use std::net::SocketAddr;

use prometheus::{IntCounter, IntGauge, Registry as MetricsRegistry};
use serde::Deserialize;
use tokio::io::{AsyncBufReadExt, AsyncWrite, AsyncWriteExt, BufReader, BufWriter};
use tokio::net::tcp::{ReadHalf, WriteHalf};
use tokio::net::{TcpListener, TcpStream};
use tokio::sync::oneshot::channel;

use crate::core::player::{ConnectionId, PlayerHandle, PlayerId, PlayerRegistry, Updates};
use crate::core::room::RoomId;
use crate::prelude::*;
use crate::protos::irc::client::{client_message, ClientMessage};
use crate::protos::irc::server::{ServerMessage, ServerMessageBody};
use crate::protos::irc::{Chan, Recipient};
use crate::util::Terminator;

#[derive(Deserialize, Debug, Clone)]
pub struct ServerConfig {
    pub listen_on: SocketAddr,
    pub server_name: String,
}

#[derive(Debug)]
struct RegisteredUser {
    nickname: Vec<u8>,
    username: Vec<u8>,
    realname: Vec<u8>,
}

async fn handle_socket(
    config: ServerConfig,
    mut stream: TcpStream,
    socket_addr: SocketAddr,
    mut players: PlayerRegistry,
) -> Result<()> {
    let (reader, writer) = stream.split();
    let mut reader: BufReader<ReadHalf> = BufReader::new(reader);
    let mut writer = BufWriter::new(writer);

    ServerMessage {
        tags: vec![],
        sender: Some(config.server_name.as_bytes().to_vec()),
        body: ServerMessageBody::Notice {
            first_target: b"*".to_vec(),
            rest_targets: vec![],
            text: b"Welcome to my server!".to_vec(),
        },
    }
    .write_async(&mut writer)
    .await?;
    writer.flush().await?;

    let registered_user: Result<RegisteredUser> =
        handle_registration(&mut reader, &mut writer).await;
    match registered_user {
        Ok(user) => {
            handle_registered_socket(config, socket_addr, players, &mut reader, &mut writer, user)
                .await?;
        }
        Err(_) => {}
    }

    stream.shutdown().await?;
    Ok(())
}

async fn handle_registration<'a>(
    reader: &mut BufReader<ReadHalf<'a>>,
    writer: &mut BufWriter<WriteHalf<'a>>,
) -> Result<RegisteredUser> {
    let mut buffer = vec![];

    let mut future_nickname: Option<Vec<u8>> = None;
    let mut future_username: Option<(Vec<u8>, Vec<u8>)> = None;

    loop {
        let res = reader.read_until(b'\n', &mut buffer).await;
        match res {
            Ok(len) => {
                if len == 0 {
                    log::info!("Terminating socket");
                    break Err(anyhow::Error::msg("EOF"));
                }
            }
            Err(err) => {
                log::warn!("Failed to read from socket: {err}");
                break Err(err.into());
            }
        }
        let parsed = client_message(&buffer[..]);
        match parsed {
            Ok((rest, msg)) => {
                log::info!("Incoming IRC message: {msg:?}");
                match msg {
                    ClientMessage::Nick { nickname } => {
                        if let Some((username, realname)) = future_username {
                            break Ok(RegisteredUser {
                                nickname,
                                username,
                                realname,
                            });
                        } else {
                            future_nickname = Some(nickname);
                        }
                    }
                    ClientMessage::User { username, realname } => {
                        if let Some(nickname) = future_nickname {
                            break Ok(RegisteredUser {
                                nickname,
                                username,
                                realname,
                            });
                        } else {
                            future_username = Some((username, realname));
                        }
                    }
                    _ => {}
                }
            }
            Err(err) => {
                log::warn!("Failed to parse IRC message: {err}");
            }
        }
        buffer.clear();
    }
}

async fn handle_registered_socket<'a>(
    config: ServerConfig,
    socket_addr: SocketAddr,
    mut players: PlayerRegistry,
    reader: &mut BufReader<ReadHalf<'a>>,
    writer: &mut BufWriter<WriteHalf<'a>>,
    user: RegisteredUser,
) -> Result<()> {
    let mut buffer = vec![];
    log::info!("Handling registered user: {user:?}");

    let mut user_handle = players
        .get_or_create_player(PlayerId(user.nickname.clone()))
        .await;
    let (my_connection_id, mut connnection) = user_handle.subscribe().await;

    ServerMessage {
        tags: vec![],
        sender: Some(config.server_name.as_bytes().to_vec()),
        body: ServerMessageBody::N001Welcome {
            client: user.nickname.clone(),
            text: b"Welcome to Kek Server".to_vec(),
        },
    }
    .write_async(writer)
    .await?;
    ServerMessage {
        tags: vec![],
        sender: Some(config.server_name.as_bytes().to_vec()),
        body: ServerMessageBody::N002YourHost {
            client: user.nickname.clone(),
            text: b"Welcome to Kek Server".to_vec(),
        },
    }
    .write_async(writer)
    .await?;
    ServerMessage {
        tags: vec![],
        sender: Some(config.server_name.as_bytes().to_vec()),
        body: ServerMessageBody::N003Created {
            client: user.nickname.clone(),
            text: b"Welcome to Kek Server".to_vec(),
        },
    }
    .write_async(writer)
    .await?;
    ServerMessage {
        tags: vec![],
        sender: Some(config.server_name.as_bytes().to_vec()),
        body: ServerMessageBody::N004MyInfo {
            client: user.nickname.clone(),
            hostname: config.server_name.as_bytes().to_vec(),
            softname: b"kek-0.1.alpha.3".to_vec(),
        },
    }
    .write_async(writer)
    .await?;
    ServerMessage {
        tags: vec![],
        sender: Some(config.server_name.as_bytes().to_vec()),
        body: ServerMessageBody::N005ISupport {
            client: user.nickname.clone(),
            params: b"CHANTYPES=#".to_vec(),
        },
    }
    .write_async(writer)
    .await?;
    writer.flush().await?;

    loop {
        select! {
            biased;
            len = reader.read_until(b'\n', &mut buffer) => {
                let len = len?;
                let len = if len == 0 {
                    log::info!("EOF, Terminating socket");
                    break;
                } else {
                    len
                };
                handle_incoming_message(&buffer[0..len], &config, &user, &mut user_handle, &my_connection_id, writer).await?;
                buffer.clear();
            },
            update = connnection.recv() => {
                match update.unwrap() {
                    Updates::RoomJoined { room_id } => {},
                    Updates::NewMessage { author_id, connection_id, room_id, body } => {
                        if my_connection_id != connection_id {
                            ServerMessage {
                                tags: vec![],
                                sender: Some(author_id.0.clone()),
                                body: ServerMessageBody::PrivateMessage { target: Recipient::Chan(Chan::Global(room_id.0)), body: body.as_bytes().to_vec() }
                            }.write_async(writer).await?;
                            writer.flush().await?
                        }
                    },
                }
            }
        }
    }
    Ok(())
}

async fn handle_incoming_message(
    buffer: &[u8],
    config: &ServerConfig,
    user: &RegisteredUser,
    user_handle: &mut PlayerHandle,
    my_connection_id: &ConnectionId,
    writer: &mut (impl AsyncWrite + Unpin),
) -> Result<()> {
    let parsed = client_message(buffer);
    match parsed {
        Ok((rest, msg)) => match msg {
            ClientMessage::Ping { token } => {
                ServerMessage {
                    tags: vec![],
                    sender: None,
                    body: ServerMessageBody::Pong {
                        from: config.server_name.as_bytes().to_vec(),
                        token,
                    },
                }
                .write_async(writer)
                .await?;
                writer.flush().await?;
            }
            ClientMessage::Join(ref chan) => {
                handle_join(&config, &user, user_handle, chan, writer).await?;
            }
            ClientMessage::PrivateMessage { recipient, body } => match recipient {
                Recipient::Chan(Chan::Global(room)) => match String::from_utf8(body) {
                    Ok(body) => {
                        user_handle
                            .send_message(
                                RoomId(room.clone()),
                                my_connection_id.clone(),
                                body.clone(),
                            )
                            .await
                    }
                    Err(err) => log::warn!("failed to parse incoming message: {err}"),
                },
                _ => log::warn!("Unsupported target type"),
            },
            _ => {}
        },
        Err(err) => {
            log::warn!("Failed to parse IRC message: {err}");
        }
    }
    Ok(())
}

async fn handle_join(
    config: &ServerConfig,
    user: &RegisteredUser,
    user_handle: &mut PlayerHandle,
    chan: &Chan,
    writer: &mut (impl AsyncWrite + Unpin),
) -> Result<()> {
    match chan {
        Chan::Global(ref room) => {
            user_handle.join_room(RoomId(room.clone())).await;
            ServerMessage {
                tags: vec![],
                sender: Some(user.nickname.clone()),
                body: ServerMessageBody::Join(chan.clone()),
            }
            .write_async(writer)
            .await?;
            ServerMessage {
                tags: vec![],
                sender: Some(config.server_name.as_bytes().to_vec()),
                body: ServerMessageBody::N332Topic {
                    client: user.nickname.clone(),
                    chat: chan.clone(),
                    topic: b"chan topic lol".to_vec(),
                },
            }
            .write_async(writer)
            .await?;
            ServerMessage {
                tags: vec![],
                sender: Some(config.server_name.as_bytes().to_vec()),
                body: ServerMessageBody::N353NamesReply {
                    client: user.nickname.clone(),
                    chan: chan.clone(),
                    members: user.nickname.clone(),
                },
            }
            .write_async(writer)
            .await?;
            ServerMessage {
                tags: vec![],
                sender: Some(config.server_name.as_bytes().to_vec()),
                body: ServerMessageBody::N366NamesReplyEnd {
                    client: user.nickname.clone(),
                    chan: chan.clone(),
                },
            }
            .write_async(writer)
            .await?;

            writer.flush().await?;
        }
        Chan::Local(_) => {}
    };
    Ok(())
}

pub async fn launch(
    config: ServerConfig,
    players: PlayerRegistry,
    metrics: MetricsRegistry,
) -> Result<Terminator> {
    log::info!("Starting IRC projection");
    let (signal, mut rx) = channel();
    let current_connections =
        IntGauge::new("irc_current_connections", "Open and alive TCP connections")?;
    let total_connections = IntCounter::new(
        "irc_total_connections",
        "Total number of opened connections",
    )?;
    metrics.register(Box::new(current_connections.clone()))?;
    metrics.register(Box::new(total_connections.clone()))?;

    let listener = TcpListener::bind(config.listen_on).await?;
    log::debug!("Listener started");

    let handle = tokio::task::spawn(async move {
        loop {
            select! {
                biased;
                _ = &mut rx => break,
                new_conn = listener.accept() => {
                    match new_conn {
                        Ok((stream, socket_addr)) => {
                            let config = config.clone();
                            total_connections.inc();
                            current_connections.inc();
                            log::debug!("Incoming connection from {socket_addr}");
                            let players_clone = players.clone();
                            let current_connections_clone = current_connections.clone();
                            let handle = tokio::task::spawn(async move {
                                match handle_socket(config, stream, socket_addr, players_clone).await {
                                    Ok(_) => log::info!("Connection terminated"),
                                    Err(err) => log::warn!("Connection failed: {err}"),
                                }
                                current_connections_clone.dec();
                            });
                        },
                        Err(err) => log::warn!("Failed to accept new connection: {err}"),
                    }
                },
            }
        }

        log::info!("Stopping IRC projection");
        Ok(())
    });

    let terminator = Terminator::from_raw(signal, handle);
    Ok(terminator)
}