use super::fleck_core;
use std::{
    cell::RefCell,
    collections::VecDeque,
    io::{Read, Write},
    os::fd::AsRawFd,
    rc::Rc,
};

use mio::net::{UnixListener, UnixStream};

use super::{FdHandler, IOService, InterestRegistration};

#[derive(Default)]
pub struct UnixSocketBuilder {
    path: Option<String>,
    connect: Option<bool>,
}

impl UnixSocketBuilder {
    pub fn set_path<S: Into<String>>(mut self, path: S) -> Self {
        self.path = Some(path.into());
        self
    }

    pub fn connect_mode(mut self) -> Self {
        self.connect = Some(true);
        self
    }

    pub fn serve_mode(mut self) -> Self {
        self.connect = Some(false);
        self
    }

    pub fn build(self, io: &IOService) -> UnixSocketRef {
        let sock = match self.connect.unwrap() {
            true => UnixSocket::Client(UnixClientSocket::connect(io, self.path.unwrap())),
            false => UnixSocket::Server(UnixServerSocket::build(io, self.path.unwrap())),
        };

        UnixSocketRef { sock }
    }
}

pub struct UnixSocketRef {
    sock: UnixSocket,
}

impl UnixSocketRef {
    pub fn connected_peer(&self) -> fleck_core::Peer {
        match &self.sock {
            UnixSocket::Client(client) => client.peer.get().unwrap().clone(),
            UnixSocket::Server(_) => {
                panic!("Can't get the connected peer for a UNIX server socket!")
            },
        }
    }
}

enum UnixSocket {
    Client(Rc<UnixClientSocket>),
    Server(Rc<UnixServerSocket>),
}

pub struct UnixClientSocket {
    api: std::rc::Rc<crate::API>,
    interest: InterestRegistration,
    socket: RefCell<mio::net::UnixStream>,
    peer: once_cell::unsync::OnceCell<fleck_core::Peer>,
    send_queue: RefCell<VecDeque<u8>>,
    recv_queue: RefCell<VecDeque<u8>>,
}

impl UnixClientSocket {
    fn connect(io: &IOService, path: String) -> Rc<Self> {
        let socket = UnixStream::connect(path).expect("couldn't connect to socket?");
        Self::build(io, socket)
    }

    fn build(io: &IOService, socket: UnixStream) -> Rc<Self> {
        let interest = io.register_interest(socket.as_raw_fd());

        let sock = Rc::new(Self {
            api: io.api.clone(),
            interest,
            socket: RefCell::new(socket),
            peer: Default::default(),
            recv_queue: Default::default(),
            send_queue: Default::default(),
        });

        let peer = fleck_core::Peer {
            data: Rc::new(fleck_core::peer::PeerData::new(
                sock.clone(),
                fleck_core::peer::PeerAddress::Stream,
            )),
        };

        sock.peer
            .set(peer)
            .expect("somehow couldn't initialize the once_cell?");

        io.api.queue::<super::NewHandlerChannel>(sock.clone());

        sock
    }
}

impl FdHandler for UnixClientSocket {
    fn interest(&self) -> &InterestRegistration {
        &self.interest
    }

    fn ready_read(&self, _rc: &Rc<dyn FdHandler>) {
        // read all available data
        let mut buf = [0u8; 2048];
        let mut rq = self.recv_queue.borrow_mut();
        while let Ok(bytes) = self.socket.borrow_mut().read(&mut buf) {
            rq.extend(&buf[0..bytes]);
        }

        // parse as many packets as possible
        while rq.len() >= 2 {
            let data = rq.make_contiguous();
            let packet_len = u16::from_be_bytes(data[0..2].try_into().unwrap()) as usize;
            if data.len() < (packet_len + 2) {
                break;
            }
            if let Ok(mut msg) =
                bincode::deserialize::<fleck_core::msg::Message>(&data[2..(packet_len + 2)])
            {
                msg.peer = self.peer.get().cloned();
                self.api.queue::<fleck_core::ReceivePacketChannel>(msg);
            }
            rq.drain(0..(packet_len + 2));
        }
    }

    fn ready_write(&self, _rc: &Rc<dyn FdHandler>) {
        let mut sq = self.send_queue.borrow_mut();

        while sq.len() > 0 {
            let data = sq.make_contiguous();
            if let Ok(bytes) = self.socket.borrow_mut().write(data) {
                sq.drain(0..bytes);
            } else {
                return;
            }
        }

        self.interest.update_interest(mio::Interest::READABLE);
    }

    fn dispatch(&self, msg: crate::fleck_core::msg::Message) {
        let mut sq = self.send_queue.borrow_mut();
        let data = bincode::serialize(&msg).expect("couldn't serialize message?");
        sq.extend(u16::to_be_bytes(data.len() as u16));
        sq.extend(data);
        self.interest
            .update_interest(mio::Interest::READABLE.add(mio::Interest::WRITABLE));
    }
}

pub struct UnixServerSocket {
    api: std::rc::Rc<crate::API>,
    interest: InterestRegistration,
    socket: UnixListener,
}

impl UnixServerSocket {
    fn build(io: &IOService, path: String) -> Rc<Self> {
        match std::fs::remove_file(&path) {
            Ok(_) => (),
            Err(e) => match e.kind() {
                std::io::ErrorKind::PermissionDenied => {
                    panic!("couldn't remove existing socket file!")
                },
                std::io::ErrorKind::NotFound => {
                    // this is perfectly okay!
                },
                k => {
                    panic!("Unexpected error removing socket file: {:?}", k)
                },
            },
        }

        let socket = UnixListener::bind(path).expect("couldn't bind to given path");
        let interest = io.register_interest(socket.as_raw_fd());

        let sock = Rc::new(Self {
            api: io.api.clone(),
            interest,
            socket,
        });

        io.register_handler(sock.clone());

        sock
    }
}

impl FdHandler for UnixServerSocket {
    fn interest(&self) -> &InterestRegistration {
        &self.interest
    }

    fn ready_read(&self, _rc: &Rc<dyn FdHandler>) {
        loop {
            let client = self.socket.accept();
            if let Err(err) = client {
                if err.kind() == std::io::ErrorKind::WouldBlock {
                    break;
                } else {
                    panic!("Unexpected error occurred while accepting new UNIX socket client");
                }
            }

            self.api.with_service(|io: &IOService| {
                UnixClientSocket::build(io, client.unwrap().0);
            });
        }
    }

    fn ready_write(&self, _rc: &Rc<dyn FdHandler>) {
        unreachable!();
    }

    fn dispatch(&self, _msg: fleck_core::msg::Message) {
        unreachable!();
    }
}