mod char_bag;
mod fuzzy;

use crate::{
    editor::{History, Snapshot as BufferSnapshot},
    sum_tree::{self, Edit, SumTree},
};
use anyhow::{anyhow, Context, Result};
use fuzzy::PathEntry;
pub use fuzzy::{match_paths, PathMatch};
use gpui::{scoped_pool, AppContext, Entity, ModelContext, ModelHandle, Task};
use ignore::gitignore::Gitignore;
use parking_lot::Mutex;
use postage::{
    prelude::{Sink, Stream},
    watch,
};
use smol::{channel::Sender, Timer};
use std::{
    collections::{HashMap, HashSet},
    ffi::OsStr,
    fmt, fs,
    future::Future,
    io::{self, Read, Write},
    ops::{AddAssign, Deref},
    os::unix::fs::MetadataExt,
    path::{Path, PathBuf},
    sync::Arc,
    time::Duration,
};

const GITIGNORE: &'static str = ".gitignore";

#[derive(Clone, Debug)]
enum ScanState {
    Idle,
    Scanning,
    Err(Arc<io::Error>),
}

pub struct Worktree {
    snapshot: Snapshot,
    background_snapshot: Arc<Mutex<Snapshot>>,
    scan_state: (watch::Sender<ScanState>, watch::Receiver<ScanState>),
    _event_stream_handle: fsevent::Handle,
    poll_scheduled: bool,
}

#[derive(Clone)]
pub struct FileHandle {
    worktree: ModelHandle<Worktree>,
    inode: u64,
}

impl Worktree {
    pub fn new(path: impl Into<Arc<Path>>, ctx: &mut ModelContext<Self>) -> Self {
        let (scan_state_tx, scan_state_rx) = smol::channel::unbounded();
        let id = ctx.model_id();
        let snapshot = Snapshot {
            id,
            path: path.into(),
            root_inode: None,
            ignores: Default::default(),
            entries: Default::default(),
        };
        let (event_stream, event_stream_handle) =
            fsevent::EventStream::new(&[snapshot.path.as_ref()], Duration::from_millis(100));

        let background_snapshot = Arc::new(Mutex::new(snapshot.clone()));

        let tree = Self {
            snapshot,
            background_snapshot: background_snapshot.clone(),
            scan_state: watch::channel_with(ScanState::Scanning),
            _event_stream_handle: event_stream_handle,
            poll_scheduled: false,
        };

        std::thread::spawn(move || {
            let scanner = BackgroundScanner::new(background_snapshot, scan_state_tx, id);
            scanner.run(event_stream)
        });

        ctx.spawn_stream(scan_state_rx, Self::observe_scan_state, |_, _| {})
            .detach();

        tree
    }

    pub fn scan_complete(&self) -> impl Future<Output = ()> {
        let mut scan_state_rx = self.scan_state.1.clone();
        async move {
            let mut scan_state = Some(scan_state_rx.borrow().clone());
            while let Some(ScanState::Scanning) = scan_state {
                scan_state = scan_state_rx.recv().await;
            }
        }
    }

    pub fn next_scan_complete(&self) -> impl Future<Output = ()> {
        let mut scan_state_rx = self.scan_state.1.clone();
        let mut did_scan = matches!(*scan_state_rx.borrow(), ScanState::Scanning);
        async move {
            loop {
                if let ScanState::Scanning = *scan_state_rx.borrow() {
                    did_scan = true;
                } else if did_scan {
                    break;
                }
                scan_state_rx.recv().await;
            }
        }
    }

    fn observe_scan_state(&mut self, scan_state: ScanState, ctx: &mut ModelContext<Self>) {
        let _ = self.scan_state.0.blocking_send(scan_state);
        self.poll_entries(ctx);
    }

    fn poll_entries(&mut self, ctx: &mut ModelContext<Self>) {
        self.snapshot = self.background_snapshot.lock().clone();
        ctx.notify();

        if self.is_scanning() && !self.poll_scheduled {
            ctx.spawn(Timer::after(Duration::from_millis(100)), |this, _, ctx| {
                this.poll_scheduled = false;
                this.poll_entries(ctx);
            })
            .detach();
            self.poll_scheduled = true;
        }
    }

    fn is_scanning(&self) -> bool {
        if let ScanState::Scanning = *self.scan_state.1.borrow() {
            true
        } else {
            false
        }
    }

    pub fn snapshot(&self) -> Snapshot {
        self.snapshot.clone()
    }

    pub fn contains_path(&self, path: &Path) -> bool {
        path.starts_with(&self.snapshot.path)
    }

    pub fn has_inode(&self, inode: u64) -> bool {
        self.snapshot.entries.get(&inode).is_some()
    }

    pub fn file_count(&self) -> usize {
        self.snapshot.entries.summary().file_count
    }

    pub fn abs_path_for_inode(&self, ino: u64) -> Result<PathBuf> {
        let mut result = self.snapshot.path.to_path_buf();
        result.push(self.path_for_inode(ino, false)?);
        Ok(result)
    }

    pub fn load_history(
        &self,
        ino: u64,
        ctx: &AppContext,
    ) -> impl Future<Output = Result<History>> {
        let path = self.abs_path_for_inode(ino);
        ctx.background_executor().spawn(async move {
            let mut file = std::fs::File::open(&path?)?;
            let mut base_text = String::new();
            file.read_to_string(&mut base_text)?;
            Ok(History::new(Arc::from(base_text)))
        })
    }

    pub fn save<'a>(
        &self,
        ino: u64,
        content: BufferSnapshot,
        ctx: &AppContext,
    ) -> Task<Result<()>> {
        let path = self.abs_path_for_inode(ino);
        ctx.background_executor().spawn(async move {
            let buffer_size = content.text_summary().bytes.min(10 * 1024);
            let file = std::fs::File::create(&path?)?;
            let mut writer = std::io::BufWriter::with_capacity(buffer_size, file);
            for chunk in content.fragments() {
                writer.write(chunk.as_bytes())?;
            }
            writer.flush()?;
            Ok(())
        })
    }

    #[cfg(test)]
    pub fn files<'a>(&'a self) -> impl Iterator<Item = u64> + 'a {
        self.snapshot
            .entries
            .cursor::<(), ()>()
            .filter_map(|entry| {
                if let Entry::File { inode, .. } = entry {
                    Some(*inode)
                } else {
                    None
                }
            })
    }
}

impl Entity for Worktree {
    type Event = ();
}

impl Deref for Worktree {
    type Target = Snapshot;

    fn deref(&self) -> &Self::Target {
        &self.snapshot
    }
}

impl fmt::Debug for Worktree {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.snapshot.fmt(f)
    }
}

#[derive(Clone)]
pub struct Snapshot {
    id: usize,
    path: Arc<Path>,
    root_inode: Option<u64>,
    ignores: HashMap<u64, Gitignore>,
    entries: SumTree<Entry>,
}

impl Snapshot {
    pub fn file_count(&self) -> usize {
        self.entries.summary().file_count
    }

    pub fn root_entry(&self) -> Option<&Entry> {
        self.root_inode.and_then(|inode| self.entries.get(&inode))
    }

    pub fn root_name(&self) -> Option<&OsStr> {
        self.path.file_name()
    }

    fn entry_for_path(&self, path: impl AsRef<Path>) -> Option<&Entry> {
        self.inode_for_path(path)
            .and_then(|inode| self.entries.get(&inode))
    }

    fn inode_for_path(&self, path: impl AsRef<Path>) -> Option<u64> {
        let path = path.as_ref();
        self.root_inode.and_then(|mut inode| {
            'components: for path_component in path {
                if let Some(Entry::Dir { children, .. }) = &self.entries.get(&inode) {
                    for (child_inode, name) in children.as_ref() {
                        if name.as_ref() == path_component {
                            inode = *child_inode;
                            continue 'components;
                        }
                    }
                }
                return None;
            }
            Some(inode)
        })
    }

    pub fn is_path_ignored(&self, path: impl AsRef<Path>) -> Result<bool> {
        if let Some(inode) = self.inode_for_path(path.as_ref()) {
            self.is_inode_ignored(inode)
        } else {
            Ok(false)
        }
    }

    pub fn is_inode_ignored(&self, mut inode: u64) -> Result<bool> {
        let mut components = Vec::new();
        let mut relative_path = PathBuf::new();
        let mut entry = self
            .entries
            .get(&inode)
            .ok_or_else(|| anyhow!("entry does not exist in worktree"))?;
        while let Some(parent) = entry.parent() {
            let parent_entry = self.entries.get(&parent).unwrap();
            if let Entry::Dir { children, .. } = parent_entry {
                let (_, child_name) = children
                    .iter()
                    .find(|(child_inode, _)| *child_inode == inode)
                    .unwrap();
                components.push(child_name.as_ref());
                inode = parent;

                if let Some(ignore) = self.ignores.get(&inode) {
                    relative_path.clear();
                    relative_path.extend(components.iter().rev());
                    match ignore.matched_path_or_any_parents(&relative_path, entry.is_dir()) {
                        ignore::Match::Whitelist(_) => return Ok(false),
                        ignore::Match::Ignore(_) => return Ok(true),
                        ignore::Match::None => {}
                    }
                }
            } else {
                unreachable!();
            }
            entry = parent_entry;
        }
        Ok(false)
    }

    pub fn path_for_inode(&self, mut inode: u64, include_root: bool) -> Result<PathBuf> {
        let mut components = Vec::new();
        let mut entry = self
            .entries
            .get(&inode)
            .ok_or_else(|| anyhow!("entry does not exist in worktree"))?;
        while let Some(parent) = entry.parent() {
            entry = self.entries.get(&parent).unwrap();
            if let Entry::Dir { children, .. } = entry {
                let (_, child_name) = children
                    .iter()
                    .find(|(child_inode, _)| *child_inode == inode)
                    .unwrap();
                components.push(child_name.as_ref());
                inode = parent;
            } else {
                unreachable!();
            }
        }
        if include_root {
            components.push(self.root_name().unwrap());
        }
        Ok(components.into_iter().rev().collect())
    }

    fn insert_entry(&mut self, name: Option<&OsStr>, entry: Entry) {
        let mut edits = Vec::new();

        if let Some(old_entry) = self.entries.get(&entry.inode()) {
            // If the entry's parent changed, remove the entry from the old parent's children.
            if old_entry.parent() != entry.parent() {
                if let Some(old_parent_inode) = old_entry.parent() {
                    let old_parent = self.entries.get(&old_parent_inode).unwrap().clone();
                    self.remove_children(old_parent, &mut edits, |inode| inode == entry.inode());
                }
            }

            // Remove all descendants of the old version of the entry being inserted.
            self.clear_descendants(entry.inode(), &mut edits);
        }

        // Insert the entry in its new parent with the correct name.
        if let Some(new_parent_inode) = entry.parent() {
            let name = name.unwrap();
            if name == GITIGNORE {
                self.insert_ignore_file(new_parent_inode);
            }

            let mut new_parent = self.entries.get(&new_parent_inode).unwrap().clone();
            if let Entry::Dir { children, .. } = &mut new_parent {
                *children = children
                    .iter()
                    .filter(|(inode, _)| *inode != entry.inode())
                    .cloned()
                    .chain(Some((entry.inode(), name.into())))
                    .collect::<Vec<_>>()
                    .into();
            } else {
                unreachable!("non-directory parent");
            }
            edits.push(Edit::Insert(new_parent));
        }

        // Insert the entry itself.
        edits.push(Edit::Insert(entry));

        self.entries.edit(edits);
    }

    fn populate_dir(
        &mut self,
        parent_inode: u64,
        children: impl IntoIterator<Item = (Arc<OsStr>, Entry)>,
    ) {
        let mut edits = Vec::new();

        self.clear_descendants(parent_inode, &mut edits);

        // Determine which children are being re-parented and populate array of new children to
        // assign to the parent.
        let mut new_children = Vec::new();
        let mut old_children = HashMap::<u64, HashSet<u64>>::new();
        for (name, child) in children.into_iter() {
            if *name == *GITIGNORE {
                self.insert_ignore_file(parent_inode);
            }

            new_children.push((child.inode(), name.into()));
            if let Some(old_child) = self.entries.get(&child.inode()) {
                if let Some(old_parent_inode) = old_child.parent() {
                    if old_parent_inode != parent_inode {
                        old_children
                            .entry(old_parent_inode)
                            .or_default()
                            .insert(child.inode());
                    }
                }
            }
            edits.push(Edit::Insert(child));
        }

        // Replace the parent with a clone that includes the children and isn't pending
        let mut parent = self.entries.get(&parent_inode).unwrap().clone();
        if let Entry::Dir {
            children, pending, ..
        } = &mut parent
        {
            *children = new_children.into();
            *pending = false;
        } else {
            unreachable!("non-directory parent");
        }
        edits.push(Edit::Insert(parent));

        // For any children that were re-parented, remove them from their old parents
        for (parent_inode, to_remove) in old_children {
            let parent = self.entries.get(&parent_inode).unwrap().clone();
            self.remove_children(parent, &mut edits, |inode| to_remove.contains(&inode));
        }

        self.entries.edit(edits);
    }

    fn remove_path(&mut self, path: &Path) {
        if let Some(entry) = self.entry_for_path(path).cloned() {
            let mut edits = Vec::new();

            self.clear_descendants(entry.inode(), &mut edits);

            if let Some(parent_inode) = entry.parent() {
                if let Some(file_name) = path.file_name() {
                    if file_name == GITIGNORE {
                        self.remove_ignore_file(parent_inode);
                    }
                }
                let parent = self.entries.get(&parent_inode).unwrap().clone();
                self.remove_children(parent, &mut edits, |inode| inode == entry.inode());
            }

            edits.push(Edit::Remove(entry.inode()));

            self.entries.edit(edits);
        }
    }

    fn clear_descendants(&mut self, inode: u64, edits: &mut Vec<Edit<Entry>>) {
        let mut stack = vec![inode];
        while let Some(inode) = stack.pop() {
            let mut has_gitignore = false;
            if let Entry::Dir { children, .. } = self.entries.get(&inode).unwrap() {
                for (child_inode, child_name) in children.iter() {
                    if **child_name == *GITIGNORE {
                        has_gitignore = true;
                    }
                    edits.push(Edit::Remove(*child_inode));
                    stack.push(*child_inode);
                }
            }
            if has_gitignore {
                self.remove_ignore_file(inode);
            }
        }
    }

    fn remove_children(
        &mut self,
        mut parent: Entry,
        edits: &mut Vec<Edit<Entry>>,
        predicate: impl Fn(u64) -> bool,
    ) {
        if let Entry::Dir { children, .. } = &mut parent {
            *children = children
                .iter()
                .filter(|(inode, _)| !predicate(*inode))
                .cloned()
                .collect::<Vec<_>>()
                .into();
        } else {
            unreachable!("non-directory parent");
        }
        edits.push(Edit::Insert(parent));
    }

    fn insert_ignore_file(&mut self, dir_inode: u64) {
        let mut path = self.path.to_path_buf();
        path.push(self.path_for_inode(dir_inode, false).unwrap());
        path.push(GITIGNORE);
        let (ignore, err) = Gitignore::new(&path);
        if let Some(err) = err {
            log::info!("error in ignore file {:?} - {:?}", path, err);
        }

        self.ignores.insert(dir_inode, ignore);
    }

    fn remove_ignore_file(&mut self, dir_inode: u64) {
        self.ignores.remove(&dir_inode);
    }

    fn fmt_entry(
        &self,
        f: &mut fmt::Formatter<'_>,
        ino: u64,
        name: &OsStr,
        indent: usize,
    ) -> fmt::Result {
        match self.entries.get(&ino).unwrap() {
            Entry::Dir { children, .. } => {
                write!(
                    f,
                    "{}{}/ ({})\n",
                    " ".repeat(indent),
                    name.to_string_lossy(),
                    ino
                )?;
                for (child_inode, child_name) in children.iter() {
                    self.fmt_entry(f, *child_inode, child_name, indent + 2)?;
                }
                Ok(())
            }
            Entry::File { .. } => write!(
                f,
                "{}{} ({})\n",
                " ".repeat(indent),
                name.to_string_lossy(),
                ino
            ),
        }
    }
}

impl fmt::Debug for Snapshot {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if let Some(root_ino) = self.root_inode {
            self.fmt_entry(f, root_ino, self.path.file_name().unwrap(), 0)
        } else {
            write!(f, "Empty tree\n")
        }
    }
}

impl FileHandle {
    pub fn path(&self, ctx: &AppContext) -> PathBuf {
        self.worktree
            .read(ctx)
            .path_for_inode(self.inode, false)
            .unwrap()
    }

    pub fn load_history(&self, ctx: &AppContext) -> impl Future<Output = Result<History>> {
        self.worktree.read(ctx).load_history(self.inode, ctx)
    }

    pub fn save<'a>(&self, content: BufferSnapshot, ctx: &AppContext) -> Task<Result<()>> {
        let worktree = self.worktree.read(ctx);
        worktree.save(self.inode, content, ctx)
    }

    pub fn entry_id(&self) -> (usize, u64) {
        (self.worktree.id(), self.inode)
    }
}

#[derive(Clone, Debug)]
pub enum Entry {
    Dir {
        inode: u64,
        parent: Option<u64>,
        is_symlink: bool,
        children: Arc<[(u64, Arc<OsStr>)]>,
        pending: bool,
    },
    File {
        inode: u64,
        parent: Option<u64>,
        is_symlink: bool,
        path: PathEntry,
    },
}

impl Entry {
    fn inode(&self) -> u64 {
        match self {
            Entry::Dir { inode, .. } => *inode,
            Entry::File { inode, .. } => *inode,
        }
    }

    fn is_dir(&self) -> bool {
        matches!(self, Entry::Dir { .. })
    }

    fn parent(&self) -> Option<u64> {
        match self {
            Entry::Dir { parent, .. } => *parent,
            Entry::File { parent, .. } => *parent,
        }
    }
}

impl sum_tree::Item for Entry {
    type Summary = EntrySummary;

    fn summary(&self) -> Self::Summary {
        EntrySummary {
            max_ino: self.inode(),
            file_count: if matches!(self, Self::File { .. }) {
                1
            } else {
                0
            },
        }
    }
}

impl sum_tree::KeyedItem for Entry {
    type Key = u64;

    fn key(&self) -> Self::Key {
        self.inode()
    }
}

#[derive(Clone, Debug, Default)]
pub struct EntrySummary {
    max_ino: u64,
    file_count: usize,
}

impl<'a> AddAssign<&'a EntrySummary> for EntrySummary {
    fn add_assign(&mut self, rhs: &'a EntrySummary) {
        self.max_ino = rhs.max_ino;
        self.file_count += rhs.file_count;
    }
}

impl<'a> sum_tree::Dimension<'a, EntrySummary> for u64 {
    fn add_summary(&mut self, summary: &'a EntrySummary) {
        *self = summary.max_ino;
    }
}

#[derive(Copy, Clone, Default, Debug, Eq, PartialEq, Ord, PartialOrd)]
struct FileCount(usize);

impl<'a> sum_tree::Dimension<'a, EntrySummary> for FileCount {
    fn add_summary(&mut self, summary: &'a EntrySummary) {
        self.0 += summary.file_count;
    }
}

struct BackgroundScanner {
    snapshot: Arc<Mutex<Snapshot>>,
    notify: Sender<ScanState>,
    thread_pool: scoped_pool::Pool,
}

impl BackgroundScanner {
    fn new(snapshot: Arc<Mutex<Snapshot>>, notify: Sender<ScanState>, worktree_id: usize) -> Self {
        Self {
            snapshot,
            notify,
            thread_pool: scoped_pool::Pool::new(16, format!("worktree-{}-scanner", worktree_id)),
        }
    }

    fn path(&self) -> Arc<Path> {
        self.snapshot.lock().path.clone()
    }

    fn snapshot(&self) -> Snapshot {
        self.snapshot.lock().clone()
    }

    fn run(self, event_stream: fsevent::EventStream) {
        if smol::block_on(self.notify.send(ScanState::Scanning)).is_err() {
            return;
        }

        if let Err(err) = self.scan_dirs() {
            if smol::block_on(self.notify.send(ScanState::Err(Arc::new(err)))).is_err() {
                return;
            }
        }

        if smol::block_on(self.notify.send(ScanState::Idle)).is_err() {
            return;
        }

        event_stream.run(move |events| {
            if smol::block_on(self.notify.send(ScanState::Scanning)).is_err() {
                return false;
            }

            if !self.process_events(events) {
                return false;
            }

            if smol::block_on(self.notify.send(ScanState::Idle)).is_err() {
                return false;
            }

            true
        });
    }

    fn scan_dirs(&self) -> io::Result<()> {
        let path = self.path();
        let metadata = fs::metadata(&path)?;
        let inode = metadata.ino();
        let is_symlink = fs::symlink_metadata(&path)?.file_type().is_symlink();
        let name = Arc::from(path.file_name().unwrap_or(OsStr::new("/")));
        let relative_path = PathBuf::from(&name);

        if metadata.file_type().is_dir() {
            let dir_entry = Entry::Dir {
                parent: None,
                inode,
                is_symlink,
                children: Arc::from([]),
                pending: true,
            };

            {
                let mut snapshot = self.snapshot.lock();
                snapshot.insert_entry(None, dir_entry);
                snapshot.root_inode = Some(inode);
            }

            let (tx, rx) = crossbeam_channel::unbounded();

            tx.send(Ok(ScanJob {
                inode,
                path: path.clone(),
                relative_path,
                scan_queue: tx.clone(),
            }))
            .unwrap();
            drop(tx);

            let mut results = Vec::new();
            results.resize_with(self.thread_pool.thread_count(), || Ok(()));
            self.thread_pool.scoped(|pool| {
                for result in &mut results {
                    pool.execute(|| {
                        let result = result;
                        while let Ok(job) = rx.recv() {
                            if let Err(err) = job.and_then(|job| self.scan_dir(job)) {
                                *result = Err(err);
                                break;
                            }
                        }
                    });
                }
            });
            results.into_iter().collect::<io::Result<()>>()?;
        } else {
            let mut snapshot = self.snapshot.lock();
            snapshot.insert_entry(
                None,
                Entry::File {
                    parent: None,
                    path: PathEntry::new(inode, &relative_path),
                    inode,
                    is_symlink,
                },
            );
            snapshot.root_inode = Some(inode);
        }

        Ok(())
    }

    fn scan_dir(&self, job: ScanJob) -> io::Result<()> {
        let scan_queue = job.scan_queue;

        let mut new_entries = Vec::new();
        let mut new_jobs = Vec::new();

        for child_entry in fs::read_dir(&job.path)? {
            let child_entry = child_entry?;
            let child_name: Arc<OsStr> = child_entry.file_name().into();
            let child_relative_path = job.relative_path.join(child_name.as_ref());
            let child_metadata = child_entry.metadata()?;
            let child_inode = child_metadata.ino();
            let child_is_symlink = child_metadata.file_type().is_symlink();
            let child_path = job.path.join(child_name.as_ref());

            if child_metadata.is_dir() {
                new_entries.push((
                    child_name,
                    Entry::Dir {
                        parent: Some(job.inode),
                        inode: child_inode,
                        is_symlink: child_is_symlink,
                        children: Arc::from([]),
                        pending: true,
                    },
                ));
                new_jobs.push(ScanJob {
                    inode: child_inode,
                    path: Arc::from(child_path),
                    relative_path: child_relative_path,
                    scan_queue: scan_queue.clone(),
                });
            } else {
                new_entries.push((
                    child_name,
                    Entry::File {
                        parent: Some(job.inode),
                        path: PathEntry::new(child_inode, &child_relative_path),
                        inode: child_inode,
                        is_symlink: child_is_symlink,
                    },
                ));
            };
        }

        self.snapshot.lock().populate_dir(job.inode, new_entries);
        for new_job in new_jobs {
            scan_queue.send(Ok(new_job)).unwrap();
        }

        Ok(())
    }

    fn process_events(&self, mut events: Vec<fsevent::Event>) -> bool {
        let mut snapshot = self.snapshot();
        let root_path = if let Ok(path) = snapshot.path.canonicalize() {
            path
        } else {
            return false;
        };

        events.sort_unstable_by(|a, b| a.path.cmp(&b.path));
        let mut paths = events.into_iter().map(|e| e.path).peekable();
        let (scan_queue_tx, scan_queue_rx) = crossbeam_channel::unbounded();
        while let Some(path) = paths.next() {
            let relative_path = match path.strip_prefix(&root_path) {
                Ok(relative_path) => relative_path.to_path_buf(),
                Err(_) => {
                    log::error!("unexpected event {:?} for root path {:?}", path, root_path);
                    continue;
                }
            };

            while paths.peek().map_or(false, |p| p.starts_with(&path)) {
                paths.next();
            }

            snapshot.remove_path(&relative_path);

            match self.fs_entry_for_path(&root_path, &path) {
                Ok(Some(fs_entry)) => {
                    let is_dir = fs_entry.is_dir();
                    let inode = fs_entry.inode();

                    snapshot.insert_entry(path.file_name(), fs_entry);
                    if is_dir {
                        scan_queue_tx
                            .send(Ok(ScanJob {
                                inode,
                                path: Arc::from(path),
                                relative_path: snapshot
                                    .root_name()
                                    .map_or(PathBuf::new(), PathBuf::from)
                                    .join(relative_path),
                                scan_queue: scan_queue_tx.clone(),
                            }))
                            .unwrap();
                    }
                }
                Ok(None) => {}
                Err(err) => {
                    // TODO - create a special 'error' entry in the entries tree to mark this
                    log::error!("error reading file on event {:?}", err);
                }
            }
        }

        *self.snapshot.lock() = snapshot;

        // Scan any directories that were created as part of this event batch.
        drop(scan_queue_tx);
        self.thread_pool.scoped(|pool| {
            for _ in 0..self.thread_pool.thread_count() {
                pool.execute(|| {
                    while let Ok(job) = scan_queue_rx.recv() {
                        if let Err(err) = job.and_then(|job| self.scan_dir(job)) {
                            log::error!("Error scanning {:?}", err);
                        }
                    }
                });
            }
        });

        true
    }

    fn fs_entry_for_path(&self, root_path: &Path, path: &Path) -> Result<Option<Entry>> {
        let metadata = match fs::metadata(&path) {
            Err(err) => {
                return match (err.kind(), err.raw_os_error()) {
                    (io::ErrorKind::NotFound, _) => Ok(None),
                    (io::ErrorKind::Other, Some(libc::ENOTDIR)) => Ok(None),
                    _ => Err(anyhow::Error::new(err)),
                }
            }
            Ok(metadata) => metadata,
        };

        let inode = metadata.ino();
        let is_symlink = fs::symlink_metadata(&path)
            .context("failed to read symlink metadata")?
            .file_type()
            .is_symlink();
        let parent = if path == root_path {
            None
        } else {
            Some(
                fs::metadata(path.parent().unwrap())
                    .context("failed to read parent inode")?
                    .ino(),
            )
        };

        let entry = if metadata.file_type().is_dir() {
            Entry::Dir {
                inode,
                parent,
                is_symlink,
                pending: true,
                children: Arc::from([]),
            }
        } else {
            Entry::File {
                inode,
                parent,
                is_symlink,
                path: PathEntry::new(
                    inode,
                    root_path
                        .parent()
                        .map_or(path, |parent| path.strip_prefix(parent).unwrap()),
                ),
            }
        };

        Ok(Some(entry))
    }
}

struct ScanJob {
    inode: u64,
    path: Arc<Path>,
    relative_path: PathBuf,
    scan_queue: crossbeam_channel::Sender<io::Result<ScanJob>>,
}

pub trait WorktreeHandle {
    fn file(&self, entry_id: u64, app: &AppContext) -> Result<FileHandle>;
}

impl WorktreeHandle for ModelHandle<Worktree> {
    fn file(&self, inode: u64, app: &AppContext) -> Result<FileHandle> {
        if self.read(app).has_inode(inode) {
            Ok(FileHandle {
                worktree: self.clone(),
                inode,
            })
        } else {
            Err(anyhow!("entry does not exist in tree"))
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::editor::Buffer;
    use crate::test::*;
    use anyhow::Result;
    use gpui::App;
    use rand::prelude::*;
    use serde_json::json;
    use std::env;
    use std::os::unix;
    use std::time::{SystemTime, UNIX_EPOCH};

    #[test]
    fn test_populate_and_search() {
        App::test_async((), |mut app| async move {
            let dir = temp_tree(json!({
                "root": {
                    "apple": "",
                    "banana": {
                        "carrot": {
                            "date": "",
                            "endive": "",
                        }
                    },
                    "fennel": {
                        "grape": "",
                    }
                }
            }));

            let root_link_path = dir.path().join("root_link");
            unix::fs::symlink(&dir.path().join("root"), &root_link_path).unwrap();

            let tree = app.add_model(|ctx| Worktree::new(root_link_path, ctx));

            app.read(|ctx| tree.read(ctx).scan_complete()).await;
            app.read(|ctx| {
                let tree = tree.read(ctx);
                assert_eq!(tree.file_count(), 4);
                let results = match_paths(
                    Some(tree.snapshot()).iter(),
                    "bna",
                    false,
                    false,
                    false,
                    10,
                    ctx.thread_pool().clone(),
                )
                .iter()
                .map(|result| tree.path_for_inode(result.entry_id, true))
                .collect::<Result<Vec<PathBuf>, _>>()
                .unwrap();
                assert_eq!(
                    results,
                    vec![
                        PathBuf::from("root_link/banana/carrot/date"),
                        PathBuf::from("root_link/banana/carrot/endive"),
                    ]
                );
            })
        });

        eprintln!("HI");
    }

    #[test]
    fn test_save_file() {
        App::test_async((), |mut app| async move {
            let dir = temp_tree(json!({
                "file1": "the old contents",
            }));

            let tree = app.add_model(|ctx| Worktree::new(dir.path(), ctx));
            app.read(|ctx| tree.read(ctx).scan_complete()).await;
            app.read(|ctx| assert_eq!(tree.read(ctx).file_count(), 1));

            let buffer = Buffer::new(1, "a line of text.\n".repeat(10 * 1024));

            let file_inode = app.read(|ctx| {
                let tree = tree.read(ctx);
                let inode = tree.files().next().unwrap();
                assert_eq!(
                    tree.path_for_inode(inode, false)
                        .unwrap()
                        .file_name()
                        .unwrap(),
                    "file1"
                );
                inode
            });

            tree.update(&mut app, |tree, ctx| {
                smol::block_on(tree.save(file_inode, buffer.snapshot(), ctx.as_ref())).unwrap()
            });

            let loaded_history = app
                .read(|ctx| tree.read(ctx).load_history(file_inode, ctx))
                .await
                .unwrap();
            assert_eq!(loaded_history.base_text.as_ref(), buffer.text());
        });
    }

    #[test]
    fn test_rescan() {
        App::test_async((), |mut app| async move {
            let dir = temp_tree(json!({
                "a": {
                    "file1": "",
                },
                "b": {
                    "c": {
                        "file2": "",
                    }
                }
            }));

            let tree = app.add_model(|ctx| Worktree::new(dir.path(), ctx));
            app.read(|ctx| tree.read(ctx).scan_complete()).await;
            app.read(|ctx| assert_eq!(tree.read(ctx).file_count(), 2));

            let file2 = app.read(|ctx| {
                let inode = tree.read(ctx).inode_for_path("b/c/file2").unwrap();
                let file2 = tree.file(inode, ctx).unwrap();
                assert_eq!(file2.path(ctx), Path::new("b/c/file2"));
                file2
            });

            std::fs::rename(dir.path().join("b/c"), dir.path().join("d")).unwrap();
            tree.condition(&app, move |_, ctx| file2.path(ctx) == Path::new("d/file2"))
                .await;
        });
    }

    #[test]
    fn test_rescan_with_gitignore() {
        App::test_async((), |mut app| async move {
            let dir = temp_tree(json!({
                ".git": {},
                ".gitignore": "ignored-dir\n",
                "tracked-dir": {
                    "tracked-file1": "tracked contents",
                },
                "ignored-dir": {
                    "ignored-file1": "ignored contents",
                }
            }));

            let tree = app.add_model(|ctx| Worktree::new(dir.path(), ctx));
            app.read(|ctx| tree.read(ctx).scan_complete()).await;
            app.read(|ctx| {
                let tree = tree.read(ctx);
                assert!(!tree.is_path_ignored("tracked-dir/tracked-file1").unwrap());
                assert!(tree.is_path_ignored("ignored-dir/ignored-file1").unwrap());
            });

            fs::write(dir.path().join("tracked-dir/tracked-file2"), "").unwrap();
            fs::write(dir.path().join("ignored-dir/ignored-file2"), "").unwrap();
            app.read(|ctx| tree.read(ctx).next_scan_complete()).await;
            app.read(|ctx| {
                let tree = tree.read(ctx);
                assert!(!tree.is_path_ignored("tracked-dir/tracked-file2").unwrap());
                assert!(tree.is_path_ignored("ignored-dir/ignored-file2").unwrap());
            });
        });
    }

    #[test]
    fn test_random() {
        let iterations = env::var("ITERATIONS")
            .map(|i| i.parse().unwrap())
            .unwrap_or(100);
        let operations = env::var("OPERATIONS")
            .map(|o| o.parse().unwrap())
            .unwrap_or(40);
        let initial_entries = env::var("INITIAL_ENTRIES")
            .map(|o| o.parse().unwrap())
            .unwrap_or(20);
        let seeds = if let Ok(seed) = env::var("SEED").map(|s| s.parse().unwrap()) {
            seed..seed + 1
        } else {
            0..iterations
        };

        for seed in seeds {
            dbg!(seed);
            let mut rng = StdRng::seed_from_u64(seed);

            let root_dir = tempdir::TempDir::new(&format!("test-{}", seed)).unwrap();
            for _ in 0..initial_entries {
                randomly_mutate_tree(root_dir.path(), 1.0, &mut rng).unwrap();
            }
            log::info!("Generated initial tree");

            let (notify_tx, _notify_rx) = smol::channel::unbounded();
            let scanner = BackgroundScanner::new(
                Arc::new(Mutex::new(Snapshot {
                    id: 0,
                    path: root_dir.path().into(),
                    root_inode: None,
                    entries: Default::default(),
                    ignores: Default::default(),
                })),
                notify_tx,
                0,
            );
            scanner.scan_dirs().unwrap();

            let mut events = Vec::new();
            let mut mutations_len = operations;
            while mutations_len > 1 {
                if !events.is_empty() && rng.gen_bool(0.4) {
                    let len = rng.gen_range(0..=events.len());
                    let to_deliver = events.drain(0..len).collect::<Vec<_>>();
                    log::info!("Delivering events: {:#?}", to_deliver);
                    scanner.process_events(to_deliver);
                } else {
                    events.extend(randomly_mutate_tree(root_dir.path(), 0.6, &mut rng).unwrap());
                    mutations_len -= 1;
                }
            }
            log::info!("Quiescing: {:#?}", events);
            scanner.process_events(events);

            let (notify_tx, _notify_rx) = smol::channel::unbounded();
            let new_scanner = BackgroundScanner::new(
                Arc::new(Mutex::new(Snapshot {
                    id: 0,
                    path: root_dir.path().into(),
                    root_inode: None,
                    entries: Default::default(),
                    ignores: Default::default(),
                })),
                notify_tx,
                1,
            );
            new_scanner.scan_dirs().unwrap();
            scanner.snapshot().check_invariants();
            assert_eq!(scanner.snapshot().to_vec(), new_scanner.snapshot().to_vec());
        }
    }

    fn randomly_mutate_tree(
        root_path: &Path,
        insertion_probability: f64,
        rng: &mut impl Rng,
    ) -> Result<Vec<fsevent::Event>> {
        let root_path = root_path.canonicalize().unwrap();
        let (dirs, files) = read_dir_recursive(root_path.clone());

        let mut events = Vec::new();
        let mut record_event = |path: PathBuf| {
            events.push(fsevent::Event {
                event_id: SystemTime::now()
                    .duration_since(UNIX_EPOCH)
                    .unwrap()
                    .as_secs(),
                flags: fsevent::StreamFlags::empty(),
                path,
            });
        };

        if (files.is_empty() && dirs.len() == 1) || rng.gen_bool(insertion_probability) {
            let path = dirs.choose(rng).unwrap();
            let new_path = path.join(gen_name(rng));

            if rng.gen() {
                log::info!("Creating dir {:?}", new_path.strip_prefix(root_path)?);
                fs::create_dir(&new_path)?;
            } else {
                log::info!("Creating file {:?}", new_path.strip_prefix(root_path)?);
                fs::write(&new_path, "")?;
            }
            record_event(new_path);
        } else {
            let old_path = {
                let file_path = files.choose(rng);
                let dir_path = dirs[1..].choose(rng);
                file_path.into_iter().chain(dir_path).choose(rng).unwrap()
            };

            let is_rename = rng.gen();
            if is_rename {
                let new_path_parent = dirs
                    .iter()
                    .filter(|d| !d.starts_with(old_path))
                    .choose(rng)
                    .unwrap();

                let overwrite_existing_dir =
                    !old_path.starts_with(&new_path_parent) && rng.gen_bool(0.3);
                let new_path = if overwrite_existing_dir {
                    fs::remove_dir_all(&new_path_parent).ok();
                    new_path_parent.to_path_buf()
                } else {
                    new_path_parent.join(gen_name(rng))
                };

                log::info!(
                    "Renaming {:?} to {}{:?}",
                    old_path.strip_prefix(&root_path)?,
                    if overwrite_existing_dir {
                        "overwrite "
                    } else {
                        ""
                    },
                    new_path.strip_prefix(&root_path)?
                );
                fs::rename(&old_path, &new_path)?;
                record_event(old_path.clone());
                record_event(new_path);
            } else if old_path.is_dir() {
                let (dirs, files) = read_dir_recursive(old_path.clone());

                log::info!("Deleting dir {:?}", old_path.strip_prefix(&root_path)?);
                fs::remove_dir_all(&old_path).unwrap();
                for file in files {
                    record_event(file);
                }
                for dir in dirs {
                    record_event(dir);
                }
            } else {
                log::info!("Deleting file {:?}", old_path.strip_prefix(&root_path)?);
                fs::remove_file(old_path).unwrap();
                record_event(old_path.clone());
            }
        }

        Ok(events)
    }

    fn read_dir_recursive(path: PathBuf) -> (Vec<PathBuf>, Vec<PathBuf>) {
        let child_entries = fs::read_dir(&path).unwrap();
        let mut dirs = vec![path];
        let mut files = Vec::new();
        for child_entry in child_entries {
            let child_path = child_entry.unwrap().path();
            if child_path.is_dir() {
                let (child_dirs, child_files) = read_dir_recursive(child_path);
                dirs.extend(child_dirs);
                files.extend(child_files);
            } else {
                files.push(child_path);
            }
        }
        (dirs, files)
    }

    fn gen_name(rng: &mut impl Rng) -> String {
        (0..6)
            .map(|_| rng.sample(rand::distributions::Alphanumeric))
            .map(char::from)
            .collect()
    }

    impl Snapshot {
        fn check_invariants(&self) {
            for entry in self.entries.items() {
                let path = self.path_for_inode(entry.inode(), false).unwrap();
                assert_eq!(self.inode_for_path(path).unwrap(), entry.inode());
            }
        }

        fn to_vec(&self) -> Vec<(PathBuf, u64)> {
            use std::iter::FromIterator;

            let mut paths = Vec::new();

            let mut stack = Vec::new();
            stack.extend(self.root_inode);
            while let Some(inode) = stack.pop() {
                let computed_path = self.path_for_inode(inode, true).unwrap();
                match self.entries.get(&inode).unwrap() {
                    Entry::Dir { children, .. } => {
                        stack.extend(children.iter().map(|c| c.0));
                    }
                    Entry::File { path, .. } => {
                        assert_eq!(
                            String::from_iter(path.path.iter()),
                            computed_path.to_str().unwrap()
                        );
                    }
                }
                paths.push((computed_path, inode));
            }

            assert_eq!(paths.len(), self.entries.items().len());
            paths.sort_by(|a, b| a.0.cmp(&b.0));
            paths
        }
    }
}