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//! Muxing is the process of splitting a connection into multiple substreams.
//!
//! The main item of this module is the `StreamMuxer` trait. An implementation of `StreamMuxer`
//! has ownership of a connection, lets you open and close substreams, and read/write data
//! on open substreams.
//!
//! > **Note**: You normally don't need to use the methods of the `StreamMuxer` directly, as this
//! >           is managed by the library's internals.
//!
//! Each substream of a connection is an isolated stream of data. All the substreams are muxed
//! together so that the data read from or written to each substream doesn't influence the other
//! substreams.
//!
//! In the context of libp2p, each substream can use a different protocol. Contrary to opening a
//! connection, opening a substream is almost free in terms of resources. This means that you
//! shouldn't hesitate to rapidly open and close substreams, and to design protocols that don't
//! require maintaining long-lived channels of communication.
//!
//! > **Example**: The Kademlia protocol opens a new substream for each request it wants to
//! >              perform. Multiple requests can be performed simultaneously by opening multiple
//! >              substreams, without having to worry about associating responses with the
//! >              right request.
//!
//! # Implementing a muxing protocol
//!
//! In order to implement a muxing protocol, create an object that implements the `UpgradeInfo`
//! and `Upgrader` traits. See the `upgrade` module for more information.
//! The `Output` associated type of the `Upgrader` traits should be an object that implements
//! the `StreamMuxer` trait.
//!
//! The upgrade process will take ownership of the connection, which makes it possible for the
//! implementation of `StreamMuxer` to control everything that happens on the wire.
//!
//! The `Output` associated type of the `StreamMuxer` is a trait object `IReadWrite`, which is
//! in fact AsyncRead + AsyncWrite + StreamInfo + Unpin.
//!
//! IStreamMuxer is the trait object of StreamMuxer.

use async_trait::async_trait;
use futures::future::BoxFuture;

use crate::secure_io::SecureInfo;
use crate::transport::{ConnectionInfo, TransportError};
use futures::{AsyncRead, AsyncWrite};

/// StreamInfo returns the information of a substream opened by stream muxer.
///
/// The output of StreamMuxer must implements this trait.
pub trait StreamInfo: Send {
    /// Returns the identity of the stream.
    fn id(&self) -> usize;
}

/// The trait for IReadWrite. It can be made into a trait object `IReadWrite` used
/// by Swarm Substream.
/// `StreamInfo` must be supported.
#[async_trait]
pub trait ReadWriteEx: AsyncRead + AsyncWrite + StreamInfo + Unpin + std::fmt::Debug {
    fn box_clone(&self) -> IReadWrite;
}

pub type IReadWrite = Box<dyn ReadWriteEx>;

/*
impl Clone for IReadWrite {
    fn clone(&self) -> Self {
        self.box_clone()
    }
}
 */

/*
impl AsyncRead for IReadWrite {
    fn poll_read(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8]) -> Poll<io::Result<usize>> {
        AsyncRead::poll_read(Pin::new(&mut **self), cx, buf)
    }
}

impl AsyncWrite for IReadWrite {
    fn poll_write(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8]) -> Poll<io::Result<usize>> {
        AsyncWrite::poll_write(Pin::new(&mut **self), cx, buf)
    }

    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        AsyncWrite::poll_flush(Pin::new(&mut **self), cx)
    }

    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        AsyncWrite::poll_close(Pin::new(&mut **self), cx)
    }
}
 */

#[async_trait]
pub trait StreamMuxer {
    /// Opens a new outgoing substream.
    async fn open_stream(&mut self) -> Result<IReadWrite, TransportError>;
    /// Accepts a new incoming substream.
    async fn accept_stream(&mut self) -> Result<IReadWrite, TransportError>;
    /// Closes the stream muxer, the runtime of stream muxer will then exit.
    async fn close(&mut self) -> Result<(), TransportError>;
    /// Returns a Future which represents the main loop of the stream muxer.
    fn task(&mut self) -> Option<BoxFuture<'static, ()>>;
    /// Returns the cloned Trait object.
    fn box_clone(&self) -> IStreamMuxer;
}

/// The trait for IStreamMuxer. It can be made into a trait object `IStreamMuxer`.
/// Stream muxer in Swarm must support ConnectionInfo + SecureInfo.
pub trait StreamMuxerEx: StreamMuxer + ConnectionInfo + SecureInfo + std::fmt::Debug {}

pub type IStreamMuxer = Box<dyn StreamMuxerEx>;

impl Clone for IStreamMuxer {
    fn clone(&self) -> Self {
        self.box_clone()
    }
}