// Copyright 2017 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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use futures::future::Future;
use std::io::Error as IoError;
use tokio_io::{AsyncRead, AsyncWrite};

/// Implemented on objects that can be turned into a substream.
///
/// > **Note**: The methods of this trait consume the object, but if the object implements `Clone`
/// >           then you can clone it and keep the original in order to open additional substreams.
pub trait StreamMuxer {
    /// Type of the object that represents the raw substream where data can be read and written.
    type Substream: AsyncRead + AsyncWrite;

    /// Future that will be resolved when a new incoming substream is open.
    ///
    /// A `None` item signals that the underlying resource has been exhausted and
    /// no more substreams can be created.
    type InboundSubstream: Future<Item = Option<Self::Substream>, Error = IoError>;

    /// Future that will be resolved when the outgoing substream is open.
    ///
    /// A `None` item signals that the underlying resource has been exhausted and
    /// no more substreams can be created.
    type OutboundSubstream: Future<Item = Option<Self::Substream>, Error = IoError>;

    /// Produces a future that will be resolved when a new incoming substream arrives.
    fn inbound(self) -> Self::InboundSubstream;

    /// Opens a new outgoing substream, and produces a future that will be resolved when it becomes
    /// available.
    fn outbound(self) -> Self::OutboundSubstream;
}