use std::fmt;
use libc::c_int;
use fcntl::Fd;
use errno::{SysResult, SysError, from_ffi};

mod ffi {
    use libc::{c_int};
    use super::EpollEvent;

    extern {
        pub fn epoll_create(size: c_int) -> c_int;
        pub fn epoll_ctl(epfd: c_int, op: c_int, fd: c_int, event: *const EpollEvent) -> c_int;
        pub fn epoll_wait(epfd: c_int, events: *mut EpollEvent, max_events: c_int, timeout: c_int) -> c_int;
    }
}

bitflags!(
    #[repr(C)]
    flags EpollEventKind: u32 {
        const EPOLLIN = 0x001,
        const EPOLLPRI = 0x002,
        const EPOLLOUT = 0x004,
        const EPOLLRDNORM = 0x040,
        const EPOLLRDBAND = 0x080,
        const EPOLLWRNORM = 0x100,
        const EPOLLWRBAND = 0x200,
        const EPOLLMSG = 0x400,
        const EPOLLERR = 0x008,
        const EPOLLHUP = 0x010,
        const EPOLLRDHUP = 0x2000,
        const EPOLLWAKEUP = 1 << 29,
        const EPOLLONESHOT = 1 << 30,
        const EPOLLET = 1 << 31
    }
)

impl fmt::Show for EpollEventKind {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        let variants = [
            (EPOLLIN,       "EPOLLIN"),
            (EPOLLPRI,      "EPOLLPRI"),
            (EPOLLOUT,      "EPOLLOUT"),
            (EPOLLRDNORM,   "EPOLLRDNORM"),
            (EPOLLRDBAND,   "EPOLLRDBAND"),
            (EPOLLWRNORM,   "EPOLLWRNORM"),
            (EPOLLWRBAND,   "EPOLLWRBAND"),
            (EPOLLMSG,      "EPOLLMSG"),
            (EPOLLERR,      "EPOLLERR"),
            (EPOLLHUP,      "EPOLLHUP"),
            (EPOLLRDHUP,    "EPOLLRDHUP"),
            (EPOLLWAKEUP,   "EPOLLWAKEUP"),
            (EPOLLONESHOT,  "EPOLLONESHOT"),
            (EPOLLET,       "EPOLLET")];

        let mut first = true;

        for &(val, name) in variants.iter() {
            if self.contains(val) {
                if first {
                    first = false;
                    try!(write!(fmt, "{}", name));
                } else {
                    try!(write!(fmt, "|{}", name));
                }
            }
        }

        Ok(())
    }
}

#[deriving(Copy)]
#[repr(C)]
pub enum EpollOp {
    EpollCtlAdd = 1,
    EpollCtlDel = 2,
    EpollCtlMod = 3
}

#[deriving(Copy)]
#[repr(C, packed)]
pub struct EpollEvent {
    pub events: EpollEventKind,
    pub data: u64
}

#[inline]
pub fn epoll_create() -> SysResult<Fd> {
    let res = unsafe { ffi::epoll_create(1024) };

    if res < 0 {
        return Err(SysError::last());
    }

    Ok(res)
}

#[inline]
pub fn epoll_ctl(epfd: Fd, op: EpollOp, fd: Fd, event: &EpollEvent) -> SysResult<()> {
    let res = unsafe { ffi::epoll_ctl(epfd, op as c_int, fd, event as *const EpollEvent) };
    from_ffi(res)
}

#[inline]
pub fn epoll_wait(epfd: Fd, events: &mut [EpollEvent], timeout_ms: uint) -> SysResult<uint> {
    let res = unsafe {
        ffi::epoll_wait(epfd, events.as_mut_ptr(), events.len() as c_int, timeout_ms as c_int)
    };

    if res < 0 {
        return Err(SysError::last());
    }

    Ok(res as uint)
}