use crate::disk::inode::InodeMode;
use crate::utils::permissions::get_groups;
use crate::utils::permissions::{check_access, clear_suid_sgid};
use crate::utils::{from_systime, time_now, to_fileattr, to_filetype};
use crate::{AyaFS, TTL};
use fuser::TimeOrNow::{Now, SpecificTime};
use fuser::{
    Filesystem, KernelConfig, ReplyAttr, ReplyData, ReplyDirectory, ReplyEmpty, ReplyEntry,
    ReplyLseek, ReplyOpen, ReplyWrite, Request, TimeOrNow,
};
use libc::{c_int, EACCES, EBADF, EEXIST, EINVAL, EIO, EISDIR, ENAMETOOLONG, ENOENT, ENOSPC, ENOSYS, ENOTDIR, ENOTEMPTY, EPERM, O_ACCMODE, O_RDONLY, O_RDWR, O_WRONLY, R_OK, S_ISGID, S_ISUID, S_IXGRP, S_IXOTH, S_IXUSR, W_OK};
use log::debug;
use std::ffi::OsStr;
use std::time::SystemTime;
use crate::block_device::BLOCK_SIZE;
use crate::disk::block::DataBlock;

impl AyaFS {}

impl Filesystem for AyaFS {
    fn init(&mut self, _req: &Request<'_>, _config: &mut KernelConfig) -> Result<(), c_int> {
        debug!("`init()");
        Ok(())
    }

    fn destroy(&mut self) {
        debug!("destroy()");
        // TODO 写回
    }

    fn lookup(&mut self, req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEntry) {
        if name.len() > 255 {
            reply.error(ENAMETOOLONG);
            return;
        }

        let parent = parent as usize;
        if let Some(parent_inode) = self.get_inode(parent) {
            if check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                R_OK,
            ) {
                let parent_inode = parent_inode.clone();
                match self.lookup_name(parent, &parent_inode, name) {
                    Ok((inode_index, _, inode)) => {
                        let attr = to_fileattr(inode_index as usize, &inode);
                        reply.entry(&TTL, &attr, 0);
                    }
                    Err(err_code) => reply.error(err_code),
                };
            } else {
                reply.error(EACCES);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn getattr(&mut self, _req: &Request<'_>, ino: u64, reply: ReplyAttr) {
        if let Some(inode) = self.get_inode(ino as usize) {
            reply.attr(&TTL, &to_fileattr(ino as usize, inode));
        } else {
            reply.error(ENOENT);
        }
    }

    fn setattr(
        &mut self,
        req: &Request<'_>,
        ino: u64,
        mode: Option<u32>,
        uid: Option<u32>,
        gid: Option<u32>,
        size: Option<u64>, // TODO 当 setattr 被 ftruncate invoke 时会设置 size
        atime: Option<TimeOrNow>,
        mtime: Option<TimeOrNow>,
        _ctime: Option<SystemTime>,
        fh: Option<u64>, // TODO 当 setattr 被 ftruncate invoke 时会提供 fh
        _crtime: Option<SystemTime>, // 忽略
        _chgtime: Option<SystemTime>, // 忽略
        _bkuptime: Option<SystemTime>, // 忽略
        _flags: Option<u32>, // 忽略
        reply: ReplyAttr,
    ) {
        if let Some(inode) = self.get_inode_mut(ino as usize) {
            // chmod
            if let Some(mode) = mode {
                debug!("chmod on inode {:#x?} mode {:o}", ino, mode);
                if req.uid() != 0 && req.uid() != inode.uid {
                    reply.error(EPERM);
                    return;
                } // uid == 0 (root) or uid == inode.uid (user itself)

                if req.uid() != 0
                    && req.gid() != inode.gid
                    && !get_groups(req.pid()).contains(&inode.gid)
                {
                    inode.mode = InodeMode((mode & !S_ISGID) as u16);
                } else {
                    inode.mode = InodeMode(mode as u16);
                }

                inode.ctime = time_now();
                reply.attr(&TTL, &to_fileattr(ino as usize, inode));
                return;
            }

            // chown
            if uid.is_some() || gid.is_some() {
                debug!("chown on inode {:#x?} uid {:?} gid {:?}", ino, uid, gid);
                if let Some(uid) = uid {
                    // 虽然只有 root 可以 chown 但是 user chown 自己也是不报错的
                    if req.uid() != 0 && !(uid == inode.uid && uid == req.uid()) {
                        reply.error(EPERM);
                        return;
                    }
                }
                if let Some(gid) = gid {
                    // 只有 root 和 file owner 才可以 chgrp
                    if req.uid() != 0 && req.uid() != inode.uid {
                        reply.error(EPERM);
                        return;
                    }
                    // root 可以任意 chgrp, 非 root 只能修改到用户自己所在的组里
                    if req.gid() != 0 && !get_groups(req.pid()).contains(&gid) {
                        reply.error(EPERM);
                        return;
                    }
                }

                // 可执行文件要清除 suid & sgid
                if inode.mode.0 & (S_IXUSR | S_IXGRP | S_IXOTH) as u16 != 0 {
                    inode.mode = clear_suid_sgid(inode.mode);
                }

                // chown 要清除 suid
                if let Some(uid) = uid {
                    inode.uid = uid;
                    inode.mode.0 &= !S_ISUID as u16;
                }

                if let Some(gid) = gid {
                    inode.gid = gid;
                    if req.uid() != 0 {
                        inode.mode.0 &= !S_ISGID as u16;
                    }
                }
                inode.ctime = time_now();
                reply.attr(&TTL, &to_fileattr(ino as usize, inode));
                return;
            }

            // ftruncate
            if let Some(size) = size {
                debug!("ftruncate on inode {:#x?} size {:?}", ino, size);
                if let Some(file_handle) = fh {
                    // 有 file handle 的
                    todo!()
                } else {
                    // 没有 file handle 基于 inode 的
                    todo!()
                }
            }

            // time 相关
            if atime.is_some() || mtime.is_some() {
                let current_time = time_now();
                if let Some(atime) = atime {
                    debug!("utimensat on inode {:#x?}, atime {:?}", ino, atime);
                    // root 和 user 可以随意修改 atime, 其他用户只能 touch (即 atime == Now)
                    if req.uid() != 0 && req.uid() != inode.uid && atime != Now {
                        reply.error(EPERM);
                        return;
                    }

                    if req.uid() != 0
                        && req.uid() != inode.uid
                        && check_access(
                            req.uid(),
                            req.gid(),
                            inode.uid,
                            inode.gid,
                            inode.mode,
                            R_OK, // atime 来说是 read TODO 对吗
                        )
                    {
                        reply.error(EACCES);
                        return;
                    }

                    inode.atime = match atime {
                        SpecificTime(time) => from_systime(time),
                        Now => current_time,
                    };
                    inode.ctime = current_time;
                }
                if let Some(mtime) = mtime {
                    debug!("utimensat on inode {:#x?}, mtime {:?}", ino, mtime);
                    // root 和 user 可以随意修改 mtime, 其他用户只能 mtime == Now
                    if req.uid() != 0 && req.uid() != inode.uid && mtime != Now {
                        reply.error(EPERM);
                        return;
                    }

                    if req.uid() != 0
                        && req.uid() != inode.uid
                        && check_access(
                            req.uid(),
                            req.gid(),
                            inode.uid,
                            inode.gid,
                            inode.mode,
                            W_OK, // mtime 来说是 write
                        )
                    {
                        reply.error(EACCES);
                        return;
                    }

                    inode.mtime = match mtime {
                        SpecificTime(time) => from_systime(time),
                        Now => current_time,
                    };
                    inode.ctime = current_time;
                }
            }
            reply.attr(&TTL, &to_fileattr(ino as usize, inode));
            return;
        } else {
            reply.error(ENOENT);
        }
    }

    fn readlink(&mut self, _req: &Request<'_>, ino: u64, reply: ReplyData) {
        debug!("[Not Implemented] readlink(ino: {})", ino);
        reply.error(ENOSYS);
    }

    fn mknod(
        &mut self,
        req: &Request<'_>,
        parent: u64,
        name: &OsStr,
        mode: u32,
        _umask: u32, // umask 是用不到的
        _rdev: u32,  // the device number (only valid if created file is a device)
        reply: ReplyEntry,
    ) {
        debug!(
            "Filesystem::mknod(parent: {}, name: {:?}, mode: {}, umask: {})",
            parent, name, mode, _umask
        );

        if let Some(parent_inode) = self.get_inode(parent as usize) {
            if !check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                W_OK,
            ) {
                reply.error(EACCES);
                return;
            }

            // parent 不是 IFDIR -> Not a directory
            if !parent_inode.is_dir() {
                reply.error(ENOTDIR);
                return;
            }

            // 文件名长度超过 255, 返回 filename too long
            if name.len() > 255 {
                reply.error(ENAMETOOLONG);
                return;
            }

            let mut parent_inode = parent_inode.clone();
            // 如果已经存在, 返回 already exists
            if self
                .lookup_name(parent as usize, &parent_inode, name)
                .is_ok()
            {
                reply.error(EEXIST);
                return;
            }

            let mode = mode as u16;
            if let Some((child_inode_index, child_inode)) =
                self.create_file(mode, req.uid(), req.gid(), 0)
            {
                let child_inode = child_inode.clone();
                let file_attr = to_fileattr(child_inode_index, &child_inode);
                if let Err(err_code) = self.add_direntry(
                    parent as usize,
                    &mut parent_inode,
                    child_inode_index,
                    name,
                    child_inode.mode.into(),
                ) {
                    reply.error(err_code);
                    return;
                }
                self.update_inode(parent as usize, parent_inode); // 前面 clone 了, 这里写回
                reply.entry(&TTL, &file_attr, 0);
            } else {
                // create_inode 失败 -> no enough space
                reply.error(ENOSPC);
            }
        } else {
            // parent 不存在 -> No such file or directory
            reply.error(ENOENT);
        }
    }

    fn mkdir(
        &mut self,
        req: &Request<'_>,
        parent: u64,
        name: &OsStr,
        mode: u32,
        _umask: u32, // umask 应该也是用不到的
        reply: ReplyEntry,
    ) {
        if let Some(parent_inode) = self.get_inode(parent as usize) {
            // 无权限创建 -> EACCES
            if !check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                W_OK,
            ) {
                reply.error(EACCES);
                return;
            }

            // parent 不是 IFDIR -> Not a directory
            if !parent_inode.is_dir() {
                reply.error(ENOTDIR);
                return;
            }

            // 文件名长度超过 255 -> filename too long
            if name.len() > 255 {
                reply.error(ENAMETOOLONG);
                return;
            }

            let mut parent_inode = parent_inode.clone();
            // 已经存在 -> File exists
            if self
                .lookup_name(parent as usize, &parent_inode, name)
                .is_ok()
            {
                reply.error(EEXIST);
                return;
            }

            let mode = mode as u16;
            if let Some((child_inode_index, child_inode)) =
                self.create_directory(mode, req.uid(), req.gid(), 0, Some(parent as usize))
            {
                let child_inode = child_inode.clone();
                let file_attr = to_fileattr(child_inode_index, &child_inode);
                if let Err(err_code) = self.add_direntry(
                    parent as usize,
                    &mut parent_inode,
                    child_inode_index,
                    name,
                    child_inode.mode.into(),
                ) {
                    reply.error(err_code);
                    return;
                }
                self.update_inode(parent as usize, parent_inode); // 前面 clone 了, 这里写回
                reply.entry(&TTL, &file_attr, 0);
            } else {
                // create_inode 失败 -> no enough space
                reply.error(ENOSPC);
            }
        } else {
            // parent 不存在 -> No such file or directory
            reply.error(ENOENT);
        }
    }

    fn unlink(&mut self, req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEmpty) {
        debug!("unlink(parent: {:#x?}, name: {:?})", parent, name,);
        if let Some(parent_inode) = self.get_inode(parent as usize) {
            // 无权限删除 -> EACCES
            if !check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                W_OK,
            ) {
                reply.error(EACCES);
                return;
            }

            // parent 不是 dir -> ENOTDIR
            if !parent_inode.is_dir() {
                reply.error(ENOTDIR);
                return;
            }

            // 文件名长度超过 255 -> filename too long
            if name.len() > 255 {
                reply.error(ENAMETOOLONG);
                return;
            }

            let mut parent_inode = parent_inode.clone();
            // 不存在 -> No such file or directory
            if let Ok((inode_index, entry_index, mut inode)) =
                self.lookup_name(parent as usize, &parent_inode, name)
            {
                let inode_index = inode_index as usize;
                // 要删除的 entry 是目录, 不能用 unlink
                if inode.is_dir() {
                    reply.error(EISDIR);
                    return;
                }

                inode.n_links -= 1;
                if inode.n_links == 0 {
                    // n_links == 0 -> 整个 inode 都要删除掉
                    match self.remove_file(inode_index) {
                        Ok(flag) => debug!("  unlink {}", flag),
                        Err(err_code) => {
                            reply.error(err_code);
                            return;
                        }
                    }
                } else {
                    // n_links > 0 -> 只是移除了一个 hard link, 将改动写回
                    self.update_inode(inode_index, inode);
                }

                // 删除 dir entry
                if let Err(err_code) =
                    self.remove_direntry(parent as usize, &mut parent_inode, name, entry_index)
                {
                    reply.error(err_code);
                    return;
                }
                reply.ok();
            } else {
                reply.error(ENOENT);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn rmdir(&mut self, req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEmpty) {
        debug!("rmdir(parent: {:#x?}, name: {:?}", parent, name,);
        if let Some(parent_inode) = self.get_inode(parent as usize) {
            // 无权限删除 -> EACCES
            if !check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                W_OK,
            ) {
                reply.error(EACCES);
                return;
            }

            // parent 不是 dir -> ENOTDIR
            if !parent_inode.is_dir() {
                reply.error(ENOTDIR);
                return;
            }

            // 文件名长度超过 255 -> filename too long
            if name.len() > 255 {
                reply.error(ENAMETOOLONG);
                return;
            }

            let mut parent_inode = parent_inode.clone();
            // 不存在 -> No such file or directory
            if let Ok((inode_index, entry_index, inode)) =
                self.lookup_name(parent as usize, &parent_inode, name)
            {
                let inode_index = inode_index as usize;
                // 要删除的 entry 是一般文件, 不用 rmdir
                if inode.is_file() {
                    reply.error(ENOTDIR);
                    return;
                }

                // 一定有 . 和 .. 所以 size == 2 就是空目录
                // 目录非空 -> ENOTEMPTY
                if inode.size > 2 {
                    reply.error(ENOTEMPTY);
                    return;
                }

                // directory 没有 hard link, 删了就是删了
                match self.remove_dir(inode_index) {
                    Ok(flag) => debug!("  rmdir {}", flag),
                    Err(err_code) => {
                        reply.error(err_code);
                        return;
                    }
                }

                // 删除 dir entry
                if let Err(err_code) =
                    self.remove_direntry(parent as usize, &mut parent_inode, name, entry_index)
                {
                    reply.error(err_code);
                    return;
                }

                reply.ok();
            } else {
                reply.error(ENOENT);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn open(&mut self, req: &Request<'_>, ino: u64, flags: i32, reply: ReplyOpen) {
        debug!("open(ino: {:#x?}, flags: {:#x?})", ino, flags);
        let (access_mask, read, write) = match flags & O_ACCMODE {
            O_RDONLY => {
                // Behavior is undefined, but most filesystems return EACCES
                if flags & libc::O_TRUNC != 0 {
                    reply.error(libc::EACCES);
                    return;
                }
                (R_OK, true, false)
            }
            O_WRONLY => (W_OK, false, true),
            O_RDWR => (R_OK | W_OK, true, true),
            _ => {
                // flag 非法
                reply.error(EINVAL);
                return;
            }
        };

        match self.get_inode(ino as usize) {
            Some(inode) => {
                if !check_access(
                    req.uid(),
                    req.gid(),
                    inode.uid,
                    inode.gid,
                    inode.mode,
                    access_mask,
                ) {
                    reply.error(EACCES);
                    return;
                }
                let fd = self.allocate_file_descriptor(ino as usize, read, write);
                reply.opened(fd, 0);
            }
            None => {
                reply.error(ENOENT);
            }
        }
    }

    // read [offset, offset + size)
    // - EOF < offset + size -> return EOF - offset
    // - EOF > offset + size -> return size
    fn read(
        &mut self,
        req: &Request<'_>,
        ino: u64,
        fh: u64,
        offset: i64,
        size: u32,
        _flags: i32,
        _lock_owner: Option<u64>, // 用不到!
        reply: ReplyData,
    ) {
        assert_eq!(self.file_handle_map.get(&fh).unwrap().0, ino as usize);
        if let Some(inode) = self.get_inode(ino as usize) {
            if inode.is_dir() {
                reply.error(EISDIR);
                return;
            }
            if !check_access(req.uid(), req.gid(), inode.uid, inode.gid, inode.mode, R_OK) {
                reply.error(EACCES);
                return;
            }
            debug!("reading inode {:#x} (offset {} size {})", ino, offset, size);

            if offset as u32 >= inode.size {
                // offset 在 EOF 后面, 直接返回一个 0 长度的空 buffer
                reply.data(&Vec::new());
                return;
            }

            // let read_length = size.min(inode.size.saturating_sub(offset as u32)) as usize;
            // 这和下面那个是等同的但是不利于让人看懂……
            let read_length = if offset as u32 + size <= inode.size {
                size // 没有越过 EOF, 读取 size 个 byte
            } else {
                inode.size - offset as u32 // 越过了 EOF, 读取 inode.size - offset 个 byte
            } as usize;

            let mut read_buffer = vec![0u8; read_length];
            let mut read_ptr = 0usize;

            let inode = inode.clone();

            while read_ptr < read_length {
                let current_point = offset as usize + read_ptr;
                let current_block_index = current_point / BLOCK_SIZE;
                let current_offset = current_point % BLOCK_SIZE;

                let read_length_within_block = if BLOCK_SIZE - current_offset < read_length - read_ptr {
                    BLOCK_SIZE - current_offset // 可以读到 block 最后
                } else {
                    read_length - read_ptr // 读到中途会停下来
                };

                if let Some(block) = self.access_block::<DataBlock>(&inode, current_block_index) {
                    (&mut read_buffer[read_ptr .. read_ptr + read_length_within_block])
                        .copy_from_slice(&block.block.0[current_offset .. current_offset + read_length_within_block]);
                    read_ptr += read_length_within_block;
                } else {
                    reply.error(EIO);
                    return;
                }
            }

            reply.data(&read_buffer);
        }
    }

    // 写了多少就返回多少
    fn write(
        &mut self,
        req: &Request<'_>,
        ino: u64,
        fh: u64,
        offset: i64,
        data: &[u8],
        write_flags: u32,
        flags: i32,
        _lock_owner: Option<u64>,
        reply: ReplyWrite,
    ) {
        assert_eq!(self.file_handle_map.get(&fh).unwrap().0, ino as usize);
        if let Some(inode) = self.get_inode(ino as usize) {
            if inode.is_dir() {
                reply.error(EISDIR);
                return;
            }
            if !check_access(req.uid(), req.gid(), inode.uid, inode.gid, inode.mode, W_OK) {
                reply.error(EACCES);
                return;
            }
            debug!("writing inode {:#x} (offset {} size {})", ino, offset, data.len());
            let write_length = data.len();
            let mut write_ptr = 0usize;

            let mut inode = inode.clone();

            while write_ptr < write_length {
                let current_point = offset as usize + write_ptr;
                let current_block_index = current_point / BLOCK_SIZE;
                let current_offset = current_point % BLOCK_SIZE;

                let write_length_within_block = if BLOCK_SIZE - current_offset < write_length - write_ptr {
                    BLOCK_SIZE - current_offset // 可以写满 block
                } else {
                    write_length - write_ptr // 写完 buffer 就停下来
                };

                // 当前块已分配, 直接往里写
                if let Some(block) = self.access_block_mut::<DataBlock>(&inode, current_block_index) {
                    debug!("writing in block {} within inode", current_block_index);
                    (block.block.0[ .. current_offset + write_length_within_block])
                        .copy_from_slice(&data[write_ptr .. write_ptr + write_length_within_block]);
                    write_ptr += write_length_within_block;
                } else { // 当前块未分配，尝试分配
                    if let Some((block_index, block_index_within_inode)) = self.allocate_block_for(&mut inode) {
                        debug!("allocating block {} within inode, block index is {}", block_index_within_inode, block_index);
                        // 能分配, 往里写
                        let block = self.access_block_mut::<DataBlock>(&inode, block_index_within_inode).unwrap();
                        (block.block.0[ .. current_offset + write_length_within_block])
                            .copy_from_slice(&data[write_ptr .. write_ptr + write_length_within_block]);
                        write_ptr += write_length_within_block;
                    } else {
                        // 分配不了, 没空间了
                        break;
                    }
                }
            }

            inode.size = inode.size.max(offset as u32 + write_length as u32);
            self.update_inode(ino as usize, inode);
            reply.written(write_length as u32);
        } else {
            reply.error(ENOENT);
        }
    }

    fn release(
        &mut self,
        _req: &Request<'_>,
        ino: u64,
        fh: u64,
        _flags: i32,
        _lock_owner: Option<u64>,
        _flush: bool,
        reply: ReplyEmpty,
    ) {
        debug!("release(ino: {:#x?}, fh: {}", ino, fh);
        if self.file_handle_map.contains_key(&fh) {
            self.file_handle_map.remove(&fh);
            reply.ok();
        } else {
            reply.error(EBADF);
        }
    }

    fn opendir(&mut self, req: &Request<'_>, ino: u64, flags: i32, reply: ReplyOpen) {
        debug!("opendir(ino: {:#x?}, flags: {:#x?})", ino, flags);
        let (access_mask, read, write) = match flags & O_ACCMODE {
            O_RDONLY => {
                // Behavior is undefined, but most filesystems return EACCES
                if flags & libc::O_TRUNC != 0 {
                    reply.error(libc::EACCES);
                    return;
                }
                (R_OK, true, false)
            }
            O_WRONLY => (W_OK, false, true),
            O_RDWR => (R_OK | W_OK, true, true),
            _ => {
                // flag 非法
                reply.error(EINVAL);
                return;
            }
        };

        match self.get_inode(ino as usize) {
            Some(inode) => {
                if !check_access(
                    req.uid(),
                    req.gid(),
                    inode.uid,
                    inode.gid,
                    inode.mode,
                    access_mask,
                ) {
                    reply.error(EACCES);
                    return;
                }
                let fd = self.allocate_file_descriptor(ino as usize, read, write);
                reply.opened(fd, 0);
            }
            None => {
                reply.error(ENOENT);
            }
        }
    }

    fn readdir(
        &mut self,
        req: &Request<'_>,
        ino: u64,
        fh: u64, // 如果 invoke 它的 opendir 里有指定 fh, 那么这里会收到 fh 参数
        offset: i64,
        mut reply: ReplyDirectory,
    ) {
        assert_eq!(self.file_handle_map.get(&fh).unwrap().0, ino as usize);
        if let Some(inode) = self.get_inode(ino as usize) {
            if !inode.is_dir() {
                reply.error(ENOTDIR);
                return;
            }

            if !check_access(req.uid(), req.gid(), inode.uid, inode.gid, inode.mode, R_OK) {
                reply.error(EACCES);
                return;
            }

            debug!("reading dir entries from inode {:#x} with offset {}", ino, offset);
            let inode = inode.clone();

            self.load_direntry_map(ino as usize, &inode).unwrap();
            for (entry_index, (name, dir_entry)) in self
                .dir_entry_map
                .get(&(ino as usize))
                .unwrap()
                .iter()
                .enumerate()
                .skip(offset as usize)
            {
                debug!("  entry {} from inode {:#x} with name {:?}", entry_index, dir_entry.inode, name);
                if reply.add(
                    dir_entry.inode as u64,
                    entry_index as i64 + 1,
                    to_filetype(dir_entry.file_type).expect("not 0x0!"),
                    name
                ) {
                    break;
                }
            }

            reply.ok();
        } else {
            reply.error(ENOENT);
        }
    }

    fn releasedir(
        &mut self,
        _req: &Request<'_>,
        ino: u64,
        fh: u64,
        _flags: i32,
        reply: ReplyEmpty,
    ) {
        debug!("releasedir(ino: {:#x?}, fh: {}", ino, fh);
        if self.file_handle_map.contains_key(&fh) {
            self.file_handle_map.remove(&fh);
            reply.ok();
        } else {
            reply.error(EBADF);
        }
    }

    fn access(&mut self, req: &Request<'_>, ino: u64, mask: i32, reply: ReplyEmpty) {
        // mask:
        // - 要么是 libc::F_OK (aka 0), 检查文件是否存在
        // - 要么是 libc::R_OK,libc::W_OK,libc::X_OK (aka 4/2/1) 构成的 bitmask, 检查是否有对应权限
        debug!("Filesystem::access(ino: {}, mask: {})", ino, mask);

        if let Some(inode) = self.get_inode(ino as usize) {
            if mask == libc::F_OK // 只要检查是否存在
                || check_access(req.uid(), req.gid(), inode.uid, inode.gid, inode.mode, mask)
            // 需要检查 rwx 权限
            {
                reply.ok();
            } else {
                reply.error(EACCES);
            }
        } else {
            reply.error(ENOENT);
        }
    }
}