core: Add vote filter (#430)

* core: ignore usless vote

* core: export SkipBlockHash and NullBlockHash

* core: add VoteFilter

* Add test

* New VoteFilter for each round

2 files changed, 153 insertions, 0 deletions

diff --git a/core/utils/vote-filter.go b/core/utils/vote-filter.go
new file mode 100644
index 0000000..a199027
--- /dev/null
+++ b/core/utils/vote-filter.go
@@ -0,0 +1,61 @@
+// Copyright 2019 The dexon-consensus Authors
+// This file is part of the dexon-consensus library.
+//
+// The dexon-consensus library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus library 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 Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package utils
+
+import (
+	"github.com/dexon-foundation/dexon-consensus/core/types"
+)
+
+// VoteFilter filters votes that are useless for now.
+// To maximize performance, this structure is not thread-safe and will never be.
+type VoteFilter struct {
+	Height   uint64
+	LockIter uint64
+	Period   uint64
+	Confirm  bool
+}
+
+// NewVoteFilter creates a new vote filter instance.
+func NewVoteFilter() *VoteFilter {
+	return &VoteFilter{}
+}
+
+// Filter checks if the vote should be filtered out.
+func (vf *VoteFilter) Filter(vote *types.Vote) bool {
+	if vote.Type == types.VoteInit {
+		return true
+	}
+	if vote.Position.Height < vf.Height {
+		return true
+	} else if vote.Position.Height > vf.Height {
+		// It's impossible to check the vote of other height.
+		return false
+	}
+	if vf.Confirm {
+		return true
+	}
+	if vote.Type == types.VotePreCom && vote.Period < vf.LockIter {
+		return true
+	}
+	if vote.Type == types.VoteCom &&
+		vote.Period < vf.Period &&
+		vote.BlockHash == types.SkipBlockHash {
+		return true
+	}
+	return false
+}
diff --git a/core/utils/vote-filter_test.go b/core/utils/vote-filter_test.go
new file mode 100644
index 0000000..88050e1
--- /dev/null
+++ b/core/utils/vote-filter_test.go
@@ -0,0 +1,92 @@
+// Copyright 2019 The dexon-consensus Authors
+// This file is part of the dexon-consensus library.
+//
+// The dexon-consensus library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus library 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 Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package utils
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+
+	"github.com/dexon-foundation/dexon-consensus/common"
+	"github.com/dexon-foundation/dexon-consensus/core/types"
+)
+
+type VoteFilterTestSuite struct {
+	suite.Suite
+}
+
+func (s *VoteFilterTestSuite) TestFilterVotePass() {
+	filter := NewVoteFilter()
+	filter.Height = uint64(6)
+	filter.Period = uint64(3)
+	filter.LockIter = uint64(3)
+	// Pass with higher Height.
+	vote := types.NewVote(types.VotePreCom, common.NewRandomHash(), uint64(1))
+	vote.Position.Height = filter.Height + 1
+	s.Require().False(filter.Filter(vote))
+	// Pass with VotePreCom.
+	vote = types.NewVote(types.VotePreCom, common.NewRandomHash(),
+		filter.LockIter)
+	vote.Position.Height = filter.Height
+	s.Require().False(filter.Filter(vote))
+	// Pass with VoteCom.
+	vote = types.NewVote(types.VoteCom, common.NewRandomHash(),
+		filter.Period)
+	vote.Position.Height = filter.Height
+	s.Require().False(filter.Filter(vote))
+	vote.Period--
+	s.Require().False(filter.Filter(vote))
+}
+
+func (s *VoteFilterTestSuite) TestFilterVoteInit() {
+	filter := NewVoteFilter()
+	vote := types.NewVote(types.VoteInit, common.NewRandomHash(), uint64(1))
+	s.True(filter.Filter(vote))
+}
+
+func (s *VoteFilterTestSuite) TestFilterVotePreCom() {
+	filter := NewVoteFilter()
+	filter.LockIter = uint64(3)
+	vote := types.NewVote(types.VotePreCom, common.NewRandomHash(), uint64(1))
+	s.True(filter.Filter(vote))
+}
+
+func (s *VoteFilterTestSuite) TestFilterVoteCom() {
+	filter := NewVoteFilter()
+	filter.Period = uint64(3)
+	vote := types.NewVote(types.VoteCom, types.SkipBlockHash, uint64(1))
+	s.True(filter.Filter(vote))
+}
+
+func (s *VoteFilterTestSuite) TestFilterConfirm() {
+	filter := NewVoteFilter()
+	filter.Confirm = true
+	vote := types.NewVote(types.VoteCom, common.NewRandomHash(), uint64(1))
+	s.True(filter.Filter(vote))
+}
+func (s *VoteFilterTestSuite) TestFilterLowerHeight() {
+	filter := NewVoteFilter()
+	filter.Height = uint64(10)
+	vote := types.NewVote(types.VoteCom, common.NewRandomHash(), uint64(1))
+	vote.Position.Height = filter.Height - 1
+	s.True(filter.Filter(vote))
+}
+
+func TestVoteFilter(t *testing.T) {
+	suite.Run(t, new(VoteFilterTestSuite))
+}