1use crate::{PlatformDispatcher, Priority, RunnableVariant};
  2use scheduler::Instant;
  3use scheduler::{Clock, Scheduler, SessionId, TestScheduler, TestSchedulerConfig, Yield};
  4use std::{
  5    sync::{
  6        Arc,
  7        atomic::{AtomicUsize, Ordering},
  8    },
  9    time::Duration,
 10};
 11
 12/// TestDispatcher provides deterministic async execution for tests.
 13///
 14/// This implementation delegates task scheduling to the scheduler crate's `TestScheduler`.
 15/// Access the scheduler directly via `scheduler()` for clock, rng, and parking control.
 16#[doc(hidden)]
 17pub struct TestDispatcher {
 18    session_id: SessionId,
 19    scheduler: Arc<TestScheduler>,
 20    num_cpus_override: Arc<AtomicUsize>,
 21}
 22
 23impl TestDispatcher {
 24    pub fn new(seed: u64) -> Self {
 25        let scheduler = Arc::new(TestScheduler::new(TestSchedulerConfig {
 26            seed,
 27            randomize_order: true,
 28            allow_parking: false,
 29            capture_pending_traces: std::env::var("PENDING_TRACES")
 30                .map_or(false, |var| var == "1" || var == "true"),
 31            timeout_ticks: 0..=1000,
 32        }));
 33
 34        let session_id = scheduler.allocate_session_id();
 35
 36        TestDispatcher {
 37            session_id,
 38            scheduler,
 39            num_cpus_override: Arc::new(AtomicUsize::new(0)),
 40        }
 41    }
 42
 43    pub fn scheduler(&self) -> &Arc<TestScheduler> {
 44        &self.scheduler
 45    }
 46
 47    pub fn session_id(&self) -> SessionId {
 48        self.session_id
 49    }
 50
 51    pub fn advance_clock(&self, by: Duration) {
 52        self.scheduler.advance_clock(by);
 53    }
 54
 55    pub fn advance_clock_to_next_timer(&self) -> bool {
 56        self.scheduler.advance_clock_to_next_timer()
 57    }
 58
 59    pub fn simulate_random_delay(&self) -> Yield {
 60        self.scheduler.yield_random()
 61    }
 62
 63    pub fn tick(&self, background_only: bool) -> bool {
 64        if background_only {
 65            self.scheduler.tick_background_only()
 66        } else {
 67            self.scheduler.tick()
 68        }
 69    }
 70
 71    pub fn run_until_parked(&self) {
 72        while self.tick(false) {}
 73    }
 74
 75    /// Override the value returned by `BackgroundExecutor::num_cpus()` in tests.
 76    /// A value of 0 means no override (the default of 4 is used).
 77    pub fn set_num_cpus(&self, count: usize) {
 78        self.num_cpus_override.store(count, Ordering::SeqCst);
 79    }
 80
 81    /// Returns the overridden CPU count, or `None` if no override is set.
 82    pub fn num_cpus_override(&self) -> Option<usize> {
 83        match self.num_cpus_override.load(Ordering::SeqCst) {
 84            0 => None,
 85            n => Some(n),
 86        }
 87    }
 88}
 89
 90impl Clone for TestDispatcher {
 91    fn clone(&self) -> Self {
 92        let session_id = self.scheduler.allocate_session_id();
 93        Self {
 94            session_id,
 95            scheduler: self.scheduler.clone(),
 96            num_cpus_override: self.num_cpus_override.clone(),
 97        }
 98    }
 99}
100
101impl PlatformDispatcher for TestDispatcher {
102    fn get_all_timings(&self) -> Vec<crate::ThreadTaskTimings> {
103        Vec::new()
104    }
105
106    fn get_current_thread_timings(&self) -> crate::ThreadTaskTimings {
107        crate::ThreadTaskTimings {
108            thread_name: None,
109            thread_id: std::thread::current().id(),
110            timings: Vec::new(),
111            total_pushed: 0,
112        }
113    }
114
115    fn is_main_thread(&self) -> bool {
116        self.scheduler.is_main_thread()
117    }
118
119    fn now(&self) -> Instant {
120        self.scheduler.clock().now()
121    }
122
123    fn dispatch(&self, runnable: RunnableVariant, priority: Priority) {
124        self.scheduler
125            .schedule_background_with_priority(runnable, priority);
126    }
127
128    fn dispatch_on_main_thread(&self, runnable: RunnableVariant, _priority: Priority) {
129        self.scheduler
130            .schedule_foreground(self.session_id, runnable);
131    }
132
133    fn dispatch_after(&self, _duration: Duration, _runnable: RunnableVariant) {
134        panic!(
135            "dispatch_after should not be called in tests. \
136            Use BackgroundExecutor::timer() which uses the scheduler's native timer."
137        );
138    }
139
140    fn as_test(&self) -> Option<&TestDispatcher> {
141        Some(self)
142    }
143
144    fn spawn_realtime(&self, f: Box<dyn FnOnce() + Send>) {
145        std::thread::spawn(move || {
146            f();
147        });
148    }
149}