use std::collections::HashMap;
use std::net::SocketAddr;
use std::sync::atomic::{self, AtomicBool, AtomicU16};
use std::sync::{Arc, Mutex};

use bytes::Bytes;
use log::{debug, error, trace};

use tokio::net::TcpStream;
use tokio::sync::{mpsc, oneshot, watch};
use tokio_util::compat::*;

use futures::io::AsyncReadExt;

use async_trait::async_trait;

use kuska_handshake::async_std::{handshake_client, handshake_server, BoxStream};

use crate::error::*;
use crate::message::*;
use crate::netapp::*;
use crate::proto::*;
use crate::util::*;

pub(crate) struct ServerConn {
	pub(crate) remote_addr: SocketAddr,
	pub(crate) peer_id: NodeID,

	netapp: Arc<NetApp>,

	resp_send: mpsc::UnboundedSender<Option<(RequestID, RequestPriority, Vec<u8>)>>,
	close_send: watch::Sender<bool>,
}

impl ServerConn {
	pub(crate) async fn run(netapp: Arc<NetApp>, socket: TcpStream) -> Result<(), Error> {
		let remote_addr = socket.peer_addr()?;
		let mut socket = socket.compat();

		let handshake = handshake_server(
			&mut socket,
			netapp.netid.clone(),
			netapp.id,
			netapp.privkey.clone(),
		)
		.await?;
		let peer_id = handshake.peer_pk;

		debug!(
			"Handshake complete (server) with {}@{}",
			hex::encode(&peer_id),
			remote_addr
		);

		let (read, write) = socket.split();

		let (read, write) =
			BoxStream::from_handshake(read, write, handshake, 0x8000).split_read_write();

		let (resp_send, resp_recv) = mpsc::unbounded_channel();

		let (close_send, close_recv) = watch::channel(false);

		let conn = Arc::new(ServerConn {
			netapp: netapp.clone(),
			remote_addr,
			peer_id,
			resp_send,
			close_send,
		});

		netapp.connected_as_server(peer_id, conn.clone());

		let conn2 = conn.clone();
		let conn3 = conn.clone();
		let close_recv2 = close_recv.clone();
		tokio::try_join!(
			async move {
				tokio::select!(
					r = conn2.recv_loop(read) => r,
					_ = await_exit(close_recv) => Ok(()),
				)
			},
			async move {
				tokio::select!(
					r = conn3.send_loop(resp_recv, write) => r,
					_ = await_exit(close_recv2) => Ok(()),
				)
			},
		)
		.map(|_| ())
		.log_err("ServerConn recv_loop/send_loop");

		netapp.disconnected_as_server(&peer_id, conn);

		Ok(())
	}

	pub fn close(&self) {
		self.close_send.send(true).unwrap();
	}
}

impl SendLoop for ServerConn {}

#[async_trait]
impl RecvLoop for ServerConn {
	async fn recv_handler(self: Arc<Self>, id: u16, bytes: Vec<u8>) {
		trace!("ServerConn recv_handler {} ({} bytes)", id, bytes.len());

		let bytes: Bytes = bytes.into();

		let prio = bytes[0];

		let mut kind_bytes = [0u8; 4];
		kind_bytes.copy_from_slice(&bytes[1..5]);
		let kind = u32::from_be_bytes(kind_bytes);

		if let Some(handler) = self.netapp.msg_handlers.load().get(&kind) {
			let net_handler = &handler.net_handler;
			let resp = net_handler(self.peer_id, bytes.slice(5..)).await;
			self.resp_send
				.send(Some((id, prio, resp)))
				.log_err("ServerConn recv_handler send resp");
		}
	}
}
pub(crate) struct ClientConn {
	pub(crate) remote_addr: SocketAddr,
	pub(crate) peer_id: NodeID,

	query_send: mpsc::UnboundedSender<Option<(RequestID, RequestPriority, Vec<u8>)>>,

	next_query_number: AtomicU16,
	inflight: Mutex<HashMap<RequestID, oneshot::Sender<Vec<u8>>>>,
	must_exit: AtomicBool,
	stop_recv_loop: watch::Sender<bool>,
}

impl ClientConn {
	pub(crate) async fn init(
		netapp: Arc<NetApp>,
		socket: TcpStream,
		peer_id: NodeID,
	) -> Result<(), Error> {
		let remote_addr = socket.peer_addr()?;
		let mut socket = socket.compat();

		let handshake = handshake_client(
			&mut socket,
			netapp.netid.clone(),
			netapp.id,
			netapp.privkey.clone(),
			peer_id,
		)
		.await?;

		debug!(
			"Handshake complete (client) with {}@{}",
			hex::encode(&peer_id),
			remote_addr
		);

		let (read, write) = socket.split();

		let (read, write) =
			BoxStream::from_handshake(read, write, handshake, 0x8000).split_read_write();

		let (query_send, query_recv) = mpsc::unbounded_channel();

		let (stop_recv_loop, stop_recv_loop_recv) = watch::channel(false);

		let conn = Arc::new(ClientConn {
			remote_addr,
			peer_id,
			next_query_number: AtomicU16::from(0u16),
			query_send,
			inflight: Mutex::new(HashMap::new()),
			must_exit: AtomicBool::new(false),
			stop_recv_loop,
		});

		netapp.connected_as_client(peer_id, conn.clone());

		tokio::spawn(async move {
			let conn2 = conn.clone();
			let conn3 = conn.clone();
			tokio::try_join!(conn2.send_loop(query_recv, write), async move {
				tokio::select!(
					r = conn3.recv_loop(read) => r,
					_ = await_exit(stop_recv_loop_recv) => Ok(()),
				)
			})
			.map(|_| ())
			.log_err("ClientConn send_loop/recv_loop/dispatch_loop");

			netapp.disconnected_as_client(&peer_id, conn);
		});

		Ok(())
	}

	pub fn close(&self) {
		self.must_exit.store(true, atomic::Ordering::SeqCst);
		self.query_send
			.send(None)
			.log_err("could not write None in query_send");
		if self.inflight.lock().unwrap().is_empty() {
			self.stop_recv_loop
				.send(true)
				.log_err("could not write true to stop_recv_loop");
		}
	}

	pub(crate) async fn request<T>(
		self: Arc<Self>,
		rq: T,
		prio: RequestPriority,
	) -> Result<<T as Message>::Response, Error>
	where
		T: Message,
	{
		let id = self
			.next_query_number
			.fetch_add(1u16, atomic::Ordering::Relaxed);
		let mut bytes = vec![prio];
		bytes.extend_from_slice(&u32::to_be_bytes(T::KIND)[..]);
		bytes.extend_from_slice(&rmp_to_vec_all_named(&rq)?[..]);

		let (resp_send, resp_recv) = oneshot::channel();
		let old = self.inflight.lock().unwrap().insert(id, resp_send);
		if let Some(old_ch) = old {
			error!(
				"Too many inflight requests! RequestID collision. Interrupting previous request."
			);
			if old_ch.send(vec![]).is_err() {
				debug!("Could not send empty response to collisionned request, probably because request was interrupted. Dropping response.");
			}
		}

		trace!("request: query_send {}, {} bytes", id, bytes.len());
		self.query_send.send(Some((id, prio, bytes)))?;

		let resp = resp_recv.await?;

		rmp_serde::decode::from_read_ref::<_, Result<<T as Message>::Response, String>>(&resp[..])?
			.map_err(Error::Remote)
	}
}

impl SendLoop for ClientConn {}

#[async_trait]
impl RecvLoop for ClientConn {
	async fn recv_handler(self: Arc<Self>, id: RequestID, msg: Vec<u8>) {
		trace!("ClientConn recv_handler {} ({} bytes)", id, msg.len());

		let mut inflight = self.inflight.lock().unwrap();
		if let Some(ch) = inflight.remove(&id) {
			if ch.send(msg).is_err() {
				debug!("Could not send request response, probably because request was interrupted. Dropping response.");
			}
		}

		if inflight.is_empty() && self.must_exit.load(atomic::Ordering::SeqCst) {
			self.stop_recv_loop
				.send(true)
				.log_err("could not write true to stop_recv_loop");
		}
	}
}