Stub out more of the file system watcher structure.

Cargo.lock

  "unicode-normalization 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "inotify"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures-core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "inotify-sys 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mio 0.6.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.9 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "inotify-sys"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "input_buffer"
 version = "0.2.0"
  "env_logger 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-tokio-compat 0.1.0 (git+https://github.com/mgottschlag/futures-tokio-compat.git)",
+ "inotify 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.44 (registry+https://github.com/rust-lang/crates.io-index)",
 "checksum httparse 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "cd179ae861f0c2e53da70d892f5f3029f9594be0c41dc5269cd371691b1dc2f9"
 "checksum humantime 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "df004cfca50ef23c36850aaaa59ad52cc70d0e90243c3c7737a4dd32dc7a3c4f"
 "checksum idna 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "02e2673c30ee86b5b96a9cb52ad15718aa1f966f5ab9ad54a8b95d5ca33120a9"
+"checksum inotify 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c45f8a4a890357e626ac878be77e43d9a29ca17f67c477517c26ee108d32d973"
+"checksum inotify-sys 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "e74a1aa87c59aeff6ef2cc2fa62d41bc43f54952f55652656b18a02fd5e356c0"
 "checksum input_buffer 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8e1b822cc844905551931d6f81608ed5f50a79c1078a4e2b4d42dbc7c1eedfbf"
 "checksum iovec 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "b2b3ea6ff95e175473f8ffe6a7eb7c00d054240321b84c57051175fe3c1e075e"
 "checksum itoa 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "501266b7edd0174f8530248f87f99c88fbe60ca4ef3dd486835b8d8d53136f7f"

Cargo.toml

 edition = "2018"
 
 [dependencies]
-#fswatcher = { path = "./fswatcher" }
 structopt = "0.3"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 async-tungstenite = { version = "0.3", features = ["tokio-runtime"] }
 env_logger = "0.7"
 log = "0.4"
+inotify = "0.8"

src/file_system_watcher.rs

+use std::collections::VecDeque;
 use std::sync::Arc;
+use std::path::Path;
 
+use inotify::{Inotify, WatchMask};
 use tokio::sync::{mpsc, oneshot, Mutex};
+use tokio::task;
 
 use super::{Error, FileTree};
 
     }
 
     async fn task_paused(
-        _file_tree: Arc<Mutex<FileTree>>,
+        mut file_tree: Arc<Mutex<FileTree>>,
         mut state_receive: mpsc::Receiver<(StateChange, oneshot::Sender<()>)>,
     ) {
         let mut paused = true;
             } else {
                 // We were unpaused, initialize the file system watcher and start waiting for
                 // that as well.
+                let next_state = Self::task_unpaused(&mut file_tree, &mut state_receive).await;
+                match next_state {
+                    StateChange::Pause => paused = true,
+                    StateChange::Unpause => paused = false,
+                    StateChange::Terminate => break,
+                }
+            }
+        }
+    }
+
+    async fn task_unpaused(
+        file_tree: &mut Arc<Mutex<FileTree>>,
+        _state_receive: &mut mpsc::Receiver<(StateChange, oneshot::Sender<()>)>,
+    ) -> StateChange {
+        let mut inotify = Inotify::init().expect("Failed to initialize inotify");
+        let mut new_directories = VecDeque::new();
+        new_directories.push_back(file_tree.lock().await.root_path().to_owned());
+
+        let mut inotify_buffer = InotifyBuffer { data: [0; 1024] };
+        let _inotify_stream = inotify.event_stream(&mut inotify_buffer).unwrap();
+        //let watches_by_path = BTreeMap::new();
+        //let paths_by_watch = HashMap::new();
+
+        loop {
+            if new_directories.is_empty() {
+                // If all the inotify watches are up-to-date, simply wait for any events.
                 // TODO
+            } else {
+                // Install an inotify watch for the directory and check the directory contents
+                // against the database.
+                let new_directory = new_directories.pop_front().unwrap();
+                // TODO: Do not follow links!
+                // TODO: Is ONLYDIR correct?
+                // TODO: We want to delay events for 2-3 seconds, so that we limit the rate of
+                // modification events and so that we are maybe able to detect moved
+                // files/directories across different directories!
+                if Path::new(&new_directory).is_dir() {
+                    let watch = inotify.add_watch(new_directory, WatchMask::ATTRIB | WatchMask::CLOSE_WRITE | WatchMask::CREATE | WatchMask::DELETE | WatchMask::DELETE_SELF | WatchMask::MODIFY | WatchMask::MOVE | WatchMask::EXCL_UNLINK | WatchMask::ONLYDIR);
+                    // TODO
+                }
+
+                // Proceed recursively at the next loop iteration.
+                // TODO
+
+                // Poll for events (without blocking, so that we immediately process the next
+                // directory if nothing happened).
+                // TODO
+
+                // Yield to other parts of the program to minimize the impact of scanning large
+                // directory trees.
+                // TODO: Check whether this is really necessary and how large the impact on
+                // performance is.
+                task::yield_now().await;
             }
         }
     }
     }
 }
 
+struct InotifyBuffer {
+    data: [u8; 1024],
+}
+
+impl AsMut<[u8]> for InotifyBuffer {
+    fn as_mut<'a>(&'a mut self) -> &'a mut [u8] {
+        &mut self.data
+    }
+}
+
+impl AsRef<[u8]> for InotifyBuffer {
+    fn as_ref<'a>(&'a self) -> &'a [u8] {
+        &self.data
+    }
+}
+
 #[derive(Debug)]
 enum StateChange {
     Pause,

src/filetree.rs

     db: Arc<Mutex<Database>>,
     new_version_notifiers: Vec<UnboundedSender<NewVersionEvent>>,
     next_version_source: u64,
+    root_path: String,
 }
 
 impl FileTree {
-    pub fn open(db: Arc<Mutex<Database>>, _directory: &str) -> Result<FileTree, Error> {
+    pub fn open(db: Arc<Mutex<Database>>, directory: &str) -> Result<FileTree, Error> {
         // Check whether the database entry for this file tree exists and fetch the root
         // file ID.
         // TODO
             db,
             new_version_notifiers: Vec::new(),
             next_version_source: 0,
+            root_path: directory.to_owned(),
         })
     }
 
+    pub fn root_path(&self) -> &str {
+        &self.root_path
+    }
+
     pub fn new_notifier(&mut self) -> NewVersionNotifier {
         let (send, receive) = unbounded_channel();
         self.new_version_notifiers.push(send);