Networking and in-memory client (#38)

* Networking crate draft

* Started work on syncing algo

* Fixed query range

* BlockCollection tests

* In-mem client backend

* Fixed tests

* Renamed Transaction

* Removed stray println

* Docs

substrate/client/src/blockchain.rs

@@ -0,0 +1,86 @@
+// 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/>.
+
+//! Polkadot blockchain trait
+
+use std::fmt::{Display, Formatter, Error as FmtError};
+use primitives::block;
+use error::Result;
+
+/// Block indentification.
+#[derive(Debug, Clone, Copy)]
+pub enum BlockId {
+	/// Identify by block header hash.
+	Hash(block::HeaderHash),
+	/// Identify by block number.
+	Number(block::Number),
+}
+
+impl Display for BlockId {
+	fn fmt(&self, f: &mut Formatter) -> ::std::result::Result<(), FmtError> {
+		match *self {
+			BlockId::Hash(h) => h.fmt(f),
+			BlockId::Number(n) => n.fmt(f),
+		}
+	}
+}
+
+/// Blockchain database backend. Does not perform any validation.
+pub trait Backend: Send + Sync {
+	/// Get block header. Returns `None` if block is not found.
+	fn header(&self, id: BlockId) -> Result<Option<block::Header>>;
+	/// Get block body. Returns `None` if block is not found.
+	fn body(&self, id: BlockId) -> Result<Option<block::Body>>;
+	/// Get blockchain info.
+	fn info(&self) -> Result<Info>;
+	/// Get block status.
+	fn status(&self, id: BlockId) -> Result<BlockStatus>;
+	/// Get block hash by number. Returns `None` if the header is not in the chain.
+	fn hash(&self, number: block::Number) -> Result<Option<block::HeaderHash>>;
+}
+
+/// Block import outcome
+pub enum ImportResult<E> {
+	/// Imported successfully.
+	Imported,
+	/// Block already exists, skippped.
+	AlreadyInChain,
+	/// Unknown parent.
+	UnknownParent,
+	/// Other errror.
+	Err(E),
+}
+
+/// Blockchain info
+#[derive(Debug)]
+pub struct Info {
+	/// Best block hash.
+	pub best_hash: block::HeaderHash,
+	/// Best block number.
+	pub best_number: block::Number,
+	/// Genesis block hash.
+	pub genesis_hash: block::HeaderHash,
+}
+
+/// Block status.
+#[derive(Debug, PartialEq, Eq)]
+pub enum BlockStatus {
+	/// Already in the blockchain.
+	InChain,
+	/// Not in the queue or the blockchain.
+	Unknown,
+}
+