use std::os::fd::{AsRawFd, RawFd};
use std::{cell::RefCell, collections::VecDeque, io, rc::Rc, task::Poll};

use ntex_neon::driver::{DriverApi, Handler, Interest};
use ntex_neon::{syscall, Runtime};
use ntex_util::channel::oneshot::Sender;
use slab::Slab;
use socket2::SockAddr;

#[derive(Clone)]
pub(crate) struct ConnectOps(Rc<ConnectOpsInner>);

#[derive(Debug)]
enum Change {
    Readable,
    Writable,
    Error(io::Error),
}

struct ConnectOpsBatcher {
    feed: VecDeque<(usize, Change)>,
    inner: Rc<ConnectOpsInner>,
}

struct Item {
    fd: RawFd,
    sender: Sender<io::Result<()>>,
}

struct ConnectOpsInner {
    api: DriverApi,
    connects: RefCell<Slab<Item>>,
}

impl ConnectOps {
    pub(crate) fn current() -> Self {
        Runtime::value(|rt| {
            let mut inner = None;
            rt.driver().register(|api| {
                let ops = Rc::new(ConnectOpsInner {
                    api,
                    connects: RefCell::new(Slab::new()),
                });
                inner = Some(ops.clone());
                Box::new(ConnectOpsBatcher {
                    inner: ops,
                    feed: VecDeque::new(),
                })
            });

            ConnectOps(inner.unwrap())
        })
    }

    pub(crate) fn connect(
        &self,
        fd: RawFd,
        addr: SockAddr,
        sender: Sender<io::Result<()>>,
    ) -> io::Result<usize> {
        let result = syscall!(break libc::connect(fd, addr.as_ptr(), addr.len()));

        if let Poll::Ready(res) = result {
            res?;
        }

        let item = Item { fd, sender };
        let id = self.0.connects.borrow_mut().insert(item);

        self.0.api.register(fd, id, Interest::Writable);
        Ok(id)
    }
}

impl Handler for ConnectOpsBatcher {
    fn readable(&mut self, id: usize) {
        log::debug!("connect-fd is readable {:?}", id);
        self.feed.push_back((id, Change::Readable));
    }

    fn writable(&mut self, id: usize) {
        log::debug!("connect-fd is writable {:?}", id);
        self.feed.push_back((id, Change::Writable));
    }

    fn error(&mut self, id: usize, err: io::Error) {
        self.feed.push_back((id, Change::Error(err)));
    }

    fn commit(&mut self) {
        if self.feed.is_empty() {
            return;
        }
        log::debug!("Commit connect driver changes, num: {:?}", self.feed.len());

        let mut connects = self.inner.connects.borrow_mut();

        for (id, change) in self.feed.drain(..) {
            if connects.contains(id) {
                let item = connects.remove(id);
                match change {
                    Change::Readable => unreachable!(),
                    Change::Writable => {
                        let mut err: libc::c_int = 0;
                        let mut err_len =
                            std::mem::size_of::<libc::c_int>() as libc::socklen_t;

                        let res = syscall!(libc::getsockopt(
                            item.fd.as_raw_fd(),
                            libc::SOL_SOCKET,
                            libc::SO_ERROR,
                            &mut err as *mut _ as *mut _,
                            &mut err_len
                        ));

                        let res = if err == 0 {
                            res.map(|_| ())
                        } else {
                            Err(io::Error::from_raw_os_error(err))
                        };

                        self.inner.api.unregister_all(item.fd);
                        let _ = item.sender.send(res);
                    }
                    Change::Error(err) => {
                        let _ = item.sender.send(Err(err));
                        self.inner.api.unregister_all(item.fd);
                    }
                }
            }
        }
    }
}