// Copyright 2017-2018 Parity Technologies (UK) Ltd.
//
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//! Handles the `/ipfs/ping/1.0.0` protocol. This allows pinging a remote node and waiting for an
//! answer.
//!
//! # Usage
//!
//! The `Ping` struct implements the `NetworkBehaviour` trait. When used, it will automatically
//! send a periodic ping to nodes we are connected to. If a remote doesn't answer in time, it gets
//! automatically disconnected.
//!
//! The `Ping` struct is also what handles answering to the pings sent by remotes.
//!
//! When a ping succeeds, a `PingSuccess` event is generated, indicating the time the ping took.

pub mod protocol;

use futures::prelude::*;
use libp2p_core::swarm::{ConnectedPoint, NetworkBehaviour, NetworkBehaviourAction, PollParameters};
use libp2p_core::protocols_handler::{OneShotHandler, ProtocolsHandler};
use libp2p_core::{Multiaddr, PeerId};
use std::{marker::PhantomData, time::Duration};
use tokio_io::{AsyncRead, AsyncWrite};

/// Network behaviour that handles receiving pings sent by other nodes and periodically pings the
/// nodes we are connected to.
///
/// See the crate root documentation for more information.
pub struct Ping<TSubstream> {
    /// Marker to pin the generics.
    marker: PhantomData<TSubstream>,
    /// Queue of events to report to the user.
    events: Vec<PingEvent>,
}

/// Event generated by the `Ping` behaviour.
pub enum PingEvent {
    /// We have successfully pinged a peer we are connected to.
    PingSuccess {
        /// Id of the peer that we pinged.
        peer: PeerId,
        /// Time elapsed between when we sent the ping and when we received the response.
        time: Duration,
    }
}

impl<TSubstream> Ping<TSubstream> {
    /// Creates a `Ping`.
    pub fn new() -> Self {
        Ping {
            marker: PhantomData,
            events: Vec::new(),
        }
    }
}

impl<TSubstream> Default for Ping<TSubstream> {
    #[inline]
    fn default() -> Self {
        Ping::new()
    }
}

impl<TSubstream> NetworkBehaviour for Ping<TSubstream>
where
    TSubstream: AsyncRead + AsyncWrite,
{
    type ProtocolsHandler = OneShotHandler<TSubstream, protocol::Ping, protocol::Ping, protocol::PingOutput>;
    type OutEvent = PingEvent;

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

    fn addresses_of_peer(&mut self, _peer_id: &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,
        source: PeerId,
        event: <Self::ProtocolsHandler as ProtocolsHandler>::OutEvent,
    ) {
        if let protocol::PingOutput::Ping(time) = event {
            self.events.push(PingEvent::PingSuccess {
                peer: source,
                time,
            })
        }
    }

    fn poll(
        &mut self,
        _: &mut PollParameters<'_>,
    ) -> Async<
        NetworkBehaviourAction<
            <Self::ProtocolsHandler as ProtocolsHandler>::InEvent,
            Self::OutEvent,
        >,
    > {
        if !self.events.is_empty() {
            return Async::Ready(NetworkBehaviourAction::GenerateEvent(self.events.remove(0)));
        }

        Async::NotReady
    }
}