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use crate::framing::packet::CloudProtoPacket;
use crate::framing::CloudProtoError;
use bytes::Bytes;
use futures_util::{Sink, SinkExt, Stream, StreamExt};
use std::pin::Pin;
use std::task::{ready, Context, Poll};
use tokio::io::{AsyncRead, AsyncWrite, ReadHalf, WriteHalf};
use tokio_util::codec::{BytesCodec, FramedRead, FramedWrite, LengthDelimitedCodec};
use tracing::{error, trace};

/// Default maximum size of a single [`CloudProtoPacket`](super::CloudProtoPacket), including header
pub const DEFAULT_MAX_FRAME_LENGTH: usize = 32 * 1024 * 1024;

/// The common socket that carries framing-layer [`packets`](super::CloudProtoPacket) used by higher level protocols
pub struct CloudProtoSocket<IO: AsyncRead + AsyncWrite> {
    read: FramedRead<ReadHalf<IO>, LengthDelimitedCodec>,
    write: FramedWrite<WriteHalf<IO>, BytesCodec>,
}

impl<IO> CloudProtoSocket<IO>
where
    IO: AsyncRead + AsyncWrite,
{
    /// CloudProtoSocket is usually layered over a TLS session over TCP port 443,
    /// so in practice `IO` should usually be `TlsStream<TcpStream>`.
    ///
    /// The socket buffers individual packets, and has a default maximum packet size of
    /// [`DEFAULT_MAX_FRAME_LENGTH`](DEFAULT_MAX_FRAME_LENGTH).
    /// See [`with_max_frame_length`](Self::with_max_frame_length) to adjust this limit.
    pub fn new(io: IO) -> Self {
        Self::with_max_frame_length(io, DEFAULT_MAX_FRAME_LENGTH)
    }

    /// CloudProtoSocket is usually layered over a TLS session over TCP port 443,
    /// so in practice `IO` should usually be `TlsStream<TcpStream>`.
    ///
    /// The socket buffers individual packets, `max_frame_length` will be the maximum accepted size
    /// of [`CloudProtoPacket`](super::CloudProtoPacket)s, including header.
    pub fn with_max_frame_length(io: IO, max_frame_length: usize) -> Self {
        let (read, write) = tokio::io::split(io);
        let read = LengthDelimitedCodec::builder()
            .big_endian()
            .max_frame_length(max_frame_length)
            .length_field_type::<u32>()
            .length_adjustment(0)
            .length_field_offset(4)
            .num_skip(0)
            .new_read(read);
        let write = FramedWrite::new(write, BytesCodec::new());
        Self { read, write }
    }
}

impl<IO> Stream for CloudProtoSocket<IO>
where
    IO: AsyncRead + AsyncWrite,
{
    type Item = Result<CloudProtoPacket, CloudProtoError>;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let this = self.get_mut();
        let pkt = match ready!(this.read.poll_next_unpin(cx)) {
            Some(Ok(frame)) => CloudProtoPacket::from_buf(&frame),
            Some(Err(e)) => {
                return Poll::Ready(Some(Err(CloudProtoError::Io { source: e })));
            }
            None => return Poll::Ready(None),
        };
        match pkt {
            Ok(pkt) => {
                trace!(
                    "Received kind 0x{:x} packet with 0x{:x} bytes payload: {}",
                    pkt.kind,
                    pkt.payload.len(),
                    hex::encode(&pkt.payload),
                );
                Poll::Ready(Some(Ok(pkt)))
            }
            Err(e) => {
                error!("Received bad cloudproto packet: {}", e);
                Poll::Ready(Some(Err(e)))
            }
        }
    }
}

impl<IO> Sink<CloudProtoPacket> for CloudProtoSocket<IO>
where
    IO: AsyncRead + AsyncWrite,
{
    type Error = std::io::Error;

    fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        SinkExt::<Bytes>::poll_ready_unpin(&mut self.get_mut().write, cx)
    }

    fn start_send(self: Pin<&mut Self>, pkt: CloudProtoPacket) -> Result<(), Self::Error> {
        let this = self.get_mut();
        let buf = Bytes::from(pkt.to_buf());
        trace!(
            "Sending kind 0x{:x} packet with 0x{:x} bytes payload: {}",
            pkt.kind,
            pkt.payload.len(),
            hex::encode(&pkt.payload),
        );
        this.write.start_send_unpin(buf)
    }

    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        SinkExt::<Bytes>::poll_flush_unpin(&mut self.get_mut().write, cx)
    }

    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        SinkExt::<Bytes>::poll_close_unpin(&mut self.get_mut().write, cx)
    }
}

#[cfg(test)]
mod test {
    use crate::framing::{CloudProtoPacket, CloudProtoSocket, CloudProtoVersion};
    use crate::services::CloudProtoMagic;
    use anyhow::Result;
    use futures_util::{SinkExt, StreamExt};
    use rand::Rng;

    #[test_log::test(tokio::test)]
    async fn single_send_recv() -> Result<()> {
        let (client, server) = tokio::io::duplex(100 * 1024);
        let mut client = CloudProtoSocket::new(client);
        let mut server = CloudProtoSocket::new(server);

        let mut rng = rand::thread_rng();
        let len = rng.gen::<u16>() as usize;
        let mut payload = Vec::with_capacity(len);
        payload.resize(len, len as u8);
        let pkt = CloudProtoPacket {
            magic: CloudProtoMagic::TS,
            kind: 0,
            version: CloudProtoVersion::Normal,
            payload,
        };
        client.send(pkt.clone()).await?;
        let reply = server.next().await.unwrap()?;
        assert_eq!(pkt, reply);

        Ok(())
    }
}