Improve event handling in the watch mode

src/main.rs

@@ -85,7 +85,8 @@ Did you already install Rust?
 Try running `cargo --version` to diagnose the problem.",
     )?;
 
-    let exercises = InfoFile::parse()?.exercises;
+    // Leaking is not a problem since the exercises are used until the end of the program.
+    let exercises = InfoFile::parse()?.exercises.leak();
 
     if matches!(args.command, Some(Subcommands::Init)) {
         init::init(&exercises).context("Initialization failed")?;
@@ -110,7 +111,7 @@ If you are just starting with Rustlings, run the command `rustlings init` to ini
 
     match args.command {
         None | Some(Subcommands::Watch) => {
-            watch::watch(&state_file, &exercises)?;
+            watch::watch(&state_file, exercises)?;
         }
         // `Init` is handled above.
         Some(Subcommands::Init) => (),

src/watch.rs

@@ -1,9 +1,11 @@
-use anyhow::Result;
-use notify_debouncer_mini::{new_debouncer, notify::RecursiveMode};
+use anyhow::{bail, Context, Result};
+use notify_debouncer_mini::{
+    new_debouncer, notify::RecursiveMode, DebounceEventResult, DebouncedEventKind,
+};
 use std::{
     io::{self, BufRead, Write},
     path::Path,
-    sync::mpsc::{channel, sync_channel},
+    sync::mpsc::{channel, Sender},
     thread,
     time::Duration,
 };
@@ -14,70 +16,130 @@ use crate::{exercise::Exercise, state_file::StateFile};
 
 use self::state::WatchState;
 
-enum Event {
+enum InputEvent {
     Hint,
     Clear,
     Quit,
+    Unrecognized,
 }
 
-pub fn watch(state_file: &StateFile, exercises: &[Exercise]) -> Result<()> {
-    let (tx, rx) = channel();
-    let mut debouncer = new_debouncer(Duration::from_secs(1), tx)?;
-    debouncer
-        .watcher()
-        .watch(Path::new("exercises"), RecursiveMode::Recursive)?;
+enum WatchEvent {
+    Input(InputEvent),
+    FileChange { exercise_ind: usize },
+    TerminalResize,
+}
 
-    let mut watch_state = WatchState::new(state_file, exercises, rx);
+struct DebouceEventHandler {
+    tx: Sender<WatchEvent>,
+    exercises: &'static [Exercise],
+}
 
-    watch_state.run_exercise()?;
-    watch_state.render()?;
+impl notify_debouncer_mini::DebounceEventHandler for DebouceEventHandler {
+    fn handle_event(&mut self, event: DebounceEventResult) {
+        let Ok(event) = event else {
+            // TODO
+            return;
+        };
 
-    let (tx, rx) = sync_channel(0);
-    thread::spawn(move || {
+        let Some(exercise_ind) = event
+            .iter()
+            .filter_map(|event| {
+                if event.kind != DebouncedEventKind::Any
+                    || !event.path.extension().is_some_and(|ext| ext == "rs")
+                {
+                    return None;
+                }
+
+                self.exercises
+                    .iter()
+                    .position(|exercise| event.path.ends_with(&exercise.path))
+            })
+            .min()
+        else {
+            return;
+        };
+
+        self.tx.send(WatchEvent::FileChange { exercise_ind });
+    }
+}
+
+fn input_handler(tx: Sender<WatchEvent>) -> Result<()> {
     let mut stdin = io::stdin().lock();
     let mut stdin_buf = String::with_capacity(8);
 
     loop {
-            stdin.read_line(&mut stdin_buf).unwrap();
+        stdin
+            .read_line(&mut stdin_buf)
+            .context("Failed to read the user's input from stdin")?;
 
         let event = match stdin_buf.trim() {
-                "h" | "hint" => Some(Event::Hint),
-                "c" | "clear" => Some(Event::Clear),
-                "q" | "quit" => Some(Event::Quit),
-                _ => None,
+            "h" | "hint" => InputEvent::Hint,
+            "c" | "clear" => InputEvent::Clear,
+            "q" | "quit" => InputEvent::Quit,
+            _ => InputEvent::Unrecognized,
         };
 
         stdin_buf.clear();
 
-            if tx.send(event).is_err() {
-                break;
-            };
+        if tx.send(WatchEvent::Input(event)).is_err() {
+            return Ok(());
         }
-    });
+    }
+}
 
-    loop {
-        watch_state.try_recv_event()?;
+pub fn watch(state_file: &StateFile, exercises: &'static [Exercise]) -> Result<()> {
+    let (tx, rx) = channel();
+    let mut debouncer = new_debouncer(
+        Duration::from_secs(1),
+        DebouceEventHandler {
+            tx: tx.clone(),
+            exercises,
+        },
+    )?;
+    debouncer
+        .watcher()
+        .watch(Path::new("exercises"), RecursiveMode::Recursive)?;
 
-        if let Ok(event) = rx.try_recv() {
+    let mut watch_state = WatchState::new(state_file, exercises);
+
+    // TODO: bool
+    watch_state.run_exercise()?;
+    watch_state.render()?;
+
+    let input_thread = thread::spawn(move || input_handler(tx));
+
+    while let Ok(event) = rx.recv() {
         match event {
-                Some(Event::Hint) => {
+            WatchEvent::Input(InputEvent::Hint) => {
                 watch_state.show_hint()?;
             }
-                Some(Event::Clear) => {
+            WatchEvent::Input(InputEvent::Clear) | WatchEvent::TerminalResize => {
                 watch_state.render()?;
             }
-                Some(Event::Quit) => break,
-                None => {
+            WatchEvent::Input(InputEvent::Quit) => break,
+            WatchEvent::Input(InputEvent::Unrecognized) => {
                 watch_state.handle_invalid_cmd()?;
             }
+            WatchEvent::FileChange { exercise_ind } => {
+                // TODO: bool
+                watch_state.run_exercise_with_ind(exercise_ind)?;
+                watch_state.render()?;
             }
         }
     }
 
+    // Drop the receiver for the sender threads to exit.
+    drop(rx);
+
     watch_state.into_writer().write_all(b"
 We hope you're enjoying learning Rust!
 If you want to continue working on the exercises at a later point, you can simply run `rustlings` again.
 ")?;
 
+    match input_thread.join() {
+        Ok(res) => res?,
+        Err(_) => bail!("The input thread panicked"),
+    }
+
     Ok(())
 }

src/watch/state.rs

@@ -1,26 +1,23 @@
-use anyhow::Result;
+use anyhow::{Context, Result};
 use crossterm::{
     style::{Attribute, ContentStyle, Stylize},
-    terminal::{Clear, ClearType},
+    terminal::{size, Clear, ClearType},
     ExecutableCommand,
 };
-use notify_debouncer_mini::{DebounceEventResult, DebouncedEventKind};
 use std::{
     fmt::Write as _,
     io::{self, StdoutLock, Write as _},
-    sync::mpsc::Receiver,
-    time::Duration,
 };
 
 use crate::{
     exercise::{Exercise, State},
+    progress_bar::progress_bar,
     state_file::StateFile,
 };
 
 pub struct WatchState<'a> {
     writer: StdoutLock<'a>,
-    rx: Receiver<DebounceEventResult>,
-    exercises: &'a [Exercise],
+    exercises: &'static [Exercise],
     exercise: &'a Exercise,
     current_exercise_ind: usize,
     stdout: Option<Vec<u8>>,
@@ -30,11 +27,7 @@ pub struct WatchState<'a> {
 }
 
 impl<'a> WatchState<'a> {
-    pub fn new(
-        state_file: &StateFile,
-        exercises: &'a [Exercise],
-        rx: Receiver<DebounceEventResult>,
-    ) -> Self {
+    pub fn new(state_file: &StateFile, exercises: &'static [Exercise]) -> Self {
         let current_exercise_ind = state_file.next_exercise_ind();
         let exercise = &exercises[current_exercise_ind];
 
@@ -50,7 +43,6 @@ impl<'a> WatchState<'a> {
 
         Self {
             writer,
-            rx,
             exercises,
             exercise,
             current_exercise_ind,
@@ -114,41 +106,14 @@ You can keep working on this exercise or jump into the next one by removing the
         Ok(true)
     }
 
-    pub fn try_recv_event(&mut self) -> Result<()> {
-        let Ok(events) = self.rx.recv_timeout(Duration::from_millis(100)) else {
-            return Ok(());
-        };
+    pub fn run_exercise_with_ind(&mut self, exercise_ind: usize) -> Result<bool> {
+        self.exercise = self
+            .exercises
+            .get(exercise_ind)
+            .context("Invalid exercise index")?;
+        self.current_exercise_ind = exercise_ind;
 
-        if let Some(current_exercise_ind) = events?
-            .iter()
-            .filter_map(|event| {
-                if event.kind != DebouncedEventKind::Any
-                    || !event.path.extension().is_some_and(|ext| ext == "rs")
-                {
-                    return None;
-                }
-
-                self.exercises
-                    .iter()
-                    .position(|exercise| event.path.ends_with(&exercise.path))
-            })
-            .min()
-        {
-            self.current_exercise_ind = current_exercise_ind;
-        } else {
-            return Ok(());
-        };
-
-        while self.current_exercise_ind < self.exercises.len() {
-            self.exercise = &self.exercises[self.current_exercise_ind];
-            if !self.run_exercise()? {
-                break;
-            }
-
-            self.current_exercise_ind += 1;
-        }
-
-        Ok(())
+        self.run_exercise()
     }
 
     pub fn show_prompt(&mut self) -> io::Result<()> {
@@ -156,7 +121,7 @@ You can keep working on this exercise or jump into the next one by removing the
         self.writer.flush()
     }
 
-    pub fn render(&mut self) -> io::Result<()> {
+    pub fn render(&mut self) -> Result<()> {
         self.writer.execute(Clear(ClearType::All))?;
 
         if let Some(stdout) = &self.stdout {
@@ -171,7 +136,17 @@ You can keep working on this exercise or jump into the next one by removing the
             self.writer.write_all(message.as_bytes())?;
         }
 
-        self.show_prompt()
+        let line_width = size()?.0;
+        let progress_bar = progress_bar(
+            self.current_exercise_ind as u16,
+            self.exercises.len() as u16,
+            line_width,
+        )?;
+        self.writer.write_all(progress_bar.as_bytes())?;
+
+        self.show_prompt()?;
+
+        Ok(())
     }
 
     pub fn show_hint(&mut self) -> io::Result<()> {