// Copyright 2018 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
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// DEALINGS IN THE SOFTWARE.

//! High level manager of the network.
//!
//! A [`Swarm`] contains the state of the network as a whole. The entire behaviour of a
//! libp2p network can be controlled through the `Swarm`.
//!
//! # Initializing a Swarm
//!
//! Creating a `Swarm` requires three things:
//!
//!  1. A network identity of the local node in form of a [`PeerId`].
//!  2. An implementation of the [`Transport`] trait. This is the type that will be used in
//!     order to reach nodes on the network based on their address. See the [`transport`] module
//!     for more information.
//!  3. An implementation of the [`NetworkBehaviour`] trait. This is a state machine that
//!     defines how the swarm should behave once it is connected to a node.
//!
//! # Network Behaviour
//!
//! The `NetworkBehaviour` trait is implemented on types that indicate to the swarm how it should
//! behave. This includes which protocols are supported and which nodes to try to connect to.
//!

use crate::{
    Transport, Multiaddr, PeerId, InboundUpgrade, OutboundUpgrade, UpgradeInfo, ProtocolName,
    muxing::StreamMuxer,
    nodes::{
        handled_node::NodeHandler,
        node::Substream,
        raw_swarm::{self, RawSwarm, RawSwarmEvent}
    },
    protocols_handler::{NodeHandlerWrapperBuilder, NodeHandlerWrapper, NodeHandlerWrapperError, IntoProtocolsHandler, ProtocolsHandler},
    transport::TransportError,
};
use futures::prelude::*;
use smallvec::SmallVec;
use std::{error, fmt, io, ops::{Deref, DerefMut}};

pub mod toggle;

pub use crate::nodes::raw_swarm::ConnectedPoint;

/// Contains the state of the network, plus the way it should behave.
pub struct Swarm<TTransport, TBehaviour>
where TTransport: Transport,
      TBehaviour: NetworkBehaviour,
{
    raw_swarm: RawSwarm<
        TTransport,
        <<<TBehaviour as NetworkBehaviour>::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InEvent,
        <<<TBehaviour as NetworkBehaviour>::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutEvent,
        NodeHandlerWrapperBuilder<TBehaviour::ProtocolsHandler>,
        NodeHandlerWrapperError<<<<TBehaviour as NetworkBehaviour>::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::Error>,
    >,

    /// Handles which nodes to connect to and how to handle the events sent back by the protocol
    /// handlers.
    behaviour: TBehaviour,

    /// List of protocols that the behaviour says it supports.
    supported_protocols: SmallVec<[Vec<u8>; 16]>,

    /// List of multiaddresses we're listening on.
    listened_addrs: SmallVec<[Multiaddr; 8]>,

    /// List of multiaddresses we're listening on, after account for external IP addresses and
    /// similar mechanisms.
    external_addrs: SmallVec<[Multiaddr; 8]>,
}

impl<TTransport, TBehaviour> Deref for Swarm<TTransport, TBehaviour>
where TTransport: Transport,
      TBehaviour: NetworkBehaviour,
{
    type Target = TBehaviour;

    #[inline]
    fn deref(&self) -> &Self::Target {
        &self.behaviour
    }
}

impl<TTransport, TBehaviour> DerefMut for Swarm<TTransport, TBehaviour>
where TTransport: Transport,
      TBehaviour: NetworkBehaviour,
{
    #[inline]
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.behaviour
    }
}

impl<TTransport, TBehaviour, TMuxer> Swarm<TTransport, TBehaviour>
where TBehaviour: NetworkBehaviour,
      TMuxer: StreamMuxer + Send + Sync + 'static,
      <TMuxer as StreamMuxer>::OutboundSubstream: Send + 'static,
      <TMuxer as StreamMuxer>::Substream: Send + 'static,
      TTransport: Transport<Output = (PeerId, TMuxer)> + Clone,
      TTransport::Error: Send + 'static,
      TTransport::Listener: Send + 'static,
      TTransport::ListenerUpgrade: Send + 'static,
      TTransport::Dial: Send + 'static,
      TBehaviour::ProtocolsHandler: Send + 'static,
      <TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler: ProtocolsHandler<Substream = Substream<TMuxer>> + Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InEvent: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutEvent: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::Error: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundOpenInfo: Send + 'static, // TODO: shouldn't be necessary
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol: InboundUpgrade<Substream<TMuxer>> + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::Info: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::InfoIter: Send + 'static,
      <<<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::InfoIter as IntoIterator>::IntoIter: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as InboundUpgrade<Substream<TMuxer>>>::Error: fmt::Debug + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as InboundUpgrade<Substream<TMuxer>>>::Future: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol: OutboundUpgrade<Substream<TMuxer>> + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::Info: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::InfoIter: Send + 'static,
      <<<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::InfoIter as IntoIterator>::IntoIter: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as OutboundUpgrade<Substream<TMuxer>>>::Future: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as OutboundUpgrade<Substream<TMuxer>>>::Error: fmt::Debug + Send + 'static,
      <NodeHandlerWrapper<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler> as NodeHandler>::OutboundOpenInfo: Send + 'static, // TODO: shouldn't be necessary
{
    /// Builds a new `Swarm`.
    #[inline]
    pub fn new(transport: TTransport, behaviour: TBehaviour, local_peer_id: PeerId) -> Self {
        SwarmBuilder::new(transport, behaviour, local_peer_id)
            .build()
    }

    /// Returns the transport passed when building this object.
    #[inline]
    pub fn transport(me: &Self) -> &TTransport {
        me.raw_swarm.transport()
    }

    /// Starts listening on the given address.
    ///
    /// Returns an error if the address is not supported.
    /// On success, returns an alternative version of the address.
    #[inline]
    pub fn listen_on(me: &mut Self, addr: Multiaddr) -> Result<Multiaddr, TransportError<TTransport::Error>> {
        let result = me.raw_swarm.listen_on(addr);
        if let Ok(ref addr) = result {
            me.listened_addrs.push(addr.clone());
        }
        result
    }

    /// Tries to dial the given address.
    ///
    /// Returns an error if the address is not supported.
    #[inline]
    pub fn dial_addr(me: &mut Self, addr: Multiaddr) -> Result<(), TransportError<TTransport::Error>> {
        let handler = me.behaviour.new_handler();
        me.raw_swarm.dial(addr, handler.into_node_handler_builder())
    }

    /// Tries to reach the given peer using the elements in the topology.
    ///
    /// Has no effect if we are already connected to that peer, or if no address is known for the
    /// peer.
    #[inline]
    pub fn dial(me: &mut Self, peer_id: PeerId) {
        let addrs = me.behaviour.addresses_of_peer(&peer_id);
        match me.raw_swarm.peer(peer_id.clone()) {
            raw_swarm::Peer::NotConnected(peer) => {
                let handler = me.behaviour.new_handler().into_node_handler_builder();
                if peer.connect_iter(addrs, handler).is_err() {
                    me.behaviour.inject_dial_failure(&peer_id);
                }
            },
            raw_swarm::Peer::PendingConnect(mut peer) => {
                peer.append_multiaddr_attempts(addrs)
            },
            raw_swarm::Peer::Connected(_) | raw_swarm::Peer::LocalNode => {}
        }
    }

    /// Returns an iterator that produces the list of addresses we're listening on.
    #[inline]
    pub fn listeners(me: &Self) -> impl Iterator<Item = &Multiaddr> {
        RawSwarm::listeners(&me.raw_swarm)
    }

    /// Returns an iterator that produces the list of addresses that other nodes can use to reach
    /// us.
    #[inline]
    pub fn external_addresses(me: &Self) -> impl Iterator<Item = &Multiaddr> {
        me.external_addrs.iter()
    }

    /// Returns the peer ID of the swarm passed as parameter.
    #[inline]
    pub fn local_peer_id(me: &Self) -> &PeerId {
        &me.raw_swarm.local_peer_id()
    }

    /// Adds an external address.
    ///
    /// An external address is an address we are listening on but that accounts for things such as
    /// NAT traversal.
    pub fn add_external_address(me: &mut Self, addr: Multiaddr) {
        if me.external_addrs.iter().all(|a| *a != addr) {
            me.external_addrs.push(addr);
        }
    }
}

impl<TTransport, TBehaviour, TMuxer> Stream for Swarm<TTransport, TBehaviour>
where TBehaviour: NetworkBehaviour,
      TMuxer: StreamMuxer + Send + Sync + 'static,
      <TMuxer as StreamMuxer>::OutboundSubstream: Send + 'static,
      <TMuxer as StreamMuxer>::Substream: Send + 'static,
      TTransport: Transport<Output = (PeerId, TMuxer)> + Clone,
      TTransport::Error: Send + 'static,
      TTransport::Listener: Send + 'static,
      TTransport::ListenerUpgrade: Send + 'static,
      TTransport::Dial: Send + 'static,
      TBehaviour::ProtocolsHandler: Send + 'static,
      <TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler: ProtocolsHandler<Substream = Substream<TMuxer>> + Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InEvent: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutEvent: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::Error: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundOpenInfo: Send + 'static, // TODO: shouldn't be necessary
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol: InboundUpgrade<Substream<TMuxer>> + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as InboundUpgrade<Substream<TMuxer>>>::Future: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as InboundUpgrade<Substream<TMuxer>>>::Error: fmt::Debug + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::Info: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::InfoIter: Send + 'static,
      <<<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::InfoIter as IntoIterator>::IntoIter: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol: OutboundUpgrade<Substream<TMuxer>> + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as OutboundUpgrade<Substream<TMuxer>>>::Future: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as OutboundUpgrade<Substream<TMuxer>>>::Error: fmt::Debug + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::Info: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::InfoIter: Send + 'static,
      <<<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::InfoIter as IntoIterator>::IntoIter: Send + 'static,
      <NodeHandlerWrapper<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler> as NodeHandler>::OutboundOpenInfo: Send + 'static, // TODO: shouldn't be necessary
{
    type Item = TBehaviour::OutEvent;
    type Error = io::Error;

    #[inline]
    fn poll(&mut self) -> Poll<Option<TBehaviour::OutEvent>, io::Error> {
        loop {
            let mut raw_swarm_not_ready = false;

            match self.raw_swarm.poll() {
                Async::NotReady => raw_swarm_not_ready = true,
                Async::Ready(RawSwarmEvent::NodeEvent { peer_id, event }) => {
                    self.behaviour.inject_node_event(peer_id, event);
                },
                Async::Ready(RawSwarmEvent::Connected { peer_id, endpoint }) => {
                    self.behaviour.inject_connected(peer_id, endpoint);
                },
                Async::Ready(RawSwarmEvent::NodeClosed { peer_id, endpoint, .. }) => {
                    self.behaviour.inject_disconnected(&peer_id, endpoint);
                },
                Async::Ready(RawSwarmEvent::Replaced { peer_id, closed_endpoint, endpoint }) => {
                    self.behaviour.inject_replaced(peer_id, closed_endpoint, endpoint);
                },
                Async::Ready(RawSwarmEvent::IncomingConnection(incoming)) => {
                    let handler = self.behaviour.new_handler();
                    incoming.accept(handler.into_node_handler_builder());
                },
                Async::Ready(RawSwarmEvent::ListenerClosed { .. }) => {},
                Async::Ready(RawSwarmEvent::IncomingConnectionError { .. }) => {},
                Async::Ready(RawSwarmEvent::DialError { peer_id, multiaddr, error, new_state }) => {
                    self.behaviour.inject_addr_reach_failure(Some(&peer_id), &multiaddr, &error);
                    if let raw_swarm::PeerState::NotConnected = new_state {
                        self.behaviour.inject_dial_failure(&peer_id);
                    }
                },
                Async::Ready(RawSwarmEvent::UnknownPeerDialError { multiaddr, error, .. }) => {
                    self.behaviour.inject_addr_reach_failure(None, &multiaddr, &error);
                },
            }

            let behaviour_poll = {
                let transport = self.raw_swarm.transport();
                let mut parameters = PollParameters {
                    local_peer_id: &mut self.raw_swarm.local_peer_id(),
                    supported_protocols: &self.supported_protocols,
                    listened_addrs: &self.listened_addrs,
                    external_addrs: &self.external_addrs,
                    nat_traversal: &move |a, b| transport.nat_traversal(a, b),
                };
                self.behaviour.poll(&mut parameters)
            };

            match behaviour_poll {
                Async::NotReady if raw_swarm_not_ready => return Ok(Async::NotReady),
                Async::NotReady => (),
                Async::Ready(NetworkBehaviourAction::GenerateEvent(event)) => {
                    return Ok(Async::Ready(Some(event)));
                },
                Async::Ready(NetworkBehaviourAction::DialAddress { address }) => {
                    let _ = Swarm::dial_addr(self, address);
                },
                Async::Ready(NetworkBehaviourAction::DialPeer { peer_id }) => {
                    Swarm::dial(self, peer_id)
                },
                Async::Ready(NetworkBehaviourAction::SendEvent { peer_id, event }) => {
                    if let Some(mut peer) = self.raw_swarm.peer(peer_id).into_connected() {
                        peer.send_event(event);
                    }
                },
                Async::Ready(NetworkBehaviourAction::ReportObservedAddr { address }) => {
                    for addr in self.raw_swarm.nat_traversal(&address) {
                        if self.external_addrs.iter().all(|a| *a != addr) {
                            self.external_addrs.push(addr);
                        }
                    }
                },
            }
        }
    }
}

/// A behaviour for the network. Allows customizing the swarm.
///
/// This trait has been designed to be composable. Multiple implementations can be combined into
/// one that handles all the behaviours at once.
pub trait NetworkBehaviour {
    /// Handler for all the protocols the network supports.
    type ProtocolsHandler: IntoProtocolsHandler;
    /// Event generated by the swarm.
    type OutEvent;

    /// Builds a new `ProtocolsHandler`.
    fn new_handler(&mut self) -> Self::ProtocolsHandler;

    /// Addresses that this behaviour is aware of for this specific peer, and that may allow
    /// reaching the peer.
    fn addresses_of_peer(&mut self, peer_id: &PeerId) -> Vec<Multiaddr>;

    /// Indicates the behaviour that we connected to the node with the given peer id through the
    /// given endpoint.
    fn inject_connected(&mut self, peer_id: PeerId, endpoint: ConnectedPoint);

    /// Indicates the behaviour that we disconnected from the node with the given peer id. The
    /// endpoint is the one we used to be connected to.
    fn inject_disconnected(&mut self, peer_id: &PeerId, endpoint: ConnectedPoint);

    /// Indicates the behaviour that we replace the connection from the node with another.
    fn inject_replaced(&mut self, peer_id: PeerId, closed_endpoint: ConnectedPoint, new_endpoint: ConnectedPoint) {
        self.inject_disconnected(&peer_id, closed_endpoint);
        self.inject_connected(peer_id, new_endpoint);
    }

    /// Indicates the behaviour that the node with the given peer id has generated an event for
    /// us.
    ///
    /// > **Note**: This method is only called for events generated by the protocols handler.
    fn inject_node_event(
        &mut self,
        peer_id: PeerId,
        event: <<Self::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutEvent
    );

    /// Indicates to the behaviour that we tried to reach an address, but failed.
    ///
    /// If we were trying to reach a specific node, its ID is passed as parameter. If this is the
    /// last address to attempt for the given node, then `inject_dial_failure` is called afterwards.
    fn inject_addr_reach_failure(&mut self, _peer_id: Option<&PeerId>, _addr: &Multiaddr, _error: &dyn error::Error) {
    }

    /// Indicates to the behaviour that we tried to dial all the addresses known for a node, but
    /// failed.
    fn inject_dial_failure(&mut self, _peer_id: &PeerId) {
    }

    /// Polls for things that swarm should do.
    ///
    /// This API mimics the API of the `Stream` trait.
    fn poll(&mut self, params: &mut PollParameters<'_>) -> Async<NetworkBehaviourAction<<<Self::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InEvent, Self::OutEvent>>;
}

/// Used when deriving `NetworkBehaviour`. When deriving `NetworkBehaviour`, must be implemented
/// for all the possible event types generated by the various fields.
// TODO: document how the custom behaviour works and link this here
pub trait NetworkBehaviourEventProcess<TEvent> {
    /// Called when one of the fields of the type you're deriving `NetworkBehaviour` on generates
    /// an event.
    fn inject_event(&mut self, event: TEvent);
}

/// Parameters passed to `poll()`, that the `NetworkBehaviour` has access to.
// TODO: #[derive(Debug)]
pub struct PollParameters<'a: 'a> {
    local_peer_id: &'a PeerId,
    supported_protocols: &'a [Vec<u8>],
    listened_addrs: &'a [Multiaddr],
    external_addrs: &'a [Multiaddr],
    nat_traversal: &'a dyn Fn(&Multiaddr, &Multiaddr) -> Option<Multiaddr>,
}

impl<'a> PollParameters<'a> {
    /// Returns the list of protocol the behaviour supports when a remote negotiates a protocol on
    /// an inbound substream.
    ///
    /// The iterator's elements are the ASCII names as reported on the wire.
    ///
    /// Note that the list is computed once at initialization and never refreshed.
    #[inline]
    pub fn supported_protocols(&self) -> impl ExactSizeIterator<Item = &[u8]> {
        self.supported_protocols.iter().map(AsRef::as_ref)
    }

    /// Returns the list of the addresses we're listening on.
    #[inline]
    pub fn listened_addresses(&self) -> impl ExactSizeIterator<Item = &Multiaddr> {
        self.listened_addrs.iter()
    }

    /// Returns the list of the addresses nodes can use to reach us.
    #[inline]
    pub fn external_addresses(&self) -> impl ExactSizeIterator<Item = &Multiaddr> {
        self.external_addrs.iter()
    }

    /// Returns the peer id of the local node.
    #[inline]
    pub fn local_peer_id(&self) -> &PeerId {
        self.local_peer_id
    }

    /// Calls the `nat_traversal` method on the underlying transport of the `Swarm`.
    #[inline]
    pub fn nat_traversal(&self, server: &Multiaddr, observed: &Multiaddr) -> Option<Multiaddr> {
        (self.nat_traversal)(server, observed)
    }
}

/// Action to perform.
#[derive(Debug, Clone)]
pub enum NetworkBehaviourAction<TInEvent, TOutEvent> {
    /// Generate an event for the outside.
    GenerateEvent(TOutEvent),

    // TODO: report new raw connection for usage after intercepting an address dial

    /// Instructs the swarm to dial the given multiaddress without any expectation of a peer id.
    DialAddress {
        /// The address to dial.
        address: Multiaddr,
    },

    /// Instructs the swarm to try reach the given peer.
    ///
    /// In the future, a corresponding `inject_dial_failure` or `inject_connected` function call
    /// must be performed.
    DialPeer {
        /// The peer to try reach.
        peer_id: PeerId,
    },

    /// If we're connected to the given peer, sends a message to the protocol handler.
    ///
    /// If we're not connected to this peer, does nothing. If necessary, the implementation of
    /// `NetworkBehaviour` is supposed to track which peers we are connected to.
    SendEvent {
        /// The peer which to send the message to.
        peer_id: PeerId,
        /// Event to send to the peer.
        event: TInEvent,
    },

    /// Reports that a remote observes us as this address.
    ///
    /// The swarm will pass this address through the transport's NAT traversal.
    ReportObservedAddr {
        /// The address we're being observed as.
        address: Multiaddr,
    },
}

pub struct SwarmBuilder<TTransport, TBehaviour> {
    incoming_limit: Option<u32>,
    local_peer_id: PeerId,
    transport: TTransport,
    behaviour: TBehaviour,
}

impl<TTransport, TBehaviour, TMuxer> SwarmBuilder<TTransport, TBehaviour>
where TBehaviour: NetworkBehaviour,
      TMuxer: StreamMuxer + Send + Sync + 'static,
      <TMuxer as StreamMuxer>::OutboundSubstream: Send + 'static,
      <TMuxer as StreamMuxer>::Substream: Send + 'static,
      TTransport: Transport<Output = (PeerId, TMuxer)> + Clone,
      TTransport::Error: Send + 'static,
      TTransport::Listener: Send + 'static,
      TTransport::ListenerUpgrade: Send + 'static,
      TTransport::Dial: Send + 'static,
      TBehaviour::ProtocolsHandler: Send + 'static,
      <TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler: ProtocolsHandler<Substream = Substream<TMuxer>> + Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InEvent: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutEvent: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::Error: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundOpenInfo: Send + 'static, // TODO: shouldn't be necessary
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol: InboundUpgrade<Substream<TMuxer>> + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::Info: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::InfoIter: Send + 'static,
      <<<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as UpgradeInfo>::InfoIter as IntoIterator>::IntoIter: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as InboundUpgrade<Substream<TMuxer>>>::Error: fmt::Debug + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::InboundProtocol as InboundUpgrade<Substream<TMuxer>>>::Future: Send + 'static,
      <<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol: OutboundUpgrade<Substream<TMuxer>> + Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::Info: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::InfoIter: Send + 'static,
      <<<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as UpgradeInfo>::InfoIter as IntoIterator>::IntoIter: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as OutboundUpgrade<Substream<TMuxer>>>::Future: Send + 'static,
      <<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler as ProtocolsHandler>::OutboundProtocol as OutboundUpgrade<Substream<TMuxer>>>::Error: fmt::Debug + Send + 'static,
      <NodeHandlerWrapper<<TBehaviour::ProtocolsHandler as IntoProtocolsHandler>::Handler> as NodeHandler>::OutboundOpenInfo: Send + 'static, // TODO: shouldn't be necessary

{
    pub fn new(transport: TTransport, behaviour: TBehaviour, local_peer_id: PeerId) -> Self {
        SwarmBuilder {
            incoming_limit: None,
            local_peer_id,
            transport,
            behaviour,
        }
    }

    pub fn incoming_limit(mut self, incoming_limit: Option<u32>) -> Self {
        self.incoming_limit = incoming_limit;
        self
    }

    pub fn build(mut self) -> Swarm<TTransport, TBehaviour> {
        let supported_protocols = self.behaviour
            .new_handler()
            .into_handler(&self.local_peer_id)
            .listen_protocol()
            .protocol_info()
            .into_iter()
            .map(|info| info.protocol_name().to_vec())
            .collect();

        let raw_swarm = RawSwarm::new_with_incoming_limit(self.transport, self.local_peer_id, self.incoming_limit);

        Swarm {
            raw_swarm,
            behaviour: self.behaviour,
            supported_protocols,
            listened_addrs: SmallVec::new(),
            external_addrs: SmallVec::new(),
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::{identity, PeerId, PublicKey};
    use crate::protocols_handler::{DummyProtocolsHandler, ProtocolsHandler};
    use crate::tests::dummy_transport::DummyTransport;
    use futures::prelude::*;
    use multiaddr::Multiaddr;
    use std::marker::PhantomData;
    use super::{ConnectedPoint, NetworkBehaviour, NetworkBehaviourAction,
                PollParameters, SwarmBuilder};
    use tokio_io::{AsyncRead, AsyncWrite};
    use void::Void;

    #[derive(Clone)]
    struct DummyBehaviour<TSubstream> {
        marker: PhantomData<TSubstream>,
    }

    trait TSubstream: AsyncRead + AsyncWrite {}

    impl<TSubstream> NetworkBehaviour
        for DummyBehaviour<TSubstream>
        where TSubstream: AsyncRead + AsyncWrite
    {
        type ProtocolsHandler = DummyProtocolsHandler<TSubstream>;
        type OutEvent = Void;

        fn new_handler(&mut self) -> Self::ProtocolsHandler {
            DummyProtocolsHandler::default()
        }

        fn addresses_of_peer(&mut self, _: &PeerId) -> Vec<Multiaddr> {
            Vec::new()
        }

        fn inject_connected(&mut self, _: PeerId, _: ConnectedPoint) {}

        fn inject_disconnected(&mut self, _: &PeerId, _: ConnectedPoint) {}

        fn inject_node_event(&mut self, _: PeerId,
            _: <Self::ProtocolsHandler as ProtocolsHandler>::OutEvent) {}

        fn poll(&mut self, _: &mut PollParameters<'_>) ->
            Async<NetworkBehaviourAction<<Self::ProtocolsHandler as
            ProtocolsHandler>::InEvent, Self::OutEvent>>
        {
            Async::NotReady
        }

    }

    fn get_random_id() -> PublicKey {
        identity::Keypair::generate_ed25519().public()
    }

    #[test]
    fn test_build_swarm() {
        let id = get_random_id();
        let transport = DummyTransport::new();
        let behaviour = DummyBehaviour{marker: PhantomData};
        let swarm = SwarmBuilder::new(transport, behaviour, id.into())
            .incoming_limit(Some(4)).build();
        assert_eq!(swarm.raw_swarm.incoming_limit(), Some(4));
    }

    #[test]
    fn test_build_swarm_with_max_listeners_none() {
        let id = get_random_id();
        let transport = DummyTransport::new();
        let behaviour = DummyBehaviour{marker: PhantomData};
        let swarm = SwarmBuilder::new(transport, behaviour, id.into()).build();
        assert!(swarm.raw_swarm.incoming_limit().is_none())

    }


}