#![feature(coroutines, coroutine_trait, type_alias_impl_trait, impl_trait_in_assoc_type)]

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 anyhow::anyhow;
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 lavina_core::player::{PlayerConnection, PlayerId, PlayerRegistry};
use lavina_core::prelude::*;
use lavina_core::repo::Storage;
use lavina_core::room::RoomRegistry;
use lavina_core::terminator::Terminator;
use proto_xmpp::bind::{Name, Resource};
use proto_xmpp::stream::*;
use proto_xmpp::xml::{Continuation, FromXml, Parser, ToXml};
use sasl::AuthBody;

use self::proto::ClientPacket;

mod iq;
mod message;
mod presence;
mod updates;

#[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 struct RunningServer {
    pub addr: SocketAddr,
    terminator: Terminator,
}

impl RunningServer {
    pub async fn terminate(self) -> Result<()> {
        self.terminator.terminate().await
    }
}

pub async fn launch(
    config: ServerConfig,
    players: PlayerRegistry,
    rooms: RoomRegistry,
    metrics: MetricsRegistry,
    storage: Storage,
) -> Result<RunningServer> {
    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),
        _ => return Err(fail("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 addr = listener.local_addr()?;

    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 storage = storage.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, storage, 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(RunningServer { addr, terminator })
}

async fn handle_socket(
    config: Arc<LoadedConfig>,
    mut stream: TcpStream,
    socket_addr: &SocketAddr,
    mut players: PlayerRegistry,
    rooms: RoomRegistry,
    mut storage: Storage,
    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());

    log::debug!("Accepting TLS connection...");
    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, &mut storage).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 proto_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>,
    storage: &mut Storage,
) -> 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 auth: proto_xmpp::sasl::Auth = proto_xmpp::sasl::Auth::parse(xml_reader, reader_buf).await?;
    proto_xmpp::sasl::Success.write_xml(xml_writer).await?;

    match AuthBody::from_str(&auth.body) {
        Ok(logopass) => {
            let name = &logopass.login;
            let stored_user = storage.retrieve_user_by_name(name).await?;

            let stored_user = match stored_user {
                Some(u) => u,
                None => {
                    log::info!("User '{}' not found", name);
                    return Err(fail("no user found"));
                }
            };
            // TODO return proper XML errors to the client

            if stored_user.password.is_none() {
                log::info!("Password not defined for user '{}'", name);
                return Err(fail("password is not defined"));
            }
            if stored_user.password.as_deref() != Some(&logopass.password) {
                log::info!("Incorrect password supplied for user '{}'", name);
                return Err(fail("passwords do not match"));
            }

            Ok(Authenticated {
                player_id: PlayerId::from(name.as_str())?,
                xmpp_name: Name(name.to_string().into()),
                xmpp_resource: Resource(name.to_string().into()),
                xmpp_muc_name: Resource(name.to_string().into()),
            })
        }
        Err(e) => return Err(e),
    }
}

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 mut conn = XmppConnection {
            user: authenticated,
            user_handle,
            rooms,
        };
        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 = conn.handle_packet(&mut events, res).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 = conn.user_handle.receiver.recv() => {
                if let Some(update) = update {
                    conn.handle_update(&mut events, update).await?;
                    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(())
}

struct XmppConnection<'a> {
    user: &'a Authenticated,
    user_handle: &'a mut PlayerConnection,
    rooms: &'a RoomRegistry,
}

impl<'a> XmppConnection<'a> {
    async fn handle_packet(&mut self, output: &mut Vec<Event<'static>>, packet: ClientPacket) -> Result<bool> {
        let res = match packet {
            proto::ClientPacket::Iq(iq) => {
                self.handle_iq(output, iq).await;
                false
            }
            ClientPacket::Message(m) => {
                self.handle_message(output, m).await?;
                false
            }
            proto::ClientPacket::Presence(p) => {
                self.handle_presence(output, p).await?;
                false
            }
            proto::ClientPacket::StreamEnd => {
                ServerStreamEnd.serialize(output);
                true
            }
        };
        Ok(res)
    }
}

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(anyhow!("Unsupported encoding: {encoding:?}"))
            }
        } else {
            // Err(fail("No XML encoding provided"))
            Ok(())
        }
    } else {
        Err(anyhow!("Expected XML header"))
    }
}