Improve event handling in the watch mode

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<()> {
+enum WatchEvent {
+    Input(InputEvent),
+    FileChange { exercise_ind: usize },
+    TerminalResize,
+}
+
+struct DebouceEventHandler {
+    tx: Sender<WatchEvent>,
+    exercises: &'static [Exercise],
+}
+
+impl notify_debouncer_mini::DebounceEventHandler for DebouceEventHandler {
+    fn handle_event(&mut self, event: DebounceEventResult) {
+        let Ok(event) = event else {
+            // TODO
+            return;
+        };
+
+        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)
+            .context("Failed to read the user's input from stdin")?;
+
+        let event = match stdin_buf.trim() {
+            "h" | "hint" => InputEvent::Hint,
+            "c" | "clear" => InputEvent::Clear,
+            "q" | "quit" => InputEvent::Quit,
+            _ => InputEvent::Unrecognized,
+        };
+
+        stdin_buf.clear();
+
+        if tx.send(WatchEvent::Input(event)).is_err() {
+            return Ok(());
+        }
+    }
+}
+
+pub fn watch(state_file: &StateFile, exercises: &'static [Exercise]) -> Result<()> {
     let (tx, rx) = channel();
-    let mut debouncer = new_debouncer(Duration::from_secs(1), tx)?;
+    let mut debouncer = new_debouncer(
+        Duration::from_secs(1),
+        DebouceEventHandler {
+            tx: tx.clone(),
+            exercises,
+        },
+    )?;
     debouncer
         .watcher()
         .watch(Path::new("exercises"), RecursiveMode::Recursive)?;
 
-    let mut watch_state = WatchState::new(state_file, exercises, rx);
+    let mut watch_state = WatchState::new(state_file, exercises);
 
+    // TODO: bool
     watch_state.run_exercise()?;
     watch_state.render()?;
 
-    let (tx, rx) = sync_channel(0);
-    thread::spawn(move || {
-        let mut stdin = io::stdin().lock();
-        let mut stdin_buf = String::with_capacity(8);
+    let input_thread = thread::spawn(move || input_handler(tx));
 
-        loop {
-            stdin.read_line(&mut stdin_buf).unwrap();
-
-            let event = match stdin_buf.trim() {
-                "h" | "hint" => Some(Event::Hint),
-                "c" | "clear" => Some(Event::Clear),
-                "q" | "quit" => Some(Event::Quit),
-                _ => None,
-            };
-
-            stdin_buf.clear();
-
-            if tx.send(event).is_err() {
-                break;
-            };
-        }
-    });
-
-    loop {
-        watch_state.try_recv_event()?;
-
-        if let Ok(event) = rx.try_recv() {
-            match event {
-                Some(Event::Hint) => {
-                    watch_state.show_hint()?;
-                }
-                Some(Event::Clear) => {
-                    watch_state.render()?;
-                }
-                Some(Event::Quit) => break,
-                None => {
-                    watch_state.handle_invalid_cmd()?;
-                }
+    while let Ok(event) = rx.recv() {
+        match event {
+            WatchEvent::Input(InputEvent::Hint) => {
+                watch_state.show_hint()?;
+            }
+            WatchEvent::Input(InputEvent::Clear) | WatchEvent::TerminalResize => {
+                watch_state.render()?;
+            }
+            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(())
 }