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use crate::fs::{make_pipe, open, pselect, DiskInodeType, OpenFlags, StatMode, open_root_inode};
use crate::fs::{ppoll, Dirent, FdSet, File, FileDescriptor, FileLike, Null, Stat, Zero, TTY};
use crate::mm::{
    copy_from_user, copy_from_user_array, copy_to_user, copy_to_user_array, translated_byte_buffer,
    translated_byte_buffer_append_to_existed_vec, translated_ref, translated_refmut,
    translated_str, MapPermission, UserBuffer,
};
use crate::task::{current_task, current_user_token};
use crate::timer::TimeSpec;
use crate::{move_ptr_to_opt, ptr_to_opt_ref, ptr_to_opt_ref_mut};
use alloc::sync::Arc;
use alloc::vec::Vec;
use core::mem::size_of;
use core::ptr::{null, null_mut};
use log::{debug, error, info, trace, warn};
use num_enum::FromPrimitive;

use super::errno::*;

pub const AT_FDCWD: usize = 100usize.wrapping_neg();

pub fn sys_getcwd(buf: usize, size: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    if !inner
        .memory_set
        .contains_valid_buffer(buf, size, MapPermission::W)
    {
        // buf points to a bad address.
        return EFAULT;
    }
    if size == 0 && buf != 0 {
        // The size argument is zero and buf is not a NULL pointer.
        return EINVAL;
    }
    if inner.working_dir.len() >= size {
        // The size argument is less than the length of the absolute pathname of the working directory,
        // including the terminating null byte.
        return ERANGE;
    }
    let token = inner.get_user_token();
    UserBuffer::new(translated_byte_buffer(token, buf as *const u8, size))
        .write(inner.working_dir.as_bytes());
    buf as isize
}

bitflags! {
    pub struct SeekWhence: u32 {
        const SEEK_SET  =   0; /* set to offset bytes.  */
        const SEEK_CUR  =   1; /* set to its current location plus offset bytes.  */
        const SEEK_END  =   2; /* set to the size of the file plus offset bytes.  */
    }
}

pub fn sys_lseek(fd: usize, offset: usize, whence: u32) -> isize {
    // whence is not valid
    let whence = match SeekWhence::from_bits(whence) {
        Some(whence) => whence,
        None => {
            warn!("[sys_lseek] unknown flags");
            return EINVAL;
        }
    };
    info!(
        "[sys_lseek] fd: {}, offset: {}, whence: {:?}",
        fd, offset, whence,
    );
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    // fd is not a valid file descriptor
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
    match &file_descriptor.file {
        // On Linux, using lseek() on a terminal device returns ESPIPE
        FileLike::Abstract(_) => return ESPIPE,
        // whence should be check in lseek
        FileLike::Regular(file) => file.lseek(offset as isize, whence),
    }
}

pub fn sys_read(fd: usize, buf: usize, count: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    // fd is not a valid file descriptor
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
    let file: Arc<dyn File + Send + Sync> = match &file_descriptor.file {
        FileLike::Abstract(file) => file.clone(),
        FileLike::Regular(file) => file.clone(),
    };
    // fd is not open for reading
    if !file.readable() {
        return EBADF;
    }
    // buf is outside your accessible address space.
    if !inner
        .memory_set
        .contains_valid_buffer(buf, count, MapPermission::W)
    {
        return EFAULT;
    }
    let token = inner.get_user_token();
    drop(inner);
    file.read(UserBuffer::new(translated_byte_buffer(
        token,
        buf as *const u8,
        count,
    ))) as isize
}

pub fn sys_write(fd: usize, buf: usize, count: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    // fd is not a valid file descriptor
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
    let file: Arc<dyn File + Send + Sync> = match &file_descriptor.file {
        FileLike::Abstract(file) => file.clone(),
        FileLike::Regular(file) => file.clone(),
    };
    // fd is not open for writing
    if !file.writable() {
        return EBADF;
    }
    // buf is outside your accessible address space.
    if !inner
        .memory_set
        .contains_valid_buffer(buf, count, MapPermission::R)
    {
        return EFAULT;
    }
    let token = inner.get_user_token();
    drop(inner);
    file.write(UserBuffer::new(translated_byte_buffer(
        token,
        buf as *const u8,
        count,
    ))) as isize
}

#[repr(C)]
#[derive(Clone, Copy)]
struct IOVec {
    iov_base: *const u8, /* Starting address */
    iov_len: usize,      /* Number of bytes to transfer */
}

pub fn sys_readv(fd: usize, iov: usize, iovcnt: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    // fd is not a valid file descriptor
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
    let file: Arc<dyn File + Send + Sync> = match &file_descriptor.file {
        FileLike::Abstract(file) => file.clone(),
        FileLike::Regular(file) => file.clone(),
    };
    // fd is not open for reading
    if !file.readable() {
        return EBADF;
    }
    let token = inner.get_user_token();
    drop(inner);
    let mut iovecs = Vec::<IOVec>::with_capacity(iovcnt);
    copy_from_user_array(token, iov as *const IOVec, iovecs.as_mut_ptr(), iovcnt);
    unsafe { iovecs.set_len(iovcnt) };
    file.read(UserBuffer::new(iovecs.iter().fold(
        Vec::new(),
        |buffer, iovec| {
            // This function aims to avoid the extra cost caused by `Vec::append` (it moves data on heap)
            translated_byte_buffer_append_to_existed_vec(
                Some(buffer),
                token,
                iovec.iov_base,
                iovec.iov_len,
            )
        },
    ))) as isize
}

pub fn sys_writev(fd: usize, iov: usize, iovcnt: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    // fd is not a valid file descriptor
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
    let file: Arc<dyn File + Send + Sync> = match &file_descriptor.file {
        FileLike::Abstract(file) => file.clone(),
        FileLike::Regular(file) => file.clone(),
    };
    // fd is not open for writing
    if !file.writable() {
        return EBADF;
    }
    let token = inner.get_user_token();
    drop(inner);
    let mut iovecs = Vec::<IOVec>::with_capacity(iovcnt);
    copy_from_user_array(token, iov as *const IOVec, iovecs.as_mut_ptr(), iovcnt);
    unsafe { iovecs.set_len(iovcnt) };
    file.write(UserBuffer::new(iovecs.iter().fold(
        Vec::new(),
        |buffer, iovec| {
            // for debug
            {
                if !iovec.iov_base.is_null() {
                    let mut temp = Vec::<u8>::with_capacity(iovec.iov_len);
                    copy_from_user_array(token, iovec.iov_base, temp.as_mut_ptr(), iovec.iov_len);
                    unsafe {
                        temp.set_len(iovec.iov_len);
                    }
                    info!(
                        "[sys_writev] Iterating... content: {:?}, iovlen: {}",
                        core::str::from_utf8(temp.as_slice()),
                        iovec.iov_len
                    );
                }
            }
            // This function aims to avoid the extra cost caused by `Vec::append` (it moves data on heap)
            translated_byte_buffer_append_to_existed_vec(
                Some(buffer),
                token,
                iovec.iov_base,
                iovec.iov_len,
            )
        },
    ))) as isize
}

/// If offset is not NULL, then it points to a variable holding the
/// file offset from which sendfile() will start reading data from
/// in_fd.
///
/// When sendfile() returns,
/// this variable will be set to the offset of the byte following
/// the last byte that was read.
///
/// If offset is not NULL, then sendfile() does not modify the file
/// offset of in_fd; otherwise the file offset is adjusted to reflect
/// the number of bytes read from in_fd.
///
/// If offset is NULL, then data will be read from in_fd starting at
/// the file offset, and the file offset will be updated by the call.
pub fn sys_sendfile(out_fd: usize, in_fd: usize, offset: *mut usize, count: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    if in_fd >= inner.fd_table.len()
        || inner.fd_table[in_fd].is_none()
        || out_fd >= inner.fd_table.len()
        || inner.fd_table[out_fd].is_none()
    {
        return EBADF;
    }
    info!("[sys_sendfile] outfd: {}, in_fd: {}", out_fd, in_fd);
    let in_file = match &inner.fd_table[in_fd].as_ref().unwrap().file {
        // The in_fd argument must correspond to a file which supports mmap-like operations
        FileLike::Abstract(_) => return EINVAL,
        FileLike::Regular(file) => {
            // fd is not open for reading
            if !file.readable() {
                return EBADF;
            }
            file.clone()
        }
    };
    let out_file = match &inner.fd_table[out_fd].as_ref().unwrap().file {
        FileLike::Abstract(file) => {
            // fd is not open for writing
            if !file.writable() {
                return EBADF;
            }
            file.clone()
        }
        FileLike::Regular(file) => {
            // fd is not open for writing
            if !file.writable() {
                return EBADF;
            }
            file.clone()
        }
    };
    let token = inner.get_user_token();
    drop(inner);

    // turn a pointer in user space into a pointer in kernel space if it is not null
    let offset = if offset.is_null() {
        offset
    } else {
        translated_refmut(token, offset) as *mut usize
    };

    // a buffer in kernel
    const BUFFER_SIZE: usize = 4096;
    let mut buffer = Vec::<u8>::with_capacity(BUFFER_SIZE);

    let mut left_bytes = count;
    let mut write_size = 0;
    loop {
        unsafe {
            buffer.set_len(left_bytes.min(BUFFER_SIZE));
        }
        let read_size = in_file.kread(unsafe { offset.as_mut() }, buffer.as_mut_slice());
        if read_size == 0 {
            break;
        }
        unsafe {
            buffer.set_len(read_size);
        }
        write_size += out_file.kwrite(None, buffer.as_slice());
        left_bytes -= read_size;
    }
    info!("[sys_sendfile] written bytes: {}", write_size);
    write_size as isize
}

pub fn sys_close(fd: usize) -> isize {
    info!("[sys_close] fd:{}", fd);
    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    inner.fd_table[fd].take();
    SUCCESS
}

/// # Warning
/// Only O_CLOEXEC is supported now
pub fn sys_pipe2(pipefd: usize, flags: u32) -> isize {
    let flags = match OpenFlags::from_bits(flags) {
        Some(flags) => {
            // only O_CLOEXEC | O_DIRECT | O_NONBLOCK are valid in pipe2()
            if flags
                .difference(OpenFlags::O_CLOEXEC | OpenFlags::O_DIRECT | OpenFlags::O_NONBLOCK)
                .is_empty()
            {
                flags
            // some flags are invalid in pipe2(), they are all valid OpenFlags though
            } else {
                warn!(
                    "[sys_pipe2] invalid flags: {:?}",
                    flags.difference(
                        OpenFlags::O_CLOEXEC | OpenFlags::O_DIRECT | OpenFlags::O_NONBLOCK
                    )
                );
                return EINVAL;
            }
        }
        // contains invalid OpenFlags
        None => {
            warn!("[sys_pipe2] unknown flags");
            return EINVAL;
        }
    };
    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();
    let (pipe_read, pipe_write) = make_pipe();
    let read_fd = match inner.alloc_fd() {
        Some(fd) => fd,
        None => return EMFILE,
    };
    inner.fd_table[read_fd] = Some(FileDescriptor::new(
        flags.contains(OpenFlags::O_CLOEXEC),
        FileLike::Abstract(pipe_read),
    ));
    let write_fd = match inner.alloc_fd() {
        Some(fd) => fd,
        None => return EMFILE,
    };
    inner.fd_table[write_fd] = Some(FileDescriptor::new(
        flags.contains(OpenFlags::O_CLOEXEC),
        FileLike::Abstract(pipe_write),
    ));
    let token = inner.get_user_token();
    drop(inner);
    copy_to_user_array(
        token,
        [read_fd as u32, write_fd as u32].as_ptr(),
        pipefd as *mut u32,
        2,
    );
    info!(
        "[sys_pipe2] read_fd: {}, write_fd: {}, flags: {:?}",
        read_fd, write_fd, flags
    );
    SUCCESS
}

pub fn sys_getdents64(fd: usize, dirp: *mut u8, count: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    let token = inner.get_user_token();

    if fd == AT_FDCWD {
        let dirent_vec = inner.working_inode.get_dirent(count);
        copy_to_user_array(
            token,
            dirent_vec.as_ptr(),
            dirp as *mut Dirent,
            dirent_vec.len(),
        );
        info!("[sys_getdents64] fd: AT_FDCWD, count: {}", count);
        (dirent_vec.len() * size_of::<Dirent>()) as isize
    } else {
        if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
            return EBADF;
        }
        let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
        match &file_descriptor.file {
            FileLike::Regular(file) => {
                    let dirent_vec = file.get_dirent(count);
                    copy_to_user_array(
                        token,
                        dirent_vec.as_ptr(),
                        dirp as *mut Dirent,
                        dirent_vec.len(),
                    );
                    info!("[sys_getdents64] fd: {}, count: {}", fd, count);
                    (dirent_vec.len() * size_of::<Dirent>()) as isize
                }
            _ => ENOTDIR,
        }
    }
}

pub fn sys_dup(oldfd: usize) -> isize {
    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();
    if oldfd >= inner.fd_table.len() || inner.fd_table[oldfd].is_none() {
        return EBADF;
    }
    let newfd = match inner.alloc_fd() {
        Some(fd) => fd,
        None => return EMFILE,
    };
    inner.fd_table[newfd] = Some(inner.fd_table[oldfd].as_ref().unwrap().clone());
    newfd as isize
}

pub fn sys_dup3(oldfd: usize, newfd: usize, flags: u32) -> isize {
    info!(
        "[sys_dup3] oldfd: {}, newfd: {}, flags: {:?}",
        oldfd,
        newfd,
        OpenFlags::from_bits(flags)
    );
    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();
    if oldfd >= inner.fd_table.len() || inner.fd_table[oldfd].is_none() {
        return EBADF;
    }
    let is_cloexec = match OpenFlags::from_bits(flags) {
        Some(OpenFlags::O_CLOEXEC) => true,
        // `O_RDONLY == 0`, so it means *NO* cloexec in fact
        Some(OpenFlags::O_RDONLY) => false,
        // flags contain an invalid value
        Some(flags) => {
            warn!("[sys_dup3] invalid flags: {:?}", flags);
            return EINVAL;
        }
        None => {
            warn!("[sys_dup3] unknown flags");
            return EINVAL;
        }
    };
    if oldfd == newfd {
        return EINVAL;
    }
    if newfd >= inner.fd_table.len() {
        match inner.alloc_fd_at(newfd) {
            // `newfd` is not allocated in this case, so `fd` should never differ from `newfd`
            Some(fd) => assert_eq!(fd, newfd),
            // newfd is out of the allowed range for file descriptors
            None => return EBADF,
        };
    }
    inner.fd_table[newfd] = Some(inner.fd_table[oldfd].as_ref().unwrap().clone());
    inner.fd_table[newfd]
        .as_mut()
        .unwrap()
        .set_cloexec(is_cloexec);
    newfd as isize
}

// This syscall is not complete at all, only /read proc/self/exe
pub fn sys_readlinkat(dirfd: usize, pathname: *const u8, buf: *mut u8, bufsiz: usize) -> isize {
    if dirfd == AT_FDCWD {
        let token = current_user_token();
        let path = translated_str(token, pathname);
        if path.as_str() != "/proc/self/exe" {
            panic!("sys_readlinkat: pathname not support");
        }
        let mut userbuf = UserBuffer::new(translated_byte_buffer(token, buf, bufsiz));
        //let procinfo = "/lmbench_all\0";
        let procinfo = "/busybox\0";
        let buff = procinfo.as_bytes();
        userbuf.write(buff);

        let len = procinfo.len() - 1;
        info!(
            "[sys_readlinkat] dirfd = {}, pathname = {}, *buf = 0x{:X}, bufsiz = {}, len = {}",
            dirfd, path, buf as usize, bufsiz, len
        );

        return len as isize;
    } else {
        panic!("sys_readlinkat: fd not support");
    }
}

bitflags! {
    pub struct FstatatFlags: u32 {
        const AT_EMPTY_PATH = 0x1000;
        const AT_NO_AUTOMOUNT = 0x800;
        const AT_SYMLINK_NOFOLLOW = 0x100;
    }
}

pub fn sys_fstatat(dirfd: usize, path: *const u8, buf: *mut u8, flags: u32) -> isize {
    let token = current_user_token();
    let path = translated_str(token, path);
    let flags = match FstatatFlags::from_bits(flags) {
        Some(flags) => flags,
        None => {
            warn!("[sys_fstatat] unknown flags");
            return EINVAL;
        }
    };

    info!(
        "[sys_fstatat] dirfd = {}, path = {:?}, flags: {:?}",
        dirfd, path, flags,
    );

    let inode = match __openat(dirfd, &path) {
        Ok(inode) => inode,
        Err(errno) => return errno,
    };

    copy_to_user(token, inode.stat().as_ref(), buf as *mut Stat);
    SUCCESS
}

pub fn sys_fstat(fd: usize, statbuf: *mut u8) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    let token = inner.get_user_token();

    if fd == AT_FDCWD {
        let stat = inner.working_inode.stat();
        copy_to_user(token, stat.as_ref(), statbuf as *mut Stat);
        info!("[syscall_fstat] fd = {}, stat = {:?}", fd, stat);
        SUCCESS
    } else {
        if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
            return EBADF;
        }
        let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
        let stat = match &file_descriptor.file {
            FileLike::Regular(inode) => inode.stat(),
            FileLike::Abstract(abstract_file) => abstract_file.stat(),
        };
        copy_to_user(token, stat.as_ref(), statbuf as *mut Stat);
        info!("[syscall_fstat] fd: {}, stat: {:?}", fd, stat);
        SUCCESS
    }
}

pub fn sys_chdir(path: *const u8) -> isize {
    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();
    let token = inner.get_user_token();
    let path = translated_str(token, path);
    info!("[sys_chdir] path: {}", path);

    if path.starts_with("/") {
        match open(
            &open_root_inode(),
            path.as_str(),
            OpenFlags::O_RDONLY,
            DiskInodeType::Directory,
        ) {
            Ok(inode) => {
                if !inode.is_dir() {
                    return ENOTDIR;
                }
                inner.working_inode = inode;
                inner.working_dir = path;
                SUCCESS
            }
            Err(errno) => errno,
        }
    } else {
        match open(
            &inner.working_inode,
            path.as_str(),
            OpenFlags::O_RDONLY,
            DiskInodeType::Directory,
        ) {
            Ok(inode) => {
                if !inode.is_dir() {
                    return ENOTDIR;
                }
                inner.working_inode = inode;
                inner.working_dir += path.as_str();
                SUCCESS
            }
            Err(errno) => errno,
        }
    }
}

pub fn sys_openat(dirfd: usize, path: *const u8, flags: u32, mode: u32) -> isize {
    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();
    let token = inner.get_user_token();
    let path = translated_str(token, path);
    let flags = match OpenFlags::from_bits(flags) {
        Some(flags) => flags,
        None => {
            warn!("[sys_openat] unknown flags");
            return EINVAL;
        }
    };
    let mode = StatMode::from_bits(mode);
    info!(
        "[sys_openat] dirfd: {}, path:{}, flags:{:?}, mode:{:?}",
        dirfd, path, flags, mode
    );
    if path.starts_with("/dev") {
        let file = {
            if path.contains("tty") {
                FileLike::Abstract(TTY.clone())
            } else if path.contains("null") {
                FileLike::Abstract(Arc::new(Null))
            } else if path.contains("zero") {
                FileLike::Abstract(Arc::new(Zero))
            } else {
                warn!("[sys_openat] device file not supported: {}", path);
                return ENOENT;
            }
        };
        let fd = match inner.alloc_fd() {
            Some(fd) => fd,
            None => return EMFILE,
        };
        inner.fd_table[fd] = Some(FileDescriptor::new(false, file));
        return fd as isize;
    }
    let result = if path.starts_with("/") {
        open(&open_root_inode(), path.as_str(), flags, DiskInodeType::File)
    } else {
        if dirfd == AT_FDCWD {
            open(
                &inner.working_inode,
                path.as_str(),
                flags,
                DiskInodeType::File,
            )
        } else {
            if dirfd >= inner.fd_table.len() || inner.fd_table[dirfd].is_none() {
                Err(EBADF)
            } else {
                let file_descriptor = inner.fd_table[dirfd].as_ref().unwrap();
                match &file_descriptor.file {
                    FileLike::Regular(inode) => {
                        inode.open_by_relative_path(path.as_str(), flags, DiskInodeType::File)
                    }
                    FileLike::Abstract(_) => Err(ENOTDIR),
                }
            }
        }
    };
    match result {
        Ok(inode) => {
            let fd = match inner.alloc_fd() {
                Some(fd) => fd,
                None => return EMFILE,
            };
            inner.fd_table[fd] = Some(FileDescriptor::new(
                flags.contains(OpenFlags::O_CLOEXEC),
                FileLike::Regular(inode),
            ));
            fd as isize
        }
        Err(errno) => {
            warn!("[sys_openat] open failed with errno: {}", errno);
            errno
        }
    }
}

pub fn sys_ioctl(fd: usize, cmd: u32, arg: usize) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }
    let file_descriptor = inner.fd_table[fd].as_ref().unwrap();
    let file: Arc<dyn File + Send + Sync> = match &file_descriptor.file {
        FileLike::Abstract(f) => f.clone(),
        FileLike::Regular(f) => f.clone(),
    };
    drop(inner);
    return file.ioctl(cmd, arg);
}

pub fn sys_ppoll(poll_fd: usize, nfds: usize, time_spec: usize, sigmask: usize) -> isize {
    ppoll(
        poll_fd,
        nfds,
        time_spec,
        sigmask as *const crate::task::Signals,
    )
}

pub fn sys_mkdirat(dirfd: usize, path: *const u8, mode: u32) -> isize {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    let token = inner.get_user_token();
    let path = translated_str(token, path);
    info!(
        "[sys_mkdirat] dirfd: {}, path: {}, mode: {:?}",
        dirfd,
        path,
        StatMode::from_bits(mode)
    );
    if path.starts_with("/") {
        match open(
            &open_root_inode(),
            path.as_str(),
            OpenFlags::O_CREAT | OpenFlags::O_EXCL,
            DiskInodeType::Directory,
        ) {
            Ok(_) => SUCCESS,
            Err(errno) => errno,
        }
    } else {
        if dirfd == AT_FDCWD {
            match open(
                &inner.working_inode,
                path.as_str(),
                OpenFlags::O_CREAT | OpenFlags::O_EXCL,
                DiskInodeType::Directory,
            ) {
                Ok(_) => SUCCESS,
                Err(errno) => errno,
            }
        } else {
            if dirfd >= inner.fd_table.len() || inner.fd_table[dirfd].is_none() {
                return EBADF;
            }
            let file_descriptor = inner.fd_table[dirfd].as_ref().unwrap();
            match &file_descriptor.file {
                FileLike::Regular(inode) => {
                    match inode.open_by_relative_path(
                        path.as_str(),
                        OpenFlags::O_CREAT | OpenFlags::O_EXCL,
                        DiskInodeType::Directory,
                    ) {
                        Ok(_) => SUCCESS,
                        Err(errno) => errno,
                    }
                }
                _ => ENOTDIR,
            }
        }
    }
}

bitflags! {
    pub struct UnlinkatFlags: u32 {
        const AT_REMOVEDIR = 0x200;
    }
}

/// # Warning
/// Currently we have no hard-link so this syscall will remove file directly.
/// `AT_REMOVEDIR` is not supported yet.
pub fn sys_unlinkat(dirfd: usize, path: *const u8, flags: u32) -> isize {
    let token = current_user_token();
    let path = translated_str(token, path);
    let flags = match UnlinkatFlags::from_bits(flags) {
        Some(flags) => flags,
        None => {
            warn!("[sys_unlinkat] unknown flags");
            return EINVAL;
        }
    };
    info!(
        "[sys_unlinkat] dirfd: {}, path: {}, flags: {:?}",
        dirfd, path, flags
    );

    let inode = match __openat(dirfd, &path) {
        Ok(inode) => inode,
        Err(errno) => return errno,
    };

    if inode.is_dir() {
        if flags.contains(UnlinkatFlags::AT_REMOVEDIR) {
            todo!();
        } else {
            return EISDIR;
        }
    }
    inode.delete();
    SUCCESS
}

bitflags! {
    pub struct UmountFlags: u32 {
        const MNT_FORCE           =   1;
        const MNT_DETACH          =   2;
        const MNT_EXPIRE          =   4;
        const UMOUNT_NOFOLLOW     =   8;
    }
}

pub fn sys_umount2(target: *const u8, flags: u32) -> isize {
    if target.is_null() {
        return EINVAL;
    }
    let token = current_user_token();
    let target = translated_str(token, target);
    let flags = match UmountFlags::from_bits(flags) {
        Some(flags) => flags,
        None => return EINVAL,
    };
    info!("[sys_umount2] target: {}, flags: {:?}", target, flags);
    warn!("[sys_umount2] fake implementation!");
    SUCCESS
}

bitflags! {
    pub struct MountFlags: usize {
        const MS_RDONLY         =   1;
        const MS_NOSUID         =   2;
        const MS_NODEV          =   4;
        const MS_NOEXEC         =   8;
        const MS_SYNCHRONOUS    =   16;
        const MS_REMOUNT        =   32;
        const MS_MANDLOCK       =   64;
        const MS_DIRSYNC        =   128;
        const MS_NOATIME        =   1024;
        const MS_NODIRATIME     =   2048;
        const MS_BIND           =   4096;
        const MS_MOVE           =   8192;
        const MS_REC            =   16384;
        const MS_SILENT         =   32768;
        const MS_POSIXACL       =   (1<<16);
        const MS_UNBINDABLE     =   (1<<17);
        const MS_PRIVATE        =   (1<<18);
        const MS_SLAVE          =   (1<<19);
        const MS_SHARED         =   (1<<20);
        const MS_RELATIME       =   (1<<21);
        const MS_KERNMOUNT      =   (1<<22);
        const MS_I_VERSION      =   (1<<23);
        const MS_STRICTATIME    =   (1<<24);
        const MS_LAZYTIME       =   (1<<25);
        const MS_NOREMOTELOCK   =   (1<<27);
        const MS_NOSEC          =   (1<<28);
        const MS_BORN           =   (1<<29);
        const MS_ACTIVE         =   (1<<30);
        const MS_NOUSER         =   (1<<31);
    }
}

pub fn sys_mount(
    source: *const u8,
    target: *const u8,
    filesystemtype: *const u8,
    mountflags: usize,
    data: *const u8,
) -> isize {
    if source.is_null() || target.is_null() || filesystemtype.is_null() {
        return EINVAL;
    }
    let token = current_user_token();
    let source = translated_str(token, source);
    let target = translated_str(token, target);
    let filesystemtype = translated_str(token, filesystemtype);
    // infallible
    let mountflags = MountFlags::from_bits(mountflags).unwrap();
    info!(
        "[sys_mount] source: {}, target: {}, filesystemtype: {}, mountflags: {:?}, data: {:?}",
        source, target, filesystemtype, mountflags, data
    );
    warn!("[sys_mount] fake implementation!");
    SUCCESS
}

bitflags! {
    pub struct UtimensatFlags: u32 {
        const AT_SYMLINK_NOFOLLOW = 0x100;
    }
}

pub fn sys_utimensat(
    dirfd: usize,
    pathname: *const u8,
    times: *const [TimeSpec; 2],
    flags: u32,
) -> isize {
    const UTIME_NOW: usize = 0x3fffffff;
    const UTIME_OMIT: usize = 0x3ffffffe;

    let token = current_user_token();
    let path = translated_str(token, pathname);
    let flags = match UtimensatFlags::from_bits(flags) {
        Some(flags) => flags,
        None => {
            warn!("[sys_utimensat] unknown flags");
            return EINVAL;
        }
    };

    info!(
        "[sys_utimensat] dirfd: {}, path: {}, times: {:?}, flags: {:?}",
        dirfd, path, times, flags
    );

    let inode = match __openat(dirfd, &path) {
        Ok(inode) => inode,
        Err(errno) => return errno,
    };

    let now = TimeSpec::now();
    let timespec = &mut [now; 2];
    let mut atime = Some(now.tv_sec);
    let mut mtime = Some(now.tv_sec);
    if !times.is_null() {
        copy_from_user(token, times, timespec);
        match timespec[0].tv_nsec {
            UTIME_NOW => (),
            UTIME_OMIT => atime = None,
            _ => atime = Some(timespec[0].tv_sec),
        }
        match timespec[1].tv_nsec {
            UTIME_NOW => (),
            UTIME_OMIT => mtime = None,
            _ => mtime = Some(timespec[1].tv_sec),
        }
    }

    inode.set_timestamp(None, atime, mtime);
    SUCCESS
}

/// # Warning
/// `acquire_inner_lock()` is called in this function
fn __openat(dirfd: usize, path: &str) -> Result<Arc<crate::fs::OSInode>, isize> {
    let task = current_task().unwrap();
    let inner = task.acquire_inner_lock();
    let inode = if path.starts_with("/") {
        if let Ok(inode) = open(&open_root_inode(), path, OpenFlags::O_RDONLY, DiskInodeType::File) {
            inode
        } else {
            return Err(ENOENT);
        }
    } else {
        if dirfd == AT_FDCWD {
            if let Ok(inode) = open(
                &inner.working_inode,
                path,
                OpenFlags::O_RDONLY,
                DiskInodeType::File,
            ) {
                inode
            } else {
                return Err(ENOENT);
            }
        } else {
            if dirfd >= inner.fd_table.len() || inner.fd_table[dirfd].is_none() {
                return Err(EBADF);
            }
            let file_descriptor = inner.fd_table[dirfd].as_ref().unwrap();
            match &file_descriptor.file {
                FileLike::Regular(inode) => {
                    inode.open_by_relative_path(path, OpenFlags::O_RDONLY, DiskInodeType::File)?
                }
                FileLike::Abstract(_) => return Err(ENOTDIR),
            }
        }
    };
    Ok(inode)
}

#[allow(non_camel_case_types)]
#[derive(Debug, Eq, PartialEq, FromPrimitive)]
#[repr(u32)]
pub enum Command {
    DUPFD = 0,
    GETFD = 1,
    SETFD = 2,
    GETFL = 3,
    SETFL = 4,
    GETLK = 5,
    SETLK = 6,
    SETLKW = 7,
    SETOWN = 8,
    GETOWN = 9,
    SETSIG = 10,
    GETSIG = 11,
    SETOWN_EX = 15,
    GETOWN_EX = 16,
    GETOWNER_UIDS = 17,
    OFD_GETLK = 36,
    OFD_SETLK = 37,
    OFD_SETLKW = 38,
    SETLEASE = 1024,
    GETLEASE = 1025,
    NOTIFY = 1026,
    CANCELLK = 1029,
    DUPFD_CLOEXEC = 1030,
    SETPIPE_SZ = 1031,
    GETPIPE_SZ = 1032,
    ADD_SEALS = 1033,
    GET_SEALS = 1034,
    GET_RW_HINT = 1035,
    SET_RW_HINT = 1036,
    GET_FILE_RW_HINT = 1037,
    SET_FILE_RW_HINT = 1038,
    #[num_enum(default)]
    ILLEAGAL,
}

pub fn sys_fcntl(fd: usize, cmd: u32, arg: usize) -> isize {
    const FD_CLOEXEC: usize = 1;

    let task = current_task().unwrap();
    let mut inner = task.acquire_inner_lock();

    if fd >= inner.fd_table.len() || inner.fd_table[fd].is_none() {
        return EBADF;
    }

    info!(
        "[sys_fcntl] fd:{}, cmd:{:?}, arg:{:X}",
        fd,
        Command::from_primitive(cmd),
        arg
    );
    let file_descriptor = inner.fd_table[fd].as_mut().unwrap();
    match Command::from_primitive(cmd) {
        Command::DUPFD | Command::DUPFD_CLOEXEC => {
            let newfd = match inner.alloc_fd_at(arg) {
                Some(fd) => fd,
                // cmd is F_DUPFD and arg is negative or is greater than the maximum allowable value
                None => return EINVAL,
            };
            drop(inner);
            // take advantage of `DUPFD == 0`
            sys_dup3(fd, newfd, OpenFlags::O_CLOEXEC.bits() & cmd)
        }
        Command::GETFD => file_descriptor.get_cloexec() as isize,
        Command::SETFD => {
            file_descriptor.set_cloexec((arg & FD_CLOEXEC) != 0);
            if (arg & !FD_CLOEXEC) != 0 {
                warn!("[fcntl] Unsupported flag exists: {:X}", arg);
            }
            SUCCESS
        }
        Command::GETFL => {
            match &file_descriptor.file {
                // Access control is not fully implemented
                FileLike::Regular(_) => OpenFlags::O_RDWR.bits() as isize,
                FileLike::Abstract(_) => {
                    OpenFlags::O_RDWR.bits() as isize
                }
            }
        }
        command => {
            warn!("[fcntl] Unsupported command: {:?}", command);
            SUCCESS
        } // WARNING!!!
    }
}

pub fn sys_pselect(
    nfds: usize,
    read_fds: *mut FdSet,
    write_fds: *mut FdSet,
    exception_fds: *mut FdSet,
    timeout: *const TimeSpec,
    sigmask: *const crate::task::signal::Signals,
) -> isize {
    if (nfds as isize) < 0 {
        return -1;
    }
    let token = current_user_token();
    pselect(
        nfds,
        ptr_to_opt_ref_mut!(token, read_fds),
        ptr_to_opt_ref_mut!(token, write_fds),
        ptr_to_opt_ref_mut!(token, exception_fds),
        ptr_to_opt_ref!(token, timeout),
        sigmask,
    )
}

/// umask() sets the calling process's file mode creation mask (umask) to
/// mask & 0777 (i.e., only the file permission bits of mask are used),
/// and returns the previous value of the mask.
/// # WARNING
/// In current implementation, umask is always 0. This syscall won't do anything.
pub fn sys_umask(mask: u32) -> isize {
    info!("[sys_umask] mask: {:o}", mask);
    warn!("[sys_umask] In current implementation, umask is always 0. This syscall won't do anything.");
    0
}

bitflags! {
    pub struct FaccessatMode: u32 {
        const F_OK = 0;
        const R_OK = 4;
        const W_OK = 2;
        const X_OK = 1;
    }
    pub struct FaccessatFlags: u32 {
        const AT_SYMLINK_NOFOLLOW = 0x100;
        const AT_EACCESS = 0x200;
    }
}

pub fn sys_faccessat2(dirfd: usize, pathname: *const u8, mode: u32, flags: u32) -> isize {
    let token = current_user_token();
    let pathname = translated_str(token, pathname);
    let mode = match FaccessatMode::from_bits(mode) {
        Some(mode) => mode,
        None => {
            warn!("[sys_faccessat2] unknown mode");
            return EINVAL;
        }
    };
    let flags = match FaccessatFlags::from_bits(flags) {
        Some(flags) => flags,
        None => {
            warn!("[sys_faccessat2] unknown flags");
            return EINVAL;
        }
    };

    info!(
        "[sys_faccessat2] dirfd: {}, pathname: {}, mode: {:?}, flags: {:?}",
        dirfd, pathname, mode, flags
    );

    // Do not check user's authority, because user group is not implemented yet.
    // All existing files can be accessed.
    match __openat(dirfd, pathname.as_str()) {
        Ok(_) => SUCCESS,
        Err(errno) => errno
    }
}