pub mod fs_watcher;

pub use fs_watcher::requires_poll_watcher;

use parking_lot::Mutex;
use std::ffi::OsString;
use std::sync::atomic::{AtomicU8, AtomicUsize, Ordering};
use std::time::Instant;
use util::maybe;

use anyhow::{Context as _, Result, anyhow};
use futures::stream::iter;
use gpui::App;
use gpui::BackgroundExecutor;
use gpui::Global;
use gpui::ReadGlobal as _;
use gpui::SharedString;
#[cfg(unix)]
use std::ffi::CString;
use util::command::new_command;

#[cfg(unix)]
use std::os::fd::{AsFd, AsRawFd};
#[cfg(unix)]
use std::os::unix::ffi::OsStrExt;

#[cfg(unix)]
use std::os::unix::fs::{FileTypeExt, MetadataExt};

#[cfg(any(target_os = "macos", target_os = "freebsd"))]
use std::mem::MaybeUninit;

use async_tar::Archive;
use futures::{AsyncRead, Stream, StreamExt, future::BoxFuture};
use git::repository::{GitRepository, RealGitRepository};
use is_executable::IsExecutable;
use rope::Rope;
use serde::{Deserialize, Serialize};
use smol::io::AsyncWriteExt;
#[cfg(feature = "test-support")]
use std::path::Component;
use std::{
    io::{self, Write},
    path::{Path, PathBuf},
    pin::Pin,
    sync::Arc,
    time::{Duration, SystemTime, UNIX_EPOCH},
};
use tempfile::TempDir;
use text::LineEnding;

#[cfg(feature = "test-support")]
mod fake_git_repo;
#[cfg(feature = "test-support")]
use collections::{BTreeMap, btree_map};
#[cfg(feature = "test-support")]
use fake_git_repo::{FakeCommitDataEntry, FakeGitRepositoryState};
#[cfg(feature = "test-support")]
use git::{
    repository::{CommitData, InitialGraphCommitData, RepoPath, Worktree, repo_path},
    status::{FileStatus, StatusCode, TrackedStatus, UnmergedStatus},
};
#[cfg(feature = "test-support")]
use util::normalize_path;

#[cfg(feature = "test-support")]
use smol::io::AsyncReadExt;
#[cfg(feature = "test-support")]
use std::ffi::OsStr;

pub trait Watcher: Send + Sync {
    fn add(&self, path: &Path) -> Result<()>;
    fn remove(&self, path: &Path) -> Result<()>;
}

#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub enum PathEventKind {
    Removed,
    Created,
    Changed,
    Rescan,
}

#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub struct PathEvent {
    pub path: PathBuf,
    pub kind: Option<PathEventKind>,
}

impl From<PathEvent> for PathBuf {
    fn from(event: PathEvent) -> Self {
        event.path
    }
}

#[async_trait::async_trait]
pub trait Fs: Send + Sync {
    async fn create_dir(&self, path: &Path) -> Result<()>;
    async fn create_symlink(&self, path: &Path, target: PathBuf) -> Result<()>;
    async fn create_file(&self, path: &Path, options: CreateOptions) -> Result<()>;
    async fn create_file_with(
        &self,
        path: &Path,
        content: Pin<&mut (dyn AsyncRead + Send)>,
    ) -> Result<()>;
    async fn extract_tar_file(
        &self,
        path: &Path,
        content: Archive<Pin<&mut (dyn AsyncRead + Send)>>,
    ) -> Result<()>;
    async fn copy_file(&self, source: &Path, target: &Path, options: CopyOptions) -> Result<()>;
    async fn rename(&self, source: &Path, target: &Path, options: RenameOptions) -> Result<()>;

    /// Removes a directory from the filesystem.
    /// There is no expectation that the directory will be preserved in the
    /// system trash.
    async fn remove_dir(&self, path: &Path, options: RemoveOptions) -> Result<()>;

    /// Moves a file or directory to the system trash.
    /// Returns a [`TrashedEntry`] that can be used to keep track of the
    /// location of the trashed item in the system's trash.
    async fn trash(&self, path: &Path, options: RemoveOptions) -> Result<TrashedEntry>;

    /// Removes a file from the filesystem.
    /// There is no expectation that the file will be preserved in the system
    /// trash.
    async fn remove_file(&self, path: &Path, options: RemoveOptions) -> Result<()>;

    async fn open_handle(&self, path: &Path) -> Result<Arc<dyn FileHandle>>;
    async fn open_sync(&self, path: &Path) -> Result<Box<dyn io::Read + Send + Sync>>;
    async fn load(&self, path: &Path) -> Result<String> {
        Ok(String::from_utf8(self.load_bytes(path).await?)?)
    }
    async fn load_bytes(&self, path: &Path) -> Result<Vec<u8>>;
    async fn atomic_write(&self, path: PathBuf, text: String) -> Result<()>;
    async fn save(&self, path: &Path, text: &Rope, line_ending: LineEnding) -> Result<()>;
    async fn write(&self, path: &Path, content: &[u8]) -> Result<()>;
    async fn canonicalize(&self, path: &Path) -> Result<PathBuf>;
    async fn is_file(&self, path: &Path) -> bool;
    async fn is_dir(&self, path: &Path) -> bool;
    async fn metadata(&self, path: &Path) -> Result<Option<Metadata>>;
    async fn read_link(&self, path: &Path) -> Result<PathBuf>;
    async fn read_dir(
        &self,
        path: &Path,
    ) -> Result<Pin<Box<dyn Send + Stream<Item = Result<PathBuf>>>>>;

    async fn watch(
        &self,
        path: &Path,
        latency: Duration,
    ) -> (
        Pin<Box<dyn Send + Stream<Item = Vec<PathEvent>>>>,
        Arc<dyn Watcher>,
    );

    fn open_repo(
        &self,
        abs_dot_git: &Path,
        system_git_binary_path: Option<&Path>,
    ) -> Result<Arc<dyn GitRepository>>;
    async fn git_init(&self, abs_work_directory: &Path, fallback_branch_name: String)
    -> Result<()>;
    async fn git_clone(&self, abs_work_directory: &Path, repo_url: &str) -> Result<()>;
    async fn git_config(&self, abs_work_directory: &Path, args: Vec<String>) -> Result<String>;
    fn is_fake(&self) -> bool;
    async fn is_case_sensitive(&self) -> bool;
    fn subscribe_to_jobs(&self) -> JobEventReceiver;

    /// Restores a given `TrashedEntry`, moving it from the system's trash back
    /// to the original path.
    async fn restore(
        &self,
        trashed_entry: TrashedEntry,
    ) -> std::result::Result<PathBuf, TrashRestoreError>;

    #[cfg(feature = "test-support")]
    fn as_fake(&self) -> Arc<FakeFs> {
        panic!("called as_fake on a real fs");
    }
}

// We use our own type rather than `trash::TrashItem` directly to avoid carrying
// over fields we don't need (e.g. `time_deleted`) and to insulate callers and
// tests from changes to that crate's API surface.
/// Represents a file or directory that has been moved to the system trash,
/// retaining enough information to restore it to its original location.
#[derive(Clone, PartialEq, Debug)]
pub struct TrashedEntry {
    /// Platform-specific identifier for the file/directory in the trash.
    ///
    /// * Freedesktop – Path to the `.trashinfo` file.
    /// * macOS & Windows – Full path to the file/directory in the system's
    /// trash.
    pub id: OsString,
    /// Name of the file/directory at the time of trashing, including extension.
    pub name: OsString,
    /// Absolute path to the parent directory at the time of trashing.
    pub original_parent: PathBuf,
}

impl From<trash::TrashItem> for TrashedEntry {
    fn from(item: trash::TrashItem) -> Self {
        Self {
            id: item.id,
            name: item.name,
            original_parent: item.original_parent,
        }
    }
}

impl TrashedEntry {
    fn into_trash_item(self) -> trash::TrashItem {
        trash::TrashItem {
            id: self.id,
            name: self.name,
            original_parent: self.original_parent,
            // `TrashedEntry` doesn't preserve `time_deleted` as we don't
            // currently need it for restore, so we default it to 0 here.
            time_deleted: 0,
        }
    }
}

#[derive(Debug, thiserror::Error)]
pub enum TrashRestoreError {
    #[error("The specified `path` ({}) was not found in the system's trash.", path.display())]
    NotFound { path: PathBuf },
    #[error("File or directory ({}) already exists at the restore destination.", path.display())]
    Collision { path: PathBuf },
    #[error("Unknown error ({description})")]
    Unknown { description: String },
}

impl From<trash::Error> for TrashRestoreError {
    fn from(err: trash::Error) -> Self {
        match err {
            trash::Error::RestoreCollision { path, .. } => Self::Collision { path },
            trash::Error::Unknown { description } => Self::Unknown { description },
            other => Self::Unknown {
                description: other.to_string(),
            },
        }
    }
}

struct GlobalFs(Arc<dyn Fs>);

impl Global for GlobalFs {}

impl dyn Fs {
    /// Returns the global [`Fs`].
    pub fn global(cx: &App) -> Arc<Self> {
        GlobalFs::global(cx).0.clone()
    }

    /// Sets the global [`Fs`].
    pub fn set_global(fs: Arc<Self>, cx: &mut App) {
        cx.set_global(GlobalFs(fs));
    }
}

#[derive(Copy, Clone, Default)]
pub struct CreateOptions {
    pub overwrite: bool,
    pub ignore_if_exists: bool,
}

#[derive(Copy, Clone, Default)]
pub struct CopyOptions {
    pub overwrite: bool,
    pub ignore_if_exists: bool,
}

#[derive(Copy, Clone, Default)]
pub struct RenameOptions {
    pub overwrite: bool,
    pub ignore_if_exists: bool,
    /// Whether to create parent directories if they do not exist.
    pub create_parents: bool,
}

#[derive(Copy, Clone, Default)]
pub struct RemoveOptions {
    pub recursive: bool,
    pub ignore_if_not_exists: bool,
}

#[derive(Copy, Clone, Debug)]
pub struct Metadata {
    pub inode: u64,
    pub mtime: MTime,
    pub is_symlink: bool,
    pub is_dir: bool,
    pub len: u64,
    pub is_fifo: bool,
    pub is_executable: bool,
}

/// Filesystem modification time. The purpose of this newtype is to discourage use of operations
/// that do not make sense for mtimes. In particular, it is not always valid to compare mtimes using
/// `<` or `>`, as there are many things that can cause the mtime of a file to be earlier than it
/// was. See ["mtime comparison considered harmful" - apenwarr](https://apenwarr.ca/log/20181113).
///
/// Do not derive Ord, PartialOrd, or arithmetic operation traits.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Deserialize, Serialize)]
#[serde(transparent)]
pub struct MTime(SystemTime);

pub type JobId = usize;

#[derive(Clone, Debug)]
pub struct JobInfo {
    pub start: Instant,
    pub message: SharedString,
    pub id: JobId,
}

#[derive(Debug, Clone)]
pub enum JobEvent {
    Started { info: JobInfo },
    Completed { id: JobId },
}

pub type JobEventSender = futures::channel::mpsc::UnboundedSender<JobEvent>;
pub type JobEventReceiver = futures::channel::mpsc::UnboundedReceiver<JobEvent>;

struct JobTracker {
    id: JobId,
    subscribers: Arc<Mutex<Vec<JobEventSender>>>,
}

impl JobTracker {
    fn new(info: JobInfo, subscribers: Arc<Mutex<Vec<JobEventSender>>>) -> Self {
        let id = info.id;
        {
            let mut subs = subscribers.lock();
            subs.retain(|sender| {
                sender
                    .unbounded_send(JobEvent::Started { info: info.clone() })
                    .is_ok()
            });
        }
        Self { id, subscribers }
    }
}

impl Drop for JobTracker {
    fn drop(&mut self) {
        let mut subs = self.subscribers.lock();
        subs.retain(|sender| {
            sender
                .unbounded_send(JobEvent::Completed { id: self.id })
                .is_ok()
        });
    }
}

impl MTime {
    /// Conversion intended for persistence and testing.
    pub fn from_seconds_and_nanos(secs: u64, nanos: u32) -> Self {
        MTime(UNIX_EPOCH + Duration::new(secs, nanos))
    }

    /// Conversion intended for persistence.
    pub fn to_seconds_and_nanos_for_persistence(self) -> Option<(u64, u32)> {
        self.0
            .duration_since(UNIX_EPOCH)
            .ok()
            .map(|duration| (duration.as_secs(), duration.subsec_nanos()))
    }

    /// Returns the value wrapped by this `MTime`, for presentation to the user. The name including
    /// "_for_user" is to discourage misuse - this method should not be used when making decisions
    /// about file dirtiness.
    pub fn timestamp_for_user(self) -> SystemTime {
        self.0
    }

    /// Temporary method to split out the behavior changes from introduction of this newtype.
    pub fn bad_is_greater_than(self, other: MTime) -> bool {
        self.0 > other.0
    }
}

impl From<proto::Timestamp> for MTime {
    fn from(timestamp: proto::Timestamp) -> Self {
        MTime(timestamp.into())
    }
}

impl From<MTime> for proto::Timestamp {
    fn from(mtime: MTime) -> Self {
        mtime.0.into()
    }
}

pub struct RealFs {
    bundled_git_binary_path: Option<PathBuf>,
    executor: BackgroundExecutor,
    next_job_id: Arc<AtomicUsize>,
    job_event_subscribers: Arc<Mutex<Vec<JobEventSender>>>,
    is_case_sensitive: AtomicU8,
}

pub trait FileHandle: Send + Sync + std::fmt::Debug {
    fn current_path(&self, fs: &Arc<dyn Fs>) -> Result<PathBuf>;
}

impl FileHandle for std::fs::File {
    #[cfg(target_os = "macos")]
    fn current_path(&self, _: &Arc<dyn Fs>) -> Result<PathBuf> {
        use std::{
            ffi::{CStr, OsStr},
            os::unix::ffi::OsStrExt,
        };

        let fd = self.as_fd();
        let mut path_buf = MaybeUninit::<[u8; libc::PATH_MAX as usize]>::uninit();

        let result = unsafe { libc::fcntl(fd.as_raw_fd(), libc::F_GETPATH, path_buf.as_mut_ptr()) };
        anyhow::ensure!(result != -1, "fcntl returned -1");

        // SAFETY: `fcntl` will initialize the path buffer.
        let c_str = unsafe { CStr::from_ptr(path_buf.as_ptr().cast()) };
        anyhow::ensure!(!c_str.is_empty(), "Could find a path for the file handle");
        let path = PathBuf::from(OsStr::from_bytes(c_str.to_bytes()));
        Ok(path)
    }

    #[cfg(target_os = "linux")]
    fn current_path(&self, _: &Arc<dyn Fs>) -> Result<PathBuf> {
        let fd = self.as_fd();
        let fd_path = format!("/proc/self/fd/{}", fd.as_raw_fd());
        let new_path = std::fs::read_link(fd_path)?;
        if new_path
            .file_name()
            .is_some_and(|f| f.to_string_lossy().ends_with(" (deleted)"))
        {
            anyhow::bail!("file was deleted")
        };

        Ok(new_path)
    }

    #[cfg(target_os = "freebsd")]
    fn current_path(&self, _: &Arc<dyn Fs>) -> Result<PathBuf> {
        use std::{
            ffi::{CStr, OsStr},
            os::unix::ffi::OsStrExt,
        };

        let fd = self.as_fd();
        let mut kif = MaybeUninit::<libc::kinfo_file>::uninit();
        kif.kf_structsize = libc::KINFO_FILE_SIZE;

        let result = unsafe { libc::fcntl(fd.as_raw_fd(), libc::F_KINFO, kif.as_mut_ptr()) };
        anyhow::ensure!(result != -1, "fcntl returned -1");

        // SAFETY: `fcntl` will initialize the kif.
        let c_str = unsafe { CStr::from_ptr(kif.assume_init().kf_path.as_ptr()) };
        anyhow::ensure!(!c_str.is_empty(), "Could find a path for the file handle");
        let path = PathBuf::from(OsStr::from_bytes(c_str.to_bytes()));
        Ok(path)
    }

    #[cfg(target_os = "windows")]
    fn current_path(&self, _: &Arc<dyn Fs>) -> Result<PathBuf> {
        use std::ffi::OsString;
        use std::os::windows::ffi::OsStringExt;
        use std::os::windows::io::AsRawHandle;

        use windows::Win32::Foundation::HANDLE;
        use windows::Win32::Storage::FileSystem::{
            FILE_NAME_NORMALIZED, GetFinalPathNameByHandleW,
        };

        let handle = HANDLE(self.as_raw_handle() as _);

        // Query required buffer size (in wide chars)
        let required_len =
            unsafe { GetFinalPathNameByHandleW(handle, &mut [], FILE_NAME_NORMALIZED) };
        anyhow::ensure!(
            required_len != 0,
            "GetFinalPathNameByHandleW returned 0 length"
        );

        // Allocate buffer and retrieve the path
        let mut buf: Vec<u16> = vec![0u16; required_len as usize + 1];
        let written = unsafe { GetFinalPathNameByHandleW(handle, &mut buf, FILE_NAME_NORMALIZED) };
        anyhow::ensure!(
            written != 0,
            "GetFinalPathNameByHandleW failed to write path"
        );

        let os_str: OsString = OsString::from_wide(&buf[..written as usize]);
        anyhow::ensure!(!os_str.is_empty(), "Could find a path for the file handle");
        Ok(PathBuf::from(os_str))
    }
}

pub struct RealWatcher {}

impl RealFs {
    pub fn new(git_binary_path: Option<PathBuf>, executor: BackgroundExecutor) -> Self {
        Self {
            bundled_git_binary_path: git_binary_path,
            executor,
            next_job_id: Arc::new(AtomicUsize::new(0)),
            job_event_subscribers: Arc::new(Mutex::new(Vec::new())),
            is_case_sensitive: Default::default(),
        }
    }

    #[cfg(target_os = "windows")]
    fn canonicalize(path: &Path) -> Result<PathBuf> {
        use std::ffi::OsString;
        use std::os::windows::ffi::OsStringExt;
        use windows::Win32::Storage::FileSystem::GetVolumePathNameW;
        use windows::core::HSTRING;

        // std::fs::canonicalize resolves mapped network paths to UNC paths, which can
        // confuse some software. To mitigate this, we canonicalize the input, then rebase
        // the result onto the input's original volume root if both paths are on the same
        // volume. This keeps the same drive letter or mount point the caller used.

        let abs_path = if path.is_relative() {
            std::env::current_dir()?.join(path)
        } else {
            path.to_path_buf()
        };

        let path_hstring = HSTRING::from(abs_path.as_os_str());
        let mut vol_buf = vec![0u16; abs_path.as_os_str().len() + 2];
        unsafe { GetVolumePathNameW(&path_hstring, &mut vol_buf)? };
        let volume_root = {
            let len = vol_buf
                .iter()
                .position(|&c| c == 0)
                .unwrap_or(vol_buf.len());
            PathBuf::from(OsString::from_wide(&vol_buf[..len]))
        };

        let resolved_path = dunce::canonicalize(&abs_path)?;
        let resolved_root = dunce::canonicalize(&volume_root)?;

        if let Ok(relative) = resolved_path.strip_prefix(&resolved_root) {
            let mut result = volume_root;
            result.push(relative);
            Ok(result)
        } else {
            Ok(resolved_path)
        }
    }
}

#[cfg(any(target_os = "macos", target_os = "linux"))]
fn rename_without_replace(source: &Path, target: &Path) -> io::Result<()> {
    let source = path_to_c_string(source)?;
    let target = path_to_c_string(target)?;

    #[cfg(target_os = "macos")]
    let result = unsafe { libc::renamex_np(source.as_ptr(), target.as_ptr(), libc::RENAME_EXCL) };

    #[cfg(target_os = "linux")]
    let result = unsafe {
        libc::syscall(
            libc::SYS_renameat2,
            libc::AT_FDCWD,
            source.as_ptr(),
            libc::AT_FDCWD,
            target.as_ptr(),
            libc::RENAME_NOREPLACE,
        )
    };

    if result == 0 {
        Ok(())
    } else {
        Err(io::Error::last_os_error())
    }
}

#[cfg(target_os = "windows")]
fn rename_without_replace(source: &Path, target: &Path) -> io::Result<()> {
    use std::os::windows::ffi::OsStrExt;

    use windows::Win32::Storage::FileSystem::{MOVE_FILE_FLAGS, MoveFileExW};
    use windows::core::PCWSTR;

    let source: Vec<u16> = source.as_os_str().encode_wide().chain(Some(0)).collect();
    let target: Vec<u16> = target.as_os_str().encode_wide().chain(Some(0)).collect();

    unsafe {
        MoveFileExW(
            PCWSTR(source.as_ptr()),
            PCWSTR(target.as_ptr()),
            MOVE_FILE_FLAGS::default(),
        )
    }
    .map_err(|_| io::Error::last_os_error())
}

#[cfg(any(target_os = "macos", target_os = "linux"))]
fn path_to_c_string(path: &Path) -> io::Result<CString> {
    CString::new(path.as_os_str().as_bytes()).map_err(|_| {
        io::Error::new(
            io::ErrorKind::InvalidInput,
            format!("path contains interior NUL: {}", path.display()),
        )
    })
}

#[async_trait::async_trait]
impl Fs for RealFs {
    async fn create_dir(&self, path: &Path) -> Result<()> {
        Ok(smol::fs::create_dir_all(path).await?)
    }

    async fn create_symlink(&self, path: &Path, target: PathBuf) -> Result<()> {
        #[cfg(unix)]
        smol::fs::unix::symlink(target, path).await?;

        #[cfg(windows)]
        if smol::fs::metadata(&target).await?.is_dir() {
            let status = new_command("cmd")
                .args(["/C", "mklink", "/J"])
                .args([path, target.as_path()])
                .status()
                .await?;

            if !status.success() {
                return Err(anyhow::anyhow!(
                    "Failed to create junction from {:?} to {:?}",
                    path,
                    target
                ));
            }
        } else {
            smol::fs::windows::symlink_file(target, path).await?
        }

        Ok(())
    }

    async fn create_file(&self, path: &Path, options: CreateOptions) -> Result<()> {
        let mut open_options = smol::fs::OpenOptions::new();
        open_options.write(true).create(true);
        if options.overwrite {
            open_options.truncate(true);
        } else if !options.ignore_if_exists {
            open_options.create_new(true);
        }
        open_options
            .open(path)
            .await
            .with_context(|| format!("Failed to create file at {:?}", path))?;
        Ok(())
    }

    async fn create_file_with(
        &self,
        path: &Path,
        content: Pin<&mut (dyn AsyncRead + Send)>,
    ) -> Result<()> {
        let mut file = smol::fs::File::create(&path)
            .await
            .with_context(|| format!("Failed to create file at {:?}", path))?;
        futures::io::copy(content, &mut file).await?;
        Ok(())
    }

    async fn extract_tar_file(
        &self,
        path: &Path,
        content: Archive<Pin<&mut (dyn AsyncRead + Send)>>,
    ) -> Result<()> {
        content.unpack(path).await?;
        Ok(())
    }

    async fn copy_file(&self, source: &Path, target: &Path, options: CopyOptions) -> Result<()> {
        if !options.overwrite && smol::fs::metadata(target).await.is_ok() {
            if options.ignore_if_exists {
                return Ok(());
            } else {
                anyhow::bail!("{target:?} already exists");
            }
        }

        smol::fs::copy(source, target).await?;
        Ok(())
    }

    async fn rename(&self, source: &Path, target: &Path, options: RenameOptions) -> Result<()> {
        if options.create_parents {
            if let Some(parent) = target.parent() {
                self.create_dir(parent).await?;
            }
        }

        if options.overwrite {
            smol::fs::rename(source, target).await?;
            return Ok(());
        }

        let use_metadata_fallback = {
            #[cfg(any(target_os = "macos", target_os = "linux", target_os = "windows"))]
            {
                let source = source.to_path_buf();
                let target = target.to_path_buf();
                match self
                    .executor
                    .spawn(async move { rename_without_replace(&source, &target) })
                    .await
                {
                    Ok(()) => return Ok(()),
                    Err(error) if error.kind() == io::ErrorKind::AlreadyExists => {
                        if options.ignore_if_exists {
                            return Ok(());
                        }
                        return Err(error.into());
                    }
                    Err(error)
                        if error.raw_os_error().is_some_and(|code| {
                            code == libc::ENOSYS
                                || code == libc::ENOTSUP
                                || code == libc::EOPNOTSUPP
                                || code == libc::EINVAL
                        }) =>
                    {
                        // For case when filesystem or kernel does not support atomic no-overwrite rename.
                        // EINVAL is returned by FUSE-based filesystems (e.g. NTFS via ntfs-3g)
                        // that don't support RENAME_NOREPLACE.
                        true
                    }
                    Err(error) => return Err(error.into()),
                }
            }

            #[cfg(not(any(target_os = "macos", target_os = "linux", target_os = "windows")))]
            {
                // For platforms which do not have an atomic no-overwrite rename yet.
                true
            }
        };

        if use_metadata_fallback && smol::fs::metadata(target).await.is_ok() {
            if options.ignore_if_exists {
                return Ok(());
            } else {
                anyhow::bail!("{target:?} already exists");
            }
        }

        smol::fs::rename(source, target).await?;
        Ok(())
    }

    async fn remove_dir(&self, path: &Path, options: RemoveOptions) -> Result<()> {
        let result = if options.recursive {
            smol::fs::remove_dir_all(path).await
        } else {
            smol::fs::remove_dir(path).await
        };
        match result {
            Ok(()) => Ok(()),
            Err(err) if err.kind() == io::ErrorKind::NotFound && options.ignore_if_not_exists => {
                Ok(())
            }
            Err(err) => Err(err)?,
        }
    }

    async fn remove_file(&self, path: &Path, options: RemoveOptions) -> Result<()> {
        #[cfg(windows)]
        if let Ok(Some(metadata)) = self.metadata(path).await
            && metadata.is_symlink
            && metadata.is_dir
        {
            self.remove_dir(
                path,
                RemoveOptions {
                    recursive: false,
                    ignore_if_not_exists: true,
                },
            )
            .await?;
            return Ok(());
        }

        match smol::fs::remove_file(path).await {
            Ok(()) => Ok(()),
            Err(err) if err.kind() == io::ErrorKind::NotFound && options.ignore_if_not_exists => {
                Ok(())
            }
            Err(err) => Err(err)?,
        }
    }

    async fn trash(&self, path: &Path, _options: RemoveOptions) -> Result<TrashedEntry> {
        // We must make the path absolute or trash will make a weird abomination
        // of the zed working directory (not usually the worktree) and whatever
        // the path variable holds.
        let path = self
            .canonicalize(path)
            .await
            .context("Could not canonicalize the path of the file")?;

        let (tx, rx) = futures::channel::oneshot::channel();
        std::thread::Builder::new()
            .name("trash file or dir".to_string())
            .spawn(|| tx.send(trash::delete_with_info(path)))
            .expect("The os can spawn threads");

        Ok(rx
            .await
            .context("Tx dropped or fs.restore panicked")?
            .context("Could not trash file or dir")?
            .into())
    }

    async fn open_sync(&self, path: &Path) -> Result<Box<dyn io::Read + Send + Sync>> {
        Ok(Box::new(std::fs::File::open(path)?))
    }

    async fn open_handle(&self, path: &Path) -> Result<Arc<dyn FileHandle>> {
        let mut options = std::fs::OpenOptions::new();
        options.read(true);
        #[cfg(windows)]
        {
            use std::os::windows::fs::OpenOptionsExt;
            options.custom_flags(windows::Win32::Storage::FileSystem::FILE_FLAG_BACKUP_SEMANTICS.0);
        }
        Ok(Arc::new(options.open(path)?))
    }

    async fn load(&self, path: &Path) -> Result<String> {
        let path = path.to_path_buf();
        self.executor
            .spawn(async move {
                std::fs::read_to_string(&path)
                    .with_context(|| format!("Failed to read file {}", path.display()))
            })
            .await
    }

    async fn load_bytes(&self, path: &Path) -> Result<Vec<u8>> {
        let path = path.to_path_buf();
        let bytes = self
            .executor
            .spawn(async move { std::fs::read(path) })
            .await?;
        Ok(bytes)
    }

    #[cfg(not(target_os = "windows"))]
    async fn atomic_write(&self, path: PathBuf, data: String) -> Result<()> {
        smol::unblock(move || {
            // Use the directory of the destination as temp dir to avoid
            // invalid cross-device link error, and XDG_CACHE_DIR for fallback.
            // See https://github.com/zed-industries/zed/pull/8437 for more details.
            let mut tmp_file =
                tempfile::NamedTempFile::new_in(path.parent().unwrap_or(paths::temp_dir()))?;
            tmp_file.write_all(data.as_bytes())?;
            tmp_file.persist(path)?;
            anyhow::Ok(())
        })
        .await?;

        Ok(())
    }

    #[cfg(target_os = "windows")]
    async fn atomic_write(&self, path: PathBuf, data: String) -> Result<()> {
        smol::unblock(move || {
            // If temp dir is set to a different drive than the destination,
            // we receive error:
            //
            // failed to persist temporary file:
            // The system cannot move the file to a different disk drive. (os error 17)
            //
            // This is because `ReplaceFileW` does not support cross volume moves.
            // See the remark section: "The backup file, replaced file, and replacement file must all reside on the same volume."
            // https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-replacefilew#remarks
            //
            // So we use the directory of the destination as a temp dir to avoid it.
            // https://github.com/zed-industries/zed/issues/16571
            let temp_dir = TempDir::new_in(path.parent().unwrap_or(paths::temp_dir()))?;
            let temp_file = {
                let temp_file_path = temp_dir.path().join("temp_file");
                let mut file = std::fs::File::create_new(&temp_file_path)?;
                file.write_all(data.as_bytes())?;
                temp_file_path
            };
            atomic_replace(path.as_path(), temp_file.as_path())?;
            anyhow::Ok(())
        })
        .await?;
        Ok(())
    }

    async fn save(&self, path: &Path, text: &Rope, line_ending: LineEnding) -> Result<()> {
        let buffer_size = text.summary().len.min(10 * 1024);
        if let Some(path) = path.parent() {
            self.create_dir(path)
                .await
                .with_context(|| format!("Failed to create directory at {:?}", path))?;
        }
        let file = smol::fs::File::create(path)
            .await
            .with_context(|| format!("Failed to create file at {:?}", path))?;
        let mut writer = smol::io::BufWriter::with_capacity(buffer_size, file);
        for chunk in text::chunks_with_line_ending(text, line_ending) {
            writer.write_all(chunk.as_bytes()).await?;
        }
        writer.flush().await?;
        Ok(())
    }

    async fn write(&self, path: &Path, content: &[u8]) -> Result<()> {
        if let Some(path) = path.parent() {
            self.create_dir(path)
                .await
                .with_context(|| format!("Failed to create directory at {:?}", path))?;
        }
        let path = path.to_owned();
        let contents = content.to_owned();
        self.executor
            .spawn(async move {
                std::fs::write(path, contents)?;
                Ok(())
            })
            .await
    }

    async fn canonicalize(&self, path: &Path) -> Result<PathBuf> {
        let path = path.to_owned();
        self.executor
            .spawn(async move {
                #[cfg(target_os = "windows")]
                let result = Self::canonicalize(&path);

                #[cfg(not(target_os = "windows"))]
                let result = std::fs::canonicalize(&path);

                result.with_context(|| format!("canonicalizing {path:?}"))
            })
            .await
    }

    async fn is_file(&self, path: &Path) -> bool {
        let path = path.to_owned();
        self.executor
            .spawn(async move { std::fs::metadata(path).is_ok_and(|metadata| metadata.is_file()) })
            .await
    }

    async fn is_dir(&self, path: &Path) -> bool {
        let path = path.to_owned();
        self.executor
            .spawn(async move { std::fs::metadata(path).is_ok_and(|metadata| metadata.is_dir()) })
            .await
    }

    async fn metadata(&self, path: &Path) -> Result<Option<Metadata>> {
        let path_buf = path.to_owned();
        let symlink_metadata = match self
            .executor
            .spawn(async move { std::fs::symlink_metadata(&path_buf) })
            .await
        {
            Ok(metadata) => metadata,
            Err(err) => {
                return match err.kind() {
                    io::ErrorKind::NotFound | io::ErrorKind::NotADirectory => Ok(None),
                    _ => Err(anyhow::Error::new(err)),
                };
            }
        };

        let is_symlink = symlink_metadata.file_type().is_symlink();
        let metadata = if is_symlink {
            let path_buf = path.to_path_buf();
            // Read target metadata, if the target exists
            match self
                .executor
                .spawn(async move { std::fs::metadata(path_buf) })
                .await
            {
                Ok(target_metadata) => target_metadata,
                Err(err) => {
                    if err.kind() != io::ErrorKind::NotFound {
                        // TODO: Also FilesystemLoop when that's stable
                        log::warn!(
                            "Failed to read symlink target metadata for path {path:?}: {err}"
                        );
                    }
                    // For a broken or recursive symlink, return the symlink metadata. (Or
                    // as edge cases, a symlink into a directory we can't read, which is hard
                    // to distinguish from just being broken.)
                    symlink_metadata
                }
            }
        } else {
            symlink_metadata
        };

        #[cfg(unix)]
        let inode = metadata.ino();

        #[cfg(windows)]
        let inode = file_id(path).await?;

        #[cfg(windows)]
        let is_fifo = false;

        #[cfg(unix)]
        let is_fifo = metadata.file_type().is_fifo();

        let path_buf = path.to_path_buf();
        let is_executable = self
            .executor
            .spawn(async move { path_buf.is_executable() })
            .await;

        Ok(Some(Metadata {
            inode,
            mtime: MTime(metadata.modified().unwrap_or(SystemTime::UNIX_EPOCH)),
            len: metadata.len(),
            is_symlink,
            is_dir: metadata.file_type().is_dir(),
            is_fifo,
            is_executable,
        }))
    }

    async fn read_link(&self, path: &Path) -> Result<PathBuf> {
        let path = path.to_owned();
        let path = self
            .executor
            .spawn(async move { std::fs::read_link(&path) })
            .await?;
        Ok(path)
    }

    async fn read_dir(
        &self,
        path: &Path,
    ) -> Result<Pin<Box<dyn Send + Stream<Item = Result<PathBuf>>>>> {
        let path = path.to_owned();
        let result = iter(
            self.executor
                .spawn(async move { std::fs::read_dir(path) })
                .await?,
        )
        .map(|entry| match entry {
            Ok(entry) => Ok(entry.path()),
            Err(error) => Err(anyhow!("failed to read dir entry {error:?}")),
        });
        Ok(Box::pin(result))
    }

    async fn watch(
        &self,
        path: &Path,
        latency: Duration,
    ) -> (
        Pin<Box<dyn Send + Stream<Item = Vec<PathEvent>>>>,
        Arc<dyn Watcher>,
    ) {
        use util::{ResultExt as _, paths::SanitizedPath};
        let executor = self.executor.clone();

        let (tx, rx) = async_channel::unbounded();
        let pending_paths: Arc<Mutex<Vec<PathEvent>>> = Default::default();

        let watcher: Arc<dyn Watcher> = Arc::new(fs_watcher::FsWatcher::new(
            executor.clone(),
            tx.clone(),
            pending_paths.clone(),
        ));

        if let Err(e) = watcher.add(path) {
            log::warn!("Failed to watch {}:\n{e}", path.display());
        }

        // Check if path is a symlink and follow the target parent
        if let Some(mut target) = self.read_link(path).await.ok() {
            log::trace!("watch symlink {path:?} -> {target:?}");
            // Check if symlink target is relative path, if so make it absolute
            if target.is_relative()
                && let Some(parent) = path.parent()
            {
                target = parent.join(target);
                if let Ok(canonical) = self.canonicalize(&target).await {
                    target = SanitizedPath::new(&canonical).as_path().to_path_buf();
                }
            }
            watcher.add(&target).ok();
            if let Some(parent) = target.parent() {
                watcher.add(parent).log_err();
            }
        }

        (
            Box::pin(rx.filter_map({
                let watcher = watcher.clone();
                let executor = executor.clone();
                move |_| {
                    let _ = watcher.clone();
                    let pending_paths = pending_paths.clone();
                    let executor = executor.clone();
                    async move {
                        executor.timer(latency).await;
                        let paths = std::mem::take(&mut *pending_paths.lock());
                        log::debug!("pending path events: {:?}", paths);
                        (!paths.is_empty()).then_some(paths)
                    }
                }
            })),
            watcher,
        )
    }

    fn open_repo(
        &self,
        dotgit_path: &Path,
        system_git_binary_path: Option<&Path>,
    ) -> Result<Arc<dyn GitRepository>> {
        Ok(Arc::new(RealGitRepository::new(
            dotgit_path,
            self.bundled_git_binary_path.clone(),
            system_git_binary_path.map(|path| path.to_path_buf()),
            self.executor.clone(),
        )?))
    }

    async fn git_init(
        &self,
        abs_work_directory_path: &Path,
        fallback_branch_name: String,
    ) -> Result<()> {
        let result = new_command("git")
            .current_dir(abs_work_directory_path)
            .args(&["config", "--global", "--get", "init.defaultBranch"])
            .output()
            .await;

        // In case the `git config` command fails, which would be the case if
        // the user doesn't have an `init.defaultBranch` value set, we'll just
        // default to the provided `fallback_branch_name`.
        let branch_name = match result {
            Ok(output) if !output.stdout.is_empty() => String::from_utf8(output.stdout)?,
            _ => fallback_branch_name,
        };

        new_command("git")
            .current_dir(abs_work_directory_path)
            .args(&["init", "-b"])
            .arg(branch_name.trim())
            .output()
            .await?;

        Ok(())
    }

    async fn git_clone(&self, abs_work_directory: &Path, repo_url: &str) -> Result<()> {
        let job_id = self.next_job_id.fetch_add(1, Ordering::SeqCst);
        let job_info = JobInfo {
            id: job_id,
            start: Instant::now(),
            message: SharedString::from(format!("Cloning {}", repo_url)),
        };

        let _job_tracker = JobTracker::new(job_info, self.job_event_subscribers.clone());

        let output = new_command("git")
            .current_dir(abs_work_directory)
            .args(&["clone", repo_url])
            .output()
            .await?;

        if !output.status.success() {
            anyhow::bail!(
                "git clone failed: {}",
                String::from_utf8_lossy(&output.stderr)
            );
        }

        Ok(())
    }

    /// Runs `git config` with the given arguments.
    /// Will return `Ok` if the commands exit status is `0`, with the stdout
    /// contents. Otherwise returns `Err` with the stderr contents.
    async fn git_config(&self, abs_work_directory: &Path, args: Vec<String>) -> Result<String> {
        let output = new_command("git")
            .current_dir(abs_work_directory)
            .args([String::from("config")].into_iter().chain(args))
            .output()
            .await?;

        if !output.status.success() {
            let err = String::from_utf8(output.stderr)?;
            anyhow::bail!(err);
        }

        String::from_utf8(output.stdout).map_err(Into::into)
    }

    fn is_fake(&self) -> bool {
        false
    }

    fn subscribe_to_jobs(&self) -> JobEventReceiver {
        let (sender, receiver) = futures::channel::mpsc::unbounded();
        self.job_event_subscribers.lock().push(sender);
        receiver
    }

    /// Checks whether the file system is case sensitive by attempting to create two files
    /// that have the same name except for the casing.
    ///
    /// It creates both files in a temporary directory it removes at the end.
    async fn is_case_sensitive(&self) -> bool {
        const UNINITIALIZED: u8 = 0;
        const CASE_SENSITIVE: u8 = 1;
        const NOT_CASE_SENSITIVE: u8 = 2;

        // Note we could CAS here, but really, if we race we do this work twice at worst which isn't a big deal.
        let load = self.is_case_sensitive.load(Ordering::Acquire);
        if load != UNINITIALIZED {
            return load == CASE_SENSITIVE;
        }
        let temp_dir = self.executor.spawn(async { TempDir::new() });
        let res = maybe!(async {
            let temp_dir = temp_dir.await?;
            let test_file_1 = temp_dir.path().join("case_sensitivity_test.tmp");
            let test_file_2 = temp_dir.path().join("CASE_SENSITIVITY_TEST.TMP");

            let create_opts = CreateOptions {
                overwrite: false,
                ignore_if_exists: false,
            };

            // Create file1
            self.create_file(&test_file_1, create_opts).await?;

            // Now check whether it's possible to create file2
            let case_sensitive = match self.create_file(&test_file_2, create_opts).await {
                Ok(_) => Ok(true),
                Err(e) => {
                    if let Some(io_error) = e.downcast_ref::<io::Error>() {
                        if io_error.kind() == io::ErrorKind::AlreadyExists {
                            Ok(false)
                        } else {
                            Err(e)
                        }
                    } else {
                        Err(e)
                    }
                }
            };

            temp_dir.close()?;
            case_sensitive
        }).await.unwrap_or_else(|e| {
            log::error!(
                "Failed to determine whether filesystem is case sensitive (falling back to true) due to error: {e:#}"
            );
            true
        });
        self.is_case_sensitive.store(
            if res {
                CASE_SENSITIVE
            } else {
                NOT_CASE_SENSITIVE
            },
            Ordering::Release,
        );
        res
    }

    async fn restore(
        &self,
        trashed_entry: TrashedEntry,
    ) -> std::result::Result<PathBuf, TrashRestoreError> {
        let restored_item_path = trashed_entry.original_parent.join(&trashed_entry.name);

        let (tx, rx) = futures::channel::oneshot::channel();
        std::thread::Builder::new()
            .name("restore trashed item".to_string())
            .spawn(move || {
                let res = trash::restore_all([trashed_entry.into_trash_item()]);
                tx.send(res)
            })
            .expect("The OS can spawn a threads");
        rx.await.expect("Restore all never panics")?;
        Ok(restored_item_path)
    }
}

#[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
impl Watcher for RealWatcher {
    fn add(&self, _: &Path) -> Result<()> {
        Ok(())
    }

    fn remove(&self, _: &Path) -> Result<()> {
        Ok(())
    }
}

#[cfg(feature = "test-support")]
pub struct FakeFs {
    this: std::sync::Weak<Self>,
    // Use an unfair lock to ensure tests are deterministic.
    state: Arc<Mutex<FakeFsState>>,
    executor: gpui::BackgroundExecutor,
}

#[cfg(feature = "test-support")]
struct FakeFsState {
    root: FakeFsEntry,
    next_inode: u64,
    next_mtime: SystemTime,
    git_event_tx: async_channel::Sender<PathBuf>,
    event_txs: Vec<(PathBuf, async_channel::Sender<Vec<PathEvent>>)>,
    events_paused: bool,
    buffered_events: Vec<PathEvent>,
    metadata_call_count: usize,
    read_dir_call_count: usize,
    path_write_counts: std::collections::HashMap<PathBuf, usize>,
    moves: std::collections::HashMap<u64, PathBuf>,
    job_event_subscribers: Arc<Mutex<Vec<JobEventSender>>>,
    trash: Vec<(TrashedEntry, FakeFsEntry)>,
}

#[cfg(feature = "test-support")]
#[derive(Clone, Debug)]
enum FakeFsEntry {
    File {
        inode: u64,
        mtime: MTime,
        len: u64,
        content: Vec<u8>,
        // The path to the repository state directory, if this is a gitfile.
        git_dir_path: Option<PathBuf>,
    },
    Dir {
        inode: u64,
        mtime: MTime,
        len: u64,
        entries: BTreeMap<String, FakeFsEntry>,
        git_repo_state: Option<Arc<Mutex<FakeGitRepositoryState>>>,
    },
    Symlink {
        target: PathBuf,
    },
}

#[cfg(feature = "test-support")]
impl PartialEq for FakeFsEntry {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (
                Self::File {
                    inode: l_inode,
                    mtime: l_mtime,
                    len: l_len,
                    content: l_content,
                    git_dir_path: l_git_dir_path,
                },
                Self::File {
                    inode: r_inode,
                    mtime: r_mtime,
                    len: r_len,
                    content: r_content,
                    git_dir_path: r_git_dir_path,
                },
            ) => {
                l_inode == r_inode
                    && l_mtime == r_mtime
                    && l_len == r_len
                    && l_content == r_content
                    && l_git_dir_path == r_git_dir_path
            }
            (
                Self::Dir {
                    inode: l_inode,
                    mtime: l_mtime,
                    len: l_len,
                    entries: l_entries,
                    git_repo_state: l_git_repo_state,
                },
                Self::Dir {
                    inode: r_inode,
                    mtime: r_mtime,
                    len: r_len,
                    entries: r_entries,
                    git_repo_state: r_git_repo_state,
                },
            ) => {
                let same_repo_state = match (l_git_repo_state.as_ref(), r_git_repo_state.as_ref()) {
                    (Some(l), Some(r)) => Arc::ptr_eq(l, r),
                    (None, None) => true,
                    _ => false,
                };
                l_inode == r_inode
                    && l_mtime == r_mtime
                    && l_len == r_len
                    && l_entries == r_entries
                    && same_repo_state
            }
            (Self::Symlink { target: l_target }, Self::Symlink { target: r_target }) => {
                l_target == r_target
            }
            _ => false,
        }
    }
}

#[cfg(feature = "test-support")]
impl FakeFsState {
    fn get_and_increment_mtime(&mut self) -> MTime {
        let mtime = self.next_mtime;
        self.next_mtime += FakeFs::SYSTEMTIME_INTERVAL;
        MTime(mtime)
    }

    fn get_and_increment_inode(&mut self) -> u64 {
        let inode = self.next_inode;
        self.next_inode += 1;
        inode
    }

    fn canonicalize(&self, target: &Path, follow_symlink: bool) -> Option<PathBuf> {
        let mut canonical_path = PathBuf::new();
        let mut path = target.to_path_buf();
        let mut entry_stack = Vec::new();
        'outer: loop {
            let mut path_components = path.components().peekable();
            let mut prefix = None;
            while let Some(component) = path_components.next() {
                match component {
                    Component::Prefix(prefix_component) => prefix = Some(prefix_component),
                    Component::RootDir => {
                        entry_stack.clear();
                        entry_stack.push(&self.root);
                        canonical_path.clear();
                        match prefix {
                            Some(prefix_component) => {
                                canonical_path = PathBuf::from(prefix_component.as_os_str());
                                // Prefixes like `C:\\` are represented without their trailing slash, so we have to re-add it.
                                canonical_path.push(std::path::MAIN_SEPARATOR_STR);
                            }
                            None => canonical_path = PathBuf::from(std::path::MAIN_SEPARATOR_STR),
                        }
                    }
                    Component::CurDir => {}
                    Component::ParentDir => {
                        entry_stack.pop()?;
                        canonical_path.pop();
                    }
                    Component::Normal(name) => {
                        let current_entry = *entry_stack.last()?;
                        if let FakeFsEntry::Dir { entries, .. } = current_entry {
                            let entry = entries.get(name.to_str().unwrap())?;
                            if (path_components.peek().is_some() || follow_symlink)
                                && let FakeFsEntry::Symlink { target, .. } = entry
                            {
                                let mut target = target.clone();
                                target.extend(path_components);
                                path = target;
                                continue 'outer;
                            }
                            entry_stack.push(entry);
                            canonical_path = canonical_path.join(name);
                        } else {
                            return None;
                        }
                    }
                }
            }
            break;
        }

        if entry_stack.is_empty() {
            None
        } else {
            Some(canonical_path)
        }
    }

    fn try_entry(
        &mut self,
        target: &Path,
        follow_symlink: bool,
    ) -> Option<(&mut FakeFsEntry, PathBuf)> {
        let canonical_path = self.canonicalize(target, follow_symlink)?;

        let mut components = canonical_path
            .components()
            .skip_while(|component| matches!(component, Component::Prefix(_)));
        let Some(Component::RootDir) = components.next() else {
            panic!(
                "the path {:?} was not canonicalized properly {:?}",
                target, canonical_path
            )
        };

        let mut entry = &mut self.root;
        for component in components {
            match component {
                Component::Normal(name) => {
                    if let FakeFsEntry::Dir { entries, .. } = entry {
                        entry = entries.get_mut(name.to_str().unwrap())?;
                    } else {
                        return None;
                    }
                }
                _ => {
                    panic!(
                        "the path {:?} was not canonicalized properly {:?}",
                        target, canonical_path
                    )
                }
            }
        }

        Some((entry, canonical_path))
    }

    fn entry(&mut self, target: &Path) -> Result<&mut FakeFsEntry> {
        Ok(self
            .try_entry(target, true)
            .ok_or_else(|| {
                anyhow!(io::Error::new(
                    io::ErrorKind::NotFound,
                    format!("not found: {target:?}")
                ))
            })?
            .0)
    }

    fn write_path<Fn, T>(&mut self, path: &Path, callback: Fn) -> Result<T>
    where
        Fn: FnOnce(btree_map::Entry<String, FakeFsEntry>) -> Result<T>,
    {
        let path = normalize_path(path);
        let filename = path.file_name().context("cannot overwrite the root")?;
        let parent_path = path.parent().unwrap();

        let parent = self.entry(parent_path)?;
        let new_entry = parent
            .dir_entries(parent_path)?
            .entry(filename.to_str().unwrap().into());
        callback(new_entry)
    }

    fn emit_event<I, T>(&mut self, paths: I)
    where
        I: IntoIterator<Item = (T, Option<PathEventKind>)>,
        T: Into<PathBuf>,
    {
        self.buffered_events
            .extend(paths.into_iter().map(|(path, kind)| PathEvent {
                path: path.into(),
                kind,
            }));

        if !self.events_paused {
            self.flush_events(self.buffered_events.len());
        }
    }

    fn flush_events(&mut self, mut count: usize) {
        count = count.min(self.buffered_events.len());
        let events = self.buffered_events.drain(0..count).collect::<Vec<_>>();
        self.event_txs.retain(|(_, tx)| {
            let _ = tx.try_send(events.clone());
            !tx.is_closed()
        });
    }
}

#[cfg(feature = "test-support")]
pub static FS_DOT_GIT: std::sync::LazyLock<&'static OsStr> =
    std::sync::LazyLock::new(|| OsStr::new(".git"));

#[cfg(feature = "test-support")]
impl FakeFs {
    /// We need to use something large enough for Windows and Unix to consider this a new file.
    /// https://doc.rust-lang.org/nightly/std/time/struct.SystemTime.html#platform-specific-behavior
    const SYSTEMTIME_INTERVAL: Duration = Duration::from_nanos(100);

    pub fn new(executor: gpui::BackgroundExecutor) -> Arc<Self> {
        let (tx, rx) = async_channel::bounded::<PathBuf>(10);

        let this = Arc::new_cyclic(|this| Self {
            this: this.clone(),
            executor: executor.clone(),
            state: Arc::new(Mutex::new(FakeFsState {
                root: FakeFsEntry::Dir {
                    inode: 0,
                    mtime: MTime(UNIX_EPOCH),
                    len: 0,
                    entries: Default::default(),
                    git_repo_state: None,
                },
                git_event_tx: tx,
                next_mtime: UNIX_EPOCH + Self::SYSTEMTIME_INTERVAL,
                next_inode: 1,
                event_txs: Default::default(),
                buffered_events: Vec::new(),
                events_paused: false,
                read_dir_call_count: 0,
                metadata_call_count: 0,
                path_write_counts: Default::default(),
                moves: Default::default(),
                job_event_subscribers: Arc::new(Mutex::new(Vec::new())),
                trash: Vec::new(),
            })),
        });

        executor.spawn({
            let this = this.clone();
            async move {
                while let Ok(git_event) = rx.recv().await {
                    if let Some(mut state) = this.state.try_lock() {
                        state.emit_event([(git_event, Some(PathEventKind::Changed))]);
                    } else {
                        panic!("Failed to lock file system state, this execution would have caused a test hang");
                    }
                }
            }
        }).detach();

        this
    }

    pub fn set_next_mtime(&self, next_mtime: SystemTime) {
        let mut state = self.state.lock();
        state.next_mtime = next_mtime;
    }

    pub fn get_and_increment_mtime(&self) -> MTime {
        let mut state = self.state.lock();
        state.get_and_increment_mtime()
    }

    pub async fn touch_path(&self, path: impl AsRef<Path>) {
        let mut state = self.state.lock();
        let path = path.as_ref();
        let new_mtime = state.get_and_increment_mtime();
        let new_inode = state.get_and_increment_inode();
        state
            .write_path(path, move |entry| {
                match entry {
                    btree_map::Entry::Vacant(e) => {
                        e.insert(FakeFsEntry::File {
                            inode: new_inode,
                            mtime: new_mtime,
                            content: Vec::new(),
                            len: 0,
                            git_dir_path: None,
                        });
                    }
                    btree_map::Entry::Occupied(mut e) => match &mut *e.get_mut() {
                        FakeFsEntry::File { mtime, .. } => *mtime = new_mtime,
                        FakeFsEntry::Dir { mtime, .. } => *mtime = new_mtime,
                        FakeFsEntry::Symlink { .. } => {}
                    },
                }
                Ok(())
            })
            .unwrap();
        state.emit_event([(path.to_path_buf(), Some(PathEventKind::Changed))]);
    }

    pub async fn insert_file(&self, path: impl AsRef<Path>, content: Vec<u8>) {
        self.write_file_internal(path, content, true).unwrap()
    }

    pub async fn insert_symlink(&self, path: impl AsRef<Path>, target: PathBuf) {
        let mut state = self.state.lock();
        let path = path.as_ref();
        let file = FakeFsEntry::Symlink { target };
        state
            .write_path(path.as_ref(), move |e| match e {
                btree_map::Entry::Vacant(e) => {
                    e.insert(file);
                    Ok(())
                }
                btree_map::Entry::Occupied(mut e) => {
                    *e.get_mut() = file;
                    Ok(())
                }
            })
            .unwrap();
        state.emit_event([(path, Some(PathEventKind::Created))]);
    }

    fn write_file_internal(
        &self,
        path: impl AsRef<Path>,
        new_content: Vec<u8>,
        recreate_inode: bool,
    ) -> Result<()> {
        fn inner(
            this: &FakeFs,
            path: &Path,
            new_content: Vec<u8>,
            recreate_inode: bool,
        ) -> Result<()> {
            let mut state = this.state.lock();
            let path_buf = path.to_path_buf();
            *state.path_write_counts.entry(path_buf).or_insert(0) += 1;
            let new_inode = state.get_and_increment_inode();
            let new_mtime = state.get_and_increment_mtime();
            let new_len = new_content.len() as u64;
            let mut kind = None;
            state.write_path(path, |entry| {
                match entry {
                    btree_map::Entry::Vacant(e) => {
                        kind = Some(PathEventKind::Created);
                        e.insert(FakeFsEntry::File {
                            inode: new_inode,
                            mtime: new_mtime,
                            len: new_len,
                            content: new_content,
                            git_dir_path: None,
                        });
                    }
                    btree_map::Entry::Occupied(mut e) => {
                        kind = Some(PathEventKind::Changed);
                        if let FakeFsEntry::File {
                            inode,
                            mtime,
                            len,
                            content,
                            ..
                        } = e.get_mut()
                        {
                            *mtime = new_mtime;
                            *content = new_content;
                            *len = new_len;
                            if recreate_inode {
                                *inode = new_inode;
                            }
                        } else {
                            anyhow::bail!("not a file")
                        }
                    }
                }
                Ok(())
            })?;
            state.emit_event([(path, kind)]);
            Ok(())
        }
        inner(self, path.as_ref(), new_content, recreate_inode)
    }

    pub fn read_file_sync(&self, path: impl AsRef<Path>) -> Result<Vec<u8>> {
        let path = path.as_ref();
        let path = normalize_path(path);
        let mut state = self.state.lock();
        let entry = state.entry(&path)?;
        entry.file_content(&path).cloned()
    }

    async fn load_internal(&self, path: impl AsRef<Path>) -> Result<Vec<u8>> {
        let path = path.as_ref();
        let path = normalize_path(path);
        self.simulate_random_delay().await;
        let mut state = self.state.lock();
        let entry = state.entry(&path)?;
        entry.file_content(&path).cloned()
    }

    pub fn pause_events(&self) {
        self.state.lock().events_paused = true;
    }

    pub fn unpause_events_and_flush(&self) {
        self.state.lock().events_paused = false;
        self.flush_events(usize::MAX);
    }

    pub fn buffered_event_count(&self) -> usize {
        self.state.lock().buffered_events.len()
    }

    pub fn clear_buffered_events(&self) {
        self.state.lock().buffered_events.clear();
    }

    pub fn flush_events(&self, count: usize) {
        self.state.lock().flush_events(count);
    }

    pub(crate) fn entry(&self, target: &Path) -> Result<FakeFsEntry> {
        self.state.lock().entry(target).cloned()
    }

    pub(crate) fn insert_entry(&self, target: &Path, new_entry: FakeFsEntry) -> Result<()> {
        let mut state = self.state.lock();
        state.write_path(target, |entry| {
            match entry {
                btree_map::Entry::Vacant(vacant_entry) => {
                    vacant_entry.insert(new_entry);
                }
                btree_map::Entry::Occupied(mut occupied_entry) => {
                    occupied_entry.insert(new_entry);
                }
            }
            Ok(())
        })
    }

    #[must_use]
    pub fn insert_tree<'a>(
        &'a self,
        path: impl 'a + AsRef<Path> + Send,
        tree: serde_json::Value,
    ) -> futures::future::BoxFuture<'a, ()> {
        use futures::FutureExt as _;
        use serde_json::Value::*;

        fn inner<'a>(
            this: &'a FakeFs,
            path: Arc<Path>,
            tree: serde_json::Value,
        ) -> futures::future::BoxFuture<'a, ()> {
            async move {
                match tree {
                    Object(map) => {
                        this.create_dir(&path).await.unwrap();
                        for (name, contents) in map {
                            let mut path = PathBuf::from(path.as_ref());
                            path.push(name);
                            this.insert_tree(&path, contents).await;
                        }
                    }
                    Null => {
                        this.create_dir(&path).await.unwrap();
                    }
                    String(contents) => {
                        this.insert_file(&path, contents.into_bytes()).await;
                    }
                    _ => {
                        panic!("JSON object must contain only objects, strings, or null");
                    }
                }
            }
            .boxed()
        }
        inner(self, Arc::from(path.as_ref()), tree)
    }

    pub fn insert_tree_from_real_fs<'a>(
        &'a self,
        path: impl 'a + AsRef<Path> + Send,
        src_path: impl 'a + AsRef<Path> + Send,
    ) -> futures::future::BoxFuture<'a, ()> {
        use futures::FutureExt as _;

        async move {
            let path = path.as_ref();
            if std::fs::metadata(&src_path).unwrap().is_file() {
                let contents = std::fs::read(src_path).unwrap();
                self.insert_file(path, contents).await;
            } else {
                self.create_dir(path).await.unwrap();
                for entry in std::fs::read_dir(&src_path).unwrap() {
                    let entry = entry.unwrap();
                    self.insert_tree_from_real_fs(path.join(entry.file_name()), entry.path())
                        .await;
                }
            }
        }
        .boxed()
    }

    pub fn with_git_state_and_paths<T, F>(
        &self,
        dot_git: &Path,
        emit_git_event: bool,
        f: F,
    ) -> Result<T>
    where
        F: FnOnce(&mut FakeGitRepositoryState, &Path, &Path) -> T,
    {
        let mut state = self.state.lock();
        let git_event_tx = state.git_event_tx.clone();
        let entry = state.entry(dot_git).context("open .git")?;

        if let FakeFsEntry::Dir { git_repo_state, .. } = entry {
            let repo_state = git_repo_state.get_or_insert_with(|| {
                log::debug!("insert git state for {dot_git:?}");
                Arc::new(Mutex::new(FakeGitRepositoryState::new(git_event_tx)))
            });
            let mut repo_state = repo_state.lock();

            let result = f(&mut repo_state, dot_git, dot_git);

            drop(repo_state);
            if emit_git_event {
                state.emit_event([(
                    dot_git.join("fake_git_repo_event"),
                    Some(PathEventKind::Changed),
                )]);
            }

            Ok(result)
        } else if let FakeFsEntry::File {
            content,
            git_dir_path,
            ..
        } = &mut *entry
        {
            let path = match git_dir_path {
                Some(path) => path,
                None => {
                    let path = std::str::from_utf8(content)
                        .ok()
                        .and_then(|content| content.strip_prefix("gitdir:"))
                        .context("not a valid gitfile")?
                        .trim();
                    git_dir_path.insert(normalize_path(&dot_git.parent().unwrap().join(path)))
                }
            }
            .clone();
            let Some((git_dir_entry, canonical_path)) = state.try_entry(&path, true) else {
                anyhow::bail!("pointed-to git dir {path:?} not found")
            };
            let FakeFsEntry::Dir {
                git_repo_state,
                entries,
                ..
            } = git_dir_entry
            else {
                anyhow::bail!("gitfile points to a non-directory")
            };
            let common_dir = if let Some(child) = entries.get("commondir") {
                let raw = std::str::from_utf8(child.file_content("commondir".as_ref())?)
                    .context("commondir content")?
                    .trim();
                let raw_path = Path::new(raw);
                if raw_path.is_relative() {
                    normalize_path(&canonical_path.join(raw_path))
                } else {
                    raw_path.to_owned()
                }
            } else {
                canonical_path.clone()
            };
            let repo_state = git_repo_state.get_or_insert_with(|| {
                Arc::new(Mutex::new(FakeGitRepositoryState::new(git_event_tx)))
            });
            let mut repo_state = repo_state.lock();

            let result = f(&mut repo_state, &canonical_path, &common_dir);

            if emit_git_event {
                drop(repo_state);
                state.emit_event([(
                    canonical_path.join("fake_git_repo_event"),
                    Some(PathEventKind::Changed),
                )]);
            }

            Ok(result)
        } else {
            anyhow::bail!("not a valid git repository");
        }
    }

    pub fn with_git_state<T, F>(&self, dot_git: &Path, emit_git_event: bool, f: F) -> Result<T>
    where
        F: FnOnce(&mut FakeGitRepositoryState) -> T,
    {
        self.with_git_state_and_paths(dot_git, emit_git_event, |state, _, _| f(state))
    }

    pub fn set_branch_name(&self, dot_git: &Path, branch: Option<impl Into<String>>) {
        self.with_git_state(dot_git, true, |state| {
            let branch = branch.map(Into::into);
            state.branches.extend(branch.clone());
            state.current_branch_name = branch
        })
        .unwrap();
    }

    pub fn set_remote_for_repo(
        &self,
        dot_git: &Path,
        name: impl Into<String>,
        url: impl Into<String>,
    ) {
        self.with_git_state(dot_git, true, |state| {
            state.remotes.insert(name.into(), url.into());
        })
        .unwrap();
    }

    pub fn insert_branches(&self, dot_git: &Path, branches: &[&str]) {
        self.with_git_state(dot_git, true, |state| {
            if let Some(first) = branches.first()
                && state.current_branch_name.is_none()
            {
                state.current_branch_name = Some(first.to_string())
            }
            state
                .branches
                .extend(branches.iter().map(ToString::to_string));
        })
        .unwrap();
    }

    pub async fn add_linked_worktree_for_repo(
        &self,
        dot_git: &Path,
        emit_git_event: bool,
        worktree: Worktree,
    ) {
        let ref_name = worktree
            .ref_name
            .as_ref()
            .expect("linked worktree must have a ref_name");
        let branch_name = ref_name
            .strip_prefix("refs/heads/")
            .unwrap_or(ref_name.as_ref());

        // Create ref in git state.
        self.with_git_state(dot_git, false, |state| {
            state
                .refs
                .insert(ref_name.to_string(), worktree.sha.to_string());
        })
        .unwrap();

        // Create .git/worktrees/<name>/ directory with HEAD, commondir, and gitdir.
        let worktrees_entry_dir = dot_git.join("worktrees").join(branch_name);
        self.create_dir(&worktrees_entry_dir).await.unwrap();

        self.write_file_internal(
            worktrees_entry_dir.join("HEAD"),
            format!("ref: {ref_name}").into_bytes(),
            false,
        )
        .unwrap();

        self.write_file_internal(
            worktrees_entry_dir.join("commondir"),
            dot_git.to_string_lossy().into_owned().into_bytes(),
            false,
        )
        .unwrap();

        let worktree_dot_git = worktree.path.join(".git");
        self.write_file_internal(
            worktrees_entry_dir.join("gitdir"),
            worktree_dot_git.to_string_lossy().into_owned().into_bytes(),
            false,
        )
        .unwrap();

        // Create the worktree checkout directory with a .git file pointing back.
        self.create_dir(&worktree.path).await.unwrap();

        self.write_file_internal(
            &worktree_dot_git,
            format!("gitdir: {}", worktrees_entry_dir.display()).into_bytes(),
            false,
        )
        .unwrap();

        if emit_git_event {
            self.with_git_state(dot_git, true, |_| {}).unwrap();
        }
    }

    pub async fn remove_worktree_for_repo(
        &self,
        dot_git: &Path,
        emit_git_event: bool,
        ref_name: &str,
    ) {
        let branch_name = ref_name.strip_prefix("refs/heads/").unwrap_or(ref_name);
        let worktrees_entry_dir = dot_git.join("worktrees").join(branch_name);

        // Read gitdir to find the worktree checkout path.
        let gitdir_content = self
            .load_internal(worktrees_entry_dir.join("gitdir"))
            .await
            .unwrap();
        let gitdir_str = String::from_utf8(gitdir_content).unwrap();
        let worktree_path = PathBuf::from(gitdir_str.trim())
            .parent()
            .map(PathBuf::from)
            .unwrap_or_default();

        // Remove the worktree checkout directory.
        self.remove_dir(
            &worktree_path,
            RemoveOptions {
                recursive: true,
                ignore_if_not_exists: true,
            },
        )
        .await
        .unwrap();

        // Remove the .git/worktrees/<name>/ directory.
        self.remove_dir(
            &worktrees_entry_dir,
            RemoveOptions {
                recursive: true,
                ignore_if_not_exists: false,
            },
        )
        .await
        .unwrap();

        if emit_git_event {
            self.with_git_state(dot_git, true, |_| {}).unwrap();
        }
    }

    pub fn set_unmerged_paths_for_repo(
        &self,
        dot_git: &Path,
        unmerged_state: &[(RepoPath, UnmergedStatus)],
    ) {
        self.with_git_state(dot_git, true, |state| {
            state.unmerged_paths.clear();
            state.unmerged_paths.extend(
                unmerged_state
                    .iter()
                    .map(|(path, content)| (path.clone(), *content)),
            );
        })
        .unwrap();
    }

    pub fn set_index_for_repo(&self, dot_git: &Path, index_state: &[(&str, String)]) {
        self.with_git_state(dot_git, true, |state| {
            state.index_contents.clear();
            state.index_contents.extend(
                index_state
                    .iter()
                    .map(|(path, content)| (repo_path(path), content.clone())),
            );
        })
        .unwrap();
    }

    pub fn set_head_for_repo(
        &self,
        dot_git: &Path,
        head_state: &[(&str, String)],
        sha: impl Into<String>,
    ) {
        self.with_git_state(dot_git, true, |state| {
            state.head_contents.clear();
            state.head_contents.extend(
                head_state
                    .iter()
                    .map(|(path, content)| (repo_path(path), content.clone())),
            );
            state.refs.insert("HEAD".into(), sha.into());
        })
        .unwrap();
    }

    pub fn set_head_and_index_for_repo(&self, dot_git: &Path, contents_by_path: &[(&str, String)]) {
        self.with_git_state(dot_git, true, |state| {
            state.head_contents.clear();
            state.head_contents.extend(
                contents_by_path
                    .iter()
                    .map(|(path, contents)| (repo_path(path), contents.clone())),
            );
            state.index_contents = state.head_contents.clone();
        })
        .unwrap();
    }

    pub fn set_merge_base_content_for_repo(
        &self,
        dot_git: &Path,
        contents_by_path: &[(&str, String)],
    ) {
        self.with_git_state(dot_git, true, |state| {
            use git::Oid;

            state.merge_base_contents.clear();
            let oids = (1..)
                .map(|n| n.to_string())
                .map(|n| Oid::from_bytes(n.repeat(20).as_bytes()).unwrap());
            for ((path, content), oid) in contents_by_path.iter().zip(oids) {
                state.merge_base_contents.insert(repo_path(path), oid);
                state.oids.insert(oid, content.clone());
            }
        })
        .unwrap();
    }

    pub fn set_blame_for_repo(&self, dot_git: &Path, blames: Vec<(RepoPath, git::blame::Blame)>) {
        self.with_git_state(dot_git, true, |state| {
            state.blames.clear();
            state.blames.extend(blames);
        })
        .unwrap();
    }

    pub fn set_graph_commits(&self, dot_git: &Path, commits: Vec<Arc<InitialGraphCommitData>>) {
        self.with_git_state(dot_git, true, |state| {
            state.graph_commits = commits;
        })
        .unwrap();
    }

    pub fn set_graph_error(&self, dot_git: &Path, error: Option<String>) {
        self.with_git_state(dot_git, true, |state| {
            state.simulated_graph_error = error;
        })
        .unwrap();
    }

    pub fn set_commit_data(
        &self,
        dot_git: &Path,
        commit_data: impl IntoIterator<Item = (CommitData, bool)>,
    ) {
        self.with_git_state(dot_git, true, |state| {
            state.commit_data = commit_data
                .into_iter()
                .map(|(data, should_fail)| {
                    (
                        data.sha,
                        if should_fail {
                            FakeCommitDataEntry::Fail(data)
                        } else {
                            FakeCommitDataEntry::Success(data)
                        },
                    )
                })
                .collect();
        })
        .unwrap();
    }

    /// Put the given git repository into a state with the given status,
    /// by mutating the head, index, and unmerged state.
    pub fn set_status_for_repo(&self, dot_git: &Path, statuses: &[(&str, FileStatus)]) {
        let workdir_path = dot_git.parent().unwrap();
        let workdir_contents = self.files_with_contents(workdir_path);
        self.with_git_state(dot_git, true, |state| {
            state.index_contents.clear();
            state.head_contents.clear();
            state.unmerged_paths.clear();
            for (path, content) in workdir_contents {
                use util::{paths::PathStyle, rel_path::RelPath};

                let repo_path = RelPath::new(path.strip_prefix(&workdir_path).unwrap(), PathStyle::local()).unwrap();
                let repo_path = RepoPath::from_rel_path(&repo_path);
                let status = statuses
                    .iter()
                    .find_map(|(p, status)| (*p == repo_path.as_unix_str()).then_some(status));
                let mut content = String::from_utf8_lossy(&content).to_string();

                let mut index_content = None;
                let mut head_content = None;
                match status {
                    None => {
                        index_content = Some(content.clone());
                        head_content = Some(content);
                    }
                    Some(FileStatus::Untracked | FileStatus::Ignored) => {}
                    Some(FileStatus::Unmerged(unmerged_status)) => {
                        state
                            .unmerged_paths
                            .insert(repo_path.clone(), *unmerged_status);
                        content.push_str(" (unmerged)");
                        index_content = Some(content.clone());
                        head_content = Some(content);
                    }
                    Some(FileStatus::Tracked(TrackedStatus {
                        index_status,
                        worktree_status,
                    })) => {
                        match worktree_status {
                            StatusCode::Modified => {
                                let mut content = content.clone();
                                content.push_str(" (modified in working copy)");
                                index_content = Some(content);
                            }
                            StatusCode::TypeChanged | StatusCode::Unmodified => {
                                index_content = Some(content.clone());
                            }
                            StatusCode::Added => {}
                            StatusCode::Deleted | StatusCode::Renamed | StatusCode::Copied => {
                                panic!("cannot create these statuses for an existing file");
                            }
                        };
                        match index_status {
                            StatusCode::Modified => {
                                let mut content = index_content.clone().expect(
                                    "file cannot be both modified in index and created in working copy",
                                );
                                content.push_str(" (modified in index)");
                                head_content = Some(content);
                            }
                            StatusCode::TypeChanged | StatusCode::Unmodified => {
                                head_content = Some(index_content.clone().expect("file cannot be both unmodified in index and created in working copy"));
                            }
                            StatusCode::Added => {}
                            StatusCode::Deleted  => {
                                head_content = Some("".into());
                            }
                            StatusCode::Renamed | StatusCode::Copied => {
                                panic!("cannot create these statuses for an existing file");
                            }
                        };
                    }
                };

                if let Some(content) = index_content {
                    state.index_contents.insert(repo_path.clone(), content);
                }
                if let Some(content) = head_content {
                    state.head_contents.insert(repo_path.clone(), content);
                }
            }
        }).unwrap();
    }

    pub fn set_error_message_for_index_write(&self, dot_git: &Path, message: Option<String>) {
        self.with_git_state(dot_git, true, |state| {
            state.simulated_index_write_error_message = message;
        })
        .unwrap();
    }

    pub fn set_create_worktree_error(&self, dot_git: &Path, message: Option<String>) {
        self.with_git_state(dot_git, true, |state| {
            state.simulated_create_worktree_error = message;
        })
        .unwrap();
    }

    pub fn paths(&self, include_dot_git: bool) -> Vec<PathBuf> {
        let mut result = Vec::new();
        let mut queue = collections::VecDeque::new();
        let state = &*self.state.lock();
        queue.push_back((PathBuf::from(util::path!("/")), &state.root));
        while let Some((path, entry)) = queue.pop_front() {
            if let FakeFsEntry::Dir { entries, .. } = entry {
                for (name, entry) in entries {
                    queue.push_back((path.join(name), entry));
                }
            }
            if include_dot_git
                || !path
                    .components()
                    .any(|component| component.as_os_str() == *FS_DOT_GIT)
            {
                result.push(path);
            }
        }
        result
    }

    pub fn directories(&self, include_dot_git: bool) -> Vec<PathBuf> {
        let mut result = Vec::new();
        let mut queue = collections::VecDeque::new();
        let state = &*self.state.lock();
        queue.push_back((PathBuf::from(util::path!("/")), &state.root));
        while let Some((path, entry)) = queue.pop_front() {
            if let FakeFsEntry::Dir { entries, .. } = entry {
                for (name, entry) in entries {
                    queue.push_back((path.join(name), entry));
                }
                if include_dot_git
                    || !path
                        .components()
                        .any(|component| component.as_os_str() == *FS_DOT_GIT)
                {
                    result.push(path);
                }
            }
        }
        result
    }

    pub fn files(&self) -> Vec<PathBuf> {
        let mut result = Vec::new();
        let mut queue = collections::VecDeque::new();
        let state = &*self.state.lock();
        queue.push_back((PathBuf::from(util::path!("/")), &state.root));
        while let Some((path, entry)) = queue.pop_front() {
            match entry {
                FakeFsEntry::File { .. } => result.push(path),
                FakeFsEntry::Dir { entries, .. } => {
                    for (name, entry) in entries {
                        queue.push_back((path.join(name), entry));
                    }
                }
                FakeFsEntry::Symlink { .. } => {}
            }
        }
        result
    }

    pub fn files_with_contents(&self, prefix: &Path) -> Vec<(PathBuf, Vec<u8>)> {
        let mut result = Vec::new();
        let mut queue = collections::VecDeque::new();
        let state = &*self.state.lock();
        queue.push_back((PathBuf::from(util::path!("/")), &state.root));
        while let Some((path, entry)) = queue.pop_front() {
            match entry {
                FakeFsEntry::File { content, .. } => {
                    if path.starts_with(prefix) {
                        result.push((path, content.clone()));
                    }
                }
                FakeFsEntry::Dir { entries, .. } => {
                    for (name, entry) in entries {
                        queue.push_back((path.join(name), entry));
                    }
                }
                FakeFsEntry::Symlink { .. } => {}
            }
        }
        result
    }

    /// How many `read_dir` calls have been issued.
    pub fn read_dir_call_count(&self) -> usize {
        self.state.lock().read_dir_call_count
    }

    pub fn watched_paths(&self) -> Vec<PathBuf> {
        let state = self.state.lock();
        state
            .event_txs
            .iter()
            .filter_map(|(path, tx)| Some(path.clone()).filter(|_| !tx.is_closed()))
            .collect()
    }

    /// How many `metadata` calls have been issued.
    pub fn metadata_call_count(&self) -> usize {
        self.state.lock().metadata_call_count
    }

    /// How many write operations have been issued for a specific path.
    pub fn write_count_for_path(&self, path: impl AsRef<Path>) -> usize {
        let path = path.as_ref().to_path_buf();
        self.state
            .lock()
            .path_write_counts
            .get(&path)
            .copied()
            .unwrap_or(0)
    }

    pub fn emit_fs_event(&self, path: impl Into<PathBuf>, event: Option<PathEventKind>) {
        self.state.lock().emit_event(std::iter::once((path, event)));
    }

    fn simulate_random_delay(&self) -> impl futures::Future<Output = ()> {
        self.executor.simulate_random_delay()
    }

    /// Returns list of all tracked trash entries.
    pub fn trash_entries(&self) -> Vec<TrashedEntry> {
        self.state
            .lock()
            .trash
            .iter()
            .map(|(entry, _)| entry.clone())
            .collect()
    }

    async fn remove_dir_inner(
        &self,
        path: &Path,
        options: RemoveOptions,
    ) -> Result<Option<FakeFsEntry>> {
        self.simulate_random_delay().await;

        let path = normalize_path(path);
        let parent_path = path.parent().context("cannot remove the root")?;
        let base_name = path.file_name().context("cannot remove the root")?;

        let mut state = self.state.lock();
        let parent_entry = state.entry(parent_path)?;
        let entry = parent_entry
            .dir_entries(parent_path)?
            .entry(base_name.to_str().unwrap().into());

        let removed = match entry {
            btree_map::Entry::Vacant(_) => {
                if !options.ignore_if_not_exists {
                    anyhow::bail!("{path:?} does not exist");
                }

                None
            }
            btree_map::Entry::Occupied(mut entry) => {
                {
                    let children = entry.get_mut().dir_entries(&path)?;
                    if !options.recursive && !children.is_empty() {
                        anyhow::bail!("{path:?} is not empty");
                    }
                }

                Some(entry.remove())
            }
        };

        state.emit_event([(path, Some(PathEventKind::Removed))]);
        Ok(removed)
    }

    async fn remove_file_inner(
        &self,
        path: &Path,
        options: RemoveOptions,
    ) -> Result<Option<FakeFsEntry>> {
        self.simulate_random_delay().await;

        let path = normalize_path(path);
        let parent_path = path.parent().context("cannot remove the root")?;
        let base_name = path.file_name().unwrap();
        let mut state = self.state.lock();
        let parent_entry = state.entry(parent_path)?;
        let entry = parent_entry
            .dir_entries(parent_path)?
            .entry(base_name.to_str().unwrap().into());
        let removed = match entry {
            btree_map::Entry::Vacant(_) => {
                if !options.ignore_if_not_exists {
                    anyhow::bail!("{path:?} does not exist");
                }

                None
            }
            btree_map::Entry::Occupied(mut entry) => {
                entry.get_mut().file_content(&path)?;
                Some(entry.remove())
            }
        };

        state.emit_event([(path, Some(PathEventKind::Removed))]);
        Ok(removed)
    }
}

#[cfg(feature = "test-support")]
impl FakeFsEntry {
    fn is_file(&self) -> bool {
        matches!(self, Self::File { .. })
    }

    fn is_symlink(&self) -> bool {
        matches!(self, Self::Symlink { .. })
    }

    fn file_content(&self, path: &Path) -> Result<&Vec<u8>> {
        if let Self::File { content, .. } = self {
            Ok(content)
        } else {
            anyhow::bail!("not a file: {path:?}");
        }
    }

    fn dir_entries(&mut self, path: &Path) -> Result<&mut BTreeMap<String, FakeFsEntry>> {
        if let Self::Dir { entries, .. } = self {
            Ok(entries)
        } else {
            anyhow::bail!("not a directory: {path:?}");
        }
    }
}

#[cfg(feature = "test-support")]
struct FakeWatcher {
    tx: async_channel::Sender<Vec<PathEvent>>,
    original_path: PathBuf,
    fs_state: Arc<Mutex<FakeFsState>>,
    prefixes: Mutex<Vec<PathBuf>>,
}

#[cfg(feature = "test-support")]
impl Watcher for FakeWatcher {
    fn add(&self, path: &Path) -> Result<()> {
        if path.starts_with(&self.original_path) {
            return Ok(());
        }
        self.fs_state
            .try_lock()
            .unwrap()
            .event_txs
            .push((path.to_owned(), self.tx.clone()));
        self.prefixes.lock().push(path.to_owned());
        Ok(())
    }

    fn remove(&self, _: &Path) -> Result<()> {
        Ok(())
    }
}

#[cfg(feature = "test-support")]
#[derive(Debug)]
struct FakeHandle {
    inode: u64,
}

#[cfg(feature = "test-support")]
impl FileHandle for FakeHandle {
    fn current_path(&self, fs: &Arc<dyn Fs>) -> Result<PathBuf> {
        let fs = fs.as_fake();
        let mut state = fs.state.lock();
        let Some(target) = state.moves.get(&self.inode).cloned() else {
            anyhow::bail!("fake fd not moved")
        };

        if state.try_entry(&target, false).is_some() {
            return Ok(target);
        }
        anyhow::bail!("fake fd target not found")
    }
}

#[cfg(feature = "test-support")]
#[async_trait::async_trait]
impl Fs for FakeFs {
    async fn create_dir(&self, path: &Path) -> Result<()> {
        self.simulate_random_delay().await;

        let mut created_dirs = Vec::new();
        let mut cur_path = PathBuf::new();
        for component in path.components() {
            let should_skip = matches!(component, Component::Prefix(..) | Component::RootDir);
            cur_path.push(component);
            if should_skip {
                continue;
            }
            let mut state = self.state.lock();

            let inode = state.get_and_increment_inode();
            let mtime = state.get_and_increment_mtime();
            state.write_path(&cur_path, |entry| {
                entry.or_insert_with(|| {
                    created_dirs.push((cur_path.clone(), Some(PathEventKind::Created)));
                    FakeFsEntry::Dir {
                        inode,
                        mtime,
                        len: 0,
                        entries: Default::default(),
                        git_repo_state: None,
                    }
                });
                Ok(())
            })?
        }

        self.state.lock().emit_event(created_dirs);
        Ok(())
    }

    async fn create_file(&self, path: &Path, options: CreateOptions) -> Result<()> {
        self.simulate_random_delay().await;
        let mut state = self.state.lock();
        let inode = state.get_and_increment_inode();
        let mtime = state.get_and_increment_mtime();
        let file = FakeFsEntry::File {
            inode,
            mtime,
            len: 0,
            content: Vec::new(),
            git_dir_path: None,
        };
        let mut kind = Some(PathEventKind::Created);
        state.write_path(path, |entry| {
            match entry {
                btree_map::Entry::Occupied(mut e) => {
                    if options.overwrite {
                        kind = Some(PathEventKind::Changed);
                        *e.get_mut() = file;
                    } else if !options.ignore_if_exists {
                        anyhow::bail!("path already exists: {path:?}");
                    }
                }
                btree_map::Entry::Vacant(e) => {
                    e.insert(file);
                }
            }
            Ok(())
        })?;
        state.emit_event([(path, kind)]);
        Ok(())
    }

    async fn create_symlink(&self, path: &Path, target: PathBuf) -> Result<()> {
        let mut state = self.state.lock();
        let file = FakeFsEntry::Symlink { target };
        state
            .write_path(path.as_ref(), move |e| match e {
                btree_map::Entry::Vacant(e) => {
                    e.insert(file);
                    Ok(())
                }
                btree_map::Entry::Occupied(mut e) => {
                    *e.get_mut() = file;
                    Ok(())
                }
            })
            .unwrap();
        state.emit_event([(path, Some(PathEventKind::Created))]);

        Ok(())
    }

    async fn create_file_with(
        &self,
        path: &Path,
        mut content: Pin<&mut (dyn AsyncRead + Send)>,
    ) -> Result<()> {
        let mut bytes = Vec::new();
        content.read_to_end(&mut bytes).await?;
        self.write_file_internal(path, bytes, true)?;
        Ok(())
    }

    async fn extract_tar_file(
        &self,
        path: &Path,
        content: Archive<Pin<&mut (dyn AsyncRead + Send)>>,
    ) -> Result<()> {
        let mut entries = content.entries()?;
        while let Some(entry) = entries.next().await {
            let mut entry = entry?;
            if entry.header().entry_type().is_file() {
                let path = path.join(entry.path()?.as_ref());
                let mut bytes = Vec::new();
                entry.read_to_end(&mut bytes).await?;
                self.create_dir(path.parent().unwrap()).await?;
                self.write_file_internal(&path, bytes, true)?;
            }
        }
        Ok(())
    }

    async fn rename(&self, old_path: &Path, new_path: &Path, options: RenameOptions) -> Result<()> {
        self.simulate_random_delay().await;

        let old_path = normalize_path(old_path);
        let new_path = normalize_path(new_path);

        if options.create_parents {
            if let Some(parent) = new_path.parent() {
                self.create_dir(parent).await?;
            }
        }

        let mut state = self.state.lock();
        let moved_entry = state.write_path(&old_path, |e| {
            if let btree_map::Entry::Occupied(e) = e {
                Ok(e.get().clone())
            } else {
                anyhow::bail!("path does not exist: {old_path:?}")
            }
        })?;

        let inode = match moved_entry {
            FakeFsEntry::File { inode, .. } => inode,
            FakeFsEntry::Dir { inode, .. } => inode,
            _ => 0,
        };

        state.moves.insert(inode, new_path.clone());

        state.write_path(&new_path, |e| {
            match e {
                btree_map::Entry::Occupied(mut e) => {
                    if options.overwrite {
                        *e.get_mut() = moved_entry;
                    } else if !options.ignore_if_exists {
                        anyhow::bail!("path already exists: {new_path:?}");
                    }
                }
                btree_map::Entry::Vacant(e) => {
                    e.insert(moved_entry);
                }
            }
            Ok(())
        })?;

        state
            .write_path(&old_path, |e| {
                if let btree_map::Entry::Occupied(e) = e {
                    Ok(e.remove())
                } else {
                    unreachable!()
                }
            })
            .unwrap();

        state.emit_event([
            (old_path, Some(PathEventKind::Removed)),
            (new_path, Some(PathEventKind::Created)),
        ]);
        Ok(())
    }

    async fn copy_file(&self, source: &Path, target: &Path, options: CopyOptions) -> Result<()> {
        self.simulate_random_delay().await;

        let source = normalize_path(source);
        let target = normalize_path(target);
        let mut state = self.state.lock();
        let mtime = state.get_and_increment_mtime();
        let inode = state.get_and_increment_inode();
        let source_entry = state.entry(&source)?;
        let content = source_entry.file_content(&source)?.clone();
        let mut kind = Some(PathEventKind::Created);
        state.write_path(&target, |e| match e {
            btree_map::Entry::Occupied(e) => {
                if options.overwrite {
                    kind = Some(PathEventKind::Changed);
                    Ok(Some(e.get().clone()))
                } else if !options.ignore_if_exists {
                    anyhow::bail!("{target:?} already exists");
                } else {
                    Ok(None)
                }
            }
            btree_map::Entry::Vacant(e) => Ok(Some(
                e.insert(FakeFsEntry::File {
                    inode,
                    mtime,
                    len: content.len() as u64,
                    content,
                    git_dir_path: None,
                })
                .clone(),
            )),
        })?;
        state.emit_event([(target, kind)]);
        Ok(())
    }

    async fn remove_dir(&self, path: &Path, options: RemoveOptions) -> Result<()> {
        self.remove_dir_inner(path, options).await.map(|_| ())
    }

    async fn trash(&self, path: &Path, options: RemoveOptions) -> Result<TrashedEntry> {
        let normalized_path = normalize_path(path);
        let parent_path = normalized_path.parent().context("cannot remove the root")?;
        let base_name = normalized_path.file_name().unwrap();
        let result = if self.is_dir(path).await {
            self.remove_dir_inner(path, options).await?
        } else {
            self.remove_file_inner(path, options).await?
        };

        match result {
            Some(fake_entry) => {
                let trashed_entry = TrashedEntry {
                    id: base_name.to_str().unwrap().into(),
                    name: base_name.to_str().unwrap().into(),
                    original_parent: parent_path.to_path_buf(),
                };

                let mut state = self.state.lock();
                state.trash.push((trashed_entry.clone(), fake_entry));
                Ok(trashed_entry)
            }
            None => anyhow::bail!("{normalized_path:?} does not exist"),
        }
    }

    async fn remove_file(&self, path: &Path, options: RemoveOptions) -> Result<()> {
        self.remove_file_inner(path, options).await.map(|_| ())
    }

    async fn open_sync(&self, path: &Path) -> Result<Box<dyn io::Read + Send + Sync>> {
        let bytes = self.load_internal(path).await?;
        Ok(Box::new(io::Cursor::new(bytes)))
    }

    async fn open_handle(&self, path: &Path) -> Result<Arc<dyn FileHandle>> {
        self.simulate_random_delay().await;
        let mut state = self.state.lock();
        let inode = match state.entry(path)? {
            FakeFsEntry::File { inode, .. } => *inode,
            FakeFsEntry::Dir { inode, .. } => *inode,
            _ => unreachable!(),
        };
        Ok(Arc::new(FakeHandle { inode }))
    }

    async fn load(&self, path: &Path) -> Result<String> {
        let content = self.load_internal(path).await?;
        Ok(String::from_utf8(content)?)
    }

    async fn load_bytes(&self, path: &Path) -> Result<Vec<u8>> {
        self.load_internal(path).await
    }

    async fn atomic_write(&self, path: PathBuf, data: String) -> Result<()> {
        self.simulate_random_delay().await;
        let path = normalize_path(path.as_path());
        if let Some(path) = path.parent() {
            self.create_dir(path).await?;
        }
        self.write_file_internal(path, data.into_bytes(), true)?;
        Ok(())
    }

    async fn save(&self, path: &Path, text: &Rope, line_ending: LineEnding) -> Result<()> {
        self.simulate_random_delay().await;
        let path = normalize_path(path);
        let content = text::chunks_with_line_ending(text, line_ending).collect::<String>();
        if let Some(path) = path.parent() {
            self.create_dir(path).await?;
        }
        self.write_file_internal(path, content.into_bytes(), false)?;
        Ok(())
    }

    async fn write(&self, path: &Path, content: &[u8]) -> Result<()> {
        self.simulate_random_delay().await;
        let path = normalize_path(path);
        if let Some(path) = path.parent() {
            self.create_dir(path).await?;
        }
        self.write_file_internal(path, content.to_vec(), false)?;
        Ok(())
    }

    async fn canonicalize(&self, path: &Path) -> Result<PathBuf> {
        let path = normalize_path(path);
        self.simulate_random_delay().await;
        let state = self.state.lock();
        let canonical_path = state
            .canonicalize(&path, true)
            .with_context(|| format!("path does not exist: {path:?}"))?;
        Ok(canonical_path)
    }

    async fn is_file(&self, path: &Path) -> bool {
        let path = normalize_path(path);
        self.simulate_random_delay().await;
        let mut state = self.state.lock();
        if let Some((entry, _)) = state.try_entry(&path, true) {
            entry.is_file()
        } else {
            false
        }
    }

    async fn is_dir(&self, path: &Path) -> bool {
        self.metadata(path)
            .await
            .is_ok_and(|metadata| metadata.is_some_and(|metadata| metadata.is_dir))
    }

    async fn metadata(&self, path: &Path) -> Result<Option<Metadata>> {
        self.simulate_random_delay().await;
        let path = normalize_path(path);
        let mut state = self.state.lock();
        state.metadata_call_count += 1;
        if let Some((mut entry, _)) = state.try_entry(&path, false) {
            let is_symlink = entry.is_symlink();
            if is_symlink {
                if let Some(e) = state.try_entry(&path, true).map(|e| e.0) {
                    entry = e;
                } else {
                    return Ok(None);
                }
            }

            Ok(Some(match &*entry {
                FakeFsEntry::File {
                    inode, mtime, len, ..
                } => Metadata {
                    inode: *inode,
                    mtime: *mtime,
                    len: *len,
                    is_dir: false,
                    is_symlink,
                    is_fifo: false,
                    is_executable: false,
                },
                FakeFsEntry::Dir {
                    inode, mtime, len, ..
                } => Metadata {
                    inode: *inode,
                    mtime: *mtime,
                    len: *len,
                    is_dir: true,
                    is_symlink,
                    is_fifo: false,
                    is_executable: false,
                },
                FakeFsEntry::Symlink { .. } => unreachable!(),
            }))
        } else {
            Ok(None)
        }
    }

    async fn read_link(&self, path: &Path) -> Result<PathBuf> {
        self.simulate_random_delay().await;
        let path = normalize_path(path);
        let mut state = self.state.lock();
        let (entry, _) = state
            .try_entry(&path, false)
            .with_context(|| format!("path does not exist: {path:?}"))?;
        if let FakeFsEntry::Symlink { target } = entry {
            Ok(target.clone())
        } else {
            anyhow::bail!("not a symlink: {path:?}")
        }
    }

    async fn read_dir(
        &self,
        path: &Path,
    ) -> Result<Pin<Box<dyn Send + Stream<Item = Result<PathBuf>>>>> {
        self.simulate_random_delay().await;
        let path = normalize_path(path);
        let mut state = self.state.lock();
        state.read_dir_call_count += 1;
        let entry = state.entry(&path)?;
        let children = entry.dir_entries(&path)?;
        let paths = children
            .keys()
            .map(|file_name| Ok(path.join(file_name)))
            .collect::<Vec<_>>();
        Ok(Box::pin(futures::stream::iter(paths)))
    }

    async fn watch(
        &self,
        path: &Path,
        _: Duration,
    ) -> (
        Pin<Box<dyn Send + Stream<Item = Vec<PathEvent>>>>,
        Arc<dyn Watcher>,
    ) {
        self.simulate_random_delay().await;
        let (tx, rx) = async_channel::unbounded();
        let path = path.to_path_buf();
        self.state.lock().event_txs.push((path.clone(), tx.clone()));
        let executor = self.executor.clone();
        let watcher = Arc::new(FakeWatcher {
            tx,
            original_path: path.to_owned(),
            fs_state: self.state.clone(),
            prefixes: Mutex::new(vec![path]),
        });
        (
            Box::pin(futures::StreamExt::filter(rx, {
                let watcher = watcher.clone();
                move |events| {
                    let result = events.iter().any(|evt_path| {
                        watcher
                            .prefixes
                            .lock()
                            .iter()
                            .any(|prefix| evt_path.path.starts_with(prefix))
                    });
                    let executor = executor.clone();
                    async move {
                        executor.simulate_random_delay().await;
                        result
                    }
                }
            })),
            watcher,
        )
    }

    fn open_repo(
        &self,
        abs_dot_git: &Path,
        _system_git_binary: Option<&Path>,
    ) -> Result<Arc<dyn GitRepository>> {
        self.with_git_state_and_paths(
            abs_dot_git,
            false,
            |_, repository_dir_path, common_dir_path| {
                Arc::new(fake_git_repo::FakeGitRepository {
                    fs: self.this.upgrade().unwrap(),
                    executor: self.executor.clone(),
                    dot_git_path: abs_dot_git.to_path_buf(),
                    repository_dir_path: repository_dir_path.to_owned(),
                    common_dir_path: common_dir_path.to_owned(),
                    checkpoints: Arc::default(),
                    is_trusted: Arc::default(),
                }) as _
            },
        )
    }

    async fn git_init(
        &self,
        abs_work_directory_path: &Path,
        _fallback_branch_name: String,
    ) -> Result<()> {
        self.create_dir(&abs_work_directory_path.join(".git")).await
    }

    async fn git_clone(&self, _abs_work_directory: &Path, _repo_url: &str) -> Result<()> {
        anyhow::bail!("Git clone is not supported in fake Fs")
    }

    async fn git_config(&self, _abs_work_directory: &Path, _args: Vec<String>) -> Result<String> {
        anyhow::bail!("Git config is not supported in fake Fs")
    }

    fn is_fake(&self) -> bool {
        true
    }

    async fn is_case_sensitive(&self) -> bool {
        true
    }

    fn subscribe_to_jobs(&self) -> JobEventReceiver {
        let (sender, receiver) = futures::channel::mpsc::unbounded();
        self.state.lock().job_event_subscribers.lock().push(sender);
        receiver
    }

    async fn restore(&self, trashed_entry: TrashedEntry) -> Result<PathBuf, TrashRestoreError> {
        let mut state = self.state.lock();

        let Some((trashed_entry, fake_entry)) = state
            .trash
            .iter()
            .find(|(entry, _)| *entry == trashed_entry)
            .cloned()
        else {
            return Err(TrashRestoreError::NotFound {
                path: PathBuf::from(trashed_entry.id),
            });
        };

        let path = trashed_entry
            .original_parent
            .join(trashed_entry.name.clone());

        let result = state.write_path(&path, |entry| match entry {
            btree_map::Entry::Vacant(entry) => {
                entry.insert(fake_entry);
                Ok(())
            }
            btree_map::Entry::Occupied(_) => {
                anyhow::bail!("Failed to restore {:?}", path);
            }
        });

        match result {
            Ok(_) => {
                state.trash.retain(|(entry, _)| *entry != trashed_entry);
                state.emit_event([(path.clone(), Some(PathEventKind::Created))]);
                Ok(path)
            }
            Err(_) => {
                // For now we'll just assume that this failed because it was a
                // collision error, which I think that, for the time being, is
                // the only case where this could fail?
                Err(TrashRestoreError::Collision { path })
            }
        }
    }

    #[cfg(feature = "test-support")]
    fn as_fake(&self) -> Arc<FakeFs> {
        self.this.upgrade().unwrap()
    }
}

pub async fn copy_recursive<'a>(
    fs: &'a dyn Fs,
    source: &'a Path,
    target: &'a Path,
    options: CopyOptions,
) -> Result<()> {
    for (item, is_dir) in read_dir_items(fs, source).await? {
        let Ok(item_relative_path) = item.strip_prefix(source) else {
            continue;
        };
        let target_item = if item_relative_path == Path::new("") {
            target.to_path_buf()
        } else {
            target.join(item_relative_path)
        };
        if is_dir {
            if !options.overwrite && fs.metadata(&target_item).await.is_ok_and(|m| m.is_some()) {
                if options.ignore_if_exists {
                    continue;
                } else {
                    anyhow::bail!("{target_item:?} already exists");
                }
            }
            let _ = fs
                .remove_dir(
                    &target_item,
                    RemoveOptions {
                        recursive: true,
                        ignore_if_not_exists: true,
                    },
                )
                .await;
            fs.create_dir(&target_item).await?;
        } else {
            fs.copy_file(&item, &target_item, options).await?;
        }
    }
    Ok(())
}

/// Recursively reads all of the paths in the given directory.
///
/// Returns a vector of tuples of (path, is_dir).
pub async fn read_dir_items<'a>(fs: &'a dyn Fs, source: &'a Path) -> Result<Vec<(PathBuf, bool)>> {
    let mut items = Vec::new();
    read_recursive(fs, source, &mut items).await?;
    Ok(items)
}

fn read_recursive<'a>(
    fs: &'a dyn Fs,
    source: &'a Path,
    output: &'a mut Vec<(PathBuf, bool)>,
) -> BoxFuture<'a, Result<()>> {
    use futures::future::FutureExt;

    async move {
        let metadata = fs
            .metadata(source)
            .await?
            .with_context(|| format!("path does not exist: {source:?}"))?;

        if metadata.is_dir {
            output.push((source.to_path_buf(), true));
            let mut children = fs.read_dir(source).await?;
            while let Some(child_path) = children.next().await {
                if let Ok(child_path) = child_path {
                    read_recursive(fs, &child_path, output).await?;
                }
            }
        } else {
            output.push((source.to_path_buf(), false));
        }
        Ok(())
    }
    .boxed()
}

// todo(windows)
// can we get file id not open the file twice?
// https://github.com/rust-lang/rust/issues/63010
#[cfg(target_os = "windows")]
async fn file_id(path: impl AsRef<Path>) -> Result<u64> {
    use std::os::windows::io::AsRawHandle;

    use smol::fs::windows::OpenOptionsExt;
    use windows::Win32::{
        Foundation::HANDLE,
        Storage::FileSystem::{
            BY_HANDLE_FILE_INFORMATION, FILE_FLAG_BACKUP_SEMANTICS, GetFileInformationByHandle,
        },
    };

    let file = smol::fs::OpenOptions::new()
        .read(true)
        .custom_flags(FILE_FLAG_BACKUP_SEMANTICS.0)
        .open(path)
        .await?;

    let mut info: BY_HANDLE_FILE_INFORMATION = unsafe { std::mem::zeroed() };
    // https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfileinformationbyhandle
    // This function supports Windows XP+
    smol::unblock(move || {
        unsafe { GetFileInformationByHandle(HANDLE(file.as_raw_handle() as _), &mut info)? };

        Ok(((info.nFileIndexHigh as u64) << 32) | (info.nFileIndexLow as u64))
    })
    .await
}

#[cfg(target_os = "windows")]
fn atomic_replace<P: AsRef<Path>>(
    replaced_file: P,
    replacement_file: P,
) -> windows::core::Result<()> {
    use windows::{
        Win32::Storage::FileSystem::{REPLACE_FILE_FLAGS, ReplaceFileW},
        core::HSTRING,
    };

    // If the file does not exist, create it.
    let _ = std::fs::File::create_new(replaced_file.as_ref());

    unsafe {
        ReplaceFileW(
            &HSTRING::from(replaced_file.as_ref().to_string_lossy().into_owned()),
            &HSTRING::from(replacement_file.as_ref().to_string_lossy().into_owned()),
            None,
            REPLACE_FILE_FLAGS::default(),
            None,
            None,
        )
    }
}
