Refactor the Identify protocol. (#1231)

* Refactor the Identify protocol.

Thereby updating the documentation. The low-level protocol
and handler modules are no longer exposed and some constructors
of the IdentifyEvent renamed.

* Update protocols/identify/src/protocol.rs

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

protocols/identify/src/handler.rs

@@ -0,0 +1,171 @@
+// 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
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+use crate::protocol::{RemoteInfo, IdentifyProtocolConfig, ReplySubstream};
+use futures::prelude::*;
+use libp2p_core::upgrade::{
+    InboundUpgrade,
+    OutboundUpgrade,
+    Negotiated
+};
+use libp2p_swarm::{
+    KeepAlive,
+    SubstreamProtocol,
+    ProtocolsHandler,
+    ProtocolsHandlerEvent,
+    ProtocolsHandlerUpgrErr
+};
+use smallvec::SmallVec;
+use std::{io, marker::PhantomData, time::Duration};
+use tokio_io::{AsyncRead, AsyncWrite};
+use wasm_timer::{Delay, Instant};
+use void::Void;
+
+/// Delay between the moment we connect and the first time we identify.
+const DELAY_TO_FIRST_ID: Duration = Duration::from_millis(500);
+/// After an identification succeeded, wait this long before the next time.
+const DELAY_TO_NEXT_ID: Duration = Duration::from_secs(5 * 60);
+/// After we failed to identify the remote, try again after the given delay.
+const TRY_AGAIN_ON_ERR: Duration = Duration::from_secs(60 * 60);
+
+/// Protocol handler for sending and receiving identification requests.
+///
+/// Outbound requests are sent periodically. The handler performs expects
+/// at least one identification request to be answered by the remote before
+/// permitting the underlying connection to be closed.
+pub struct IdentifyHandler<TSubstream> {
+    /// Configuration for the protocol.
+    config: IdentifyProtocolConfig,
+
+    /// Pending events to yield.
+    events: SmallVec<[IdentifyHandlerEvent<TSubstream>; 4]>,
+
+    /// Future that fires when we need to identify the node again.
+    next_id: Delay,
+
+    /// Whether the handler should keep the connection alive.
+    keep_alive: KeepAlive,
+
+    /// Marker for strong typing.
+    marker: PhantomData<TSubstream>,
+}
+
+/// Event produced by the `IdentifyHandler`.
+#[derive(Debug)]
+pub enum IdentifyHandlerEvent<TSubstream> {
+    /// We obtained identification information from the remote
+    Identified(RemoteInfo),
+    /// We received a request for identification.
+    Identify(ReplySubstream<Negotiated<TSubstream>>),
+    /// Failed to identify the remote.
+    IdentificationError(ProtocolsHandlerUpgrErr<io::Error>),
+}
+
+impl<TSubstream> IdentifyHandler<TSubstream> {
+    /// Creates a new `IdentifyHandler`.
+    pub fn new() -> Self {
+        IdentifyHandler {
+            config: IdentifyProtocolConfig,
+            events: SmallVec::new(),
+            next_id: Delay::new(Instant::now() + DELAY_TO_FIRST_ID),
+            keep_alive: KeepAlive::Yes,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<TSubstream> ProtocolsHandler for IdentifyHandler<TSubstream>
+where
+    TSubstream: AsyncRead + AsyncWrite,
+{
+    type InEvent = Void;
+    type OutEvent = IdentifyHandlerEvent<TSubstream>;
+    type Error = wasm_timer::Error;
+    type Substream = TSubstream;
+    type InboundProtocol = IdentifyProtocolConfig;
+    type OutboundProtocol = IdentifyProtocolConfig;
+    type OutboundOpenInfo = ();
+
+    fn listen_protocol(&self) -> SubstreamProtocol<Self::InboundProtocol> {
+        SubstreamProtocol::new(self.config.clone())
+    }
+
+    fn inject_fully_negotiated_inbound(
+        &mut self,
+        protocol: <Self::InboundProtocol as InboundUpgrade<TSubstream>>::Output
+    ) {
+        self.events.push(IdentifyHandlerEvent::Identify(protocol))
+    }
+
+    fn inject_fully_negotiated_outbound(
+        &mut self,
+        protocol: <Self::OutboundProtocol as OutboundUpgrade<TSubstream>>::Output,
+        _info: Self::OutboundOpenInfo,
+    ) {
+        self.events.push(IdentifyHandlerEvent::Identified(protocol));
+        self.keep_alive = KeepAlive::No;
+    }
+
+    fn inject_event(&mut self, _: Self::InEvent) {}
+
+    fn inject_dial_upgrade_error(
+        &mut self,
+        _info: Self::OutboundOpenInfo,
+        err: ProtocolsHandlerUpgrErr<
+            <Self::OutboundProtocol as OutboundUpgrade<Self::Substream>>::Error
+        >
+    ) {
+        self.events.push(IdentifyHandlerEvent::IdentificationError(err));
+        self.keep_alive = KeepAlive::No;
+        self.next_id.reset(Instant::now() + TRY_AGAIN_ON_ERR);
+    }
+
+    fn connection_keep_alive(&self) -> KeepAlive {
+        self.keep_alive
+    }
+
+    fn poll(&mut self) -> Poll<
+        ProtocolsHandlerEvent<
+            Self::OutboundProtocol,
+            Self::OutboundOpenInfo,
+            IdentifyHandlerEvent<TSubstream>,
+        >,
+        Self::Error,
+    > {
+        if !self.events.is_empty() {
+            return Ok(Async::Ready(ProtocolsHandlerEvent::Custom(
+                self.events.remove(0),
+            )));
+        }
+
+        // Poll the future that fires when we need to identify the node again.
+        match self.next_id.poll()? {
+            Async::NotReady => Ok(Async::NotReady),
+            Async::Ready(()) => {
+                self.next_id.reset(Instant::now() + DELAY_TO_NEXT_ID);
+                let ev = ProtocolsHandlerEvent::OutboundSubstreamRequest {
+                    protocol: SubstreamProtocol::new(self.config.clone()),
+                    info: (),
+                };
+                Ok(Async::Ready(ev))
+            }
+        }
+    }
+}