use super::nodes::{
    DirectoryStream, OpenFile, ResolvedEntry, bsd_lock_operation, errno, fuse_lock, record_lock,
    reply_result, reply_xattr, timestamp, unsupported_lock_flags, writable_xattr,
};
use super::{
    Arc, AsFd, BsdFileFlags, CopyFileRangeFlags, DirectoryEntry, Errno, FallocateFlags, FcntlArg,
    FileAttr, FileExt, FileHandle, FileType, Filesystem, FopenFlags, FuseRenameFlags, Generation,
    Gid, INodeNo, IgnoredWorkspace, InitFlags, KernelConfig, LockFlags, LockOwner, Mode, OFlags,
    OpenFlags, Ordering, OsStr, OsString, Path, RenameFlags, ReplyAttr, ReplyCreate, ReplyData,
    ReplyDirectory, ReplyEmpty, ReplyEntry, ReplyLock, ReplyLseek, ReplyOpen, ReplyStatfs,
    ReplyWrite, ReplyXattr, Request, SeekFrom, SystemTime, TTL, TimeOrNow, Timestamps, Uid,
    WriteFlags, XattrFlags, bsd_flock, copy_file_range, fallocate, fchmod, fchown, fcntl,
    fgetxattr, flistxattr, fremovexattr, fsetxattr, fstat, fstatvfs, ftruncate, futimens, io,
    mknodat, open_flags, seek,
};

impl Filesystem for IgnoredWorkspace {
    fn init(&mut self, _request: &Request, config: &mut KernelConfig) -> io::Result<()> {
        config
            .add_capabilities(
                InitFlags::FUSE_AUTO_INVAL_DATA
                    | InitFlags::FUSE_POSIX_ACL
                    | InitFlags::FUSE_POSIX_LOCKS
                    | InitFlags::FUSE_FLOCK_LOCKS,
            )
            .map_err(|unsupported| {
                io::Error::other(format!(
                    "required FUSE capabilities are unavailable: {unsupported:?}"
                ))
            })
    }

    fn lookup(&self, _request: &Request, parent: INodeNo, name: &OsStr, reply: ReplyEntry) {
        match self.child_path(parent, name) {
            Ok(path) => self.reply_entry(&path, reply),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn getattr(
        &self,
        _request: &Request,
        inode: INodeNo,
        handle: Option<FileHandle>,
        reply: ReplyAttr,
    ) {
        let result = if let Some(handle) = handle {
            self.with_file(handle, |open| {
                let stat = fstat(open.file.as_fd())?;
                let path = self.path_for(inode)?;
                self.attributes(&ResolvedEntry {
                    path,
                    backing: open.backing,
                    stat,
                })
            })
        } else {
            self.path_for(inode).and_then(|path| {
                let snapshot = self.classifier.snapshot_for(&path);
                self.resolve(&snapshot, &path)
                    .and_then(|entry| self.attributes(&entry))
            })
        };
        match result {
            Ok(attributes) => reply.attr(&TTL, &attributes),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn setattr(
        &self,
        _request: &Request,
        inode: INodeNo,
        mode: Option<u32>,
        uid: Option<u32>,
        gid: Option<u32>,
        size: Option<u64>,
        atime: Option<TimeOrNow>,
        mtime: Option<TimeOrNow>,
        _ctime: Option<SystemTime>,
        handle: Option<FileHandle>,
        _crtime: Option<SystemTime>,
        _chgtime: Option<SystemTime>,
        _bkuptime: Option<SystemTime>,
        _flags: Option<BsdFileFlags>,
        reply: ReplyAttr,
    ) {
        let operation = |open: &OpenFile| -> io::Result<FileAttr> {
            if let Some(mode) = mode {
                fchmod(open.file.as_fd(), Mode::from_raw_mode(mode & 0o7777))?;
            }
            if uid.is_some() || gid.is_some() {
                fchown(
                    open.file.as_fd(),
                    uid.map(Uid::from_raw),
                    gid.map(Gid::from_raw),
                )?;
            }
            if let Some(size) = size {
                ftruncate(open.file.as_fd(), size)?;
            }
            if atime.is_some() || mtime.is_some() {
                futimens(
                    open.file.as_fd(),
                    &Timestamps {
                        last_access: timestamp(atime),
                        last_modification: timestamp(mtime),
                    },
                )?;
            }
            let path = self.path_for(inode)?;
            self.attributes(&ResolvedEntry {
                path,
                backing: open.backing,
                stat: fstat(open.file.as_fd())?,
            })
        };
        let result = if let Some(handle) = handle {
            self.with_file(handle, operation)
        } else {
            let path = match self.path_for(inode) {
                Ok(path) => path,
                Err(error) => {
                    reply.error(errno(&error));
                    return;
                }
            };
            let snapshot = self.classifier.snapshot_for(&path);
            let entry = match self.resolve(&snapshot, &path) {
                Ok(entry) => entry,
                Err(error) => {
                    reply.error(errno(&error));
                    return;
                }
            };
            if entry.stat.st_mode & libc::S_IFMT == libc::S_IFLNK {
                if mode.is_some() || uid.is_some() || gid.is_some() || size.is_some() {
                    Err(io::Error::from_raw_os_error(libc::EOPNOTSUPP))
                } else {
                    self.root(entry.backing)
                        .set_symlink_times(
                            &path,
                            &Timestamps {
                                last_access: timestamp(atime),
                                last_modification: timestamp(mtime),
                            },
                        )
                        .and_then(|()| {
                            self.root(entry.backing).stat(&path).and_then(|stat| {
                                self.attributes(&ResolvedEntry {
                                    path,
                                    backing: entry.backing,
                                    stat,
                                })
                            })
                        })
                }
            } else {
                let flags = if size.is_some() {
                    libc::O_RDWR
                } else {
                    libc::O_RDONLY
                };
                self.open_file(inode, flags).and_then(|handle| {
                    let result = self.with_file(FileHandle(handle), operation);
                    self.files
                        .lock()
                        .unwrap_or_else(std::sync::PoisonError::into_inner)
                        .remove(&handle);
                    result
                })
            }
        };
        match result {
            Ok(attributes) => reply.attr(&TTL, &attributes),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn readlink(&self, _request: &Request, inode: INodeNo, reply: ReplyData) {
        let result = self.path_for(inode).and_then(|path| {
            let snapshot = self.classifier.snapshot_for(&path);
            let entry = self.resolve(&snapshot, &path)?;
            self.root(entry.backing).readlink(&path)
        });
        match result {
            Ok(bytes) => reply.data(&bytes),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn mknod(
        &self,
        _request: &Request,
        parent: INodeNo,
        name: &OsStr,
        mode: u32,
        umask: u32,
        rdev: u32,
        reply: ReplyEntry,
    ) {
        if matches!(mode & libc::S_IFMT, libc::S_IFCHR | libc::S_IFBLK) {
            reply.error(Errno::EPERM);
            return;
        }
        let result = (|| {
            let path = self.child_path(parent, name)?;
            let snapshot = self.classifier.snapshot_for(&path);
            let backing = self.create_backing(&snapshot, &path, false)?;
            let root = self.root(backing);
            let parent_path = path.parent().unwrap_or_else(|| Path::new(""));
            let directory = root.open_directory(parent_path)?;
            mknodat(
                directory.as_fd(),
                name,
                rustix::fs::FileType::from_raw_mode(mode),
                Mode::from_raw_mode(mode & !umask),
                rustix::fs::makedev(rdev >> 8, rdev & 0xff),
            )?;
            Ok(path)
        })();
        match result {
            Ok(path) => self.reply_entry(&path, reply),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn mkdir(
        &self,
        _request: &Request,
        parent: INodeNo,
        name: &OsStr,
        mode: u32,
        umask: u32,
        reply: ReplyEntry,
    ) {
        let result = (|| {
            let path = self.child_path(parent, name)?;
            let snapshot = self.classifier.snapshot_for(&path);
            let backing = self.create_backing(&snapshot, &path, true)?;
            self.root(backing)
                .mkdir(&path, Mode::from_raw_mode((mode & !umask) & 0o7777))?;
            Ok(path)
        })();
        match result {
            Ok(path) => self.reply_entry(&path, reply),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn unlink(&self, _request: &Request, parent: INodeNo, name: &OsStr, reply: ReplyEmpty) {
        self.remove(parent, name, false, reply);
    }

    fn rmdir(&self, _request: &Request, parent: INodeNo, name: &OsStr, reply: ReplyEmpty) {
        self.remove(parent, name, true, reply);
    }

    fn symlink(
        &self,
        _request: &Request,
        parent: INodeNo,
        name: &OsStr,
        target: &Path,
        reply: ReplyEntry,
    ) {
        let result = (|| {
            let path = self.child_path(parent, name)?;
            let snapshot = self.classifier.snapshot_for(&path);
            let backing = self.create_backing(&snapshot, &path, false)?;
            self.root(backing).symlink(target, &path)?;
            Ok(path)
        })();
        match result {
            Ok(path) => self.reply_entry(&path, reply),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn rename(
        &self,
        _request: &Request,
        parent: INodeNo,
        name: &OsStr,
        new_parent: INodeNo,
        new_name: &OsStr,
        flags: FuseRenameFlags,
        reply: ReplyEmpty,
    ) {
        if flags.contains(FuseRenameFlags::RENAME_WHITEOUT) {
            reply.error(Errno::EOPNOTSUPP);
            return;
        }
        let result = (|| {
            let source = self.child_path(parent, name)?;
            let destination = self.child_path(new_parent, new_name)?;
            let snapshot = self.classifier.snapshot_for_paths(&[&source, &destination]);
            let source_entry = self.resolve(&snapshot, &source)?;
            let destination_backing = self.classify(
                &snapshot,
                &destination,
                source_entry.stat.st_mode & libc::S_IFMT == libc::S_IFDIR,
            );
            if source_entry.backing != destination_backing {
                return Err(io::Error::from_raw_os_error(libc::EXDEV));
            }
            if destination == Path::new(".git/index") {
                self.require_index_publication_safe(source_entry.backing, &source, &snapshot)?;
            }
            let flags = RenameFlags::from_bits_retain(flags.bits());
            self.root(source_entry.backing)
                .rename(&source, &destination, flags)
        })();
        reply_result(result, reply);
    }

    fn link(
        &self,
        _request: &Request,
        inode: INodeNo,
        new_parent: INodeNo,
        new_name: &OsStr,
        reply: ReplyEntry,
    ) {
        let result = (|| {
            let source = self.path_for(inode)?;
            let destination = self.child_path(new_parent, new_name)?;
            let snapshot = self.classifier.snapshot_for_paths(&[&source, &destination]);
            let source_entry = self.resolve(&snapshot, &source)?;
            let destination_backing = self.classify(&snapshot, &destination, false);
            if source_entry.backing != destination_backing {
                return Err(io::Error::from_raw_os_error(libc::EXDEV));
            }
            self.root(source_entry.backing)
                .link(&source, &destination)?;
            Ok(destination)
        })();
        match result {
            Ok(path) => self.reply_entry(&path, reply),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn open(&self, _request: &Request, inode: INodeNo, flags: OpenFlags, reply: ReplyOpen) {
        match self.open_file(inode, flags.0) {
            Ok(handle) => reply.opened(FileHandle(handle), FopenFlags::empty()),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn read(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        offset: u64,
        size: u32,
        _flags: OpenFlags,
        _lock_owner: Option<LockOwner>,
        reply: ReplyData,
    ) {
        let result = self.with_file(handle, |open| {
            let mut bytes = vec![0; size as usize];
            let read = open.file.read_at(&mut bytes, offset)?;
            bytes.truncate(read);
            Ok(bytes)
        });
        match result {
            Ok(bytes) => reply.data(&bytes),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn write(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        offset: u64,
        data: &[u8],
        _write_flags: WriteFlags,
        flags: OpenFlags,
        _lock_owner: Option<LockOwner>,
        reply: ReplyWrite,
    ) {
        let result = self.with_file(handle, |open| {
            let offset = if flags.0 & libc::O_APPEND != 0 {
                open.file.metadata()?.len()
            } else {
                offset
            };
            open.file.write_at(data, offset)
        });
        match result {
            Ok(written) => reply.written(u32::try_from(written).unwrap_or(u32::MAX)),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn flush(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        owner: LockOwner,
        reply: ReplyEmpty,
    ) {
        let result = self.with_file(handle, |open| {
            self.release_posix_locks(open, owner)?;
            open.file.sync_data()
        });
        reply_result(result, reply);
    }

    fn release(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        _flags: OpenFlags,
        owner: Option<LockOwner>,
        _flush: bool,
        reply: ReplyEmpty,
    ) {
        let open = self
            .files
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .remove(&handle.0);
        let result = match (open, owner) {
            (Some(open), Some(owner)) => self.release_posix_locks(&open, owner),
            (Some(_), None) => Ok(()),
            (None, _) => Err(io::Error::from_raw_os_error(libc::EBADF)),
        };
        reply_result(result, reply);
    }

    fn fsync(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        datasync: bool,
        reply: ReplyEmpty,
    ) {
        let result = self.with_file(handle, |open| {
            if datasync {
                open.file.sync_data()
            } else {
                open.file.sync_all()
            }
        });
        reply_result(result, reply);
    }

    fn getlk(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        owner: LockOwner,
        start: u64,
        end: u64,
        typ: i32,
        _pid: u32,
        flags: LockFlags,
        reply: ReplyLock,
    ) {
        if unsupported_lock_flags(flags) {
            reply.error(Errno::EOPNOTSUPP);
            return;
        }
        if flags.contains(LockFlags::FUSE_LK_FLOCK) {
            reply.locked(0, u64::MAX, libc::F_UNLCK, 0);
            return;
        }
        let result = self.with_file(handle, |open| {
            let file = self.posix_lock_file(open, owner)?;
            let mut lock = record_lock(start, end, typ)?;
            fcntl(file.as_fd(), FcntlArg::F_OFD_GETLK(&mut lock))?;
            fuse_lock(&lock)
        });
        match result {
            Ok((start, end, typ, pid)) => reply.locked(start, end, typ, pid),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn setlk(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        owner: LockOwner,
        start: u64,
        end: u64,
        typ: i32,
        _pid: u32,
        sleep: bool,
        flags: LockFlags,
        reply: ReplyEmpty,
    ) {
        if unsupported_lock_flags(flags) {
            reply.error(Errno::EOPNOTSUPP);
            return;
        }
        let result = self.with_file(handle, |open| {
            if flags.contains(LockFlags::FUSE_LK_FLOCK) {
                if (start, end) != (0, i64::MAX as u64) {
                    return Err(io::Error::from_raw_os_error(libc::EINVAL));
                }
                return Ok(bsd_flock(
                    open.file.as_fd(),
                    bsd_lock_operation(typ, sleep)?,
                )?);
            }
            let file = self.posix_lock_file(open, owner)?;
            let lock = record_lock(start, end, typ)?;
            let command = if sleep {
                FcntlArg::F_OFD_SETLKW(&lock)
            } else {
                FcntlArg::F_OFD_SETLK(&lock)
            };
            fcntl(file.as_fd(), command)?;
            Ok(())
        });
        reply_result(result, reply);
    }

    fn opendir(&self, _request: &Request, inode: INodeNo, _flags: OpenFlags, reply: ReplyOpen) {
        let result = (|| {
            let path = self.path_for(inode)?;
            let snapshot = self.classifier.snapshot_for(&path);
            let entry = self.resolve(&snapshot, &path)?;
            let directory = self.root(entry.backing).open_directory(&path)?;
            let mut entries = vec![
                DirectoryEntry {
                    inode,
                    kind: FileType::Directory,
                    name: OsString::from("."),
                },
                DirectoryEntry {
                    inode: if path.as_os_str().is_empty() {
                        INodeNo::ROOT
                    } else {
                        let parent = path.parent().unwrap_or_else(|| Path::new(""));
                        let parent_entry = self.resolve(&snapshot, parent)?;
                        self.inode_for(&parent_entry)
                    },
                    kind: FileType::Directory,
                    name: OsString::from(".."),
                },
            ];
            entries.extend(self.visible_entries(&path, &snapshot)?);
            let handle = self.next_handle.fetch_add(1, Ordering::Relaxed);
            self.directories
                .lock()
                .unwrap_or_else(std::sync::PoisonError::into_inner)
                .insert(
                    handle,
                    DirectoryStream {
                        directory,
                        entries,
                        _snapshot: snapshot,
                    },
                );
            Ok(handle)
        })();
        match result {
            Ok(handle) => reply.opened(FileHandle(handle), FopenFlags::empty()),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn readdir(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        offset: u64,
        mut reply: ReplyDirectory,
    ) {
        let directories = self
            .directories
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        let Some(directory) = directories.get(&handle.0) else {
            reply.error(Errno::EBADF);
            return;
        };
        for (index, entry) in directory
            .entries
            .iter()
            .enumerate()
            .skip(usize::try_from(offset).unwrap_or(usize::MAX))
        {
            if reply.add(entry.inode, (index + 1) as u64, entry.kind, &entry.name) {
                break;
            }
        }
        reply.ok();
    }

    fn releasedir(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        _flags: OpenFlags,
        reply: ReplyEmpty,
    ) {
        self.directories
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .remove(&handle.0);
        reply.ok();
    }

    fn fsyncdir(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        datasync: bool,
        reply: ReplyEmpty,
    ) {
        let directories = self
            .directories
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        let result = directories
            .get(&handle.0)
            .ok_or_else(|| io::Error::from_raw_os_error(libc::EBADF))
            .and_then(|stream| {
                if datasync {
                    stream.directory.sync_data()
                } else {
                    stream.directory.sync_all()
                }
            });
        reply_result(result, reply);
    }

    fn statfs(&self, _request: &Request, _inode: INodeNo, reply: ReplyStatfs) {
        match self
            .host
            .duplicate()
            .and_then(|file| Ok(fstatvfs(file.as_fd())?))
        {
            Ok(stat) => reply.statfs(
                stat.f_blocks,
                stat.f_bfree,
                stat.f_bavail,
                stat.f_files,
                stat.f_ffree,
                u32::try_from(stat.f_bsize).unwrap_or(u32::MAX),
                u32::try_from(stat.f_namemax).unwrap_or(u32::MAX),
                u32::try_from(stat.f_frsize).unwrap_or(u32::MAX),
            ),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn setxattr(
        &self,
        _request: &Request,
        inode: INodeNo,
        name: &OsStr,
        value: &[u8],
        flags: i32,
        position: u32,
        reply: ReplyEmpty,
    ) {
        if position != 0 || !writable_xattr(name) {
            reply.error(Errno::ENOTSUP);
            return;
        }
        let result = self.with_temporary_file(inode, |file| {
            Ok(fsetxattr(
                file.as_fd(),
                name,
                value,
                XattrFlags::from_bits_retain(u32::from_ne_bytes(flags.to_ne_bytes())),
            )?)
        });
        reply_result(result, reply);
    }

    fn getxattr(
        &self,
        _request: &Request,
        inode: INodeNo,
        name: &OsStr,
        size: u32,
        reply: ReplyXattr,
    ) {
        let result = self.with_temporary_file(inode, |file| {
            let mut bytes = vec![0; 64 * 1024];
            let length = fgetxattr(file.as_fd(), name, &mut bytes)?;
            bytes.truncate(length);
            Ok(bytes)
        });
        reply_xattr(result, size, reply);
    }

    fn listxattr(&self, _request: &Request, inode: INodeNo, size: u32, reply: ReplyXattr) {
        let result = self.with_temporary_file(inode, |file| {
            let mut bytes = vec![0; 64 * 1024];
            let length = flistxattr(file.as_fd(), &mut bytes)?;
            bytes.truncate(length);
            Ok(bytes)
        });
        reply_xattr(result, size, reply);
    }

    fn removexattr(&self, _request: &Request, inode: INodeNo, name: &OsStr, reply: ReplyEmpty) {
        if !writable_xattr(name) {
            reply.error(Errno::ENOTSUP);
            return;
        }
        let result = self.with_temporary_file(inode, |file| Ok(fremovexattr(file.as_fd(), name)?));
        reply_result(result, reply);
    }

    fn create(
        &self,
        _request: &Request,
        parent: INodeNo,
        name: &OsStr,
        mode: u32,
        umask: u32,
        flags: i32,
        reply: ReplyCreate,
    ) {
        let result = (|| {
            let path = self.child_path(parent, name)?;
            let snapshot = self.classifier.snapshot_for(&path);
            let backing = self.create_backing(&snapshot, &path, false)?;
            let file = self.root(backing).open_entry(
                &path,
                open_flags(flags) | OFlags::CREATE,
                Mode::from_raw_mode((mode & !umask) & 0o7777),
            )?;
            let stat = fstat(file.as_fd())?;
            let attributes = self.attributes(&ResolvedEntry {
                path,
                backing,
                stat,
            })?;
            let handle = self.next_handle.fetch_add(1, Ordering::Relaxed);
            self.files
                .lock()
                .unwrap_or_else(std::sync::PoisonError::into_inner)
                .insert(
                    handle,
                    Arc::new(OpenFile {
                        file,
                        backing,
                        access_mode: flags & libc::O_ACCMODE,
                    }),
                );
            Ok((attributes, handle))
        })();
        match result {
            Ok((attributes, handle)) => reply.created(
                &TTL,
                &attributes,
                Generation(0),
                FileHandle(handle),
                FopenFlags::empty(),
            ),
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn fallocate(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        offset: u64,
        length: u64,
        mode: i32,
        reply: ReplyEmpty,
    ) {
        let result = self.with_file(handle, |open| {
            Ok(fallocate(
                open.file.as_fd(),
                FallocateFlags::from_bits_retain(u32::from_ne_bytes(mode.to_ne_bytes())),
                offset,
                length,
            )?)
        });
        reply_result(result, reply);
    }

    fn lseek(
        &self,
        _request: &Request,
        _inode: INodeNo,
        handle: FileHandle,
        offset: i64,
        whence: i32,
        reply: ReplyLseek,
    ) {
        let position = match whence {
            libc::SEEK_SET => u64::try_from(offset).ok().map(SeekFrom::Start),
            libc::SEEK_CUR => Some(SeekFrom::Current(offset)),
            libc::SEEK_END => Some(SeekFrom::End(offset)),
            libc::SEEK_DATA => u64::try_from(offset).ok().map(SeekFrom::Data),
            libc::SEEK_HOLE => u64::try_from(offset).ok().map(SeekFrom::Hole),
            _ => None,
        };
        let result = position
            .ok_or_else(|| io::Error::from_raw_os_error(libc::EINVAL))
            .and_then(|position| {
                self.with_file(handle, |open| Ok(seek(open.file.as_fd(), position)?))
            });
        match result {
            Ok(position) => match i64::try_from(position) {
                Ok(position) => reply.offset(position),
                Err(_) => reply.error(Errno::EOVERFLOW),
            },
            Err(error) => reply.error(errno(&error)),
        }
    }

    fn copy_file_range(
        &self,
        _request: &Request,
        _inode_in: INodeNo,
        handle_in: FileHandle,
        offset_in: u64,
        _inode_out: INodeNo,
        handle_out: FileHandle,
        offset_out: u64,
        length: u64,
        flags: CopyFileRangeFlags,
        reply: ReplyWrite,
    ) {
        if !flags.is_empty() {
            reply.error(Errno::EINVAL);
            return;
        }
        let files = self
            .files
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        let result = (|| {
            let input = files
                .get(&handle_in.0)
                .ok_or_else(|| io::Error::from_raw_os_error(libc::EBADF))?;
            let output = files
                .get(&handle_out.0)
                .ok_or_else(|| io::Error::from_raw_os_error(libc::EBADF))?;
            if input.backing != output.backing {
                return Err(io::Error::from_raw_os_error(libc::EXDEV));
            }
            let mut input_offset = offset_in;
            let mut output_offset = offset_out;
            copy_file_range(
                input.file.as_fd(),
                Some(&mut input_offset),
                output.file.as_fd(),
                Some(&mut output_offset),
                usize::try_from(length).unwrap_or(usize::MAX),
            )
            .map_err(io::Error::from)
        })();
        match result {
            Ok(written) => reply.written(u32::try_from(written).unwrap_or(u32::MAX)),
            Err(error) => reply.error(errno(&error)),
        }
    }
}