Use BTreeMap rather than HashMap in demo runtime.

polkadot/api/Cargo.toml

@@ -11,3 +11,6 @@ polkadot-primitives = { path = "../primitives" }
 substrate-client = { path = "../../substrate/client" }
 substrate-executor = { path = "../../substrate/executor" }
 substrate-state-machine = { path = "../../substrate/state-machine" }
+
+[dev-dependencies]
+substrate-keyring = { path = "../../substrate/keyring" }

polkadot/api/src/lib.rs

@@ -18,7 +18,7 @@
 //! runtime.
 
 extern crate polkadot_executor as polkadot_executor;
-extern crate polkadot_runtime ;
+extern crate polkadot_runtime;
 extern crate polkadot_primitives as primitives;
 extern crate substrate_client as client;
 extern crate substrate_executor as substrate_executor;
@@ -27,13 +27,18 @@ extern crate substrate_state_machine as state_machine;
 #[macro_use]
 extern crate error_chain;
 
+#[cfg(test)]
+extern crate substrate_keyring as keyring;
+
 use client::backend::Backend;
 use client::Client;
 use polkadot_runtime::runtime;
 use polkadot_executor::Executor as LocalDispatch;
 use substrate_executor::{NativeExecutionDispatch, NativeExecutor};
-use primitives::{AccountId, SessionKey};
-use primitives::block::Id as BlockId;
+use state_machine::OverlayedChanges;
+use primitives::{AccountId, SessionKey, Timestamp};
+use primitives::block::{Id as BlockId, Block, Header, Body};
+use primitives::transaction::UncheckedTransaction;
 use primitives::parachain::DutyRoster;
 
 error_chain! {
@@ -43,10 +48,21 @@ error_chain! {
 			description("Unknown runtime code")
 			display("Unknown runtime code")
 		}
+		/// Unknown block ID.
 		UnknownBlock(b: BlockId) {
 			description("Unknown block")
 			display("Unknown block")
 		}
+		/// Attempted to push an inherent transaction manually.
+		PushedInherentTransaction(tx: UncheckedTransaction) {
+			description("Attempted to push an inherent transaction to a block."),
+			display("Pushed inherent transaction to a block: {:?}", tx),
+		}
+		/// Badly-formed transaction.
+		BadlyFormedTransaction(tx: UncheckedTransaction) {
+			description("Attempted to push a badly-formed transaction to a block."),
+			display("Pushed badly-formed transaction to a block: {:?}", tx),
+		}
 		/// Some other error.
 		// TODO: allow to be specified as associated type of PolkadotApi
 		Other(e: Box<::std::error::Error + Send>) {
@@ -60,10 +76,29 @@ error_chain! {
 	}
 }
 
+impl From<client::error::Error> for Error {
+	fn from(e: client::error::Error) -> Error {
+		match e {
+			client::error::Error(client::error::ErrorKind::UnknownBlock(b), _) => Error::from_kind(ErrorKind::UnknownBlock(b)),
+			other => Error::from_kind(ErrorKind::Other(Box::new(other) as Box<_>)),
+		}
+	}
+}
+
+pub trait BlockBuilder: Sized {
+	/// Push a non-inherent transaction.
+	fn push_transaction(&mut self, transaction: UncheckedTransaction) -> Result<()>;
+
+	/// Finalise the block.
+	fn bake(self) -> Block;
+}
+
 /// Trait encapsulating the Polkadot API.
 ///
 /// All calls should fail when the exact runtime is unknown.
 pub trait PolkadotApi {
+	type BlockBuilder: BlockBuilder;
+
 	/// Get session keys at a given block.
 	fn session_keys(&self, at: &BlockId) -> Result<Vec<SessionKey>>;
 
@@ -72,24 +107,26 @@ pub trait PolkadotApi {
 
 	/// Get the authority duty roster at a block.
 	fn duty_roster(&self, at: &BlockId) -> Result<DutyRoster>;
-}
 
-fn convert_client_error(e: client::error::Error) -> Error {
-	match e {
-		client::error::Error(client::error::ErrorKind::UnknownBlock(b), _) => Error::from_kind(ErrorKind::UnknownBlock(b)),
-		other => Error::from_kind(ErrorKind::Other(Box::new(other) as Box<_>)),
-	}
+	/// Get the timestamp registered at a block.
+	fn timestamp(&self, at: &BlockId) -> Result<Timestamp>;
+
+	/// Evaluate a block and see if it gives an error.
+	fn evaluate_block(&self, at: &BlockId, block: Block) -> Result<()>;
+
+	/// Create a block builder on top of the parent block.
+	fn build_block(&self, parent: &BlockId, timestamp: u64) -> Result<Self::BlockBuilder>;
 }
 
 // set up the necessary scaffolding to execute the runtime.
 macro_rules! with_runtime {
 	($client: ident, $at: expr, $exec: expr) => {{
 		// bail if the code is not the same as the natively linked.
-		if $client.code_at($at).map_err(convert_client_error)? != LocalDispatch::native_equivalent() {
+		if $client.code_at($at)? != LocalDispatch::native_equivalent() {
 			bail!(ErrorKind::UnknownRuntime);
 		}
 
-		$client.state_at($at).map_err(convert_client_error).and_then(|state| {
+		$client.state_at($at).map_err(Error::from).and_then(|state| {
 			let mut changes = Default::default();
 			let mut ext = state_machine::Ext {
 				overlay: &mut changes,
@@ -104,6 +141,8 @@ macro_rules! with_runtime {
 impl<B: Backend> PolkadotApi for Client<B, NativeExecutor<LocalDispatch>>
 	where ::client::error::Error: From<<<B as Backend>::State as state_machine::backend::Backend>::Error>
 {
+	type BlockBuilder = ClientBlockBuilder<B::State>;
+
 	fn session_keys(&self, at: &BlockId) -> Result<Vec<SessionKey>> {
 		with_runtime!(self, at, ::runtime::consensus::authorities)
 	}
@@ -115,4 +154,185 @@ impl<B: Backend> PolkadotApi for Client<B, NativeExecutor<LocalDispatch>>
 	fn duty_roster(&self, at: &BlockId) -> Result<DutyRoster> {
 		with_runtime!(self, at, ::runtime::parachains::calculate_duty_roster)
 	}
+
+	fn timestamp(&self, at: &BlockId) -> Result<Timestamp> {
+		with_runtime!(self, at, ::runtime::timestamp::get)
+	}
+
+	fn evaluate_block(&self, at: &BlockId, block: Block) -> Result<()> {
+		with_runtime!(self, at, || ::runtime::system::internal::execute_block(block))
+	}
+
+	fn build_block(&self, parent: &BlockId, timestamp: Timestamp) -> Result<Self::BlockBuilder> {
+		if self.code_at(parent)? != LocalDispatch::native_equivalent() {
+			bail!(ErrorKind::UnknownRuntime);
+		}
+
+		let header = Header {
+			parent_hash: self.block_hash_from_id(parent)?.ok_or(ErrorKind::UnknownBlock(*parent))?,
+			number: self.block_number_from_id(parent)?.ok_or(ErrorKind::UnknownBlock(*parent))? + 1,
+			state_root: Default::default(),
+			transaction_root: Default::default(),
+			digest: Default::default(),
+		};
+
+		let body = Body {
+			timestamp: timestamp,
+			transactions: Vec::new(),
+		};
+
+		let mut builder = ClientBlockBuilder {
+			parent: *parent,
+			changes: OverlayedChanges::default(),
+			state: self.state_at(parent)?,
+			header,
+			timestamp,
+			transactions: Vec::new(),
+		};
+
+		for inherent in body.inherent_transactions() {
+			builder.execute_transaction(inherent)?;
+		}
+
+		Ok(builder)
+	}
+}
+
+/// A polkadot block builder.
+#[derive(Debug, Clone)]
+pub struct ClientBlockBuilder<S> {
+	parent: BlockId,
+	changes: OverlayedChanges,
+	state: S,
+	header: Header,
+	timestamp: Timestamp,
+	transactions: Vec<UncheckedTransaction>,
+}
+
+impl<S: state_machine::Backend> ClientBlockBuilder<S>
+	where S::Error: Into<client::error::Error>
+{
+	// executes a transaction, inherent or otherwise, without appending to the list
+	fn execute_transaction(&mut self, transaction: UncheckedTransaction) -> Result<()> {
+		if !transaction.is_well_formed() {
+			bail!(ErrorKind::BadlyFormedTransaction(transaction));
+		}
+
+		let mut ext = state_machine::Ext {
+			overlay: &mut self.changes,
+			backend: &self.state,
+		};
+
+		// TODO: avoid clone
+		let header = self.header.clone();
+		let result = ::substrate_executor::with_native_environment(
+			&mut ext,
+			move || runtime::system::internal::execute_transaction(transaction, header),
+		).map_err(Into::into);
+
+		match result {
+			Ok(header) => {
+				ext.overlay.commit_prospective();
+				self.header = header;
+				Ok(())
+			}
+			Err(e) => {
+				ext.overlay.discard_prospective();
+				Err(e)
+			}
+		}
+	}
+}
+
+impl<S: state_machine::Backend> BlockBuilder for ClientBlockBuilder<S>
+	where S::Error: Into<client::error::Error>
+{
+	fn push_transaction(&mut self, transaction: UncheckedTransaction) -> Result<()> {
+		if transaction.transaction.function.is_inherent() {
+			bail!(ErrorKind::PushedInherentTransaction(transaction));
+		} else {
+			self.execute_transaction(transaction.clone())?;
+			self.transactions.push(transaction);
+			Ok(())
+		}
+	}
+
+	fn bake(mut self) -> Block {
+		let mut ext = state_machine::Ext {
+			overlay: &mut self.changes,
+			backend: &self.state,
+		};
+
+		let old_header = self.header;
+		let final_header = ::substrate_executor::with_native_environment(
+			&mut ext,
+			move || runtime::system::internal::finalise_block(old_header)
+		).expect("all inherent transactions pushed; all other transactions executed correctly; qed");
+
+		Block {
+			header: final_header,
+			body: Body {
+				timestamp: self.timestamp,
+				transactions: self.transactions,
+			}
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use client::in_mem::Backend as InMemory;
+	use polkadot_runtime::genesismap::{additional_storage_with_genesis, GenesisConfig};
+	use substrate_executor::NativeExecutionDispatch;
+	use keyring::Keyring;
+
+	fn validators() -> Vec<AccountId> {
+		vec![
+			Keyring::One.to_raw_public(),
+			Keyring::Two.to_raw_public(),
+		]
+	}
+
+	fn client() -> Client<InMemory, NativeExecutor<LocalDispatch>> {
+		::client::new_in_mem(
+			LocalDispatch::new(),
+			|| {
+				let config = GenesisConfig::new_simple(validators(), 100);
+
+				// override code entry.
+				let mut storage = config.genesis_map();
+				storage.insert(b":code".to_vec(), LocalDispatch::native_equivalent().to_vec());
+
+				let block = ::client::genesis::construct_genesis_block(
+					&config.genesis_map()
+				);
+				storage.extend(additional_storage_with_genesis(&block));
+				(block.header, storage.into_iter().collect())
+			}
+		).unwrap()
+	}
+
+	#[test]
+	fn gets_session_and_validator_keys() {
+		let client = client();
+		assert_eq!(client.session_keys(&BlockId::Number(0)).unwrap(), validators());
+		assert_eq!(client.validators(&BlockId::Number(0)).unwrap(), validators());
+	}
+
+	#[test]
+	fn build_block() {
+		let client = client();
+
+		let block_builder = client.build_block(&BlockId::Number(0), 1_000_000).unwrap();
+		let block = block_builder.bake();
+
+		assert_eq!(block.header.number, 1);
+	}
+
+	#[test]
+	fn cannot_build_block_on_unknown_parent() {
+		let client = client();
+		assert!(client.build_block(&BlockId::Number(100), 1_000_000).is_err());
+	}
 }

polkadot/collator/src/lib.rs

@@ -61,7 +61,7 @@ pub trait ParachainContext {
 	fn produce_candidate<I: IntoIterator<Item=(ParaId, Message)>>(
 		&self,
 		ingress: I,
-	) -> (parachain::BlockData, polkadot_primitives::Signature);
+	) -> (parachain::BlockData, polkadot_primitives::AccountId, polkadot_primitives::Signature);
 }
 
 /// Relay chain context needed to collate.
@@ -131,7 +131,7 @@ pub fn collate<'a, R, P>(local_id: ParaId, relay_context: R, para_context: P)
 		P: ParachainContext + 'a,
 {
 	Box::new(collate_ingress(relay_context).map(move |ingress| {
-		let (block_data, signature) = para_context.produce_candidate(
+		let (block_data, _, signature) = para_context.produce_candidate(
 			ingress.0.iter().flat_map(|&(id, ref msgs)| msgs.iter().cloned().map(move |msg| (id, msg)))
 		);
 

polkadot/consensus/Cargo.toml

@@ -8,6 +8,9 @@ futures = "0.1.17"
 parking_lot = "0.4"
 tokio-timer = "0.1.2"
 ed25519 = { path = "../../substrate/ed25519" }
+error-chain = "0.11"
+polkadot-api = { path = "../api" }
+polkadot-collator = { path = "../collator" }
 polkadot-primitives = { path = "../primitives" }
 polkadot-statement-table = { path = "../statement-table" }
 substrate-bft = { path = "../../substrate/bft" }

polkadot/consensus/src/error.rs

@@ -0,0 +1,51 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Errors that can occur during the consensus process.
+
+use primitives::block::HeaderHash;
+
+error_chain! {
+	links {
+		PolkadotApi(::polkadot_api::Error, ::polkadot_api::ErrorKind);
+		Bft(::bft::Error, ::bft::ErrorKind);
+	}
+
+	errors {
+		InvalidDutyRosterLength(expected: usize, got: usize) {
+			description("Duty Roster had invalid length"),
+			display("Invalid duty roster length: expected {}, got {}", expected, got),
+		}
+		ProposalNotForPolkadot {
+			description("Proposal provided not a Polkadot block."),
+			display("Proposal provided not a Polkadot block."),
+		}
+		TimestampInFuture {
+			description("Proposal had timestamp too far in the future."),
+			display("Proposal had timestamp too far in the future."),
+		}
+		WrongParentHash(expected: HeaderHash, got: HeaderHash) {
+			description("Proposal had wrong parent hash."),
+			display("Proposal had wrong parent hash. Expected {:?}, got {:?}", expected, got),
+		}
+	}
+}
+
+impl From<::bft::InputStreamConcluded> for Error {
+	fn from(err: ::bft::InputStreamConcluded) -> Self {
+		::bft::Error::from(err).into()
+	}
+}

polkadot/consensus/src/lib.rs

@@ -29,31 +29,73 @@
 //!
 //! Groups themselves may be compromised by malicious authorities.
 
-use std::collections::{HashMap, HashSet};
-use std::sync::Arc;
-
-use codec::Slicable;
-use table::Table;
-use table::generic::Statement as GenericStatement;
-use polkadot_primitives::Hash;
-use polkadot_primitives::parachain::{Id as ParaId, CandidateReceipt};
-use primitives::block::Block as SubstrateBlock;
-use primitives::AuthorityId;
-
-use parking_lot::Mutex;
-
 extern crate futures;
 extern crate ed25519;
 extern crate parking_lot;
 extern crate tokio_timer;
+extern crate polkadot_api;
+extern crate polkadot_collator as collator;
 extern crate polkadot_statement_table as table;
 extern crate polkadot_primitives;
 extern crate substrate_bft as bft;
 extern crate substrate_codec as codec;
 extern crate substrate_primitives as primitives;
 
+#[macro_use]
+extern crate error_chain;
+
+use std::collections::{HashMap, HashSet};
+use std::sync::Arc;
+
+use codec::Slicable;
+use table::{Table, Context as TableContextTrait};
+use table::generic::Statement as GenericStatement;
+use polkadot_api::{PolkadotApi, BlockBuilder};
+use polkadot_primitives::{Hash, Timestamp};
+use polkadot_primitives::block::Block as PolkadotBlock;
+use polkadot_primitives::parachain::{Id as ParaId, DutyRoster, BlockData, Extrinsic, CandidateReceipt};
+use primitives::block::{Block as SubstrateBlock, Header as SubstrateHeader, HeaderHash, Id as BlockId};
+use primitives::AuthorityId;
+
+use futures::prelude::*;
+use futures::future;
+use parking_lot::Mutex;
+
+pub use self::error::{ErrorKind, Error};
+
+mod error;
+
+/// A handle to a statement table router.
+pub trait TableRouter {
+	/// Errors when fetching data from the network.
+	type Error;
+	/// Future that resolves when candidate data is fetched.
+	type FetchCandidate: IntoFuture<Item=BlockData,Error=Self::Error>;
+	/// Future that resolves when extrinsic candidate data is fetched.
+	type FetchExtrinsic: IntoFuture<Item=Extrinsic,Error=Self::Error>;
+
+	/// Note local candidate data.
+	fn local_candidate_data(&self, block_data: BlockData, extrinsic: Extrinsic);
+
+	/// Fetch block data for a specific candidate.
+	fn fetch_block_data(&self, candidate: &CandidateReceipt) -> Self::FetchCandidate;
+
+	/// Fetch extrinsic data for a specific candidate.
+	fn fetch_extrinsic_data(&self, candidate: &CandidateReceipt) -> Self::FetchExtrinsic;
+}
+
+/// A long-lived network which can create statement table routing instances.
+pub trait Network {
+	/// The table router type. This should handle importing of any statements,
+	/// routing statements to peers, and driving completion of any `StatementProducers`.
+	type TableRouter: TableRouter;
+
+	/// Instantiate a table router using the given shared table.
+	fn table_router(&self, table: Arc<SharedTable>) -> Self::TableRouter;
+}
+
 /// Information about a specific group.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct GroupInfo {
 	/// Authorities meant to check validity of candidates.
 	pub validity_guarantors: HashSet<AuthorityId>,
@@ -89,6 +131,10 @@ impl table::Context for TableContext {
 }
 
 impl TableContext {
+	fn local_id(&self) -> AuthorityId {
+		self.key.public().0
+	}
+
 	fn sign_statement(&self, statement: table::Statement) -> table::SignedStatement {
 		let signature = sign_table_statement(&statement, &self.key, &self.parent_hash);
 		let local_id = self.key.public().0;
@@ -124,16 +170,120 @@ pub fn sign_table_statement(statement: &table::Statement, key: &ed25519::Pair, p
 struct SharedTableInner {
 	table: Table<TableContext>,
 	proposed_digest: Option<Hash>,
+	checked_validity: HashSet<Hash>,
+	checked_availability: HashSet<Hash>,
 }
 
 impl SharedTableInner {
-	fn import_statement(
+	// Import a single statement. Provide a handle to a table router.
+	fn import_statement<R: TableRouter>(
 		&mut self,
 		context: &TableContext,
-		statement: ::table::SignedStatement,
+		router: &R,
+		statement: table::SignedStatement,
 		received_from: Option<AuthorityId>,
-	) -> Option<table::Summary> {
-		self.table.import_statement(context, statement, received_from)
+	) -> StatementProducer<<R::FetchCandidate as IntoFuture>::Future, <R::FetchExtrinsic as IntoFuture>::Future> {
+		let mut producer = StatementProducer {
+			fetch_block_data: None,
+			fetch_extrinsic: None,
+			produced_statements: Default::default(),
+			_key: context.key.clone(),
+		};
+
+		let summary = match self.table.import_statement(context, statement, received_from) {
+			Some(summary) => summary,
+			None => return producer,
+		};
+
+		let local_id = context.local_id();
+		let is_validity_member = context.is_member_of(&local_id, &summary.group_id);
+		let is_availability_member =
+			context.is_availability_guarantor_of(&local_id, &summary.group_id);
+
+		let digest = &summary.candidate;
+
+		// TODO: consider a strategy based on the number of candidate votes as well.
+		// only check validity if this wasn't locally proposed.
+		let checking_validity = is_validity_member
+			&& self.proposed_digest.as_ref().map_or(true, |d| d != digest)
+			&& self.checked_validity.insert(digest.clone());
+
+		let checking_availability = is_availability_member && self.checked_availability.insert(digest.clone());
+
+		if checking_validity || checking_availability {
+			match self.table.get_candidate(&digest) {
+				None => {} // TODO: handle table inconsistency somehow?
+				Some(candidate) => {
+					if checking_validity {
+						producer.fetch_block_data = Some(router.fetch_block_data(candidate).into_future().fuse());
+					}
+
+					if checking_availability {
+						producer.fetch_extrinsic = Some(router.fetch_extrinsic_data(candidate).into_future().fuse());
+					}
+				}
+			}
+		}
+
+		producer
+	}
+}
+
+/// Produced statements about a specific candidate.
+/// Both may be `None`.
+#[derive(Default)]
+pub struct ProducedStatements {
+	/// A statement about the validity of the candidate.
+	pub validity: Option<table::Statement>,
+	/// A statement about the availability of the candidate.
+	pub availability: Option<table::Statement>,
+}
+
+/// Future that produces statements about a specific candidate.
+pub struct StatementProducer<D: Future, E: Future> {
+	fetch_block_data: Option<future::Fuse<D>>,
+	fetch_extrinsic: Option<future::Fuse<E>>,
+	produced_statements: ProducedStatements,
+	_key: Arc<ed25519::Pair>,
+}
+
+impl<D, E, Err> Future for StatementProducer<D, E>
+	where
+		D: Future<Item=BlockData,Error=Err>,
+		E: Future<Item=Extrinsic,Error=Err>,
+{
+	type Item = ProducedStatements;
+	type Error = Err;
+
+	fn poll(&mut self) -> Poll<ProducedStatements, Err> {
+		let mut done = true;
+		if let Some(ref mut fetch_block_data) = self.fetch_block_data {
+			match fetch_block_data.poll()? {
+				Async::Ready(_block_data) => {
+					// TODO [PoC-2] : validate block data here and make statement.
+				},
+				Async::NotReady => {
+					done = false;
+				}
+			}
+		}
+
+		if let Some(ref mut fetch_extrinsic) = self.fetch_extrinsic {
+			match fetch_extrinsic.poll()? {
+				Async::Ready(_extrinsic) => {
+					// TODO [PoC-2]: guarantee availability of data and make statment.
+				}
+				Async::NotReady => {
+					done = false;
+				}
+			}
+		}
+
+		if done {
+			Ok(Async::Ready(::std::mem::replace(&mut self.produced_statements, Default::default())))
+		} else {
+			Ok(Async::NotReady)
+		}
 	}
 }
 
@@ -147,7 +297,7 @@ impl Clone for SharedTable {
 	fn clone(&self) -> Self {
 		SharedTable {
 			context: self.context.clone(),
-			inner: self.inner.clone()
+			inner: self.inner.clone(),
 		}
 	}
 }
@@ -163,24 +313,34 @@ impl SharedTable {
 			inner: Arc::new(Mutex::new(SharedTableInner {
 				table: Table::default(),
 				proposed_digest: None,
+				checked_validity: HashSet::new(),
+				checked_availability: HashSet::new(),
 			}))
 		}
 	}
 
-	/// Import a single statement.
-	pub fn import_statement(
+	/// Get group info.
+	pub fn group_info(&self) -> &HashMap<ParaId, GroupInfo> {
+		&self.context.groups
+	}
+
+	/// Import a single statement. Provide a handle to a table router
+	/// for dispatching any other requests which come up.
+	pub fn import_statement<R: TableRouter>(
 		&self,
+		router: &R,
 		statement: table::SignedStatement,
 		received_from: Option<AuthorityId>,
-	) -> Option<table::Summary> {
-		self.inner.lock().import_statement(&*self.context, statement, received_from)
+	) -> StatementProducer<<R::FetchCandidate as IntoFuture>::Future, <R::FetchExtrinsic as IntoFuture>::Future> {
+		self.inner.lock().import_statement(&*self.context, router, statement, received_from)
 	}
 
 	/// Sign and import a local statement.
-	pub fn sign_and_import(
+	pub fn sign_and_import<R: TableRouter>(
 		&self,
+		router: &R,
 		statement: table::Statement,
-	) -> Option<table::Summary> {
+	) -> StatementProducer<<R::FetchCandidate as IntoFuture>::Future, <R::FetchExtrinsic as IntoFuture>::Future> {
 		let proposed_digest = match statement {
 			GenericStatement::Candidate(ref c) => Some(c.hash()),
 			_ => None,
@@ -193,21 +353,25 @@ impl SharedTable {
 			inner.proposed_digest = proposed_digest;
 		}
 
-		inner.import_statement(&*self.context, signed_statement, None)
+		inner.import_statement(&*self.context, router, signed_statement, None)
 	}
 
 	/// Import many statements at once.
 	///
 	/// Provide an iterator yielding pairs of (statement, received_from).
-	pub fn import_statements<I, U>(&self, iterable: I) -> U
+	pub fn import_statements<R, I, U>(&self, router: &R, iterable: I) -> U
 		where
+			R: TableRouter,
 			I: IntoIterator<Item=(table::SignedStatement, Option<AuthorityId>)>,
-			U: ::std::iter::FromIterator<table::Summary>,
+			U: ::std::iter::FromIterator<StatementProducer<
+				<R::FetchCandidate as IntoFuture>::Future,
+				<R::FetchExtrinsic as IntoFuture>::Future>
+			>,
 	{
 		let mut inner = self.inner.lock();
 
-		iterable.into_iter().filter_map(move |(statement, received_from)| {
-			inner.import_statement(&*self.context, statement, received_from)
+		iterable.into_iter().map(move |(statement, received_from)| {
+			inner.import_statement(&*self.context, router, statement, received_from)
 		}).collect()
 	}
 
@@ -241,3 +405,152 @@ impl SharedTable {
 		self.inner.lock().proposed_digest.clone()
 	}
 }
+
+fn make_group_info(roster: DutyRoster, authorities: &[AuthorityId]) -> Result<HashMap<ParaId, GroupInfo>, Error> {
+	if roster.validator_duty.len() != authorities.len() {
+		bail!(ErrorKind::InvalidDutyRosterLength(authorities.len(), roster.validator_duty.len()))
+	}
+
+	if roster.guarantor_duty.len() != authorities.len() {
+		bail!(ErrorKind::InvalidDutyRosterLength(authorities.len(), roster.guarantor_duty.len()))
+	}
+
+	let mut map = HashMap::new();
+
+	let duty_iter = authorities.iter().zip(&roster.validator_duty).zip(&roster.guarantor_duty);
+	for ((authority, v_duty), a_duty) in duty_iter {
+		use polkadot_primitives::parachain::Chain;
+
+		match *v_duty {
+			Chain::Relay => {}, // does nothing for now.
+			Chain::Parachain(ref id) => {
+				map.entry(id.clone()).or_insert_with(GroupInfo::default)
+					.validity_guarantors
+					.insert(authority.clone());
+			}
+		}
+
+		match *a_duty {
+			Chain::Relay => {}, // does nothing for now.
+			Chain::Parachain(ref id) => {
+				map.entry(id.clone()).or_insert_with(GroupInfo::default)
+					.availability_guarantors
+					.insert(authority.clone());
+			}
+		}
+	}
+
+	for live_group in map.values_mut() {
+		let validity_len = live_group.validity_guarantors.len();
+		let availability_len = live_group.availability_guarantors.len();
+
+		live_group.needed_validity = validity_len / 2 + validity_len % 2;
+		live_group.needed_availability = availability_len / 2 + availability_len % 2;
+	}
+
+	Ok(map)
+}
+
+/// Polkadot proposer factory.
+pub struct ProposerFactory<C, N> {
+	/// The client instance.
+	pub client: Arc<C>,
+	/// The backing network handle.
+	pub network: N,
+}
+
+impl<C: PolkadotApi, N: Network> bft::ProposerFactory for ProposerFactory<C, N> {
+	type Proposer = Proposer<C, N::TableRouter>;
+	type Error = Error;
+
+	fn init(&self, parent_header: &SubstrateHeader, authorities: &[AuthorityId], sign_with: Arc<ed25519::Pair>) -> Result<Self::Proposer, Error> {
+		let parent_hash = parent_header.hash();
+		let duty_roster = self.client.duty_roster(&BlockId::Hash(parent_hash))?;
+
+		let group_info = make_group_info(duty_roster, authorities)?;
+		let table = Arc::new(SharedTable::new(group_info, sign_with, parent_hash));
+		let router = self.network.table_router(table.clone());
+
+		// TODO [PoC-2]: kick off collation process.
+		Ok(Proposer {
+			parent_hash,
+			_table: table,
+			_router: router,
+			client: self.client.clone(),
+		})
+	}
+}
+
+fn current_timestamp() -> Timestamp {
+	use std::time;
+
+	time::SystemTime::now().duration_since(time::UNIX_EPOCH)
+		.expect("now always later than unix epoch; qed")
+		.as_secs()
+}
+
+/// The Polkadot proposer logic.
+pub struct Proposer<C, R> {
+	parent_hash: HeaderHash,
+	client: Arc<C>,
+	_table: Arc<SharedTable>,
+	_router: R,
+}
+
+impl<C: PolkadotApi, R: TableRouter> bft::Proposer for Proposer<C, R> {
+	type Error = Error;
+	type Create = Result<SubstrateBlock, Error>;
+	type Evaluate = Result<bool, Error>;
+
+	fn propose(&self) -> Result<SubstrateBlock, Error> {
+		// TODO: handle case when current timestamp behind that in state.
+		let polkadot_block = self.client.build_block(
+			&BlockId::Hash(self.parent_hash),
+			current_timestamp()
+		)?.bake();
+
+		// TODO: integrate transaction queue and `push_transaction`s.
+
+		let substrate_block = Slicable::decode(&mut polkadot_block.encode().as_slice())
+			.expect("polkadot blocks defined to serialize to substrate blocks correctly; qed");
+
+		Ok(substrate_block)
+	}
+
+	// TODO: certain kinds of errors here should lead to a misbehavior report.
+	fn evaluate(&self, proposal: &SubstrateBlock) -> Result<bool, Error> {
+		evaluate_proposal(proposal, &*self.client, current_timestamp(), &self.parent_hash)
+	}
+}
+
+fn evaluate_proposal<C: PolkadotApi>(
+	proposal: &SubstrateBlock,
+	client: &C,
+	now: Timestamp,
+	parent_hash: &HeaderHash,
+) -> Result<bool, Error> {
+	const MAX_TIMESTAMP_DRIFT: Timestamp = 4;
+
+	let encoded = Slicable::encode(proposal);
+	let proposal = PolkadotBlock::decode(&mut &encoded[..])
+		.ok_or_else(|| ErrorKind::ProposalNotForPolkadot)?;
+
+	if proposal.header.parent_hash != *parent_hash {
+		bail!(ErrorKind::WrongParentHash(*parent_hash, proposal.header.parent_hash));
+	}
+
+	// no need to check number because
+	// a) we assume the parent is valid.
+	// b) the runtime checks that `proposal.parent_hash` == `block_hash(proposal.number - 1)`
+
+	let block_timestamp = proposal.body.timestamp;
+
+	// TODO: just defer using `tokio_timer` to delay prepare vote.
+	if block_timestamp > now + MAX_TIMESTAMP_DRIFT {
+		bail!(ErrorKind::TimestampInFuture)
+	}
+
+	// execute the block.
+	client.evaluate_block(&BlockId::Hash(*parent_hash), proposal)?;
+	Ok(true)
+}

polkadot/executor/src/lib.rs

@@ -44,8 +44,10 @@ mod tests {
 	use polkadot_runtime::runtime::staking::balance;
 	use state_machine::{CodeExecutor, TestExternalities};
 	use primitives::twox_128;
-	use polkadot_primitives::{Hash, Header, BlockNumber, Block, Digest, Transaction,
-		UncheckedTransaction, Function};
+	use polkadot_primitives::{
+		Hash, Header, Body, BlockNumber, Block, Digest, Transaction,
+		UncheckedTransaction, Function, InherentFunction,
+	};
 	use ed25519::{Public, Pair};
 
 	const BLOATY_CODE: &[u8] = include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm");
@@ -58,76 +60,6 @@ mod tests {
 		)
 	}
 
-	fn tx() -> UncheckedTransaction {
-		let transaction = Transaction {
-			signed: Keyring::One.to_raw_public(),
-			nonce: 0,
-			function: Function::StakingTransfer(Keyring::Two.to_raw_public(), 69),
-		};
-		let signature = Keyring::from_raw_public(transaction.signed).unwrap()
-			.sign(&transaction.encode());
-
-		UncheckedTransaction { transaction, signature }
-	}
-
-	#[test]
-	fn panic_execution_with_foreign_code_gives_error() {
-		let one = Keyring::One.to_raw_public();
-		let mut t: TestExternalities = map![
-			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![68u8, 0, 0, 0, 0, 0, 0, 0]
-		];
-
-		let r = Executor::new().call(&mut t, BLOATY_CODE, "execute_transaction", &vec![].and(&Header::from_block_number(1u64)).and(&tx()));
-		assert!(r.is_err());
-	}
-
-	#[test]
-	fn panic_execution_with_native_equivalent_code_gives_error() {
-		let one = Keyring::One.to_raw_public();
-		let mut t: TestExternalities = map![
-			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![68u8, 0, 0, 0, 0, 0, 0, 0]
-		];
-
-		let r = Executor::new().call(&mut t, COMPACT_CODE, "execute_transaction", &vec![].and(&Header::from_block_number(1u64)).and(&tx()));
-		assert!(r.is_err());
-	}
-
-	#[test]
-	fn successful_execution_with_native_equivalent_code_gives_ok() {
-		let one = Keyring::One.to_raw_public();
-		let two = Keyring::Two.to_raw_public();
-
-		let mut t: TestExternalities = map![
-			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![111u8, 0, 0, 0, 0, 0, 0, 0]
-		];
-
-		let r = Executor::new().call(&mut t, COMPACT_CODE, "execute_transaction", &vec![].and(&Header::from_block_number(1u64)).and(&tx()));
-		assert!(r.is_ok());
-
-		runtime_io::with_externalities(&mut t, || {
-			assert_eq!(balance(&one), 42);
-			assert_eq!(balance(&two), 69);
-		});
-	}
-
-	#[test]
-	fn successful_execution_with_foreign_code_gives_ok() {
-		let one = Keyring::One.to_raw_public();
-		let two = Keyring::Two.to_raw_public();
-
-		let mut t: TestExternalities = map![
-			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![111u8, 0, 0, 0, 0, 0, 0, 0]
-		];
-
-		let r = Executor::new().call(&mut t, BLOATY_CODE, "execute_transaction", &vec![].and(&Header::from_block_number(1u64)).and(&tx()));
-		assert!(r.is_ok());
-
-		runtime_io::with_externalities(&mut t, || {
-			assert_eq!(balance(&one), 42);
-			assert_eq!(balance(&two), 69);
-		});
-	}
-
 	fn new_test_ext() -> TestExternalities {
 		let one = Keyring::One.to_raw_public();
 		let two = Keyring::Two.to_raw_public();
@@ -152,40 +84,77 @@ mod tests {
 		]
 	}
 
-	fn construct_block(number: BlockNumber, parent_hash: Hash, state_root: Hash, txs: Vec<Transaction>) -> (Vec<u8>, Hash) {
+	fn set_timestamp(timestamp: u64) -> UncheckedTransaction {
+		UncheckedTransaction::inherent(InherentFunction::TimestampSet(timestamp))
+	}
+
+	fn tx() -> UncheckedTransaction {
+		let transaction = Transaction {
+			signed: Keyring::One.to_raw_public(),
+			nonce: 0,
+			function: Function::StakingTransfer(Keyring::Two.to_raw_public(), 69),
+		};
+		let signature = Keyring::from_raw_public(transaction.signed).unwrap()
+			.sign(&transaction.encode());
+
+		UncheckedTransaction { transaction, signature }
+	}
+
+	fn execute_tx_on<C>(executor: C, ext: &mut TestExternalities, code: &[u8], tx: UncheckedTransaction, header: Header)
+		-> Result<Vec<u8>, C::Error>
+		where C: CodeExecutor
+	{
+		let next_header = executor.call(ext, code, "execute_transaction", &vec![].and(&header).and(&set_timestamp(100_000))).unwrap();
+		let next_input = next_header.and(&tx);
+
+		executor.call(ext, code, "execute_transaction", &next_input[..])
+	}
+
+	fn construct_block(number: BlockNumber, parent_hash: Hash, state_root: Hash, timestamp: u64, txs: Vec<Transaction>) -> (Vec<u8>, Hash) {
 		use triehash::ordered_trie_root;
 
+
 		let transactions = txs.into_iter().map(|transaction| {
 			let signature = Pair::from(Keyring::from_public(Public::from_raw(transaction.signed)).unwrap())
 				.sign(&transaction.encode());
 
 			UncheckedTransaction { transaction, signature }
-		}).collect::<Vec<_>>();
-
-		let transaction_root = ordered_trie_root(transactions.iter().map(Slicable::encode)).0.into();
+		}).collect();
 
 		let header = Header {
 			parent_hash,
 			number,
 			state_root,
-			transaction_root,
+			transaction_root: Default::default(),
 			digest: Digest { logs: vec![], },
 		};
-		let hash = header.blake2_256();
 
-		(Block { header, transactions }.encode(), hash.into())
+		let mut block = Block {
+			header,
+			body: Body { timestamp, transactions },
+		};
+
+		let transaction_root = ordered_trie_root(block.all_transactions().map(|tx| Slicable::encode(&tx))).0.into();
+		block.header.transaction_root = transaction_root;
+
+		let hash = block.header.blake2_256();
+
+		(block.encode(), hash.into())
 	}
 
 	fn block1() -> (Vec<u8>, Hash) {
 		construct_block(
 			1,
 			[69u8; 32].into(),
-			hex!("2481853da20b9f4322f34650fea5f240dcbfb266d02db94bfa0153c31f4a29db").into(),
-			vec![Transaction {
-				signed: Keyring::One.to_raw_public(),
-				nonce: 0,
-				function: Function::StakingTransfer(Keyring::Two.to_raw_public(), 69),
-			}]
+			hex!("3df569d47a0d7f4a448486f04fba4eea3e9dfca001319c609f88b3a67b0dd1ea").into(),
+			100_000,
+			vec![
+				Transaction {
+					signed: Keyring::One.to_raw_public(),
+					nonce: 0,
+					function: Function::StakingTransfer(Keyring::Two.to_raw_public(), 69),
+				}
+			]
 		)
 	}
 
@@ -193,7 +162,8 @@ mod tests {
 		construct_block(
 			2,
 			block1().1,
-			hex!("1feb4d3a2e587079e6ce1685fa79994efd995e33cb289d39cded67aac1bb46a9").into(),
+			hex!("c8776c92e8012bf6b3f206448eda3f00bca26d77f220f4714c81cbc92a30e1e2").into(),
+			200_000,
 			vec![
 				Transaction {
 					signed: Keyring::Two.to_raw_public(),
@@ -209,6 +179,64 @@ mod tests {
 		)
 	}
 
+	#[test]
+	fn panic_execution_with_foreign_code_gives_error() {
+		let one = Keyring::One.to_raw_public();
+		let mut t: TestExternalities = map![
+			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![68u8, 0, 0, 0, 0, 0, 0, 0]
+		];
+
+		let r = execute_tx_on(Executor::new(), &mut t, BLOATY_CODE, tx(), Header::from_block_number(1));
+		assert!(r.is_err());
+	}
+
+	#[test]
+	fn panic_execution_with_native_equivalent_code_gives_error() {
+		let one = Keyring::One.to_raw_public();
+		let mut t: TestExternalities = map![
+			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![68u8, 0, 0, 0, 0, 0, 0, 0]
+		];
+
+		let r = execute_tx_on(Executor::new(), &mut t, COMPACT_CODE, tx(), Header::from_block_number(1));
+		assert!(r.is_err());
+	}
+
+	#[test]
+	fn successful_execution_with_native_equivalent_code_gives_ok() {
+		let one = Keyring::One.to_raw_public();
+		let two = Keyring::Two.to_raw_public();
+
+		let mut t: TestExternalities = map![
+			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![111u8, 0, 0, 0, 0, 0, 0, 0]
+		];
+
+		let r = execute_tx_on(Executor::new(), &mut t, COMPACT_CODE, tx(), Header::from_block_number(1));
+		assert!(r.is_ok());
+
+		runtime_io::with_externalities(&mut t, || {
+			assert_eq!(balance(&one), 42);
+			assert_eq!(balance(&two), 69);
+		});
+	}
+
+	#[test]
+	fn successful_execution_with_foreign_code_gives_ok() {
+		let one = Keyring::One.to_raw_public();
+		let two = Keyring::Two.to_raw_public();
+
+		let mut t: TestExternalities = map![
+			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![111u8, 0, 0, 0, 0, 0, 0, 0]
+		];
+
+		let r = execute_tx_on(Executor::new(), &mut t, BLOATY_CODE, tx(), Header::from_block_number(1));
+		assert!(r.is_ok());
+
+		runtime_io::with_externalities(&mut t, || {
+			assert_eq!(balance(&one), 42);
+			assert_eq!(balance(&two), 69);
+		});
+	}
+
 	#[test]
 	fn full_native_block_import_works() {
 		let mut t = new_test_ext();
@@ -255,7 +283,7 @@ mod tests {
 		];
 
 		let foreign_code = include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm");
-		let r = WasmExecutor.call(&mut t, &foreign_code[..], "execute_transaction", &vec![].and(&Header::from_block_number(1u64)).and(&tx()));
+		let r = execute_tx_on(WasmExecutor, &mut t, &foreign_code[..], tx(), Header::from_block_number(1));
 		assert!(r.is_err());
 	}
 
@@ -269,7 +297,7 @@ mod tests {
 		];
 
 		let foreign_code = include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm");
-		let r = WasmExecutor.call(&mut t, &foreign_code[..], "execute_transaction", &vec![].and(&Header::from_block_number(1u64)).and(&tx()));
+		let r = execute_tx_on(WasmExecutor, &mut t, &foreign_code[..], tx(), Header::from_block_number(1));
 		assert!(r.is_ok());
 
 		runtime_io::with_externalities(&mut t, || {

polkadot/primitives/src/block.rs

@@ -21,7 +21,7 @@ use primitives::bytes;
 use primitives::H256;
 use rstd::vec::Vec;
 use codec::{Input, Slicable};
-use transaction::UncheckedTransaction;
+use transaction::{UncheckedTransaction, Function, InherentFunction};
 
 pub use primitives::block::Id;
 
@@ -69,8 +69,65 @@ impl Slicable for Digest {
 	}
 }
 
-/// The block "body": A bunch of transactions.
-pub type Body = Vec<UncheckedTransaction>;
+/// Iterator over all inherent transactions.
+pub struct InherentTransactions<'a> {
+	number: u64,
+	body: &'a Body,
+}
+
+impl<'a> Iterator for InherentTransactions<'a> {
+	type Item = UncheckedTransaction;
+
+	fn next(&mut self) -> Option<UncheckedTransaction> {
+		if self.number == InherentFunction::count() {
+			return None
+		}
+
+		self.number += 1;
+
+		let function = match self.number {
+			1 => Some(InherentFunction::TimestampSet(self.body.timestamp)),
+			_ => None,
+		};
+
+		function.map(UncheckedTransaction::inherent)
+	}
+}
+
+/// Type alias for an iterator over all transactions in a block.
+pub type AllTransactions<'a> = ::rstd::iter::Chain<
+	InherentTransactions<'a>,
+	::rstd::iter::Cloned<::rstd::slice::Iter<'a, UncheckedTransaction>>,
+>;
+
+/// The block body. Contains timestamp and transactions.
+// TODO: add candidates update as well.
+#[derive(PartialEq, Eq, Clone)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+#[cfg_attr(feature = "std", serde(rename_all = "camelCase"))]
+#[cfg_attr(feature = "std", serde(deny_unknown_fields))]
+pub struct Body {
+	/// The timestamp of the block.
+	pub timestamp: u64,
+	/// The transactions in the block.
+	pub transactions: Vec<UncheckedTransaction>,
+}
+
+impl Body {
+	/// Get an iterator over all inherent transactions of the body.
+	pub fn inherent_transactions(&self) -> InherentTransactions {
+		InherentTransactions {
+			number: 0,
+			body: self,
+		}
+	}
+
+	/// Get an iterator over all transactions in a block.
+	pub fn all_transactions(&self) -> AllTransactions {
+		self.inherent_transactions().chain(self.transactions.iter().cloned())
+	}
+}
+
 
 /// A Polkadot relay chain block.
 #[derive(PartialEq, Eq, Clone)]
@@ -78,21 +135,65 @@ pub type Body = Vec<UncheckedTransaction>;
 pub struct Block {
 	/// The block header.
 	pub header: Header,
-	/// All relay-chain transactions.
-	pub transactions: Body,
+	/// The block body.
+	pub body: Body,
+}
+
+impl Block {
+	/// Get an iterator over all inherent transactions of the body.
+	pub fn inherent_transactions(&self) -> InherentTransactions {
+		self.body.inherent_transactions()
+	}
+
+	/// Get an iterator over all transactions in a block.
+	pub fn all_transactions(&self) -> AllTransactions {
+		self.body.all_transactions()
+	}
 }
 
 impl Slicable for Block {
 	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		let (header, transactions) = try_opt!(Slicable::decode(input));
-		Some(Block { header, transactions })
+		let header = try_opt!(Slicable::decode(input));
+
+		let transactions_len: u32 = try_opt!(Slicable::decode(input));
+		let regular_transactions_len = try_opt!(transactions_len.checked_sub(InherentFunction::count() as u32));
+
+		let timestamp_tx = try_opt!(UncheckedTransaction::decode(input));
+		let timestamp = match timestamp_tx.transaction.function {
+			Function::Inherent(InherentFunction::TimestampSet(ref t)) if timestamp_tx.is_well_formed() => { t.clone() }
+			_ => return None,
+		};
+
+		let transactions: Option<Vec<_>> = (0..regular_transactions_len)
+			.map(|_| UncheckedTransaction::decode(input))
+			.filter(|tx| tx.as_ref().map_or(true, |tx| tx.is_well_formed()))
+			.collect();
+
+		let body = Body {
+			timestamp,
+			transactions: try_opt!(transactions),
+		};
+
+		Some(Block { header, body })
 	}
 
 	fn encode(&self) -> Vec<u8> {
 		let mut v = Vec::new();
 
 		v.extend(self.header.encode());
-		v.extend(self.transactions.encode());
+
+		// encode inherent transactions before non-inherent.
+		let transactions_len = self.body.transactions.len() as u64 + InherentFunction::count();
+		(transactions_len as u32).using_encoded(|s| v.extend(s));
+
+		let timestamp_set_tx = UncheckedTransaction::inherent(
+			InherentFunction::TimestampSet(self.body.timestamp)
+		);
+
+		v.extend(timestamp_set_tx.encode());
+		for non_inherent_transaction in &self.body.transactions {
+			v.extend(non_inherent_transaction.encode());
+		}
 
 		v
 	}
@@ -186,4 +287,89 @@ mod tests {
 		let v = header.encode();
 		assert_eq!(Header::decode(&mut &v[..]).unwrap(), header);
 	}
+
+	#[test]
+	fn block_encoding_round_trip() {
+		let mut block = Block {
+			header: Header::from_block_number(1),
+			body: Body {
+				timestamp: 100_000_000,
+				transactions: Vec::new(),
+			}
+		};
+
+		let raw = block.encode();
+		let decoded = Block::decode(&mut &raw[..]).unwrap();
+
+		assert_eq!(block, decoded);
+
+		block.body.transactions.push(UncheckedTransaction {
+			transaction: ::transaction::Transaction {
+				function: Function::StakingStake,
+				signed: Default::default(),
+				nonce: 10101,
+			},
+			signature: Default::default(),
+		});
+
+		let raw = block.encode();
+		let decoded = Block::decode(&mut &raw[..]).unwrap();
+
+		assert_eq!(block, decoded);
+	}
+
+	#[test]
+	fn block_encoding_substrate_round_trip() {
+		let mut block = Block {
+			header: Header::from_block_number(1),
+			body: Body {
+				timestamp: 100_000_000,
+				transactions: Vec::new(),
+			}
+		};
+
+		block.body.transactions.push(UncheckedTransaction {
+			transaction: ::transaction::Transaction {
+				function: Function::StakingStake,
+				signed: Default::default(),
+				nonce: 10101,
+			},
+			signature: Default::default(),
+		});
+
+		let raw = block.encode();
+		let decoded_substrate = ::primitives::block::Block::decode(&mut &raw[..]).unwrap();
+		let encoded_substrate = decoded_substrate.encode();
+		let decoded = Block::decode(&mut &encoded_substrate[..]).unwrap();
+
+		assert_eq!(block, decoded);
+	}
+
+	#[test]
+	fn decode_body_without_inherents_fails() {
+		let substrate_blank = ::primitives::block::Block {
+			header: ::primitives::block::Header::from_block_number(1),
+			transactions: Vec::new(),
+		};
+
+		let encoded_substrate = substrate_blank.encode();
+		assert!(Block::decode(&mut &encoded_substrate[..]).is_none());
+	}
+
+	#[test]
+	fn inherent_transactions_iter_contains_all_inherent() {
+		let block = Block {
+			header: Header::from_block_number(1),
+			body: Body {
+				timestamp: 10101,
+				transactions: Vec::new(),
+			}
+		};
+
+		let mut iter = block.inherent_transactions();
+
+		assert_eq!(InherentFunction::count(), 1); // following depends on this assertion.
+		assert_eq!(iter.next().unwrap(), UncheckedTransaction::inherent(InherentFunction::TimestampSet(10101)));
+		assert!(iter.next().is_none());
+	}
 }

polkadot/primitives/src/lib.rs

@@ -49,9 +49,9 @@ pub mod validator;
 pub mod block;
 pub mod transaction;
 
-pub use self::block::{Header, Block, Log, Digest};
+pub use self::block::{Header, Body, Block, Log, Digest};
 pub use self::block::Number as BlockNumber;
-pub use self::transaction::{Transaction, UncheckedTransaction, Function, Proposal};
+pub use self::transaction::{Transaction, UncheckedTransaction, Function, InherentFunction, Proposal};
 
 /// Virtual account ID that represents the idea of a dispatch/statement being signed by everybody
 /// (who matters). Essentially this means that a majority of validators have decided it is
@@ -75,5 +75,8 @@ pub type TxOrder = u64;
 /// A hash of some data used by the relay chain.
 pub type Hash = primitives::H256;
 
-/// Alias to 520-bit hash when used in the context of a signature on the relay chain.
+/// Alias to 512-bit hash when used in the context of a signature on the relay chain.
 pub type Signature = primitives::hash::H512;
+
+/// A timestamp: seconds since the unix epoch.
+pub type Timestamp = u64;

polkadot/primitives/src/parachain.rs

@@ -121,6 +121,13 @@ impl Slicable for DutyRoster {
 	}
 }
 
+/// Extrinsic data for a parachain.
+#[derive(PartialEq, Eq, Clone)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+#[cfg_attr(feature = "std", serde(rename_all = "camelCase"))]
+#[cfg_attr(feature = "std", serde(deny_unknown_fields))]
+pub struct Extrinsic;
+
 /// Candidate parachain block.
 ///
 /// https://github.com/w3f/polkadot-spec/blob/master/spec.md#candidate-para-chain-block

polkadot/primitives/src/transaction.rs

@@ -18,6 +18,7 @@
 
 use rstd::vec::Vec;
 use codec::{Input, Slicable};
+use ::Signature;
 
 #[cfg(feature = "std")]
 use std::fmt;
@@ -184,12 +185,35 @@ impl FunctionId {
 	}
 }
 
+/// Inherent functions on the runtime.
+/// These must be called each block by the `EVERYBODY` account.
+#[derive(Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+pub enum InherentFunction {
+	/// Set the timestamp.
+	TimestampSet(u64),
+}
+
+impl InherentFunction {
+	/// Get the number of inherent functions.
+	pub fn count() -> u64 {
+		1
+	}
+
+	/// Get the index.
+	pub fn index(&self) -> u64 {
+		match *self {
+			InherentFunction::TimestampSet(_) => 0,
+		}
+	}
+}
+
 /// Functions on the runtime.
 #[derive(Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
 pub enum Function {
-	/// Set the timestamp.
-	TimestampSet(u64),
+	/// An inherent function.
+	Inherent(InherentFunction),
 	/// Set temporary session key as a validator.
 	SessionSetKey(::SessionKey),
 	/// Staking subsystem: begin staking.
@@ -204,12 +228,34 @@ pub enum Function {
 	GovernanceApprove(BlockNumber),
 }
 
+impl Function {
+	/// The number of inherent functions.
+	pub fn inherent_functions() -> u64 { InherentFunction::count() }
+
+	/// Whether this function is "inherent": that it must be part of every
+	/// block at the given index and no other.
+	///
+	/// Transactions containing inherent functions should not be signed.
+	pub fn is_inherent(&self) -> bool {
+		self.inherent_index().is_some()
+	}
+
+	/// If this function is inherent, returns the index it should occupy
+	/// in the block. Otherwise returns `None`.
+	pub fn inherent_index(&self) -> Option<u64> {
+		match *self {
+			Function::Inherent(ref inner) => Some(inner.index()),
+			_ => None,
+		}
+	}
+}
+
 impl Slicable for Function {
 	fn decode<I: Input>(input: &mut I) -> Option<Self> {
 		let id = try_opt!(u8::decode(input).and_then(FunctionId::from_u8));
 		Some(match id {
 			FunctionId::TimestampSet =>
-				Function::TimestampSet(try_opt!(Slicable::decode(input))),
+				Function::Inherent(InherentFunction::TimestampSet(try_opt!(Slicable::decode(input)))),
 			FunctionId::SessionSetKey =>
 				Function::SessionSetKey(try_opt!(Slicable::decode(input))),
 			FunctionId::StakingStake => Function::StakingStake,
@@ -230,7 +276,7 @@ impl Slicable for Function {
 	fn encode(&self) -> Vec<u8> {
 		let mut v = Vec::new();
 		match *self {
-			Function::TimestampSet(ref data) => {
+			Function::Inherent(InherentFunction::TimestampSet(ref data)) => {
 				(FunctionId::TimestampSet as u8).using_encoded(|s| v.extend(s));
 				data.using_encoded(|s| v.extend(s));
 			}
@@ -308,7 +354,33 @@ pub struct UncheckedTransaction {
 	/// The actual transaction information.
 	pub transaction: Transaction,
 	/// The signature; should be an Ed25519 signature applied to the serialised `transaction` field.
-	pub signature: super::Signature,
+	pub signature: Signature,
+}
+
+impl UncheckedTransaction {
+	/// Whether the transaction is well-formed. In particular checks that
+	/// inherent transactions have the correct signed and signature fields.
+	///
+	/// Does not check signatures on other transactions.
+	pub fn is_well_formed(&self) -> bool {
+		if self.transaction.function.is_inherent() {
+			self.transaction.signed == ::EVERYBODY && self.signature == Signature::zero()
+		} else {
+			true
+		}
+	}
+
+	/// Create a new inherent-style transaction from the given function.
+	pub fn inherent(function: InherentFunction) -> Self {
+		UncheckedTransaction {
+			transaction: Transaction {
+				function: Function::Inherent(function),
+				nonce: 0,
+				signed: ::EVERYBODY
+			},
+			signature: Signature::zero(),
+		}
+	}
 }
 
 impl Slicable for UncheckedTransaction {
@@ -372,7 +444,7 @@ mod tests {
 			transaction: Transaction {
 				signed: [1; 32],
 				nonce: 999u64,
-				function: Function::TimestampSet(135135),
+				function: Function::Inherent(InherentFunction::TimestampSet(135135)),
 			},
 			signature: primitives::hash::H512([0; 64]),
 		};

polkadot/runtime/src/api.rs

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-use runtime::{system, parachains, consensus, session};
+use runtime::{system, parachains, consensus, session, timestamp};
 
 impl_stubs!(
 	execute_block => |block| system::internal::execute_block(block),
@@ -23,5 +23,6 @@ impl_stubs!(
 	validator_count => |()| session::validator_count(),
 	validators => |()| session::validators(),
 	authorities => |()| consensus::authorities(),
-	duty_roster => |()| parachains::calculate_duty_roster()
+	duty_roster => |()| parachains::calculate_duty_roster(),
+	get_timestamp => |()| timestamp::get()
 );

polkadot/runtime/src/environment.rs

@@ -17,7 +17,6 @@
 //! Environment API: Allows certain information to be accessed throughout the runtime.
 
 use rstd::boxed::Box;
-use rstd::mem;
 use rstd::cell::RefCell;
 use rstd::rc::Rc;
 
@@ -32,6 +31,8 @@ pub struct Environment {
 	pub parent_hash: Hash,
 	/// The current block digest.
 	pub digest: Digest,
+	/// The current transaction index
+	pub transaction_index: u64,
 }
 
 /// Do something with the environment and return its value. Keep the function short.
@@ -52,7 +53,7 @@ fn env() -> Rc<RefCell<Environment>> {
 			let singleton: Rc<RefCell<Environment>> = Rc::new(RefCell::new(Default::default()));
 
 			// Put it in the heap so it can outlive this call
-			SINGLETON = mem::transmute(Box::new(singleton));
+			SINGLETON = Box::into_raw(Box::new(singleton)) as *const _;
 		}
 
 		// Now we give out a copy of the data that is safe to use concurrently.
@@ -73,7 +74,7 @@ fn env() -> Rc<RefCell<Environment>> {
 			let singleton: Rc<RefCell<Environment>> = Rc::new(RefCell::new(Default::default()));
 
 			// Put it in the heap so it can outlive this call
-			*s.borrow_mut() = mem::transmute(Box::new(singleton));
+			*s.borrow_mut() = Box::into_raw(Box::new(singleton)) as *const _;
 		}
 
 		// Now we give out a copy of the data that is safe to use concurrently.

polkadot/runtime/src/lib.rs

@@ -41,7 +41,7 @@ pub mod api;
 pub mod transaction {
 	use rstd::ops;
 	use polkadot_primitives::Signature;
-	pub use polkadot_primitives::{Transaction, UncheckedTransaction};
+	pub use polkadot_primitives::{Transaction, Function, UncheckedTransaction};
 
 	/// A type-safe indicator that a transaction has been checked.
 	#[derive(PartialEq, Eq, Clone)]
@@ -63,10 +63,20 @@ pub mod transaction {
 		}
 	}
 
-	/// Check the signature on a transaction.
-	///
-	/// On failure, return the transaction back.
-	pub fn check(tx: UncheckedTransaction) -> Result<CheckedTransaction, UncheckedTransaction> {
+	/// Check the validity of a transaction: whether it can appear at the given index
+	/// and whether it is correctly authenticated.
+	pub fn check(tx: UncheckedTransaction, index: u64) -> Result<CheckedTransaction, UncheckedTransaction> {
+		match tx.transaction.function.inherent_index() {
+			Some(correct_index) => {
+				if index != correct_index || !tx.is_well_formed() { return Err(tx) }
+				return Ok(CheckedTransaction(tx));
+			}
+			None => {
+				// non-inherent functions must appear after inherent.
+				if index < Function::inherent_functions() { return Err(tx) }
+			}
+		}
+
 		let msg = ::codec::Slicable::encode(&tx.transaction);
 		if ::runtime_io::ed25519_verify(&tx.signature.0, &msg, &tx.transaction.signed) {
 			Ok(CheckedTransaction(tx))

polkadot/runtime/src/runtime/system.rs

@@ -24,12 +24,12 @@ use codec::{KeyedVec, Slicable};
 use runtime_support::{Hashable, storage};
 use environment::with_env;
 use polkadot_primitives::{AccountId, Hash, TxOrder, BlockNumber, Block, Header,
-	UncheckedTransaction, Function, Log};
+	UncheckedTransaction, Function, InherentFunction, Log};
 use runtime::{staking, session};
 
 const NONCE_OF: &[u8] = b"sys:non:";
 const BLOCK_HASH_AT: &[u8] = b"sys:old:";
-const CODE: &[u8] = b"sys:cod";
+const TEMP_TRANSACTION_NUMBER: &[u8] = b"temp:txcount:";
 
 /// The current block number being processed. Set by `execute_block`.
 pub fn block_number() -> BlockNumber {
@@ -71,8 +71,10 @@ pub mod internal {
 		// any initial checks
 		initial_checks(&block);
 
-		// execute transactions
-		block.transactions.iter().cloned().for_each(super::execute_transaction);
+		// execute all transactions, inherent or otherwise.
+		for (tx_num, tx) in block.all_transactions().enumerate() {
+			super::execute_transaction(tx, tx_num as u64);
+		}
 
 		// post-transactional book-keeping.
 		staking::internal::check_new_era();
@@ -87,6 +89,8 @@ pub mod internal {
 
 	/// Execute a transaction outside of the block execution function.
 	/// This doesn't attempt to validate anything regarding the block.
+	/// Note that when building a block transaction by transaction, the
+	/// inherent methods must be called manually.
 	pub fn execute_transaction(utx: UncheckedTransaction, mut header: Header) -> Header {
 		// populate environment from header.
 		with_env(|e| {
@@ -95,11 +99,16 @@ pub mod internal {
 			mem::swap(&mut header.digest, &mut e.digest);
 		});
 
-		super::execute_transaction(utx);
+		let tx_num: u64 = storage::get_or_default(TEMP_TRANSACTION_NUMBER);
+
+		super::execute_transaction(utx, tx_num);
 
 		with_env(|e| {
 			mem::swap(&mut header.digest, &mut e.digest);
 		});
+
+		storage::put(TEMP_TRANSACTION_NUMBER, &(tx_num + 1));
+
 		header
 	}
 
@@ -113,6 +122,11 @@ pub mod internal {
 			mem::swap(&mut header.digest, &mut e.digest);
 		});
 
+		let tx_count: u64 = storage::take_or_default(TEMP_TRANSACTION_NUMBER);
+		if tx_count < Function::inherent_functions() {
+			panic!("Not enough transactions provided to fulfill all inherent functions.");
+		}
+
 		staking::internal::check_new_era();
 		session::internal::check_rotate_session();
 
@@ -125,54 +139,61 @@ pub mod internal {
 
 		header
 	}
+}
 
-	/// Dispatch a function.
-	pub fn dispatch_function(function: &Function, transactor: &AccountId) {
-		match *function {
-			Function::StakingStake => {
-				::runtime::staking::public::stake(transactor);
-			}
-			Function::StakingUnstake => {
-				::runtime::staking::public::unstake(transactor);
-			}
-			Function::StakingTransfer(dest, value) => {
-				::runtime::staking::public::transfer(transactor, &dest, value);
-			}
-			Function::SessionSetKey(session) => {
-				::runtime::session::public::set_key(transactor, &session);
-			}
-			Function::TimestampSet(t) => {
-				::runtime::timestamp::public::set(t);
-			}
-			Function::GovernancePropose(ref proposal) => {
-				::runtime::governance::public::propose(transactor, proposal);
-			}
-			Function::GovernanceApprove(era_index) => {
-				::runtime::governance::public::approve(transactor, era_index);
-			}
+/// Dispatch a function.
+fn dispatch_function(function: &Function, transactor: &AccountId) {
+	match *function {
+		Function::Inherent(InherentFunction::TimestampSet(t)) => {
+			::runtime::timestamp::public::set(t);
+		}
+		Function::StakingStake => {
+			::runtime::staking::public::stake(transactor);
+		}
+		Function::StakingUnstake => {
+			::runtime::staking::public::unstake(transactor);
+		}
+		Function::StakingTransfer(dest, value) => {
+			::runtime::staking::public::transfer(transactor, &dest, value);
+		}
+		Function::SessionSetKey(session) => {
+			::runtime::session::public::set_key(transactor, &session);
+		}
+		Function::GovernancePropose(ref proposal) => {
+			::runtime::governance::public::propose(transactor, proposal);
+		}
+		Function::GovernanceApprove(era_index) => {
+			::runtime::governance::public::approve(transactor, era_index);
 		}
 	}
 }
 
-fn execute_transaction(utx: UncheckedTransaction) {
+fn execute_transaction(utx: UncheckedTransaction, tx_num: u64) {
 	use ::transaction;
 
-	// Verify the signature is good.
-	let tx = match transaction::check(utx) {
+	// Verify the transaction is authenticated at its position.
+	let tx = match transaction::check(utx, tx_num) {
 		Ok(tx) => tx,
-		Err(_) => panic!("All transactions should be properly signed"),
+		Err(_) => panic!("Transaction at index {} not properly authenticated", tx_num),
 	};
 
 	// check nonce
 	let nonce_key = tx.signed.to_keyed_vec(NONCE_OF);
-	let expected_nonce: TxOrder = storage::get_or(&nonce_key, 0);
+	let (expected_nonce, increment_nonce) = if !tx.function.is_inherent() {
+		(storage::get_or(&nonce_key, 0), true)
+	} else {
+		(0, false)
+	};
+
 	assert!(tx.nonce == expected_nonce, "All transactions should have the correct nonce");
 
-	// increment nonce in storage
-	storage::put(&nonce_key, &(expected_nonce + 1));
+	// increment nonce in storage, unless it's the EVERYBODY account.
+	if increment_nonce {
+		storage::put(&nonce_key, &(expected_nonce + 1));
+	}
 
 	// decode parameters and dispatch
-	internal::dispatch_function(&tx.function, &tx.signed);
+	dispatch_function(&tx.function, &tx.signed);
 }
 
 fn initial_checks(block: &Block) {
@@ -185,7 +206,7 @@ fn initial_checks(block: &Block) {
 	);
 
 	// check transaction trie root represents the transactions.
-	let txs = block.transactions.iter().map(Slicable::encode).collect::<Vec<_>>();
+	let txs = block.all_transactions().map(|tx| Slicable::encode(&tx)).collect::<Vec<_>>();
 	let txs = txs.iter().map(Vec::as_slice).collect::<Vec<_>>();
 	let txs_root = enumerated_trie_root(&txs).into();
 	info_expect_equal_hash(&header.transaction_root, &txs_root);
@@ -239,9 +260,37 @@ mod tests {
 	use keyring::Keyring;
 	use environment::with_env;
 	use primitives::hexdisplay::HexDisplay;
-	use polkadot_primitives::{Header, Digest, UncheckedTransaction, Transaction, Function};
+	use polkadot_primitives::{Header, Body, Digest, UncheckedTransaction, Transaction, Function, InherentFunction};
 	use runtime::staking;
 
+	fn set_timestamp() -> UncheckedTransaction {
+		UncheckedTransaction::inherent(InherentFunction::TimestampSet(100_000))
+	}
+
+	#[test]
+	#[should_panic]
+	fn fails_if_first_not_timestamp_set() {
+		let one = Keyring::One.to_raw_public();
+		let two = Keyring::Two.to_raw_public();
+
+		let mut t: TestExternalities = map![
+			twox_128(&one.to_keyed_vec(b"sta:bal:")).to_vec() => vec![111u8, 0, 0, 0, 0, 0, 0, 0]
+		];
+
+		let tx = UncheckedTransaction {
+			transaction: Transaction {
+				signed: one.clone(),
+				nonce: 0,
+				function: Function::StakingTransfer(two, 69),
+			},
+			signature: hex!("5f9832c5a4a39e2dd4a3a0c5b400e9836beb362cb8f7d845a8291a2ae6fe366612e080e4acd0b5a75c3d0b6ee69614a68fb63698c1e76bf1f2dcd8fa617ddf05").into(),
+		};
+
+		with_externalities(&mut t, || {
+			internal::execute_transaction(tx, Header::from_block_number(1));
+		});
+	}
+
 	#[test]
 	fn staking_balance_transfer_dispatch_works() {
 		let one = Keyring::One.to_raw_public();
@@ -261,7 +310,9 @@ mod tests {
 		};
 
 		with_externalities(&mut t, || {
-			internal::execute_transaction(tx, Header::from_block_number(1));
+			let header = Header::from_block_number(1);
+			let header = internal::execute_transaction(set_timestamp(), header);
+			internal::execute_transaction(tx, header);
 			assert_eq!(staking::balance(&one), 42);
 			assert_eq!(staking::balance(&two), 69);
 		});
@@ -293,22 +344,22 @@ mod tests {
 
 	#[test]
 	fn block_import_works() {
-		let one = Keyring::One.to_raw_public();
-		let two = Keyring::Two.to_raw_public();
-
 		let mut t = new_test_ext();
 
 		let h = Header {
 			parent_hash: [69u8; 32].into(),
 			number: 1,
-			state_root: hex!("1ab2dbb7d4868a670b181327b0b6a58dc64b10cfb9876f737a5aa014b8da31e0").into(),
-			transaction_root: hex!("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421").into(),
+			state_root: hex!("aa4fbcdc09b21e4366aebccd9b9ec0831a8a2765c712d3397f121ff8e60e21e2").into(),
+			transaction_root: hex!("328ae80be3adf358d2a2e188cbe1bfd3f8cd5b15a2e7666e2b4eccf7450efc32").into(),
 			digest: Digest { logs: vec![], },
 		};
 
 		let b = Block {
 			header: h,
-			transactions: vec![],
+			body: Body {
+				timestamp: 100_000,
+				transactions: vec![]
+			}
 		};
 
 		with_externalities(&mut t, || {
@@ -334,7 +385,10 @@ mod tests {
 
 		let b = Block {
 			header: h,
-			transactions: vec![],
+			body: Body {
+				timestamp: 100_000,
+				transactions: vec![],
+			}
 		};
 
 		with_externalities(&mut t, || {
@@ -360,7 +414,10 @@ mod tests {
 
 		let b = Block {
 			header: h,
-			transactions: vec![],
+			body: Body {
+				timestamp: 100_000,
+				transactions: vec![],
+			}
 		};
 
 		with_externalities(&mut t, || {

polkadot/runtime/src/runtime/timestamp.rs

@@ -17,8 +17,7 @@
 //! Timestamp manager: just handles the current timestamp.
 
 use runtime_support::storage;
-
-pub type Timestamp = u64;
+use polkadot_primitives::Timestamp;
 
 const CURRENT_TIMESTAMP: &[u8] = b"tim:val";
 
@@ -32,6 +31,10 @@ pub mod public {
 
 	/// Set the current time.
 	pub fn set(now: Timestamp) {
+		if super::get() > now {
+			panic!("last timestamp less than now");
+		}
+
 		storage::put(CURRENT_TIMESTAMP, &now);
 	}
 }