//! `sys/wait.h` implementation.
//!
//! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_wait.h.html>.

use crate::{
    error::ResultExt,
    out::Out,
    platform::{
        Pal, Sys,
        types::{c_int, pid_t},
    },
};

/// Do not hang if no status is available; return immediately.
pub const WNOHANG: c_int = 1;
/// Report status of stopped child process.
pub const WUNTRACED: c_int = 2;
/// Report status of continued child process.
pub const WCONTINUED: c_int = 8;

/// Status is returned for any child that has stopped upon receipt of a signal.
pub const WSTOPPED: c_int = 2;
/// Wait for processes that have terminated.
pub const WEXITED: c_int = 4;
/// Keep the process whose status is returned in `infop` in a waitable state.
pub const WNOWAIT: c_int = 0x0100_0000;

/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man2/waitpid.2.html>.
///
/// Do not wait for children of other threads in the same thread group.
pub const __WNOTHREAD: c_int = 0x2000_0000;
/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man2/waitpid.2.html>.
///
/// Wait for all children regardless of type ("clone" or "non-clone").
pub const __WALL: c_int = 0x4000_0000;
/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man2/waitpid.2.html>.
///
/// Wait for "clone" children only.
#[allow(overflowing_literals)]
pub const __WCLONE: c_int = 0x8000_0000;

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/wait.html>.
///
/// Obtains status information pertaining to one of the caller's child
/// processes.
///
/// If returning because the status of a child process is available, returns a
/// value equal to the process ID of the child process for which status is
/// reported. If returning due to the delivery of a signal to the calling
/// process, returns `-1` and sets errno to `EINTR`. If otherwise failing,
/// returns `-1` and sets errno.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn wait(stat_loc: *mut c_int) -> pid_t {
    unsafe { waitpid(!0, stat_loc, 0) }
}

/*
 * TODO: implement idtype_t, id_t, and siginfo_t
 *
 * #[unsafe(no_mangle)]
 * pub unsafe extern "C" fn waitid(
 *     idtype: idtype_t,
 *     id: id_t,
 *     infop: siginfo_t,
 *     options: c_int
 *  ) -> c_int {
 *      unimplemented!();
 *  }
 */

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/waitpid.html>.
///
/// Obtains status information pertaining to one of the caller's child
/// processes.
///
/// If returning because the status of a child process is available, returns a
/// value equal to the process ID of the child process for which status is
/// reported. If returning due to the delivery of a signal to the calling
/// process, returns `-1` and sets errno to `EINTR`. if invoked with `WNOHANG`
/// set in `options`, it has at least one child process specified by `pid` for
/// wchich status is not available, and status is not available for any process
/// specified by `pid`, `0` is returned. If otherwise failing, returns `-1` and
/// sets errno.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn waitpid(pid: pid_t, stat_loc: *mut c_int, options: c_int) -> pid_t {
    Sys::waitpid(pid, unsafe { Out::nullable(stat_loc) }, options).or_minus_one_errno()
}