From 2f5aeda44fb9d2b92cb41e3a668d834819366246 Mon Sep 17 00:00:00 2001
From: keorn <pczaban@gmail.com>
Date: Mon, 22 Aug 2016 13:19:23 +0200
Subject: [PATCH] reusable voting on hashes

---
 ethcore/src/engines/mod.rs         |   4 +-
 ethcore/src/engines/signed_vote.rs | 101 +++++++++++++++++++++++++++++
 ethcore/src/error.rs               |  12 ++++
 3 files changed, 116 insertions(+), 1 deletion(-)
 create mode 100644 ethcore/src/engines/signed_vote.rs

diff --git a/ethcore/src/engines/mod.rs b/ethcore/src/engines/mod.rs
index e52db90fb..47a12435d 100644
--- a/ethcore/src/engines/mod.rs
+++ b/ethcore/src/engines/mod.rs
@@ -20,13 +20,15 @@ mod null_engine;
 mod instant_seal;
 mod basic_authority;
 mod bft;
+mod signed_vote;
 
 pub use self::null_engine::NullEngine;
 pub use self::instant_seal::InstantSeal;
 pub use self::basic_authority::BasicAuthority;
 pub use self::bft::BFT;
+pub use self::signed_vote::VoteError;
 
-use common::*;
+use common::{HashMap, SemanticVersion, Header, EnvInfo, Address, Builtin, BTreeMap, U256, Bytes, SignedTransaction, Error};
 use account_provider::AccountProvider;
 use block::ExecutedBlock;
 use spec::CommonParams;
diff --git a/ethcore/src/engines/signed_vote.rs b/ethcore/src/engines/signed_vote.rs
new file mode 100644
index 000000000..694b7cc9b
--- /dev/null
+++ b/ethcore/src/engines/signed_vote.rs
@@ -0,0 +1,101 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity 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.
+
+// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Voting on hashes, where each vote has to come from a set of public keys.
+
+use common::*;
+use account_provider::AccountProvider;
+use block::*;
+use spec::CommonParams;
+use engines::Engine;
+use evm::Schedule;
+use ethjson;
+
+/// Signed voting on hashes.
+#[derive(Debug)]
+pub struct SignedVote {
+	/// Voter public keys.
+	pub voters: HashSet<Address>,
+	/// Number of voters.
+	pub voter_n: usize,
+	/// Threshold vote number for success.
+	pub threshold: usize,
+	/// Votes.
+	votes: RwLock<HashMap<H256, HashSet<Signature>>>,
+	/// Winner hash, set after enough votes are reached.
+	winner: RwLock<Option<H256>>
+}
+
+#[derive(Debug)]
+pub enum VoteError {
+	UnauthorisedVoter
+}
+
+impl SignedVote {
+	/// Create a new instance of BFT engine
+	pub fn new(voters: HashSet<Address>, threshold: usize) -> Self {
+		SignedVote {
+			voter_n: voters.len(),
+			voters: voters,
+			threshold: threshold,
+			votes: RwLock::new(HashMap::new()),
+			winner: RwLock::new(None)
+		}
+	}
+
+	pub fn vote(&self, bare_hash: H256, signature: &Signature) -> bool {
+		if !self.can_vote(&bare_hash, signature).is_ok() { return false; }
+		let n = if let Some(mut old) = self.votes.write().get_mut(&bare_hash) {
+			old.insert(signature.clone());
+			old.len()
+		} else {
+			let mut new = HashSet::new();
+			new.insert(signature.clone());
+			assert!(self.votes.write().insert(bare_hash.clone(), new).is_none());
+			1
+		};
+		if self.is_won(n) {
+			let mut guard = self.winner.write();
+			*guard = Some(bare_hash);
+		}
+		true
+	}
+
+	fn can_vote(&self, bare_hash: &H256, signature: &Signature) -> Result<(), Error> {
+		let signer = Address::from(try!(ec::recover(&signature, bare_hash)).sha3());
+		match self.voters.contains(&signer) {
+			false => try!(Err(VoteError::UnauthorisedVoter)),
+			true => Ok(()),
+		}
+	}
+
+	fn is_won(&self, valid_votes: usize) -> bool {
+		valid_votes > self.threshold
+	}
+
+	pub fn winner(&self) -> Option<H256> { self.winner.read().clone() }
+}
+
+#[cfg(test)]	
+mod tests {
+	use common::{HashSet, Address};
+	use engines::signed_vote::SignedVote;
+	#[test]
+	fn simple_vote() {
+		let voters: HashSet<_> = vec![Address::default()].into_iter().collect();
+		let vote = SignedVote::new(voters, 2);
+	}
+}
diff --git a/ethcore/src/error.rs b/ethcore/src/error.rs
index 449303732..aed7773ae 100644
--- a/ethcore/src/error.rs
+++ b/ethcore/src/error.rs
@@ -24,6 +24,7 @@ use client::Error as ClientError;
 use ipc::binary::{BinaryConvertError, BinaryConvertable};
 use types::block_import_error::BlockImportError;
 use snapshot::Error as SnapshotError;
+use engines::VoteError;
 
 pub use types::executed::{ExecutionError, CallError};
 
@@ -238,6 +239,8 @@ pub enum Error {
 	Snappy(::util::snappy::InvalidInput),
 	/// Snapshot error.
 	Snapshot(SnapshotError),
+	/// Consensus vote error.
+	Vote(VoteError),
 }
 
 impl fmt::Display for Error {
@@ -258,6 +261,7 @@ impl fmt::Display for Error {
 			Error::StdIo(ref err) => err.fmt(f),
 			Error::Snappy(ref err) => err.fmt(f),
 			Error::Snapshot(ref err) => err.fmt(f),
+			Error::Vote(ref err) => f.write_str("Bad vote."),
 		}
 	}
 }
@@ -361,6 +365,14 @@ impl From<SnapshotError> for Error {
 	}
 }
 
+impl From<VoteError> for Error {
+	fn from(err: VoteError) -> Error {
+		match err {
+			other => Error::Vote(other),
+		}
+	}
+}
+
 impl<E> From<Box<E>> for Error where Error: From<E> {
 	fn from(err: Box<E>) -> Error {
 		Error::from(*err)