//! libc syscalls supporting `rustix::event`.

use crate::backend::c;
use crate::backend::conv::ret_c_int;
#[cfg(any(apple, netbsdlike, target_os = "dragonfly", target_os = "solaris"))]
use crate::backend::conv::ret_owned_fd;
use crate::event::PollFd;
#[cfg(any(linux_kernel, bsd, solarish, target_os = "espidf"))]
use crate::fd::OwnedFd;
use crate::io;
#[cfg(any(bsd, solarish))]
use {crate::backend::conv::borrowed_fd, crate::fd::BorrowedFd, core::mem::MaybeUninit};
#[cfg(solarish)]
use {
    crate::backend::conv::ret, crate::event::port::Event, crate::utils::as_mut_ptr,
    core::ptr::null_mut,
};
#[cfg(any(
    linux_kernel,
    target_os = "freebsd",
    target_os = "illumos",
    target_os = "espidf"
))]
use {crate::backend::conv::ret_owned_fd, crate::event::EventfdFlags};
#[cfg(bsd)]
use {crate::event::kqueue::Event, crate::utils::as_ptr, core::ptr::null};

#[cfg(any(
    linux_kernel,
    target_os = "freebsd",
    target_os = "illumos",
    target_os = "espidf"
))]
pub(crate) fn eventfd(initval: u32, flags: EventfdFlags) -> io::Result<OwnedFd> {
    #[cfg(linux_kernel)]
    unsafe {
        syscall! {
            fn eventfd2(
                initval: c::c_uint,
                flags: c::c_int
            ) via SYS_eventfd2 -> c::c_int
        }
        ret_owned_fd(eventfd2(initval, bitflags_bits!(flags)))
    }

    // `eventfd` was added in FreeBSD 13, so it isn't available on FreeBSD 12.
    #[cfg(target_os = "freebsd")]
    unsafe {
        weakcall! {
            fn eventfd(
                initval: c::c_uint,
                flags: c::c_int
            ) -> c::c_int
        }
        ret_owned_fd(eventfd(initval, bitflags_bits!(flags)))
    }

    #[cfg(any(target_os = "illumos", target_os = "espidf"))]
    unsafe {
        ret_owned_fd(c::eventfd(initval, bitflags_bits!(flags)))
    }
}

#[cfg(bsd)]
pub(crate) fn kqueue() -> io::Result<OwnedFd> {
    unsafe { ret_owned_fd(c::kqueue()) }
}

#[cfg(bsd)]
pub(crate) unsafe fn kevent(
    kq: BorrowedFd<'_>,
    changelist: &[Event],
    eventlist: &mut [MaybeUninit<Event>],
    timeout: Option<&c::timespec>,
) -> io::Result<c::c_int> {
    ret_c_int(c::kevent(
        borrowed_fd(kq),
        changelist.as_ptr().cast(),
        changelist
            .len()
            .try_into()
            .map_err(|_| io::Errno::OVERFLOW)?,
        eventlist.as_mut_ptr().cast(),
        eventlist
            .len()
            .try_into()
            .map_err(|_| io::Errno::OVERFLOW)?,
        timeout.map_or(null(), as_ptr),
    ))
}

#[inline]
pub(crate) fn poll(fds: &mut [PollFd<'_>], timeout: c::c_int) -> io::Result<usize> {
    let nfds = fds
        .len()
        .try_into()
        .map_err(|_convert_err| io::Errno::INVAL)?;

    ret_c_int(unsafe { c::poll(fds.as_mut_ptr().cast(), nfds, timeout) })
        .map(|nready| nready as usize)
}

#[cfg(solarish)]
pub(crate) fn port_create() -> io::Result<OwnedFd> {
    unsafe { ret_owned_fd(c::port_create()) }
}

#[cfg(solarish)]
pub(crate) unsafe fn port_associate(
    port: BorrowedFd<'_>,
    source: c::c_int,
    object: c::uintptr_t,
    events: c::c_int,
    user: *mut c::c_void,
) -> io::Result<()> {
    ret(c::port_associate(
        borrowed_fd(port),
        source,
        object,
        events,
        user,
    ))
}

#[cfg(solarish)]
pub(crate) unsafe fn port_dissociate(
    port: BorrowedFd<'_>,
    source: c::c_int,
    object: c::uintptr_t,
) -> io::Result<()> {
    ret(c::port_dissociate(borrowed_fd(port), source, object))
}

#[cfg(solarish)]
pub(crate) fn port_get(
    port: BorrowedFd<'_>,
    timeout: Option<&mut c::timespec>,
) -> io::Result<Event> {
    let mut event = MaybeUninit::<c::port_event>::uninit();
    let timeout = timeout.map_or(null_mut(), as_mut_ptr);

    unsafe {
        ret(c::port_get(borrowed_fd(port), event.as_mut_ptr(), timeout))?;
    }

    // If we're done, initialize the event and return it.
    Ok(Event(unsafe { event.assume_init() }))
}

#[cfg(solarish)]
pub(crate) fn port_getn(
    port: BorrowedFd<'_>,
    timeout: Option<&mut c::timespec>,
    events: &mut Vec<Event>,
    mut nget: u32,
) -> io::Result<()> {
    let timeout = timeout.map_or(null_mut(), as_mut_ptr);
    unsafe {
        ret(c::port_getn(
            borrowed_fd(port),
            events.as_mut_ptr().cast(),
            events.len().try_into().unwrap(),
            &mut nget,
            timeout,
        ))?;
    }

    // Update the vector length.
    unsafe {
        events.set_len(nget.try_into().unwrap());
    }

    Ok(())
}

#[cfg(solarish)]
pub(crate) fn port_send(
    port: BorrowedFd<'_>,
    events: c::c_int,
    userdata: *mut c::c_void,
) -> io::Result<()> {
    unsafe { ret(c::port_send(borrowed_fd(port), events, userdata)) }
}
