//! Syscalls for file system

use core::cell::UnsafeCell;
use core::cmp::min;
use core::mem::size_of;
use rcore_fs::vfs::Timespec;

use crate::drivers::SOCKET_ACTIVITY;
use crate::fs::*;
use crate::memory::MemorySet;
use crate::sync::Condvar;

use bitvec::prelude::{BitSlice, BitVec, LittleEndian};

use super::*;

pub fn sys_read(fd: usize, base: *mut u8, len: usize) -> SysResult {
    let mut proc = process();
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!("read: fd: {}, base: {:?}, len: {:#x}", fd, base, len);
    }
    proc.vm.check_write_array(base, len)?;
    let slice = unsafe { slice::from_raw_parts_mut(base, len) };
    let file_like = proc.get_file_like(fd)?;
    let len = file_like.read(slice)?;
    Ok(len)
}

pub fn sys_write(fd: usize, base: *const u8, len: usize) -> SysResult {
    let mut proc = process();
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!("write: fd: {}, base: {:?}, len: {:#x}", fd, base, len);
    }
    proc.vm.check_read_array(base, len)?;
    let slice = unsafe { slice::from_raw_parts(base, len) };
    let file_like = proc.get_file_like(fd)?;
    let len = file_like.write(slice)?;
    Ok(len)
}

pub fn sys_pread(fd: usize, base: *mut u8, len: usize, offset: usize) -> SysResult {
    info!(
        "pread: fd: {}, base: {:?}, len: {}, offset: {}",
        fd, base, len, offset
    );
    let mut proc = process();
    proc.vm.check_write_array(base, len)?;

    let slice = unsafe { slice::from_raw_parts_mut(base, len) };
    let len = proc.get_file(fd)?.read_at(offset, slice)?;
    Ok(len)
}

pub fn sys_pwrite(fd: usize, base: *const u8, len: usize, offset: usize) -> SysResult {
    info!(
        "pwrite: fd: {}, base: {:?}, len: {}, offset: {}",
        fd, base, len, offset
    );
    let mut proc = process();
    proc.vm.check_read_array(base, len)?;

    let slice = unsafe { slice::from_raw_parts(base, len) };
    let len = proc.get_file(fd)?.write_at(offset, slice)?;
    Ok(len)
}

pub fn sys_ppoll(ufds: *mut PollFd, nfds: usize, timeout: *const TimeSpec) -> SysResult {
    let proc = process();
    let timeout_msecs = if timeout.is_null() {
        1 << 31 // infinity
    } else {
        proc.vm.check_read_ptr(timeout)?;
        unsafe { (*timeout).to_msec() }
    };
    drop(proc);

    sys_poll(ufds, nfds, timeout_msecs as usize)
}

pub fn sys_poll(ufds: *mut PollFd, nfds: usize, timeout_msecs: usize) -> SysResult {
    let proc = process();
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!(
            "poll: ufds: {:?}, nfds: {}, timeout_msecs: {:#x}",
            ufds, nfds, timeout_msecs
        );
    }
    proc.vm.check_write_array(ufds, nfds)?;

    let polls = unsafe { slice::from_raw_parts_mut(ufds, nfds) };
    for poll in polls.iter() {
        if proc.files.get(&(poll.fd as usize)).is_none() {
            return Err(SysError::EINVAL);
        }
    }
    drop(proc);

    let begin_time_ms = crate::trap::uptime_msec();
    loop {
        use PollEvents as PE;
        let proc = process();
        let mut events = 0;
        for poll in polls.iter_mut() {
            poll.revents = PE::empty();
            if let Some(file_like) = proc.files.get(&(poll.fd as usize)) {
                let status = file_like.poll()?;
                if status.error {
                    poll.revents |= PE::HUP;
                    events += 1;
                }
                if status.read && poll.events.contains(PE::IN) {
                    poll.revents |= PE::IN;
                    events += 1;
                }
                if status.write && poll.events.contains(PE::OUT) {
                    poll.revents |= PE::OUT;
                    events += 1;
                }
            } else {
                poll.revents |= PE::ERR;
                events += 1;
            }
        }
        drop(proc);

        if events > 0 {
            return Ok(events);
        }

        let current_time_ms = crate::trap::uptime_msec();
        if timeout_msecs < (1 << 31) && current_time_ms - begin_time_ms > timeout_msecs {
            return Ok(0);
        }

        Condvar::wait_any(&[&STDIN.pushed, &(*SOCKET_ACTIVITY)]);
    }
}

pub fn sys_select(
    nfds: usize,
    read: *mut u32,
    write: *mut u32,
    err: *mut u32,
    timeout: *const TimeVal,
) -> SysResult {
    info!(
        "select: nfds: {}, read: {:?}, write: {:?}, err: {:?}, timeout: {:?}",
        nfds, read, write, err, timeout
    );

    let proc = process();
    let mut read_fds = FdSet::new(&proc.vm, read, nfds)?;
    let mut write_fds = FdSet::new(&proc.vm, write, nfds)?;
    let mut err_fds = FdSet::new(&proc.vm, err, nfds)?;
    let timeout_msecs = if timeout as usize != 0 {
        proc.vm.check_read_ptr(timeout)?;
        unsafe { *timeout }.to_msec()
    } else {
        // infinity
        1 << 31
    };
    drop(proc);

    let begin_time_ms = crate::trap::uptime_msec();
    loop {
        let proc = process();
        let mut events = 0;
        for (&fd, file_like) in proc.files.iter() {
            if fd >= nfds {
                continue;
            }
            let status = file_like.poll()?;
            if status.error && err_fds.contains(fd) {
                err_fds.set(fd);
                events += 1;
            }
            if status.read && read_fds.contains(fd) {
                read_fds.set(fd);
                events += 1;
            }
            if status.write && write_fds.contains(fd) {
                write_fds.set(fd);
                events += 1;
            }
        }
        drop(proc);

        if events > 0 {
            return Ok(events);
        }

        if timeout_msecs == 0 {
            // no timeout, return now;
            return Ok(0);
        }

        let current_time_ms = crate::trap::uptime_msec();
        // infinity check
        if timeout_msecs < (1 << 31) && current_time_ms - begin_time_ms > timeout_msecs as usize {
            return Ok(0);
        }

        Condvar::wait_any(&[&STDIN.pushed, &(*SOCKET_ACTIVITY)]);
    }
}

pub fn sys_readv(fd: usize, iov_ptr: *const IoVec, iov_count: usize) -> SysResult {
    info!(
        "readv: fd: {}, iov: {:?}, count: {}",
        fd, iov_ptr, iov_count
    );
    let mut proc = process();
    let mut iovs = IoVecs::check_and_new(iov_ptr, iov_count, &proc.vm, true)?;

    // read all data to a buf
    let file_like = proc.get_file_like(fd)?;
    let mut buf = iovs.new_buf(true);
    let len = file_like.read(buf.as_mut_slice())?;
    // copy data to user
    iovs.write_all_from_slice(&buf[..len]);
    Ok(len)
}

pub fn sys_writev(fd: usize, iov_ptr: *const IoVec, iov_count: usize) -> SysResult {
    let mut proc = process();
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!(
            "writev: fd: {}, iov: {:?}, count: {}",
            fd, iov_ptr, iov_count
        );
    }
    let iovs = IoVecs::check_and_new(iov_ptr, iov_count, &proc.vm, false)?;

    let buf = iovs.read_all_to_vec();
    let len = buf.len();

    let file_like = proc.get_file_like(fd)?;
    let len = file_like.write(buf.as_slice())?;
    Ok(len)
}

pub fn sys_open(path: *const u8, flags: usize, mode: usize) -> SysResult {
    sys_openat(AT_FDCWD, path, flags, mode)
}

pub fn sys_openat(dir_fd: usize, path: *const u8, flags: usize, mode: usize) -> SysResult {
    let mut proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    let flags = OpenFlags::from_bits_truncate(flags);
    info!(
        "openat: dir_fd: {}, path: {:?}, flags: {:?}, mode: {:#o}",
        dir_fd as isize, path, flags, mode
    );

    let inode = if flags.contains(OpenFlags::CREATE) {
        let (dir_path, file_name) = split_path(&path);
        // relative to cwd
        let dir_inode = proc.lookup_inode_at(dir_fd, dir_path)?;
        match dir_inode.find(file_name) {
            Ok(file_inode) => {
                if flags.contains(OpenFlags::EXCLUSIVE) {
                    return Err(SysError::EEXIST);
                }
                file_inode
            }
            Err(FsError::EntryNotFound) => {
                dir_inode.create(file_name, FileType::File, mode as u32)?
            }
            Err(e) => return Err(SysError::from(e)),
        }
    } else {
        proc.lookup_inode_at(dir_fd, &path)?
    };

    let fd = proc.get_free_fd();

    let file = FileHandle::new(inode, flags.to_options());
    proc.files.insert(fd, FileLike::File(file));
    Ok(fd)
}

pub fn sys_close(fd: usize) -> SysResult {
    info!("close: fd: {:?}", fd);
    let mut proc = process();
    proc.files.remove(&fd).ok_or(SysError::EBADF)?;
    Ok(0)
}

pub fn sys_access(path: *const u8, mode: usize) -> SysResult {
    sys_faccessat(AT_FDCWD, path, mode, 0)
}

pub fn sys_faccessat(dirfd: usize, path: *const u8, mode: usize, flags: usize) -> SysResult {
    // TODO: check permissions based on uid/gid
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    let flags = AtFlags::from_bits_truncate(flags);
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!(
            "faccessat: dirfd: {}, path: {:?}, mode: {:#o}, flags: {:?}",
            dirfd as isize, path, mode, flags
        );
    }
    let inode = proc.lookup_inode_at(dirfd, &path)?;
    Ok(0)
}

pub fn sys_getcwd(buf: *mut u8, len: usize) -> SysResult {
    let proc = process();
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!("getcwd: buf: {:?}, len: {:#x}", buf, len);
    }
    proc.vm.check_write_array(buf, len)?;
    if proc.cwd.len() + 1 > len {
        return Err(SysError::ERANGE);
    }
    unsafe { util::write_cstr(buf, &proc.cwd) }
    Ok(buf as usize)
}

pub fn sys_lstat(path: *const u8, stat_ptr: *mut Stat) -> SysResult {
    warn!("lstat is partial implemented as stat");
    sys_stat(path, stat_ptr)
}

pub fn sys_fstat(fd: usize, stat_ptr: *mut Stat) -> SysResult {
    info!("fstat: fd: {}, stat_ptr: {:?}", fd, stat_ptr);
    let mut proc = process();
    proc.vm.check_write_ptr(stat_ptr)?;
    let file = proc.get_file(fd)?;
    let stat = Stat::from(file.metadata()?);
    unsafe {
        stat_ptr.write(stat);
    }
    Ok(0)
}

pub fn sys_fstatat(dirfd: usize, path: *const u8, stat_ptr: *mut Stat, flags: usize) -> SysResult {
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    proc.vm.check_write_ptr(stat_ptr)?;
    let flags = AtFlags::from_bits_truncate(flags);
    info!(
        "fstatat: dirfd: {}, path: {:?}, stat_ptr: {:?}, flags: {:?}",
        dirfd as isize, path, stat_ptr, flags
    );

    let inode = proc.lookup_inode_at(dirfd, &path)?;
    let stat = Stat::from(inode.metadata()?);
    unsafe {
        stat_ptr.write(stat);
    }
    Ok(0)
}

pub fn sys_stat(path: *const u8, stat_ptr: *mut Stat) -> SysResult {
    sys_fstatat(AT_FDCWD, path, stat_ptr, 0)
}

pub fn sys_readlink(path: *const u8, base: *mut u8, len: usize) -> SysResult {
    sys_readlinkat(AT_FDCWD, path, base, len)
}

pub fn sys_readlinkat(dirfd: usize, path: *const u8, base: *mut u8, len: usize) -> SysResult {
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    proc.vm.check_write_array(base, len)?;
    info!("readlink: path: {:?}, base: {:?}, len: {}", path, base, len);

    let inode = proc.lookup_inode_at(dirfd, &path)?;
    if inode.metadata()?.type_ == FileType::SymLink {
        // TODO: recursive link resolution and loop detection
        let mut slice = unsafe { slice::from_raw_parts_mut(base, len) };
        let len = inode.read_at(0, &mut slice)?;
        Ok(len)
    } else {
        Err(SysError::EINVAL)
    }
}

pub fn sys_lseek(fd: usize, offset: i64, whence: u8) -> SysResult {
    let pos = match whence {
        SEEK_SET => SeekFrom::Start(offset as u64),
        SEEK_END => SeekFrom::End(offset),
        SEEK_CUR => SeekFrom::Current(offset),
        _ => return Err(SysError::EINVAL),
    };
    info!("lseek: fd: {}, pos: {:?}", fd, pos);

    let mut proc = process();
    let file = proc.get_file(fd)?;
    let offset = file.seek(pos)?;
    Ok(offset as usize)
}

pub fn sys_fsync(fd: usize) -> SysResult {
    info!("fsync: fd: {}", fd);
    process().get_file(fd)?.sync_all()?;
    Ok(0)
}

pub fn sys_fdatasync(fd: usize) -> SysResult {
    info!("fdatasync: fd: {}", fd);
    process().get_file(fd)?.sync_data()?;
    Ok(0)
}

pub fn sys_truncate(path: *const u8, len: usize) -> SysResult {
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    info!("truncate: path: {:?}, len: {}", path, len);
    proc.lookup_inode(&path)?.resize(len)?;
    Ok(0)
}

pub fn sys_ftruncate(fd: usize, len: usize) -> SysResult {
    info!("ftruncate: fd: {}, len: {}", fd, len);
    process().get_file(fd)?.set_len(len as u64)?;
    Ok(0)
}

pub fn sys_getdents64(fd: usize, buf: *mut LinuxDirent64, buf_size: usize) -> SysResult {
    info!(
        "getdents64: fd: {}, ptr: {:?}, buf_size: {}",
        fd, buf, buf_size
    );
    let mut proc = process();
    proc.vm.check_write_array(buf as *mut u8, buf_size)?;
    let file = proc.get_file(fd)?;
    let info = file.metadata()?;
    if info.type_ != FileType::Dir {
        return Err(SysError::ENOTDIR);
    }
    let mut writer = unsafe { DirentBufWriter::new(buf, buf_size) };
    loop {
        let name = match file.read_entry() {
            Err(FsError::EntryNotFound) => break,
            r => r,
        }?;
        // TODO: get ino from dirent
        let ok = writer.try_write(0, DirentType::from_type(&info.type_).bits(), &name);
        if !ok {
            break;
        }
    }
    Ok(writer.written_size)
}

pub fn sys_dup2(fd1: usize, fd2: usize) -> SysResult {
    info!("dup2: from {} to {}", fd1, fd2);
    let mut proc = process();
    // close fd2 first if it is opened
    proc.files.remove(&fd2);

    let file_like = proc.get_file_like(fd1)?.clone();
    proc.files.insert(fd2, file_like);
    Ok(fd2)
}

pub fn sys_ioctl(fd: usize, request: usize, arg1: usize, arg2: usize, arg3: usize) -> SysResult {
    info!(
        "ioctl: fd: {}, request: {}, args: {} {} {}",
        fd, request, arg1, arg2, arg3
    );
    let mut proc = process();
    let file_like = proc.get_file_like(fd)?;
    file_like.ioctl(request, arg1, arg2, arg3)
}

pub fn sys_chdir(path: *const u8) -> SysResult {
    let mut proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    if !proc.pid.is_init() {
        // we trust pid 0 process
        info!("chdir: path: {:?}", path);
    }

    let inode = proc.lookup_inode(&path)?;
    let info = inode.metadata()?;
    if info.type_ != FileType::Dir {
        return Err(SysError::ENOTDIR);
    }

    // BUGFIX: '..' and '.'
    if path.len() > 0 {
        let cwd = match path.as_bytes()[0] {
            b'/' => String::from("/"),
            _ => proc.cwd.clone(),
        };
        let mut cwd_vec: Vec<_> = cwd.split("/").filter(|&x| x != "").collect();
        let path_split = path.split("/").filter(|&x| x != "");
        for seg in path_split {
            if seg == ".." {
                cwd_vec.pop();
            } else if seg == "." {
                // nothing to do here.
            } else {
                cwd_vec.push(seg);
            }
        }
        proc.cwd = String::from("");
        for seg in cwd_vec {
            proc.cwd.push_str("/");
            proc.cwd.push_str(seg);
        }
        if proc.cwd == "" {
            proc.cwd = String::from("/");
        }
    }
    Ok(0)
}

pub fn sys_rename(oldpath: *const u8, newpath: *const u8) -> SysResult {
    sys_renameat(AT_FDCWD, oldpath, AT_FDCWD, newpath)
}

pub fn sys_renameat(
    olddirfd: usize,
    oldpath: *const u8,
    newdirfd: usize,
    newpath: *const u8,
) -> SysResult {
    let mut proc = process();
    let oldpath = unsafe { proc.vm.check_and_clone_cstr(oldpath)? };
    let newpath = unsafe { proc.vm.check_and_clone_cstr(newpath)? };
    info!(
        "renameat: olddirfd: {}, oldpath: {:?}, newdirfd: {}, newpath: {:?}",
        olddirfd as isize, oldpath, newdirfd as isize, newpath
    );

    let (old_dir_path, old_file_name) = split_path(&oldpath);
    let (new_dir_path, new_file_name) = split_path(&newpath);
    let old_dir_inode = proc.lookup_inode_at(olddirfd, old_dir_path)?;
    let new_dir_inode = proc.lookup_inode_at(newdirfd, new_dir_path)?;
    old_dir_inode.move_(old_file_name, &new_dir_inode, new_file_name)?;
    Ok(0)
}

pub fn sys_mkdir(path: *const u8, mode: usize) -> SysResult {
    sys_mkdirat(AT_FDCWD, path, mode)
}

pub fn sys_mkdirat(dirfd: usize, path: *const u8, mode: usize) -> SysResult {
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    // TODO: check pathname
    info!(
        "mkdirat: dirfd: {}, path: {:?}, mode: {:#o}",
        dirfd as isize, path, mode
    );

    let (dir_path, file_name) = split_path(&path);
    let inode = proc.lookup_inode_at(dirfd, dir_path)?;
    if inode.find(file_name).is_ok() {
        return Err(SysError::EEXIST);
    }
    inode.create(file_name, FileType::Dir, mode as u32)?;
    Ok(0)
}

pub fn sys_rmdir(path: *const u8) -> SysResult {
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    info!("rmdir: path: {:?}", path);

    let (dir_path, file_name) = split_path(&path);
    let dir_inode = proc.lookup_inode(dir_path)?;
    let file_inode = dir_inode.find(file_name)?;
    if file_inode.metadata()?.type_ != FileType::Dir {
        return Err(SysError::ENOTDIR);
    }
    dir_inode.unlink(file_name)?;
    Ok(0)
}

pub fn sys_link(oldpath: *const u8, newpath: *const u8) -> SysResult {
    sys_linkat(AT_FDCWD, oldpath, AT_FDCWD, newpath, 0)
}

pub fn sys_linkat(
    olddirfd: usize,
    oldpath: *const u8,
    newdirfd: usize,
    newpath: *const u8,
    flags: usize,
) -> SysResult {
    let proc = process();
    let oldpath = unsafe { proc.vm.check_and_clone_cstr(oldpath)? };
    let newpath = unsafe { proc.vm.check_and_clone_cstr(newpath)? };
    let flags = AtFlags::from_bits_truncate(flags);
    info!(
        "linkat: olddirfd: {}, oldpath: {:?}, newdirfd: {}, newpath: {:?}, flags: {:?}",
        olddirfd as isize, oldpath, newdirfd as isize, newpath, flags
    );

    let (new_dir_path, new_file_name) = split_path(&newpath);
    let inode = proc.lookup_inode_at(olddirfd, &oldpath)?;
    let new_dir_inode = proc.lookup_inode_at(newdirfd, new_dir_path)?;
    new_dir_inode.link(new_file_name, &inode)?;
    Ok(0)
}

pub fn sys_unlink(path: *const u8) -> SysResult {
    sys_unlinkat(AT_FDCWD, path, 0)
}

pub fn sys_unlinkat(dirfd: usize, path: *const u8, flags: usize) -> SysResult {
    let proc = process();
    let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
    let flags = AtFlags::from_bits_truncate(flags);
    info!(
        "unlinkat: dirfd: {}, path: {:?}, flags: {:?}",
        dirfd as isize, path, flags
    );

    let (dir_path, file_name) = split_path(&path);
    let dir_inode = proc.lookup_inode_at(dirfd, dir_path)?;
    let file_inode = dir_inode.find(file_name)?;
    if file_inode.metadata()?.type_ == FileType::Dir {
        return Err(SysError::EISDIR);
    }
    dir_inode.unlink(file_name)?;
    Ok(0)
}

pub fn sys_pipe(fds: *mut u32) -> SysResult {
    info!("pipe: fds: {:?}", fds);

    let mut proc = process();
    proc.vm.check_write_array(fds, 2)?;
    let (read, write) = Pipe::create_pair();

    let read_fd = proc.get_free_fd();
    proc.files.insert(
        read_fd,
        FileLike::File(FileHandle::new(
            Arc::new(read),
            OpenOptions {
                read: true,
                write: false,
                append: false,
            },
        )),
    );

    let write_fd = proc.get_free_fd();
    proc.files.insert(
        write_fd,
        FileLike::File(FileHandle::new(
            Arc::new(write),
            OpenOptions {
                read: false,
                write: true,
                append: false,
            },
        )),
    );

    unsafe {
        *fds = read_fd as u32;
        *(fds.add(1)) = write_fd as u32;
    }

    info!("pipe: created rfd: {} wfd: {}", read_fd, write_fd);

    Ok(0)
}

pub fn sys_sync() -> SysResult {
    ROOT_INODE.fs().sync()?;
    Ok(0)
}

pub fn sys_sendfile(out_fd: usize, in_fd: usize, offset: *mut usize, count: usize) -> SysResult {
    info!(
        "sendfile: out: {}, in: {}, offset: {:?}, count: {}",
        out_fd, in_fd, offset, count
    );
    let proc = process();
    // We know it's save, pacify the borrow checker
    let proc_cell = UnsafeCell::new(proc);
    let proc_in = unsafe { &mut *proc_cell.get() };
    let proc_out = unsafe { &mut *proc_cell.get() };
    //let in_file: &mut FileHandle = unsafe { &mut *UnsafeCell::new(proc.get_file(in_fd)?).get() };
    //let out_file: &mut FileHandle = unsafe { &mut *UnsafeCell::new(proc.get_file(out_fd)?).get() };
    let in_file = proc_in.get_file(in_fd)?;
    let out_file = proc_out.get_file(out_fd)?;
    let mut buffer = [0u8; 1024];
    if offset.is_null() {
        // read from current file offset
        let mut bytes_read = 0;
        while bytes_read < count {
            let len = min(buffer.len(), count - bytes_read);
            let read_len = in_file.read(&mut buffer[..len])?;
            if read_len == 0 {
                break;
            }
            bytes_read += read_len;
            let mut bytes_written = 0;
            while bytes_written < read_len {
                let write_len = out_file.write(&buffer[bytes_written..])?;
                if write_len == 0 {
                    return Err(SysError::EBADF);
                }
                bytes_written += write_len;
            }
        }
        return Ok(bytes_read);
    } else {
        let proc_mem = unsafe { &mut *proc_cell.get() };
        proc_mem.vm.check_read_ptr(offset)?;
        let mut read_offset = unsafe { *offset };
        // read from specified offset and write new offset back
        let mut bytes_read = 0;
        while bytes_read < count {
            let len = min(buffer.len(), count - bytes_read);
            let read_len = in_file.read_at(read_offset, &mut buffer[..len])?;
            if read_len == 0 {
                break;
            }
            bytes_read += read_len;
            read_offset += read_len;
            let mut bytes_written = 0;
            while bytes_written < read_len {
                let write_len = out_file.write(&buffer[bytes_written..])?;
                if write_len == 0 {
                    return Err(SysError::EBADF);
                }
                bytes_written += write_len;
            }
        }
        unsafe {
            *offset = read_offset;
        }
        return Ok(bytes_read);
    }
}

impl Process {
    pub fn get_file_like(&mut self, fd: usize) -> Result<&mut FileLike, SysError> {
        self.files.get_mut(&fd).ok_or(SysError::EBADF)
    }
    pub fn get_file(&mut self, fd: usize) -> Result<&mut FileHandle, SysError> {
        match self.get_file_like(fd)? {
            FileLike::File(file) => Ok(file),
            _ => Err(SysError::EBADF),
        }
    }
    /// Lookup INode from the process.
    ///
    /// - If `path` is relative, then it is interpreted relative to the directory
    ///   referred to by the file descriptor `dirfd`.
    ///
    /// - If the `dirfd` is the special value `AT_FDCWD`, then the directory is
    ///   current working directory of the process.
    ///
    /// - If `path` is absolute, then `dirfd` is ignored.
    ///
    /// - If `follow` is true, then dereference `path` if it is a symbolic link.
    pub fn lookup_inode_at(
        &self,
        dirfd: usize,
        path: &str,
        //        follow: bool,
    ) -> Result<Arc<INode>, SysError> {
        let follow = true;
        debug!(
            "lookup_inode_at: dirfd: {:?}, cwd: {:?}, path: {:?}, follow: {:?}",
            dirfd as isize, self.cwd, path, follow
        );
        let follow_max_depth = if follow { FOLLOW_MAX_DEPTH } else { 0 };
        if dirfd == AT_FDCWD {
            Ok(ROOT_INODE
                .lookup(&self.cwd)?
                .lookup_follow(path, follow_max_depth)?)
        } else {
            let file = match self.files.get(&dirfd).ok_or(SysError::EBADF)? {
                FileLike::File(file) => file,
                _ => return Err(SysError::EBADF),
            };
            Ok(file.lookup_follow(path, follow_max_depth)?)
        }
    }

    pub fn lookup_inode(&self, path: &str) -> Result<Arc<INode>, SysError> {
        self.lookup_inode_at(AT_FDCWD, path)
    }
}

/// Split a `path` str to `(base_path, file_name)`
fn split_path(path: &str) -> (&str, &str) {
    let mut split = path.trim_end_matches('/').rsplitn(2, '/');
    let file_name = split.next().unwrap();
    let mut dir_path = split.next().unwrap_or(".");
    if dir_path == "" {
        dir_path = "/";
    }
    (dir_path, file_name)
}

impl From<FsError> for SysError {
    fn from(error: FsError) -> Self {
        match error {
            FsError::NotSupported => SysError::ENOSYS,
            FsError::NotFile => SysError::EISDIR,
            FsError::IsDir => SysError::EISDIR,
            FsError::NotDir => SysError::ENOTDIR,
            FsError::EntryNotFound => SysError::ENOENT,
            FsError::EntryExist => SysError::EEXIST,
            FsError::NotSameFs => SysError::EXDEV,
            FsError::InvalidParam => SysError::EINVAL,
            FsError::NoDeviceSpace => SysError::ENOMEM,
            FsError::DirRemoved => SysError::ENOENT,
            FsError::DirNotEmpty => SysError::ENOTEMPTY,
            FsError::WrongFs => SysError::EINVAL,
            FsError::DeviceError => SysError::EIO,
        }
    }
}

bitflags! {
    struct AtFlags: usize {
        const EMPTY_PATH = 0x1000;
        const SYMLINK_NOFOLLOW = 0x100;
    }
}

bitflags! {
    struct OpenFlags: usize {
        /// read only
        const RDONLY = 0;
        /// write only
        const WRONLY = 1;
        /// read write
        const RDWR = 2;
        /// create file if it does not exist
        const CREATE = 1 << 6;
        /// error if CREATE and the file exists
        const EXCLUSIVE = 1 << 7;
        /// truncate file upon open
        const TRUNCATE = 1 << 9;
        /// append on each write
        const APPEND = 1 << 10;
    }
}

impl OpenFlags {
    fn readable(&self) -> bool {
        let b = self.bits() & 0b11;
        b == OpenFlags::RDONLY.bits() || b == OpenFlags::RDWR.bits()
    }
    fn writable(&self) -> bool {
        let b = self.bits() & 0b11;
        b == OpenFlags::WRONLY.bits() || b == OpenFlags::RDWR.bits()
    }
    fn to_options(&self) -> OpenOptions {
        OpenOptions {
            read: self.readable(),
            write: self.writable(),
            append: self.contains(OpenFlags::APPEND),
        }
    }
}

#[derive(Debug)]
#[repr(packed)] // Don't use 'C'. Or its size will align up to 8 bytes.
pub struct LinuxDirent64 {
    /// Inode number
    ino: u64,
    /// Offset to next structure
    offset: u64,
    /// Size of this dirent
    reclen: u16,
    /// File type
    type_: u8,
    /// Filename (null-terminated)
    name: [u8; 0],
}

struct DirentBufWriter {
    ptr: *mut LinuxDirent64,
    rest_size: usize,
    written_size: usize,
}

impl DirentBufWriter {
    unsafe fn new(buf: *mut LinuxDirent64, size: usize) -> Self {
        DirentBufWriter {
            ptr: buf,
            rest_size: size,
            written_size: 0,
        }
    }
    fn try_write(&mut self, inode: u64, type_: u8, name: &str) -> bool {
        let len = ::core::mem::size_of::<LinuxDirent64>() + name.len() + 1;
        let len = (len + 7) / 8 * 8; // align up
        if self.rest_size < len {
            return false;
        }
        let dent = LinuxDirent64 {
            ino: inode,
            offset: 0,
            reclen: len as u16,
            type_,
            name: [],
        };
        unsafe {
            self.ptr.write(dent);
            let name_ptr = self.ptr.add(1) as _;
            util::write_cstr(name_ptr, name);
            self.ptr = (self.ptr as *const u8).add(len) as _;
        }
        self.rest_size -= len;
        self.written_size += len;
        true
    }
}

bitflags! {
    pub struct DirentType: u8 {
        const DT_UNKNOWN  = 0;
        /// FIFO (named pipe)
        const DT_FIFO = 1;
        /// Character device
        const DT_CHR  = 2;
        /// Directory
        const DT_DIR  = 4;
        /// Block device
        const DT_BLK = 6;
        /// Regular file
        const DT_REG = 8;
        /// Symbolic link
        const DT_LNK = 10;
        /// UNIX domain socket
        const DT_SOCK  = 12;
        /// ???
        const DT_WHT = 14;
    }
}

impl DirentType {
    fn from_type(type_: &FileType) -> Self {
        match type_ {
            FileType::File => Self::DT_REG,
            FileType::Dir => Self::DT_DIR,
            FileType::SymLink => Self::DT_LNK,
            FileType::CharDevice => Self::DT_CHR,
            FileType::BlockDevice => Self::DT_BLK,
            FileType::Socket => Self::DT_SOCK,
            FileType::NamedPipe => Self::DT_FIFO,
        }
    }
}

#[cfg(target_arch = "x86_64")]
#[repr(C)]
#[derive(Debug)]
pub struct Stat {
    /// ID of device containing file
    dev: u64,
    /// inode number
    ino: u64,
    /// number of hard links
    nlink: u64,

    /// file type and mode
    mode: StatMode,
    /// user ID of owner
    uid: u32,
    /// group ID of owner
    gid: u32,
    /// padding
    _pad0: u32,
    /// device ID (if special file)
    rdev: u64,
    /// total size, in bytes
    size: u64,
    /// blocksize for filesystem I/O
    blksize: u64,
    /// number of 512B blocks allocated
    blocks: u64,

    /// last access time
    atime: Timespec,
    /// last modification time
    mtime: Timespec,
    /// last status change time
    ctime: Timespec,
}

#[cfg(not(target_arch = "x86_64"))]
#[repr(C)]
#[derive(Debug)]
pub struct Stat {
    /// ID of device containing file
    dev: u64,
    /// inode number
    ino: u64,
    /// file type and mode
    mode: StatMode,
    /// number of hard links
    nlink: u32,

    /// user ID of owner
    uid: u32,
    /// group ID of owner
    gid: u32,
    /// device ID (if special file)
    rdev: u64,
    /// padding
    __pad: u64,
    /// total size, in bytes
    size: u64,
    /// blocksize for filesystem I/O
    blksize: u32,
    /// padding
    __pad2: u32,
    /// number of 512B blocks allocated
    blocks: u64,

    /// last access time
    atime: Timespec,
    /// last modification time
    mtime: Timespec,
    /// last status change time
    ctime: Timespec,
}

bitflags! {
    pub struct StatMode: u32 {
        const NULL  = 0;
        /// Type
        const TYPE_MASK = 0o170000;
        /// FIFO
        const FIFO  = 0o010000;
        /// character device
        const CHAR  = 0o020000;
        /// directory
        const DIR   = 0o040000;
        /// block device
        const BLOCK = 0o060000;
        /// ordinary regular file
        const FILE  = 0o100000;
        /// symbolic link
        const LINK  = 0o120000;
        /// socket
        const SOCKET = 0o140000;

        /// Set-user-ID on execution.
        const SET_UID = 0o4000;
        /// Set-group-ID on execution.
        const SET_GID = 0o2000;

        /// Read, write, execute/search by owner.
        const OWNER_MASK = 0o700;
        /// Read permission, owner.
        const OWNER_READ = 0o400;
        /// Write permission, owner.
        const OWNER_WRITE = 0o200;
        /// Execute/search permission, owner.
        const OWNER_EXEC = 0o100;

        /// Read, write, execute/search by group.
        const GROUP_MASK = 0o70;
        /// Read permission, group.
        const GROUP_READ = 0o40;
        /// Write permission, group.
        const GROUP_WRITE = 0o20;
        /// Execute/search permission, group.
        const GROUP_EXEC = 0o10;

        /// Read, write, execute/search by others.
        const OTHER_MASK = 0o7;
        /// Read permission, others.
        const OTHER_READ = 0o4;
        /// Write permission, others.
        const OTHER_WRITE = 0o2;
        /// Execute/search permission, others.
        const OTHER_EXEC = 0o1;
    }
}

impl StatMode {
    fn from_type_mode(type_: FileType, mode: u16) -> Self {
        let type_ = match type_ {
            FileType::File => StatMode::FILE,
            FileType::Dir => StatMode::DIR,
            FileType::SymLink => StatMode::LINK,
            FileType::CharDevice => StatMode::CHAR,
            FileType::BlockDevice => StatMode::BLOCK,
            FileType::Socket => StatMode::SOCKET,
            FileType::NamedPipe => StatMode::FIFO,
        };
        let mode = StatMode::from_bits_truncate(mode as u32);
        type_ | mode
    }
}

impl From<Metadata> for Stat {
    #[cfg(target_arch = "x86_64")]
    fn from(info: Metadata) -> Self {
        Stat {
            dev: info.dev as u64,
            ino: info.inode as u64,
            mode: StatMode::from_type_mode(info.type_, info.mode as u16),
            nlink: info.nlinks as u64,
            uid: info.uid as u32,
            gid: info.gid as u32,
            rdev: 0,
            size: info.size as u64,
            blksize: info.blk_size as u64,
            blocks: info.blocks as u64,
            atime: info.atime,
            mtime: info.mtime,
            ctime: info.ctime,
            _pad0: 0,
        }
    }

    #[cfg(not(target_arch = "x86_64"))]
    fn from(info: Metadata) -> Self {
        Stat {
            dev: info.dev as u64,
            ino: info.inode as u64,
            mode: StatMode::from_type_mode(info.type_, info.mode as u16),
            nlink: info.nlinks as u32,
            uid: info.uid as u32,
            gid: info.gid as u32,
            rdev: 0,
            size: info.size as u64,
            blksize: info.blk_size as u32,
            blocks: info.blocks as u64,
            atime: info.atime,
            mtime: info.mtime,
            ctime: info.ctime,
            __pad: 0,
            __pad2: 0,
        }
    }
}

const SEEK_SET: u8 = 0;
const SEEK_CUR: u8 = 1;
const SEEK_END: u8 = 2;

#[derive(Debug, Copy, Clone)]
#[repr(C)]
pub struct IoVec {
    /// Starting address
    base: *mut u8,
    /// Number of bytes to transfer
    len: usize,
}

/// A valid IoVecs request from user
#[derive(Debug)]
pub struct IoVecs(Vec<&'static mut [u8]>);

impl IoVecs {
    pub fn check_and_new(
        iov_ptr: *const IoVec,
        iov_count: usize,
        vm: &MemorySet,
        readv: bool,
    ) -> Result<Self, SysError> {
        vm.check_read_array(iov_ptr, iov_count)?;
        let iovs = unsafe { slice::from_raw_parts(iov_ptr, iov_count) }.to_vec();
        // check all bufs in iov
        for iov in iovs.iter() {
            if iov.len > 0 {
                // skip empty iov
                if readv {
                    vm.check_write_array(iov.base, iov.len)?;
                } else {
                    vm.check_read_array(iov.base, iov.len)?;
                }
            }
        }
        let slices = iovs
            .iter()
            .map(|iov| unsafe { slice::from_raw_parts_mut(iov.base, iov.len) })
            .collect();
        Ok(IoVecs(slices))
    }

    pub fn read_all_to_vec(&self) -> Vec<u8> {
        let mut buf = self.new_buf(false);
        for slice in self.0.iter() {
            buf.extend(slice.iter());
        }
        buf
    }

    pub fn write_all_from_slice(&mut self, buf: &[u8]) {
        let mut copied_len = 0;
        for slice in self.0.iter_mut() {
            let copy_len = min(slice.len(), buf.len() - copied_len);
            if copy_len == 0 {
                continue;
            }

            slice[..copy_len].copy_from_slice(&buf[copied_len..copied_len + copy_len]);
            copied_len += copy_len;
        }
    }

    /// Create a new Vec buffer from IoVecs
    /// For readv:  `set_len` is true,  Vec.len = total_len.
    /// For writev: `set_len` is false, Vec.cap = total_len.
    pub fn new_buf(&self, set_len: bool) -> Vec<u8> {
        let total_len = self.0.iter().map(|slice| slice.len()).sum::<usize>();
        info!("{}", total_len);
        let mut buf = Vec::with_capacity(total_len);
        if set_len {
            unsafe {
                buf.set_len(total_len);
            }
        }
        buf
    }
}

#[repr(C)]
pub struct PollFd {
    fd: u32,
    events: PollEvents,
    revents: PollEvents,
}

bitflags! {
    pub struct PollEvents: u16 {
        /// There is data to read.
        const IN = 0x0001;
        /// Writing is now possible.
        const OUT = 0x0004;
        /// Error condition (return only)
        const ERR = 0x0008;
        /// Hang up (return only)
        const HUP = 0x0010;
        /// Invalid request: fd not open (return only)
        const INVAL = 0x0020;
    }
}

const FD_PER_ITEM: usize = 8 * size_of::<u32>();
const MAX_FDSET_SIZE: usize = 1024 / FD_PER_ITEM;

struct FdSet {
    bitset: &'static mut BitSlice<LittleEndian, u32>,
    origin: BitVec<LittleEndian, u32>,
}

impl FdSet {
    /// Initialize a `FdSet` from pointer and number of fds
    /// Check if the array is large enough
    fn new(vm: &MemorySet, addr: *mut u32, nfds: usize) -> Result<FdSet, SysError> {
        if addr.is_null() {
            Ok(FdSet {
                bitset: BitSlice::empty_mut(),
                origin: BitVec::new(),
            })
        } else {
            let len = (nfds + FD_PER_ITEM - 1) / FD_PER_ITEM;
            vm.check_write_array(addr, len)?;
            if len > MAX_FDSET_SIZE {
                return Err(SysError::EINVAL);
            }
            let slice = unsafe { slice::from_raw_parts_mut(addr, len) };
            let bitset: &'static mut BitSlice<LittleEndian, u32> = slice.into();

            // save the fdset, and clear it
            use alloc::prelude::ToOwned;
            let origin = bitset.to_owned();
            bitset.set_all(false);
            Ok(FdSet { bitset, origin })
        }
    }

    /// Try to set fd in `FdSet`
    /// Return true when `FdSet` is valid, and false when `FdSet` is bad (i.e. null pointer)
    /// Fd should be less than nfds
    fn set(&mut self, fd: usize) -> bool {
        if self.bitset.is_empty() {
            return false;
        }
        self.bitset.set(fd, true);
        true
    }

    /// Check to see whether `fd` is in original `FdSet`
    /// Fd should be less than nfds
    fn contains(&self, fd: usize) -> bool {
        self.origin[fd]
    }
}

const AT_FDCWD: usize = -100isize as usize;