rgpui 0.1.1

use super::{
    BackgroundExecutor, Clock, ForegroundExecutor, Instant, Priority, RunnableMeta, Scheduler,
    SessionId, TestClock, Timer,
};
use async_task::Runnable;
use backtrace::{Backtrace, BacktraceFrame};
use futures::channel::oneshot;
use parking_lot::{Mutex, MutexGuard};
use rand::{
    distr::{StandardUniform, uniform::SampleRange, uniform::SampleUniform},
    prelude::*,
};
use std::{
    any::type_name_of_val,
    collections::{BTreeMap, HashSet, VecDeque},
    env,
    fmt::Write,
    future::Future,
    mem,
    ops::RangeInclusive,
    panic::{self, AssertUnwindSafe},
    pin::Pin,
    sync::{
        Arc,
        atomic::{AtomicBool, Ordering::SeqCst},
    },
    task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
    thread::{self, Thread},
    time::Duration,
};

const PENDING_TRACES_VAR_NAME: &str = "PENDING_TRACES";

pub struct TestScheduler {
    clock: Arc<TestClock>,
    rng: Arc<Mutex<StdRng>>,
    state: Arc<Mutex<SchedulerState>>,
    thread: Thread,
}

impl TestScheduler {
    /// 使用默认配置（种子 0）运行一次测试
    pub fn once<R>(f: impl AsyncFnOnce(Arc<TestScheduler>) -> R) -> R {
        Self::with_seed(0, f)
    }

    /// 使用连续种子（0、1、2、...）多次运行测试
    pub fn many<R>(
        default_iterations: usize,
        mut f: impl AsyncFnMut(Arc<TestScheduler>) -> R,
    ) -> Vec<R> {
        let num_iterations = std::env::var("ITERATIONS")
            .map(|iterations| iterations.parse().unwrap())
            .unwrap_or(default_iterations);

        let seed = std::env::var("SEED")
            .map(|seed| seed.parse().unwrap())
            .unwrap_or(0);

        (seed..seed + num_iterations as u64)
            .map(|seed| {
                let mut unwind_safe_f = AssertUnwindSafe(&mut f);
                eprintln!("Running seed: {seed}");
                match panic::catch_unwind(move || Self::with_seed(seed, &mut *unwind_safe_f)) {
                    Ok(result) => result,
                    Err(error) => {
                        eprintln!("\x1b[31mFailing Seed: {seed}\x1b[0m");
                        panic::resume_unwind(error);
                    }
                }
            })
            .collect()
    }

    fn with_seed<R>(seed: u64, f: impl AsyncFnOnce(Arc<TestScheduler>) -> R) -> R {
        let scheduler = Arc::new(TestScheduler::new(TestSchedulerConfig::with_seed(seed)));
        let future = f(scheduler.clone());
        let result = scheduler.foreground().block_on(future);
        scheduler.run(); // 确保生成的任务在测试返回前完成
        result
    }

    pub fn new(config: TestSchedulerConfig) -> Self {
        Self {
            rng: Arc::new(Mutex::new(StdRng::seed_from_u64(config.seed))),
            state: Arc::new(Mutex::new(SchedulerState {
                runnables: VecDeque::new(),
                timers: Vec::new(),
                blocked_sessions: Vec::new(),
                randomize_order: config.randomize_order,
                allow_parking: config.allow_parking,
                timeout_ticks: config.timeout_ticks,
                next_session_id: SessionId(0),
                capture_pending_traces: config.capture_pending_traces,
                pending_traces: BTreeMap::new(),
                next_trace_id: TraceId(0),
                is_main_thread: true,
                non_determinism_error: None,
                finished: false,
                parking_allowed_once: false,
                unparked: false,
            })),
            clock: Arc::new(TestClock::new()),
            thread: thread::current(),
        }
    }

    pub fn end_test(&self) {
        let mut state = self.state.lock();
        if let Some((message, backtrace)) = &state.non_determinism_error {
            panic!("{}\n{:?}", message, backtrace)
        }
        state.finished = true;
    }

    pub fn clock(&self) -> Arc<TestClock> {
        self.clock.clone()
    }

    pub fn rng(&self) -> SharedRng {
        SharedRng(self.rng.clone())
    }

    pub fn set_timeout_ticks(&self, timeout_ticks: RangeInclusive<usize>) {
        self.state.lock().timeout_ticks = timeout_ticks;
    }

    pub fn allow_parking(&self) {
        let mut state = self.state.lock();
        state.allow_parking = true;
        state.parking_allowed_once = true;
    }

    pub fn forbid_parking(&self) {
        self.state.lock().allow_parking = false;
    }

    pub fn parking_allowed(&self) -> bool {
        self.state.lock().allow_parking
    }

    pub fn is_main_thread(&self) -> bool {
        self.state.lock().is_main_thread
    }

    /// 分配新的会话 ID 用于前台任务调度。
    /// 这由 GPUI 的 TestDispatcher 用于将调度器实例映射到会话。
    pub fn allocate_session_id(&self) -> SessionId {
        let mut state = self.state.lock();
        state.next_session_id.0 += 1;
        state.next_session_id
    }

    /// 为此调度器创建前台执行器
    pub fn foreground(self: &Arc<Self>) -> ForegroundExecutor {
        let session_id = self.allocate_session_id();
        ForegroundExecutor::new(session_id, self.clone())
    }

    /// 为此调度器创建后台执行器
    pub fn background(self: &Arc<Self>) -> BackgroundExecutor {
        BackgroundExecutor::new(self.clone())
    }

    pub fn yield_random(&self) -> Yield {
        let rng = &mut *self.rng.lock();
        if rng.random_bool(0.1) {
            Yield(rng.random_range(10..20))
        } else {
            Yield(rng.random_range(0..2))
        }
    }

    pub fn run(&self) {
        while self.step() {
            // Continue until no work remains
        }
    }

    pub fn run_with_clock_advancement(&self) {
        while self.step() || self.advance_clock_to_next_timer() {
            // Continue until no work remains
        }
    }

    /// 执行调度器的一个 tick，处理已过期的计时器并运行
    /// 最多一个任务。如果有任何工作完成则返回 true。
    ///
    /// 这是 GPUI 的 TestDispatcher 驱动任务执行的公共接口。
    pub fn tick(&self) -> bool {
        self.step_filtered(false)
    }

    /// 执行一个 tick，但仅运行后台任务（无前台/会话任务）。
    /// 如果有任何工作完成则返回 true。
    pub fn tick_background_only(&self) -> bool {
        self.step_filtered(true)
    }

    /// 检查是否有任何可以运行的待处理任务或计时器。
    pub fn has_pending_tasks(&self) -> bool {
        let state = self.state.lock();
        !state.runnables.is_empty() || !state.timers.is_empty()
    }

    /// 返回当前排队的（前台任务，后台任务）数量。
    /// 前台任务是那些有 session_id 的，后台任务没有。
    pub fn pending_task_counts(&self) -> (usize, usize) {
        let state = self.state.lock();
        let foreground = state
            .runnables
            .iter()
            .filter(|r| r.session_id.is_some())
            .count();
        let background = state
            .runnables
            .iter()
            .filter(|r| r.session_id.is_none())
            .count();
        (foreground, background)
    }

    fn step(&self) -> bool {
        self.step_filtered(false)
    }

    fn step_filtered(&self, background_only: bool) -> bool {
        let (elapsed_count, runnables_before) = {
            let mut state = self.state.lock();
            let end_ix = state
                .timers
                .partition_point(|timer| timer.expiration <= self.clock.now());
            let elapsed: Vec<_> = state.timers.drain(..end_ix).collect();
            let count = elapsed.len();
            let runnables = state.runnables.len();
            drop(state);
            // Dropping elapsed timers here wakes the waiting futures
            drop(elapsed);
            (count, runnables)
        };

        if elapsed_count > 0 {
            let runnables_after = self.state.lock().runnables.len();
            if std::env::var("DEBUG_SCHEDULER").is_ok() {
                eprintln!(
                    "[scheduler] Expired {} timers at {:?}, runnables: {} -> {}",
                    elapsed_count,
                    self.clock.now(),
                    runnables_before,
                    runnables_after
                );
            }
            return true;
        }

        let runnable = {
            let state = &mut *self.state.lock();

            // 查找候选任务：
            // - 对于前台任务（有 session_id），只有每个会话的第一个任务
            //   是候选任务（以保持会话内顺序）
            // - 对于后台任务（无 session_id），所有都是候选任务
            // - 排除被阻塞会话的任务
            // - 如果 background_only 为 true，则完全跳过前台任务
            let mut seen_sessions = HashSet::new();
            let candidate_indices: Vec<usize> = state
                .runnables
                .iter()
                .enumerate()
                .filter(|(_, runnable)| {
                    if let Some(session_id) = runnable.session_id {
                        // 如果 background_only 模式则跳过前台任务
                        if background_only {
                            return false;
                        }
                        // 排除被阻塞会话的任务
                        if state.blocked_sessions.contains(&session_id) {
                            return false;
                        }
                        // 仅包含每个会话的第一个任务（如果为新会话则 insert 返回 true）
                        seen_sessions.insert(session_id)
                    } else {
                        // 后台任务始终是候选任务
                        true
                    }
                })
                .map(|(ix, _)| ix)
                .collect();

            if candidate_indices.is_empty() {
                None
            } else if state.randomize_order {
                // Use priority-weighted random selection
                let weights: Vec<u32> = candidate_indices
                    .iter()
                    .map(|&ix| state.runnables[ix].priority.weight())
                    .collect();
                let total_weight: u32 = weights.iter().sum();

                if total_weight == 0 {
                    // Fallback to uniform random if all weights are zero
                    let choice = self.rng.lock().random_range(0..candidate_indices.len());
                    state.runnables.remove(candidate_indices[choice])
                } else {
                    let mut target = self.rng.lock().random_range(0..total_weight);
                    let mut selected_idx = 0;
                    for (i, &weight) in weights.iter().enumerate() {
                        if target < weight {
                            selected_idx = i;
                            break;
                        }
                        target -= weight;
                    }
                    state.runnables.remove(candidate_indices[selected_idx])
                }
            } else {
                // 非随机化：只需取第一个候选任务
                state.runnables.remove(candidate_indices[0])
            }
        };

        if let Some(runnable) = runnable {
            let is_foreground = runnable.session_id.is_some();
            let was_main_thread = self.state.lock().is_main_thread;
            self.state.lock().is_main_thread = is_foreground;
            runnable.run();
            self.state.lock().is_main_thread = was_main_thread;
            return true;
        }

        false
    }

    /// 从调度器中丢弃所有任务。
    ///
    /// 这被泄漏检测器使用，以确保所有任务都被丢弃，因为任务可能会使实体保持活动状态。
    /// 你可能会问，为什么测试完成时我们还有任务剩下。原因很简单，调度器本身是执行器，它保留已调度的可运行对象。
    /// 许多任务，包括每个前台任务都包含一个执行器句柄，使测试调度器保持活动状态，导致引用循环，因此目前需要此函数。
    pub fn drain_tasks(&self) {
        // 丢弃可运行对象可能会因包含执行器的 drop 实现而重新调度任务
        // 因此丢弃直到达到固定点
        loop {
            let mut state = self.state.lock();
            if state.runnables.is_empty() && state.timers.is_empty() {
                break;
            }
            let runnables = std::mem::take(&mut state.runnables);
            let timers = std::mem::take(&mut state.timers);
            drop(state);
            drop(timers);
            drop(runnables);
        }
    }

    pub fn advance_clock_to_next_timer(&self) -> bool {
        if let Some(timer) = self.state.lock().timers.first() {
            self.clock.advance(timer.expiration - self.clock.now());
            true
        } else {
            false
        }
    }

    pub fn advance_clock(&self, duration: Duration) {
        let debug = std::env::var("DEBUG_SCHEDULER").is_ok();
        let start = self.clock.now();
        let next_now = start + duration;
        if debug {
            let timer_count = self.state.lock().timers.len();
            eprintln!(
                "[scheduler] advance_clock({:?}) from {:?}, {} pending timers",
                duration, start, timer_count
            );
        }
        loop {
            self.run();
            if let Some(timer) = self.state.lock().timers.first()
                && timer.expiration <= next_now
            {
                let advance_to = timer.expiration;
                if debug {
                    eprintln!(
                        "[scheduler] Advancing clock {:?} -> {:?} for timer",
                        self.clock.now(),
                        advance_to
                    );
                }
                self.clock.advance(advance_to - self.clock.now());
            } else {
                break;
            }
        }
        self.clock.advance(next_now - self.clock.now());
        if debug {
            eprintln!(
                "[scheduler] advance_clock done, now at {:?}",
                self.clock.now()
            );
        }
    }

    fn park(&self, deadline: Option<Instant>) -> bool {
        if self.state.lock().allow_parking {
            let start = Instant::now();
            // 强制执行硬超时，防止测试无限期挂起
            let hard_deadline = start + Duration::from_secs(15);

            // 使用提供的 deadline 或硬超时 deadline 中较早的一个
            let effective_deadline = deadline
                .map(|d| d.min(hard_deadline))
                .unwrap_or(hard_deadline);

            // 以小间隔 park 以允许检查两个 deadline
            const PARK_INTERVAL: Duration = Duration::from_millis(100);
            loop {
                let now = Instant::now();
                if now >= effective_deadline {
                    // 检查是否达到硬超时
                    if now >= hard_deadline {
                        panic!(
                            "测试在 park 时超时 15 秒。\
                            这可能表示死锁或缺少唤醒器。",
                        );
                    }
                    // 达到提供的 deadline
                    return false;
                }

                let remaining = effective_deadline.saturating_duration_since(now);
                let park_duration = remaining.min(PARK_INTERVAL);
                let before_park = Instant::now();
                thread::park_timeout(park_duration);
                let elapsed = before_park.elapsed();

                // 推进测试时钟，推进 park 期间的实际时间
                self.clock.advance(elapsed);

                // 检查推进时钟后是否有任何计时器过期。
                // 如果是，返回以便调用者可以处理它们。
                if self
                    .state
                    .lock()
                    .timers
                    .first()
                    .map_or(false, |t| t.expiration <= self.clock.now())
                {
                    return true;
                }

                // 检查是否被其他线程唤醒。
                // 我们使用标志，因为基于时间的检测不可靠：
                // OS 调度延迟可能导致 elapsed >= park_duration，即使
                // 我们被 unpark() 提前唤醒。
                if std::mem::take(&mut self.state.lock().unparked) {
                    return true;
                }
            }
        } else if deadline.is_some() {
            false
        } else if self.state.lock().capture_pending_traces {
            let mut pending_traces = String::new();
            for (_, trace) in mem::take(&mut self.state.lock().pending_traces) {
                writeln!(pending_traces, "{:?}", exclude_wakers_from_trace(trace)).unwrap();
            }
            panic!("Parking forbidden. Pending traces:\n{}", pending_traces);
        } else {
            panic!(
                "Parking forbidden. Re-run with {PENDING_TRACES_VAR_NAME}=1 to show pending traces"
            );
        }
    }
}

fn assert_correct_thread(expected: &Thread, state: &Arc<Mutex<SchedulerState>>) {
    let current_thread = thread::current();
    let mut state = state.lock();
    if state.parking_allowed_once {
        return;
    }
    if current_thread.id() == expected.id() {
        return;
    }

    let message = format!(
        "Detected activity on thread {:?} {:?}, but test scheduler is running on {:?} {:?}. Your test is not deterministic.",
        current_thread.name(),
        current_thread.id(),
        expected.name(),
        expected.id(),
    );
    let backtrace = Backtrace::new();
    if state.finished {
        panic!("{}", message);
    } else {
        state.non_determinism_error = Some((message, backtrace))
    }
}

impl Scheduler for TestScheduler {
    /// 阻塞直到给定未来对象完成，带有可选超时。如果
    /// 未来对象在任何时刻无法取得进展且
    /// 没有其他任务或计时器剩余，除非允许 park 否则我们 panic。如果
    /// 允许 park，我们阻塞直到超时或无限期（如果未提供）。
    /// 这允许测试确定性和非确定性异步行为的混合，
    /// 例如在否则确定性的测试中与 I/O 交互时。
    fn block(
        &self,
        session_id: Option<SessionId>,
        mut future: Pin<&mut dyn Future<Output = ()>>,
        timeout: Option<Duration>,
    ) -> bool {
        if let Some(session_id) = session_id {
            self.state.lock().blocked_sessions.push(session_id);
        }

        let deadline = timeout.map(|timeout| Instant::now() + timeout);
        let awoken = Arc::new(AtomicBool::new(false));
        let waker = Box::new(TracingWaker {
            id: None,
            awoken: awoken.clone(),
            thread: self.thread.clone(),
            state: self.state.clone(),
        });
        let waker = unsafe { Waker::new(Box::into_raw(waker) as *const (), &WAKER_VTABLE) };
        let max_ticks = if timeout.is_some() {
            self.rng
                .lock()
                .random_range(self.state.lock().timeout_ticks.clone())
        } else {
            usize::MAX
        };
        let mut cx = Context::from_waker(&waker);

        let mut completed = false;
        for _ in 0..max_ticks {
            match future.as_mut().poll(&mut cx) {
                Poll::Ready(()) => {
                    completed = true;
                    break;
                }
                Poll::Pending => {}
            }

            let mut stepped = None;
            while self.rng.lock().random() {
                let stepped = stepped.get_or_insert(false);
                if self.step() {
                    *stepped = true;
                } else {
                    break;
                }
            }

            let stepped = stepped.unwrap_or(true);
            let awoken = awoken.swap(false, SeqCst);
            if !stepped && !awoken {
                let parking_allowed = self.state.lock().allow_parking;
                // 在确定性模式（不允许 park）中，立即跳转到下一个计时器。
                // 在非确定性模式（允许 park）中，让实际时间流逝。
                let advanced_to_timer = !parking_allowed && self.advance_clock_to_next_timer();
                if !advanced_to_timer && !self.park(deadline) {
                    break;
                }
            }
        }

        if session_id.is_some() {
            self.state.lock().blocked_sessions.pop();
        }

        completed
    }

    fn schedule_foreground(&self, session_id: SessionId, runnable: Runnable<RunnableMeta>) {
        assert_correct_thread(&self.thread, &self.state);
        let mut state = self.state.lock();
        let ix = if state.randomize_order {
            let start_ix = state
                .runnables
                .iter()
                .rposition(|task| task.session_id == Some(session_id))
                .map_or(0, |ix| ix + 1);
            self.rng
                .lock()
                .random_range(start_ix..=state.runnables.len())
        } else {
            state.runnables.len()
        };
        state.runnables.insert(
            ix,
            ScheduledRunnable {
                session_id: Some(session_id),
                priority: Priority::default(),
                runnable,
            },
        );
        state.unparked = true;
        drop(state);
        self.thread.unpark();
    }

    fn schedule_background_with_priority(
        &self,
        runnable: Runnable<RunnableMeta>,
        priority: Priority,
    ) {
        assert_correct_thread(&self.thread, &self.state);
        let mut state = self.state.lock();
        let ix = if state.randomize_order {
            self.rng.lock().random_range(0..=state.runnables.len())
        } else {
            state.runnables.len()
        };
        state.runnables.insert(
            ix,
            ScheduledRunnable {
                session_id: None,
                priority,
                runnable,
            },
        );
        state.unparked = true;
        drop(state);
        self.thread.unpark();
    }

    fn spawn_realtime(&self, f: Box<dyn FnOnce() + Send>) {
        std::thread::spawn(move || {
            f();
        });
    }

    #[track_caller]
    fn timer(&self, duration: Duration) -> Timer {
        let (tx, rx) = oneshot::channel();
        let state = &mut *self.state.lock();
        state.timers.push(ScheduledTimer {
            expiration: self.clock.now() + duration,
            _notify: tx,
        });
        state.timers.sort_by_key(|timer| timer.expiration);
        Timer(rx)
    }

    fn clock(&self) -> Arc<dyn Clock> {
        self.clock.clone()
    }

    fn as_test(&self) -> Option<&TestScheduler> {
        Some(self)
    }
}

#[derive(Clone, Debug)]
pub struct TestSchedulerConfig {
    pub seed: u64,
    pub randomize_order: bool,
    pub allow_parking: bool,
    pub capture_pending_traces: bool,
    pub timeout_ticks: RangeInclusive<usize>,
}

impl TestSchedulerConfig {
    pub fn with_seed(seed: u64) -> Self {
        Self {
            seed,
            ..Default::default()
        }
    }
}

impl Default for TestSchedulerConfig {
    fn default() -> Self {
        Self {
            seed: 0,
            randomize_order: true,
            allow_parking: false,
            capture_pending_traces: env::var(PENDING_TRACES_VAR_NAME)
                .map_or(false, |var| var == "1" || var == "true"),
            timeout_ticks: 1..=1000,
        }
    }
}

struct ScheduledRunnable {
    session_id: Option<SessionId>,
    priority: Priority,
    runnable: Runnable<RunnableMeta>,
}

impl ScheduledRunnable {
    fn run(self) {
        self.runnable.run();
    }
}

struct ScheduledTimer {
    expiration: Instant,
    _notify: oneshot::Sender<()>,
}

struct SchedulerState {
    runnables: VecDeque<ScheduledRunnable>,
    timers: Vec<ScheduledTimer>,
    blocked_sessions: Vec<SessionId>,
    randomize_order: bool,
    allow_parking: bool,
    timeout_ticks: RangeInclusive<usize>,
    next_session_id: SessionId,
    capture_pending_traces: bool,
    next_trace_id: TraceId,
    pending_traces: BTreeMap<TraceId, Backtrace>,
    is_main_thread: bool,
    non_determinism_error: Option<(String, Backtrace)>,
    parking_allowed_once: bool,
    finished: bool,
    unparked: bool,
}

const WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(
    TracingWaker::clone_raw,
    TracingWaker::wake_raw,
    TracingWaker::wake_by_ref_raw,
    TracingWaker::drop_raw,
);

#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord)]
struct TraceId(usize);

struct TracingWaker {
    id: Option<TraceId>,
    awoken: Arc<AtomicBool>,
    thread: Thread,
    state: Arc<Mutex<SchedulerState>>,
}

impl Clone for TracingWaker {
    fn clone(&self) -> Self {
        let mut state = self.state.lock();
        let id = if state.capture_pending_traces {
            let id = state.next_trace_id;
            state.next_trace_id.0 += 1;
            state.pending_traces.insert(id, Backtrace::new_unresolved());
            Some(id)
        } else {
            None
        };
        Self {
            id,
            awoken: self.awoken.clone(),
            thread: self.thread.clone(),
            state: self.state.clone(),
        }
    }
}

impl Drop for TracingWaker {
    fn drop(&mut self) {
        assert_correct_thread(&self.thread, &self.state);

        if let Some(id) = self.id {
            self.state.lock().pending_traces.remove(&id);
        }
    }
}

impl TracingWaker {
    fn wake(self) {
        self.wake_by_ref();
    }

    fn wake_by_ref(&self) {
        assert_correct_thread(&self.thread, &self.state);

        let mut state = self.state.lock();
        if let Some(id) = self.id {
            state.pending_traces.remove(&id);
        }
        state.unparked = true;
        drop(state);
        self.awoken.store(true, SeqCst);
        self.thread.unpark();
    }

    fn clone_raw(waker: *const ()) -> RawWaker {
        let waker = waker as *const TracingWaker;
        let waker = unsafe { &*waker };
        RawWaker::new(
            Box::into_raw(Box::new(waker.clone())) as *const (),
            &WAKER_VTABLE,
        )
    }

    fn wake_raw(waker: *const ()) {
        let waker = unsafe { Box::from_raw(waker as *mut TracingWaker) };
        waker.wake();
    }

    fn wake_by_ref_raw(waker: *const ()) {
        let waker = waker as *const TracingWaker;
        let waker = unsafe { &*waker };
        waker.wake_by_ref();
    }

    fn drop_raw(waker: *const ()) {
        let waker = unsafe { Box::from_raw(waker as *mut TracingWaker) };
        drop(waker);
    }
}

pub struct Yield(usize);

/// A wrapper around `Arc<Mutex<StdRng>>` that provides convenient methods
/// for random number generation without requiring explicit locking.
#[derive(Clone)]
pub struct SharedRng(Arc<Mutex<StdRng>>);

impl SharedRng {
    /// Lock the inner RNG for direct access. Use this when you need multiple
    /// random operations without re-locking between each one.
    pub fn lock(&self) -> MutexGuard<'_, StdRng> {
        self.0.lock()
    }

    /// Generate a random value in the given range.
    pub fn random_range<T, R>(&self, range: R) -> T
    where
        T: SampleUniform,
        R: SampleRange<T>,
    {
        self.0.lock().random_range(range)
    }

    /// Generate a random boolean with the given probability of being true.
    pub fn random_bool(&self, p: f64) -> bool {
        self.0.lock().random_bool(p)
    }

    /// Generate a random value of the given type.
    pub fn random<T>(&self) -> T
    where
        StandardUniform: Distribution<T>,
    {
        self.0.lock().random()
    }

    /// Generate a random ratio - true with probability `numerator/denominator`.
    pub fn random_ratio(&self, numerator: u32, denominator: u32) -> bool {
        self.0.lock().random_ratio(numerator, denominator)
    }
}

impl Future for Yield {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
        if self.0 == 0 {
            Poll::Ready(())
        } else {
            self.0 -= 1;
            cx.waker().wake_by_ref();
            Poll::Pending
        }
    }
}

fn exclude_wakers_from_trace(mut trace: Backtrace) -> Backtrace {
    trace.resolve();
    let mut frames: Vec<BacktraceFrame> = trace.into();
    let waker_clone_frame_ix = frames.iter().position(|frame| {
        frame.symbols().iter().any(|symbol| {
            symbol
                .name()
                .is_some_and(|name| format!("{name:#?}") == type_name_of_val(&Waker::clone))
        })
    });

    if let Some(waker_clone_frame_ix) = waker_clone_frame_ix {
        frames.drain(..waker_clone_frame_ix + 1);
    }

    Backtrace::from(frames)
}