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, rsa_private_keys};
use serde::Deserialize;
use tokio::io::{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::PlayerRegistry;
use crate::core::room::RoomRegistry;
use crate::prelude::*;
use crate::protos::xmpp;
use crate::util::Terminator;

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

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

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 keys = rsa_private_keys(&mut SyncBufReader::new(File::open(config.key)?))?;
    let keys = keys.into_iter().map(PrivateKey).collect::<Vec<_>>();

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

    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,
    players: PlayerRegistry,
    rooms: RoomRegistry,
    termination: Deferred<()>, // TODO use it to stop the connection gracefully
) -> Result<()> {
    use xmpp::stream::*;
    log::debug!("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);

    {
        let mut xml_reader = NsReader::from_reader(&mut buf_reader);
        let mut xml_writer = Writer::new(&mut buf_writer);
        let aaa = xml_reader.read_event_into_async(&mut reader_buf).await?;
        if let Event::Decl(_) = aaa {
            // this is <?xml ...> header
        } else {
            return Err(fail("expected XML header"));
        }
        let _ = ClientStreamStart::parse(&mut xml_reader, &mut reader_buf).await?;

        xml_writer
            .write_event_async(Event::Decl(BytesDecl::new("1.0", None, None)))
            .await?;
        xmpp::stream::ServerStreamStart {
            from: "localhost".into(),
            lang: "en".into(),
            version: "1.0".into(),
        }
        .write_xml(&mut xml_writer)
        .await?;
        xmpp::stream::Features {
            start_tls: true,
            mechanisms: false,
            bind: false,
        }
        .write_xml(&mut xml_writer)
        .await?;
        xml_writer.get_mut().flush().await?;

        let StartTLS = StartTLS::parse(&mut xml_reader, &mut reader_buf).await?;
        // TODO read <starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls"/>
        xmpp::stream::Proceed.write_xml(&mut xml_writer).await?;
        xml_writer.get_mut().flush().await?;
    }

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

    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 buf_reader = BufReader::new(a);

    let mut xml_reader = NsReader::from_reader(buf_reader);
    let mut xml_writer = Writer::new(b);

    {
        if let Event::Decl(_) = xml_reader.read_event_into_async(&mut reader_buf).await? {
            // this is <?xml ...> header
        } else {
            return Err(fail("expected XML header"));
        }
        let _ = ClientStreamStart::parse(&mut xml_reader, &mut reader_buf).await?;

        xml_writer
            .write_event_async(Event::Decl(BytesDecl::new("1.0", None, None)))
            .await?;
        xmpp::stream::ServerStreamStart {
            from: "localhost".into(),
            lang: "en".into(),
            version: "1.0".into(),
        }
        .write_xml(&mut xml_writer)
        .await?;
        xmpp::stream::Features {
            start_tls: false,
            mechanisms: true,
            bind: false,
        }
        .write_xml(&mut xml_writer)
        .await?;
        xml_writer.get_mut().flush().await?;

        let _ = xmpp::sasl::Auth::parse(&mut xml_reader, &mut reader_buf).await?;
        xmpp::sasl::Success.write_xml(&mut xml_writer).await?;
    }
    {
        if let Event::Decl(_) = xml_reader.read_event_into_async(&mut reader_buf).await? {
            // this is <?xml ...> header
        } else {
            return Err(fail("expected XML header"));
        }
        let _ = ClientStreamStart::parse(&mut xml_reader, &mut reader_buf).await?;

        xml_writer
            .write_event_async(Event::Decl(BytesDecl::new("1.0", None, None)))
            .await?;
        xmpp::stream::ServerStreamStart {
            from: "localhost".into(),
            lang: "en".into(),
            version: "1.0".into(),
        }
        .write_xml(&mut xml_writer)
        .await?;
        xmpp::stream::Features {
            start_tls: false,
            mechanisms: false,
            bind: true,
        }
        .write_xml(&mut xml_writer)
        .await?;
        xml_writer.get_mut().flush().await?;
    }
    loop {
        let event = xml_reader.read_event_into_async(&mut reader_buf).await?;
        println!("EVENT: {event:?}");
        if event == Event::Eof {
            break;
        }
    }

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