// This file is part of Substrate.

// Copyright (C) 2019-2021 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

use crate::{
	config::ProtocolId,
	bitswap::Bitswap,
	discovery::{DiscoveryBehaviour, DiscoveryConfig, DiscoveryOut},
	protocol::{message::Roles, CustomMessageOutcome, NotificationsSink, Protocol},
	peer_info, request_responses, light_client_requests,
	ObservedRole, DhtEvent,
};

use bytes::Bytes;
use futures::{channel::oneshot, stream::StreamExt};
use libp2p::NetworkBehaviour;
use libp2p::core::{Multiaddr, PeerId, PublicKey};
use libp2p::identify::IdentifyInfo;
use libp2p::kad::record;
use libp2p::swarm::{
	NetworkBehaviourAction, NetworkBehaviourEventProcess, PollParameters, toggle::Toggle
};
use log::debug;
use prost::Message;
use sp_consensus::{BlockOrigin, import_queue::{IncomingBlock, Origin}};
use sp_runtime::{traits::{Block as BlockT, NumberFor}, Justifications};
use std::{
	borrow::Cow,
	collections::{HashSet, VecDeque},
	iter,
	task::{Context, Poll},
	time::Duration,
};

pub use crate::request_responses::{
	ResponseFailure, InboundFailure, RequestFailure, OutboundFailure, RequestId,
	IfDisconnected
};

/// General behaviour of the network. Combines all protocols together.
#[derive(NetworkBehaviour)]
#[behaviour(out_event = "BehaviourOut<B>", poll_method = "poll")]
pub struct Behaviour<B: BlockT> {
	/// All the substrate-specific protocols.
	substrate: Protocol<B>,
	/// Periodically pings and identifies the nodes we are connected to, and store information in a
	/// cache.
	peer_info: peer_info::PeerInfoBehaviour,
	/// Discovers nodes of the network.
	discovery: DiscoveryBehaviour,
	/// Bitswap server for blockchain data.
	bitswap: Toggle<Bitswap<B>>,
	/// Generic request-reponse protocols.
	request_responses: request_responses::RequestResponsesBehaviour,

	/// Queue of events to produce for the outside.
	#[behaviour(ignore)]
	events: VecDeque<BehaviourOut<B>>,

	/// Light client request handling.
	#[behaviour(ignore)]
	light_client_request_sender: light_client_requests::sender::LightClientRequestSender<B>,

	/// Protocol name used to send out block requests via
	/// [`request_responses::RequestResponsesBehaviour`].
	#[behaviour(ignore)]
	block_request_protocol_name: String,
}

/// Event generated by `Behaviour`.
pub enum BehaviourOut<B: BlockT> {
	BlockImport(BlockOrigin, Vec<IncomingBlock<B>>),
	JustificationImport(Origin, B::Hash, NumberFor<B>, Justifications),

	/// Started a random iterative Kademlia discovery query.
	RandomKademliaStarted(ProtocolId),

	/// We have received a request from a peer and answered it.
	///
	/// This event is generated for statistics purposes.
	InboundRequest {
		/// Peer which sent us a request.
		peer: PeerId,
		/// Protocol name of the request.
		protocol: Cow<'static, str>,
		/// If `Ok`, contains the time elapsed between when we received the request and when we
		/// sent back the response. If `Err`, the error that happened.
		result: Result<Duration, ResponseFailure>,
	},

	/// A request has succeeded or failed.
	///
	/// This event is generated for statistics purposes.
	RequestFinished {
		/// Peer that we send a request to.
		peer: PeerId,
		/// Name of the protocol in question.
		protocol: Cow<'static, str>,
		/// Duration the request took.
		duration: Duration,
		/// Result of the request.
		result: Result<(), RequestFailure>,
	},

	/// Opened a substream with the given node with the given notifications protocol.
	///
	/// The protocol is always one of the notification protocols that have been registered.
	NotificationStreamOpened {
		/// Node we opened the substream with.
		remote: PeerId,
		/// The concerned protocol. Each protocol uses a different substream.
		protocol: Cow<'static, str>,
		/// If the negotiation didn't use the main name of the protocol (the one in
		/// `notifications_protocol`), then this field contains which name has actually been
		/// used.
		/// See also [`crate::Event::NotificationStreamOpened`].
		negotiated_fallback: Option<Cow<'static, str>>,
		/// Object that permits sending notifications to the peer.
		notifications_sink: NotificationsSink,
		/// Role of the remote.
		role: ObservedRole,
	},

	/// The [`NotificationsSink`] object used to send notifications with the given peer must be
	/// replaced with a new one.
	///
	/// This event is typically emitted when a transport-level connection is closed and we fall
	/// back to a secondary connection.
	NotificationStreamReplaced {
		/// Id of the peer we are connected to.
		remote: PeerId,
		/// The concerned protocol. Each protocol uses a different substream.
		protocol: Cow<'static, str>,
		/// Replacement for the previous [`NotificationsSink`].
		notifications_sink: NotificationsSink,
	},

	/// Closed a substream with the given node. Always matches a corresponding previous
	/// `NotificationStreamOpened` message.
	NotificationStreamClosed {
		/// Node we closed the substream with.
		remote: PeerId,
		/// The concerned protocol. Each protocol uses a different substream.
		protocol: Cow<'static, str>,
	},

	/// Received one or more messages from the given node using the given protocol.
	NotificationsReceived {
		/// Node we received the message from.
		remote: PeerId,
		/// Concerned protocol and associated message.
		messages: Vec<(Cow<'static, str>, Bytes)>,
	},

	/// Now connected to a new peer for syncing purposes.
	SyncConnected(PeerId),

	/// No longer connected to a peer for syncing purposes.
	SyncDisconnected(PeerId),

	/// Events generated by a DHT as a response to get_value or put_value requests as well as the
	/// request duration.
	Dht(DhtEvent, Duration),
}

impl<B: BlockT> Behaviour<B> {
	/// Builds a new `Behaviour`.
	pub fn new(
		substrate: Protocol<B>,
		user_agent: String,
		local_public_key: PublicKey,
		light_client_request_sender: light_client_requests::sender::LightClientRequestSender<B>,
		disco_config: DiscoveryConfig,
		block_request_protocol_config: request_responses::ProtocolConfig,
		bitswap: Option<Bitswap<B>>,
		light_client_request_protocol_config: request_responses::ProtocolConfig,
		// All remaining request protocol configs.
		mut request_response_protocols: Vec<request_responses::ProtocolConfig>,
	) -> Result<Self, request_responses::RegisterError> {
		// Extract protocol name and add to `request_response_protocols`.
		let block_request_protocol_name = block_request_protocol_config.name.to_string();
		request_response_protocols.push(block_request_protocol_config);

		request_response_protocols.push(light_client_request_protocol_config);

		Ok(Behaviour {
			substrate,
			peer_info: peer_info::PeerInfoBehaviour::new(user_agent, local_public_key),
			discovery: disco_config.finish(),
			bitswap: bitswap.into(),
			request_responses:
				request_responses::RequestResponsesBehaviour::new(request_response_protocols.into_iter())?,
			light_client_request_sender,
			events: VecDeque::new(),

			block_request_protocol_name,
		})
	}

	/// Returns the list of nodes that we know exist in the network.
	pub fn known_peers(&mut self) -> HashSet<PeerId> {
		self.discovery.known_peers()
	}

	/// Adds a hard-coded address for the given peer, that never expires.
	pub fn add_known_address(&mut self, peer_id: PeerId, addr: Multiaddr) {
		self.discovery.add_known_address(peer_id, addr)
	}

	/// Returns the number of nodes in each Kademlia kbucket for each Kademlia instance.
	///
	/// Identifies Kademlia instances by their [`ProtocolId`] and kbuckets by the base 2 logarithm
	/// of their lower bound.
	pub fn num_entries_per_kbucket(&mut self) -> impl ExactSizeIterator<Item = (&ProtocolId, Vec<(u32, usize)>)> {
		self.discovery.num_entries_per_kbucket()
	}

	/// Returns the number of records in the Kademlia record stores.
	pub fn num_kademlia_records(&mut self) -> impl ExactSizeIterator<Item = (&ProtocolId, usize)> {
		self.discovery.num_kademlia_records()
	}

	/// Returns the total size in bytes of all the records in the Kademlia record stores.
	pub fn kademlia_records_total_size(&mut self) -> impl ExactSizeIterator<Item = (&ProtocolId, usize)> {
		self.discovery.kademlia_records_total_size()
	}

	/// Borrows `self` and returns a struct giving access to the information about a node.
	///
	/// Returns `None` if we don't know anything about this node. Always returns `Some` for nodes
	/// we're connected to, meaning that if `None` is returned then we're not connected to that
	/// node.
	pub fn node(&self, peer_id: &PeerId) -> Option<peer_info::Node> {
		self.peer_info.node(peer_id)
	}

	/// Initiates sending a request.
	pub fn send_request(
		&mut self,
		target: &PeerId,
		protocol: &str,
		request: Vec<u8>,
		pending_response: oneshot::Sender<Result<Vec<u8>, RequestFailure>>,
		connect: IfDisconnected,
	) {
		self.request_responses.send_request(target, protocol, request, pending_response, connect)
	}

	/// Returns a shared reference to the user protocol.
	pub fn user_protocol(&self) -> &Protocol<B> {
		&self.substrate
	}

	/// Returns a mutable reference to the user protocol.
	pub fn user_protocol_mut(&mut self) -> &mut Protocol<B> {
		&mut self.substrate
	}

	/// Start querying a record from the DHT. Will later produce either a `ValueFound` or a `ValueNotFound` event.
	pub fn get_value(&mut self, key: &record::Key) {
		self.discovery.get_value(key);
	}

	/// Starts putting a record into DHT. Will later produce either a `ValuePut` or a `ValuePutFailed` event.
	pub fn put_value(&mut self, key: record::Key, value: Vec<u8>) {
		self.discovery.put_value(key, value);
	}

	/// Issue a light client request.
	pub fn light_client_request(
		&mut self,
		r: light_client_requests::sender::Request<B>,
	) -> Result<(), light_client_requests::sender::SendRequestError> {
		self.light_client_request_sender.request(r)
	}
}

fn reported_roles_to_observed_role(roles: Roles) -> ObservedRole {
	if roles.is_authority() {
		ObservedRole::Authority
	} else if roles.is_full() {
		ObservedRole::Full
	} else {
		ObservedRole::Light
	}
}

impl<B: BlockT> NetworkBehaviourEventProcess<void::Void> for
Behaviour<B> {
	fn inject_event(&mut self, event: void::Void) {
		void::unreachable(event)
	}
}

impl<B: BlockT> NetworkBehaviourEventProcess<CustomMessageOutcome<B>> for
Behaviour<B> {
	fn inject_event(&mut self, event: CustomMessageOutcome<B>) {
		match event {
			CustomMessageOutcome::BlockImport(origin, blocks) =>
				self.events.push_back(BehaviourOut::BlockImport(origin, blocks)),
			CustomMessageOutcome::JustificationImport(origin, hash, nb, justification) =>
				self.events.push_back(BehaviourOut::JustificationImport(origin, hash, nb, justification)),
			CustomMessageOutcome::BlockRequest { target, request, pending_response } => {
				let mut buf = Vec::with_capacity(request.encoded_len());
				if let Err(err) = request.encode(&mut buf) {
					log::warn!(
						target: "sync",
						"Failed to encode block request {:?}: {:?}",
						request, err
					);
					return
				}

				self.request_responses.send_request(
					&target, &self.block_request_protocol_name, buf, pending_response, IfDisconnected::ImmediateError,
				);
			},
			CustomMessageOutcome::NotificationStreamOpened {
				remote, protocol, negotiated_fallback, roles, notifications_sink
			} => {
				self.events.push_back(BehaviourOut::NotificationStreamOpened {
					remote,
					protocol,
					negotiated_fallback,
					role: reported_roles_to_observed_role(roles),
					notifications_sink: notifications_sink.clone(),
				});
			},
			CustomMessageOutcome::NotificationStreamReplaced { remote, protocol, notifications_sink } =>
				self.events.push_back(BehaviourOut::NotificationStreamReplaced {
					remote,
					protocol,
					notifications_sink,
				}),
			CustomMessageOutcome::NotificationStreamClosed { remote, protocol } =>
				self.events.push_back(BehaviourOut::NotificationStreamClosed {
					remote,
					protocol,
				}),
			CustomMessageOutcome::NotificationsReceived { remote, messages } => {
				self.events.push_back(BehaviourOut::NotificationsReceived { remote, messages });
			},
			CustomMessageOutcome::PeerNewBest(peer_id, number) => {
				self.light_client_request_sender.update_best_block(&peer_id, number);
			}
			CustomMessageOutcome::SyncConnected(peer_id) => {
				self.light_client_request_sender.inject_connected(peer_id);
				self.events.push_back(BehaviourOut::SyncConnected(peer_id))
			}
			CustomMessageOutcome::SyncDisconnected(peer_id) => {
				self.light_client_request_sender.inject_disconnected(peer_id);
				self.events.push_back(BehaviourOut::SyncDisconnected(peer_id))
			}
			CustomMessageOutcome::None => {}
		}
	}
}

impl<B: BlockT> NetworkBehaviourEventProcess<request_responses::Event> for Behaviour<B> {
	fn inject_event(&mut self, event: request_responses::Event) {
		match event {
			request_responses::Event::InboundRequest { peer, protocol, result } => {
				self.events.push_back(BehaviourOut::InboundRequest {
					peer,
					protocol,
					result,
				});
			}
			request_responses::Event::RequestFinished { peer, protocol, duration, result } => {
				self.events.push_back(BehaviourOut::RequestFinished {
					peer, protocol, duration, result,
				});
			},
			request_responses::Event::ReputationChanges { peer, changes } => {
				for change in changes {
					self.substrate.report_peer(peer, change);
				}
			}
		}
	}
}

impl<B: BlockT> NetworkBehaviourEventProcess<peer_info::PeerInfoEvent>
	for Behaviour<B> {
	fn inject_event(&mut self, event: peer_info::PeerInfoEvent) {
		let peer_info::PeerInfoEvent::Identified {
			peer_id,
			info: IdentifyInfo {
				protocol_version,
				agent_version,
				mut listen_addrs,
				protocols,
				..
			},
		} = event;

		if listen_addrs.len() > 30 {
			debug!(
				target: "sub-libp2p",
				"Node {:?} has reported more than 30 addresses; it is identified by {:?} and {:?}",
				peer_id, protocol_version, agent_version
			);
			listen_addrs.truncate(30);
		}

		for addr in listen_addrs {
			self.discovery.add_self_reported_address(&peer_id, protocols.iter(), addr);
		}
		self.substrate.add_default_set_discovered_nodes(iter::once(peer_id));
	}
}

impl<B: BlockT> NetworkBehaviourEventProcess<DiscoveryOut>
	for Behaviour<B> {
	fn inject_event(&mut self, out: DiscoveryOut) {
		match out {
			DiscoveryOut::UnroutablePeer(_peer_id) => {
				// Obtaining and reporting listen addresses for unroutable peers back
				// to Kademlia is handled by the `Identify` protocol, part of the
				// `PeerInfoBehaviour`. See the `NetworkBehaviourEventProcess`
				// implementation for `PeerInfoEvent`.
			}
			DiscoveryOut::Discovered(peer_id) => {
				self.substrate.add_default_set_discovered_nodes(iter::once(peer_id));
			}
			DiscoveryOut::ValueFound(results, duration) => {
				self.events.push_back(BehaviourOut::Dht(DhtEvent::ValueFound(results), duration));
			}
			DiscoveryOut::ValueNotFound(key, duration) => {
				self.events.push_back(BehaviourOut::Dht(DhtEvent::ValueNotFound(key), duration));
			}
			DiscoveryOut::ValuePut(key, duration) => {
				self.events.push_back(BehaviourOut::Dht(DhtEvent::ValuePut(key), duration));
			}
			DiscoveryOut::ValuePutFailed(key, duration) => {
				self.events.push_back(BehaviourOut::Dht(DhtEvent::ValuePutFailed(key), duration));
			}
			DiscoveryOut::RandomKademliaStarted(protocols) => {
				for protocol in protocols {
					self.events.push_back(BehaviourOut::RandomKademliaStarted(protocol));
				}
			}
		}
	}
}

impl<B: BlockT> Behaviour<B> {
	fn poll<TEv>(
		&mut self,
		cx: &mut Context,
		_: &mut impl PollParameters,
	) -> Poll<NetworkBehaviourAction<TEv, BehaviourOut<B>>> {
		use light_client_requests::sender::OutEvent;
		while let Poll::Ready(Some(event)) =
			self.light_client_request_sender.poll_next_unpin(cx)
		{
			match event {
				OutEvent::SendRequest {
					target,
					request,
					pending_response,
					protocol_name,
				} => self.request_responses.send_request(
					&target,
					&protocol_name,
					request,
					pending_response,
					IfDisconnected::ImmediateError,
				),
			}
		}

		if let Some(event) = self.events.pop_front() {
			return Poll::Ready(NetworkBehaviourAction::GenerateEvent(event))
		}

		Poll::Pending
	}
}