From b4963f4ff7afaf9fb432a8ff7d2d8241ba6faae4 Mon Sep 17 00:00:00 2001
From: Lucien Greathouse <me@lpghatguy.com>
Date: Tue, 18 Feb 2020 22:42:31 -0800
Subject: [PATCH] Watching

---
 vfs/src/lib.rs          | 24 +++++++++++++++++-------
 vfs/src/noop_backend.rs | 29 +++++++++++++++++++++++++----
 vfs/src/std_backend.rs  | 41 ++++++++++++++++++++++++++++++++++++-----
 3 files changed, 78 insertions(+), 16 deletions(-)

diff --git a/vfs/src/lib.rs b/vfs/src/lib.rs
index 7246111f..836e4443 100644
--- a/vfs/src/lib.rs
+++ b/vfs/src/lib.rs
@@ -8,11 +8,23 @@ use std::sync::{Arc, Mutex};
 pub use noop_backend::NoopBackend;
 pub use std_backend::StdBackend;
 
-pub trait VfsBackend {
-    fn read(&self, path: &Path) -> io::Result<Vec<u8>>;
-    fn write(&self, path: &Path, data: &[u8]) -> io::Result<()>;
-    fn read_dir(&self, path: &Path) -> io::Result<ReadDir>;
-    fn metadata(&self, path: &Path) -> io::Result<Metadata>;
+mod sealed {
+    use super::*;
+
+    pub trait Sealed {}
+
+    impl Sealed for NoopBackend {}
+    impl Sealed for StdBackend {}
+}
+
+pub trait VfsBackend: sealed::Sealed {
+    fn read(&mut self, path: &Path) -> io::Result<Vec<u8>>;
+    fn write(&mut self, path: &Path, data: &[u8]) -> io::Result<()>;
+    fn read_dir(&mut self, path: &Path) -> io::Result<ReadDir>;
+    fn metadata(&mut self, path: &Path) -> io::Result<Metadata>;
+
+    fn watch(&mut self, path: &Path) -> io::Result<()>;
+    fn unwatch(&mut self, path: &Path) -> io::Result<()>;
 }
 
 pub struct DirEntry {
@@ -52,7 +64,6 @@ impl Metadata {
 }
 
 struct VfsLock {
-    data: (),
     backend: Box<dyn VfsBackend>,
 }
 
@@ -86,7 +97,6 @@ pub struct Vfs {
 impl Vfs {
     pub fn new<B: VfsBackend + 'static>(backend: B) -> Self {
         let lock = VfsLock {
-            data: (),
             backend: Box::new(backend),
         };
 
diff --git a/vfs/src/noop_backend.rs b/vfs/src/noop_backend.rs
index 95e66205..7b210f28 100644
--- a/vfs/src/noop_backend.rs
+++ b/vfs/src/noop_backend.rs
@@ -3,31 +3,52 @@ use std::path::Path;
 
 use crate::{Metadata, ReadDir, VfsBackend};
 
+#[non_exhaustive]
 pub struct NoopBackend;
 
+impl NoopBackend {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
 impl VfsBackend for NoopBackend {
-    fn read(&self, path: &Path) -> io::Result<Vec<u8>> {
+    fn read(&mut self, _path: &Path) -> io::Result<Vec<u8>> {
         Err(io::Error::new(
             io::ErrorKind::Other,
             "NoopBackend doesn't do anything",
         ))
     }
 
-    fn write(&self, path: &Path, data: &[u8]) -> io::Result<()> {
+    fn write(&mut self, _path: &Path, _data: &[u8]) -> io::Result<()> {
         Err(io::Error::new(
             io::ErrorKind::Other,
             "NoopBackend doesn't do anything",
         ))
     }
 
-    fn read_dir(&self, path: &Path) -> io::Result<ReadDir> {
+    fn read_dir(&mut self, _path: &Path) -> io::Result<ReadDir> {
         Err(io::Error::new(
             io::ErrorKind::Other,
             "NoopBackend doesn't do anything",
         ))
     }
 
-    fn metadata(&self, path: &Path) -> io::Result<Metadata> {
+    fn metadata(&mut self, _path: &Path) -> io::Result<Metadata> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "NoopBackend doesn't do anything",
+        ))
+    }
+
+    fn watch(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "NoopBackend doesn't do anything",
+        ))
+    }
+
+    fn unwatch(&mut self, _path: &Path) -> io::Result<()> {
         Err(io::Error::new(
             io::ErrorKind::Other,
             "NoopBackend doesn't do anything",
diff --git a/vfs/src/std_backend.rs b/vfs/src/std_backend.rs
index 1e2d4f6d..940b7b8f 100644
--- a/vfs/src/std_backend.rs
+++ b/vfs/src/std_backend.rs
@@ -1,21 +1,40 @@
 use std::fs;
 use std::io;
 use std::path::Path;
+use std::sync::mpsc;
+use std::time::Duration;
+
+use notify::{watcher, DebouncedEvent, RecommendedWatcher, RecursiveMode, Watcher};
 
 use crate::{DirEntry, Metadata, ReadDir, VfsBackend};
 
-pub struct StdBackend;
+pub struct StdBackend {
+    watcher: RecommendedWatcher,
+    watcher_receiver: mpsc::Receiver<DebouncedEvent>,
+}
+
+impl StdBackend {
+    pub fn new() -> StdBackend {
+        let (tx, rx) = mpsc::channel();
+        let watcher = watcher(tx, Duration::from_millis(50)).unwrap();
+
+        Self {
+            watcher,
+            watcher_receiver: rx,
+        }
+    }
+}
 
 impl VfsBackend for StdBackend {
-    fn read(&self, path: &Path) -> io::Result<Vec<u8>> {
+    fn read(&mut self, path: &Path) -> io::Result<Vec<u8>> {
         fs::read(path)
     }
 
-    fn write(&self, path: &Path, data: &[u8]) -> io::Result<()> {
+    fn write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         fs::write(path, data)
     }
 
-    fn read_dir(&self, path: &Path) -> io::Result<ReadDir> {
+    fn read_dir(&mut self, path: &Path) -> io::Result<ReadDir> {
         let inner = fs::read_dir(path)?.map(|entry| {
             Ok(DirEntry {
                 path: entry?.path(),
@@ -27,11 +46,23 @@ impl VfsBackend for StdBackend {
         })
     }
 
-    fn metadata(&self, path: &Path) -> io::Result<Metadata> {
+    fn metadata(&mut self, path: &Path) -> io::Result<Metadata> {
         let inner = fs::metadata(path)?;
 
         Ok(Metadata {
             is_file: inner.is_file(),
         })
     }
+
+    fn watch(&mut self, path: &Path) -> io::Result<()> {
+        self.watcher
+            .watch(path, RecursiveMode::NonRecursive)
+            .map_err(|inner| io::Error::new(io::ErrorKind::Other, inner))
+    }
+
+    fn unwatch(&mut self, path: &Path) -> io::Result<()> {
+        self.watcher
+            .unwatch(path)
+            .map_err(|inner| io::Error::new(io::ErrorKind::Other, inner))
+    }
 }