From 4670857c15b22007830770cc4eae8d957f607a59 Mon Sep 17 00:00:00 2001
From: Zarko Milosevic <zarko@tendermint.com>
Date: Tue, 23 Jan 2018 16:54:24 +0100
Subject: [PATCH] Add support for ValidBlock mechanism for the simplest case

---
 consensus/state.go       | 17 +++++++++++++++++
 consensus/types/state.go |  7 +++++++
 2 files changed, 24 insertions(+)

diff --git a/consensus/state.go b/consensus/state.go
index aa334fdd0..8fd177b73 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -477,6 +477,9 @@ func (cs *ConsensusState) updateToState(state sm.State) {
 	cs.LockedRound = 0
 	cs.LockedBlock = nil
 	cs.LockedBlockParts = nil
+	cs.ValidRound = 0
+	cs.ValidBlock = nil
+	cs.ValidBlockParts = nil
 	cs.Votes = cstypes.NewHeightVoteSet(state.ChainID, height, validators)
 	cs.CommitRound = -1
 	cs.LastCommit = lastPrecommits
@@ -798,6 +801,9 @@ func (cs *ConsensusState) defaultDecideProposal(height int64, round int) {
 	if cs.LockedBlock != nil {
 		// If we're locked onto a block, just choose that.
 		block, blockParts = cs.LockedBlock, cs.LockedBlockParts
+	} else if cs.ValidBlock != nil {
+		// If there is valid block, choose that.
+		block, blockParts = cs.ValidBlock, cs.ValidBlockParts
 	} else {
 		// Create a new proposal block from state/txs from the mempool.
 		block, blockParts = cs.createProposalBlock()
@@ -1389,6 +1395,17 @@ func (cs *ConsensusState) addVote(vote *types.Vote, peerID p2p.ID) (added bool,
 						cs.LockedBlockParts = nil
 						cs.eventBus.PublishEventUnlock(cs.RoundStateEvent())
 					}
+					if ok && !blockID.IsZero() && !cs.ValidBlock.HashesTo(blockID.Hash) && vote.Round > cs.ValidRound {
+						// update valid value
+						if cs.ProposalBlock.HashesTo(blockID.Hash) {
+							cs.ValidRound = vote.Round
+							cs.ValidBlock = cs.ProposalBlock
+							cs.ValidBlockParts = cs.ProposalBlockParts
+						}
+						//TODO: We might want to update ValidBlock also in case we don't have that block yet,
+						// and obtain the required block using gossiping
+					}
+
 				}
 				if cs.Round <= vote.Round && prevotes.HasTwoThirdsAny() {
 					// Round-skip over to PrevoteWait or goto Precommit.
diff --git a/consensus/types/state.go b/consensus/types/state.go
index b95131f4e..8e79f10d2 100644
--- a/consensus/types/state.go
+++ b/consensus/types/state.go
@@ -70,6 +70,9 @@ type RoundState struct {
 	LockedRound        int
 	LockedBlock        *types.Block
 	LockedBlockParts   *types.PartSet
+	ValidRound         int
+	ValidBlock         *types.Block
+	ValidBlockParts    *types.PartSet
 	Votes              *HeightVoteSet
 	CommitRound        int            //
 	LastCommit         *types.VoteSet // Last precommits at Height-1
@@ -106,6 +109,8 @@ func (rs *RoundState) StringIndented(indent string) string {
 %s  ProposalBlock: %v %v
 %s  LockedRound:   %v
 %s  LockedBlock:   %v %v
+%s  ValidRound:   %v
+%s  ValidBlock:   %v %v
 %s  Votes:         %v
 %s  LastCommit:    %v
 %s  LastValidators:%v
@@ -118,6 +123,8 @@ func (rs *RoundState) StringIndented(indent string) string {
 		indent, rs.ProposalBlockParts.StringShort(), rs.ProposalBlock.StringShort(),
 		indent, rs.LockedRound,
 		indent, rs.LockedBlockParts.StringShort(), rs.LockedBlock.StringShort(),
+		indent, rs.ValidRound,
+		indent, rs.ValidBlockParts.StringShort(), rs.ValidBlock.StringShort(),
 		indent, rs.Votes.StringIndented(indent+"    "),
 		indent, rs.LastCommit.StringShort(),
 		indent, rs.LastValidators.StringIndented(indent+"    "),