From c795ec76423e0704bfe452c16d59989f5cec1bab Mon Sep 17 00:00:00 2001
From: Zarko Milosevic <zarko@tendermint.com>
Date: Thu, 10 Jan 2019 16:30:24 +0100
Subject: [PATCH] Example of more functional proposer API

---
 consensus/state.go     | 10 +++++++---
 state/execution.go     | 16 ++++++++--------
 state/state.go         |  3 ++-
 types/validator_set.go | 33 ++++-----------------------------
 4 files changed, 21 insertions(+), 41 deletions(-)

diff --git a/consensus/state.go b/consensus/state.go
index 81bdce7d..5b2c5cf3 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -743,9 +743,13 @@ func (cs *ConsensusState) enterNewRound(height int64, round int) {
 
 	// Increment validators if necessary
 	validators := cs.Validators
-	if cs.Round < round {
-		validators = validators.Copy()
-		validators.IncrementProposerPriority(round - cs.Round)
+	//if cs.Round < round {
+	//	validators = validators.Copy()
+	//	validators.IncrementProposerPriority(round - cs.Round)
+	//}
+
+	for i := cs.Round; i < round; i++ {
+		validators = validators.UpdateProposerPriority()
 	}
 
 	// Setup new round
diff --git a/state/execution.go b/state/execution.go
index b3d7268e..e3473c54 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -344,11 +344,7 @@ func validateValidatorUpdates(abciUpdates []abci.ValidatorUpdate,
 }
 
 func NextValidators(currentSet *types.ValidatorSet, updates []*types.Validator) (*types.ValidatorSet, error) {
-	nValSet := currentSet.Copy()
-	// update proposer priority. Increase proposer priority for every process for ammount
-	// equal to their voting power and decrease proposer priority of the initial proposer
-	// equal to total voting power
-	nValSet.UpdateProposerPriority()
+	nValSet := currentSet.UpdateProposerPriority()
 
 	// apply updates
 	for _, valUpdate := range updates {
@@ -488,12 +484,13 @@ func updateState(
 
 	// Copy the valset so we can apply changes from EndBlock
 	// and update s.LastValidators and s.Validators.
-	nValSet := state.NextValidators.Copy()
+	nValSet, err := state.NextValidators, error(nil)
 
 	// Update the validator set with the latest abciResponses.
 	lastHeightValsChanged := state.LastHeightValidatorsChanged
 	if len(validatorUpdates) > 0 {
-		err := updateValidators(nValSet, validatorUpdates)
+		//err := updateValidators(nValSet, validatorUpdates)
+		nValSet, err = NextValidators(nValSet, validatorUpdates)
 		if err != nil {
 			return state, fmt.Errorf("Error changing validator set: %v", err)
 		}
@@ -501,8 +498,11 @@ func updateState(
 		lastHeightValsChanged = header.Height + 1 + 1
 	}
 
+	//TODO: Given validator set at height h, when we move to height h+1, should we increment
+	//proposer priority with the voting power they have at height h, or at height h+1?
+
 	// Update validator proposer priority and set state variables.
-	nValSet.IncrementProposerPriority(1)
+	//nValSet.IncrementProposerPriority(1)
 
 	// Update the params with the latest abciResponses.
 	nextParams := state.ConsensusParams
diff --git a/state/state.go b/state/state.go
index b6253b64..fd8320e1 100644
--- a/state/state.go
+++ b/state/state.go
@@ -226,7 +226,8 @@ func MakeGenesisState(genDoc *types.GenesisDoc) (State, error) {
 			validators[i] = types.NewValidator(val.PubKey, val.Power)
 		}
 		validatorSet = types.NewValidatorSet(validators)
-		nextValidatorSet = types.NewValidatorSet(validators).CopyIncrementProposerPriority(1)
+		//nextValidatorSet = types.NewValidatorSet(validators).CopyIncrementProposerPriority(1)
+		nextValidatorSet = validatorSet.UpdateProposerPriority()
 	}
 
 	return State{
diff --git a/types/validator_set.go b/types/validator_set.go
index effb7e07..5c22f94c 100644
--- a/types/validator_set.go
+++ b/types/validator_set.go
@@ -37,8 +37,6 @@ type ValidatorSet struct {
 
 	// cached (unexported)
 	totalVotingPower       int64
-	initProposerPriorities []int64
-	round                  int
 }
 
 // NewValidatorSet initializes a ValidatorSet by copying over the
@@ -58,8 +56,6 @@ func NewValidatorSet(valz []*Validator) *ValidatorSet {
 
 	vals := &ValidatorSet{
 		Validators:             validators,
-		initProposerPriorities: propPriorities,
-		round:                  0,
 	}
 
 	//if len(valz) > 0 {
@@ -81,29 +77,6 @@ func (vals *ValidatorSet) CopyIncrementProposerPriority(times int) *ValidatorSet
 	return copy
 }
 
-// FindProposer computes the proposer of the given round for the validator set.
-// The function for a given validator set and round number always return the same validator
-// as a proposer, i.e., it is purely functional.
-func (vals *ValidatorSet) FindProposer(round int) *Validator {
-	var proposer *Validator
-	if round < vals.round {
-		initialValSet := vals.Copy()
-		initialValSet.round = 0
-		for i, val := range initialValSet.Validators {
-			val.ProposerPriority = initialValSet.initProposerPriorities[i]
-		}
-		for i := initialValSet.round; i <= round; i++ {
-			proposer = vals.UpdateProposerPriority()
-		}
-	} else {
-		for i := vals.round; i <= round; i++ {
-			proposer = vals.UpdateProposerPriority()
-		}
-		vals.round = round
-	}
-	return proposer
-}
-
 // IncrementProposerPriority increments ProposerPriority of each validator and updates the
 // proposer. Panics if validator set is empty.
 // `times` must be positive.
@@ -127,13 +100,15 @@ func (vals *ValidatorSet) IncrementProposerPriority(times int) {
 	vals.Proposer = proposer
 }
 
+// UpdateProposerPriority update proposer priority between rounds. Proposer priority of
+// every proposer is augmented with its voting power; proposer priority of the coordinator is
+// decreased by the total voting power.
 func (vals *ValidatorSet) UpdateProposerPriority() *ValidatorSet {
 	nValSet := vals.Copy()
 
 	// just pick the proposer with the highest proposer priority
 	// without any modification to it
-	proposer := vals.FindProposer(0) // maybe use getProposer here
-
+	proposer := vals.GetProposer()
 	// update proposer priority
 	for _, val := range nValSet.Validators {
 		// Check for overflow for sum.