use std::error::Error;
use std::net::SocketAddr;
use futures::stream::{SplitSink, SplitStream};
use futures::{FutureExt, SinkExt, StreamExt};
use hyper::upgrade::Upgraded;
use log::{error, info};
use tokio::sync::mpsc::Receiver;
use tokio_tungstenite::WebSocketStream;
use tungstenite::Message;
use protocol::{GoodbyeReason, MessageC2S, MessageS2C, PROTOCOL_VERSION, ps2c, recv, send, State};
use crate::handler::{ClientHandlerMessage, ClientManager};

pub async fn handle_client(mgr: ClientManager, remote_addr: SocketAddr, mut rx: Receiver<ClientHandlerMessage>, mut client_tx: SplitSink<WebSocketStream<Upgraded>, Message>, mut client_rx: SplitStream<WebSocketStream<Upgraded>>) -> Result<(), Box<dyn Error>> {
    let mut state = State::Handshake;

    loop {
        if let Some(msg) = rx.recv().await {
            match msg {
                ClientHandlerMessage::Tick => {} // this intentionally does nothing
            }
        } else {
            info!("channel closed, shutting down");
            break;
        }

        if let Some(pkt) = recv!(client_rx)? {
            match state {
                State::Handshake => {
                    match pkt {
                        MessageC2S::Hello { version, requested_username, next_state } => {
                            if !matches!(next_state, State::Play) {
                                error!("client sent unexpected state {:?} (expected: Play)", next_state);
                                send!(client_tx, &MessageS2C::Goodbye {
                                        reason: GoodbyeReason::UnexpectedNextState,
                                    }).await?;
                                break;
                            }

                            // check version
                            if version != PROTOCOL_VERSION {
                                error!("client sent incompatible version {} (expected: {})", version, PROTOCOL_VERSION);
                                send!(client_tx, &MessageS2C::Goodbye {
                                        reason: GoodbyeReason::UnsupportedProtocol {
                                            supported: PROTOCOL_VERSION,
                                            got: version,
                                        },
                                    }).await?;
                                break;
                            }

                            // determine if we can give them that username
                            {
                                if mgr.usernames.read().await.values().any(|u| *u == requested_username) {
                                    error!("client requested username {} but it is in use", requested_username);
                                    send!(client_tx, &MessageS2C::Goodbye {
                                            reason: GoodbyeReason::UsernameTaken,
                                        }).await?;
                                    break;
                                }
                            }

                            // username is fine
                            {
                                mgr.usernames.write().await.insert(remote_addr, requested_username.clone());
                            }

                            send!(client_tx, &MessageS2C::Hello {
                                    version,
                                    given_username: requested_username,
                                    next_state,
                                }).await?;
                        },
                        MessageC2S::Goodbye { reason } => {
                            info!("client sent goodbye: {:?}", reason);
                            break;
                        }
                    }
                }
                State::Play => {
                    match pkt {
                        MessageC2S::Hello { .. } => {
                            error!("client sent unexpected packet {:?} for state {:?}", pkt, state);
                            send!(client_tx, &MessageS2C::Goodbye {
                                    reason: GoodbyeReason::UnexpectedPacket,
                                }).await?;
                            break;
                        }
                        MessageC2S::Goodbye { reason } => {
                            info!("client sent goodbye: {:?}", reason);
                            break;
                        }
                    }
                }
            }
        }
    }

    Ok(())
}