Add low-level validator/delegator block reward logic

core/state/statedb.go

@@ -23,6 +23,8 @@ import (
 	"math/big"
 	"sort"
 
+	"github.com/harmony-one/harmony/numeric"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
@@ -727,9 +729,39 @@ func (db *DB) IsValidator(addr common.Address) bool {
 	return so.IsValidator(db.db)
 }
 
-func (db *DB) AddReward(validator common.Address, reward *big.Int) {
-	//TODO: implement reward logic
-	// the reward will be distributed to all the delegators based on stake percentage.
+// AddReward distributes the reward to all the delegators based on stake percentage.
+func (db *DB) AddReward(validator common.Address, reward *big.Int) error {
+	rewardPool := big.NewInt(0).Set(reward)
+
+	wrapper := db.GetStakingInfo(validator)
+	if wrapper == nil {
+		return errors.New("failed to distribute rewards: validator does not exist")
+	}
+
+	// Payout commission
+	commissionInt := wrapper.Validator.CommissionRates.Rate.MulInt(reward).RoundInt()
+	wrapper.Delegations[0].Reward.Add(wrapper.Delegations[0].Reward, commissionInt)
+	rewardPool.Sub(rewardPool, commissionInt)
+
+	totalRewardForDelegators := big.NewInt(0).Set(rewardPool)
+
+	// Payout each delegator's reward pro-rata
+	totalDelegationDec := numeric.NewDecFromBigInt(wrapper.TotalDelegation())
+	for i := range wrapper.Delegations {
+		delegation := wrapper.Delegations[i]
+		percentage := numeric.NewDecFromBigInt(delegation.Amount).Quo(totalDelegationDec) // percentage = <this_delegator_amount>/<total_delegation>
+		rewardInt := percentage.MulInt(totalRewardForDelegators).RoundInt()
+
+		delegation.Reward.Add(delegation.Reward, rewardInt)
+		rewardPool.Sub(rewardPool, rewardInt)
+	}
+
+	// The last remaining bit belongs to the validator (remember the validator's self delegation is always at index 0)
+	if rewardPool.Cmp(big.NewInt(0)) > 0 {
+		wrapper.Delegations[0].Reward.Add(wrapper.Delegations[0].Reward, rewardPool)
+	}
+
+	return db.UpdateStakingInfo(validator, wrapper)
 }
 
 func (db *DB) CollectReward(delegator common.Address) {

core/vm/interface.go

@@ -45,7 +45,7 @@ type StateDB interface {
 	SetValidatorFlag(common.Address)
 	UnsetValidatorFlag(common.Address)
 	IsValidator(common.Address) bool
-	AddReward(common.Address, *big.Int)
+	AddReward(common.Address, *big.Int) error
 	CollectReward(common.Address)
 
 	AddRefund(uint64)

numeric/decimal.go

@@ -483,9 +483,9 @@ func (d Dec) RoundInt64() int64 {
 }
 
 // RoundInt round the decimal using bankers rounding
-//func (d Dec) RoundInt() big.Int {
-//	return NewIntFromBigInt(chopPrecisionAndRoundNonMutative(d.Int))
-//}
+func (d Dec) RoundInt() *big.Int {
+	return chopPrecisionAndRoundNonMutative(d.Int)
+}
 
 //___________________________________________________________________________________
 
@@ -509,9 +509,9 @@ func (d Dec) TruncateInt64() int64 {
 }
 
 // TruncateInt truncates the decimals from the number and returns an Int
-//func (d Dec) TruncateInt() big.Int {
-//	return NewIntFromBigInt(chopPrecisionAndTruncateNonMutative(d.Int))
-//}
+func (d Dec) TruncateInt() *big.Int {
+	return chopPrecisionAndTruncateNonMutative(d.Int)
+}
 
 // TruncateDec truncates the decimals from the number and returns a Dec
 func (d Dec) TruncateDec() Dec {

staking/types/delegation.go

@@ -18,6 +18,7 @@ var (
 type Delegation struct {
 	DelegatorAddress common.Address       `json:"delegator_address" yaml:"delegator_address"`
 	Amount           *big.Int             `json:"amount" yaml:"amount"`
+	Reward           *big.Int             `json:"reward" yaml:"reward"`
 	Entries          []*UndelegationEntry `json:"entries" yaml:"entries"`
 }
 

staking/types/validator.go

@@ -68,6 +68,15 @@ func printSlotPubKeys(pubKeys []shard.BlsPublicKey) string {
 	return str
 }
 
+// TotalDelegation - return the total amount of token in delegation
+func (w *ValidatorWrapper) TotalDelegation() *big.Int {
+	total := big.NewInt(0)
+	for _, entry := range w.Delegations {
+		total.Add(total, entry.Amount)
+	}
+	return total
+}
+
 // Description - some possible IRL connections
 type Description struct {
 	Name            string `json:"name" yaml:"name"`                         // name
@@ -157,6 +166,7 @@ func CreateValidatorFromNewMsg(val *CreateValidator) (*Validator, error) {
 	commission := Commission{val.CommissionRates, new(big.Int)}
 	pubKeys := []shard.BlsPublicKey{}
 	pubKeys = append(pubKeys, val.SlotPubKeys...)
+	// TODO: a new validator should have a minimum of 1 token as self delegation, and that should be added as a delegation entry here.
 	v := Validator{val.ValidatorAddress, pubKeys,
 		val.Amount, new(big.Int), val.MinSelfDelegation, val.MaxTotalDelegation, false,
 		commission, desc, big.NewInt(0)}