protosocket-server 1.0.1

use protosocket::Codec;
use protosocket::Connection;
use protosocket::Decoder;
use protosocket::Encoder;
use protosocket::MessageReactor;
use protosocket::SocketListener;
use protosocket::SocketResult;
use protosocket::TcpSocketListener;
use std::future::Future;
use std::io::Error;
use std::net::SocketAddr;
use std::pin::Pin;
use std::task::Context;
use std::task::Poll;

/// The ServerConnector listens to a socket and spawns a Reactor for each new connection.
pub trait ServerConnector: Unpin {
    /// Message encoding
    type Codec: Codec
        + Decoder<Message = <Self::Reactor as MessageReactor>::Inbound>
        + Encoder<Message = <Self::Reactor as MessageReactor>::Outbound>;
    /// Per-connection message handler
    type Reactor: MessageReactor;
    /// The listener type for this service. E.g., `TcpSocketListener`
    type SocketListener: SocketListener;

    /// Create a new message codec for a connection
    fn codec(&self) -> Self::Codec;

    /// Create a per-connection message Reactor.
    /// You can look at the connection in here if you need some data, like a SocketAddr
    fn new_reactor(
        &self,
        optional_outbound: spillway::Sender<<Self::Reactor as MessageReactor>::LogicalOutbound>,
        _connection: &<Self::SocketListener as SocketListener>::Stream,
    ) -> Self::Reactor;

    /// Spawn a connection - probably you just want tokio::spawn, but you might have other needs.
    fn spawn_connection(
        &self,
        connection: Connection<
            <Self::SocketListener as SocketListener>::Stream,
            Self::Codec,
            Self::Reactor,
        >,
    );
}

/// A `protosocket::Connection` is an IO driver. It directly uses tokio's io wrapper of mio to poll
/// the OS's io primitives, manages read and write buffers, and vends messages to & from connections.
/// Connections send messages to the ConnectionServer through an mpsc channel, and they receive
/// inbound messages via a reactor callback.
///
/// Protosockets are monomorphic messages: You can only have 1 kind of message per service.
/// The expected way to work with this is to use prost and protocol buffers to encode messages.
/// Of course you can do whatever you want, as the telnet example shows.
///
/// Protosocket messages are not opinionated about request & reply. If you are, you will need
/// to implement such a thing. This allows you freely choose whether you want to send
/// fire-&-forget messages sometimes; however it requires you to write your protocol's rules.
/// You get an inbound iterable of <MessageIn> batches and an outbound stream of <MessageOut> per
/// connection - you decide what those mean for you!
///
/// A ProtosocketServer is a future: You spawn it and it runs forever.
///
/// Construct a new ProtosocketServer by creating a ProtosocketServerConfig and calling the {{bind_tcp}} method.
pub struct ProtosocketServer<Connector: ServerConnector> {
    connector: Connector,
    listener: Connector::SocketListener,
    max_buffer_length: usize,
    buffer_allocation_increment: usize,
    max_queued_outbound_messages: usize,
}

/// Socket configuration options for a ProtosocketServer.
pub struct ProtosocketSocketConfig {
    nodelay: bool,
    reuse: bool,
    keepalive_duration: Option<std::time::Duration>,
    listen_backlog: u32,
}

impl ProtosocketSocketConfig {
    /// Whether nodelay should be set on the socket.
    pub fn nodelay(mut self, nodelay: bool) -> Self {
        self.nodelay = nodelay;
        self
    }
    /// Whether reuseaddr and reuseport should be set on the socket.
    pub fn reuse(mut self, reuse: bool) -> Self {
        self.reuse = reuse;
        self
    }
    /// The keepalive window to be set on the socket.
    pub fn keepalive_duration(mut self, keepalive_duration: std::time::Duration) -> Self {
        self.keepalive_duration = Some(keepalive_duration);
        self
    }
    /// The backlog to be set on the socket when invoking `listen`.
    pub fn listen_backlog(mut self, backlog: u32) -> Self {
        self.listen_backlog = backlog;
        self
    }
}

impl Default for ProtosocketSocketConfig {
    fn default() -> Self {
        Self {
            nodelay: true,
            reuse: true,
            keepalive_duration: None,
            listen_backlog: 65536,
        }
    }
}

/// A configurator for a protosocket server
pub struct ProtosocketServerConfig {
    max_buffer_length: usize,
    max_queued_outbound_messages: usize,
    buffer_allocation_increment: usize,
    socket_config: ProtosocketSocketConfig,
}

impl ProtosocketServerConfig {
    /// The maximum buffer length per connection on this server.
    pub fn max_buffer_length(mut self, max_buffer_length: usize) -> Self {
        self.max_buffer_length = max_buffer_length;
        self
    }
    /// The maximum number of queued outbound messages per connection on this server.
    pub fn max_queued_outbound_messages(mut self, max_queued_outbound_messages: usize) -> Self {
        self.max_queued_outbound_messages = max_queued_outbound_messages;
        self
    }
    /// The step size for allocating additional memory for connection buffers on this server.
    pub fn buffer_allocation_increment(mut self, buffer_allocation_increment: usize) -> Self {
        self.buffer_allocation_increment = buffer_allocation_increment;
        self
    }
    /// The tcp socket configuration options for this server.
    pub fn socket_config(mut self, config: ProtosocketSocketConfig) -> Self {
        self.socket_config = config;
        self
    }

    /// Binds a tcp listener to the given address and returns a ProtosocketServer with this configuration.
    /// After binding, you must await the returned server future to process requests.
    pub fn bind_tcp<Connector: ServerConnector<SocketListener = TcpSocketListener>>(
        self,
        address: SocketAddr,
        connector: Connector,
    ) -> crate::Result<ProtosocketServer<Connector>> {
        Ok(ProtosocketServer::new(
            TcpSocketListener::listen(
                address,
                self.socket_config.listen_backlog,
                self.socket_config.keepalive_duration,
            )?,
            connector,
            self,
        ))
    }

    /// Build a socket server with a configured listener and a socket Connector.
    /// After building, you must await the returned server future to process requests.
    pub fn build_server<
        Connector: ServerConnector<SocketListener = Listener>,
        Listener: SocketListener,
    >(
        self,
        listener: Listener,
        connector: Connector,
    ) -> crate::Result<ProtosocketServer<Connector>> {
        Ok(ProtosocketServer::new(listener, connector, self))
    }
}

impl Default for ProtosocketServerConfig {
    fn default() -> Self {
        Self {
            max_buffer_length: 16 * (2 << 20),
            max_queued_outbound_messages: 128,
            buffer_allocation_increment: 1 << 20,
            socket_config: Default::default(),
        }
    }
}

impl<Connector: ServerConnector> ProtosocketServer<Connector> {
    /// Construct a new `ProtosocketServer`.
    fn new(
        listener: Connector::SocketListener,
        connector: Connector,
        config: ProtosocketServerConfig,
    ) -> Self {
        Self {
            connector,
            listener,
            max_buffer_length: config.max_buffer_length,
            max_queued_outbound_messages: config.max_queued_outbound_messages,
            buffer_allocation_increment: config.buffer_allocation_increment,
        }
    }
}

impl<Connector: ServerConnector> Unpin for ProtosocketServer<Connector> {}
impl<Connector: ServerConnector> Future for ProtosocketServer<Connector> {
    type Output = Result<(), Error>;

    fn poll(mut self: Pin<&mut Self>, context: &mut Context<'_>) -> Poll<Self::Output> {
        loop {
            break match self.listener.poll_accept(context) {
                Poll::Ready(result) => match result {
                    SocketResult::Stream(stream) => {
                        let (outbound_submission_queue, outbound_messages) = spillway::channel();
                        // I want to let people make their stream,reactor tuple in an async context.
                        // I want it to not require Send, so that io_uring is possible
                        // That unfortunately means that Stream might have to be internally async
                        let reactor = self
                            .connector
                            .new_reactor(outbound_submission_queue.clone(), &stream);
                        let connection = Connection::new(
                            stream,
                            self.connector.codec(),
                            self.max_buffer_length,
                            self.buffer_allocation_increment,
                            self.max_queued_outbound_messages,
                            outbound_messages,
                            reactor,
                        );
                        self.connector.spawn_connection(connection);
                        continue;
                    }
                    SocketResult::Disconnect => Poll::Ready(Ok(())),
                },
                Poll::Pending => Poll::Pending,
            };
        }
    }
}