From d05f9b3b1eb90543f3b725f4a9c10eec58747310 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20V=C3=ADt?= <radekvitr@gmail.com>
Date: Wed, 16 Sep 2020 18:14:33 +0200
Subject: [PATCH] Make the sleep command respond to Ctrl+C (#2550)

---
 crates/nu-cli/src/commands/sleep.rs | 107 +++++++++++++++++++++++++---
 1 file changed, 98 insertions(+), 9 deletions(-)

diff --git a/crates/nu-cli/src/commands/sleep.rs b/crates/nu-cli/src/commands/sleep.rs
index e69f149f90..bd9ba31d1f 100644
--- a/crates/nu-cli/src/commands/sleep.rs
+++ b/crates/nu-cli/src/commands/sleep.rs
@@ -4,8 +4,17 @@ use crate::prelude::*;
 use nu_errors::ShellError;
 use nu_protocol::{Signature, SyntaxShape};
 use nu_source::Tagged;
+use parking_lot::Mutex;
+use std::{
+    future::Future,
+    pin::Pin,
+    sync::atomic::Ordering,
+    task::{Poll, Waker},
+    thread,
+    time::Duration,
+};
 
-use std::{thread, time};
+const CTRL_C_CHECK_INTERVAL: Duration = Duration::from_millis(100);
 
 pub struct Sleep;
 
@@ -36,7 +45,15 @@ impl WholeStreamCommand for Sleep {
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        sleep(args, registry).await
+        let registry = registry.clone();
+        let ctrl_c = args.ctrl_c().clone();
+
+        let (SleepArgs { dur, rest }, ..) = args.process(&registry).await?;
+
+        let total_dur = dur.item + rest.iter().map(|val| val.item).sum::<u64>();
+        let total_dur = Duration::from_nanos(total_dur);
+
+        SleepFuture::new(total_dur, ctrl_c).await
     }
 
     fn examples(&self) -> Vec<Example> {
@@ -55,16 +72,88 @@ impl WholeStreamCommand for Sleep {
     }
 }
 
-async fn sleep(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let registry = registry.clone();
+struct SleepFuture {
+    shared_state: Arc<Mutex<SharedState>>,
+}
 
-    let (SleepArgs { dur, rest }, ..) = args.process(&registry).await?;
+impl SleepFuture {
+    /// Create a new `SleepFuture` which will complete after the provided
+    /// timeout and check for Ctrl+C periodically.
+    pub fn new(duration: Duration, ctrl_c: Arc<AtomicBool>) -> Self {
+        let shared_state = Arc::new(Mutex::new(SharedState {
+            done: false,
+            waker: None,
+        }));
 
-    let total_dur = dur.item + rest.iter().map(|val| val.item).sum::<u64>();
-    let total_dur = time::Duration::from_nanos(total_dur);
-    thread::sleep(total_dur);
+        // Spawn the main sleep thread
+        let thread_shared_state = shared_state.clone();
+        thread::spawn(move || {
+            thread::sleep(duration);
+            let mut shared_state = thread_shared_state.lock();
+            // Signal that the timer has completed and wake up the last
+            // task on which the future was polled, if one exists.
+            if !shared_state.done {
+                shared_state.done = true;
+                if let Some(waker) = shared_state.waker.take() {
+                    waker.wake()
+                }
+            }
+        });
 
-    Ok(OutputStream::empty())
+        // Spawn the Ctrl+C-watching polling thread
+        let thread_shared_state = shared_state.clone();
+        thread::spawn(move || {
+            loop {
+                {
+                    let mut shared_state = thread_shared_state.lock();
+                    // exit if the main thread is done
+                    if shared_state.done {
+                        return;
+                    }
+                    // finish the future prematurely if Ctrl+C has been pressed
+                    if ctrl_c.load(Ordering::SeqCst) {
+                        shared_state.done = true;
+                        if let Some(waker) = shared_state.waker.take() {
+                            waker.wake()
+                        }
+                        return;
+                    }
+                }
+                // sleep for a short time
+                thread::sleep(CTRL_C_CHECK_INTERVAL);
+            }
+        });
+
+        SleepFuture { shared_state }
+    }
+}
+
+struct SharedState {
+    done: bool,
+    waker: Option<Waker>,
+}
+
+impl Future for SleepFuture {
+    type Output = Result<OutputStream, ShellError>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
+        // Look at the shared state to see if the timer has already completed.
+        let mut shared_state = self.shared_state.lock();
+        if shared_state.done {
+            Poll::Ready(Ok(OutputStream::empty()))
+        } else {
+            // Set the waker if necessary
+            if shared_state
+                .waker
+                .as_ref()
+                .map(|waker| !waker.will_wake(&cx.waker()))
+                .unwrap_or(true)
+            {
+                shared_state.waker = Some(cx.waker().clone());
+            }
+            Poll::Pending
+        }
+    }
 }
 
 #[cfg(test)]