#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
#![cfg_attr(feature = "nightly", feature(never_type))]

use std::boxed::Box;
use std::future::{poll_fn, Future};
use std::sync::{Arc, Mutex};
use std::task::Poll;

use embassy_executor::raw::Executor;
use embassy_executor::{task, Spawner};

#[export_name = "__pender"]
fn __pender(context: *mut ()) {
    unsafe {
        let trace = &*(context as *const Trace);
        trace.push("pend");
    }
}

#[derive(Clone)]
struct Trace {
    trace: Arc<Mutex<Vec<&'static str>>>,
}

impl Trace {
    fn new() -> Self {
        Self {
            trace: Arc::new(Mutex::new(Vec::new())),
        }
    }
    fn push(&self, value: &'static str) {
        self.trace.lock().unwrap().push(value)
    }

    fn get(&self) -> Vec<&'static str> {
        self.trace.lock().unwrap().clone()
    }
}

fn setup() -> (&'static Executor, Trace) {
    let trace = Trace::new();
    let context = Box::leak(Box::new(trace.clone())) as *mut _ as *mut ();
    let executor = &*Box::leak(Box::new(Executor::new(context)));

    (executor, trace)
}

#[test]
fn executor_noop() {
    let (executor, trace) = setup();
    unsafe { executor.poll() };
    assert!(trace.get().is_empty())
}

#[test]
fn executor_task() {
    #[task]
    async fn task1(trace: Trace) {
        trace.push("poll task1")
    }

    #[task]
    async fn task2() -> ! {
        panic!()
    }

    let (executor, trace) = setup();
    executor.spawner().spawn(task1(trace.clone())).unwrap();

    unsafe { executor.poll() };
    unsafe { executor.poll() };

    assert_eq!(
        trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "poll task1", // poll only once.
        ]
    )
}

#[test]
fn executor_task_rpit() {
    #[task]
    fn task1(trace: Trace) -> impl Future<Output = ()> {
        async move { trace.push("poll task1") }
    }

    #[cfg(feature = "nightly")]
    #[task]
    fn task2() -> impl Future<Output = !> {
        async { panic!() }
    }

    let (executor, trace) = setup();
    executor.spawner().spawn(task1(trace.clone())).unwrap();

    unsafe { executor.poll() };
    unsafe { executor.poll() };

    assert_eq!(
        trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "poll task1", // poll only once.
        ]
    )
}

#[test]
fn executor_task_self_wake() {
    #[task]
    async fn task1(trace: Trace) {
        poll_fn(|cx| {
            trace.push("poll task1");
            cx.waker().wake_by_ref();
            Poll::Pending
        })
        .await
    }

    let (executor, trace) = setup();
    executor.spawner().spawn(task1(trace.clone())).unwrap();

    unsafe { executor.poll() };
    unsafe { executor.poll() };

    assert_eq!(
        trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "poll task1", //
            "pend",       // task self-wakes
            "poll task1", //
            "pend",       // task self-wakes
        ]
    )
}

#[test]
fn executor_task_self_wake_twice() {
    #[task]
    async fn task1(trace: Trace) {
        poll_fn(|cx| {
            trace.push("poll task1");
            cx.waker().wake_by_ref();
            trace.push("poll task1 wake 2");
            cx.waker().wake_by_ref();
            Poll::Pending
        })
        .await
    }

    let (executor, trace) = setup();
    executor.spawner().spawn(task1(trace.clone())).unwrap();

    unsafe { executor.poll() };
    unsafe { executor.poll() };

    assert_eq!(
        trace.get(),
        &[
            "pend",              // spawning a task pends the executor
            "poll task1",        //
            "pend",              // task self-wakes
            "poll task1 wake 2", // task self-wakes again, shouldn't pend
            "poll task1",        //
            "pend",              // task self-wakes
            "poll task1 wake 2", // task self-wakes again, shouldn't pend
        ]
    )
}

#[test]
fn waking_after_completion_does_not_poll() {
    use embassy_sync::waitqueue::AtomicWaker;

    #[task]
    async fn task1(trace: Trace, waker: &'static AtomicWaker) {
        poll_fn(|cx| {
            trace.push("poll task1");
            waker.register(cx.waker());
            Poll::Ready(())
        })
        .await
    }

    let waker = Box::leak(Box::new(AtomicWaker::new()));

    let (executor, trace) = setup();
    executor.spawner().spawn(task1(trace.clone(), waker)).unwrap();

    unsafe { executor.poll() };
    waker.wake();
    unsafe { executor.poll() };

    // Exited task may be waken but is not polled
    waker.wake();
    waker.wake();
    unsafe { executor.poll() }; // Clears running status

    // Can respawn waken-but-dead task
    executor.spawner().spawn(task1(trace.clone(), waker)).unwrap();

    unsafe { executor.poll() };

    assert_eq!(
        trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "poll task1", //
            "pend",       // manual wake, gets cleared by poll
            "pend",       // manual wake, single pend for two wakes
            "pend",       // respawning a task pends the executor
            "poll task1", //
        ]
    )
}

#[test]
fn waking_with_old_waker_after_respawn() {
    use embassy_sync::waitqueue::AtomicWaker;

    async fn yield_now(trace: Trace) {
        let mut yielded = false;
        poll_fn(|cx| {
            if yielded {
                Poll::Ready(())
            } else {
                trace.push("yield_now");
                yielded = true;
                cx.waker().wake_by_ref();
                Poll::Pending
            }
        })
        .await
    }

    #[task]
    async fn task1(trace: Trace, waker: &'static AtomicWaker) {
        yield_now(trace.clone()).await;
        poll_fn(|cx| {
            trace.push("poll task1");
            waker.register(cx.waker());
            Poll::Ready(())
        })
        .await;
    }

    let waker = Box::leak(Box::new(AtomicWaker::new()));

    let (executor, trace) = setup();
    executor.spawner().spawn(task1(trace.clone(), waker)).unwrap();

    unsafe { executor.poll() };
    unsafe { executor.poll() }; // progress to registering the waker
    waker.wake();
    unsafe { executor.poll() };
    // Task has exited

    assert_eq!(
        trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "yield_now",  //
            "pend",       // yield_now wakes the task
            "poll task1", //
            "pend",       // task self-wakes
        ]
    );

    // Can respawn task on another executor
    let (other_executor, other_trace) = setup();
    other_executor
        .spawner()
        .spawn(task1(other_trace.clone(), waker))
        .unwrap();

    unsafe { other_executor.poll() }; // just run to the yield_now
    waker.wake(); // trigger old waker registration
    unsafe { executor.poll() };
    unsafe { other_executor.poll() };

    // First executor's trace has not changed
    assert_eq!(
        trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "yield_now",  //
            "pend",       // yield_now wakes the task
            "poll task1", //
            "pend",       // task self-wakes
        ]
    );

    assert_eq!(
        other_trace.get(),
        &[
            "pend",       // spawning a task pends the executor
            "yield_now",  //
            "pend",       // manual wake, gets cleared by poll
            "poll task1", //
        ]
    );
}

#[test]
fn executor_task_cfg_args() {
    // simulate cfg'ing away argument c
    #[task]
    async fn task1(a: u32, b: u32, #[cfg(any())] c: u32) {
        let (_, _) = (a, b);
    }

    #[task]
    async fn task2(a: u32, b: u32, #[cfg(all())] c: u32) {
        let (_, _, _) = (a, b, c);
    }
}

#[test]
fn recursive_task() {
    #[embassy_executor::task(pool_size = 2)]
    async fn task1() {
        let spawner = unsafe { Spawner::for_current_executor().await };
        spawner.spawn(task1());
    }
}