Pause input while running an exercise

src/watch.rs

@@ -1,4 +1,4 @@
-use anyhow::{Context, Error, Result};
+use anyhow::{Error, Result};
 use notify_debouncer_mini::{
     new_debouncer,
     notify::{self, RecursiveMode},
@@ -7,7 +7,6 @@ use std::{
     io::{self, Write},
     path::Path,
     sync::mpsc::channel,
-    thread,
     time::Duration,
 };
 
@@ -16,11 +15,7 @@ use crate::{
     list,
 };
 
-use self::{
-    notify_event::NotifyEventHandler,
-    state::WatchState,
-    terminal_event::{terminal_event_handler, InputEvent},
-};
+use self::{notify_event::NotifyEventHandler, state::WatchState, terminal_event::InputEvent};
 
 mod notify_event;
 mod state;
@@ -47,7 +42,7 @@ fn run_watch(
     app_state: &mut AppState,
     notify_exercise_names: Option<&'static [&'static [u8]]>,
 ) -> Result<WatchExit> {
-    let (tx, rx) = channel();
+    let (watch_event_sender, watch_event_receiver) = channel();
 
     let mut manual_run = false;
     // Prevent dropping the guard until the end of the function.
@@ -56,7 +51,7 @@ fn run_watch(
         let mut debouncer = new_debouncer(
             Duration::from_millis(200),
             NotifyEventHandler {
-                tx: tx.clone(),
+                sender: watch_event_sender.clone(),
                 exercise_names,
             },
         )
@@ -72,16 +67,12 @@ fn run_watch(
         None
     };
 
-    let mut watch_state = WatchState::build(app_state, manual_run)?;
-
+    let mut watch_state = WatchState::build(app_state, watch_event_sender, manual_run)?;
     let mut stdout = io::stdout().lock();
+
     watch_state.run_current_exercise(&mut stdout)?;
 
-    thread::Builder::new()
-        .spawn(move || terminal_event_handler(tx, manual_run))
-        .context("Failed to spawn a thread to handle terminal events")?;
-
-    while let Ok(event) = rx.recv() {
+    while let Ok(event) = watch_event_receiver.recv() {
         match event {
             WatchEvent::Input(InputEvent::Next) => match watch_state.next_exercise(&mut stdout)? {
                 ExercisesProgress::AllDone => break,

src/watch/notify_event.rs

@@ -4,7 +4,7 @@ use std::sync::mpsc::Sender;
 use super::WatchEvent;
 
 pub struct NotifyEventHandler {
-    pub tx: Sender<WatchEvent>,
+    pub sender: Sender<WatchEvent>,
     /// Used to report which exercise was modified.
     pub exercise_names: &'static [&'static [u8]],
 }
@@ -47,6 +47,6 @@ impl notify_debouncer_mini::DebounceEventHandler for NotifyEventHandler {
 
         // An error occurs when the receiver is dropped.
         // After dropping the receiver, the debouncer guard should also be dropped.
-        let _ = self.tx.send(output_event);
+        let _ = self.sender.send(output_event);
     }
 }

src/watch/state.rs

@@ -5,7 +5,11 @@ use crossterm::{
     },
     terminal, QueueableCommand,
 };
-use std::io::{self, StdoutLock, Write};
+use std::{
+    io::{self, StdoutLock, Write},
+    sync::mpsc::Sender,
+    thread,
+};
 
 use crate::{
     app_state::{AppState, ExercisesProgress},
@@ -14,6 +18,11 @@ use crate::{
     term::progress_bar,
 };
 
+use super::{
+    terminal_event::{terminal_event_handler, InputPauseGuard},
+    WatchEvent,
+};
+
 #[derive(PartialEq, Eq)]
 enum DoneStatus {
     DoneWithSolution(String),
@@ -31,11 +40,19 @@ pub struct WatchState<'a> {
 }
 
 impl<'a> WatchState<'a> {
-    pub fn build(app_state: &'a mut AppState, manual_run: bool) -> Result<Self> {
+    pub fn build(
+        app_state: &'a mut AppState,
+        watch_event_sender: Sender<WatchEvent>,
+        manual_run: bool,
+    ) -> Result<Self> {
         let term_width = terminal::size()
             .context("Failed to get the terminal size")?
             .0;
 
+        thread::Builder::new()
+            .spawn(move || terminal_event_handler(watch_event_sender, manual_run))
+            .context("Failed to spawn a thread to handle terminal events")?;
+
         Ok(Self {
             app_state,
             output: Vec::with_capacity(OUTPUT_CAPACITY),
@@ -47,6 +64,9 @@ impl<'a> WatchState<'a> {
     }
 
     pub fn run_current_exercise(&mut self, stdout: &mut StdoutLock) -> Result<()> {
+        // Ignore any input until running the exercise is done.
+        let _input_pause_guard = InputPauseGuard::scoped_pause();
+
         self.show_hint = false;
 
         writeln!(

src/watch/terminal_event.rs

@@ -1,8 +1,32 @@
 use crossterm::event::{self, Event, KeyCode, KeyEventKind};
-use std::sync::mpsc::Sender;
+use std::sync::{
+    atomic::{AtomicBool, Ordering::Relaxed},
+    mpsc::Sender,
+};
 
 use super::WatchEvent;
 
+static INPUT_PAUSED: AtomicBool = AtomicBool::new(false);
+
+// Private unit type to force using the constructor function.
+#[must_use = "When the guard is dropped, the input is unpaused"]
+pub struct InputPauseGuard(());
+
+impl InputPauseGuard {
+    #[inline]
+    pub fn scoped_pause() -> Self {
+        INPUT_PAUSED.store(true, Relaxed);
+        Self(())
+    }
+}
+
+impl Drop for InputPauseGuard {
+    #[inline]
+    fn drop(&mut self) {
+        INPUT_PAUSED.store(false, Relaxed);
+    }
+}
+
 pub enum InputEvent {
     Run,
     Next,
@@ -11,46 +35,41 @@ pub enum InputEvent {
     Quit,
 }
 
-pub fn terminal_event_handler(tx: Sender<WatchEvent>, manual_run: bool) {
-    let last_input_event = loop {
-        let terminal_event = match event::read() {
-            Ok(v) => v,
-            Err(e) => {
-                // If `send` returns an error, then the receiver is dropped and
-                // a shutdown has been already initialized.
-                let _ = tx.send(WatchEvent::TerminalEventErr(e));
-                return;
-            }
-        };
-
-        match terminal_event {
-            Event::Key(key) => {
+pub fn terminal_event_handler(sender: Sender<WatchEvent>, manual_run: bool) {
+    let last_watch_event = loop {
+        match event::read() {
+            Ok(Event::Key(key)) => {
                 match key.kind {
                     KeyEventKind::Release | KeyEventKind::Repeat => continue,
                     KeyEventKind::Press => (),
                 }
 
+                if INPUT_PAUSED.load(Relaxed) {
+                    continue;
+                }
+
                 let input_event = match key.code {
                     KeyCode::Char('n') => InputEvent::Next,
                     KeyCode::Char('h') => InputEvent::Hint,
-                    KeyCode::Char('l') => break InputEvent::List,
-                    KeyCode::Char('q') => break InputEvent::Quit,
+                    KeyCode::Char('l') => break WatchEvent::Input(InputEvent::List),
+                    KeyCode::Char('q') => break WatchEvent::Input(InputEvent::Quit),
                     KeyCode::Char('r') if manual_run => InputEvent::Run,
                     _ => continue,
                 };
 
-                if tx.send(WatchEvent::Input(input_event)).is_err() {
+                if sender.send(WatchEvent::Input(input_event)).is_err() {
                     return;
                 }
             }
-            Event::Resize(width, _) => {
-                if tx.send(WatchEvent::TerminalResize { width }).is_err() {
+            Ok(Event::Resize(width, _)) => {
+                if sender.send(WatchEvent::TerminalResize { width }).is_err() {
                     return;
                 }
             }
-            Event::FocusGained | Event::FocusLost | Event::Mouse(_) => continue,
+            Ok(Event::FocusGained | Event::FocusLost | Event::Mouse(_)) => continue,
+            Err(e) => break WatchEvent::TerminalEventErr(e),
         }
     };
 
-    let _ = tx.send(WatchEvent::Input(last_input_event));
+    let _ = sender.send(last_watch_event);
 }