use std::sync::atomic::{AtomicU64, Ordering};

use futures::{SinkExt, StreamExt, future::{select, Either}};
use gloo_net::websocket::{futures::WebSocket, Message};
use nrpc::{ClientHandler, ServiceError, ServiceClientStream, /*_helpers::async_trait,*/ _helpers::bytes};
use wasm_bindgen_futures::spawn_local;

static LAST_ID: AtomicU64 = AtomicU64::new(0);

/// Websocket client.
/// In most cases, this shouldn't be used directly, but generated code will use this.
pub struct WebSocketHandler {
    port: u16,
}

#[inline]
fn ws_is_alive(ws_state: &gloo_net::websocket::State) -> bool {
    match ws_state {
        gloo_net::websocket::State::Connecting | gloo_net::websocket::State::Open => true,
        gloo_net::websocket::State::Closing | gloo_net::websocket::State::Closed => false,
    }
}

async fn send_recv_ws<'a>(mut tx: futures_channel::mpsc::Sender<Result<bytes::Bytes, String>>, url: String, mut input: ServiceClientStream<'a, bytes::Bytes>) {
    let ws = match WebSocket::open_with_protocol(&url, "usdpl-nrpc").map_err(|e| e.to_string()) {
        Ok(x) => x,
        Err(e) => {
            log::error!("ws open error: {}", e);
            tx.send(Err(e.to_string())).await.unwrap_or(());
            return;
        }
    };


    log::debug!("ws opened successfully with url `{}`", url);

    let (mut input_done, mut output_done) = (false, false);
    let mut last_ws_state = ws.state();
    log::debug!("ws with url `{}` initial state: {:?}", url, last_ws_state);
    let (mut ws_sink, mut ws_stream) = ws.split();
    let (mut left, mut right) = (input.next(), ws_stream.next());
    while ws_is_alive(&last_ws_state) {
        if !input_done && !output_done {
            log::debug!("Input and output streams are both alive");
            match select(left, right).await {
                Either::Left((next, outstanding)) => {
                   log::debug!("Got message to send over websocket");
                    if let Some(next) = next {
                        match next {
                            Ok(next) => {
                                if let Err(e) = ws_sink.send(Message::Bytes(next.into())).await {
                                    tx.send(Err(e.to_string())).await.unwrap_or(());
                                }
                            },
                            Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(())
                        }
                    } else {
                        input_done = true;
                    }
                    right = outstanding;
                    left = input.next();
                },
                Either::Right((response, outstanding)) => {
                    log::debug!("Received message from websocket");
                    if let Some(next) = response {
                        match next {
                            Ok(Message::Bytes(b)) => tx.send(Ok(b.into())).await.unwrap_or(()),
                            Ok(_) => tx.send(Err("Message::Text not allowed".into())).await.unwrap_or(()),
                            Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(()),
                        }
                    } else {
                        output_done = true;
                    }
                    left = outstanding;
                    let ws = ws_stream.reunite(ws_sink).unwrap();
                    last_ws_state = ws.state();
                    (ws_sink, ws_stream) = ws.split();
                    right = ws_stream.next();
                }
            }
        } else if input_done {
            log::debug!("Input stream is complete");
            if let Some(next) = right.await {
                log::debug!("Received message from websocket");
                match next {
                    Ok(Message::Bytes(b)) => tx.send(Ok(b.into())).await.unwrap_or(()),
                    Ok(_) => tx.send(Err("Message::Text not allowed".into())).await.unwrap_or(()),
                    Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(()),
                }
            } else {
                output_done = true;
            }
            //left = outstanding;
            let ws = ws_stream.reunite(ws_sink).unwrap();
            last_ws_state = ws.state();
            (ws_sink, ws_stream) = ws.split();
            right = ws_stream.next();
        } else {
            // output_done is true
            log::debug!("Output stream is complete");
            if let Some(next) = left.await {
                log::debug!("Got message to send over websocket");
                match next {
                    Ok(next) => {
                        if let Err(e) = ws_sink.send(Message::Bytes(next.into())).await {
                            tx.send(Err(e.to_string())).await.unwrap_or(());
                        }
                    },
                    Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(())
                }
            } else {
                input_done = true;
            }
            //right = outstanding;
            let ws = ws_stream.reunite(ws_sink).unwrap();
            last_ws_state = ws.state();
            (ws_sink, ws_stream) = ws.split();
            left = input.next();
            right = ws_stream.next(); // this should always resolve to None (but compiler is unhappy without this)
        }
    }

    log::debug!("ws with url `{}` has closed", url);
}

#[derive(Debug)]
struct ErrorStr(String);

impl std::fmt::Display for ErrorStr {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Error message: {}", self.0)
    }
}

impl std::error::Error for ErrorStr {}

const CHANNEL_BOUND: usize = 4;

impl WebSocketHandler {
    /// Instantiate the web socket client for connecting on the specified port
    pub fn new(port: u16) -> Self {
        Self { port }
    }
}

//#[async_trait::async_trait(?Send)]
impl ClientHandler<'static> for WebSocketHandler {
    #[allow(async_fn_in_trait)]
    async fn call<'a: 'static>(
        &self,
        package: &str,
        service: &str,
        method: &str,
        input: ServiceClientStream<'a, bytes::Bytes>,
    ) -> Result<ServiceClientStream<'a, bytes::Bytes>, ServiceError> {
        let id = LAST_ID.fetch_add(1, Ordering::SeqCst);
        let url = format!(
            "ws://usdpl-ws-{}.localhost:{}/{}.{}/{}",
            id, self.port, package, service, method,
        );
        log::debug!("doing send/receive on ws url `{}`", url);
        let (tx, rx) = futures_channel::mpsc::channel(CHANNEL_BOUND);
        spawn_local(send_recv_ws(tx, url, input));

        Ok(Box::new(rx.map(|buf_result: Result<bytes::Bytes, String>| buf_result
            .map(|buf| bytes::Bytes::from(buf))
            .map_err(|e| ServiceError::Method(Box::new(ErrorStr(e)))))))
    }
}