use once_spin::*;
use std::{
    mem::forget,
    sync::atomic::{AtomicUsize, Ordering},
    sync::mpsc::channel,
    sync::Arc,
    thread,
};

#[derive(Eq, PartialEq, Debug)]
struct NonCopy(i32);

#[test]
fn smoke() {
    let l = RwLock::new(());
    drop(l.read());
    drop(l.write());
    drop((l.read(), l.read()));
    drop(l.write());
}

#[test]
fn test_rw_arc() {
    let arc = Arc::new(RwLock::new(0));
    let arc2 = arc.clone();
    let (tx, rx) = channel();

    thread::spawn(move || {
        let mut lock = arc2.write();
        for _ in 0..10 {
            let tmp = *lock;
            *lock = -1;
            thread::yield_now();
            *lock = tmp + 1;
        }
        tx.send(()).unwrap();
    });

    let mut children = Vec::new();
    for _ in 0..5 {
        let arc3 = arc.clone();
        children.push(thread::spawn(move || {
            let lock = arc3.read();
            assert!(*lock >= 0);
        }));
    }

    for r in children {
        assert!(r.join().is_ok());
    }

    rx.recv().unwrap();
    let lock = arc.read();
    assert_eq!(*lock, 10);
}

#[test]
fn test_rw_access_in_unwind() {
    let arc = Arc::new(RwLock::new(1));
    let arc2 = arc.clone();
    let _ = thread::spawn(move || -> () {
        struct Unwinder {
            i: Arc<RwLock<isize>>,
        }

        impl Drop for Unwinder {
            fn drop(&mut self) {
                let mut lock = self.i.write();
                *lock += 1;
            }
        }
        let _u = Unwinder { i: arc2 };
        panic!();
    })
    .join();
    let lock = arc.read();
    assert_eq!(*lock, 2);
}

#[test]
fn test_rwlock_unsized() {
    let rw: &RwLock<[i32]> = &RwLock::new([1, 2, 3]);
    {
        let b = &mut *rw.write();
        b[0] = 4;
        b[2] = 5;
    }
    let comp: &[i32] = &[4, 2, 5];
    assert_eq!(&*rw.read(), comp);
}

#[test]
fn test_rwlock_try_write() {
    let lock = RwLock::new(0isize);
    let read_guard = lock.read();
    let write_result = lock.try_write();
    match write_result {
        None => (),
        Some(_) => assert!(
            false,
            "try_write should not succeed while read_guard is in scope"
        ),
    }
    drop(read_guard);
}

#[test]
fn test_rw_try_read() {
    let m = RwLock::new(0);
    forget(m.write());
    assert!(m.try_read().is_none());
}

#[test]
fn test_into_inner() {
    let m = RwLock::new(NonCopy(10));
    assert_eq!(m.into_inner(), NonCopy(10));
}

#[test]
fn test_into_inner_drop() {
    struct Foo(Arc<AtomicUsize>);

    impl Drop for Foo {
        fn drop(&mut self) {
            self.0.fetch_add(1, Ordering::SeqCst);
        }
    }
    let num_drops = Arc::new(AtomicUsize::new(0));
    let m = RwLock::new(Foo(num_drops.clone()));
    assert_eq!(num_drops.load(Ordering::SeqCst), 0);
    {
        let _inner = m.into_inner();
        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
    }
    assert_eq!(num_drops.load(Ordering::SeqCst), 1);
}

#[test]
fn test_force_read_decrement() {
    let m = RwLock::new(());
    forget(m.read());
    forget(m.read());
    forget(m.read());
    assert!(m.try_write().is_none());
    unsafe {
        m.force_read_decrement();
        m.force_read_decrement();
    }
    assert!(m.try_write().is_none());
    unsafe {
        m.force_read_decrement();
    }
    assert!(m.try_write().is_some());
}

#[test]
fn test_force_write_unlock() {
    let m = RwLock::new(());
    forget(m.write());
    assert!(m.try_read().is_none());
    unsafe {
        m.force_write_unlock();
    }
    assert!(m.try_read().is_some());
}

#[test]
fn test_upgrade_downgrade() {
    let m = RwLock::new(());
    {
        let _r = m.read();
        let upg = m.try_upgradeable_read().unwrap();
        assert!(m.try_read().is_none());
        assert!(m.try_write().is_none());
        assert!(upg.try_upgrade().is_err());
    }
    {
        let w = m.write();
        assert!(m.try_upgradeable_read().is_none());
        let _r = w.downgrade();
        assert!(m.try_upgradeable_read().is_some());
        assert!(m.try_read().is_some());
        assert!(m.try_write().is_none());
    }
    {
        let _u = m.upgradeable_read();
        assert!(m.try_upgradeable_read().is_none());
    }
    assert!(m.try_upgradeable_read().unwrap().try_upgrade().is_ok());
}