pub mod error;

use crate::client::error::{MessageError, RequestError};
use crate::messages::callback::GenericCallbackError;
use crate::messages::payload::RequestMessagePayload;
use crate::messages::payload::ResponseMessagePayload;
use crate::messages::{
    ClientMessage, RegisterCallback, RequestMessage, RequestResponse, ResponseMessage,
};
use error::ConnectError;
use futures_util::stream::StreamExt;
use futures_util::SinkExt;
use log::{debug, error, warn};
use std::collections::HashMap;
use std::sync::mpsc::sync_channel;
use std::sync::Arc;
use std::thread;
use tokio::net::TcpStream;
use tokio::sync::{mpsc, oneshot, RwLock, RwLockWriteGuard};
use tokio::{select, spawn};
use tokio_tungstenite::tungstenite::client::IntoClientRequest;
use tokio_tungstenite::tungstenite::handshake::client::Request;
use tokio_tungstenite::tungstenite::Message;
use tokio_tungstenite::{connect_async, MaybeTlsStream, WebSocketStream};
use tokio_util::sync::CancellationToken;
use uuid::Uuid;

type RegisteredCallback = mpsc::Sender<(ResponseMessage, oneshot::Sender<RequestMessagePayload>)>;
type ClientChannel = Arc<RwLock<mpsc::Sender<OutgoingMessage>>>;

enum Callback {
    None,
    Once(oneshot::Sender<ResponseMessage>),
    Registered(RegisteredCallback),
}

struct OutgoingMessage {
    msg: RequestMessage,
    callback: Callback,
}

pub struct Client {
    cancel: CancellationToken,
    channel: ClientChannel,
}

struct ClientContext {
    cancel: CancellationToken,
    request: Request,
}

impl Client {
    pub fn connect<R>(request: R) -> Result<Self, ConnectError>
    where
        R: IntoClientRequest,
    {
        let (tx, _rx) = mpsc::channel(1);
        let cancel = CancellationToken::new();
        let channel = Arc::new(RwLock::new(tx));
        let context = ClientContext {
            cancel: cancel.clone(),
            request: request.into_client_request()?,
        };

        context.start(channel.clone())?;

        Ok(Self { cancel, channel })
    }

    pub async fn send_message<M: ClientMessage>(&self, msg: M) -> Result<(), MessageError> {
        let sender = self.channel.read().await;
        let data = sender.reserve().await?;
        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: None,
                payload: msg.into(),
            },
            callback: Callback::None,
        });
        Ok(())
    }

    pub async fn send_message_if_connected<M: ClientMessage>(
        &self,
        msg: M,
    ) -> Result<(), MessageError> {
        let sender = self.channel.try_read()?;
        let data = sender.reserve().await?;
        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: None,
                payload: msg.into(),
            },
            callback: Callback::None,
        });
        Ok(())
    }

    pub fn try_send_message<M: ClientMessage>(&self, msg: M) -> Result<(), MessageError> {
        let sender = self.channel.try_read()?;
        let data = sender.try_reserve()?;
        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: None,
                payload: msg.into(),
            },
            callback: Callback::None,
        });
        Ok(())
    }

    pub async fn send_request<M: RequestResponse>(
        &self,
        msg: M,
    ) -> Result<M::Response, RequestError<<M::Response as TryFrom<ResponseMessagePayload>>::Error>>
    {
        let sender = self.channel.read().await;
        let data = sender.reserve().await?;

        let (tx, rx) = oneshot::channel();
        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: None,
                payload: msg.into(),
            },
            callback: Callback::Once(tx),
        });

        let response = rx.await?;
        let response = M::Response::try_from(response.payload).map_err(RequestError::Inner)?;

        Ok(response)
    }

    pub async fn register_callback_channel<M: RegisterCallback>(
        &self,
        msg: M,
    ) -> Result<mpsc::Receiver<(M::Callback, oneshot::Sender<M::Response>)>, MessageError>
    where
        <M as RegisterCallback>::Callback: Send + 'static,
        <M as RegisterCallback>::Response: Send + 'static,
        <<M as RegisterCallback>::Callback as TryFrom<ResponseMessagePayload>>::Error: Send,
    {
        let sender = self.channel.read().await;
        let data = sender.reserve().await?;

        let (inner_tx, mut inner_rx) = mpsc::channel(16);
        let (outer_tx, outer_rx) = mpsc::channel(1);

        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: None,
                payload: msg.into(),
            },
            callback: Callback::Registered(inner_tx),
        });

        spawn(async move {
            // If the handler was unregistered we can stop
            while let Some((msg, responder)) = inner_rx.recv().await {
                let response: RequestMessagePayload = match M::Callback::try_from(msg.payload) {
                    Err(_) => GenericCallbackError::MismatchedType.into(),
                    Ok(o) => {
                        let (response_tx, response_rx) = oneshot::channel::<M::Response>();
                        match outer_tx.send((o, response_tx)).await {
                            Err(_) => GenericCallbackError::CallbackClosed.into(),
                            Ok(()) => response_rx
                                .await
                                .map(M::Response::into)
                                .unwrap_or_else(|_| GenericCallbackError::CallbackClosed.into()),
                        }
                    }
                };

                if responder.send(response).is_err() {
                    // If the callback was unregistered we can stop
                    break;
                }
            }
        });

        Ok(outer_rx)
    }

    pub async fn register_callback_fn<M: RegisterCallback, F>(
        &self,
        msg: M,
        mut f: F,
    ) -> Result<(), MessageError>
    where
        F: FnMut(M::Callback) -> M::Response + Send + 'static,
    {
        let sender = self.channel.read().await;
        let data = sender.reserve().await?;

        let (inner_tx, mut inner_rx) = mpsc::channel(16);

        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: None,
                payload: msg.into(),
            },
            callback: Callback::Registered(inner_tx),
        });

        spawn(async move {
            // If the handler was unregistered we can stop
            while let Some((msg, responder)) = inner_rx.recv().await {
                let response: RequestMessagePayload = match M::Callback::try_from(msg.payload) {
                    Err(_) => GenericCallbackError::MismatchedType.into(),
                    Ok(o) => f(o).into(),
                };

                if responder.send(response).is_err() {
                    // If the callback was unregistered we can stop
                    break;
                }
            }
        });

        Ok(())
    }
}

impl ClientContext {
    fn start(mut self, channel: ClientChannel) -> Result<(), ConnectError> {
        let runtime = tokio::runtime::Builder::new_current_thread()
            .enable_all()
            .build()?;

        let (tx, rx) = sync_channel::<()>(1);

        let _detached = thread::Builder::new()
            .name("tlm-client".to_string())
            .spawn(move || {
                runtime.block_on(async {
                    let mut write_lock = channel.write().await;

                    // This cannot fail
                    let _ = tx.send(());

                    while !self.cancel.is_cancelled() {
                        write_lock = self.run_connection(write_lock, &channel).await;
                    }
                    drop(write_lock);
                });
            })?;

        // This cannot fail
        let _ = rx.recv();

        Ok(())
    }

    async fn run_connection<'a>(
        &mut self,
        mut write_lock: RwLockWriteGuard<'a, mpsc::Sender<OutgoingMessage>>,
        channel: &'a ClientChannel,
    ) -> RwLockWriteGuard<'a, mpsc::Sender<OutgoingMessage>> {
        let mut ws = match connect_async(self.request.clone()).await {
            Ok((ws, _)) => ws,
            Err(e) => {
                error!("Connect Error: {e}");
                return write_lock;
            }
        };

        let (tx, rx) = mpsc::channel(128);
        *write_lock = tx;
        drop(write_lock);

        let close_connection = self.handle_connection(&mut ws, rx, channel).await;

        let write_lock = channel.write().await;
        if close_connection {
            if let Err(e) = ws.close(None).await {
                println!("Close Error {e}");
            }
        }
        write_lock
    }

    async fn handle_connection(
        &mut self,
        ws: &mut WebSocketStream<MaybeTlsStream<TcpStream>>,
        mut rx: mpsc::Receiver<OutgoingMessage>,
        channel: &ClientChannel,
    ) -> bool {
        let mut callbacks = HashMap::<Uuid, Callback>::new();
        loop {
            select! {
                _ = self.cancel.cancelled() => { break; },
                Some(msg) = ws.next() => {
                    match msg {
                        Ok(msg) => {
                            match msg {
                                Message::Text(msg) => {
                                    let msg: ResponseMessage = match serde_json::from_str(&msg) {
                                        Ok(m) => m,
                                        Err(e) => {
                                            error!("Failed to deserialize {e}");
                                            break;
                                        }
                                    };
                                    self.handle_incoming(msg, &mut callbacks, channel).await;
                                }
                                Message::Binary(_) => unimplemented!("Binary Data Not Implemented"),
                                Message::Ping(data) => {
                                    if let Err(e) = ws.send(Message::Pong(data)).await {
                                        error!("Failed to send Pong {e}");
                                        break;
                                    }
                                }
                                Message::Pong(_) => {
                                    // Intentionally Left Empty
                                }
                                Message::Close(_) => {
                                    debug!("Websocket Closed");
                                    return false;
                                }
                                Message::Frame(_) => unreachable!("Not Possible"),
                            }
                        }
                        Err(e) => {
                            error!("Receive Error {e}");
                            break;
                        }
                    }
                }
                Some(msg) = rx.recv() => {
                    // Insert a callback if it isn't a None callback
                    if !matches!(msg.callback, Callback::None) {
                        callbacks.insert(msg.msg.uuid, msg.callback);
                    }
                    let msg = match serde_json::to_string(&msg.msg) {
                        Ok(m) => m,
                        Err(e) => {
                            error!("Encode Error {e}");
                            break;
                        }
                    };
                    if let Err(e) = ws.send(Message::Text(msg.into())).await {
                        error!("Send Error {e}");
                        break;
                    }
                }
                else => { break; },
            }
        }
        true
    }

    async fn handle_incoming(
        &mut self,
        msg: ResponseMessage,
        callbacks: &mut HashMap<Uuid, Callback>,
        channel: &ClientChannel,
    ) {
        if let Some(response_uuid) = msg.response {
            match callbacks.get(&response_uuid) {
                Some(Callback::None) => {
                    callbacks.remove(&response_uuid);
                    unreachable!("We skip registering callbacks of None type");
                }
                Some(Callback::Once(_)) => {
                    let Some(Callback::Once(callback)) = callbacks.remove(&response_uuid) else {
                        return;
                    };
                    let _ = callback.send(msg);
                }
                Some(Callback::Registered(callback)) => {
                    let callback = callback.clone();
                    spawn(Self::handle_registered_callback(
                        callback,
                        msg,
                        channel.clone(),
                    ));
                }
                None => {
                    warn!("No Callback Registered for {response_uuid}");
                }
            }
        }
    }

    async fn handle_registered_callback(
        callback: RegisteredCallback,
        msg: ResponseMessage,
        channel: ClientChannel,
    ) {
        let (tx, rx) = oneshot::channel();

        let uuid = msg.uuid;

        let response = match callback.send((msg, tx)).await {
            Err(_) => GenericCallbackError::CallbackClosed.into(),
            Ok(()) => rx
                .await
                .unwrap_or_else(|_| GenericCallbackError::CallbackClosed.into()),
        };

        if let Err(e) = Self::send_response(channel, response, uuid).await {
            error!("Failed to send response {e}");
        }
    }

    async fn send_response(
        channel: ClientChannel,
        payload: RequestMessagePayload,
        response_uuid: Uuid,
    ) -> Result<(), MessageError> {
        // If this failed that means we're in the middle of reconnecting, so our callbacks
        // are all being cleaned up as-is. No response needed.
        let sender = channel.try_read()?;
        let data = sender.reserve().await?;

        data.send(OutgoingMessage {
            msg: RequestMessage {
                uuid: Uuid::new_v4(),
                response: Some(response_uuid),
                payload,
            },
            callback: Callback::None,
        });

        Ok(())
    }
}

impl Drop for Client {
    fn drop(&mut self) {
        self.cancel.cancel();
    }
}