notify/

inotify.rs

//! Watcher implementation for the inotify Linux API
//!
//! The inotify API provides a mechanism for monitoring filesystem events.  Inotify can be used to
//! monitor individual files, or to monitor directories.  When a directory is monitored, inotify
//! will return events for the directory itself, and for files inside the directory.

use super::event::*;
use super::{Config, Error, ErrorKind, EventHandler, RecursiveMode, Result, WatchMode, Watcher};
use crate::bimap::BiHashMap;
use crate::{BoundSender, Receiver, Sender, TargetMode, bounded, unbounded};
use inotify as inotify_sys;
use inotify_sys::{EventMask, Inotify, WatchDescriptor, WatchMask};
use std::collections::HashMap;
#[cfg(test)]
use std::collections::HashSet;
use std::env;
use std::fs::metadata;
use std::os::unix::fs::MetadataExt;
use std::os::unix::io::AsRawFd;
use std::path::{Path, PathBuf};
use std::sync::Arc;
use std::thread;
use walkdir::WalkDir;

const INOTIFY: mio::Token = mio::Token(0);
const MESSAGE: mio::Token = mio::Token(1);

// The EventLoop will set up a mio::Poll and use it to wait for the following:
//
// -  messages telling it what to do
//
// -  events telling it that something has happened on one of the watched files.

struct EventLoop {
    running: bool,
    poll: mio::Poll,
    event_loop_waker: Arc<mio::Waker>,
    event_loop_tx: Sender<EventLoopMsg>,
    event_loop_rx: Receiver<EventLoopMsg>,
    inotify: Option<Inotify>,
    event_handler: Box<dyn EventHandler>,
    watches: HashMap<PathBuf, WatchMode>,
    watch_handles: BiHashMap<WatchDescriptor, PathBuf, (/* watch_self */ bool, /* is_dir */ bool)>,
    rename_event: Option<Event>,
    follow_links: bool,
}

/// Watcher implementation based on inotify
#[derive(Debug)]
pub struct INotifyWatcher {
    channel: Sender<EventLoopMsg>,
    waker: Arc<mio::Waker>,
}

enum EventLoopMsg {
    AddWatch(PathBuf, WatchMode, Sender<Result<()>>),
    RemoveWatch(PathBuf, Sender<Result<()>>),
    Shutdown,
    Configure(Config, BoundSender<Result<bool>>),
    #[cfg(test)]
    GetWatchHandles(BoundSender<HashSet<PathBuf>>),
}

#[inline]
fn add_watch_by_event(
    path: &PathBuf,
    is_file_without_hardlinks: bool,
    watches: &HashMap<PathBuf, WatchMode>,
    add_watches: &mut Vec<(PathBuf, bool, bool)>,
) {
    if let Some(watch_mode) = watches.get(path) {
        add_watches.push((
            path.to_owned(),
            watch_mode.recursive_mode.is_recursive(),
            is_file_without_hardlinks,
        ));
        return;
    }

    let Some(parent) = path.parent() else {
        return;
    };
    if let Some(watch_mode) = watches.get(parent) {
        add_watches.push((
            path.to_owned(),
            watch_mode.recursive_mode.is_recursive(),
            is_file_without_hardlinks,
        ));
        return;
    }

    let mut current = parent;
    while let Some(parent) = current.parent() {
        if let Some(watch_mode) = watches.get(parent)
            && watch_mode.recursive_mode == RecursiveMode::Recursive
        {
            add_watches.push((path.to_owned(), true, is_file_without_hardlinks));
            return;
        }
        current = parent;
    }
}

#[inline]
fn remove_watch_by_event(
    path: &PathBuf,
    watch_handles: &BiHashMap<WatchDescriptor, PathBuf, (bool, bool)>,
    remove_watches: &mut Vec<PathBuf>,
) {
    if watch_handles.contains_right(path) {
        remove_watches.push(path.to_owned());
    }
}

impl EventLoop {
    pub fn new(
        inotify: Inotify,
        event_handler: Box<dyn EventHandler>,
        follow_links: bool,
    ) -> Result<Self> {
        let (event_loop_tx, event_loop_rx) = unbounded::<EventLoopMsg>();
        let poll = mio::Poll::new()?;

        let event_loop_waker = Arc::new(mio::Waker::new(poll.registry(), MESSAGE)?);

        let inotify_fd = inotify.as_raw_fd();
        let mut evented_inotify = mio::unix::SourceFd(&inotify_fd);
        poll.registry()
            .register(&mut evented_inotify, INOTIFY, mio::Interest::READABLE)?;

        let event_loop = EventLoop {
            running: true,
            poll,
            event_loop_waker,
            event_loop_tx,
            event_loop_rx,
            inotify: Some(inotify),
            event_handler,
            watches: HashMap::new(),
            watch_handles: BiHashMap::new(),
            rename_event: None,
            follow_links,
        };
        Ok(event_loop)
    }

    // Run the event loop.
    pub fn run(self) {
        let result = thread::Builder::new()
            .name("notify-rs inotify loop".to_string())
            .spawn(|| self.event_loop_thread());
        if let Err(e) = result {
            tracing::error!(?e, "failed to start inotify event loop thread");
        }
    }

    fn event_loop_thread(mut self) {
        let mut events = mio::Events::with_capacity(16);
        loop {
            // Wait for something to happen.
            match self.poll.poll(&mut events, None) {
                Err(ref e) if matches!(e.kind(), std::io::ErrorKind::Interrupted) => {
                    // System call was interrupted, we will retry
                    // TODO: Not covered by tests (to reproduce likely need to setup signal handlers)
                }
                Err(e) => panic!("poll failed: {}", e),
                Ok(()) => {}
            }

            // Process whatever happened.
            for event in &events {
                self.handle_event(event);
            }

            // Stop, if we're done.
            if !self.running {
                break;
            }
        }
    }

    // Handle a single event.
    fn handle_event(&mut self, event: &mio::event::Event) {
        match event.token() {
            MESSAGE => {
                // The channel is readable - handle messages.
                self.handle_messages()
            }
            INOTIFY => {
                // inotify has something to tell us.
                self.handle_inotify()
            }
            _ => unreachable!(),
        }
    }

    fn handle_messages(&mut self) {
        while let Ok(msg) = self.event_loop_rx.try_recv() {
            match msg {
                EventLoopMsg::AddWatch(path, watch_mode, tx) => {
                    let result = tx.send(self.add_watch(path, watch_mode));
                    if let Err(e) = result {
                        tracing::error!(?e, "failed to send AddWatch result");
                    }
                }
                EventLoopMsg::RemoveWatch(path, tx) => {
                    let result = tx.send(self.remove_watch(path));
                    if let Err(e) = result {
                        tracing::error!(?e, "failed to send RemoveWatch result");
                    }
                }
                EventLoopMsg::Shutdown => {
                    let result = self.remove_all_watches();
                    if let Err(e) = result {
                        tracing::error!(?e, "failed to remove all watches on shutdown");
                    }
                    if let Some(inotify) = self.inotify.take() {
                        let result = inotify.close();
                        if let Err(e) = result {
                            tracing::error!(?e, "failed to close inotify instance on shutdown");
                        }
                    }
                    self.running = false;
                    break;
                }
                EventLoopMsg::Configure(config, tx) => {
                    self.configure_raw_mode(config, tx);
                }
                #[cfg(test)]
                EventLoopMsg::GetWatchHandles(tx) => {
                    let handles: HashSet<PathBuf> = self
                        .watch_handles
                        .iter()
                        .map(|(_, path, _)| path.clone())
                        .collect();
                    tx.send(handles).unwrap();
                }
            }
        }
    }

    fn configure_raw_mode(&mut self, _config: Config, tx: BoundSender<Result<bool>>) {
        tx.send(Ok(false))
            .expect("configuration channel disconnected");
    }

    fn is_watched_path(watches: &HashMap<PathBuf, WatchMode>, path: &Path) -> bool {
        if watches.contains_key(path) {
            return true;
        }

        let Some(parent) = path.parent() else {
            return false;
        };
        if watches.contains_key(parent) {
            return true;
        }

        let mut current = parent;
        while let Some(parent) = current.parent() {
            if let Some(watch_mode) = watches.get(parent)
                && watch_mode.recursive_mode == RecursiveMode::Recursive
            {
                return true;
            }
            current = parent;
        }
        false
    }

    fn handle_inotify(&mut self) {
        let mut add_watches = Vec::new();
        let mut remove_watches = Vec::new();

        if let Some(ref mut inotify) = self.inotify {
            let mut buffer = [0; 1024];
            // Read all buffers available.
            loop {
                match inotify.read_events(&mut buffer) {
                    Ok(events) => {
                        let mut num_events = 0;
                        for event in events {
                            tracing::trace!(?event, "inotify event received");

                            num_events += 1;
                            if event.mask.contains(EventMask::Q_OVERFLOW) {
                                let ev = Ok(Event::new(EventKind::Other).set_flag(Flag::Rescan));
                                self.event_handler.handle_event(ev);
                            }

                            let path = match event.name {
                                Some(name) => self
                                    .watch_handles
                                    .get_by_left(&event.wd)
                                    .map(|(root, _)| root.join(name)),
                                None => self
                                    .watch_handles
                                    .get_by_left(&event.wd)
                                    .map(|(root, _)| root.clone()),
                            };

                            let path = match path {
                                Some(path) => path,
                                None => {
                                    tracing::debug!(
                                        ?event,
                                        "inotify event with unknown descriptor"
                                    );
                                    continue;
                                }
                            };

                            let mut evs = Vec::new();

                            if event.mask.contains(EventMask::MOVED_FROM) {
                                remove_watch_by_event(
                                    &path,
                                    &self.watch_handles,
                                    &mut remove_watches,
                                );

                                let event = Event::new(EventKind::Modify(ModifyKind::Name(
                                    RenameMode::From,
                                )))
                                .add_path(path.clone())
                                .set_tracker(event.cookie as usize);

                                self.rename_event = Some(event.clone());

                                if Self::is_watched_path(&self.watches, &path) {
                                    evs.push(event);
                                }
                            } else if event.mask.contains(EventMask::MOVED_TO) {
                                if Self::is_watched_path(&self.watches, &path) {
                                    evs.push(
                                        Event::new(EventKind::Modify(ModifyKind::Name(
                                            RenameMode::To,
                                        )))
                                        .set_tracker(event.cookie as usize)
                                        .add_path(path.clone()),
                                    );

                                    let trackers_match =
                                        self.rename_event.as_ref().and_then(|e| e.tracker())
                                            == Some(event.cookie as usize);

                                    if trackers_match {
                                        let rename_event = self.rename_event.take().unwrap(); // unwrap is safe because `rename_event` must be set at this point
                                        let from_path = rename_event.paths.first();
                                        if from_path.is_none_or(|from_path| {
                                            Self::is_watched_path(&self.watches, from_path)
                                        }) {
                                            evs.push(
                                                Event::new(EventKind::Modify(ModifyKind::Name(
                                                    RenameMode::Both,
                                                )))
                                                .set_tracker(event.cookie as usize)
                                                .add_some_path(from_path.cloned())
                                                .add_path(path.clone()),
                                            );
                                        }
                                    }
                                }

                                let is_file_without_hardlinks =
                                    !event.mask.contains(EventMask::ISDIR)
                                        && metadata(&path)
                                            .map(|m| m.is_file_without_hardlinks())
                                            .unwrap_or_default();
                                add_watch_by_event(
                                    &path,
                                    is_file_without_hardlinks,
                                    &self.watches,
                                    &mut add_watches,
                                );
                            }
                            if event.mask.contains(EventMask::MOVE_SELF) {
                                remove_watch_by_event(
                                    &path,
                                    &self.watch_handles,
                                    &mut remove_watches,
                                );
                                if Self::is_watched_path(&self.watches, &path) {
                                    evs.push(
                                        Event::new(EventKind::Modify(ModifyKind::Name(
                                            RenameMode::From,
                                        )))
                                        .add_path(path.clone()),
                                    );
                                    // TODO stat the path and get to new path
                                    // - emit To and Both events
                                    // - change prefix for further events
                                }
                            }
                            if event.mask.contains(EventMask::CREATE) {
                                let is_dir = event.mask.contains(EventMask::ISDIR);
                                if Self::is_watched_path(&self.watches, &path) {
                                    evs.push(
                                        Event::new(EventKind::Create(if is_dir {
                                            CreateKind::Folder
                                        } else {
                                            CreateKind::File
                                        }))
                                        .add_path(path.clone()),
                                    );
                                }
                                let is_file_without_hardlinks = !is_dir
                                    && metadata(&path)
                                        .map(|m| m.is_file_without_hardlinks())
                                        .unwrap_or_default();
                                add_watch_by_event(
                                    &path,
                                    is_file_without_hardlinks,
                                    &self.watches,
                                    &mut add_watches,
                                );
                            }
                            if event.mask.contains(EventMask::DELETE) {
                                if Self::is_watched_path(&self.watches, &path) {
                                    evs.push(
                                        Event::new(EventKind::Remove(
                                            if event.mask.contains(EventMask::ISDIR) {
                                                RemoveKind::Folder
                                            } else {
                                                RemoveKind::File
                                            },
                                        ))
                                        .add_path(path.clone()),
                                    );
                                }
                                remove_watch_by_event(
                                    &path,
                                    &self.watch_handles,
                                    &mut remove_watches,
                                );
                            }
                            if event.mask.contains(EventMask::DELETE_SELF) {
                                let remove_kind = match self.watch_handles.get_by_right(&path) {
                                    Some((_, (_, true))) => RemoveKind::Folder,
                                    Some((_, (_, false))) => RemoveKind::File,
                                    None => RemoveKind::Other,
                                };
                                if Self::is_watched_path(&self.watches, &path) {
                                    evs.push(
                                        Event::new(EventKind::Remove(remove_kind))
                                            .add_path(path.clone()),
                                    );
                                }
                                remove_watch_by_event(
                                    &path,
                                    &self.watch_handles,
                                    &mut remove_watches,
                                );
                            }
                            if event.mask.contains(EventMask::MODIFY)
                                && Self::is_watched_path(&self.watches, &path)
                            {
                                evs.push(
                                    Event::new(EventKind::Modify(ModifyKind::Data(
                                        DataChange::Any,
                                    )))
                                    .add_path(path.clone()),
                                );
                            }
                            if event.mask.contains(EventMask::CLOSE_WRITE)
                                && Self::is_watched_path(&self.watches, &path)
                            {
                                evs.push(
                                    Event::new(EventKind::Access(AccessKind::Close(
                                        AccessMode::Write,
                                    )))
                                    .add_path(path.clone()),
                                );
                            }
                            if event.mask.contains(EventMask::CLOSE_NOWRITE)
                                && Self::is_watched_path(&self.watches, &path)
                            {
                                evs.push(
                                    Event::new(EventKind::Access(AccessKind::Close(
                                        AccessMode::Read,
                                    )))
                                    .add_path(path.clone()),
                                );
                            }
                            if event.mask.contains(EventMask::ATTRIB)
                                && Self::is_watched_path(&self.watches, &path)
                            {
                                evs.push(
                                    Event::new(EventKind::Modify(ModifyKind::Metadata(
                                        MetadataKind::Any,
                                    )))
                                    .add_path(path.clone()),
                                );
                            }
                            if event.mask.contains(EventMask::OPEN)
                                && Self::is_watched_path(&self.watches, &path)
                            {
                                evs.push(
                                    Event::new(EventKind::Access(AccessKind::Open(
                                        AccessMode::Any,
                                    )))
                                    .add_path(path.clone()),
                                );
                            }

                            for ev in evs {
                                self.event_handler.handle_event(Ok(ev));
                            }
                        }

                        // All events read. Break out.
                        if num_events == 0 {
                            break;
                        }
                    }
                    Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => {
                        // No events read. Break out.
                        break;
                    }
                    Err(e) => {
                        self.event_handler.handle_event(Err(Error::io(e)));
                    }
                }
            }
        }

        tracing::trace!(
            ?add_watches,
            ?remove_watches,
            "processing inotify watch changes"
        );

        for path in remove_watches {
            if self
                .watches
                .get(&path)
                .is_some_and(|watch_mode| watch_mode.target_mode == TargetMode::NoTrack)
            {
                self.watches.remove(&path);
            }
            self.remove_maybe_recursive_watch(path, true).ok();
        }

        for (path, is_recursive, is_file_without_hardlinks) in add_watches {
            if let Err(add_watch_error) =
                self.add_maybe_recursive_watch(path, is_recursive, is_file_without_hardlinks, false)
            {
                // The handler should be notified if we have reached the limit.
                // Otherwise, the user might expect that a recursive watch
                // is continuing to work correctly, but it's not.
                if let ErrorKind::MaxFilesWatch = add_watch_error.kind {
                    self.event_handler.handle_event(Err(add_watch_error));

                    // After that kind of a error we should stop adding watches,
                    // because the limit has already reached and all next calls
                    // will return us only the same error.
                    break;
                }
            }
        }
    }

    #[tracing::instrument(level = "trace", skip(self))]
    fn add_watch(&mut self, path: PathBuf, watch_mode: WatchMode) -> Result<()> {
        if let Some(existing) = self.watches.get(&path) {
            let need_upgrade_to_recursive = match existing.recursive_mode {
                RecursiveMode::Recursive => false,
                RecursiveMode::NonRecursive => {
                    watch_mode.recursive_mode == RecursiveMode::Recursive
                }
            };
            let need_to_watch_parent_newly = match existing.target_mode {
                TargetMode::TrackPath => false,
                TargetMode::NoTrack => watch_mode.target_mode == TargetMode::TrackPath,
            };
            tracing::trace!(
                ?need_upgrade_to_recursive,
                ?need_to_watch_parent_newly,
                "upgrading existing watch for path: {}",
                path.display()
            );
            if need_to_watch_parent_newly && let Some(parent) = path.parent() {
                self.add_single_watch(parent.to_path_buf(), true, false)?;
            }
            if !need_upgrade_to_recursive {
                return Ok(());
            }

            // upgrade to recursive
            if metadata(&path).map_err(Error::io)?.is_dir() {
                self.add_maybe_recursive_watch(path.clone(), true, false, true)?;
            }
            self.watches
                .get_mut(&path)
                .unwrap()
                .upgrade_with(watch_mode);
            return Ok(());
        }

        if watch_mode.target_mode == TargetMode::TrackPath
            && let Some(parent) = path.parent()
        {
            self.add_single_watch(parent.to_path_buf(), true, false)?;
        }

        let meta = match metadata(&path).map_err(Error::io_watch) {
            Ok(metadata) => metadata,
            Err(err) => {
                if watch_mode.target_mode == TargetMode::TrackPath
                    && matches!(err.kind, ErrorKind::PathNotFound)
                {
                    self.watches.insert(path, watch_mode);
                    return Ok(());
                }
                return Err(err);
            }
        };

        self.add_maybe_recursive_watch(
            path.clone(),
            // If the watch is not recursive, or if we determine (by stat'ing the path to get its
            // metadata) that the watched path is not a directory, add a single path watch.
            watch_mode.recursive_mode.is_recursive() && meta.is_dir(),
            meta.is_file_without_hardlinks(),
            watch_mode.target_mode != TargetMode::TrackPath, // parent is watched, so no need to watch self
        )?;

        self.watches.insert(path, watch_mode);

        Ok(())
    }

    #[tracing::instrument(level = "trace", skip(self))]
    fn add_maybe_recursive_watch(
        &mut self,
        path: PathBuf,
        is_recursive: bool,
        is_file_without_hardlinks: bool,
        mut watch_self: bool,
    ) -> Result<()> {
        if is_recursive {
            for entry in WalkDir::new(&path)
                .follow_links(self.follow_links)
                .into_iter()
                .filter_map(filter_dir)
            {
                self.add_single_watch(entry.into_path(), false, watch_self)?;
                watch_self = false;
            }
        } else {
            self.add_single_watch(path.clone(), is_file_without_hardlinks, watch_self)?;
        }
        Ok(())
    }

    #[tracing::instrument(level = "trace", skip(self))]
    fn add_single_watch(
        &mut self,
        path: PathBuf,
        is_file_without_hardlinks: bool,
        watch_self: bool,
    ) -> Result<()> {
        if let Some((_, &(old_watch_self, _))) = self.watch_handles.get_by_right(&path)
            // if upgrade to watch self is not needed
            && (old_watch_self || !watch_self)
        {
            tracing::trace!(
                "watch handle already exists and no need to upgrade: {}",
                path.display()
            );
            return Ok(());
        }

        if is_file_without_hardlinks
            && let Some(parent) = path.parent()
            && self.watch_handles.get_by_right(parent).is_some()
        {
            tracing::trace!(
                "parent dir watch handle already exists and is a file without hardlinks: {}",
                path.display()
            );
            return Ok(());
        }

        let mut watchmask = WatchMask::ATTRIB
            | WatchMask::CREATE
            | WatchMask::OPEN
            | WatchMask::DELETE
            | WatchMask::CLOSE_WRITE
            | WatchMask::MODIFY
            | WatchMask::MOVED_FROM
            | WatchMask::MOVED_TO;
        if watch_self {
            watchmask.insert(WatchMask::DELETE_SELF);
            watchmask.insert(WatchMask::MOVE_SELF);
        }

        if let Some(ref mut inotify) = self.inotify {
            tracing::trace!("adding inotify watch: {}", path.display());

            match inotify.watches().add(&path, watchmask) {
                Err(e) => {
                    Err(if e.raw_os_error() == Some(libc::ENOSPC) {
                        // do not report inotify limits as "no more space" on linux #266
                        Error::new(ErrorKind::MaxFilesWatch)
                    } else if e.kind() == std::io::ErrorKind::NotFound {
                        Error::new(ErrorKind::PathNotFound)
                    } else {
                        Error::io(e)
                    }
                    .add_path(path))
                }
                Ok(w) => {
                    watchmask.remove(WatchMask::MASK_ADD);
                    let is_dir = metadata(&path).map_err(Error::io)?.is_dir();
                    self.watch_handles.insert(w, path, (watch_self, is_dir));
                    Ok(())
                }
            }
        } else {
            Ok(())
        }
    }

    #[tracing::instrument(level = "trace", skip(self))]
    fn remove_watch(&mut self, path: PathBuf) -> Result<()> {
        match self.watches.remove(&path) {
            None => return Err(Error::watch_not_found().add_path(path)),
            Some(watch_mode) => {
                self.remove_maybe_recursive_watch(path, watch_mode.recursive_mode.is_recursive())?;
            }
        }
        Ok(())
    }

    #[tracing::instrument(level = "trace", skip(self))]
    fn remove_maybe_recursive_watch(&mut self, path: PathBuf, is_recursive: bool) -> Result<()> {
        let Some(ref mut inotify) = self.inotify else {
            return Ok(());
        };
        let mut inotify_watches = inotify.watches();

        if let Some((handle, _)) = self.watch_handles.remove_by_right(&path) {
            tracing::trace!("removing inotify watch: {}", path.display());

            inotify_watches
                .remove(handle.clone())
                .map_err(|e| Error::io(e).add_path(path.clone()))?;
        }

        if is_recursive {
            let mut remove_list = Vec::new();
            for (w, p, _) in &self.watch_handles {
                if p.starts_with(&path) {
                    inotify_watches
                        .remove(w.clone())
                        .map_err(|e| Error::io(e).add_path(p.into()))?;
                    remove_list.push(w.clone());
                }
            }
            for w in remove_list {
                self.watch_handles.remove_by_left(&w);
            }
        }
        Ok(())
    }

    fn remove_all_watches(&mut self) -> Result<()> {
        if let Some(ref mut inotify) = self.inotify {
            let mut inotify_watches = inotify.watches();
            for (w, p, _) in &self.watch_handles {
                inotify_watches
                    .remove(w.clone())
                    .map_err(|e| Error::io(e).add_path(p.into()))?;
            }
            self.watch_handles.clear();
            self.watches.clear();
        }
        Ok(())
    }
}

/// return `DirEntry` when it is a directory
fn filter_dir(e: walkdir::Result<walkdir::DirEntry>) -> Option<walkdir::DirEntry> {
    if let Ok(e) = e
        && let Ok(metadata) = e.metadata()
        && metadata.is_dir()
    {
        return Some(e);
    }
    None
}

impl INotifyWatcher {
    fn from_event_handler(
        event_handler: Box<dyn EventHandler>,
        follow_links: bool,
    ) -> Result<Self> {
        let inotify = Inotify::init()?;
        let event_loop = EventLoop::new(inotify, event_handler, follow_links)?;
        let channel = event_loop.event_loop_tx.clone();
        let waker = event_loop.event_loop_waker.clone();
        event_loop.run();
        Ok(INotifyWatcher { channel, waker })
    }

    fn watch_inner(&mut self, path: &Path, watch_mode: WatchMode) -> Result<()> {
        let pb = if path.is_absolute() {
            path.to_owned()
        } else {
            let p = env::current_dir().map_err(Error::io)?;
            p.join(path)
        };
        let (tx, rx) = unbounded();
        let msg = EventLoopMsg::AddWatch(pb, watch_mode, tx);

        // we expect the event loop to live and reply => unwraps must not panic
        self.channel.send(msg).unwrap();
        self.waker.wake().unwrap();
        rx.recv().unwrap()
    }

    fn unwatch_inner(&mut self, path: &Path) -> Result<()> {
        let pb = if path.is_absolute() {
            path.to_owned()
        } else {
            let p = env::current_dir().map_err(Error::io)?;
            p.join(path)
        };
        let (tx, rx) = unbounded();
        let msg = EventLoopMsg::RemoveWatch(pb, tx);

        // we expect the event loop to live and reply => unwraps must not panic
        self.channel.send(msg).unwrap();
        self.waker.wake().unwrap();
        rx.recv().unwrap()
    }
}

impl Watcher for INotifyWatcher {
    /// Create a new watcher.
    #[tracing::instrument(level = "debug", skip(event_handler))]
    fn new<F: EventHandler>(event_handler: F, config: Config) -> Result<Self> {
        Self::from_event_handler(Box::new(event_handler), config.follow_symlinks())
    }

    #[tracing::instrument(level = "debug", skip(self))]
    fn watch(&mut self, path: &Path, watch_mode: WatchMode) -> Result<()> {
        self.watch_inner(path, watch_mode)
    }

    #[tracing::instrument(level = "debug", skip(self))]
    fn unwatch(&mut self, path: &Path) -> Result<()> {
        self.unwatch_inner(path)
    }

    #[tracing::instrument(level = "debug", skip(self))]
    fn configure(&mut self, config: Config) -> Result<bool> {
        let (tx, rx) = bounded(1);
        self.channel.send(EventLoopMsg::Configure(config, tx))?;
        self.waker.wake()?;
        rx.recv()?
    }

    fn kind() -> crate::WatcherKind {
        crate::WatcherKind::Inotify
    }

    #[cfg(test)]
    fn get_watch_handles(&self) -> std::collections::HashSet<std::path::PathBuf> {
        let (tx, rx) = bounded(1);
        self.channel
            .send(EventLoopMsg::GetWatchHandles(tx))
            .unwrap();
        self.waker.wake().unwrap();
        rx.recv().unwrap()
    }
}

impl Drop for INotifyWatcher {
    fn drop(&mut self) {
        // we expect the event loop to live => unwrap must not panic
        self.channel.send(EventLoopMsg::Shutdown).unwrap();
        self.waker.wake().unwrap();
    }
}

trait MetadataNotifyExt {
    fn is_file_without_hardlinks(&self) -> bool;
}

impl MetadataNotifyExt for std::fs::Metadata {
    #[inline]
    fn is_file_without_hardlinks(&self) -> bool {
        self.is_file() && self.nlink() == 1
    }
}

#[cfg(test)]
mod tests {
    use std::{
        collections::HashSet,
        path::{Path, PathBuf},
        sync::{Arc, atomic::AtomicBool, mpsc},
        thread::{self, available_parallelism},
        time::Duration,
    };

    use super::{Config, Error, ErrorKind, Event, INotifyWatcher, Result, Watcher};

    use crate::{RecursiveMode, TargetMode, config::WatchMode, test::*};

    fn watcher() -> (TestWatcher<INotifyWatcher>, Receiver) {
        channel()
    }

    #[test]
    fn inotify_watcher_is_send_and_sync() {
        fn check<T: Send + Sync>() {}
        check::<INotifyWatcher>();
    }

    #[test]
    fn native_error_type_on_missing_path() {
        let mut watcher = INotifyWatcher::new(|_| {}, Config::default()).unwrap();

        let result = watcher.watch(
            &PathBuf::from("/some/non/existant/path"),
            WatchMode::non_recursive(),
        );

        assert!(matches!(
            result,
            Err(Error {
                paths: _,
                kind: ErrorKind::PathNotFound
            })
        ))
    }

    /// Runs manually.
    ///
    /// * Save actual value of the limit: `MAX_USER_WATCHES=$(sysctl -n fs.inotify.max_user_watches)`
    /// * Run the test.
    /// * Set the limit to 0: `sudo sysctl fs.inotify.max_user_watches=0` while test is running
    /// * Wait for the test to complete
    /// * Restore the limit `sudo sysctl fs.inotify.max_user_watches=$MAX_USER_WATCHES`
    #[test]
    #[ignore = "requires changing sysctl fs.inotify.max_user_watches while test is running"]
    fn recursive_watch_calls_handler_if_creating_a_file_raises_max_files_watch() {
        use std::time::Duration;

        let tmpdir = tempfile::tempdir().unwrap();
        let (tx, rx) = std::sync::mpsc::channel();
        let (proc_changed_tx, proc_changed_rx) = std::sync::mpsc::channel();
        let proc_path = Path::new("/proc/sys/fs/inotify/max_user_watches");
        let mut watcher = INotifyWatcher::new(
            move |result: Result<Event>| match result {
                Ok(event) => {
                    if event.paths.first().is_some_and(|path| path == proc_path) {
                        proc_changed_tx.send(()).unwrap();
                    }
                }
                Err(e) => tx.send(e).unwrap(),
            },
            Config::default(),
        )
        .unwrap();

        watcher
            .watch(tmpdir.path(), WatchMode::recursive())
            .unwrap();
        watcher
            .watch(proc_path, WatchMode::non_recursive())
            .unwrap();

        // give the time to set the limit
        proc_changed_rx
            .recv_timeout(Duration::from_secs(30))
            .unwrap();

        let child_dir = tmpdir.path().join("child");
        std::fs::create_dir(child_dir).unwrap();

        let result = rx.recv_timeout(Duration::from_millis(500));

        assert!(
            matches!(
                &result,
                Ok(Error {
                    kind: ErrorKind::MaxFilesWatch,
                    paths: _,
                })
            ),
            "expected {:?}, found: {:#?}",
            ErrorKind::MaxFilesWatch,
            result
        );
    }

    /// https://github.com/notify-rs/notify/issues/678
    #[test]
    fn race_condition_on_unwatch_and_pending_events_with_deleted_descriptor() {
        let tmpdir = tempfile::tempdir().expect("tmpdir");
        let (tx, rx) = mpsc::channel();
        let mut inotify = INotifyWatcher::new(
            move |e: Result<Event>| {
                let e = match e {
                    Ok(e) if e.paths.is_empty() => e,
                    Ok(_) | Err(_) => return,
                };
                let _ = tx.send(e);
            },
            Config::default(),
        )
        .expect("inotify creation");

        let dir_path = tmpdir.path();
        let file_path = dir_path.join("foo");
        std::fs::File::create(&file_path).unwrap();

        let stop = Arc::new(AtomicBool::new(false));

        let handles: Vec<_> = (0..available_parallelism().unwrap().get().max(4))
            .map(|_| {
                let file_path = file_path.clone();
                let stop = stop.clone();
                thread::spawn(move || {
                    while !stop.load(std::sync::atomic::Ordering::Relaxed) {
                        let _ = std::fs::File::open(&file_path).unwrap();
                    }
                })
            })
            .collect();

        let non_recursive = WatchMode::non_recursive();
        for _ in 0..(handles.len() * 4) {
            inotify.watch(dir_path, non_recursive).unwrap();
            inotify.unwatch(dir_path).unwrap();
        }

        stop.store(true, std::sync::atomic::Ordering::Relaxed);
        handles
            .into_iter()
            .for_each(|handle| handle.join().ok().unwrap_or_default());

        drop(inotify);

        let events: Vec<_> = rx.into_iter().map(|e| format!("{e:?}")).collect();

        const LOG_LEN: usize = 10;
        let events_len = events.len();
        assert!(
            events.is_empty(),
            "expected no events without path, but got {events_len}. first 10: {:#?}",
            &events[..LOG_LEN.min(events_len)]
        );
    }

    #[test]
    fn create_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        watcher.watch_recursively(&tmpdir);

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).create_file(),
            expected(&path).access_open_any(),
            expected(&path).access_close_write(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn create_self_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");

        watcher.watch_nonrecursively(&path);

        std::fs::File::create_new(&path).expect("create");

        rx.wait_ordered_exact([
            expected(&path).create_file(),
            expected(&path).access_open_any(),
            expected(&path).access_close_write(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn create_self_file_no_track() {
        let tmpdir = testdir();
        let (mut watcher, _) = watcher();

        let path = tmpdir.path().join("entry");

        let result = watcher.watcher.watch(
            &path,
            WatchMode {
                recursive_mode: RecursiveMode::NonRecursive,
                target_mode: TargetMode::NoTrack,
            },
        );
        assert!(matches!(
            result,
            Err(Error {
                paths: _,
                kind: ErrorKind::PathNotFound
            })
        ));
    }

    #[test]
    #[ignore = "TODO: not implemented"]
    fn create_self_file_nested() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry/nested");

        watcher.watch_nonrecursively(&path);

        std::fs::create_dir_all(path.parent().unwrap()).expect("create");
        std::fs::File::create_new(&path).expect("create");

        rx.wait_ordered_exact([
            expected(&path).create_file(),
            expected(&path).access_open_any(),
            expected(&path).access_close_write(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn create_file_nested_in_recursive_watch() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let nested1_dir = tmpdir.path().join("nested1");
        let nested2_dir = nested1_dir.join("nested2");
        std::fs::create_dir_all(&nested2_dir).expect("create_dir");

        watcher.watch_recursively(&tmpdir);

        let path = nested2_dir.join("entry");
        std::fs::File::create_new(&path).expect("create");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&nested1_dir).access_open_any().optional(),
            expected(&nested2_dir).access_open_any().optional(),
            expected(&path).create_file(),
            expected(&path).access_open_any(),
            expected(&path).access_close_write(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([
                tmpdir.parent_path_buf(),
                tmpdir.to_path_buf(),
                nested1_dir,
                nested2_dir
            ])
        )
    }

    #[test]
    fn write_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch_recursively(&tmpdir);
        std::fs::write(&path, b"123").expect("write");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).access_open_any(),
            expected(&path).modify_data_any().multiple(),
            expected(&path).access_close_write(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn chmod_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        let file = std::fs::File::create_new(&path).expect("create");
        let mut permissions = file.metadata().expect("metadata").permissions();
        permissions.set_readonly(true);

        watcher.watch_recursively(&tmpdir);
        file.set_permissions(permissions).expect("set_permissions");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).modify_meta_any(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn rename_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch_recursively(&tmpdir);
        let new_path = tmpdir.path().join("renamed");

        std::fs::rename(&path, &new_path).expect("rename");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).rename_from(),
            expected(&new_path).rename_to(),
            expected([path, new_path]).rename_both(),
        ])
        .ensure_trackers_len(1)
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn rename_self_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch_nonrecursively(&path);
        let new_path = tmpdir.path().join("renamed");

        std::fs::rename(&path, &new_path).expect("rename");

        rx.wait_ordered_exact([expected(&path).rename_from()])
            .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );

        std::fs::rename(&new_path, &path).expect("rename2");

        rx.wait_ordered_exact([expected(&path).rename_to()])
            .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn rename_self_file_no_track() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch(
            &path,
            WatchMode {
                recursive_mode: RecursiveMode::NonRecursive,
                target_mode: TargetMode::NoTrack,
            },
        );

        let new_path = tmpdir.path().join("renamed");

        std::fs::rename(&path, &new_path).expect("rename");

        rx.wait_ordered_exact([expected(&path).rename_from()])
            .ensure_no_tail();
        assert_eq!(watcher.get_watch_handles(), HashSet::from([]));

        let result = watcher.watcher.watch(
            &path,
            WatchMode {
                recursive_mode: RecursiveMode::NonRecursive,
                target_mode: TargetMode::NoTrack,
            },
        );
        assert!(matches!(
            result,
            Err(Error {
                paths: _,
                kind: ErrorKind::PathNotFound
            })
        ));
    }

    #[test]
    fn delete_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        let file = tmpdir.path().join("file");
        std::fs::write(&file, "").expect("write");

        watcher.watch_nonrecursively(&tmpdir);

        std::fs::remove_file(&file).expect("remove");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&file).remove_file(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn delete_self_file() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        let file = tmpdir.path().join("file");
        std::fs::write(&file, "").expect("write");

        watcher.watch_nonrecursively(&file);

        std::fs::remove_file(&file).expect("remove");

        rx.wait_ordered_exact([expected(&file).remove_file()]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );

        std::fs::write(&file, "").expect("write");

        rx.wait_ordered_exact([expected(&file).create_file()]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn delete_self_file_no_track() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        let file = tmpdir.path().join("file");
        std::fs::write(&file, "").expect("write");

        watcher.watch(
            &file,
            WatchMode {
                recursive_mode: RecursiveMode::NonRecursive,
                target_mode: TargetMode::NoTrack,
            },
        );

        std::fs::remove_file(&file).expect("remove");

        rx.wait_ordered_exact([
            expected(&file).modify_meta_any(),
            expected(&file).remove_file(),
        ]);
        assert_eq!(watcher.get_watch_handles(), HashSet::from([]));

        std::fs::write(&file, "").expect("write");

        rx.ensure_empty_with_wait();
    }

    #[test]
    fn create_write_overwrite() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        let overwritten_file = tmpdir.path().join("overwritten_file");
        let overwriting_file = tmpdir.path().join("overwriting_file");
        std::fs::write(&overwritten_file, "123").expect("write1");

        watcher.watch_nonrecursively(&tmpdir);

        std::fs::File::create(&overwriting_file).expect("create");
        std::fs::write(&overwriting_file, "321").expect("write2");
        std::fs::rename(&overwriting_file, &overwritten_file).expect("rename");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&overwriting_file).create_file(),
            expected(&overwriting_file).access_open_any(),
            expected(&overwriting_file).access_close_write(),
            expected(&overwriting_file).access_open_any(),
            expected(&overwriting_file).modify_data_any().multiple(),
            expected(&overwriting_file).access_close_write().multiple(),
            expected(&overwriting_file).rename_from(),
            expected(&overwritten_file).rename_to(),
            expected([&overwriting_file, &overwritten_file]).rename_both(),
        ])
        .ensure_no_tail()
        .ensure_trackers_len(1);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn create_self_write_overwrite() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        let overwritten_file = tmpdir.path().join("overwritten_file");
        let overwriting_file = tmpdir.path().join("overwriting_file");
        std::fs::write(&overwritten_file, "123").expect("write1");

        watcher.watch_nonrecursively(&overwritten_file);

        std::fs::File::create(&overwriting_file).expect("create");
        std::fs::write(&overwriting_file, "321").expect("write2");
        std::fs::rename(&overwriting_file, &overwritten_file).expect("rename");

        rx.wait_ordered_exact([expected(&overwritten_file).rename_to()])
            .ensure_no_tail()
            .ensure_trackers_len(1);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn create_self_write_overwrite_no_track() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        let overwritten_file = tmpdir.path().join("overwritten_file");
        let overwriting_file = tmpdir.path().join("overwriting_file");
        std::fs::write(&overwritten_file, "123").expect("write1");

        watcher.watch(
            &overwritten_file,
            WatchMode {
                recursive_mode: RecursiveMode::NonRecursive,
                target_mode: TargetMode::NoTrack,
            },
        );

        std::fs::File::create(&overwriting_file).expect("create");
        std::fs::write(&overwriting_file, "321").expect("write2");
        std::fs::rename(&overwriting_file, &overwritten_file).expect("rename");

        rx.wait_ordered_exact([
            expected(&overwritten_file).modify_meta_any(),
            expected(&overwritten_file).remove_file(),
        ])
        .ensure_no_tail()
        .ensure_trackers_len(0);
        assert_eq!(watcher.get_watch_handles(), HashSet::from([]));
    }

    #[test]
    fn create_dir() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();
        watcher.watch_recursively(&tmpdir);

        let path = tmpdir.path().join("entry");
        std::fs::create_dir(&path).expect("create");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).create_folder(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf(), path])
        );
    }

    #[test]
    fn chmod_dir() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::create_dir(&path).expect("create_dir");
        let mut permissions = std::fs::metadata(&path).expect("metadata").permissions();
        permissions.set_readonly(true);

        watcher.watch_recursively(&tmpdir);
        std::fs::set_permissions(&path, permissions).expect("set_permissions");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).access_open_any().optional(),
            expected(&path).modify_meta_any(),
            expected(&path).modify_meta_any(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf(), path])
        );
    }

    #[test]
    fn rename_dir() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        let new_path = tmpdir.path().join("new_path");
        std::fs::create_dir(&path).expect("create_dir");

        watcher.watch_recursively(&tmpdir);

        std::fs::rename(&path, &new_path).expect("rename");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).access_open_any().optional(),
            expected(&path).rename_from(),
            expected(&new_path).rename_to(),
            expected([&path, &new_path]).rename_both(),
        ])
        .ensure_trackers_len(1);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf(), new_path])
        );
    }

    #[test]
    fn delete_dir() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::create_dir(&path).expect("create_dir");

        watcher.watch_recursively(&tmpdir);
        std::fs::remove_dir(&path).expect("remove");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).access_open_any().optional(),
            expected(&path).remove_folder(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn delete_self_dir() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::create_dir(&path).expect("create_dir");

        watcher.watch_recursively(&path);
        std::fs::remove_dir(&path).expect("remove");

        rx.wait_ordered_exact([
            expected(&path).access_open_any().optional(),
            expected(&path).remove_folder(),
            expected(&path).access_open_any().optional(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );

        std::fs::create_dir(&path).expect("create_dir2");

        rx.wait_ordered_exact([
            expected(&path).access_open_any().optional(),
            expected(&path).create_folder(),
            expected(&path).access_open_any().optional(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf(), path.clone()])
        );
    }

    #[test]
    fn delete_self_dir_no_track() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::create_dir(&path).expect("create_dir");

        watcher
            .watcher
            .watch(
                &path,
                WatchMode {
                    recursive_mode: RecursiveMode::Recursive,
                    target_mode: TargetMode::NoTrack,
                },
            )
            .expect("watch");
        std::fs::remove_dir(&path).expect("remove");

        rx.wait_ordered_exact([expected(&path).remove_folder()])
            .ensure_no_tail();
        assert_eq!(watcher.get_watch_handles(), HashSet::from([]));

        std::fs::create_dir(&path).expect("create_dir2");

        rx.ensure_empty_with_wait();
    }

    #[test]
    fn rename_dir_twice() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        let new_path = tmpdir.path().join("new_path");
        let new_path2 = tmpdir.path().join("new_path2");
        std::fs::create_dir(&path).expect("create_dir");

        watcher.watch_recursively(&tmpdir);
        std::fs::rename(&path, &new_path).expect("rename");
        std::fs::rename(&new_path, &new_path2).expect("rename2");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).access_open_any().optional(),
            expected(&path).rename_from(),
            expected(&new_path).rename_to(),
            expected([&path, &new_path]).rename_both(),
            expected(&new_path).access_open_any().optional(),
            expected(&new_path).rename_from(),
            expected(&new_path2).rename_to(),
            expected([&new_path, &new_path2]).rename_both(),
        ])
        .ensure_trackers_len(2);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf(), new_path2])
        );
    }

    #[test]
    fn move_out_of_watched_dir() {
        let tmpdir = testdir();
        let subdir = tmpdir.path().join("subdir");
        let (mut watcher, mut rx) = watcher();

        let path = subdir.join("entry");
        std::fs::create_dir_all(&subdir).expect("create_dir_all");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch_recursively(&subdir);
        let new_path = tmpdir.path().join("entry");

        std::fs::rename(&path, &new_path).expect("rename");

        rx.wait_ordered_exact([
            expected(&subdir).access_open_any(),
            expected(&path).rename_from(),
        ])
        .ensure_trackers_len(1)
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf(), subdir])
        );
    }

    #[test]
    fn create_write_write_rename_write_remove() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let file1 = tmpdir.path().join("entry");
        let file2 = tmpdir.path().join("entry2");
        std::fs::File::create_new(&file2).expect("create file2");
        let new_path = tmpdir.path().join("renamed");

        watcher.watch_recursively(&tmpdir);
        std::fs::write(&file1, "123").expect("write 1");
        std::fs::write(&file2, "321").expect("write 2");
        std::fs::rename(&file1, &new_path).expect("rename");
        std::fs::write(&new_path, b"1").expect("write 3");
        std::fs::remove_file(&new_path).expect("remove");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&file1).create_file(),
            expected(&file1).access_open_any(),
            expected(&file1).modify_data_any().multiple(),
            expected(&file1).access_close_write(),
            expected(&file2).access_open_any(),
            expected(&file2).modify_data_any().multiple(),
            expected(&file2).access_close_write(),
            expected(&file1).access_open_any().optional(),
            expected(&file1).rename_from(),
            expected(&new_path).rename_to(),
            expected([&file1, &new_path]).rename_both(),
            expected(&new_path).access_open_any(),
            expected(&new_path).modify_data_any().multiple(),
            expected(&new_path).access_close_write(),
            expected(&new_path).remove_file(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn rename_twice() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch_recursively(&tmpdir);
        let new_path1 = tmpdir.path().join("renamed1");
        let new_path2 = tmpdir.path().join("renamed2");

        std::fs::rename(&path, &new_path1).expect("rename1");
        std::fs::rename(&new_path1, &new_path2).expect("rename2");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).access_open_any().optional(),
            expected(&path).rename_from(),
            expected(&new_path1).rename_to(),
            expected([&path, &new_path1]).rename_both(),
            expected(&new_path1).access_open_any().optional(),
            expected(&new_path1).rename_from(),
            expected(&new_path2).rename_to(),
            expected([&new_path1, &new_path2]).rename_both(),
        ])
        .ensure_no_tail()
        .ensure_trackers_len(2);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn set_file_mtime() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        let file = std::fs::File::create_new(&path).expect("create");

        watcher.watch_recursively(&tmpdir);

        file.set_modified(
            std::time::SystemTime::now()
                .checked_sub(Duration::from_secs(60 * 60))
                .expect("time"),
        )
        .expect("set_time");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&path).modify_data_any(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn write_file_non_recursive_watch() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("entry");
        std::fs::File::create_new(&path).expect("create");

        watcher.watch_nonrecursively(&path);

        std::fs::write(&path, b"123").expect("write");

        rx.wait_ordered_exact([
            expected(&path).access_open_any(),
            expected(&path).modify_data_any().multiple(),
            expected(&path).access_close_write(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf()])
        );
    }

    #[test]
    fn watch_recursively_then_unwatch_child_stops_events_from_child() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let subdir = tmpdir.path().join("subdir");
        let file = subdir.join("file");
        std::fs::create_dir(&subdir).expect("create");

        watcher.watch_recursively(&tmpdir);

        std::fs::File::create(&file).expect("create");

        rx.wait_ordered_exact([
            expected(tmpdir.path()).access_open_any().optional(),
            expected(&subdir).access_open_any().optional(),
            expected(&file).create_file(),
            expected(&file).access_open_any(),
            expected(&file).access_close_write(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.parent_path_buf(), tmpdir.to_path_buf(), subdir])
        );

        // TODO: https://github.com/rolldown/notify/issues/8
        // watcher.watcher.unwatch(&subdir).expect("unwatch");

        // std::fs::write(&file, b"123").expect("write");

        // std::fs::remove_dir_all(&subdir).expect("remove_dir_all");

        // rx.wait_ordered_exact([
        //     expected(&subdir).access_open_any().optional(),
        //     expected(&subdir).remove_folder(),
        // ])
        // .ensure_no_tail();
    }

    #[test]
    fn write_to_a_hardlink_pointed_to_the_watched_file_triggers_an_event() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let subdir = tmpdir.path().join("subdir");
        let subdir2 = tmpdir.path().join("subdir2");
        let file = subdir.join("file");
        let hardlink = subdir2.join("hardlink");

        std::fs::create_dir(&subdir).expect("create");
        std::fs::create_dir(&subdir2).expect("create2");
        std::fs::write(&file, "").expect("file");
        std::fs::hard_link(&file, &hardlink).expect("hardlink");

        watcher.watch_nonrecursively(&file);

        std::fs::write(&hardlink, "123123").expect("write to the hard link");

        rx.wait_ordered_exact([
            expected(&file).access_open_any(),
            expected(&file).modify_data_any().multiple(),
            expected(&file).access_close_write(),
        ]);
        assert_eq!(watcher.get_watch_handles(), HashSet::from([subdir, file]));
    }

    #[test]
    fn write_to_a_hardlink_pointed_to_the_watched_file_triggers_an_event_even_if_the_parent_is_watched()
     {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let subdir1 = tmpdir.path().join("subdir1");
        let subdir2 = subdir1.join("subdir2");
        let file = subdir2.join("file");
        let hardlink = tmpdir.path().join("hardlink");

        std::fs::create_dir_all(&subdir2).expect("create");
        std::fs::write(&file, "").expect("file");
        std::fs::hard_link(&file, &hardlink).expect("hardlink");

        watcher.watch_nonrecursively(&subdir2);
        watcher.watch_nonrecursively(&file);

        std::fs::write(&hardlink, "123123").expect("write to the hard link");

        rx.wait_ordered_exact([
            expected(&subdir2).access_open_any().optional(),
            expected(&file).access_open_any(),
            expected(&file).modify_data_any().multiple(),
            expected(&file).access_close_write(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([subdir1, subdir2, file])
        );
    }

    #[test]
    fn write_to_a_hardlink_pointed_to_the_file_in_the_watched_dir_doesnt_trigger_an_event() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let subdir = tmpdir.path().join("subdir");
        let subdir2 = tmpdir.path().join("subdir2");
        let file = subdir.join("file");
        let hardlink = subdir2.join("hardlink");

        std::fs::create_dir(&subdir).expect("create");
        std::fs::create_dir(&subdir2).expect("create");
        std::fs::write(&file, "").expect("file");
        std::fs::hard_link(&file, &hardlink).expect("hardlink");

        watcher.watch_nonrecursively(&subdir);

        std::fs::write(&hardlink, "123123").expect("write to the hard link");

        rx.wait_ordered_exact([expected(&subdir).access_open_any().optional()])
            .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf(), subdir])
        );
    }

    #[test]
    #[ignore = "see https://github.com/notify-rs/notify/issues/727"]
    fn recursive_creation() {
        let tmpdir = testdir();
        let nested1 = tmpdir.path().join("1");
        let nested2 = tmpdir.path().join("1/2");
        let nested3 = tmpdir.path().join("1/2/3");
        let nested4 = tmpdir.path().join("1/2/3/4");
        let nested5 = tmpdir.path().join("1/2/3/4/5");
        let nested6 = tmpdir.path().join("1/2/3/4/5/6");
        let nested7 = tmpdir.path().join("1/2/3/4/5/6/7");
        let nested8 = tmpdir.path().join("1/2/3/4/5/6/7/8");
        let nested9 = tmpdir.path().join("1/2/3/4/5/6/7/8/9");

        let (mut watcher, mut rx) = watcher();

        watcher.watch_recursively(&tmpdir);

        std::fs::create_dir_all(&nested9).expect("create_dir_all");
        rx.wait_ordered([
            expected(&nested1).create_folder(),
            expected(&nested2).create_folder(),
            expected(&nested3).create_folder(),
            expected(&nested4).create_folder(),
            expected(&nested5).create_folder(),
            expected(&nested6).create_folder(),
            expected(&nested7).create_folder(),
            expected(&nested8).create_folder(),
            expected(&nested9).create_folder(),
        ]);
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([
                tmpdir.to_path_buf(),
                nested1,
                nested2,
                nested3,
                nested4,
                nested5,
                nested6,
                nested7,
                nested8,
                nested9
            ])
        );
    }

    #[test]
    fn upgrade_to_recursive() {
        let tmpdir = testdir();
        let (mut watcher, mut rx) = watcher();

        let path = tmpdir.path().join("upgrade");
        let deep = tmpdir.path().join("upgrade/deep");
        let file = tmpdir.path().join("upgrade/deep/file");
        std::fs::create_dir_all(&deep).expect("create_dir");

        watcher.watch_nonrecursively(&path);
        std::fs::File::create_new(&file).expect("create");
        std::fs::remove_file(&file).expect("delete");

        rx.ensure_empty_with_wait();

        watcher.watch_recursively(&path);
        std::fs::File::create_new(&file).expect("create");

        rx.wait_ordered([
            expected(&file).create_file(),
            expected(&file).access_open_any(),
            expected(&file).access_close_write(),
        ])
        .ensure_no_tail();
        assert_eq!(
            watcher.get_watch_handles(),
            HashSet::from([tmpdir.to_path_buf(), path, deep])
        );
    }
}