// Copyright 2017-2018 Parity Technologies (UK) Ltd.
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//! This module implements the `/ipfs/ping/1.0.0` protocol.
//!
//! The ping protocol can be used as a simple application-layer health check
//! for connections of any [`Transport`] as well as to measure and record
//! round-trip times.
//!
//! # Usage
//!
//! The [`Behaviour`] struct implements the [`NetworkBehaviour`] trait. When used with a [`Swarm`],
//! it will respond to inbound ping requests and as necessary periodically send outbound
//! ping requests on every established connection. If a configurable number of consecutive
//! pings fail, the connection will be closed.
//!
//! The [`Behaviour`] network behaviour produces [`Event`]s, which may be consumed from the [`Swarm`]
//! by an application, e.g. to collect statistics.
//!
//! > **Note**: The ping protocol does not keep otherwise idle connections alive
//! > by default, see [`Config::with_keep_alive`] for changing this behaviour.
//!
//! [`Swarm`]: libp2p_swarm::Swarm
//! [`Transport`]: libp2p_core::Transport

#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]

mod handler;
mod protocol;

use handler::Handler;
pub use handler::{Config, Failure, Success};
use libp2p_core::{Endpoint, Multiaddr, PeerId};
use libp2p_swarm::{
    behaviour::FromSwarm, ConnectionDenied, ConnectionId, NetworkBehaviour, NetworkBehaviourAction,
    PollParameters, THandler, THandlerInEvent, THandlerOutEvent,
};
use std::{
    collections::VecDeque,
    task::{Context, Poll},
};

#[deprecated(since = "0.39.1", note = "Use libp2p::ping::Config instead.")]
pub type PingConfig = Config;

#[deprecated(since = "0.39.1", note = "Use libp2p::ping::Event instead.")]
pub type PingEvent = Event;

#[deprecated(since = "0.39.1", note = "Use libp2p::ping::Success instead.")]
pub type PingSuccess = Success;

#[deprecated(since = "0.39.1", note = "Use libp2p::ping::Failure instead.")]
pub type PingFailure = Failure;

#[deprecated(since = "0.39.1", note = "Use libp2p::ping::Result instead.")]
pub type PingResult = Result;

#[deprecated(since = "0.39.1", note = "Use libp2p::ping::Behaviour instead.")]
pub type Ping = Behaviour;

pub use self::protocol::PROTOCOL_NAME;

/// The result of an inbound or outbound ping.
pub type Result = std::result::Result<Success, Failure>;

/// A [`NetworkBehaviour`] that responds to inbound pings and
/// periodically sends outbound pings on every established connection.
///
/// See the crate root documentation for more information.
pub struct Behaviour {
    /// Configuration for outbound pings.
    config: Config,
    /// Queue of events to yield to the swarm.
    events: VecDeque<Event>,
}

/// Event generated by the `Ping` network behaviour.
#[derive(Debug)]
pub struct Event {
    /// The peer ID of the remote.
    pub peer: PeerId,
    /// The result of an inbound or outbound ping.
    pub result: Result,
}

impl Behaviour {
    /// Creates a new `Ping` network behaviour with the given configuration.
    pub fn new(config: Config) -> Self {
        Self {
            config,
            events: VecDeque::new(),
        }
    }
}

impl Default for Behaviour {
    fn default() -> Self {
        Self::new(Config::new())
    }
}

impl NetworkBehaviour for Behaviour {
    type ConnectionHandler = Handler;
    type OutEvent = Event;

    fn handle_established_inbound_connection(
        &mut self,
        _: ConnectionId,
        _: PeerId,
        _: &Multiaddr,
        _: &Multiaddr,
    ) -> std::result::Result<THandler<Self>, ConnectionDenied> {
        Ok(Handler::new(self.config.clone()))
    }

    fn handle_established_outbound_connection(
        &mut self,
        _: ConnectionId,
        _: PeerId,
        _: &Multiaddr,
        _: Endpoint,
    ) -> std::result::Result<THandler<Self>, ConnectionDenied> {
        Ok(Handler::new(self.config.clone()))
    }

    fn on_connection_handler_event(
        &mut self,
        peer: PeerId,
        _: ConnectionId,
        result: THandlerOutEvent<Self>,
    ) {
        self.events.push_front(Event { peer, result })
    }

    fn poll(
        &mut self,
        _: &mut Context<'_>,
        _: &mut impl PollParameters,
    ) -> Poll<NetworkBehaviourAction<Self::OutEvent, THandlerInEvent<Self>>> {
        if let Some(e) = self.events.pop_back() {
            let Event { result, peer } = &e;

            match result {
                Ok(Success::Ping { .. }) => log::debug!("Ping sent to {:?}", peer),
                Ok(Success::Pong) => log::debug!("Ping received from {:?}", peer),
                _ => {}
            }

            Poll::Ready(NetworkBehaviourAction::GenerateEvent(e))
        } else {
            Poll::Pending
        }
    }

    fn on_swarm_event(
        &mut self,
        event: libp2p_swarm::behaviour::FromSwarm<Self::ConnectionHandler>,
    ) {
        match event {
            FromSwarm::ConnectionEstablished(_)
            | FromSwarm::ConnectionClosed(_)
            | FromSwarm::AddressChange(_)
            | FromSwarm::DialFailure(_)
            | FromSwarm::ListenFailure(_)
            | FromSwarm::NewListener(_)
            | FromSwarm::NewListenAddr(_)
            | FromSwarm::ExpiredListenAddr(_)
            | FromSwarm::ListenerError(_)
            | FromSwarm::ListenerClosed(_)
            | FromSwarm::NewExternalAddr(_)
            | FromSwarm::ExpiredExternalAddr(_) => {}
        }
    }
}