implement more robust file watcher

src/filewatcher.rs

@@ -0,0 +1,70 @@
+use anyhow::{bail, Result};
+use notify::{DebouncedEvent, Watcher, RecommendedWatcher};
+use std::{
+    collections::BTreeSet,
+    path::{Path, PathBuf},
+    sync::mpsc,
+    time::Duration,
+};
+
+pub struct FileWatcher {
+    _watcher: RecommendedWatcher,
+    watched_files: BTreeSet<PathBuf>,
+    rx: mpsc::Receiver<DebouncedEvent>,
+}
+
+pub struct FileWatcherBuilder(BTreeSet<PathBuf>);
+
+impl FileWatcher {
+    pub fn builder() -> FileWatcherBuilder {
+        FileWatcherBuilder(BTreeSet::new())
+    }
+
+    pub fn poll_changed_file(&self) -> Result<Option<PathBuf>> {
+        let event = self.rx.try_recv();
+        match event {
+            Ok(DebouncedEvent::Create(path) | DebouncedEvent::Write(path)) => {
+                let handle = same_file::Handle::from_path(&path)?;
+                for file in &self.watched_files {
+                    if handle == same_file::Handle::from_path(file)? {
+                        return Ok(Some(path));
+                    }
+                }
+            }
+            Err(mpsc::TryRecvError::Disconnected) => bail!("File watcher disconnected"),
+            _ => (),
+        }
+
+        Ok(None)
+    }
+}
+
+impl FileWatcherBuilder {
+    pub fn add_file<P: Into<PathBuf>>(&mut self, path: P) -> &mut Self {
+        self.0.insert(path.into());
+        self
+    }
+
+    pub fn build(self) -> Result<FileWatcher> {
+        let mut directories: BTreeSet<&Path> = BTreeSet::new();
+
+        for file in &self.0 {
+            if let Some(directory) = file.parent() {
+                directories.insert(directory);
+            }
+        }
+
+        let (tx, rx) = mpsc::channel();
+        let mut watcher = notify::watcher(tx, Duration::from_millis(100))?;
+
+        for directory in directories {
+            watcher.watch(directory, notify::RecursiveMode::NonRecursive)?;
+        }
+
+        Ok(FileWatcher {
+            _watcher: watcher,
+            watched_files: self.0,
+            rx,
+        })
+    }
+}