feat: Add "quit" command to rustlings watch

closes: #842

src/main.rs

@@ -10,7 +10,8 @@ use std::fs;
 use std::io::{self, prelude::*};
 use std::path::Path;
 use std::process::{Command, Stdio};
-use std::sync::mpsc::channel;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::mpsc::{RecvTimeoutError, channel};
 use std::sync::{Arc, Mutex};
 use std::thread;
 use std::time::Duration;
@@ -217,7 +218,8 @@ fn main() {
         }
 
         Subcommands::Watch(_subargs) => {
-            if let Err(e) = watch(&exercises, verbose) {
+            match watch(&exercises, verbose) {
+                Err(e) => {
                     println!(
                         "Error: Could not watch your progress. Error message was {:?}.",
                         e
@@ -225,6 +227,7 @@ fn main() {
                     println!("Most likely you've run out of disk space or your 'inotify limit' has been reached.");
                     std::process::exit(1);
                 }
+                Ok(WatchStatus::Finished) => {
                     println!(
                         "{emoji} All exercises completed! {emoji}",
                         emoji = Emoji("🎉", "★")
@@ -259,10 +262,16 @@ fn main() {
                     println!("Before reporting an issue or contributing, please read our guidelines:");
                     println!("https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md");
                 }
+                Ok(WatchStatus::Unfinished) => {
+                    println!("We hope you're enjoying learning about Rust!");
+                    println!("If you want to continue working on the exercises at a later point, you can simply run `rustlings watch` again");
+                }
+            }
+        }
     }
 }
 
-fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>) {
+fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>, should_quit: Arc<AtomicBool>) {
     let failed_exercise_hint = Arc::clone(failed_exercise_hint);
     println!("Welcome to watch mode! You can type 'help' to get an overview of the commands you can use here.");
     thread::spawn(move || loop {
@@ -270,15 +279,15 @@ fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>) {
         match io::stdin().read_line(&mut input) {
             Ok(_) => {
                 let input = input.trim();
-                if input.eq("hint") {
+                if input == "hint" {
                     if let Some(hint) = &*failed_exercise_hint.lock().unwrap() {
                         println!("{}", hint);
                     }
-                } else if input.eq("clear") {
+                } else if input == "clear" {
                     println!("\x1B[2J\x1B[1;1H");
                 } else if input.eq("quit") {
+                    should_quit.store(true, Ordering::SeqCst);
                     println!("Bye!");
-                    std::process::exit(0);
                 } else if input.eq("help") {
                     println!("Commands available to you in watch mode:");
                     println!("  hint  - prints the current exercise's hint");
@@ -318,7 +327,12 @@ fn find_exercise<'a>(name: &str, exercises: &'a [Exercise]) -> &'a Exercise {
     }
 }
 
-fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
+enum WatchStatus {
+    Finished,
+    Unfinished,
+}
+
+fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<WatchStatus> {
     /* Clears the terminal with an ANSI escape code.
     Works in UNIX and newer Windows terminals. */
     fn clear_screen() {
@@ -326,6 +340,7 @@ fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
     }
 
     let (tx, rx) = channel();
+    let should_quit = Arc::new(AtomicBool::new(false));
 
     let mut watcher: RecommendedWatcher = Watcher::new(tx, Duration::from_secs(2))?;
     watcher.watch(Path::new("./exercises"), RecursiveMode::Recursive)?;
@@ -334,12 +349,12 @@ fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
 
     let to_owned_hint = |t: &Exercise| t.hint.to_owned();
     let failed_exercise_hint = match verify(exercises.iter(), verbose) {
-        Ok(_) => return Ok(()),
+        Ok(_) => return Ok(WatchStatus::Finished),
         Err(exercise) => Arc::new(Mutex::new(Some(to_owned_hint(exercise)))),
     };
-    spawn_watch_shell(&failed_exercise_hint);
+    spawn_watch_shell(&failed_exercise_hint, Arc::clone(&should_quit));
     loop {
-        match rx.recv() {
+        match rx.recv_timeout(Duration::from_secs(1)) {
             Ok(event) => match event {
                 DebouncedEvent::Create(b) | DebouncedEvent::Chmod(b) | DebouncedEvent::Write(b) => {
                     if b.extension() == Some(OsStr::new("rs")) && b.exists() {
@@ -355,7 +370,7 @@ fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
                             );
                         clear_screen();
                         match verify(pending_exercises, verbose) {
-                            Ok(_) => return Ok(()),
+                            Ok(_) => return Ok(WatchStatus::Finished),
                             Err(exercise) => {
                                 let mut failed_exercise_hint = failed_exercise_hint.lock().unwrap();
                                 *failed_exercise_hint = Some(to_owned_hint(exercise));
@@ -365,8 +380,15 @@ fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
                 }
                 _ => {}
             },
+            Err(RecvTimeoutError::Timeout) => {
+                // the timeout expired, just check the `should_quit` variable below then loop again
+            }
             Err(e) => println!("watch error: {:?}", e),
         }
+        // Check if we need to exit
+        if should_quit.load(Ordering::SeqCst) {
+            return Ok(WatchStatus::Unfinished);
+        }
     }
 }