native: implement delegated voting

Close #867.

config/protocol.unit_testnet.yml

@@ -7,6 +7,7 @@ ProtocolConfiguration:
     - 02103a7f7dd016558597f7960d27c516a4394fd968b9e65155eb4b013e4040406e
     - 03d90c07df63e690ce77912e10ab51acc944b66860237b608c4f8f8309e71ee699
     - 02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62
+  ValidatorsCount: 4
   SeedList:
     - 127.0.0.1:20334
     - 127.0.0.1:20335

pkg/config/protocol_config.go

@@ -14,6 +14,7 @@ type (
 		SecondsPerBlock   int      `yaml:"SecondsPerBlock"`
 		SeedList          []string `yaml:"SeedList"`
 		StandbyValidators []string `yaml:"StandbyValidators"`
+		ValidatorsCount   int      `yaml:"ValidatorsCount"`
 		// Whether to verify received blocks.
 		VerifyBlocks bool `yaml:"VerifyBlocks"`
 		// Whether to verify transactions in received blocks.

pkg/core/native/native_neo.go

@@ -44,12 +44,14 @@ const (
 	NEOTotalSupply = 100000000
 	// prefixCandidate is a prefix used to store validator's data.
 	prefixCandidate = 33
+	// prefixVotersCount is a prefix for storing total amount of NEO of voters.
+	prefixVotersCount = 1
+	// effectiveVoterTurnout represents minimal ratio of total supply to total amount voted value
+	// which is require to use non-standby validators.
+	effectiveVoterTurnout = 5
 )
 
 var (
-	// validatorsCountKey is a key used to store validators count
-	// used to determine the real number of validators.
-	validatorsCountKey = []byte{15}
 	// nextValidatorsKey is a key used to store validators for the
 	// next block.
 	nextValidatorsKey = []byte{14}
@@ -96,7 +98,7 @@ func NewNEO() *NEO {
 
 	desc = newDescriptor("vote", smartcontract.BoolType,
 		manifest.NewParameter("account", smartcontract.Hash160Type),
-		manifest.NewParameter("pubkeys", smartcontract.ArrayType))
+		manifest.NewParameter("pubkey", smartcontract.PublicKeyType))
 	md = newMethodAndPrice(n.vote, 500000000, smartcontract.AllowModifyStates)
 	n.AddMethod(md, desc, false)
 
@@ -104,6 +106,10 @@ func NewNEO() *NEO {
 	md = newMethodAndPrice(n.getCandidatesCall, 100000000, smartcontract.AllowStates)
 	n.AddMethod(md, desc, true)
 
+	desc = newDescriptor("getСommittee", smartcontract.ArrayType)
+	md = newMethodAndPrice(n.getCommittee, 100000000, smartcontract.AllowStates)
+	n.AddMethod(md, desc, true)
+
 	desc = newDescriptor("getValidators", smartcontract.ArrayType)
 	md = newMethodAndPrice(n.getValidators, 100000000, smartcontract.AllowStates)
 	n.AddMethod(md, desc, true)
@@ -131,6 +137,11 @@ func (n *NEO) Initialize(ic *interop.Context) error {
 	}
 	n.mint(ic, h, big.NewInt(NEOTotalSupply))
 
+	err = ic.DAO.PutStorageItem(n.ContractID, []byte{prefixVotersCount}, &state.StorageItem{Value: []byte{0}})
+	if err != nil {
+		return err
+	}
+
 	for i := range vs {
 		if err := n.registerCandidateInternal(ic, vs[i]); err != nil {
 			return err
@@ -166,21 +177,11 @@ func (n *NEO) increaseBalance(ic *interop.Context, h util.Uint160, si *state.Sto
 		si.Value = acc.Bytes()
 		return nil
 	}
-	if len(acc.Votes) > 0 {
-		if err := n.ModifyAccountVotes(acc, ic.DAO, amount); err != nil {
-			return err
-		}
-		siVC := ic.DAO.GetStorageItem(n.ContractID, validatorsCountKey)
-		if siVC == nil {
-			return errors.New("validators count uninitialized")
-		}
-		vc, err := ValidatorsCountFromBytes(siVC.Value)
-		if err != nil {
-			return err
-		}
-		vc[len(acc.Votes)-1].Add(&vc[len(acc.Votes)-1], amount)
-		siVC.Value = vc.Bytes()
-		if err := ic.DAO.PutStorageItem(n.ContractID, validatorsCountKey, siVC); err != nil {
+	if err := n.ModifyAccountVotes(acc, ic.DAO, amount, modifyVoteTransfer); err != nil {
+		return err
+	}
+	if acc.VoteTo != nil {
+		if err := n.modifyVoterTurnout(ic.DAO, amount); err != nil {
 			return err
 		}
 	}
@@ -224,35 +225,26 @@ func (n *NEO) registerCandidate(ic *interop.Context, args []stackitem.Item) stac
 func (n *NEO) registerCandidateInternal(ic *interop.Context, pub *keys.PublicKey) error {
 	key := makeValidatorKey(pub)
 	si := ic.DAO.GetStorageItem(n.ContractID, key)
-	if si != nil {
-		return errors.New("already registered")
+	if si == nil {
+		si = new(state.StorageItem)
 	}
-	si = new(state.StorageItem)
-	// Zero value.
-	si.Value = []byte{}
+	c := &candidate{Registered: true}
+	si.Value = c.Bytes()
 	return ic.DAO.PutStorageItem(n.ContractID, key, si)
 }
 
 func (n *NEO) vote(ic *interop.Context, args []stackitem.Item) stackitem.Item {
 	acc := toUint160(args[0])
-	arr := args[1].Value().([]stackitem.Item)
-	var pubs keys.PublicKeys
-	for i := range arr {
-		pub := new(keys.PublicKey)
-		bs, err := arr[i].TryBytes()
-		if err != nil {
-			panic(err)
-		} else if err := pub.DecodeBytes(bs); err != nil {
-			panic(err)
-		}
-		pubs = append(pubs, pub)
+	var pub *keys.PublicKey
+	if _, ok := args[1].(stackitem.Null); !ok {
+		pub = toPublicKey(args[1])
 	}
-	err := n.VoteInternal(ic, acc, pubs)
+	err := n.VoteInternal(ic, acc, pub)
 	return stackitem.NewBool(err == nil)
 }
 
 // VoteInternal votes from account h for validarors specified in pubs.
-func (n *NEO) VoteInternal(ic *interop.Context, h util.Uint160, pubs keys.PublicKeys) error {
+func (n *NEO) VoteInternal(ic *interop.Context, h util.Uint160, pub *keys.PublicKey) error {
 	ok, err := runtime.CheckHashedWitness(ic, h)
 	if err != nil {
 		return err
@@ -268,69 +260,57 @@ func (n *NEO) VoteInternal(ic *interop.Context, h util.Uint160, pubs keys.Public
 	if err != nil {
 		return err
 	}
-	if err := n.ModifyAccountVotes(acc, ic.DAO, new(big.Int).Neg(&acc.Balance)); err != nil {
-		return err
-	}
-	pubs = pubs.Unique()
-	// Check validators registration.
-	var newPubs keys.PublicKeys
-	for _, pub := range pubs {
-		if ic.DAO.GetStorageItem(n.ContractID, makeValidatorKey(pub)) == nil {
-			continue
+	if (acc.VoteTo == nil) != (pub == nil) {
+		val := &acc.Balance
+		if pub == nil {
+			val = new(big.Int).Neg(val)
 		}
-		newPubs = append(newPubs, pub)
-	}
-	if lp, lv := len(newPubs), len(acc.Votes); lp != lv {
-		var si *state.StorageItem
-		var vc *ValidatorsCount
-		var err error
-
-		si = ic.DAO.GetStorageItem(n.ContractID, validatorsCountKey)
-		if si == nil {
-			// The first voter.
-			si = new(state.StorageItem)
-			vc = new(ValidatorsCount)
-		} else {
-			vc, err = ValidatorsCountFromBytes(si.Value)
-			if err != nil {
-				return err
-			}
-		}
-		if lv > 0 {
-			vc[lv-1].Sub(&vc[lv-1], &acc.Balance)
-		}
-		if len(newPubs) > 0 {
-			vc[lp-1].Add(&vc[lp-1], &acc.Balance)
-		}
-		si.Value = vc.Bytes()
-		if err := ic.DAO.PutStorageItem(n.ContractID, validatorsCountKey, si); err != nil {
+		if err := n.modifyVoterTurnout(ic.DAO, val); err != nil {
 			return err
 		}
 	}
-	acc.Votes = newPubs
-	if err := n.ModifyAccountVotes(acc, ic.DAO, &acc.Balance); err != nil {
+	if err := n.ModifyAccountVotes(acc, ic.DAO, new(big.Int).Neg(&acc.Balance), modifyVoteOld); err != nil {
+		return err
+	}
+	acc.VoteTo = pub
+	if err := n.ModifyAccountVotes(acc, ic.DAO, &acc.Balance, modifyVoteNew); err != nil {
 		return err
 	}
 	si.Value = acc.Bytes()
 	return ic.DAO.PutStorageItem(n.ContractID, key, si)
 }
 
+const (
+	modifyVoteTransfer = iota
+	modifyVoteOld
+	modifyVoteNew
+)
+
 // ModifyAccountVotes modifies votes of the specified account by value (can be negative).
-func (n *NEO) ModifyAccountVotes(acc *state.NEOBalanceState, d dao.DAO, value *big.Int) error {
-	for _, vote := range acc.Votes {
-		key := makeValidatorKey(vote)
+// typ specifies if this modify is occuring during transfer or vote (with old or new validator).
+func (n *NEO) ModifyAccountVotes(acc *state.NEOBalanceState, d dao.DAO, value *big.Int, typ int) error {
+	if acc.VoteTo != nil {
+		key := makeValidatorKey(acc.VoteTo)
 		si := d.GetStorageItem(n.ContractID, key)
 		if si == nil {
 			return errors.New("invalid validator")
 		}
-		votes := bigint.FromBytes(si.Value)
-		votes.Add(votes, value)
-		si.Value = bigint.ToPreallocatedBytes(votes, si.Value[:0])
-		if err := d.PutStorageItem(n.ContractID, key, si); err != nil {
-			return err
+		cd := new(candidate).FromBytes(si.Value)
+		cd.Votes.Add(&cd.Votes, value)
+		switch typ {
+		case modifyVoteOld:
+			if !cd.Registered && cd.Votes.Sign() == 0 {
+				return d.DeleteStorageItem(n.ContractID, key)
+			}
+		case modifyVoteNew:
+			if !cd.Registered {
+				return errors.New("validator must be registered")
+			}
 		}
+		n.validators.Store(keys.PublicKeys(nil))
+		si.Value = cd.Bytes()
+		return d.PutStorageItem(n.ContractID, key, si)
 	}
-	n.validators.Store(keys.PublicKeys(nil))
 	return nil
 }
 
@@ -341,8 +321,10 @@ func (n *NEO) getCandidates(d dao.DAO) ([]keyWithVotes, error) {
 	}
 	arr := make([]keyWithVotes, 0, len(siMap))
 	for key, si := range siMap {
-		votes := bigint.FromBytes(si.Value)
-		arr = append(arr, keyWithVotes{key, votes})
+		c := new(candidate).FromBytes(si.Value)
+		if c.Registered {
+			arr = append(arr, keyWithVotes{key, &c.Votes})
+		}
 	}
 	sort.Slice(arr, func(i, j int) bool { return strings.Compare(arr[i].Key, arr[j].Key) == -1 })
 	return arr, nil
@@ -386,53 +368,15 @@ func (n *NEO) GetValidatorsInternal(bc blockchainer.Blockchainer, d dao.DAO) (ke
 	if vals := n.validators.Load().(keys.PublicKeys); vals != nil {
 		return vals.Copy(), nil
 	}
-	standByValidators := bc.GetStandByValidators()
-	si := d.GetStorageItem(n.ContractID, validatorsCountKey)
-	if si == nil {
-		n.validators.Store(standByValidators)
-		return standByValidators.Copy(), nil
-	}
-	validatorsCount, err := ValidatorsCountFromBytes(si.Value)
+	result, err := n.getCommitteeMembers(bc, d)
 	if err != nil {
 		return nil, err
 	}
-	validators, err := n.GetCandidates(d)
-	if err != nil {
-		return nil, err
+	count := bc.GetConfig().ValidatorsCount
+	if len(result) < count {
+		count = len(result)
 	}
-	sort.Slice(validators, func(i, j int) bool {
-		// The most-voted validators should end up in the front of the list.
-		cmp := validators[i].Votes.Cmp(validators[j].Votes)
-		if cmp != 0 {
-			return cmp > 0
-		}
-		// Ties are broken with public keys.
-		return validators[i].Key.Cmp(validators[j].Key) == -1
-	})
-
-	count := validatorsCount.GetWeightedAverage()
-	if count < len(standByValidators) {
-		count = len(standByValidators)
-	}
-
-	uniqueSBValidators := standByValidators.Unique()
-	result := keys.PublicKeys{}
-	for _, validator := range validators {
-		if validator.Votes.Sign() > 0 || uniqueSBValidators.Contains(validator.Key) {
-			result = append(result, validator.Key)
-		}
-	}
-
-	if result.Len() >= count {
-		result = result[:count]
-	} else {
-		for i := 0; i < uniqueSBValidators.Len() && result.Len() < count; i++ {
-			if !result.Contains(uniqueSBValidators[i]) {
-				result = append(result, uniqueSBValidators[i])
-			}
-		}
-	}
-	sort.Sort(result)
+	result = result[:count]
 	n.validators.Store(result)
 	return result, nil
 }
@@ -445,6 +389,68 @@ func (n *NEO) getValidators(ic *interop.Context, _ []stackitem.Item) stackitem.I
 	return pubsToArray(result)
 }
 
+func (n *NEO) getCommittee(ic *interop.Context, _ []stackitem.Item) stackitem.Item {
+	pubs, err := n.getCommitteeMembers(ic.Chain, ic.DAO)
+	if err != nil {
+		panic(err)
+	}
+	sort.Sort(pubs)
+	return pubsToArray(pubs)
+}
+
+func (n *NEO) modifyVoterTurnout(d dao.DAO, amount *big.Int) error {
+	key := []byte{prefixVotersCount}
+	si := d.GetStorageItem(n.ContractID, key)
+	if si == nil {
+		return errors.New("voters count not found")
+	}
+	votersCount := bigint.FromBytes(si.Value)
+	votersCount.Add(votersCount, amount)
+	si.Value = bigint.ToBytes(votersCount)
+	return d.PutStorageItem(n.ContractID, key, si)
+}
+
+func (n *NEO) getCommitteeMembers(bc blockchainer.Blockchainer, d dao.DAO) (keys.PublicKeys, error) {
+	key := []byte{prefixVotersCount}
+	si := d.GetStorageItem(n.ContractID, key)
+	if si == nil {
+		return nil, errors.New("voters count not found")
+	}
+	votersCount := bigint.FromBytes(si.Value)
+	// votersCount / totalSupply must be >= 0.2
+	votersCount.Mul(votersCount, big.NewInt(effectiveVoterTurnout))
+	voterTurnout := votersCount.Div(votersCount, n.getTotalSupply(d))
+	if voterTurnout.Sign() != 1 {
+		return bc.GetStandByValidators(), nil
+	}
+	cs, err := n.getCandidates(d)
+	if err != nil {
+		return nil, err
+	}
+	sbVals := bc.GetStandByValidators()
+	count := len(sbVals)
+	if len(cs) < count {
+		return sbVals, nil
+	}
+	sort.Slice(cs, func(i, j int) bool {
+		// The most-voted validators should end up in the front of the list.
+		cmp := cs[i].Votes.Cmp(cs[j].Votes)
+		if cmp != 0 {
+			return cmp > 0
+		}
+		// Ties are broken with public keys.
+		return strings.Compare(cs[i].Key, cs[j].Key) == -1
+	})
+	pubs := make(keys.PublicKeys, count)
+	for i := range pubs {
+		pubs[i], err = keys.NewPublicKeyFromBytes([]byte(cs[i].Key), elliptic.P256())
+		if err != nil {
+			return nil, err
+		}
+	}
+	return pubs, nil
+}
+
 func (n *NEO) getNextBlockValidators(ic *interop.Context, _ []stackitem.Item) stackitem.Item {
 	result, err := n.getNextBlockValidatorsInternal(ic.Chain, ic.DAO)
 	if err != nil {

pkg/core/native/native_neo_candidate.go

@@ -0,0 +1,48 @@
+package native
+
+import (
+	"math/big"
+
+	"github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
+)
+
+type candidate struct {
+	Registered bool
+	Votes      big.Int
+}
+
+// Bytes marshals c to byte array.
+func (c *candidate) Bytes() []byte {
+	w := io.NewBufBinWriter()
+	stackitem.EncodeBinaryStackItem(c.toStackItem(), w.BinWriter)
+	return w.Bytes()
+}
+
+// FromBytes unmarshals candidate from byte array.
+func (c *candidate) FromBytes(data []byte) *candidate {
+	r := io.NewBinReaderFromBuf(data)
+	item := stackitem.DecodeBinaryStackItem(r)
+	if r.Err != nil {
+		panic(r.Err)
+	}
+	return c.fromStackItem(item)
+}
+
+func (c *candidate) toStackItem() stackitem.Item {
+	return stackitem.NewStruct([]stackitem.Item{
+		stackitem.NewBool(c.Registered),
+		stackitem.NewBigInteger(&c.Votes),
+	})
+}
+
+func (c *candidate) fromStackItem(item stackitem.Item) *candidate {
+	arr := item.(*stackitem.Struct).Value().([]stackitem.Item)
+	vs, err := arr[1].TryInteger()
+	if err != nil {
+		panic(err)
+	}
+	c.Registered = arr[0].Bool()
+	c.Votes = *vs
+	return c
+}

pkg/core/native/native_neo_test.go

@@ -0,0 +1,18 @@
+package native
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCandidate_Bytes(t *testing.T) {
+	expected := &candidate{
+		Registered: true,
+		Votes:      *big.NewInt(0x0F),
+	}
+	data := expected.Bytes()
+	actual := new(candidate).FromBytes(data)
+	require.Equal(t, expected, actual)
+}

pkg/core/native/validators_count.go

@@ -63,51 +63,3 @@ func (vc *ValidatorsCount) DecodeBinary(r *io.BinReader) {
 		vc[i] = *bigint.FromBytes(buf)
 	}
 }
-
-// GetWeightedAverage returns an average count of validators that's been voted
-// for not counting 1/4 of minimum and maximum numbers.
-func (vc *ValidatorsCount) GetWeightedAverage() int {
-	const (
-		lowerThreshold = 0.25
-		upperThreshold = 0.75
-	)
-	var (
-		sumWeight, sumValue, overallSum, slidingSum int64
-		slidingRatio                                float64
-	)
-
-	for i := range vc {
-		overallSum += vc[i].Int64()
-	}
-
-	for i := range vc {
-		if slidingRatio >= upperThreshold {
-			break
-		}
-		weight := vc[i].Int64()
-		slidingSum += weight
-		previousRatio := slidingRatio
-		slidingRatio = float64(slidingSum) / float64(overallSum)
-
-		if slidingRatio <= lowerThreshold {
-			continue
-		}
-
-		if previousRatio < lowerThreshold {
-			if slidingRatio > upperThreshold {
-				weight = int64((upperThreshold - lowerThreshold) * float64(overallSum))
-			} else {
-				weight = int64((slidingRatio - lowerThreshold) * float64(overallSum))
-			}
-		} else if slidingRatio > upperThreshold {
-			weight = int64((upperThreshold - previousRatio) * float64(overallSum))
-		}
-		sumWeight += weight
-		// Votes with N values get stored with N-1 index, thus +1 here.
-		sumValue += (int64(i) + 1) * weight
-	}
-	if sumValue == 0 || sumWeight == 0 {
-		return 0
-	}
-	return int(sumValue / sumWeight)
-}

pkg/core/state/native_state.go

@@ -1,6 +1,7 @@
 package state
 
 import (
+	"crypto/elliptic"
 	"math/big"
 
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
@@ -17,7 +18,7 @@ type NEP5BalanceState struct {
 type NEOBalanceState struct {
 	NEP5BalanceState
 	BalanceHeight uint32
-	Votes         keys.PublicKeys
+	VoteTo        *keys.PublicKey
 }
 
 // NEP5BalanceStateFromBytes converts serialized NEP5BalanceState to structure.
@@ -110,7 +111,11 @@ func (s *NEOBalanceState) DecodeBinary(r *io.BinReader) {
 func (s *NEOBalanceState) toStackItem() stackitem.Item {
 	result := s.NEP5BalanceState.toStackItem().(*stackitem.Struct)
 	result.Append(stackitem.NewBigInteger(big.NewInt(int64(s.BalanceHeight))))
-	result.Append(stackitem.NewByteArray(s.Votes.Bytes()))
+	if s.VoteTo != nil {
+		result.Append(stackitem.NewByteArray(s.VoteTo.Bytes()))
+	} else {
+		result.Append(stackitem.Null{})
+	}
 	return result
 }
 
@@ -118,6 +123,18 @@ func (s *NEOBalanceState) fromStackItem(item stackitem.Item) error {
 	structItem := item.Value().([]stackitem.Item)
 	s.Balance = *structItem[0].Value().(*big.Int)
 	s.BalanceHeight = uint32(structItem[1].Value().(*big.Int).Int64())
-	s.Votes = make(keys.PublicKeys, 0)
-	return s.Votes.DecodeBytes(structItem[2].Value().([]byte))
+	if _, ok := structItem[2].(stackitem.Null); ok {
+		s.VoteTo = nil
+		return nil
+	}
+	bs, err := structItem[2].TryBytes()
+	if err != nil {
+		return err
+	}
+	pub, err := keys.NewPublicKeyFromBytes(bs, elliptic.P256())
+	if err != nil {
+		return err
+	}
+	s.VoteTo = pub
+	return nil
 }

pkg/rpc/server/server_test.go

@@ -1125,7 +1125,6 @@ func checkNep5Transfers(t *testing.T, e *executor, acc interface{}) {
 				TxHash:    b.Hash(),
 			})
 		}
-
 	}
 	require.Equal(t, expected.Address, res.Address)
 	require.ElementsMatch(t, expected.Sent, res.Sent)