rencfs 0.14.11

use argon2::password_hash::rand_core::RngCore;
use async_trait::async_trait;
use futures_util::TryStreamExt;
use lru::LruCache;
use num_format::{Locale, ToFormattedString};
use serde::{Deserialize, Serialize};
use shush_rs::{ExposeSecret, SecretBox, SecretString, SecretVec};
use std::backtrace::Backtrace;
use std::collections::{HashMap, HashSet, VecDeque};
use std::fmt::Debug;
use std::fs::{DirEntry, File, OpenOptions, ReadDir};
use std::io::{Read, Seek, SeekFrom, Write};
use std::num::{NonZeroUsize, ParseIntError};
use std::path::{Path, PathBuf};
use std::str::FromStr;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::{Arc, LazyLock, Weak};
use std::time::{Duration, SystemTime};
use std::{fs, io};
use thiserror::Error;
use tokio::runtime::Runtime;
use tokio::sync::{Mutex, RwLock};
use tokio::task::{JoinError, JoinSet};
use tokio_stream::wrappers::ReadDirStream;
use tracing::{debug, error, info, instrument, warn, Level};

use crate::arc_hashmap::ArcHashMap;
use crate::crypto::read::{CryptoRead, CryptoReadSeek};
use crate::crypto::write::{CryptoInnerWriter, CryptoWrite, CryptoWriteSeek};
use crate::crypto::Cipher;
use crate::expire_value::{ExpireValue, ValueProvider};
use crate::{crypto, fs_util, stream_util};
use bon::bon;

mod bench;
#[cfg(test)]
mod test;

pub(crate) const INODES_DIR: &str = "inodes";
pub(crate) const CONTENTS_DIR: &str = "contents";
pub(crate) const SECURITY_DIR: &str = "security";
pub(crate) const KEY_ENC_FILENAME: &str = "key.enc";
pub(crate) const KEY_SALT_FILENAME: &str = "key.salt";

pub(crate) const LS_DIR: &str = "ls";
pub(crate) const HASH_DIR: &str = "hash";

pub(crate) const ROOT_INODE: u64 = 1;

fn spawn_runtime() -> Runtime {
    let runtime = tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()
        .unwrap();
    runtime
}

static DIR_ENTRIES_RT: LazyLock<Runtime> = LazyLock::new(spawn_runtime);
static NOD_RT: LazyLock<Runtime> = LazyLock::new(spawn_runtime);

/// File attributes.
#[derive(Clone, Copy, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub struct FileAttr {
    /// Inode number
    pub ino: u64,
    /// Size in bytes
    pub size: u64,
    /// Size in blocks
    pub blocks: u64,
    /// Time of last access
    pub atime: SystemTime,
    /// Time of last modification
    pub mtime: SystemTime,
    /// Time of last change
    pub ctime: SystemTime,
    /// Time of creation (macOS only)
    pub crtime: SystemTime,
    /// Kind of file (directory, file, pipe, etc.)
    pub kind: FileType,
    /// Permissions
    pub perm: u16,
    /// Number of hard links
    pub nlink: u32,
    /// User id
    pub uid: u32,
    /// Group id
    pub gid: u32,
    /// Rdev
    pub rdev: u32,
    /// Block size
    pub blksize: u32,
    /// Flags (macOS only, see chflags(2))
    pub flags: u32,
}

/// File types.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, Serialize, Deserialize)]
pub enum FileType {
    // /// Named pipe (S_IFIFO)
    // NamedPipe,
    // /// Character device (S_IFCHR)
    // CharDevice,
    // /// Block device (S_IFBLK)
    // BlockDevice,
    /// Directory (`S_IFDIR`)
    Directory,
    /// Regular file (`S_IFREG`)
    RegularFile,
    // /// Symbolic link (S_IFLNK)
    // Symlink,
    // /// Unix domain socket (S_IFSOCK)
    // Socket,
}

#[derive(Debug, Clone, Copy, Default)]
pub struct SetFileAttr {
    /// Size in bytes
    pub size: Option<u64>,
    /// Time of last access
    pub atime: Option<SystemTime>,
    /// Time of last modification
    pub mtime: Option<SystemTime>,
    /// Time of last change
    pub ctime: Option<SystemTime>,
    /// Time of creation (macOS only)
    pub crtime: Option<SystemTime>,
    /// Permissions
    pub perm: Option<u16>,
    /// User id
    pub uid: Option<u32>,
    /// Group id
    pub gid: Option<u32>,
    /// Rdev
    pub rdev: Option<u32>,
    /// Flags (macOS only, see chflags(2))
    pub flags: Option<u32>,
}

impl SetFileAttr {
    #[must_use]
    pub const fn with_size(mut self, size: u64) -> Self {
        self.size = Some(size);
        self
    }

    #[must_use]
    pub const fn with_atime(mut self, atime: SystemTime) -> Self {
        self.atime = Some(atime);
        self
    }

    #[must_use]
    pub const fn with_mtime(mut self, mtime: SystemTime) -> Self {
        self.mtime = Some(mtime);
        self
    }

    #[must_use]
    pub const fn with_ctime(mut self, ctime: SystemTime) -> Self {
        self.ctime = Some(ctime);
        self
    }

    #[must_use]
    pub const fn with_crtime(mut self, crtime: SystemTime) -> Self {
        self.crtime = Some(crtime);
        self
    }

    #[must_use]
    pub const fn with_perm(mut self, perm: u16) -> Self {
        self.perm = Some(perm);
        self
    }

    #[must_use]
    pub const fn with_uid(mut self, uid: u32) -> Self {
        self.uid = Some(uid);
        self
    }

    #[must_use]
    pub const fn with_gid(mut self, gid: u32) -> Self {
        self.gid = Some(gid);
        self
    }

    #[must_use]
    pub const fn with_rdev(mut self, rdev: u32) -> Self {
        self.rdev = Some(rdev);
        self
    }

    #[must_use]
    pub const fn with_flags(mut self, flags: u32) -> Self {
        self.rdev = Some(flags);
        self
    }
}

#[derive(Debug, Clone)]
pub struct CreateFileAttr {
    /// Kind of file (directory, file, pipe, etc.)
    pub kind: FileType,
    /// Permissions
    pub perm: u16,
    /// User id
    pub uid: u32,
    /// Group id
    pub gid: u32,
    /// Rdev
    pub rdev: u32,
    /// Flags (macOS only, see chflags(2))
    pub flags: u32,
}

impl From<CreateFileAttr> for FileAttr {
    fn from(value: CreateFileAttr) -> Self {
        let now = SystemTime::now();
        Self {
            ino: 0,
            size: 0,
            blocks: 0,
            atime: now,
            mtime: now,
            ctime: now,
            crtime: now,
            kind: value.kind,
            perm: value.perm,
            nlink: if value.kind == FileType::Directory {
                2
            } else {
                1
            },
            uid: value.uid,
            gid: value.gid,
            rdev: value.rdev,
            blksize: 0,
            flags: value.flags,
        }
    }
}

#[derive(Error, Debug)]
pub enum FsError {
    #[error("IO error: {source}")]
    Io {
        #[from]
        source: io::Error,
        backtrace: Backtrace,
    },
    #[error("serialize error: {source}")]
    SerializeError {
        #[from]
        source: bincode::Error,
        backtrace: Backtrace,
    },
    #[error("item not found: {0}")]
    NotFound(&'static str),
    #[error("inode not found")]
    InodeNotFound,
    #[error("invalid input")]
    InvalidInput(&'static str),
    #[error("invalid node type")]
    InvalidInodeType,
    #[error("invalid file handle")]
    InvalidFileHandle,
    #[error("already exists")]
    AlreadyExists,
    #[error("already open for write")]
    AlreadyOpenForWrite,
    #[error("not empty")]
    NotEmpty,
    #[error("other: {0}")]
    Other(&'static str),
    #[error("invalid password")]
    InvalidPassword,
    #[error("invalid structure of data directory")]
    InvalidDataDirStructure,
    #[error("crypto error: {source}")]
    Crypto {
        #[from]
        source: crypto::Error,
        backtrace: Backtrace,
    },
    #[error("keyring error: {source}")]
    Keyring {
        #[from]
        source: keyring::Error,
        backtrace: Backtrace,
    },
    #[error("parse int error: {source}")]
    ParseIntError {
        #[from]
        source: ParseIntError,
        backtrace: Backtrace,
    },
    #[error("tokio join error: {source}")]
    JoinError {
        #[from]
        source: JoinError,
        backtrace: Backtrace,
    },
    #[error("max filesize exceeded, max allowed {0}")]
    MaxFilesizeExceeded(usize),
    #[error("Read only mode is active.")]
    ReadOnly,
}

#[derive(Debug, Clone)]
struct TimesAndSizeFileAttr {
    atime: SystemTime,
    mtime: SystemTime,
    ctime: SystemTime,
    crtime: SystemTime,
    size: u64,
}

impl TimesAndSizeFileAttr {
    #[allow(dead_code)]
    const fn new(
        atime: SystemTime,
        mtime: SystemTime,
        ctime: SystemTime,
        crtime: SystemTime,
        size: u64,
    ) -> Self {
        Self {
            atime,
            mtime,
            ctime,
            crtime,
            size,
        }
    }
}

impl From<FileAttr> for TimesAndSizeFileAttr {
    fn from(value: FileAttr) -> Self {
        Self {
            atime: value.atime,
            mtime: value.mtime,
            ctime: value.ctime,
            crtime: value.crtime,
            size: value.size,
        }
    }
}

impl From<TimesAndSizeFileAttr> for SetFileAttr {
    fn from(value: TimesAndSizeFileAttr) -> Self {
        Self::default()
            .with_atime(value.atime)
            .with_mtime(value.mtime)
            .with_ctime(value.ctime)
            .with_crtime(value.crtime)
            .with_size(value.size)
    }
}

#[derive(Debug, Clone)]
struct TimesFileAttr {
    atime: SystemTime,
    mtime: SystemTime,
    ctime: SystemTime,
    crtime: SystemTime,
}

impl TimesFileAttr {
    #[allow(dead_code)]
    const fn new(
        atime: SystemTime,
        mtime: SystemTime,
        ctime: SystemTime,
        crtime: SystemTime,
    ) -> Self {
        Self {
            atime,
            mtime,
            ctime,
            crtime,
        }
    }
}

impl From<FileAttr> for TimesFileAttr {
    fn from(value: FileAttr) -> Self {
        Self {
            atime: value.atime,
            mtime: value.mtime,
            ctime: value.ctime,
            crtime: value.crtime,
        }
    }
}

impl From<TimesFileAttr> for SetFileAttr {
    fn from(value: TimesFileAttr) -> Self {
        Self::default()
            .with_atime(value.atime)
            .with_mtime(value.mtime)
            .with_ctime(value.ctime)
            .with_crtime(value.crtime)
    }
}

#[derive(Debug, Clone)]
pub struct DirectoryEntry {
    pub ino: u64,
    pub name: SecretString,
    pub kind: FileType,
}

impl PartialEq for DirectoryEntry {
    fn eq(&self, other: &Self) -> bool {
        self.ino == other.ino
            && self.name.expose_secret() == other.name.expose_secret()
            && self.kind == other.kind
    }
}

/// Like [`DirectoryEntry`] but with [`FileAttr`].
#[derive(Debug)]
pub struct DirectoryEntryPlus {
    pub ino: u64,
    pub name: SecretString,
    pub kind: FileType,
    pub attr: FileAttr,
}

impl PartialEq for DirectoryEntryPlus {
    fn eq(&self, other: &Self) -> bool {
        self.ino == other.ino
            && self.name.expose_secret() == other.name.expose_secret()
            && self.kind == other.kind
            && self.attr == other.attr
    }
}

pub type FsResult<T> = Result<T, FsError>;

pub struct DirectoryEntryIterator(VecDeque<FsResult<DirectoryEntry>>);

impl Iterator for DirectoryEntryIterator {
    type Item = FsResult<DirectoryEntry>;

    fn next(&mut self) -> Option<Self::Item> {
        self.0.pop_front()
    }
}

pub struct DirectoryEntryPlusIterator(VecDeque<FsResult<DirectoryEntryPlus>>);

impl Iterator for DirectoryEntryPlusIterator {
    type Item = FsResult<DirectoryEntryPlus>;

    #[instrument(name = "DirectoryEntryPlusIterator::next", skip(self))]
    fn next(&mut self) -> Option<Self::Item> {
        self.0.pop_front()
    }
}

struct ReadHandleContext {
    ino: u64,
    attr: TimesFileAttr,
    reader: Option<Box<dyn CryptoReadSeek<File>>>,
}

enum ReadHandleContextOperation {
    Create { ino: u64 },
}

impl ReadHandleContextOperation {
    const fn get_ino(&self) -> u64 {
        match *self {
            Self::Create { ino, .. } => ino,
        }
    }
}

enum WriteHandleContextOperation {
    Create { ino: u64 },
}

impl WriteHandleContextOperation {
    const fn get_ino(&self) -> u64 {
        match *self {
            Self::Create { ino, .. } => ino,
        }
    }
}

struct WriteHandleContext {
    ino: u64,
    attr: TimesAndSizeFileAttr,
    writer: Option<Box<dyn CryptoWriteSeek<File>>>,
}

struct KeyProvider {
    key_path: PathBuf,
    salt_path: PathBuf,
    password_provider: Box<dyn PasswordProvider>,
    cipher: Cipher,
}

#[async_trait]
impl ValueProvider<SecretVec<u8>, FsError> for KeyProvider {
    async fn provide(&self) -> Result<SecretVec<u8>, FsError> {
        let password = self
            .password_provider
            .get_password()
            .ok_or(FsError::InvalidPassword)?;
        read_or_create_key(&self.key_path, &self.salt_path, &password, self.cipher)
    }
}

pub trait PasswordProvider: Send + Sync + 'static {
    fn get_password(&self) -> Option<SecretString>;
}

struct DirEntryNameCacheProvider {}
#[async_trait]
impl ValueProvider<Mutex<LruCache<String, SecretString>>, FsError> for DirEntryNameCacheProvider {
    async fn provide(&self) -> Result<Mutex<LruCache<String, SecretString>>, FsError> {
        Ok(Mutex::new(LruCache::new(NonZeroUsize::new(2000).unwrap())))
    }
}

struct DirEntryMetaCacheProvider {}
#[async_trait]
impl ValueProvider<Mutex<DirEntryMetaCache>, FsError> for DirEntryMetaCacheProvider {
    async fn provide(&self) -> Result<Mutex<DirEntryMetaCache>, FsError> {
        Ok(Mutex::new(LruCache::new(NonZeroUsize::new(2000).unwrap())))
    }
}

struct AttrCacheProvider {}
#[async_trait]
impl ValueProvider<RwLock<LruCache<u64, FileAttr>>, FsError> for AttrCacheProvider {
    async fn provide(&self) -> Result<RwLock<LruCache<u64, FileAttr>>, FsError> {
        Ok(RwLock::new(LruCache::new(NonZeroUsize::new(2000).unwrap())))
    }
}

type DirEntryMetaCache = LruCache<String, (u64, FileType)>;

/// Encrypted FS that stores encrypted files in a dedicated directory with a specific structure based on `inode`.
pub struct EncryptedFs {
    pub(crate) data_dir: PathBuf,
    write_handles: RwLock<HashMap<u64, Mutex<WriteHandleContext>>>,
    read_handles: RwLock<HashMap<u64, Mutex<ReadHandleContext>>>,
    current_handle: AtomicU64,
    cipher: Cipher,
    // (ino, fh)
    opened_files_for_read: RwLock<HashMap<u64, HashSet<u64>>>,
    opened_files_for_write: RwLock<HashMap<u64, u64>>,
    // used for rw ops of actual serialization
    // use std::sync::RwLock instead of tokio::sync::RwLock because we need to use it also in sync code in `DirectoryEntryIterator` and `DirectoryEntryPlusIterator`
    serialize_inode_locks: Arc<ArcHashMap<u64, RwLock<bool>>>,
    // used for the update op
    serialize_update_inode_locks: ArcHashMap<u64, Mutex<bool>>,
    // use std::sync::RwLock instead of tokio::sync::RwLock because we need to use it also in sync code in `DirectoryEntryIterator` and `DirectoryEntryPlusIterator`
    serialize_dir_entries_ls_locks: Arc<ArcHashMap<String, RwLock<bool>>>,
    serialize_dir_entries_hash_locks: Arc<ArcHashMap<String, RwLock<bool>>>,
    read_write_locks: ArcHashMap<u64, RwLock<bool>>,
    key: ExpireValue<SecretVec<u8>, FsError, KeyProvider>,
    self_weak: std::sync::Mutex<Option<Weak<Self>>>,
    attr_cache: ExpireValue<RwLock<LruCache<u64, FileAttr>>, FsError, AttrCacheProvider>,
    dir_entries_name_cache:
        ExpireValue<Mutex<LruCache<String, SecretString>>, FsError, DirEntryNameCacheProvider>,
    dir_entries_meta_cache:
        ExpireValue<Mutex<DirEntryMetaCache>, FsError, DirEntryMetaCacheProvider>,
    sizes_write: Mutex<HashMap<u64, AtomicU64>>,
    sizes_read: Mutex<HashMap<u64, AtomicU64>>,
    requested_read: Mutex<HashMap<u64, AtomicU64>>,
    read_only: bool,
}

impl EncryptedFs {
    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::missing_errors_doc)]
    pub async fn new(
        data_dir: PathBuf,
        password_provider: Box<dyn PasswordProvider>,
        cipher: Cipher,
        read_only: bool,
    ) -> FsResult<Arc<Self>> {
        let key_provider = KeyProvider {
            key_path: data_dir.join(SECURITY_DIR).join(KEY_ENC_FILENAME),
            salt_path: data_dir.join(SECURITY_DIR).join(KEY_SALT_FILENAME),
            password_provider,
            cipher,
        };
        let key = ExpireValue::new(key_provider, Duration::from_secs(10 * 60));

        ensure_structure_created(&data_dir.clone()).await?;
        key.get().await?; // this will check the password

        let fs = Self {
            data_dir,
            write_handles: RwLock::new(HashMap::new()),
            read_handles: RwLock::new(HashMap::new()),
            current_handle: AtomicU64::new(1),
            cipher,
            opened_files_for_read: RwLock::new(HashMap::new()),
            opened_files_for_write: RwLock::new(HashMap::new()),
            serialize_inode_locks: Arc::new(ArcHashMap::default()),
            serialize_update_inode_locks: ArcHashMap::default(),
            serialize_dir_entries_ls_locks: Arc::new(ArcHashMap::default()),
            serialize_dir_entries_hash_locks: Arc::new(ArcHashMap::default()),
            key,
            self_weak: std::sync::Mutex::new(None),
            read_write_locks: ArcHashMap::default(),
            // todo: take duration from param
            attr_cache: ExpireValue::new(AttrCacheProvider {}, Duration::from_secs(10 * 60)),
            // todo: take duration from param
            dir_entries_name_cache: ExpireValue::new(
                DirEntryNameCacheProvider {},
                Duration::from_secs(10 * 60),
            ),
            // todo: take duration from param
            dir_entries_meta_cache: ExpireValue::new(
                DirEntryMetaCacheProvider {},
                Duration::from_secs(10 * 60),
            ),
            sizes_write: Mutex::default(),
            sizes_read: Mutex::default(),
            requested_read: Mutex::default(),
            read_only,
        };

        let arc = Arc::new(fs);
        arc.self_weak
            .lock()
            .expect("cannot obtain lock")
            .replace(Arc::downgrade(&arc));

        arc.ensure_root_exists().await?;

        Ok(arc)
    }

    pub fn exists(&self, ino: u64) -> bool {
        self.ino_file(ino).is_file()
    }

    pub fn is_dir(&self, ino: u64) -> bool {
        self.contents_path(ino).is_dir()
    }

    pub fn is_file(&self, ino: u64) -> bool {
        self.contents_path(ino).is_file()
    }

    #[allow(dead_code)]
    async fn is_read_only(&self) -> bool {
        self.read_only
    }

    fn validate_filename(&self, secret_filename: &SecretBox<String>) -> FsResult<()> {
        let filename = secret_filename.expose_secret().to_string();
        if filename.contains('/') {
            Err(FsError::InvalidInput("'/' not allowed in the filename"))
        } else if filename.contains('\\') {
            Err(FsError::InvalidInput("'\\' not allowed in the filename"))
        } else {
            Ok(())
        }
    }

    /// Create a new node in the filesystem
    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::missing_errors_doc)]
    #[allow(clippy::too_many_lines)]
    pub async fn create(
        &self,
        parent: u64,
        name: &SecretString,
        create_attr: CreateFileAttr,
        read: bool,
        write: bool,
    ) -> FsResult<(u64, FileAttr)> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if *name.expose_secret() == "." || *name.expose_secret() == ".." {
            return Err(FsError::InvalidInput("name cannot be '.' or '..'"));
        }
        if !self.exists(parent) {
            return Err(FsError::InodeNotFound);
        }
        if self.exists_by_name(parent, name)? {
            return Err(FsError::AlreadyExists);
        }
        self.validate_filename(name)?;

        // spawn on a dedicated runtime to not interfere with other higher priority tasks
        let self_clone = self
            .self_weak
            .lock()
            .unwrap()
            .as_ref()
            .unwrap()
            .upgrade()
            .unwrap();
        let name_clone = name.clone();
        NOD_RT
            .spawn(async move {
                let mut attr: FileAttr = create_attr.into();
                attr.ino = self_clone.generate_next_inode();

                let fs = self_clone;
                let mut join_set = JoinSet::new();

                // write inode
                let self_clone = fs.clone();
                self_clone.write_inode_to_storage(&attr).await?;

                match attr.kind {
                    FileType::RegularFile => {
                        let self_clone = fs.clone();
                        join_set.spawn(async move {
                            // create in contents directory
                            let file = File::create(self_clone.contents_path(attr.ino))?;
                            // sync_all file and parent
                            // these operations are a bit slow, but are necessary to make sure the file is correctly created
                            // i.e. creating 100 files takes 0.965 sec with sync_all and 0.130 sec without
                            file.sync_all()?;
                            File::open(
                                self_clone
                                    .contents_path(attr.ino)
                                    .parent()
                                    .expect("oops, we don't have a parent"),
                            )?
                            .sync_all()?;
                            Ok::<(), FsError>(())
                        });
                    }
                    FileType::Directory => {
                        let self_clone = fs.clone();
                        let attr_clone = attr;
                        join_set.spawn(async move {
                            // create in contents directory
                            let contents_dir = self_clone.contents_path(attr.ino);
                            fs::create_dir(contents_dir.clone())?;
                            // used to keep encrypted file names used by [`read_dir`] and [`read_dir_plus`]
                            fs::create_dir(contents_dir.join(LS_DIR))?;
                            // used to keep hashes of encrypted file names used by [`exists_by_name`] and [`find_by_name`]
                            // this optimizes the search process as we don't need to decrypt all file names and search
                            fs::create_dir(contents_dir.join(HASH_DIR))?;

                            // add "." and ".." entries
                            self_clone
                                .insert_directory_entry(
                                    attr_clone.ino,
                                    &DirectoryEntry {
                                        ino: attr_clone.ino,
                                        name: SecretString::new(Box::new("$.".into())),
                                        kind: FileType::Directory,
                                    },
                                )
                                .await?;
                            self_clone
                                .insert_directory_entry(
                                    attr_clone.ino,
                                    &DirectoryEntry {
                                        ino: parent,
                                        name: SecretString::new(Box::new("$..".into())),
                                        kind: FileType::Directory,
                                    },
                                )
                                .await?;
                            Ok::<(), FsError>(())
                        });
                    }
                }

                // edd entry in parent directory, used for listing
                let self_clone = fs.clone();
                let attr_clone = attr;
                join_set.spawn(async move {
                    self_clone
                        .insert_directory_entry(
                            parent,
                            &DirectoryEntry {
                                ino: attr_clone.ino,
                                name: name_clone,
                                kind: attr_clone.kind,
                            },
                        )
                        .await?;
                    Ok::<(), FsError>(())
                });

                let self_clone = fs.clone();
                join_set.spawn(async move {
                    let now = SystemTime::now();
                    self_clone
                        .set_attr(
                            parent,
                            SetFileAttr::default()
                                .with_mtime(now)
                                .with_ctime(now)
                                .with_atime(now),
                        )
                        .await?;
                    Ok::<(), FsError>(())
                });

                // wait for all tasks to finish
                while let Some(res) = join_set.join_next().await {
                    res??;
                }

                let self_clone = fs.clone();
                let handle = if attr.kind == FileType::RegularFile {
                    if read || write {
                        self_clone.open(attr.ino, read, write).await?
                    } else {
                        // we don't create a handle for files that are not opened
                        0
                    }
                } else {
                    // we don't use a handle for directories
                    0
                };

                Ok((handle, attr))
            })
            .await?
    }

    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::missing_errors_doc)]
    pub async fn find_by_name(
        &self,
        parent: u64,
        name: &SecretString,
    ) -> FsResult<Option<FileAttr>> {
        if !self.exists(parent) {
            return Err(FsError::InodeNotFound);
        }
        if !self.is_dir(parent) {
            return Err(FsError::InvalidInodeType);
        }
        let hash = crypto::hash_file_name(name);
        let hash_path = self.contents_path(parent).join(HASH_DIR).join(hash);
        if !hash_path.is_file() {
            return Ok(None);
        }
        let lock = self
            .serialize_dir_entries_hash_locks
            .get_or_insert_with(hash_path.to_str().unwrap().to_owned(), || {
                RwLock::new(false)
            });
        let guard = lock.read().await;
        let (ino, _, _): (u64, FileType, String) = bincode::deserialize_from(crypto::create_read(
            File::open(hash_path)?,
            self.cipher,
            &*self.key.get().await?,
        ))?;
        drop(guard);
        self.get_inode_from_cache_or_storage(ino).await.map(Some)
    }

    /// Count children of a directory. This **EXCLUDES** "." and "..".
    #[allow(clippy::missing_errors_doc)]
    pub fn len(&self, ino: u64) -> FsResult<usize> {
        if !self.is_dir(ino) {
            return Err(FsError::InvalidInodeType);
        }
        let mut count = fs::read_dir(self.contents_path(ino).join(LS_DIR))?.count();
        if ino == ROOT_INODE {
            // we don't count "."
            count -= 1;
        } else {
            // we don't count "." and ".."
            count -= 2;
        }
        Ok(count)
    }

    /// Delete a directory
    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::missing_errors_doc)]
    pub async fn remove_dir(&self, parent: u64, name: &SecretString) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if !self.is_dir(parent) {
            return Err(FsError::InvalidInodeType);
        }

        if !self.exists_by_name(parent, name)? {
            return Err(FsError::NotFound("name not found"));
        }

        let attr = self
            .find_by_name(parent, name)
            .await?
            .ok_or(FsError::NotFound("name not found"))?;
        if !matches!(attr.kind, FileType::Directory) {
            return Err(FsError::InvalidInodeType);
        }
        // check if it's empty
        if self.len(attr.ino)? > 0 {
            return Err(FsError::NotEmpty);
        }
        let self_clone = self
            .self_weak
            .lock()
            .unwrap()
            .as_ref()
            .unwrap()
            .upgrade()
            .unwrap();
        let name_clone = name.clone();
        NOD_RT
            .spawn(async move {
                // remove inode file
                {
                    let lock = self_clone
                        .serialize_inode_locks
                        .get_or_insert_with(attr.ino, || RwLock::new(false));
                    let _guard = lock.write();
                    fs::remove_file(self_clone.ino_file(attr.ino))?;
                }

                // remove contents directory
                fs::remove_dir_all(self_clone.contents_path(attr.ino))?;
                // remove from parent directory
                self_clone
                    .remove_directory_entry(parent, &name_clone)
                    .await?;
                // remove from cache
                self_clone
                    .attr_cache
                    .get()
                    .await?
                    .write()
                    .await
                    .demote(&attr.ino);

                let now = SystemTime::now();
                self_clone
                    .set_attr(
                        parent,
                        SetFileAttr::default()
                            .with_mtime(now)
                            .with_ctime(now)
                            .with_atime(now),
                    )
                    .await?;

                Ok(())
            })
            .await?
    }

    /// Delete a file
    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::missing_errors_doc)]
    pub async fn remove_file(&self, parent: u64, name: &SecretString) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if !self.is_dir(parent) {
            return Err(FsError::InvalidInodeType);
        }
        if !self.exists_by_name(parent, name)? {
            return Err(FsError::NotFound("name not found"));
        }

        let attr = self
            .find_by_name(parent, name)
            .await?
            .ok_or(FsError::NotFound("name not found"))?;
        if !matches!(attr.kind, FileType::RegularFile) {
            return Err(FsError::InvalidInodeType);
        }
        // todo move to method
        let self_clone = self
            .self_weak
            .lock()
            .unwrap()
            .as_ref()
            .unwrap()
            .upgrade()
            .unwrap();
        let name_clone = name.clone();
        NOD_RT
            .spawn(async move {
                // remove inode file
                {
                    let lock = self_clone
                        .serialize_inode_locks
                        .get_or_insert_with(attr.ino, || RwLock::new(false));
                    let _guard = lock.write();
                    fs::remove_file(self_clone.ino_file(attr.ino))?;
                }

                // remove from contents directory
                fs::remove_file(self_clone.contents_path(attr.ino))?;
                // remove from parent directory
                self_clone
                    .remove_directory_entry(parent, &name_clone)
                    .await?;
                // remove from cache
                self_clone
                    .attr_cache
                    .get()
                    .await?
                    .write()
                    .await
                    .demote(&attr.ino);

                let now = SystemTime::now();
                self_clone
                    .set_attr(
                        parent,
                        SetFileAttr::default()
                            .with_mtime(now)
                            .with_ctime(now)
                            .with_atime(now),
                    )
                    .await?;

                Ok(())
            })
            .await?
    }

    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::missing_errors_doc)]
    pub fn exists_by_name(&self, parent: u64, name: &SecretString) -> FsResult<bool> {
        if !self.exists(parent) {
            return Err(FsError::InodeNotFound);
        }
        if !self.is_dir(parent) {
            return Err(FsError::InvalidInodeType);
        }
        let hash = crypto::hash_file_name(name);
        let hash_path = self.contents_path(parent).join(HASH_DIR).join(hash);
        Ok(hash_path.is_file())
    }

    #[allow(clippy::missing_errors_doc)]
    pub async fn read_dir(&self, ino: u64) -> FsResult<DirectoryEntryIterator> {
        if !self.is_dir(ino) {
            return Err(FsError::InvalidInodeType);
        }
        let ls_dir = self.contents_path(ino).join(LS_DIR);
        if !ls_dir.is_dir() {
            return Err(FsError::InvalidInodeType);
        }

        let iter = fs::read_dir(ls_dir)?;
        let set_attr = SetFileAttr::default().with_atime(SystemTime::now());
        self.set_attr(ino, set_attr).await?;
        Ok(self.create_directory_entry_iterator(iter).await)
    }

    /// Like [`EncryptedFs::read_dir`] but with [`FileAttr`] so we don't need to query again for those.
    pub async fn read_dir_plus(&self, ino: u64) -> FsResult<DirectoryEntryPlusIterator> {
        if !self.is_dir(ino) {
            return Err(FsError::InvalidInodeType);
        }
        let ls_dir = self.contents_path(ino).join(LS_DIR);
        if !ls_dir.is_dir() {
            return Err(FsError::InvalidInodeType);
        }

        let iter = fs::read_dir(ls_dir)?;
        let set_attr = SetFileAttr::default().with_atime(SystemTime::now());
        self.set_attr(ino, set_attr).await?;
        Ok(self.create_directory_entry_plus_iterator(iter).await)
    }

    async fn create_directory_entry_plus(
        &self,
        entry: io::Result<DirEntry>,
    ) -> FsResult<DirectoryEntryPlus> {
        let entry = self.create_directory_entry(entry).await?;
        let lock = self.serialize_inode_locks.clone();
        let lock_ino = lock.get_or_insert_with(entry.ino, || RwLock::new(false));
        let _ino_guard = lock_ino.read();
        let attr = self.get_inode_from_cache_or_storage(entry.ino).await?;
        Ok(DirectoryEntryPlus {
            ino: entry.ino,
            name: entry.name,
            kind: entry.kind,
            attr,
        })
    }

    async fn create_directory_entry_plus_iterator(
        &self,
        read_dir: ReadDir,
    ) -> DirectoryEntryPlusIterator {
        #[allow(clippy::cast_possible_truncation)]
        let futures: Vec<_> = read_dir
            .into_iter()
            .map(|entry| {
                let fs = {
                    self.self_weak
                        .lock()
                        .unwrap()
                        .as_ref()
                        .unwrap()
                        .upgrade()
                        .unwrap()
                };
                DIR_ENTRIES_RT.spawn(async move { fs.create_directory_entry_plus(entry).await })
            })
            .collect();

        // do these futures in parallel and return them
        let mut res = VecDeque::with_capacity(futures.len());
        for f in futures {
            res.push_back(f.await.unwrap());
        }
        DirectoryEntryPlusIterator(res)
    }

    async fn create_directory_entry(
        &self,
        entry: io::Result<DirEntry>,
    ) -> FsResult<DirectoryEntry> {
        if entry.is_err() {
            return Err(entry.err().unwrap().into());
        }
        if let Err(e) = entry {
            error!(err = %e, "reading directory entry");
            return Err(e.into());
        }
        let entry = entry.unwrap();
        let name = entry.file_name().to_string_lossy().to_string();
        let name = {
            if name == "$." {
                SecretString::new(Box::new(".".into()))
            } else if name == "$.." {
                SecretString::from_str("..").unwrap()
            } else {
                // try from cache
                let lock = self.get_dir_entries_name_cache().await?;
                let mut cache = lock.lock().await;
                if let Some(name_cached) = cache.get(&name).cloned() {
                    name_cached
                } else {
                    drop(cache);
                    if let Ok(decrypted_name) =
                        crypto::decrypt_file_name(&name, self.cipher, &*self.key.get().await?)
                            .map_err(|err| {
                                error!(err = %err, "decrypting file name");
                                err
                            })
                    {
                        lock.lock().await.put(name.clone(), decrypted_name.clone());
                        decrypted_name
                    } else {
                        return Err(FsError::InvalidInput("invalid file name"));
                    }
                }
            }
        };

        self.validate_filename(&name)?;

        let file_path = entry.path().to_str().unwrap().to_owned();
        // try from cache
        let lock = self.dir_entries_meta_cache.get().await?;
        let mut cache = lock.lock().await;
        if let Some((ino, kind)) = cache.get(&file_path) {
            return Ok(DirectoryEntry {
                ino: *ino,
                name,
                kind: *kind,
            });
        }
        drop(cache);
        let lock = self
            .serialize_dir_entries_ls_locks
            .get_or_insert_with(file_path.clone(), || RwLock::new(false));
        let guard = lock.read().await;
        let file = File::open(entry.path())?;
        let res: bincode::Result<(u64, FileType)> = bincode::deserialize_from(crypto::create_read(
            file,
            self.cipher,
            &*self.key.get().await?,
        ));
        drop(guard);
        if let Err(e) = res {
            error!(err = %e, "deserializing directory entry");
            return Err(e.into());
        }
        let (ino, kind): (u64, FileType) = res.unwrap();
        // add to cache
        self.dir_entries_meta_cache
            .get()
            .await?
            .lock()
            .await
            .put(file_path, (ino, kind));
        Ok(DirectoryEntry { ino, name, kind })
    }

    async fn get_dir_entries_name_cache(
        &self,
    ) -> FsResult<Arc<Mutex<LruCache<String, SecretString>>>> {
        self.dir_entries_name_cache.get().await
    }

    async fn create_directory_entry_iterator(&self, read_dir: ReadDir) -> DirectoryEntryIterator {
        #[allow(clippy::cast_possible_truncation)]
        let futures: Vec<_> = read_dir
            .into_iter()
            .map(|entry| {
                let fs = {
                    self.self_weak
                        .lock()
                        .unwrap()
                        .as_ref()
                        .unwrap()
                        .upgrade()
                        .unwrap()
                };
                DIR_ENTRIES_RT.spawn(async move { fs.create_directory_entry(entry).await })
            })
            .collect();

        // do these futures in parallel and return them
        let mut res = VecDeque::with_capacity(futures.len());
        for f in futures {
            res.push_back(f.await.unwrap());
        }
        DirectoryEntryIterator(res)
    }

    #[allow(clippy::missing_errors_doc)]
    async fn get_inode_from_storage(&self, ino: u64) -> FsResult<FileAttr> {
        let lock = self
            .serialize_inode_locks
            .get_or_insert_with(ino, || RwLock::new(false));
        let _guard = lock.read();

        let path = self.ino_file(ino);
        if !path.is_file() {
            return Err(FsError::InodeNotFound);
        }
        let file = OpenOptions::new().read(true).open(path).map_err(|err| {
            error!(err = %err, "opening file");
            FsError::InodeNotFound
        })?;
        Ok(bincode::deserialize_from(crypto::create_read(
            file,
            self.cipher,
            &*self.key.get().await?,
        ))?)
    }

    async fn get_inode_from_cache_or_storage(&self, ino: u64) -> FsResult<FileAttr> {
        let lock = self.attr_cache.get().await?;
        let mut guard = lock.write().await;
        let attr = guard.get(&ino);
        if let Some(attr) = attr {
            Ok(*attr)
        } else {
            drop(guard);
            let attr = self.get_inode_from_storage(ino).await?;
            let mut guard = lock.write().await;
            guard.put(ino, attr);
            Ok(attr)
        }
    }

    /// Get metadata
    #[allow(clippy::missing_errors_doc)]
    pub async fn get_attr(&self, ino: u64) -> FsResult<FileAttr> {
        let mut attr = self.get_inode_from_cache_or_storage(ino).await?;

        // merge time info with any open read handles
        let open_reads = { self.opened_files_for_read.read().await.contains_key(&ino) };
        if open_reads {
            let fhs = self.opened_files_for_read.read().await.get(&ino).cloned();
            if let Some(fhs) = fhs {
                for fh in fhs {
                    let lock = self.read_handles.read().await;
                    if let Some(ctx) = lock.get(&fh) {
                        let set_atr: SetFileAttr = ctx.lock().await.attr.clone().into();
                        merge_attr(&mut attr, &set_atr, false);
                    }
                }
            }
        }

        // merge time info and size with any open write handles
        let open_writes = { self.opened_files_for_write.read().await.contains_key(&ino) };
        if open_writes {
            let fh = self.opened_files_for_write.read().await.get(&ino).copied();
            if let Some(fh) = fh {
                let lock = self.write_handles.read().await;
                if let Some(ctx) = lock.get(&fh) {
                    let ctx = ctx.lock().await;
                    merge_attr(&mut attr, &ctx.attr.clone().into(), false);
                }
            }
        }

        Ok(attr)
    }

    /// Set metadata
    pub async fn set_attr(&self, ino: u64, set_attr: SetFileAttr) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        self.set_attr2(ino, set_attr, false).await
    }

    async fn set_attr2(
        &self,
        ino: u64,
        set_attr: SetFileAttr,
        overwrite_size: bool,
    ) -> FsResult<()> {
        let serialize_update_lock = self
            .serialize_update_inode_locks
            .get_or_insert_with(ino, || Mutex::new(false));
        let _serialize_update_guard = serialize_update_lock.lock().await;

        let mut attr = self.get_attr(ino).await?;
        merge_attr(&mut attr, &set_attr, overwrite_size);
        let now = SystemTime::now();
        attr.ctime = now;
        attr.atime = now;

        self.write_inode_to_storage(&attr).await?;

        Ok(())
    }

    async fn write_inode_to_storage(&self, attr: &FileAttr) -> Result<(), FsError> {
        let lock = self
            .serialize_inode_locks
            .get_or_insert_with(attr.ino, || RwLock::new(false));
        let guard = lock.write().await;
        crypto::atomic_serialize_encrypt_into(
            &self.ino_file(attr.ino),
            attr,
            self.cipher,
            &*self.key.get().await?,
        )?;
        drop(guard);
        // update cache also
        {
            let lock = self.attr_cache.get().await?;
            let mut guard = lock.write().await;
            guard.put(attr.ino, *attr);
        }
        Ok(())
    }

    /// Read the contents from an `offset`.
    ///
    /// If we try to read outside of file size, we return zero bytes.
    /// If the file is not opened for read, it will return an error of type [FsError::InvalidFileHandle].
    #[instrument(skip(self, buf), fields(len = %buf.len()), ret(level = Level::DEBUG))]
    #[allow(clippy::missing_errors_doc)]
    #[allow(clippy::cast_possible_truncation)]
    pub async fn read(
        &self,
        ino: u64,
        offset: u64,
        buf: &mut [u8],
        handle: u64,
    ) -> FsResult<usize> {
        if !self.exists(ino) {
            return Err(FsError::InodeNotFound);
        }
        if !self.is_file(ino) {
            return Err(FsError::InvalidInodeType);
        }
        if !self.read_handles.read().await.contains_key(&handle) {
            return Err(FsError::InvalidFileHandle);
        }

        let _size = self.get_attr(ino).await?.size;

        let lock = self
            .read_write_locks
            .get_or_insert_with(ino, || RwLock::new(false));
        let _read_guard = lock.read().await;

        let guard = self.read_handles.read().await;
        let mut ctx = guard.get(&handle).unwrap().lock().await;

        if ctx.ino != ino {
            return Err(FsError::InvalidFileHandle);
        }
        if self.is_dir(ino) {
            return Err(FsError::InvalidInodeType);
        }
        if buf.is_empty() {
            // no-op
            return Ok(0);
        }

        // read data
        let (_buf, len) = {
            let reader = ctx.reader.as_mut().unwrap();

            reader.seek(SeekFrom::Start(offset)).map_err(|err| {
                error!(err = %err, "seeking");
                err
            })?;
            let pos = reader.stream_position().map_err(|err| {
                error!(err = %err, "getting position");
                err
            })?;
            if pos != offset {
                // we would need to seek after filesize
                return Ok(0);
            }
            // keep block size to max the cipher can handle
            #[allow(clippy::cast_possible_truncation)]
            let buf = if offset + buf.len() as u64 > self.cipher.max_plaintext_len() as u64 {
                warn!("reading more than max block size, truncating");
                buf.split_at_mut(self.cipher.max_plaintext_len() - offset as usize)
                    .0
            } else {
                buf
            };
            let len = stream_util::read(reader, buf).map_err(|err| {
                error!(err = %err, "reading");
                err
            })?;
            (buf, len)
        };

        ctx.attr.atime = SystemTime::now();
        drop(ctx);

        // self.sizes_read
        //     .lock()
        //     .await
        //     .get_mut(&ino)
        //     .unwrap()
        //     .fetch_add(len as u64, Ordering::SeqCst);
        // self.requested_read
        //     .lock()
        //     .await
        //     .get_mut(&ino)
        //     .unwrap()
        //     .fetch_add(buf.len() as u64, Ordering::SeqCst);

        // if buf.len() != len {
        //     error!(
        //         "size mismatch in read(), size {size} offset {offset} buf_len {} len {len}",
        //         buf.len()
        //     );
        //     let lock = self.write_handles.read().await;
        //     lock.iter().for_each(|(_, lock2)| {
        //         call_async(async {
        //             let ctx = lock2.lock().await;
        //             if ctx.ino == ino && size != ctx.attr.size {
        //                 error!("trying to read from a file which is not commited yet, ctx size {} actual size {size}", ctx.attr.size);
        //             }
        //         });
        //     });
        // }

        Ok(len)
    }

    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::too_many_lines)]
    pub async fn release(&self, handle: u64) -> FsResult<()> {
        if handle == 0 {
            // in the case of directory or if the file was crated
            // without being opened we don't use a handle
            return Ok(());
        }
        let mut valid_fh = false;

        // read
        let ctx = { self.read_handles.write().await.remove(&handle) };
        if let Some(ctx) = ctx {
            let ctx = ctx.lock().await;

            {
                let mut opened_files_for_read = self.opened_files_for_read.write().await;
                opened_files_for_read
                    .get_mut(&ctx.ino)
                    .expect("handle is missing")
                    .remove(&handle);
                if opened_files_for_read
                    .get(&ctx.ino)
                    .expect("handle is missing")
                    .is_empty()
                {
                    opened_files_for_read.remove(&ctx.ino);
                }
            }

            // write attr only here to avoid serializing it multiple times while reading
            // it will merge time fields with existing data because it might got change while we kept the handle
            let set_attr: SetFileAttr = ctx.attr.clone().into();
            let ino = ctx.ino;
            drop(ctx);
            self.set_attr(ino, set_attr).await?;

            valid_fh = true;
        }

        // write
        let ctx = { self.write_handles.write().await.remove(&handle) };
        if let Some(ctx) = ctx {
            if self.read_only {
                return Err(FsError::ReadOnly);
            }
            let mut ctx = ctx.lock().await;

            let mut writer = ctx.writer.take().unwrap();
            let lock = self
                .read_write_locks
                .get_or_insert_with(ctx.ino, || RwLock::new(false));
            let write_guard = lock.write().await;
            let file = writer.finish()?;
            file.sync_all()?;
            File::open(self.contents_path(ctx.ino).parent().unwrap())?.sync_all()?;
            // write attr only here to avoid serializing it multiple times while writing
            // it will merge time fields with existing data because it might got change while we kept the handle
            let ino = ctx.ino;
            let attr = ctx.attr.clone();
            drop(ctx);
            self.set_attr(ino, attr.into()).await?;
            let attr = self.get_attr(ino).await?;
            {
                let write_size = self
                    .sizes_write
                    .lock()
                    .await
                    .get(&ino)
                    .unwrap()
                    .load(Ordering::SeqCst);
                info!("written for {ino} {write_size}");
                if attr.size != write_size {
                    // error!("size mismatch write {} {}", write_size, attr.size);
                }
                let requested_read = self
                    .requested_read
                    .lock()
                    .await
                    .get(&ino)
                    .unwrap()
                    .load(Ordering::SeqCst);
                let read = self
                    .sizes_read
                    .lock()
                    .await
                    .get(&ino)
                    .unwrap()
                    .load(Ordering::SeqCst);
                if requested_read != read {
                    error!(
                        "size mismatch read, size {} requested {} read {}",
                        attr.size, requested_read, read
                    );
                }
            }
            self.sizes_write.lock().await.remove(&ino);
            self.sizes_read.lock().await.remove(&ino);
            self.requested_read.lock().await.remove(&ino);
            drop(write_guard);
            self.opened_files_for_write.write().await.remove(&ino);
            self.reset_handles(ino, Some(handle), true).await?;

            valid_fh = true;
        }

        if !valid_fh {
            return Err(FsError::InvalidFileHandle);
        }
        Ok(())
    }

    /// Check if a file is opened for reading with this handle.
    pub async fn is_read_handle(&self, fh: u64) -> bool {
        self.read_handles.read().await.contains_key(&fh)
    }

    /// Check if a file is opened for writing with this handle.
    pub async fn is_write_handle(&self, fh: u64) -> bool {
        self.write_handles.read().await.contains_key(&fh)
    }

    /// Writes the contents of `buf` to the file with `ino` starting at `offset`.
    ///
    /// If we write outside file size, we fill up with zeros until the `offset`.
    /// If the file is not opened for writing,
    /// it will return an error of type [FsError::InvalidFileHandle].
    #[instrument(skip(self, buf), fields(len = %buf.len()), ret(level = Level::DEBUG))]
    pub async fn write(&self, ino: u64, offset: u64, buf: &[u8], handle: u64) -> FsResult<usize> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if !self.exists(ino) {
            return Err(FsError::InodeNotFound);
        }
        if !self.is_file(ino) {
            return Err(FsError::InvalidInodeType);
        }
        {
            if !self.write_handles.read().await.contains_key(&handle) {
                return Err(FsError::InvalidFileHandle);
            }
        }
        {
            let guard = self.write_handles.read().await;
            let ctx = guard.get(&handle).unwrap().lock().await;
            if ctx.ino != ino {
                return Err(FsError::InvalidFileHandle);
            }
        }
        if buf.is_empty() {
            // no-op
            return Ok(0);
        }

        let lock = self
            .read_write_locks
            .get_or_insert_with(ino, || RwLock::new(false));
        let write_guard = lock.write().await;

        let guard = self.write_handles.read().await;
        let mut ctx = guard.get(&handle).unwrap().lock().await;

        // write new data
        let (pos, len) = {
            if offset > self.cipher.max_plaintext_len() as u64 {
                return Err(FsError::MaxFilesizeExceeded(
                    self.cipher.max_plaintext_len(),
                ));
            }
            let writer = ctx.writer.as_mut().unwrap();
            let pos = writer.seek(SeekFrom::Start(offset)).map_err(|err| {
                error!(err = %err, "seeking");
                err
            })?;
            if offset != pos {
                // we could not seek to the desired position
                return Ok(0);
            }
            // keep block size to max the cipher can handle
            #[allow(clippy::cast_possible_truncation)]
            let buf = if offset + buf.len() as u64 > self.cipher.max_plaintext_len() as u64 {
                warn!("writing more than max block size, truncating");
                &buf[..(self.cipher.max_plaintext_len() - offset as usize)]
            } else {
                buf
            };
            let len = writer.write(buf).map_err(|err| {
                error!(err = %err, "writing");
                err
            })?;
            (writer.stream_position()?, len)
        };

        // let size = ctx.attr.size;
        if pos > ctx.attr.size {
            // if we write pass file size set the new size
            debug!("setting new file size {}", pos);
            ctx.attr.size = pos;
        }
        let now = SystemTime::now();
        ctx.attr.mtime = now;
        ctx.attr.ctime = now;
        ctx.attr.atime = now;
        drop(ctx);

        drop(write_guard);
        self.reset_handles(ino, Some(handle), true).await?;

        self.sizes_write
            .lock()
            .await
            .get_mut(&ino)
            .unwrap()
            .fetch_add(len as u64, Ordering::SeqCst);
        if buf.len() != len {
            // error!(
            //     "size mismatch in write(), size {size} offset {offset} buf_len {} len {len}",
            //     buf.len()
            // );
        }
        // warn!(
        //     "written uncommited for {ino} size {}",
        //     self.sizes_write
        //         .lock()
        //         .await
        //         .get(&ino)
        //         .unwrap()
        //         .load(Ordering::SeqCst)
        // );

        Ok(len)
    }

    /// Flush the data to the underlying storage.
    #[allow(clippy::missing_panics_doc)]
    pub async fn flush(&self, handle: u64) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if handle == 0 {
            // in the case of directory or if the file was crated without being opened we don't use a handle
            return Ok(());
        }
        let lock = self.read_handles.read().await;
        let mut valid_fh = lock.get(&handle).is_some();
        let lock = self.write_handles.read().await;
        if let Some(ctx) = lock.get(&handle) {
            let mut ctx = ctx.lock().await;
            let lock = self
                .read_write_locks
                .get_or_insert_with(ctx.ino, || RwLock::new(false));
            let write_guard = lock.write().await;
            ctx.writer.as_mut().expect("writer is missing").flush()?;
            File::open(self.contents_path(ctx.ino))?.sync_all()?;
            File::open(self.contents_path(ctx.ino).parent().unwrap())?.sync_all()?;
            drop(write_guard);
            let ino = ctx.ino;
            drop(ctx);
            self.reset_handles(ino, Some(handle), true).await?;
            valid_fh = true;
        }

        if !valid_fh {
            return Err(FsError::InvalidFileHandle);
        }

        Ok(())
    }

    /// Helpful when we want to copy just some portions of the file.
    pub async fn copy_file_range(
        &self,
        file_range_req: &CopyFileRangeReq,
        size: usize,
    ) -> FsResult<usize> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if self.is_dir(file_range_req.src_ino) || self.is_dir(file_range_req.dest_ino) {
            return Err(FsError::InvalidInodeType);
        }

        let mut buf = vec![0; size];
        let len = self
            .read(
                file_range_req.src_ino,
                file_range_req.src_offset,
                &mut buf,
                file_range_req.src_fh,
            )
            .await?;
        if len == 0 {
            return Ok(0);
        }
        let mut copied = 0;
        while copied < size {
            let len = self
                .write(
                    file_range_req.dest_ino,
                    file_range_req.dest_offset,
                    &buf[copied..len],
                    file_range_req.dest_fh,
                )
                .await?;
            if len == 0 && copied < size {
                error!(len, "Failed to copy all read bytes");
                return Err(FsError::Other("Failed to copy all read bytes"));
            }
            copied += len;
        }
        Ok(len)
    }

    /// Open a file. We can open multiple times for read but only one to write at a time.
    #[allow(clippy::missing_panics_doc)]
    pub async fn open(&self, ino: u64, read: bool, write: bool) -> FsResult<u64> {
        if write && self.read_only {
            return Err(FsError::ReadOnly);
        }
        if !read && !write {
            return Err(FsError::InvalidInput(
                "read and write cannot be false at the same time",
            ));
        }
        if self.is_dir(ino) {
            return Err(FsError::InvalidInodeType);
        }

        let mut handle: Option<u64> = None;
        if read {
            handle = Some(self.next_handle());
            self.do_with_read_handle(
                *handle.as_ref().unwrap(),
                ReadHandleContextOperation::Create { ino },
            )
            .await?;
        }
        if write {
            if self.opened_files_for_write.read().await.contains_key(&ino) {
                return Err(FsError::AlreadyOpenForWrite);
            }
            if handle.is_none() {
                handle = Some(self.next_handle());
            }
            let res = self
                .do_with_write_handle(
                    *handle.as_ref().expect("handle is missing"),
                    WriteHandleContextOperation::Create { ino },
                )
                .await;
            if res.is_err() && read {
                // on error remove the read handle if it was added above,
                // remove the read handle if it was added above
                self.read_handles
                    .write()
                    .await
                    .remove(handle.as_ref().unwrap());
            }
            res?;
        }
        let fh = handle.unwrap();
        self.sizes_write
            .lock()
            .await
            .entry(ino)
            .or_insert(AtomicU64::new(0));
        self.sizes_read
            .lock()
            .await
            .entry(ino)
            .or_insert(AtomicU64::new(0));
        self.requested_read
            .lock()
            .await
            .entry(ino)
            .or_insert(AtomicU64::new(0));
        Ok(fh)
    }

    /// Truncates or extends the underlying file, updating the size of this file to become size.
    #[allow(clippy::missing_panics_doc)]
    #[allow(clippy::too_many_lines)]
    pub async fn set_len(&self, ino: u64, size: u64) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        info!("truncate {ino} to {size}");
        let attr = self.get_attr(ino).await?;
        if matches!(attr.kind, FileType::Directory) {
            return Err(FsError::InvalidInodeType);
        }

        if size == attr.size {
            // no-op
            return Ok(());
        }

        let lock = self
            .read_write_locks
            .get_or_insert_with(ino, || RwLock::new(false));
        let _write_guard = lock.write().await;

        // flush writers
        self.flush_and_reset_writers(ino).await?;

        let file_path = self.contents_path(ino);
        if size == 0 {
            debug!("truncate to zero");
            // truncate to zero
            let file = File::create(&file_path)?;
            file.set_len(0)?;
            file.sync_all()?;
        } else {
            debug!("truncate size to {}", size.to_formatted_string(&Locale::en));

            let mut file = fs_util::open_atomic_write(&file_path)?;
            {
                // have a new scope, so we drop the reader before moving new content files
                let mut reader = self.create_read(File::open(file_path.as_path())?).await?;

                let mut writer = self.create_write(file).await?;

                let len = if size > attr.size {
                    // increase size, copy existing data until existing size
                    attr.size
                } else {
                    // decrease size, copy existing data until new size
                    size
                };
                stream_util::copy_exact(&mut reader, &mut writer, len)?;
                if size > attr.size {
                    // increase size, seek to new size will write zeros
                    stream_util::fill_zeros(&mut writer, size - attr.size)?;
                }
                file = writer.finish()?;
            }
            file.commit()?;
        }
        File::open(file_path.parent().unwrap())?.sync_all()?;

        let now = SystemTime::now();
        let set_attr = SetFileAttr::default()
            .with_size(size)
            .with_mtime(now)
            .with_ctime(now)
            .with_atime(now);
        self.set_attr2(ino, set_attr, true).await?;

        let attr = self.get_inode_from_storage(ino).await?;
        println!("attr 1: {:?}", attr.size);
        let attr = self.get_attr(ino).await?;
        println!("attr 1: {:?}", attr.size);

        // reset handles because the file has changed
        self.reset_handles(attr.ino, None, false).await?;

        let attr = self.get_inode_from_storage(ino).await?;
        println!("attr 2: {:?}", attr.size);
        let attr = self.get_attr(ino).await?;
        println!("attr 2: {:?}", attr.size);

        if size != attr.size {
            error!("error truncating file expected {size} actual {}", attr.size);
        }

        Ok(())
    }

    /// This will write any dirty data to the file from all writers and reset them.
    /// Timestamps and size will be updated to the storage.
    /// > ⚠️ **Warning**
    /// > Need to be called in a context with write lock on `self.read_write_inode.lock().await.get(ino)`.
    /// > That is because we want to make sure caller is holding a lock while all writers flush and we can't
    /// > lock here also as we would end-up in a deadlock.
    async fn flush_and_reset_writers(&self, ino: u64) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        let opened_files_for_write_guard = self.opened_files_for_write.read().await;
        let handle = opened_files_for_write_guard.get(&ino);
        if let Some(handle) = handle {
            let write_handles_guard = self.write_handles.write().await;
            let ctx = write_handles_guard.get(handle);
            if let Some(lock) = ctx {
                let mut ctx = lock.lock().await;

                let mut writer = ctx.writer.take().unwrap();
                let file = writer.finish()?;
                file.sync_all()?;
                File::open(self.contents_path(ctx.ino).parent().unwrap())?.sync_all()?;
                let handle = *handle;
                let set_attr: SetFileAttr = ctx.attr.clone().into();
                drop(ctx);
                drop(opened_files_for_write_guard);
                drop(write_handles_guard);
                self.set_attr(ino, set_attr).await?;
                self.reset_handles(ino, Some(handle), true).await?;
                let write_handles_guard = self.write_handles.write().await;
                let mut ctx = write_handles_guard.get(&handle).unwrap().lock().await;
                let writer = self
                    .create_write_seek(
                        OpenOptions::new()
                            .read(true)
                            .write(true)
                            .open(self.contents_path(ino))?,
                    )
                    .await?;
                ctx.writer = Some(Box::new(writer));
                let attr = self.get_inode_from_storage(ino).await?;
                ctx.attr = attr.into();
            }
        }
        Ok(())
    }

    #[allow(clippy::missing_panics_doc)]
    pub async fn rename(
        &self,
        parent: u64,
        name: &SecretString,
        new_parent: u64,
        new_name: &SecretString,
    ) -> FsResult<()> {
        if self.read_only {
            return Err(FsError::ReadOnly);
        }
        if !self.exists(parent) {
            return Err(FsError::InodeNotFound);
        }
        if !self.is_dir(parent) {
            return Err(FsError::InvalidInodeType);
        }
        if !self.exists(new_parent) {
            return Err(FsError::InodeNotFound);
        }
        if !self.is_dir(new_parent) {
            return Err(FsError::InvalidInodeType);
        }
        if !self.exists_by_name(parent, name)? {
            return Err(FsError::NotFound("name not found"));
        }
        self.validate_filename(new_name)?;

        if parent == new_parent && name.expose_secret() == new_name.expose_secret() {
            // no-op
            return Ok(());
        }

        // Only overwrite an existing directory if it's empty
        if let Ok(Some(new_attr)) = self.find_by_name(new_parent, new_name).await {
            if new_attr.kind == FileType::Directory && self.len(new_attr.ino)? > 0 {
                return Err(FsError::NotEmpty);
            }
        }

        let attr = self
            .find_by_name(parent, name)
            .await?
            .ok_or(FsError::NotFound("name not found"))?;
        // remove from parent contents
        self.remove_directory_entry(parent, name).await?;
        // remove from new_parent contents, if exists
        if self.exists_by_name(new_parent, new_name)? {
            self.remove_directory_entry(new_parent, new_name).await?;
        }
        // add to new parent contents
        self.insert_directory_entry(
            new_parent,
            &DirectoryEntry {
                ino: attr.ino,
                name: new_name.clone(),
                kind: attr.kind,
            },
        )
        .await?;

        if attr.kind == FileType::Directory {
            // add the parent link to the new directory
            self.insert_directory_entry(
                attr.ino,
                &DirectoryEntry {
                    ino: new_parent,
                    name: SecretBox::new(Box::new("$..".to_owned())),
                    kind: FileType::Directory,
                },
            )
            .await?;
        }

        let now = SystemTime::now();
        let set_attr = SetFileAttr::default()
            .with_mtime(now)
            .with_ctime(now)
            .with_atime(now);
        self.set_attr(parent, set_attr).await?;

        let set_attr = SetFileAttr::default()
            .with_mtime(now)
            .with_ctime(now)
            .with_atime(now);
        self.set_attr(new_parent, set_attr).await?;

        let set_attr = SetFileAttr::default().with_ctime(now).with_atime(now);
        self.set_attr(attr.ino, set_attr).await?;

        Ok(())
    }

    /// Create a crypto writer using internal encryption info.
    pub async fn create_write<W: CryptoInnerWriter + Seek + Send + Sync + 'static>(
        &self,
        file: W,
    ) -> FsResult<impl CryptoWrite<W>> {
        Ok(crypto::create_write(
            file,
            self.cipher,
            &*self.key.get().await?,
        ))
    }

    /// Create a crypto writer with seek using internal encryption info.
    pub async fn create_write_seek<W: Write + Seek + Read + Send + Sync + 'static>(
        &self,
        file: W,
    ) -> FsResult<impl CryptoWriteSeek<W>> {
        Ok(crypto::create_write_seek(
            file,
            self.cipher,
            &*self.key.get().await?,
        ))
    }

    /// Create a crypto reader using internal encryption info.
    pub async fn create_read<R: Read + Send + Sync>(
        &self,
        reader: R,
    ) -> FsResult<impl CryptoRead<R>> {
        Ok(crypto::create_read(
            reader,
            self.cipher,
            &*self.key.get().await?,
        ))
    }

    /// Create a crypto reader with seek using internal encryption info.
    pub async fn create_read_seek<R: Read + Seek + Send + Sync>(
        &self,
        reader: R,
    ) -> FsResult<impl CryptoReadSeek<R>> {
        Ok(crypto::create_read_seek(
            reader,
            self.cipher,
            &*self.key.get().await?,
        ))
    }

    /// Change the password of the filesystem used to access the encryption key.
    pub async fn passwd(
        data_dir: &Path,
        old_password: SecretString,
        new_password: SecretString,
        cipher: Cipher,
    ) -> FsResult<()> {
        check_structure(data_dir, false).await?;
        // decrypt key
        let salt: Vec<u8> = bincode::deserialize_from(File::open(
            data_dir.join(SECURITY_DIR).join(KEY_SALT_FILENAME),
        )?)?;
        let initial_key = crypto::derive_key(&old_password, cipher, &salt)?;
        let enc_file = data_dir.join(SECURITY_DIR).join(KEY_ENC_FILENAME);
        let reader = crypto::create_read(File::open(enc_file)?, cipher, &initial_key);
        let key: Vec<u8> =
            bincode::deserialize_from(reader).map_err(|_| FsError::InvalidPassword)?;
        let key = SecretBox::new(Box::new(key));
        // encrypt it with a new key derived from new password
        let new_key = crypto::derive_key(&new_password, cipher, &salt)?;
        crypto::atomic_serialize_encrypt_into(
            &data_dir.join(SECURITY_DIR).join(KEY_ENC_FILENAME),
            &*key.expose_secret(),
            cipher,
            &new_key,
        )?;
        Ok(())
    }

    fn next_handle(&self) -> u64 {
        self.current_handle
            .fetch_add(1, std::sync::atomic::Ordering::SeqCst)
    }

    /// Reset all handles for a file.
    /// Read handles will be recreated.
    /// Write handles will be flushed and recreated.
    /// Timestamps and size will be updated to storage.
    /// > ⚠️ **Warning**
    /// > Need to be called in a context with write lock on `self.read_write_inode.lock().await.get(ino)`.
    /// > That is because we want to make sure caller is holding a lock while all writers flush, and we can't
    /// > lock here also as we would end-up in a deadlock.
    async fn reset_handles(
        &self,
        ino: u64,
        skip_write_fh: Option<u64>,
        save_attr: bool,
    ) -> FsResult<()> {
        let path = self.contents_path(ino);

        // read
        let lock = self.opened_files_for_read.read().await;
        if let Some(set) = lock.get(&ino) {
            for handle in set.iter().filter(|h| skip_write_fh != Some(**h)) {
                let guard = self.read_handles.read().await;
                let ctx = guard.get(handle).unwrap().lock().await;
                let set_attr: SetFileAttr = ctx.attr.clone().into();
                drop(ctx);
                self.set_attr(ino, set_attr).await?;
                let attr = self.get_inode_from_storage(ino).await?;
                let mut ctx = guard.get(handle).unwrap().lock().await;
                let reader = self.create_read_seek(File::open(&path)?).await?;
                ctx.reader = Some(Box::new(reader));
                ctx.attr = attr.into();
            }
        }

        // write
        let lock = self.opened_files_for_write.read().await;
        if let Some(fh) = lock.get(&ino) {
            if let Some(handle) = skip_write_fh {
                if *fh == handle {
                    return Ok(());
                }
            }
            let lock = self.write_handles.read().await;
            if let Some(lock) = lock.get(fh) {
                let mut ctx = lock.lock().await;
                let writer = ctx.writer.as_mut().unwrap();
                let file = writer.finish()?;
                file.sync_all()?;
                File::open(self.contents_path(ctx.ino).parent().unwrap())?.sync_all()?;
                let set_attr: Option<SetFileAttr> = if save_attr {
                    Some(ctx.attr.clone().into())
                } else {
                    None
                };
                drop(ctx);
                if let Some(set_attr) = set_attr {
                    self.set_attr(ino, set_attr).await?;
                }
                let writer = self
                    .create_write_seek(OpenOptions::new().read(true).write(true).open(&path)?)
                    .await?;
                let mut ctx = lock.lock().await;
                ctx.writer = Some(Box::new(writer));
                let attr = self.get_inode_from_storage(ino).await?;
                ctx.attr = attr.into();
            }
        }

        Ok(())
    }

    async fn do_with_read_handle(
        &self,
        handle: u64,
        op: ReadHandleContextOperation,
    ) -> FsResult<()> {
        let ino = op.get_ino();
        let path = self.contents_path(ino);
        let attr = self.get_inode_from_storage(ino).await?;
        match op {
            ReadHandleContextOperation::Create { ino } => {
                let attr: TimesFileAttr = attr.into();
                let reader = self.create_read_seek(File::open(&path)?).await?;
                let ctx = ReadHandleContext {
                    ino,
                    attr,
                    reader: Some(Box::new(reader)),
                };
                self.read_handles
                    .write()
                    .await
                    .insert(handle, Mutex::new(ctx));
                self.opened_files_for_read
                    .write()
                    .await
                    .entry(ino)
                    .or_insert_with(HashSet::new)
                    .insert(handle);
            }
        }
        Ok(())
    }

    async fn do_with_write_handle(
        &self,
        handle: u64,
        op: WriteHandleContextOperation,
    ) -> FsResult<()> {
        let ino = op.get_ino();
        let path = self.contents_path(ino);
        match op {
            WriteHandleContextOperation::Create { ino } => {
                let attr = self.get_attr(ino).await?.into();
                let writer = self
                    .create_write_seek(OpenOptions::new().read(true).write(true).open(&path)?)
                    .await?;
                let ctx = WriteHandleContext {
                    ino,
                    attr,
                    writer: Some(Box::new(writer)),
                };
                self.write_handles
                    .write()
                    .await
                    .insert(handle, Mutex::new(ctx));
                self.opened_files_for_write
                    .write()
                    .await
                    .insert(ino, handle);
            }
        }

        Ok(())
    }

    async fn ensure_root_exists(&self) -> FsResult<()> {
        if !self.exists(ROOT_INODE) {
            let mut attr: FileAttr = CreateFileAttr {
                kind: FileType::Directory,
                perm: 0o755,
                uid: 0,
                gid: 0,
                rdev: 0,
                flags: 0,
            }
            .into();
            attr.ino = ROOT_INODE;
            #[cfg(any(target_os = "linux", target_os = "macos"))]
            unsafe {
                attr.uid = libc::getuid();
                attr.gid = libc::getgid();
            }

            self.write_inode_to_storage(&attr).await?;

            // create in contents directory
            fs::create_dir(self.contents_path(attr.ino))?;
            fs::create_dir(self.contents_path(attr.ino).join(LS_DIR))?;
            fs::create_dir(self.contents_path(attr.ino).join(HASH_DIR))?;

            // add "." entry
            self.insert_directory_entry(
                attr.ino,
                &DirectoryEntry {
                    ino: attr.ino,
                    name: SecretString::from_str("$.").unwrap(),
                    kind: FileType::Directory,
                },
            )
            .await?;
        }

        Ok(())
    }

    async fn insert_directory_entry(
        &self,
        ino_contents_dir: u64,
        entry: &DirectoryEntry,
    ) -> FsResult<()> {
        let parent_path = self.contents_path(ino_contents_dir);
        let encrypted_name =
            crypto::encrypt_file_name(&entry.name, self.cipher, &*self.key.get().await?)?;
        // add to LS directory
        let self_clone = self
            .self_weak
            .lock()
            .unwrap()
            .as_ref()
            .unwrap()
            .upgrade()
            .unwrap();
        let parent_path_clone = parent_path.clone();
        let encrypted_name_clone = encrypted_name.clone();
        let entry_clone = entry.clone();
        // spawn a task to do concurrently with adding to HASH directory
        let h = tokio::spawn(async move {
            let file_path = parent_path_clone
                .join(LS_DIR)
                .join(encrypted_name_clone.clone());
            let lock = self_clone
                .serialize_dir_entries_ls_locks
                .get_or_insert_with(file_path.to_str().unwrap().to_owned(), || {
                    RwLock::new(false)
                });
            let _guard = lock.write().await;
            // write inode and file type
            let entry = (entry_clone.ino, entry_clone.kind);
            crypto::atomic_serialize_encrypt_into(
                &file_path,
                &entry,
                self_clone.cipher,
                &*self_clone.key.get().await?,
            )?;
            Ok::<(), FsError>(())
        });
        // add to HASH directory
        let self_clone = self
            .self_weak
            .lock()
            .unwrap()
            .as_ref()
            .unwrap()
            .upgrade()
            .unwrap();
        let entry_hash = entry.clone();
        tokio::spawn(async move {
            let name = crypto::hash_file_name(&entry_hash.name);
            let file_path = parent_path.join(HASH_DIR).join(name);
            let lock = self_clone
                .serialize_dir_entries_hash_locks
                .get_or_insert_with(file_path.to_str().unwrap().to_owned(), || {
                    RwLock::new(false)
                });
            let _guard = lock.write().await;
            // write inode and file type
            // we save the encrypted name also because we need it to remove the entry on [`remove_directory_entry`]
            let entry = (entry_hash.ino, entry_hash.kind, encrypted_name);
            crypto::atomic_serialize_encrypt_into(
                &file_path,
                &entry,
                self_clone.cipher,
                &*self_clone.key.get().await?,
            )?;
            Ok::<(), FsError>(())
        })
        .await??;
        h.await??;
        Ok(())
    }

    fn ino_file(&self, ino: u64) -> PathBuf {
        self.data_dir.join(INODES_DIR).join(ino.to_string())
    }

    fn contents_path(&self, ino: u64) -> PathBuf {
        self.data_dir.join(CONTENTS_DIR).join(ino.to_string())
    }

    async fn remove_directory_entry(&self, parent: u64, name: &SecretString) -> FsResult<()> {
        let parent_path = self.contents_path(parent);
        // remove from HASH
        let name = crypto::hash_file_name(name);
        let path = parent_path.join(HASH_DIR).join(name);
        let lock = self
            .serialize_dir_entries_hash_locks
            .get_or_insert_with(path.to_str().unwrap().to_owned(), || RwLock::new(false));
        let guard = lock.write().await;
        let (_, _, name): (u64, FileType, String) =
            bincode::deserialize_from(crypto::create_read(
                File::open(path.clone())?,
                self.cipher,
                &*self.key.get().await?,
            ))?;
        fs::remove_file(path)?;
        drop(guard);
        // remove from LS
        let path = parent_path.join(LS_DIR).join(name);
        let lock = self
            .serialize_dir_entries_ls_locks
            .get_or_insert_with(path.to_str().unwrap().to_owned(), || RwLock::new(false));
        let _guard = lock.write().await;
        fs::remove_file(path)?;
        Ok(())
    }

    fn generate_next_inode(&self) -> u64 {
        loop {
            let ino = crypto::create_rng().next_u64();

            if ino <= ROOT_INODE {
                continue;
            }
            if self.exists(ino) {
                continue;
            }

            return ino;
        }
    }
}
pub struct CopyFileRangeReq {
    src_ino: u64,
    src_offset: u64,
    dest_ino: u64,
    dest_offset: u64,
    src_fh: u64,
    dest_fh: u64,
}

#[bon]
impl CopyFileRangeReq {
    #[builder]
    pub fn new(
        src_ino: u64,
        src_offset: u64,
        dest_ino: u64,
        dest_offset: u64,
        src_fh: u64,
        dest_fh: u64,
    ) -> Self {
        Self {
            src_ino,
            src_offset,
            dest_ino,
            dest_offset,
            src_fh,
            dest_fh,
        }
    }
}

fn read_or_create_key(
    key_path: &PathBuf,
    salt_path: &PathBuf,
    password: &SecretString,
    cipher: Cipher,
) -> FsResult<SecretVec<u8>> {
    let salt = if salt_path.exists() {
        bincode::deserialize_from(File::open(salt_path)?).map_err(|_| FsError::InvalidPassword)?
    } else {
        let mut salt = vec![0; 16];
        crypto::create_rng().fill_bytes(&mut salt);
        let mut file = OpenOptions::new()
            .read(true)
            .write(true)
            .create(true)
            .truncate(true)
            .open(salt_path)?;
        bincode::serialize_into(&mut file, &salt)?;
        file.flush()?;
        file.sync_all()?;
        File::open(salt_path.parent().expect("oops, we don't have a parent"))?.sync_all()?;
        salt
    };
    // derive key from password
    let derived_key = crypto::derive_key(password, cipher, &salt)?;
    if key_path.exists() {
        // read key
        let reader = crypto::create_read(File::open(key_path)?, cipher, &derived_key);
        let key: Vec<u8> =
            bincode::deserialize_from(reader).map_err(|_| FsError::InvalidPassword)?;
        Ok(SecretBox::new(Box::new(key)))
    } else {
        // first time, create a random key and encrypt it with the derived key from password
        let mut key: Vec<u8> = vec![];
        let key_len = cipher.key_len();
        key.resize(key_len, 0);
        crypto::create_rng().fill_bytes(&mut key);
        let mut writer = crypto::create_write(
            OpenOptions::new()
                .read(true)
                .write(true)
                .create(true)
                .truncate(true)
                .open(key_path)?,
            cipher,
            &derived_key,
        );
        bincode::serialize_into(&mut writer, &key)?;
        let file = writer.finish()?;
        file.sync_all()?;
        File::open(key_path.parent().unwrap())?.sync_all()?;
        Ok(SecretBox::new(Box::new(key)))
    }
}

async fn ensure_structure_created(data_dir: &PathBuf) -> FsResult<()> {
    if data_dir.exists() {
        check_structure(data_dir, true).await?;
    } else {
        fs::create_dir_all(data_dir)?;
    }

    // create directories
    let dirs = vec![INODES_DIR, CONTENTS_DIR, SECURITY_DIR];
    for dir in dirs {
        let path = data_dir.join(dir);
        if !path.exists() {
            fs::create_dir_all(path)?;
        }
    }

    Ok(())
}

async fn check_structure(data_dir: &Path, ignore_empty: bool) -> FsResult<()> {
    if !data_dir.exists() || !data_dir.is_dir() {
        return Err(FsError::InvalidDataDirStructure);
    }
    let mut vec = ReadDirStream::new(tokio::fs::read_dir(data_dir).await?)
        .try_collect::<Vec<_>>()
        .await?
        .iter()
        .map(|dir| dir.file_name().to_string_lossy().to_string())
        .collect::<Vec<String>>();
    if vec.is_empty() && ignore_empty {
        return Ok(());
    }
    if vec.len() != 3 {
        return Err(FsError::InvalidDataDirStructure);
    }
    // make sure existing structure is ok
    vec.sort_unstable();
    let mut vec2 = vec![INODES_DIR, CONTENTS_DIR, SECURITY_DIR];
    vec2.sort_unstable();
    if vec != vec2
        || !data_dir.join(SECURITY_DIR).join(KEY_ENC_FILENAME).is_file()
        || !data_dir
            .join(SECURITY_DIR)
            .join(KEY_SALT_FILENAME)
            .is_file()
    {
        return Err(FsError::InvalidDataDirStructure);
    }

    Ok(())
}

fn merge_attr(attr: &mut FileAttr, set_attr: &SetFileAttr, overwrite_size: bool) {
    if let Some(size) = set_attr.size {
        if overwrite_size {
            attr.size = size;
        } else {
            attr.size = attr.size.max(size);
        }
    }
    if let Some(atime) = set_attr.atime {
        attr.atime = attr.atime.max(atime);
    }
    if let Some(mtime) = set_attr.mtime {
        attr.mtime = attr.mtime.max(mtime);
    }
    if let Some(ctime) = set_attr.ctime {
        attr.ctime = attr.ctime.max(ctime);
    }
    if let Some(crtime) = set_attr.crtime {
        attr.crtime = attr.crtime.max(crtime);
    }
    if let Some(perm) = set_attr.perm {
        attr.perm = perm;
    }
    if let Some(uid) = set_attr.uid {
        attr.uid = uid;
    }
    if let Some(gid) = set_attr.gid {
        attr.gid = gid;
    }
    if let Some(flags) = set_attr.flags {
        attr.flags = flags;
    }
}

pub async fn write_all_string_to_fs(
    fs: &EncryptedFs,
    ino: u64,
    offset: u64,
    s: &str,
    fh: u64,
) -> FsResult<()> {
    write_all_bytes_to_fs(fs, ino, offset, s.as_bytes(), fh).await
}

#[allow(clippy::missing_panics_doc)]
pub async fn write_all_bytes_to_fs(
    fs: &EncryptedFs,
    ino: u64,
    offset: u64,
    buf: &[u8],
    fh: u64,
) -> FsResult<()> {
    let mut pos = 0_usize;
    loop {
        let len = fs.write(ino, offset, &buf[pos..], fh).await?;
        pos += len;
        if pos == buf.len() {
            break;
        } else if len == 0 {
            return Err(FsError::Other("Failed to write all bytes"));
        }
    }
    fs.flush(fh).await?;
    Ok(())
}