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

use core::num::NonZeroU64;

use crate::{
    c_str::CStr,
    error::ResultExt,
    platform::{
        Pal, Sys,
        types::{c_char, c_int, c_short, c_ulonglong, mode_t, off_t, pid_t},
    },
};

pub use self::sys::*;

use super::errno::EINVAL;

#[cfg(target_os = "linux")]
#[path = "linux.rs"]
pub mod sys;

#[cfg(target_os = "redox")]
#[path = "redox.rs"]
pub mod sys;

pub const F_DUPFD: c_int = 0;
pub const F_GETFD: c_int = 1;
pub const F_SETFD: c_int = 2;
pub const F_GETFL: c_int = 3;
pub const F_SETFL: c_int = 4;
pub const F_GETLK: c_int = 5;
pub const F_SETLK: c_int = 6;
pub const F_SETLKW: c_int = 7;
pub const F_OFD_GETLK: c_int = 36;
pub const F_OFD_SETLK: c_int = 37;
pub const F_OFD_SETLKW: c_int = 38;
pub const F_DUPFD_CLOEXEC: c_int = 1030;

pub const F_RDLCK: c_int = 0;
pub const F_WRLCK: c_int = 1;
pub const F_UNLCK: c_int = 2;

pub const F_ULOCK: c_int = 0;
pub const F_LOCK: c_int = 1;
pub const F_TLOCK: c_int = 2;
pub const F_TEST: c_int = 3;

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/creat.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn creat(path: *const c_char, mode: mode_t) -> c_int {
    unsafe { open(path, O_WRONLY | O_CREAT | O_TRUNC, mode) }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fcntl.h.html>.
#[repr(C)]
#[derive(Clone, Copy, Default)]
pub struct flock {
    pub l_type: c_short,
    pub l_whence: c_short,
    pub l_start: off_t,
    pub l_len: off_t,
    pub l_pid: pid_t,
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/fcntl.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn fcntl(fildes: c_int, cmd: c_int, mut __valist: ...) -> c_int {
    // c_ulonglong
    let arg = match cmd {
        F_DUPFD | F_SETFD | F_SETFL | F_GETLK | F_SETLK | F_SETLKW | F_OFD_GETLK | F_OFD_SETLK
        | F_OFD_SETLKW | F_DUPFD_CLOEXEC => unsafe { __valist.arg::<c_ulonglong>() },
        _ => 0,
    };

    Sys::fcntl(fildes, cmd, arg).or_minus_one_errno()
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/open.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn open(path: *const c_char, oflag: c_int, mut __valist: ...) -> c_int {
    unsafe { openat(AT_FDCWD, path, oflag, __valist) }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/openat.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn openat(
    fd: c_int,
    path: *const c_char,
    oflag: c_int,
    mut __valist: ...
) -> c_int {
    let mode = if oflag & O_CREAT == O_CREAT
    /* || oflag & O_TMPFILE == O_TMPFILE */
    {
        unsafe { __valist.arg::<mode_t>() }
    } else {
        0
    };

    let path = unsafe { CStr::from_ptr(path) };
    Sys::openat(fd, path, oflag, mode).or_minus_one_errno()
}

#[unsafe(no_mangle)]
pub unsafe extern "C" fn cbindgen_stupid_struct_user_for_fcntl(_: flock) {}

#[unsafe(no_mangle)]
pub unsafe extern "C" fn posix_fallocate(fd: c_int, offset: off_t, length: off_t) -> c_int {
    // Length can't be zero and offset must be positive.
    let Ok(offset) = offset.try_into() else {
        return EINVAL;
    };
    let Some(length) = length.try_into().ok().and_then(NonZeroU64::new) else {
        return EINVAL;
    };

    // posix_fallocate does not set errno but instead returns it.
    Sys::posix_fallocate(fd, offset, length)
        .err()
        .map(|e| e.0)
        .unwrap_or_default()
}