// Copyright 2018 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate 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.

// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.

//! Aura (Authority-round) consensus in substrate.
//!
//! Aura works by having a list of authorities A who are expected to roughly
//! agree on the current time. Time is divided up into discrete slots of t
//! seconds each. For each slot s, the author of that slot is A[s % |A|].
//!
//! The author is allowed to issue one block but not more during that slot,
//! and it will be built upon the longest valid chain that has been seen.
//!
//! Blocks from future steps will be either deferred or rejected depending on how
//! far in the future they are.

use std::{sync::Arc, time::Duration, thread};

use parity_codec::Encode;
use consensus_common::{
	Authorities, BlockImport, Environment, Proposer, ForkChoiceStrategy
};
use consensus_common::import_queue::{Verifier, BasicQueue, SharedBlockImport, SharedJustificationImport};
use client::ChainHead;
use client::block_builder::api::{BlockBuilder as BlockBuilderApi, self as block_builder_api};
use client::runtime_api::ApiExt;
use consensus_common::{ImportBlock, BlockOrigin};
use runtime_primitives::{generic, generic::BlockId, Justification};
use runtime_primitives::traits::{
	Block, Header, Digest, DigestItemFor, DigestItem, ProvideRuntimeApi
};
use primitives::{Ed25519AuthorityId, ed25519};
use inherents::{InherentDataProviders, InherentData, RuntimeString};

use futures::{Stream, Future, IntoFuture, future};
use tokio::timer::Timeout;
use log::{warn, debug, info, trace};

use srml_aura::{
	InherentType as AuraInherent, AuraInherentData,
	timestamp::{TimestampInherentData, InherentType as TimestampInherent, InherentError as TIError}
};

use aura_slots::{CheckedHeader, SlotWorker, SlotInfo, SlotCompatible};

pub use aura_slots::SlotDuration;
pub use aura_primitives::*;
pub use consensus_common::SyncOracle;

/// A handle to the network. This is generally implemented by providing some
/// handle to a gossip service or similar.
///
/// Intended to be a lightweight handle such as an `Arc`.
pub trait Network: Clone {
	/// A stream of input messages for a topic.
	type In: Stream<Item=Vec<u8>,Error=()>;

	/// Send a message at a specific round out.
	fn send_message(&self, slot: u64, message: Vec<u8>);
}

/// Get slot author for given block along with authorities.
fn slot_author(slot_num: u64, authorities: &[Ed25519AuthorityId]) -> Option<Ed25519AuthorityId> {
	if authorities.is_empty() { return None }

	let idx = slot_num % (authorities.len() as u64);
	assert!(idx <= usize::max_value() as u64,
		"It is impossible to have a vector with length beyond the address space; qed");

	let current_author = *authorities.get(idx as usize)
		.expect("authorities not empty; index constrained to list length;\
				this is a valid index; qed");

	Some(current_author)
}

fn duration_now() -> Option<Duration> {
	use std::time::SystemTime;

	let now = SystemTime::now();
	now.duration_since(SystemTime::UNIX_EPOCH).map_err(|e| {
			warn!("Current time {:?} is before unix epoch. Something is wrong: {:?}", now, e);
	}).ok()
}

/// Get the slot for now.
fn slot_now(slot_duration: u64) -> Option<u64> {
	duration_now().map(|s| s.as_secs() / slot_duration)
}

fn inherent_to_common_error(err: RuntimeString) -> consensus_common::Error {
	consensus_common::ErrorKind::InherentData(err.into()).into()
}

/// A digest item which is usable with aura consensus.
pub trait CompatibleDigestItem: Sized {
	/// Construct a digest item which is a slot number and a signature on the
	/// hash.
	fn aura_seal(slot_number: u64, signature: ed25519::Signature) -> Self;

	/// If this item is an Aura seal, return the slot number and signature.
	fn as_aura_seal(&self) -> Option<(u64, &ed25519::Signature)>;
}

impl<Hash, AuthorityId> CompatibleDigestItem for generic::DigestItem<Hash, AuthorityId> {
	/// Construct a digest item which is a slot number and a signature on the
	/// hash.
	fn aura_seal(slot_number: u64, signature: ed25519::Signature) -> Self {
		generic::DigestItem::Seal(slot_number, signature)
	}
	/// If this item is an Aura seal, return the slot number and signature.
	fn as_aura_seal(&self) -> Option<(u64, &ed25519::Signature)> {
		match self {
			generic::DigestItem::Seal(slot, ref sign) => Some((*slot, sign)),
			_ => None
		}
	}
}

struct AuraSlotCompatible;

impl SlotCompatible for AuraSlotCompatible {
	fn extract_timestamp_and_slot(
		data: &InherentData
	) -> Result<(TimestampInherent, AuraInherent), consensus_common::Error> {
		data.timestamp_inherent_data()
			.and_then(|t| data.aura_inherent_data().map(|a| (t, a)))
			.map_err(inherent_to_common_error)
	}
}

/// Start the aura worker in a separate thread.
pub fn start_aura_thread<B, C, E, I, SO, Error, OnExit>(
	slot_duration: SlotDuration,
	local_key: Arc<ed25519::Pair>,
	client: Arc<C>,
	block_import: Arc<I>,
	env: Arc<E>,
	sync_oracle: SO,
	on_exit: OnExit,
	inherent_data_providers: InherentDataProviders,
) -> Result<(), consensus_common::Error> where
	B: Block + 'static,
	C: Authorities<B> + ChainHead<B> + Send + Sync + 'static,
	E: Environment<B, Error=Error> + Send + Sync + 'static,
	E::Proposer: Proposer<B, Error=Error> + Send + 'static,
	<<E::Proposer as Proposer<B>>::Create as IntoFuture>::Future: Send + 'static,
	I: BlockImport<B> + Send + Sync + 'static,
	Error: From<C::Error> + From<I::Error> + 'static,
	SO: SyncOracle + Send + Sync + Clone + 'static,
	OnExit: Future<Item=(), Error=()> + Send + 'static,
	DigestItemFor<B>: CompatibleDigestItem + DigestItem<AuthorityId=Ed25519AuthorityId> + 'static,
	Error: ::std::error::Error + Send + From<::consensus_common::Error> + 'static,
{
	let worker = AuraWorker {
		client: client.clone(), block_import, env, local_key, inherent_data_providers: inherent_data_providers.clone(), sync_oracle: sync_oracle.clone(),
	};

	aura_slots::start_slot_worker_thread::<_, _, _, _, AuraSlotCompatible, _>(
		slot_duration,
		client,
		Arc::new(worker),
		sync_oracle,
		on_exit,
		inherent_data_providers
	)
}

/// Start the aura worker. The returned future should be run in a tokio runtime.
pub fn start_aura<B, C, E, I, SO, Error, OnExit>(
	slot_duration: SlotDuration,
	local_key: Arc<ed25519::Pair>,
	client: Arc<C>,
	block_import: Arc<I>,
	env: Arc<E>,
	sync_oracle: SO,
	on_exit: OnExit,
	inherent_data_providers: InherentDataProviders,
) -> Result<impl Future<Item=(), Error=()>, consensus_common::Error> where
	B: Block,
	C: Authorities<B> + ChainHead<B>,
	E: Environment<B, Error=Error>,
	E::Proposer: Proposer<B, Error=Error>,
	<<E::Proposer as Proposer<B>>::Create as IntoFuture>::Future: Send + 'static,
	I: BlockImport<B> + Send + Sync + 'static,
	Error: From<C::Error> + From<I::Error>,
	SO: SyncOracle + Send + Sync + Clone,
	DigestItemFor<B>: CompatibleDigestItem + DigestItem<AuthorityId=Ed25519AuthorityId>,
	Error: ::std::error::Error + Send + 'static + From<::consensus_common::Error>,
	OnExit: Future<Item=(), Error=()>,
{
	let worker = AuraWorker {
		client: client.clone(), block_import, env, local_key, inherent_data_providers: inherent_data_providers.clone(), sync_oracle: sync_oracle.clone(),
	};
	aura_slots::start_slot_worker::<_, _, _, _, AuraSlotCompatible, _>(
		slot_duration,
		client,
		Arc::new(worker),
		sync_oracle,
		on_exit,
		inherent_data_providers
	)
}

struct AuraWorker<C, E, I, SO> {
	client: Arc<C>,
	block_import: Arc<I>,
	env: Arc<E>,
	local_key: Arc<ed25519::Pair>,
	sync_oracle: SO,
	inherent_data_providers: InherentDataProviders,
}

impl<B: Block, C, E, I, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, SO> where
	C: Authorities<B>,
	E: Environment<B, Error=Error>,
	E::Proposer: Proposer<B, Error=Error>,
	<<E::Proposer as Proposer<B>>::Create as IntoFuture>::Future: Send + 'static,
	I: BlockImport<B> + Send + Sync + 'static,
	Error: From<C::Error> + From<I::Error>,
	SO: SyncOracle + Send + Clone,
	DigestItemFor<B>: CompatibleDigestItem + DigestItem<AuthorityId=Ed25519AuthorityId>,
	Error: ::std::error::Error + Send + 'static + From<::consensus_common::Error>,
{
	type OnSlot = Box<Future<Item=(), Error=consensus_common::Error> + Send>;

	fn on_start(
		&self,
		slot_duration: u64
	) -> Result<(), consensus_common::Error> {
		register_aura_inherent_data_provider(&self.inherent_data_providers, slot_duration)
	}

	fn on_slot(
		&self,
		chain_head: B::Header,
		slot_info: SlotInfo,
	) -> Self::OnSlot {
		let pair = self.local_key.clone();
		let public_key = self.local_key.public();
		let client = self.client.clone();
		let block_import = self.block_import.clone();
		let env = self.env.clone();

		let (timestamp, slot_num, slot_duration) =
			(slot_info.timestamp, slot_info.number, slot_info.duration);

		let authorities = match client.authorities(&BlockId::Hash(chain_head.hash())) {
			Ok(authorities) => authorities,
			Err(e) => {
				warn!(
					"Unable to fetch authorities at block {:?}: {:?}",
					chain_head.hash(),
					e
				);
				return Box::new(future::ok(()));
			}
		};

		if self.sync_oracle.is_offline() && authorities.len() > 1 {
			debug!(target: "aura", "Skipping proposal slot. Waiting for the netork.");
			return Box::new(future::ok(()));
		}

		let proposal_work = match slot_author(slot_num, &authorities) {
			None => return Box::new(future::ok(())),
			Some(author) => if author.0 == public_key.0 {
				debug!(
					target: "aura", "Starting authorship at slot {}; timestamp = {}",
					slot_num,
					timestamp
				);

				// we are the slot author. make a block and sign it.
				let proposer = match env.init(&chain_head, &authorities) {
					Ok(p) => p,
					Err(e) => {
						warn!("Unable to author block in slot {:?}: {:?}", slot_num, e);
						return Box::new(future::ok(()))
					}
				};

				let remaining_duration = slot_info.remaining_duration();
				// deadline our production to approx. the end of the
				// slot
				Timeout::new(
					proposer.propose(slot_info.inherent_data, remaining_duration).into_future(),
					remaining_duration,
				)
			} else {
				return Box::new(future::ok(()));
			}
		};

		Box::new(
			proposal_work
				.map(move |b| {
					// minor hack since we don't have access to the timestamp
					// that is actually set by the proposer.
					let slot_after_building = slot_now(slot_duration);
					if slot_after_building != Some(slot_num) {
						info!(
							"Discarding proposal for slot {}; block production took too long",
							slot_num
						);
						return
					}

					let (header, body) = b.deconstruct();
					let header_num = header.number().clone();
					let pre_hash = header.hash();
					let parent_hash = header.parent_hash().clone();

					// sign the pre-sealed hash of the block and then
					// add it to a digest item.
					let to_sign = (slot_num, pre_hash).encode();
					let signature = pair.sign(&to_sign[..]);
					let item = <DigestItemFor<B> as CompatibleDigestItem>::aura_seal(
						slot_num,
						signature,
					);

					let import_block: ImportBlock<B> = ImportBlock {
						origin: BlockOrigin::Own,
						header,
						justification: None,
						post_digests: vec![item],
						body: Some(body),
						finalized: false,
						auxiliary: Vec::new(),
						fork_choice: ForkChoiceStrategy::LongestChain,
					};

					info!("Pre-sealed block for proposal at {}. Hash now {:?}, previously {:?}.",
						  header_num,
						  import_block.post_header().hash(),
						  pre_hash
					);

					if let Err(e) = block_import.import_block(import_block, None) {
						warn!(target: "aura", "Error with block built on {:?}: {:?}",
							  parent_hash, e);
					}
				})
				.map_err(|e| consensus_common::ErrorKind::ClientImport(format!("{:?}", e)).into())
		)
	}
}

/// check a header has been signed by the right key. If the slot is too far in the future, an error will be returned.
/// if it's successful, returns the pre-header, the slot number, and the signat.
//
// FIXME #1018 needs misbehavior types
fn check_header<B: Block>(slot_now: u64, mut header: B::Header, hash: B::Hash, authorities: &[Ed25519AuthorityId])
	-> Result<CheckedHeader<B::Header, ed25519::Signature>, String>
	where DigestItemFor<B>: CompatibleDigestItem
{
	let digest_item = match header.digest_mut().pop() {
		Some(x) => x,
		None => return Err(format!("Header {:?} is unsealed", hash)),
	};
	let (slot_num, &sig) = match digest_item.as_aura_seal() {
		Some(x) => x,
		None => return Err(format!("Header {:?} is unsealed", hash)),
	};

	if slot_num > slot_now {
		header.digest_mut().push(digest_item);
		Ok(CheckedHeader::Deferred(header, slot_num))
	} else {
		// check the signature is valid under the expected authority and
		// chain state.

		let expected_author = match slot_author(slot_num, &authorities) {
			None => return Err("Slot Author not found".to_string()),
			Some(author) => author
		};

		let pre_hash = header.hash();
		let to_sign = (slot_num, pre_hash).encode();
		let public = ed25519::Public(expected_author.0);

		if ed25519::verify_strong(&sig, &to_sign[..], public) {
			Ok(CheckedHeader::Checked(header, slot_num, sig))
		} else {
			Err(format!("Bad signature on {:?}", hash))
		}
	}
}

/// Extra verification for Aura blocks.
pub trait ExtraVerification<B: Block>: Send + Sync {
	/// Future that resolves when the block is verified or fails with error if not.
	type Verified: IntoFuture<Item=(),Error=String>;

	/// Do additional verification for this block.
	fn verify(
		&self,
		header: &B::Header,
		body: Option<&[B::Extrinsic]>,
	) -> Self::Verified;
}

/// A verifier for Aura blocks.
pub struct AuraVerifier<C, E> {
	client: Arc<C>,
	extra: E,
	inherent_data_providers: inherents::InherentDataProviders,
}

impl<C, E> AuraVerifier<C, E>
{
	fn check_inherents<B: Block>(
		&self,
		block: B,
		block_id: BlockId<B>,
		inherent_data: InherentData,
		timestamp_now: u64,
	) -> Result<(), String>
		where C: ProvideRuntimeApi, C::Api: BlockBuilderApi<B>
	{
		const MAX_TIMESTAMP_DRIFT_SECS: u64 = 60;

		let inherent_res = self.client.runtime_api().check_inherents(
			&block_id,
			block,
			inherent_data,
		).map_err(|e| format!("{:?}", e))?;

		if !inherent_res.ok() {
			inherent_res
				.into_errors()
				.try_for_each(|(i, e)| match TIError::try_from(&i, &e) {
					Some(TIError::ValidAtTimestamp(timestamp)) => {
						// halt import until timestamp is valid.
						// reject when too far ahead.
						if timestamp > timestamp_now + MAX_TIMESTAMP_DRIFT_SECS {
							return Err("Rejecting block too far in future".into());
						}

						let diff = timestamp.saturating_sub(timestamp_now);
						info!(
							target: "aura",
							"halting for block {} seconds in the future",
							diff
						);
						thread::sleep(Duration::from_secs(diff));
						Ok(())
					},
					Some(TIError::Other(e)) => Err(e.into()),
					None => Err(self.inherent_data_providers.error_to_string(&i, &e)),
				})
		} else {
			Ok(())
		}
	}

	#[allow(deprecated)]
	fn old_check_inherents<B: Block>(
		&self,
		block: B,
		block_id: BlockId<B>,
		inherent_data: InherentData,
		timestamp_now: u64,
	) -> Result<(), String>
		where C: ProvideRuntimeApi, C::Api: BlockBuilderApi<B>
	{
		use block_builder_api::{OldInherentData, OldCheckInherentError};
		const MAX_TIMESTAMP_DRIFT_SECS: u64 = 60;

		let (timestamp, slot) = AuraSlotCompatible::extract_timestamp_and_slot(&inherent_data).map_err(|e| format!("{:?}", e))?;
		let inherent_data = OldInherentData::new(timestamp, slot);

		let inherent_res = self.client.runtime_api().check_inherents_before_version_2(
			&block_id,
			block,
			inherent_data,
		).map_err(|e| format!("{:?}", e))?;

		match inherent_res {
			Ok(()) => Ok(()),
			Err(OldCheckInherentError::ValidAtTimestamp(timestamp)) => {
				// halt import until timestamp is valid.
				// reject when too far ahead.
				if timestamp > timestamp_now + MAX_TIMESTAMP_DRIFT_SECS {
					return Err("Rejecting block too far in future".into());
				}

				let diff = timestamp.saturating_sub(timestamp_now);
				info!(
					target: "aura",
					"halting for block {} seconds in the future",
					diff
				);
				thread::sleep(Duration::from_secs(diff));
				Ok(())
			},
			Err(OldCheckInherentError::Other(e)) => Err(e.into())
		}
	}
}

/// No-op extra verification.
#[derive(Debug, Clone, Copy)]
pub struct NothingExtra;

impl<B: Block> ExtraVerification<B> for NothingExtra {
	type Verified = Result<(), String>;

	fn verify(&self, _: &B::Header, _: Option<&[B::Extrinsic]>) -> Self::Verified {
		Ok(())
	}
}

impl<B: Block, C, E> Verifier<B> for AuraVerifier<C, E> where
	C: Authorities<B> + ProvideRuntimeApi + Send + Sync,
	C::Api: BlockBuilderApi<B>,
	DigestItemFor<B>: CompatibleDigestItem + DigestItem<AuthorityId=Ed25519AuthorityId>,
	E: ExtraVerification<B>,
{
	fn verify(
		&self,
		origin: BlockOrigin,
		header: B::Header,
		justification: Option<Justification>,
		mut body: Option<Vec<B::Extrinsic>>,
	) -> Result<(ImportBlock<B>, Option<Vec<Ed25519AuthorityId>>), String> {
		let mut inherent_data = self.inherent_data_providers.create_inherent_data().map_err(String::from)?;
		let (timestamp_now, slot_now) = AuraSlotCompatible::extract_timestamp_and_slot(&inherent_data)
			.map_err(|e| format!("Could not extract timestamp and slot: {:?}", e))?;
		let hash = header.hash();
		let parent_hash = *header.parent_hash();
		let authorities = self.client.authorities(&BlockId::Hash(parent_hash))
			.map_err(|e| format!("Could not fetch authorities at {:?}: {:?}", parent_hash, e))?;

		let extra_verification = self.extra.verify(
			&header,
			body.as_ref().map(|x| &x[..]),
		);

		// we add one to allow for some small drift.
		// FIXME #1019 in the future, alter this queue to allow deferring of headers
		let checked_header = check_header::<B>(slot_now + 1, header, hash, &authorities[..])?;
		match checked_header {
			CheckedHeader::Checked(pre_header, slot_num, sig) => {
				let item = <DigestItemFor<B>>::aura_seal(slot_num, sig);

				// if the body is passed through, we need to use the runtime
				// to check that the internally-set timestamp in the inherents
				// actually matches the slot set in the seal.
				if let Some(inner_body) = body.take() {
					inherent_data.aura_replace_inherent_data(slot_num);
					let block = B::new(pre_header.clone(), inner_body);

					if self.client
						.runtime_api()
						.has_api_with::<BlockBuilderApi<B>, _>(&BlockId::Hash(parent_hash), |v| v < 2)
						.map_err(|e| format!("{:?}", e))?
					{
						self.old_check_inherents(
							block.clone(),
							BlockId::Hash(parent_hash),
							inherent_data,
							timestamp_now,
						)?;
					} else {
						self.check_inherents(
							block.clone(),
							BlockId::Hash(parent_hash),
							inherent_data,
							timestamp_now,
						)?;
					}

					let (_, inner_body) = block.deconstruct();
					body = Some(inner_body);
				}

				trace!(target: "aura", "Checked {:?}; importing.", pre_header);

				extra_verification.into_future().wait()?;

				let import_block = ImportBlock {
					origin,
					header: pre_header,
					post_digests: vec![item],
					body,
					finalized: false,
					justification,
					auxiliary: Vec::new(),
					fork_choice: ForkChoiceStrategy::LongestChain,
				};

				// FIXME #1019 extract authorities
				Ok((import_block, None))
			}
			CheckedHeader::Deferred(a, b) => {
				debug!(target: "aura", "Checking {:?} failed; {:?}, {:?}.", hash, a, b);
				Err(format!("Header {:?} rejected: too far in the future", hash))
			}
		}
	}
}

/// The Aura import queue type.
pub type AuraImportQueue<B, C, E> = BasicQueue<B, AuraVerifier<C, E>>;

/// Register the aura inherent data provider, if not registered already.
fn register_aura_inherent_data_provider(
	inherent_data_providers: &InherentDataProviders,
	slot_duration: u64,
) -> Result<(), consensus_common::Error> {
	if !inherent_data_providers.has_provider(&srml_aura::INHERENT_IDENTIFIER) {
		inherent_data_providers
			.register_provider(srml_aura::InherentDataProvider::new(slot_duration))
			.map_err(inherent_to_common_error)
	} else {
		Ok(())
	}
}

/// Start an import queue for the Aura consensus algorithm.
pub fn import_queue<B, C, E>(
	slot_duration: SlotDuration,
	block_import: SharedBlockImport<B>,
	justification_import: Option<SharedJustificationImport<B>>,
	client: Arc<C>,
	extra: E,
	inherent_data_providers: InherentDataProviders,
) -> Result<AuraImportQueue<B, C, E>, consensus_common::Error> where
	B: Block,
	C: Authorities<B> + ProvideRuntimeApi + Send + Sync,
	C::Api: BlockBuilderApi<B>,
	DigestItemFor<B>: CompatibleDigestItem + DigestItem<AuthorityId=Ed25519AuthorityId>,
	E: ExtraVerification<B>,
{
	register_aura_inherent_data_provider(&inherent_data_providers, slot_duration.get())?;

	let verifier = Arc::new(
		AuraVerifier { client: client.clone(), extra, inherent_data_providers }
	);
	Ok(BasicQueue::new(verifier, block_import, justification_import))
}

#[cfg(test)]
mod tests {
	use super::*;
	use consensus_common::NoNetwork as DummyOracle;
	use network::test::*;
	use network::test::{Block as TestBlock, PeersClient};
	use runtime_primitives::traits::Block as BlockT;
	use network::config::ProtocolConfig;
	use parking_lot::Mutex;
	use tokio::runtime::current_thread;
	use keyring::Keyring;
	use client::BlockchainEvents;
	use test_client;

	type Error = ::client::error::Error;

	type TestClient = ::client::Client<test_client::Backend, test_client::Executor, TestBlock, test_client::runtime::RuntimeApi>;

	struct DummyFactory(Arc<TestClient>);
	struct DummyProposer(u64, Arc<TestClient>);

	impl Environment<TestBlock> for DummyFactory {
		type Proposer = DummyProposer;
		type Error = Error;

		fn init(&self, parent_header: &<TestBlock as BlockT>::Header, _authorities: &[Ed25519AuthorityId])
			-> Result<DummyProposer, Error>
		{
			Ok(DummyProposer(parent_header.number + 1, self.0.clone()))
		}
	}

	impl Proposer<TestBlock> for DummyProposer {
		type Error = Error;
		type Create = Result<TestBlock, Error>;

		fn propose(&self, _: InherentData, _: Duration) -> Result<TestBlock, Error> {
			self.1.new_block().unwrap().bake().map_err(|e| e.into())
		}
	}

	const SLOT_DURATION: u64 = 1;
	const TEST_ROUTING_INTERVAL: Duration = Duration::from_millis(50);

	pub struct AuraTestNet {
		peers: Vec<Arc<Peer<AuraVerifier<
			PeersClient,
			NothingExtra,
		>, ()>>>,
		started: bool,
	}

	impl TestNetFactory for AuraTestNet {
		type Verifier = AuraVerifier<PeersClient, NothingExtra>;
		type PeerData = ();

		/// Create new test network with peers and given config.
		fn from_config(_config: &ProtocolConfig) -> Self {
			AuraTestNet {
				peers: Vec::new(),
				started: false,
			}
		}

		fn make_verifier(&self, client: Arc<PeersClient>, _cfg: &ProtocolConfig)
			-> Arc<Self::Verifier>
		{
			let slot_duration = SlotDuration::get_or_compute(&*client)
				.expect("slot duration available");
			let inherent_data_providers = InherentDataProviders::new();
			register_aura_inherent_data_provider(
				&inherent_data_providers,
				slot_duration.get()
			).expect("Registers aura inherent data provider");

			assert_eq!(slot_duration.get(), SLOT_DURATION);
			Arc::new(AuraVerifier {
				client,
				extra: NothingExtra,
				inherent_data_providers,
			})
		}

		fn peer(&self, i: usize) -> &Peer<Self::Verifier, ()> {
			&self.peers[i]
		}

		fn peers(&self) -> &Vec<Arc<Peer<Self::Verifier, ()>>> {
			&self.peers
		}

		fn mut_peers<F: Fn(&mut Vec<Arc<Peer<Self::Verifier, ()>>>)>(&mut self, closure: F) {
			closure(&mut self.peers);
		}

		fn started(&self) -> bool {
			self.started
		}

		fn set_started(&mut self, new: bool) {
			self.started = new;
		}
	}

	#[test]
	fn authoring_blocks() {
		let _ = ::env_logger::try_init();
		let mut net = AuraTestNet::new(3);

		net.start();

		let peers = &[
			(0, Keyring::Alice),
			(1, Keyring::Bob),
			(2, Keyring::Charlie),
		];

		let net = Arc::new(Mutex::new(net));
		let mut import_notifications = Vec::new();

		let mut runtime = current_thread::Runtime::new().unwrap();
		for (peer_id, key) in peers {
			let client = net.lock().peer(*peer_id).client().clone();
			let environ = Arc::new(DummyFactory(client.clone()));
			import_notifications.push(
				client.import_notification_stream()
					.take_while(|n| Ok(!(n.origin != BlockOrigin::Own && n.header.number() < &5)))
					.for_each(move |_| Ok(()))
			);

			let slot_duration = SlotDuration::get_or_compute(&*client)
				.expect("slot duration available");

			let inherent_data_providers = InherentDataProviders::new();
			register_aura_inherent_data_provider(
				&inherent_data_providers, slot_duration.get()
			).expect("Registers aura inherent data provider");

			let aura = start_aura(
				slot_duration,
				Arc::new(key.clone().into()),
				client.clone(),
				client,
				environ.clone(),
				DummyOracle,
				futures::empty(),
				inherent_data_providers,
			).expect("Starts aura");

			runtime.spawn(aura);
		}

		// wait for all finalized on each.
		let wait_for = ::futures::future::join_all(import_notifications)
			.map(|_| ())
			.map_err(|_| ());

		let drive_to_completion = ::tokio::timer::Interval::new_interval(TEST_ROUTING_INTERVAL)
			.for_each(move |_| {
				net.lock().send_import_notifications();
				net.lock().route_fast();
				Ok(())
			})
			.map(|_| ())
			.map_err(|_| ());

		runtime.block_on(wait_for.select(drive_to_completion).map_err(|_| ())).unwrap();
	}
}
