use std::cell::RefCell;
use std::collections::BTreeMap;
use std::net::SocketAddr;
use std::rc::Rc;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;
use std::time::Duration;

use aquatic_common::access_list::AccessList;
use aquatic_common::convert_ipv4_mapped_ipv6;
use aquatic_ws_protocol::*;
use async_tungstenite::WebSocketStream;
use either::Either;
use futures::stream::{SplitSink, SplitStream};
use futures_lite::StreamExt;
use futures_rustls::server::TlsStream;
use futures_rustls::TlsAcceptor;
use glommio::channels::channel_mesh::{MeshBuilder, Partial, Role, Senders};
use glommio::channels::local_channel::{new_bounded, LocalReceiver, LocalSender};
use glommio::channels::shared_channel::ConnectedReceiver;
use glommio::net::{TcpListener, TcpStream};
use glommio::timer::TimerActionRepeat;
use glommio::{enclose, prelude::*};
use hashbrown::HashMap;
use slab::Slab;

use crate::config::Config;

use super::common::*;

struct PendingScrapeResponse {
    pending_worker_out_messages: usize,
    stats: HashMap<InfoHash, ScrapeStatistics>,
}

struct ConnectionReference {
    out_message_sender: LocalSender<(ConnectionMeta, OutMessage)>,
}

struct Connection {
    config: Rc<Config>,
    access_list: Rc<RefCell<AccessList>>,
    in_message_senders: Rc<Senders<(ConnectionMeta, InMessage)>>,
    out_message_receiver: LocalReceiver<(ConnectionMeta, OutMessage)>,
    out_message_consumer_id: ConsumerId,
    ws_out: SplitSink<WebSocketStream<TlsStream<TcpStream>>, tungstenite::Message>,
    ws_in: SplitStream<WebSocketStream<TlsStream<TcpStream>>>,
    peer_addr: SocketAddr,
    connection_id: ConnectionId,
}

pub async fn run_socket_worker(
    config: Config,
    tls_config: Arc<TlsConfig>,
    in_message_mesh_builder: MeshBuilder<(ConnectionMeta, InMessage), Partial>,
    out_message_mesh_builder: MeshBuilder<(ConnectionMeta, OutMessage), Partial>,
    num_bound_sockets: Arc<AtomicUsize>,
    access_list: AccessList,
) {
    let config = Rc::new(config);
    let access_list = Rc::new(RefCell::new(access_list));

    let listener = TcpListener::bind(config.network.address).expect("bind socket");
    num_bound_sockets.fetch_add(1, Ordering::SeqCst);

    let (in_message_senders, _) = in_message_mesh_builder.join(Role::Producer).await.unwrap();
    let in_message_senders = Rc::new(in_message_senders);

    let (_, mut out_message_receivers) =
        out_message_mesh_builder.join(Role::Consumer).await.unwrap();
    let out_message_consumer_id = ConsumerId(out_message_receivers.consumer_id().unwrap());

    let connection_slab = Rc::new(RefCell::new(Slab::new()));
    let connections_to_remove = Rc::new(RefCell::new(Vec::new()));

    // Periodically update access list
    TimerActionRepeat::repeat(enclose!((config, access_list) move || {
        enclose!((config, access_list) move || async move {
            update_access_list(config.clone(), access_list.clone()).await;

            Some(Duration::from_secs(config.cleaning.interval))
        })()
    }));

    // Periodically remove closed connections
    TimerActionRepeat::repeat(
        enclose!((config, connection_slab, connections_to_remove) move || {
            remove_closed_connections(
                config.clone(),
                connection_slab.clone(),
                connections_to_remove.clone(),
            )
        }),
    );

    for (_, out_message_receiver) in out_message_receivers.streams() {
        spawn_local(receive_out_messages(
            out_message_receiver,
            connection_slab.clone(),
        ))
        .detach();
    }

    let mut incoming = listener.incoming();

    while let Some(stream) = incoming.next().await {
        match stream {
            Ok(stream) => {
                let (out_message_sender, out_message_receiver) =
                    new_bounded(config.request_workers);
                let key = connection_slab
                    .borrow_mut()
                    .insert(ConnectionReference { out_message_sender });

                spawn_local(enclose!((config, access_list, in_message_senders, tls_config, connections_to_remove) async move {
                    if let Err(err) = Connection::run(
                        config,
                        access_list,
                        in_message_senders,
                        out_message_receiver,
                        out_message_consumer_id,
                        ConnectionId(key),
                        tls_config,
                        stream
                    ).await {
                        ::log::debug!("Connection::run() error: {:?}", err);
                    }

                    connections_to_remove.borrow_mut().push(key);
                }))
                .detach();
            }
            Err(err) => {
                ::log::error!("accept connection: {:?}", err);
            }
        }
    }
}

async fn remove_closed_connections(
    config: Rc<Config>,
    connection_slab: Rc<RefCell<Slab<ConnectionReference>>>,
    connections_to_remove: Rc<RefCell<Vec<usize>>>,
) -> Option<Duration> {
    let connections_to_remove = connections_to_remove.replace(Vec::new());

    for connection_id in connections_to_remove {
        if let Some(_) = connection_slab.borrow_mut().try_remove(connection_id) {
            ::log::debug!("removed connection with id {}", connection_id);
        } else {
            ::log::error!(
                "couldn't remove connection with id {}, it is not in connection slab",
                connection_id
            );
        }
    }

    Some(Duration::from_secs(config.cleaning.interval))
}

async fn receive_out_messages(
    mut out_message_receiver: ConnectedReceiver<(ConnectionMeta, OutMessage)>,
    connection_references: Rc<RefCell<Slab<ConnectionReference>>>,
) {
    while let Some(channel_out_message) = out_message_receiver.next().await {
        if let Some(reference) = connection_references
            .borrow()
            .get(channel_out_message.0.connection_id.0)
        {
            if let Err(err) = reference.out_message_sender.try_send(channel_out_message) {
                ::log::error!("Couldn't send out_message to local receiver: {:?}", err);
            }
        }
    }
}

impl Connection {
    async fn run(
        config: Rc<Config>,
        access_list: Rc<RefCell<AccessList>>,
        in_message_senders: Rc<Senders<(ConnectionMeta, InMessage)>>,
        out_message_receiver: LocalReceiver<(ConnectionMeta, OutMessage)>,
        out_message_consumer_id: ConsumerId,
        connection_id: ConnectionId,
        tls_config: Arc<TlsConfig>,
        stream: TcpStream,
    ) -> anyhow::Result<()> {
        let peer_addr = stream
            .peer_addr()
            .map_err(|err| anyhow::anyhow!("Couldn't get peer addr: {:?}", err))?;

        let tls_acceptor: TlsAcceptor = tls_config.into();
        let stream = tls_acceptor.accept(stream).await?;

        let ws_config = tungstenite::protocol::WebSocketConfig {
            max_frame_size: Some(config.network.websocket_max_frame_size),
            max_message_size: Some(config.network.websocket_max_message_size),
            ..Default::default()
        };
        let stream = async_tungstenite::accept_async_with_config(stream, Some(ws_config)).await?;
        let (ws_out, ws_in) = futures::StreamExt::split(stream);

        let mut conn = Connection {
            config: config.clone(),
            access_list: access_list.clone(),
            in_message_senders: in_message_senders.clone(),
            out_message_receiver,
            out_message_consumer_id,
            ws_out,
            ws_in,
            peer_addr,
            connection_id,
        };

        conn.run_message_loop().await?;

        Ok(())
    }

    async fn run_message_loop(&mut self) -> anyhow::Result<()> {
        loop {
            let out_message = match self.read_in_message().await? {
                Either::Left(out_message) => OutMessage::ErrorResponse(out_message),
                Either::Right(in_message) => self.handle_in_message(in_message).await?,
            };

            self.write_out_message(&out_message).await?;

            if matches!(out_message, OutMessage::ErrorResponse(_)) {
                // TODO: shut down?

                break;
            }
        }

        Ok(())
    }

    async fn read_in_message(&mut self) -> anyhow::Result<Either<ErrorResponse, InMessage>> {
        loop {
            ::log::debug!("read");

            let message = self.ws_in.next().await.unwrap()?;

            match InMessage::from_ws_message(message) {
                Ok(in_message) => {
                    ::log::debug!("received in_message: {:?}", in_message);

                    return Ok(Either::Right(in_message));
                }
                Err(err) => {
                    ::log::debug!("Couldn't parse in_message: {:?}", err);

                    let out_message = ErrorResponse {
                        action: None,
                        failure_reason: "Invalid request".into(),
                        info_hash: None,
                    };

                    return Ok(Either::Left(out_message));
                }
            }
        }
    }

    async fn handle_in_message(&self, in_message: InMessage) -> anyhow::Result<OutMessage> {
        match in_message {
            InMessage::AnnounceRequest(announce_request) => {
                let info_hash = announce_request.info_hash;

                if self
                    .access_list
                    .borrow()
                    .allows(self.config.access_list.mode, &info_hash.0)
                {
                    let meta = ConnectionMeta {
                        connection_id: self.connection_id,
                        out_message_consumer_id: self.out_message_consumer_id,
                        naive_peer_addr: self.peer_addr,
                        converted_peer_ip: convert_ipv4_mapped_ipv6(self.peer_addr.ip()),
                    };
                    let in_message = InMessage::AnnounceRequest(announce_request);

                    let consumer_index =
                        calculate_in_message_consumer_index(&self.config, info_hash);

                    // Only fails when receiver is closed
                    self.in_message_senders
                        .send_to(consumer_index, (meta, in_message))
                        .await
                        .unwrap();

                    self.wait_for_out_message(None).await
                } else {
                    let out_message = OutMessage::ErrorResponse(ErrorResponse {
                        action: Some(ErrorResponseAction::Announce),
                        failure_reason: "Info hash not allowed".into(),
                        info_hash: Some(info_hash),
                    });

                    Ok(out_message)
                }
            }
            InMessage::ScrapeRequest(ScrapeRequest { info_hashes, .. }) => {
                let info_hashes = if let Some(info_hashes) = info_hashes {
                    info_hashes
                } else {
                    let out_message = OutMessage::ErrorResponse(ErrorResponse {
                        action: Some(ErrorResponseAction::Scrape),
                        failure_reason: "Full scrapes are not allowed".into(),
                        info_hash: None,
                    });

                    return Ok(out_message);
                };

                let mut info_hashes_by_worker: BTreeMap<usize, Vec<InfoHash>> = BTreeMap::new();

                for info_hash in info_hashes.as_vec() {
                    let info_hashes = info_hashes_by_worker
                        .entry(calculate_in_message_consumer_index(&self.config, info_hash))
                        .or_default();

                    info_hashes.push(info_hash);
                }

                let pending_worker_out_messages = info_hashes_by_worker.len();

                let meta = ConnectionMeta {
                    connection_id: self.connection_id,
                    out_message_consumer_id: self.out_message_consumer_id,
                    naive_peer_addr: self.peer_addr,
                    converted_peer_ip: convert_ipv4_mapped_ipv6(self.peer_addr.ip()),
                };

                for (consumer_index, info_hashes) in info_hashes_by_worker {
                    let in_message = InMessage::ScrapeRequest(ScrapeRequest {
                        action: ScrapeAction,
                        info_hashes: Some(ScrapeRequestInfoHashes::Multiple(info_hashes)),
                    });

                    // Only fails when receiver is closed
                    self.in_message_senders
                        .send_to(consumer_index, (meta, in_message))
                        .await
                        .unwrap();
                }

                let pending_scrape_out_message = PendingScrapeResponse {
                    pending_worker_out_messages,
                    stats: Default::default(),
                };

                self.wait_for_out_message(Some(pending_scrape_out_message))
                    .await
            }
        }
    }

    /// Wait for announce out_message or partial scrape out_messages to arrive,
    /// return full out_message
    async fn wait_for_out_message(
        &self,
        mut opt_pending_scrape_out_message: Option<PendingScrapeResponse>,
    ) -> anyhow::Result<OutMessage> {
        loop {
            let (meta, out_message) = self
                .out_message_receiver
                .recv()
                .await
                .expect("wait_for_out_message: can't receive out_message, sender is closed");

            if meta.naive_peer_addr != self.peer_addr {
                return Err(anyhow::anyhow!("peer addresses didn't match"));
            }

            match out_message {
                OutMessage::ScrapeResponse(out_message) => {
                    if let Some(mut pending) = opt_pending_scrape_out_message.take() {
                        pending.stats.extend(out_message.files);
                        pending.pending_worker_out_messages -= 1;

                        if pending.pending_worker_out_messages == 0 {
                            let out_message = OutMessage::ScrapeResponse(ScrapeResponse {
                                action: ScrapeAction,
                                files: pending.stats,
                            });

                            break Ok(out_message);
                        } else {
                            opt_pending_scrape_out_message = Some(pending);
                        }
                    } else {
                        return Err(anyhow::anyhow!(
                            "received channel scrape out_message without pending scrape out_message"
                        ));
                    }
                }
                out_message => {
                    break Ok(out_message);
                }
            };
        }
    }

    async fn write_out_message(&mut self, out_message: &OutMessage) -> anyhow::Result<()> {
        futures::SinkExt::send(&mut self.ws_out, out_message.to_ws_message()).await?;
        futures::SinkExt::flush(&mut self.ws_out).await?;

        Ok(())
    }
}

fn calculate_in_message_consumer_index(config: &Config, info_hash: InfoHash) -> usize {
    (info_hash.0[0] as usize) % config.request_workers
}