_millis(45),
            "slept only {:?}, expected ≥ ~50ms",
            elapsed
        );
        // Loose upper bound — anything wildly slow indicates a bug.
        assert!(
            elapsed < Duration::from_millis(500),
            "slept {:?}, far longer than the 50ms request",
            elapsed
        );
    });
}

#[test]
fn shorter_sleep_wakes_first() {
    let log: Arc<Mutex<Vec<u8>>> = Arc::new(Mutex::new(Vec::new()));
    let l1 = log.clone();
    let l2 = log.clone();

    run(move || {
        let h1 = spawn(move || {
            sleep(Duration::from_millis(60));
            l1.lock().unwrap().push(1);
        });
        let h2 = spawn(move || {
            sleep(Duration::from_millis(20));
            l2.lock().unwrap().push(2);
        });
        h1.join().unwrap();
        h2.join().unwrap();
    });

    // 2 (shorter sleep) wakes before 1.
    assert_eq!(*log.lock().unwrap(), vec![2, 1]);
}

#[test]
fn one_sleeping_actor_does_not_block_other_runnable_actors() {
    let log: Arc<Mutex<Vec<u8>>> = Arc::new(Mutex::new(Vec::new()));
    let l1 = log.clone();
    let l2 = log.clone();

    run(move || {
        let h1 = spawn(move || {
            sleep(Duration::from_millis(100));
            l1.lock().unwrap().push(1);
        });
        let h2 = spawn(move || {
            // Doesn't sleep. Should be able to run while h1 is parked.
            for _ in 0..3 {
                l2.lock().unwrap().push(2);
                smarm::yield_now();
            }
        });
        h2.join().unwrap();
        h1.join().unwrap();
    });

    let v = log.lock().unwrap();
    // h2 finishes long before h1's 100ms timer.
    let h2_count = v.iter().filter(|&&x| x == 2).count();
    let h1_pos = v.iter().position(|&x| x == 1);
    assert_eq!(h2_count, 3);
    // h1's push should land after h2 is fully done.
    if let Some(p) = h1_pos {
        assert!(p >= h2_count, "h1 woke before h2 finished: log = {:?}", *v);
    }
}

#[test]
fn zero_duration_sleep_yields_but_does_not_park_forever() {
    // A zero-duration sleep should behave like yield_now: control returns
    // promptly without hanging.
    run(|| {
        let t0 = Instant::now();
        sleep(Duration::from_millis(0));
        assert!(t0.elapsed() < Duration::from_millis(100));
    });
}

#[test]
fn many_concurrent_sleepers_all_wake() {
    let counter = Arc::new(std::sync::atomic::AtomicU32::new(0));
    let c = counter.clone();
    run(move || {
        let mut handles = Vec::new();
        for i in 0..20u64 {
            let cc = c.clone();
            handles.push(spawn(move || {
                // Stagger so they don't all coalesce to the same wake.
                sleep(Duration::from_millis(5 + i * 2));
                cc.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
            }));
        }
        for h in handles {
            h.join().unwrap();
        }
    });
    assert_eq!(counter.load(std::sync::atomic::Ordering::SeqCst), 20);
}