//! Linux `statx`.

use crate::fd::AsFd;

use crate::fs::AtFlags;

use crate::{backend, io, path};

use backend::c;

use bitflags::bitflags;

#[cfg(feature = "linux_4_11")]

use backend::fs::syscalls::statx as _statx;

#[cfg(not(feature = "linux_4_11"))]

use compat::statx as _statx;

/// `struct statx` for use with [`statx`].

#[repr(C)]

#[derive(Debug, Copy, Clone)]

#[allow(missing_docs)]

#[non_exhaustive]

pub struct Statx {

    pub stx_mask: u32,

    pub stx_blksize: u32,

    pub stx_attributes: StatxAttributes,

    pub stx_nlink: u32,

    pub stx_uid: u32,

    pub stx_gid: u32,

    pub stx_mode: u16,

    pub(crate) __spare0: [u16; 1],

    pub stx_ino: u64,

    pub stx_size: u64,

    pub stx_blocks: u64,

    pub stx_attributes_mask: StatxAttributes,

    pub stx_atime: StatxTimestamp,

    pub stx_btime: StatxTimestamp,

    pub stx_ctime: StatxTimestamp,

    pub stx_mtime: StatxTimestamp,

    pub stx_rdev_major: u32,

    pub stx_rdev_minor: u32,

    pub stx_dev_major: u32,

    pub stx_dev_minor: u32,

    pub stx_mnt_id: u64,

    pub stx_dio_mem_align: u32,

    pub stx_dio_offset_align: u32,

    pub stx_subvol: u64,

    pub stx_atomic_write_unit_min: u32,

    pub stx_atomic_write_unit_max: u32,

    pub stx_atomic_write_segments_max: u32,

    pub(crate) __spare1: [u32; 1],

    pub(crate) __spare3: [u64; 9],

}

/// `struct statx_timestamp` for use with [`Statx`].

#[repr(C)]

#[derive(Debug, Copy, Clone)]

#[non_exhaustive]

pub struct StatxTimestamp {

    /// Seconds.

    pub tv_sec: i64,

    /// Nanoseconds. Must be less than 1_000_000_000.

    pub tv_nsec: u32,

    pub(crate) __reserved: i32,

}

bitflags! {

    /// `STATX_*` constants for use with [`statx`].

    ///

    /// [`statx`]: crate::fs::statx

    #[repr(transparent)]

    #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]

    pub struct StatxFlags: u32 {

        /// `STATX_TYPE`

        const TYPE = c::STATX_TYPE;

        /// `STATX_MODE`

        const MODE = c::STATX_MODE;

        /// `STATX_NLINK`

        const NLINK = c::STATX_NLINK;

        /// `STATX_UID`

        const UID = c::STATX_UID;

        /// `STATX_GID`

        const GID = c::STATX_GID;

        /// `STATX_ATIME`

        const ATIME = c::STATX_ATIME;

        /// `STATX_MTIME`

        const MTIME = c::STATX_MTIME;

        /// `STATX_CTIME`

        const CTIME = c::STATX_CTIME;

        /// `STATX_INO`

        const INO = c::STATX_INO;

        /// `STATX_SIZE`

        const SIZE = c::STATX_SIZE;

        /// `STATX_BLOCKS`

        const BLOCKS = c::STATX_BLOCKS;

        /// `STATX_BASIC_STATS`

        const BASIC_STATS = c::STATX_BASIC_STATS;

        /// `STATX_BTIME`

        const BTIME = c::STATX_BTIME;

        /// `STATX_MNT_ID` (since Linux 5.8)

        const MNT_ID = c::STATX_MNT_ID;

        /// `STATX_DIOALIGN` (since Linux 6.1)

        const DIOALIGN = c::STATX_DIOALIGN;

        /// `STATX_ALL`

        const ALL = c::STATX_ALL;

        /// <https://docs.rs/bitflags/*/bitflags/#externally-defined-flags>

        const _ = !0;

    }

}

bitflags! {

    /// `STATX_ATTR_*` flags for use with [`Statx`].

    #[repr(transparent)]

    #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]

    pub struct StatxAttributes: u64 {

        /// `STATX_ATTR_COMPRESSED`

        const COMPRESSED = c::STATX_ATTR_COMPRESSED as u64;

        /// `STATX_ATTR_IMMUTABLE`

        const IMMUTABLE = c::STATX_ATTR_IMMUTABLE as u64;

        /// `STATX_ATTR_APPEND`

        const APPEND = c::STATX_ATTR_APPEND as u64;

        /// `STATX_ATTR_NODUMP`

        const NODUMP = c::STATX_ATTR_NODUMP as u64;

        /// `STATX_ATTR_ENCRYPTED`

        const ENCRYPTED = c::STATX_ATTR_ENCRYPTED as u64;

        /// `STATX_ATTR_AUTOMOUNT`

        const AUTOMOUNT = c::STATX_ATTR_AUTOMOUNT as u64;

        /// `STATX_ATTR_MOUNT_ROOT`

        const MOUNT_ROOT = c::STATX_ATTR_MOUNT_ROOT as u64;

        /// `STATX_ATTR_VERITY`

        const VERITY = c::STATX_ATTR_VERITY as u64;

        /// `STATX_ATTR_DAX`

        const DAX = c::STATX_ATTR_DAX as u64;

        /// <https://docs.rs/bitflags/*/bitflags/#externally-defined-flags>

        const _ = !0;

    }

}

/// `statx(dirfd, path, flags, mask, statxbuf)`—Extended `stat`.

///

/// This function returns [`io::Errno::NOSYS`] if `statx` is not available on

/// the platform, such as Linux before 4.11. This also includes older Docker

/// versions where the actual syscall fails with different error codes; rustix

/// handles this and translates them into `NOSYS`.

///

/// # References

///  - [Linux]

///

/// # Examples

///

/// ```

/// # use std::path::Path;

/// # use std::io;

/// # use rustix::fs::{AtFlags, StatxFlags};

/// # use rustix::fd::BorrowedFd;

/// /// Try to determine if the provided path is a mount root. Will return

/// /// `Ok(None)` if the kernel is not new enough to support `statx` or

/// /// [`StatxAttributes::MOUNT_ROOT`].

/// fn is_mountpoint(root: BorrowedFd<'_>, path: &Path) -> io::Result<Option<bool>> {

///     use rustix::fs::{AtFlags, StatxAttributes, StatxFlags};

///

///     match rustix::fs::statx(

///         root,

///         path,

///         AtFlags::NO_AUTOMOUNT | AtFlags::SYMLINK_NOFOLLOW,

///         StatxFlags::empty(),

///     ) {

///         Ok(r) => {

///             let present = r.stx_attributes_mask.contains(StatxAttributes::MOUNT_ROOT);

///             Ok(present.then(|| r.stx_attributes.contains(StatxAttributes::MOUNT_ROOT)))

///         }

///         Err(rustix::io::Errno::NOSYS) => Ok(None),

///         Err(e) => Err(e.into()),

///     }

/// }

/// ```

///

/// [Linux]: https://man7.org/linux/man-pages/man2/statx.2.html

#[inline]

pub fn statx<P: path::Arg, Fd: AsFd>(

    dirfd: Fd,

    path: P,

    flags: AtFlags,

    mask: StatxFlags,

) -> io::Result<Statx> {

    path.into_with_c_str(|path| _statx(dirfd.as_fd(), path, flags, mask))

}

#[cfg(not(feature = "linux_4_11"))]

mod compat {

    use crate::fd::BorrowedFd;

    use crate::ffi::CStr;

    use crate::fs::{AtFlags, Statx, StatxFlags};

    use crate::{backend, io};

    use core::sync::atomic::{AtomicU8, Ordering};

    // Linux kernel prior to 4.11 and old versions of Docker don't support

    // `statx`. We store the availability in a global to avoid unnecessary

    // syscalls.

    //

    // 0: Unknown

    // 1: Not available

    // 2: Available

    static STATX_STATE: AtomicU8 = AtomicU8::new(0);

    #[inline]

    pub fn statx(

        dirfd: BorrowedFd<'_>,

        path: &CStr,

        flags: AtFlags,

        mask: StatxFlags,

    ) -> io::Result<Statx> {

        match STATX_STATE.load(Ordering::Relaxed) {

            0 => statx_init(dirfd, path, flags, mask),

            1 => Err(io::Errno::NOSYS),

            _ => backend::fs::syscalls::statx(dirfd, path, flags, mask),

        }

    }

    /// The first `statx` call. We don't know if `statx` is available yet.

    fn statx_init(

        dirfd: BorrowedFd<'_>,

        path: &CStr,

        flags: AtFlags,

        mask: StatxFlags,

    ) -> io::Result<Statx> {

        match backend::fs::syscalls::statx(dirfd, path, flags, mask) {

            Err(err) => statx_error(err),

            result => {

                STATX_STATE.store(2, Ordering::Relaxed);

                result

            }

        }

    }

    /// The first `statx` call failed. We can get a variety of error codes

    /// from seccomp configs or faulty FUSE drivers, so we don't trust

    /// `ENOSYS` or `EPERM` to tell us whether statx is available.

    #[cold]

    fn statx_error(err: io::Errno) -> io::Result<Statx> {

        if backend::fs::syscalls::is_statx_available() {

            // Statx is available. Record this, and fail with the error

            // code of the initial `statx` call.

            STATX_STATE.store(2, Ordering::Relaxed);

            Err(err)

        } else {

            // Statx is not available. Record this, and fail with `NOSYS`.

            STATX_STATE.store(1, Ordering::Relaxed);

            Err(io::Errno::NOSYS)

        }

    }

}