rumqttc-v4-next 0.33.1

use futures_util::{FutureExt, SinkExt, StreamExt};
pub use rumqttc_core::AsyncReadWrite;
use tokio_util::codec::Framed;

use crate::mqttbytes::{
    self,
    v4::{Codec, Packet},
};
use crate::{Incoming, MqttState, StateError};

/// Network transforms packets <-> frames efficiently. It takes
/// advantage of pre-allocation, buffering and vectorization when
/// appropriate to achieve performance
pub struct Network {
    /// Frame MQTT packets from network connection
    framed: Framed<Box<dyn AsyncReadWrite>, Codec>,
}

impl Network {
    pub fn new(
        socket: impl AsyncReadWrite + 'static,
        max_incoming_size: usize,
        max_outgoing_size: usize,
    ) -> Self {
        let socket = Box::new(socket) as Box<dyn AsyncReadWrite>;
        let codec = Codec {
            max_incoming_size,
            max_outgoing_size,
        };
        let framed = Framed::new(socket, codec);

        Self { framed }
    }

    /// Reads and returns a single packet from network
    pub async fn read(&mut self) -> Result<Incoming, StateError> {
        match self.framed.next().await {
            Some(Ok(packet)) => Ok(packet),
            Some(Err(mqttbytes::Error::InsufficientBytes(_))) => unreachable!(),
            Some(Err(e)) => Err(StateError::Deserialization(e)),
            None => Err(StateError::ConnectionAborted),
        }
    }

    /// Read packets in bulk. This allow replies to be in bulk. This method is used
    /// after the connection is established to read a bunch of incoming packets
    pub async fn readb(
        &mut self,
        state: &mut MqttState,
        read_batch_limit: usize,
    ) -> Result<(), StateError> {
        // wait for the first read
        let mut res = self.framed.next().await;
        let read_batch_limit = read_batch_limit.max(1);
        let mut count = 0;
        loop {
            match res {
                Some(Ok(packet)) => {
                    if let Some(outgoing) = state.handle_incoming_packet(packet)? {
                        self.write(outgoing).await?;
                    }

                    count += 1;
                    if count >= read_batch_limit {
                        break;
                    }
                }
                Some(Err(mqttbytes::Error::InsufficientBytes(_))) => unreachable!(),
                Some(Err(e)) => return Err(StateError::Deserialization(e)),
                None => return Err(StateError::ConnectionAborted),
            }
            // do not wait for subsequent reads
            match self.framed.next().now_or_never() {
                Some(r) => res = r,
                _ => break,
            }
        }

        Ok(())
    }

    /// Serializes packet into write buffer
    pub async fn write(&mut self, packet: Packet) -> Result<(), StateError> {
        self.framed
            .feed(packet)
            .await
            .map_err(StateError::Deserialization)
    }

    pub async fn flush(&mut self) -> Result<(), crate::state::StateError> {
        self.framed
            .flush()
            .await
            .map_err(StateError::Deserialization)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use tokio::io::{AsyncWriteExt, duplex};

    #[tokio::test]
    async fn readb_processes_exactly_two_packets_when_limit_is_two() {
        let (client, mut peer) = duplex(64);
        let mut network = Network::new(client, 1024, 1024);
        let mut state = MqttState::builder(10).build();

        peer.write_all(&[0xD0, 0x00, 0xD0, 0x00]).await.unwrap();

        network.readb(&mut state, 2).await.unwrap();

        assert_eq!(state.events.len(), 2);
    }

    #[tokio::test]
    async fn readb_processes_one_packet_when_limit_is_one() {
        let (client, mut peer) = duplex(64);
        let mut network = Network::new(client, 1024, 1024);
        let mut state = MqttState::builder(10).build();

        peer.write_all(&[0xD0, 0x00, 0xD0, 0x00]).await.unwrap();

        network.readb(&mut state, 1).await.unwrap();

        assert_eq!(state.events.len(), 1);
    }
}