use alloc::format;
use crate::c_str::{CStr, CString};
use crate::error::{Errno, ResultExt};
use crate::header::fcntl::{O_CLOEXEC, O_NONBLOCK, O_RDWR};
use crate::header::errno::EFAULT;
use crate::header::errno::EINVAL;
use crate::platform::{Pal, Sys, types::{c_int, c_uint, uint64_t}};

// cbindgen can't resolve re-exports across modules, so eventfd_t is
// defined here directly (the C typedef lives in after_includes in
// cbindgen.toml). bits_eventfd still has its own copy for independent
// consumers that include only <bits/eventfd.h>.
pub type eventfd_t = uint64_t;

pub const EFD_SEMAPHORE: c_int = 1;
pub const EFD_CLOEXEC: c_int = 0x80000;
pub const EFD_NONBLOCK: c_int = 0x800;

#[unsafe(no_mangle)]
pub extern "C" fn eventfd(initval: c_uint, flags: c_int) -> c_int {
    let supported = EFD_CLOEXEC | EFD_NONBLOCK | EFD_SEMAPHORE;
    if flags & !supported != 0 {
        return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno();
    }
    let sem = if flags & EFD_SEMAPHORE != 0 { 1 } else { 0 };
    let path = format!("/scheme/event/eventfd/{}/{}", initval, sem);
    let cpath = match CString::new(path) {
        Ok(p) => p,
        Err(_) => return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno(),
    };

    let mut oflag = O_RDWR;
    if flags & EFD_CLOEXEC == EFD_CLOEXEC {
        oflag |= O_CLOEXEC;
    }
    if flags & EFD_NONBLOCK == EFD_NONBLOCK {
        oflag |= O_NONBLOCK;
    }
    Sys::open(CStr::borrow(&cpath), oflag, 0).or_minus_one_errno()
}

#[unsafe(no_mangle)]
pub extern "C" fn eventfd_read(fd: c_int, value: *mut eventfd_t) -> c_int {
    if value.is_null() {
        return Err::<c_int, _>(Errno(EFAULT)).or_minus_one_errno();
    }
    let mut buf = [0u8; 8];
    match Sys::read(fd, &mut buf) {
        Ok(8) => { unsafe { *value = u64::from_ne_bytes(buf); } 0 }
        _ => -1,
    }
}

#[unsafe(no_mangle)]
pub extern "C" fn eventfd_write(fd: c_int, value: eventfd_t) -> c_int {
    let buf = value.to_ne_bytes();
    match Sys::write(fd, &buf) {
        Ok(8) => 0,
        _ => -1,
    }
}