//! On Linux we try to use the more accurate `utimensat` syscall but this isn't

//! always available so we also fall back to `utimes` if we couldn't find

//! `utimensat` at runtime.

use crate::FileTime;

use std::ffi::CString;

use std::fs;

use std::io;

use std::os::unix::prelude::*;

use std::path::Path;

use std::ptr;

use std::sync::atomic::AtomicBool;

use std::sync::atomic::Ordering::SeqCst;

pub fn set_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {

    set_times(p, Some(atime), Some(mtime), false)

}

pub fn set_file_mtime(p: &Path, mtime: FileTime) -> io::Result<()> {

    set_times(p, None, Some(mtime), false)

}

pub fn set_file_atime(p: &Path, atime: FileTime) -> io::Result<()> {

    set_times(p, Some(atime), None, false)

}

pub fn set_file_handle_times(

    f: &fs::File,

    atime: Option<FileTime>,

    mtime: Option<FileTime>,

) -> io::Result<()> {

    // Attempt to use the `utimensat` syscall, but if it's not supported by the

    // current kernel then fall back to an older syscall.

    static INVALID: AtomicBool = AtomicBool::new(false);

    if !INVALID.load(SeqCst) {

        let times = [super::to_timespec(&atime), super::to_timespec(&mtime)];

        // We normally use a syscall because the `utimensat` function is documented

        // as not accepting a file descriptor in the first argument (even though, on

        // Linux, the syscall itself can accept a file descriptor there).

        #[cfg(not(target_env = "musl"))]

        let rc = unsafe {

            libc::syscall(

                libc::SYS_utimensat,

                f.as_raw_fd(),

                ptr::null::<libc::c_char>(),

                times.as_ptr(),

                0,

            )

        };

        // However, on musl, we call the musl libc function instead. This is because

        // on newer musl versions starting with musl 1.2, `timespec` is always a 64-bit

        // value even on 32-bit targets. As a result, musl internally converts their

        // `timespec` values to the correct ABI before invoking the syscall. Since we

        // use `timespec` from the libc crate, it matches musl's definition and not

        // the Linux kernel's version (for some platforms) so we must use musl's

        // `utimensat` function to properly convert the value. musl's `utimensat`

        // function allows file descriptors in the path argument so this is fine.

        #[cfg(target_env = "musl")]

        let rc = unsafe {

            libc::utimensat(

                f.as_raw_fd(),

                ptr::null::<libc::c_char>(),

                times.as_ptr(),

                0,

            )

        };

        if rc == 0 {

            return Ok(());

        }

        let err = io::Error::last_os_error();

        if err.raw_os_error() == Some(libc::ENOSYS) {

            INVALID.store(true, SeqCst);

        } else {

            return Err(err);

        }

    }

    super::utimes::set_file_handle_times(f, atime, mtime)

}

pub fn set_symlink_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {

    set_times(p, Some(atime), Some(mtime), true)

}

fn set_times(

    p: &Path,

    atime: Option<FileTime>,

    mtime: Option<FileTime>,

    symlink: bool,

) -> io::Result<()> {

    let flags = if symlink {

        libc::AT_SYMLINK_NOFOLLOW

    } else {

        0

    };

    // Same as the `if` statement above.

    static INVALID: AtomicBool = AtomicBool::new(false);

    if !INVALID.load(SeqCst) {

        let p = CString::new(p.as_os_str().as_bytes())?;

        let times = [super::to_timespec(&atime), super::to_timespec(&mtime)];

        let rc = unsafe { libc::utimensat(libc::AT_FDCWD, p.as_ptr(), times.as_ptr(), flags) };

        if rc == 0 {

            return Ok(());

        }

        let err = io::Error::last_os_error();

        if err.raw_os_error() == Some(libc::ENOSYS) {

            INVALID.store(true, SeqCst);

        } else {

            return Err(err);

        }

    }

    super::utimes::set_times(p, atime, mtime, symlink)

}