1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

use crate::{
    rt::sleep::{AsyncSleep, Sleep},
    test_util::ManualTimeSource,
};
use std::time::{Duration, SystemTime};
use std::{
    collections::VecDeque,
    sync::{Arc, Mutex},
};
use tokio::sync::oneshot;
use tokio::sync::Barrier;
use tokio::time::timeout;

/// A sleep implementation where calls to [`AsyncSleep::sleep`] block until [`SleepGate::expect_sleep`] is called
///
/// Create a [`ControlledSleep`] with [`controlled_time_and_sleep`]
#[derive(Debug, Clone)]
pub struct ControlledSleep {
    barrier: Arc<Barrier>,
    log: Arc<Mutex<Vec<Duration>>>,
    duration: Arc<Mutex<VecDeque<Duration>>>,
    advance_guard: Arc<Mutex<Option<oneshot::Sender<()>>>>,
}

impl ControlledSleep {
    fn new(log: Arc<Mutex<Vec<Duration>>>) -> (ControlledSleep, SleepGate) {
        let gate = Arc::new(Barrier::new(2));
        let pending = Arc::new(Mutex::new(VecDeque::new()));
        let advance_guard: Arc<Mutex<Option<oneshot::Sender<()>>>> = Default::default();
        (
            ControlledSleep {
                barrier: gate.clone(),
                log,
                duration: pending.clone(),
                advance_guard: advance_guard.clone(),
            },
            SleepGate {
                gate,
                pending,
                advance_guard,
            },
        )
    }
}

/// Guard returned from [`SleepGate::expect_sleep`]
///
/// # Examples
/// ```rust
/// # use std::sync::Arc;
/// use std::sync::atomic::{AtomicUsize, Ordering};
/// # async {
/// use std::time::{Duration, UNIX_EPOCH};
/// use aws_smithy_async::rt::sleep::AsyncSleep;
/// use aws_smithy_async::test_util::controlled_time_and_sleep;
/// let (time, sleep, mut gate) = controlled_time_and_sleep(UNIX_EPOCH);
/// let progress = Arc::new(AtomicUsize::new(0));
/// let task_progress = progress.clone();
/// let task = tokio::spawn(async move {
///     let progress = task_progress;
///     progress.store(1, Ordering::Release);
///     sleep.sleep(Duration::from_secs(1)).await;
///     progress.store(2, Ordering::Release);
///     sleep.sleep(Duration::from_secs(2)).await;
/// });
/// while progress.load(Ordering::Acquire) != 1 {}
/// let guard = gate.expect_sleep().await;
/// assert_eq!(guard.duration(), Duration::from_secs(1));
/// assert_eq!(progress.load(Ordering::Acquire), 1);
/// guard.allow_progress();
///
/// let guard = gate.expect_sleep().await;
/// assert_eq!(progress.load(Ordering::Acquire), 2);
/// assert_eq!(task.is_finished(), false);
/// guard.allow_progress();
/// task.await.expect("successful completion");
/// # };
/// ```
#[allow(dead_code)] // unused fields retained for their `Drop` impls
pub struct CapturedSleep<'a>(oneshot::Sender<()>, &'a SleepGate, Duration);
impl CapturedSleep<'_> {
    /// Allow the calling code to advance past the call to [`AsyncSleep::sleep`]
    ///
    /// In order to facilitate testing with no flakiness, the future returned by the call to `sleep`
    /// will not resolve until [`CapturedSleep`] is dropped or this method is called.
    ///
    /// ```rust
    /// use std::time::Duration;
    /// use aws_smithy_async::rt::sleep::AsyncSleep;
    /// async fn do_something(sleep: &dyn AsyncSleep) {
    ///   println!("before sleep");
    ///   sleep.sleep(Duration::from_secs(1)).await;
    ///   println!("after sleep");
    /// }
    /// ```
    ///
    /// To be specific, when `do_something` is called, the code will advance to `sleep.sleep`.
    /// When [`SleepGate::expect_sleep`] is called, the 1 second sleep will be captured, but `after sleep`
    /// WILL NOT be printed, until `allow_progress` is called.
    pub fn allow_progress(self) {
        drop(self)
    }

    /// Duration in the call to [`AsyncSleep::sleep`]
    pub fn duration(&self) -> Duration {
        self.2
    }
}

impl AsRef<Duration> for CapturedSleep<'_> {
    fn as_ref(&self) -> &Duration {
        &self.2
    }
}

/// Gate that allows [`ControlledSleep`] to advance.
///
/// See [`controlled_time_and_sleep`] for more details
pub struct SleepGate {
    gate: Arc<Barrier>,
    pending: Arc<Mutex<VecDeque<Duration>>>,
    advance_guard: Arc<Mutex<Option<oneshot::Sender<()>>>>,
}

impl SleepGate {
    /// Expect the time source to sleep
    ///
    /// This returns the duration that was slept and a [`CapturedSleep`]. The drop guard is used
    /// to precisely control
    pub async fn expect_sleep(&mut self) -> CapturedSleep<'_> {
        timeout(Duration::from_secs(1), self.gate.wait())
            .await
            .expect("timeout");
        let dur = self
            .pending
            .lock()
            .unwrap()
            .pop_front()
            .unwrap_or(Duration::from_secs(123456));
        let guard = CapturedSleep(
            self.advance_guard.lock().unwrap().take().unwrap(),
            self,
            dur,
        );
        guard
    }

    /// Skips any sleep that may be queued up, returning its duration
    pub async fn skip_sleep(&mut self) -> Option<Duration> {
        if timeout(Duration::from_millis(1), self.gate.wait())
            .await
            .is_ok()
        {
            let _ = self.advance_guard.lock().unwrap().take();
            self.pending.lock().unwrap().pop_front()
        } else {
            None
        }
    }
}

impl AsyncSleep for ControlledSleep {
    fn sleep(&self, duration: Duration) -> Sleep {
        let barrier = self.barrier.clone();
        let log = self.log.clone();
        let pending = self.duration.clone();
        let drop_guard = self.advance_guard.clone();
        Sleep::new(async move {
            // 1. write the duration into the shared mutex
            pending.lock().unwrap().push_back(duration);
            let (tx, rx) = oneshot::channel();
            *drop_guard.lock().unwrap() = Some(tx);
            // 2. first wait on the barrier—this is how we wait for an invocation of `expect_sleep`
            barrier.wait().await;
            log.lock().unwrap().push(duration);
            let _ = rx.await;
        })
    }
}

/// Returns a trio of tools to test interactions with time
///
/// 1. [`ManualTimeSource`] which starts at a specific time and only advances when `sleep` is called.
/// It MUST be paired with [`ControlledSleep`] in order to function.
pub fn controlled_time_and_sleep(
    start_time: SystemTime,
) -> (ManualTimeSource, ControlledSleep, SleepGate) {
    let log = Arc::new(Mutex::new(vec![]));
    let (sleep, gate) = ControlledSleep::new(log.clone());
    (ManualTimeSource { start_time, log }, sleep, gate)
}

#[cfg(test)]
mod test {
    use crate::rt::sleep::AsyncSleep;
    use crate::test_util::controlled_time_and_sleep;
    use crate::time::TimeSource;
    use std::sync::atomic::{AtomicUsize, Ordering};
    use std::sync::Arc;
    use std::time::{Duration, UNIX_EPOCH};
    use tokio::task::yield_now;
    use tokio::time::timeout;

    #[tokio::test]
    async fn test_sleep_gate() {
        let start = UNIX_EPOCH;
        let (time, sleep, mut gate) = controlled_time_and_sleep(UNIX_EPOCH);
        let progress = Arc::new(AtomicUsize::new(0));
        let task_progress = progress.clone();
        let task = tokio::spawn(async move {
            assert_eq!(time.now(), start);
            let progress = task_progress;
            progress.store(1, Ordering::Release);
            sleep.sleep(Duration::from_secs(1)).await;
            assert_eq!(time.now(), start + Duration::from_secs(1));
            progress.store(2, Ordering::Release);
            sleep.sleep(Duration::from_secs(2)).await;
            assert_eq!(time.now(), start + Duration::from_secs(3));
        });
        while progress.load(Ordering::Acquire) != 1 {
            yield_now().await
        }
        let guard = gate.expect_sleep().await;
        assert_eq!(guard.duration(), Duration::from_secs(1));
        assert_eq!(progress.load(Ordering::Acquire), 1);
        guard.allow_progress();

        let guard = gate.expect_sleep().await;
        assert_eq!(progress.load(Ordering::Acquire), 2);
        assert!(!task.is_finished(), "task should not be finished");
        guard.allow_progress();
        timeout(Duration::from_secs(1), task)
            .await
            .expect("no timeout")
            .expect("successful completion");
    }

    #[tokio::test]
    async fn sleep_gate_multiple_sleeps() {
        let (time, sleep, mut gate) = controlled_time_and_sleep(UNIX_EPOCH);
        let one = sleep.sleep(Duration::from_secs(1));
        let two = sleep.sleep(Duration::from_secs(2));
        let three = sleep.sleep(Duration::from_secs(3));

        let spawn = tokio::spawn(async move {
            let _ = (one.await, two.await, three.await);
        });

        assert_eq!(Duration::from_secs(1), gate.expect_sleep().await.duration());
        gate.skip_sleep().await;
        assert_eq!(Duration::from_secs(3), gate.expect_sleep().await.duration());

        let _ = spawn.await;

        assert_eq!(UNIX_EPOCH + Duration::from_secs(6), time.now());
    }

    #[tokio::test]
    async fn sleep_gate_skipping_a_sleep_doesnt_blow_up_if_no_sleep() {
        let (time, sleep, mut gate) = controlled_time_and_sleep(UNIX_EPOCH);

        let some_sleep = sleep.sleep(Duration::from_secs(1));
        let spawn = tokio::spawn(async move {
            let _ = some_sleep.await;
        });

        assert_eq!(Some(Duration::from_secs(1)), gate.skip_sleep().await);
        assert_eq!(None, gate.skip_sleep().await);

        let _ = spawn.await;

        assert_eq!(UNIX_EPOCH + Duration::from_secs(1), time.now());
    }
}