use bytes::{Buf, Bytes};

use log::*;

use slab::Slab;

use std::{

    iter::Iterator,

    time::Duration,

};

use tokio::{

    io::AsyncReadExt,

    net::{TcpListener, TcpStream},

    sync::mpsc::{channel, Receiver, Sender},

};

use crate::{

    core::{

        events::{TimedEvents, Timeout},

        types::ClientId,

    },

    handlers,

    handlers::{IoResult, IoTask, ServerState},

    utils,

};

use hedgewars_network_protocol::{

    messages::HwServerMessage::Redirect, messages::*, parser::server_message,

};

use tokio::io::AsyncWriteExt;

enum ClientUpdateData {

    Message(HwProtocolMessage),

    Error(String),

}

struct ClientUpdate {

    client_id: ClientId,

    data: ClientUpdateData,

}

struct ClientUpdateSender {

    client_id: ClientId,

    sender: Sender<ClientUpdate>,

}

impl ClientUpdateSender {

    async fn send(&mut self, data: ClientUpdateData) -> bool {

        self.sender

            .send(ClientUpdate {

                client_id: self.client_id,

                data,

            })

            .await

            .is_ok()

    }

}

struct NetworkClient {

    id: ClientId,

    socket: TcpStream,

    receiver: Receiver<Bytes>,

    peer_addr: SocketAddr,

    decoder: ProtocolDecoder,

}

impl NetworkClient {

    fn new(

        id: ClientId,

        socket: TcpStream,

        peer_addr: SocketAddr,

        receiver: Receiver<Bytes>,

    ) -> Self {

        Self {

            id,

            socket,

            peer_addr,

            receiver,

        }

    }

    }

    }

    async fn run(mut self, sender: Sender<ClientUpdate>) {

        use ClientUpdateData::*;

        let mut sender = ClientUpdateSender {

            client_id: self.id,

            sender,

        };

        loop {

            tokio::select! {

                server_message = self.receiver.recv() => {

                    match server_message {

                            sender.send(Error("Connection reset by peer".to_string())).await;

                            break;

                        }

                        None => {

                            break;

                        }

                    }

                }

                     match client_message {

                            if !sender.send(Message(message)).await {

                                break;

                            }

                        }

                            break;

                        }

                    }

                }

            }

        }

    }

}

pub struct NetworkLayer {

    listener: TcpListener,

    server_state: ServerState,

    clients: Slab<Sender<Bytes>>,

}

impl NetworkLayer {

    pub async fn run(&mut self) {

        let (update_tx, mut update_rx) = channel(128);

        loop {

            tokio::select! {

                Ok((stream, addr)) = self.listener.accept() => {

                    if let Some(client) = self.create_client(stream, addr).await {

                        tokio::spawn(client.run(update_tx.clone()));

                    }

                }

                client_message = update_rx.recv(), if !self.clients.is_empty() => {

                    use ClientUpdateData::*;

                    match client_message {

                        Some(ClientUpdate{ client_id, data: Message(message) } ) => {

                            self.handle_message(client_id, message).await;

                        }

                            let mut response = handlers::Response::new(client_id);

                            handlers::handle_client_loss(&mut self.server_state, client_id, &mut response);

                            self.handle_response(response).await;

                        }

                        None => unreachable!()

                    }

                }

            }

        }

    }

    async fn create_client(

        &mut self,

        stream: TcpStream,

        addr: SocketAddr,

    ) -> Option<NetworkClient> {

        let entry = self.clients.vacant_entry();

        let client_id = entry.key();

        let (tx, rx) = channel(16);

        entry.insert(tx);

        let client = NetworkClient::new(client_id, stream, addr, rx);

        info!("client {} ({}) added", client.id, client.peer_addr);

        let mut response = handlers::Response::new(client_id);

        let added = if let IpAddr::V4(addr) = client.peer_addr.ip() {

            handlers::handle_client_accept(

                &mut self.server_state,

                client_id,

                &mut response,

                addr.octets(),

                addr.is_loopback(),

            )

        } else {

            todo!("implement something")

        };

        self.handle_response(response).await;

        if added {

            Some(client)

        } else {

            None

        }

    }

    async fn handle_message(&mut self, client_id: ClientId, message: HwProtocolMessage) {

        debug!("Handling message {:?} for client {}", message, client_id);

        let mut response = handlers::Response::new(client_id);

        handlers::handle(&mut self.server_state, client_id, &mut response, message);

        self.handle_response(response).await;

    }

    async fn handle_response(&mut self, mut response: handlers::Response) {

        if response.is_empty() {

            return;

        }

        debug!("{} pending server messages", response.len());

        let output = response.extract_messages(&mut self.server_state.server);

        for (clients, message) in output {

            debug!("Message {:?} to {:?}", message, clients);

            Self::send_message(&mut self.clients, message, clients.iter().cloned()).await;

        }

        for client_id in response.extract_removed_clients() {

            if self.clients.contains(client_id) {

                self.clients.remove(client_id);

            }

            info!("Client {} removed", client_id);

        }

    }

    async fn send_message<I>(

        clients: &mut Slab<Sender<Bytes>>,

        message: HwServerMessage,

        to_clients: I,

    ) where

        I: Iterator<Item = ClientId>,

    {

        let msg_string = message.to_raw_protocol();

        let bytes = Bytes::copy_from_slice(msg_string.as_bytes());

        for client_id in to_clients {

            if let Some(client) = clients.get_mut(client_id) {

                if !client.send(bytes.clone()).await.is_ok() {

                    clients.remove(client_id);

                }

            }

        }

    }

}

pub struct NetworkLayerBuilder {

    listener: Option<TcpListener>,

    clients_capacity: usize,

    rooms_capacity: usize,

}

impl Default for NetworkLayerBuilder {

    fn default() -> Self {

        Self {

            clients_capacity: 1024,

            rooms_capacity: 512,

            listener: None,

        }

    }

}

impl NetworkLayerBuilder {

    pub fn with_listener(self, listener: TcpListener) -> Self {

        Self {

            listener: Some(listener),

            ..self

        }

    }

    pub fn build(self) -> NetworkLayer {

        let server_state = ServerState::new(self.clients_capacity, self.rooms_capacity);

        let clients = Slab::with_capacity(self.clients_capacity);

        NetworkLayer {

            listener: self.listener.expect("No listener provided"),

            server_state,

            clients,

        }

    }

}