nostr-prototype/crates/client/src/relayer.rs

use crate::{pool::Event, Error};
use futures::Future;
use futures_util::{SinkExt, StreamExt};
use nostr_rs_types::{Request, Response};
use std::{
    pin::Pin,
    sync::{
        atomic::{AtomicBool, Ordering::Relaxed},
        Arc,
    },
};
use tokio::{
    sync::mpsc,
    task::JoinHandle,
    time::{sleep, timeout, Duration},
};
use tokio_tungstenite::{connect_async, tungstenite::Message};
use url::Url;

/// Relayer object
#[derive(Debug)]
pub struct Relayer {
    /// URL of the relayer
    pub url: String,
    /// Sender to the relayer. This can be used to send a Requests to this
    /// relayer
    pub send_to_socket: mpsc::Sender<Request>,

    worker: JoinHandle<()>,

    is_connected: Arc<AtomicBool>,
}

const NO_ACTIVITY_TIMEOUT_SECS: u64 = 120;

impl Drop for Relayer {
    fn drop(&mut self) {
        self.worker.abort()
    }
}

impl Relayer {
    /// Creates a new relayer
    pub fn new<F>(
        broadcast_to_listeners: mpsc::Sender<(Event, String)>,
        url: &str,
        on_connection: Option<F>,
    ) -> Result<Self, Error>
    where
        F: (Fn(&str, mpsc::Sender<Request>) -> Pin<Box<dyn Future<Output = ()> + Send>>)
            + Send
            + Sync
            + 'static,
    {
        let (sender_to_socket, send_to_socket) = mpsc::channel(100_000);
        let is_connected = Arc::new(AtomicBool::new(false));
        let worker = Self::spawn_background_client(
            broadcast_to_listeners,
            sender_to_socket.clone(),
            send_to_socket,
            url,
            is_connected.clone(),
            on_connection,
        )?;

        Ok(Self {
            url: url.to_owned(),
            is_connected,
            send_to_socket: sender_to_socket,
            worker,
        })
    }

    fn spawn_background_client<F>(
        broadcast_to_listeners: mpsc::Sender<(Event, String)>,
        sender_to_socket: mpsc::Sender<Request>,
        mut send_to_socket: mpsc::Receiver<Request>,
        url_str: &str,
        is_connected: Arc<AtomicBool>,
        on_connection: Option<F>,
    ) -> Result<JoinHandle<()>, Error>
    where
        F: (Fn(&str, mpsc::Sender<Request>) -> Pin<Box<dyn Future<Output = ()> + Send>>)
            + Send
            + Sync
            + 'static,
    {
        let url = url_str.to_owned();
        let url_parsed = Url::parse(&url)?;

        is_connected.store(false, Relaxed);

        Ok(tokio::spawn(async move {
            let mut connection_attempts = 0;

            loop {
                log::warn!("{}: Connect attempt {}", url, connection_attempts);
                connection_attempts += 1;
                let mut socket = match connect_async(url_parsed.clone()).await {
                    Ok(x) => x.0,
                    Err(err) => {
                        log::warn!("{}: Failed to connect: {}", url, err);
                        sleep(Duration::from_secs(5)).await;
                        continue;
                    }
                };

                log::info!("Connected to {}", url);
                connection_attempts = 0;

                if let Some(on_connection) = &on_connection {
                    on_connection(&url, sender_to_socket.clone()).await;
                }

                loop {
                    tokio::select! {
                        Some(msg) = send_to_socket.recv() => {
                            if let Ok(json) = serde_json::to_string(&msg) {
                                log::info!("{}: Sending {}", url, json);
                                if let Err(x) = socket.send(Message::Text(json)).await {
                                    log::error!("{} : Reconnecting due {}", url, x);
                                    break;
                                }
                            }
                        }
                        msg = timeout(Duration::from_secs(NO_ACTIVITY_TIMEOUT_SECS), socket.next()) => {
                            let msg = if let Ok(Some(Ok(msg))) = msg {
                                is_connected.store(true, Relaxed);
                                    match msg {
                                        Message::Text(text) => text,
                                        Message::Ping(msg) => {
                                            if let Err(x) = socket.send(Message::Pong(msg)).await {
                                                log::error!("{} : Reconnecting due error at sending Pong: {:?}", url, x);
                                                break;
                                            }
                                            continue;
                                        },
                                        msg => {
                                            log::error!("Unexpected {:?}", msg);
                                            continue;
                                        }
                                    }
                                } else {
                                    log::error!("{} Reconnecting client due of empty recv: {:?}", url, msg);
                                    break;
                                };

                            if msg.is_empty() {
                                continue;
                            }

                            log::info!("New message: {}", msg);


                            let msg: Result<Response, _> = serde_json::from_str(&msg);

                            if let Ok(msg) = msg {
                                if let Err(error) = broadcast_to_listeners.try_send((Event::Response(msg.into()), url.to_owned())) {
                                    log::error!("{}: Reconnecting client because of {}", url, error);
                                    break;
                                }
                            }
                        }
                        else => {
                            log::warn!("{}: else", url);
                            break;
                        }
                    }
                }

                is_connected.store(false, Relaxed);
                // Throttle down to not spam the server with reconnections
                sleep(Duration::from_millis(500)).await;
            }
        }))
    }

    /// Checks if the relayer is connected. It is guaranteed that the relayer is
    /// connected if this method returns true.
    pub fn is_connected(&self) -> bool {
        self.is_connected.load(Relaxed)
    }

    /// Sends a requests to this relayer
    pub async fn send(&self, request: Request) -> Result<(), Error> {
        self.send_to_socket
            .send(request)
            .await
            .map_err(|e| Error::Sync(Box::new(e)))
    }
}