mod proto;

use std::collections::HashMap;
use std::fs::File;
use std::io::BufReader as SyncBufReader;
use std::net::SocketAddr;
use std::path::PathBuf;
use std::sync::Arc;

use futures_util::future::join_all;
use prometheus::Registry as MetricsRegistry;
use quick_xml::events::{BytesDecl, Event};
use quick_xml::{NsReader, Writer};
use rustls_pemfile::{certs, read_one, Item as PemItem};
use serde::Deserialize;
use tokio::io::{AsyncBufRead, AsyncWrite, AsyncWriteExt, BufReader, BufWriter};
use tokio::net::{TcpListener, TcpStream};
use tokio::sync::mpsc::channel;
use tokio_rustls::rustls::{Certificate, PrivateKey};
use tokio_rustls::TlsAcceptor;

use crate::core::player::{PlayerConnection, PlayerId, PlayerRegistry};
use crate::core::room::{RoomId, RoomRegistry};
use crate::prelude::*;
use crate::protos::xmpp;
use crate::protos::xmpp::bind::{BindResponse, Jid, Name, Resource, Server};
use crate::protos::xmpp::client::{Iq, Message, MessageType, Presence};
use crate::protos::xmpp::disco::*;
use crate::protos::xmpp::roster::RosterQuery;
use crate::protos::xmpp::session::Session;
use crate::protos::xmpp::stream::*;
use crate::util::xml::{Continuation, FromXml, Parser, ToXml};
use crate::util::Terminator;

use self::proto::{ClientPacket, IqClientBody};

#[derive(Deserialize, Debug, Clone)]
pub struct ServerConfig {
    pub listen_on: SocketAddr,
    pub cert: PathBuf,
    pub key: PathBuf,
}

struct LoadedConfig {
    cert: Certificate,
    key: PrivateKey,
}

struct Authenticated {
    player_id: PlayerId,
    xmpp_name: Name,
    xmpp_resource: Resource,
    xmpp_muc_name: Resource,
}

pub async fn launch(
    config: ServerConfig,
    players: PlayerRegistry,
    rooms: RoomRegistry,
    metrics: MetricsRegistry,
) -> Result<Terminator> {
    log::info!("Starting XMPP projection");

    let certs = certs(&mut SyncBufReader::new(File::open(config.cert)?))?;
    let certs = certs.into_iter().map(Certificate).collect::<Vec<_>>();

    let key = match read_one(&mut SyncBufReader::new(File::open(config.key)?))? {
        Some(PemItem::ECKey(k) | PemItem::PKCS8Key(k) | PemItem::RSAKey(k)) => PrivateKey(k),
        _ => panic!("no keys in file"),
    };

    let loaded_config = Arc::new(LoadedConfig {
        cert: certs.into_iter().next().expect("no certs in file"),
        key,
    });

    let listener = TcpListener::bind(config.listen_on).await?;
    let terminator = Terminator::spawn(|mut termination| async move {
        let (stopped_tx, mut stopped_rx) = channel(32);
        let mut actors = HashMap::new();
        loop {
            select! {
                biased;
                _ = &mut termination => break,
                stopped = stopped_rx.recv() => match stopped {
                    Some(stopped) => { let _ = actors.remove(&stopped); },
                    None => unreachable!(),
                },
                new_conn = listener.accept() => {
                    match new_conn {
                        Ok((stream, socket_addr)) => {
                            log::debug!("Incoming connection from {socket_addr}");
                            if actors.contains_key(&socket_addr) {
                                log::warn!("Already contains connection form {socket_addr}");
                                // TODO kill the older connection and restart it
                                continue;
                            }
                            let players = players.clone();
                            let rooms = rooms.clone();
                            let terminator = Terminator::spawn(|termination| {
                                let stopped_tx = stopped_tx.clone();
                                let loaded_config = loaded_config.clone();
                                async move {
                                    match handle_socket(loaded_config, stream, &socket_addr, players, rooms, termination).await {
                                        Ok(_) => log::info!("Connection terminated"),
                                        Err(err) => log::warn!("Connection failed: {err}"),
                                    }
                                    stopped_tx.send(socket_addr).await?;
                                    Ok(())
                                }
                            });

                            actors.insert(socket_addr, terminator);
                        },
                        Err(err) => log::warn!("Failed to accept new connection: {err}"),
                    }
                },
            }
        }
        log::info!("Stopping XMPP projection");
        join_all(
            actors
                .into_iter()
                .map(|(socket_addr, terminator)| async move {
                    log::debug!("Stopping XMPP connection at {socket_addr}");
                    match terminator.terminate().await {
                        Ok(_) => log::debug!("Stopped XMPP connection at {socket_addr}"),
                        Err(err) => {
                            log::warn!(
                                "XMPP connection to {socket_addr} finished with error: {err}"
                            )
                        }
                    }
                }),
        )
        .await;
        log::info!("Stopped XMPP projection");
        Ok(())
    });
    log::info!("Started XMPP projection");
    Ok(terminator)
}

async fn handle_socket(
    config: Arc<LoadedConfig>,
    mut stream: TcpStream,
    socket_addr: &SocketAddr,
    mut players: PlayerRegistry,
    rooms: RoomRegistry,
    termination: Deferred<()>, // TODO use it to stop the connection gracefully
) -> Result<()> {
    log::info!("Received an XMPP connection from {socket_addr}");
    let mut reader_buf = vec![];
    let (reader, writer) = stream.split();
    let mut buf_reader = BufReader::new(reader);
    let mut buf_writer = BufWriter::new(writer);

    socket_force_tls(&mut buf_reader, &mut buf_writer, &mut reader_buf).await?;

    let mut config = tokio_rustls::rustls::ServerConfig::builder()
        .with_safe_defaults()
        .with_no_client_auth()
        .with_single_cert(vec![config.cert.clone()], config.key.clone())?;
    config.key_log = Arc::new(tokio_rustls::rustls::KeyLogFile::new());

    let acceptor = TlsAcceptor::from(Arc::new(config));
    let new_stream = acceptor.accept(stream).await?;
    log::debug!("TLS connection established");

    let (a, b) = tokio::io::split(new_stream);
    let mut xml_reader = NsReader::from_reader(BufReader::new(a));
    let mut xml_writer = Writer::new(b);

    let authenticated = socket_auth(&mut xml_reader, &mut xml_writer, &mut reader_buf).await?;
    log::debug!("User authenticated");
    let mut connection = players
        .connect_to_player(authenticated.player_id.clone())
        .await;
    socket_final(
        &mut xml_reader,
        &mut xml_writer,
        &mut reader_buf,
        &authenticated,
        &mut connection,
        &rooms,
    )
    .await?;

    let a = xml_reader.into_inner().into_inner();
    let b = xml_writer.into_inner();
    a.unsplit(b).shutdown().await?;
    Ok(())
}

async fn socket_force_tls(
    reader: &mut (impl AsyncBufRead + Unpin),
    writer: &mut (impl AsyncWrite + Unpin),
    reader_buf: &mut Vec<u8>,
) -> Result<()> {
    use crate::protos::xmpp::tls::*;
    let xml_reader = &mut NsReader::from_reader(reader);
    let xml_writer = &mut Writer::new(writer);
    read_xml_header(xml_reader, reader_buf).await?;
    let _ = ClientStreamStart::parse(xml_reader, reader_buf).await?;

    let event = Event::Decl(BytesDecl::new("1.0", None, None));
    xml_writer.write_event_async(event).await?;
    let msg = ServerStreamStart {
        from: "localhost".into(),
        lang: "en".into(),
        id: uuid::Uuid::new_v4().to_string(),
        version: "1.0".into(),
    };
    msg.write_xml(xml_writer).await?;
    let msg = Features {
        start_tls: true,
        mechanisms: false,
        bind: false,
    };
    msg.write_xml(xml_writer).await?;
    xml_writer.get_mut().flush().await?;

    let StartTLS = StartTLS::parse(xml_reader, reader_buf).await?;
    ProceedTLS.write_xml(xml_writer).await?;
    xml_writer.get_mut().flush().await?;
    Ok(())
}

async fn socket_auth(
    xml_reader: &mut NsReader<(impl AsyncBufRead + Unpin)>,
    xml_writer: &mut Writer<(impl AsyncWrite + Unpin)>,
    reader_buf: &mut Vec<u8>,
) -> Result<Authenticated> {
    read_xml_header(xml_reader, reader_buf).await?;
    let _ = ClientStreamStart::parse(xml_reader, reader_buf).await?;

    xml_writer
        .write_event_async(Event::Decl(BytesDecl::new("1.0", None, None)))
        .await?;
    ServerStreamStart {
        from: "localhost".into(),
        lang: "en".into(),
        id: uuid::Uuid::new_v4().to_string(),
        version: "1.0".into(),
    }
    .write_xml(xml_writer)
    .await?;
    Features {
        start_tls: false,
        mechanisms: true,
        bind: false,
    }
    .write_xml(xml_writer)
    .await?;
    xml_writer.get_mut().flush().await?;

    let _ = xmpp::sasl::Auth::parse(xml_reader, reader_buf).await?;
    xmpp::sasl::Success.write_xml(xml_writer).await?;

    let name: Str = "darova".into();
    Ok(Authenticated {
        player_id: PlayerId::from("darova")?,
        xmpp_name: Name(name.clone()),
        xmpp_resource: Resource(name.clone()),
        xmpp_muc_name: Resource(name),
    })
}

async fn socket_final(
    xml_reader: &mut NsReader<(impl AsyncBufRead + Unpin)>,
    xml_writer: &mut Writer<(impl AsyncWrite + Unpin)>,
    reader_buf: &mut Vec<u8>,
    authenticated: &Authenticated,
    user_handle: &mut PlayerConnection,
    rooms: &RoomRegistry,
) -> Result<()> {
    read_xml_header(xml_reader, reader_buf).await?;
    let _ = ClientStreamStart::parse(xml_reader, reader_buf).await?;

    xml_writer
        .write_event_async(Event::Decl(BytesDecl::new("1.0", None, None)))
        .await?;
    ServerStreamStart {
        from: "localhost".into(),
        lang: "en".into(),
        id: uuid::Uuid::new_v4().to_string(),
        version: "1.0".into(),
    }
    .write_xml(xml_writer)
    .await?;
    Features {
        start_tls: false,
        mechanisms: false,
        bind: true,
    }
    .write_xml(xml_writer)
    .await?;
    xml_writer.get_mut().flush().await?;

    let mut parser = proto::ClientPacket::parse();
    let mut events = vec![];
    reader_buf.clear();
    let mut next_xml_event = Box::pin(xml_reader.read_resolved_event_into_async(reader_buf));

    'outer: loop {
        let should_recreate_xml_future = select! {
            biased;
            res = &mut next_xml_event => 's: {
                let (ns, event) = res?;
                if let Event::Text(ref e) = event {
                    if e.iter().all(|x| *x == 0xA) {
                        break 's true;
                    }
                }
                match parser.consume(ns, &event) {
                    Continuation::Final(res) => {
                        let res = res?;
                        let stop = handle_packet(&mut events, res, authenticated, user_handle, rooms).await?;
                        for i in &events {
                            xml_writer.write_event_async(i).await?;
                        }
                        events.clear();
                        xml_writer.get_mut().flush().await?;
                        if stop {
                            break 'outer;
                        }
                        parser = proto::ClientPacket::parse();
                    }
                    Continuation::Continue(p) => parser = p,
                }
                true
            },
            update = user_handle.receiver.recv() => {
                if let Some(update) = update {
                    match update {
                        crate::core::player::Updates::NewMessage { room_id, author_id, body } => {
                            Message {
                                to: Some(Jid {
                                    name: Some(authenticated.xmpp_name.clone()),
                                    server: Server("localhost".into()),
                                    resource: Some(authenticated.xmpp_resource.clone()),
                                }),
                                from: Some(Jid {
                                    name: Some(Name(room_id.into_inner().into())),
                                    server: Server("rooms.localhost".into()),
                                    resource: Some(Resource(author_id.into_inner().into())),
                                }),
                                id: None,
                                r#type: xmpp::client::MessageType::Groupchat,
                                lang: None,
                                subject: None,
                                body: body.into(),
                            }
                            .serialize(&mut events);
                        }
                        _ => {},
                    }
                    for i in &events {
                        xml_writer.write_event_async(i).await?;
                    }
                    events.clear();
                    xml_writer.get_mut().flush().await?;
                } else {
                    log::warn!("Player is terminated, must terminate the connection");
                    break;
                }
                false
            }

        };
        if should_recreate_xml_future {
            drop(next_xml_event);
            next_xml_event = Box::pin(xml_reader.read_resolved_event_into_async(reader_buf));
        }
    }
    Ok(())
}

async fn handle_packet(
    output: &mut Vec<Event<'static>>,
    packet: ClientPacket,
    user: &Authenticated,
    user_handle: &mut PlayerConnection,
    rooms: &RoomRegistry,
) -> Result<bool> {
    Ok(match packet {
        proto::ClientPacket::Iq(iq) => {
            handle_iq(output, iq, rooms).await;
            false
        }
        proto::ClientPacket::Message(m) => {
            if let Some(Jid {
                name: Some(name),
                server,
                resource: _,
            }) = m.to
            {
                if server.0.as_ref() == "rooms.localhost" && m.r#type == MessageType::Groupchat {
                    user_handle
                        .send_message(
                            RoomId::from(name.0.clone())?,
                            m.body.clone().into(),
                        )
                        .await?;
                    Message {
                        to: Some(Jid {
                            name: Some(user.xmpp_name.clone()),
                            server: Server("localhost".into()),
                            resource: Some(user.xmpp_resource.clone()),
                        }),
                        from: Some(Jid {
                            name: Some(name),
                            server: Server("rooms.localhost".into()),
                            resource: Some(user.xmpp_muc_name.clone()),
                        }),
                        id: m.id,
                        r#type: xmpp::client::MessageType::Groupchat,
                        lang: None,
                        subject: None,
                        body: m.body.clone(),
                    }
                    .serialize(output);
                    false
                } else {
                    todo!()
                }
            } else {
                todo!()
            }
        }
        proto::ClientPacket::Presence(p) => {
            let response = if p.to.is_none() {
                Presence::<()> {
                    to: Some(Jid {
                        name: Some(user.xmpp_name.clone()),
                        server: Server("localhost".into()),
                        resource: Some(user.xmpp_resource.clone()),
                    }),
                    from: Some(Jid {
                        name: Some(user.xmpp_name.clone()),
                        server: Server("localhost".into()),
                        resource: Some(user.xmpp_resource.clone()),
                    }),
                    ..Default::default()
                }
            } else if let Some(Jid {
                name: Some(name),
                server,
                resource: Some(resource),
            }) = p.to
            {
                let a = user_handle
                    .join_room(RoomId::from(name.0.clone())?)
                    .await?;
                Presence::<()> {
                    to: Some(Jid {
                        name: Some(user.xmpp_name.clone()),
                        server: Server("localhost".into()),
                        resource: Some(user.xmpp_resource.clone()),
                    }),
                    from: Some(Jid {
                        name: Some(name.clone()),
                        server: Server("rooms.localhost".into()),
                        resource: Some(user.xmpp_muc_name.clone()),
                    }),
                    ..Default::default()
                }
            } else {
                Presence::<()>::default()
            };
            response.serialize(output);
            false
        }
        proto::ClientPacket::StreamEnd => {
            ServerStreamEnd.serialize(output);
            true
        }
    })
}

async fn handle_iq(output: &mut Vec<Event<'static>>, iq: Iq<IqClientBody>, rooms: &RoomRegistry) {
    match iq.body {
        proto::IqClientBody::Bind(b) => {
            let req = Iq {
                from: None,
                id: iq.id,
                to: None,
                r#type: xmpp::client::IqType::Result,
                body: BindResponse(Jid {
                    name: Some(Name("darova".into())),
                    server: Server("localhost".into()),
                    resource: Some(Resource("kek".into())),
                }),
            };
            req.serialize(output);
        }
        proto::IqClientBody::Session(_) => {
            let req = Iq {
                from: None,
                id: iq.id,
                to: None,
                r#type: xmpp::client::IqType::Result,
                body: Session,
            };
            req.serialize(output);
        }
        proto::IqClientBody::Roster(_) => {
            let req = Iq {
                from: None,
                id: iq.id,
                to: None,
                r#type: xmpp::client::IqType::Result,
                body: RosterQuery,
            };
            req.serialize(output);
        }
        proto::IqClientBody::DiscoInfo(info) => {
            let response = disco_info(iq.to.as_deref(), &info);
            let req = Iq {
                from: iq.to,
                id: iq.id,
                to: None,
                r#type: xmpp::client::IqType::Result,
                body: response,
            };
            req.serialize(output);
        }
        proto::IqClientBody::DiscoItem(item) => {
            let response = disco_items(iq.to.as_deref(), &item, rooms).await;
            let req = Iq {
                from: iq.to,
                id: iq.id,
                to: None,
                r#type: xmpp::client::IqType::Result,
                body: response,
            };
            req.serialize(output);
        }
        _ => {
            let req = Iq {
                from: None,
                id: iq.id,
                to: None,
                r#type: xmpp::client::IqType::Error,
                body: (),
            };
            req.serialize(output);
        }
    }
}

fn disco_info(to: Option<&str>, req: &InfoQuery) -> InfoQuery {
    let identity;
    let feature;
    match to {
        Some("localhost") => {
            identity = vec![Identity {
                category: "server".into(),
                name: None,
                r#type: "im".into(),
            }];
            feature = vec![
                Feature::new("http://jabber.org/protocol/disco#info"),
                Feature::new("http://jabber.org/protocol/disco#items"),
                Feature::new("iq"),
                Feature::new("presence"),
            ]
        }
        Some("rooms.localhost") => {
            identity = vec![Identity {
                category: "conference".into(),
                name: Some("Chat rooms".into()),
                r#type: "text".into(),
            }];
            feature = vec![
                Feature::new("http://jabber.org/protocol/disco#info"),
                Feature::new("http://jabber.org/protocol/disco#items"),
                Feature::new("http://jabber.org/protocol/muc"),
            ]
        }
        _ => {
            identity = vec![];
            feature = vec![];
        }
    };
    InfoQuery {
        node: None,
        identity,
        feature,
    }
}

async fn disco_items(to: Option<&str>, req: &ItemQuery, rooms: &RoomRegistry) -> ItemQuery {
    let item = match to {
        Some("localhost") => {
            vec![Item {
                jid: Jid {
                    name: None,
                    server: Server("rooms.localhost".into()),
                    resource: None,
                },
                name: None,
                node: None,
            }]
        }
        Some("rooms.localhost") => {
            let room_list = rooms.get_all_rooms().await;
            room_list
                .into_iter()
                .map(|room_info| Item {
                    jid: Jid {
                        name: Some(Name(room_info.id.into_inner())),
                        server: Server("rooms.localhost".into()),
                        resource: None,
                    },
                    name: None,
                    node: None,
                })
                .collect()
        }
        _ => vec![],
    };
    ItemQuery { item }
}

async fn read_xml_header(
    xml_reader: &mut NsReader<(impl AsyncBufRead + Unpin)>,
    reader_buf: &mut Vec<u8>,
) -> Result<()> {
    if let Event::Decl(bytes) = xml_reader.read_event_into_async(reader_buf).await? {
        // this is <?xml ...> header
        if let Some(encoding) = bytes.encoding() {
            let encoding = encoding?;
            if &*encoding == b"UTF-8" {
                Ok(())
            } else {
                Err(fail(format!("Unsupported encoding: {encoding:?}").as_str()))
            }
        } else {
            // Err(fail("No XML encoding provided"))
            Ok(())
        }
    } else {
        Err(fail("Expected XML header"))
    }
}