From 8aed80d428b93bd13143b777ee4227c47dfc95ac Mon Sep 17 00:00:00 2001
From: DinhLN <lenhatdinh@gmail.com>
Date: Fri, 9 Nov 2018 14:34:53 +0700
Subject: [PATCH] Fixed reward inflation and add unit test.

---
 common/constants.go |  1 +
 contracts/utils.go  |  1 +
 eth/backend.go      | 14 ++++++++++++++
 eth/backend_test.go | 24 ++++++++++++++++++++++++
 4 files changed, 40 insertions(+)
 create mode 100644 eth/backend_test.go

diff --git a/common/constants.go b/common/constants.go
index 526325a1ae..2d3bcda972 100644
--- a/common/constants.go
+++ b/common/constants.go
@@ -12,4 +12,5 @@ const (
 	EpocBlockRandomize      = 900
 	MaxMasternodes          = 150
 	LimitPenaltyEpoch       = 4
+	BlocksPerYear           = uint64(15768000)
 )
diff --git a/contracts/utils.go b/contracts/utils.go
index b80a505486..b86f7790a8 100644
--- a/contracts/utils.go
+++ b/contracts/utils.go
@@ -58,6 +58,7 @@ type rewardLog struct {
 }
 
 var TxSignMu sync.RWMutex
+
 // Send tx sign for block number to smart contract blockSigner.
 func CreateTransactionSign(chainConfig *params.ChainConfig, pool *core.TxPool, manager *accounts.Manager, block *types.Block, chainDb ethdb.Database) error {
 	TxSignMu.Lock()
diff --git a/eth/backend.go b/eth/backend.go
index b31015f043..26915e331c 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -291,7 +291,10 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 			if number > 0 && number-rCheckpoint > 0 && foudationWalletAddr != (common.Address{}) {
 				// Get signers in blockSigner smartcontract.
 				addr := common.HexToAddress(common.BlockSigners)
+				// Get reward inflation.
 				chainReward := new(big.Int).Mul(new(big.Int).SetUint64(chain.Config().Posv.Reward), new(big.Int).SetUint64(params.Ether))
+				chainReward = rewardInflation(chainReward, number, common.BlocksPerYear)
+
 				totalSigner := new(uint64)
 				signers, err := contracts.GetRewardForCheckpoint(chain, addr, number, rCheckpoint, client, totalSigner)
 				if err != nil {
@@ -646,3 +649,14 @@ func GetValidators(bc *core.BlockChain, masternodes []common.Address) ([]byte, e
 	}
 	return nil, core.ErrNotFoundM1
 }
+
+func rewardInflation(chainReward *big.Int, number uint64, blockPerYear uint64) *big.Int {
+	if blockPerYear*2 <= number && number < blockPerYear*6 {
+		chainReward.Div(chainReward, new(big.Int).SetUint64(2))
+	}
+	if blockPerYear*6 <= number {
+		chainReward.Div(chainReward, new(big.Int).SetUint64(4))
+	}
+
+	return chainReward
+}
diff --git a/eth/backend_test.go b/eth/backend_test.go
new file mode 100644
index 0000000000..d0c8ea4d3b
--- /dev/null
+++ b/eth/backend_test.go
@@ -0,0 +1,24 @@
+package eth
+
+import (
+	"github.com/ethereum/go-ethereum/params"
+	"math/big"
+	"testing"
+)
+
+func TestRewardInflation(t *testing.T) {
+	for i := 0; i < 100; i++ {
+		chainReward := new(big.Int).Mul(new(big.Int).SetUint64(250), new(big.Int).SetUint64(params.Ether))
+		chainReward = rewardInflation(chainReward, uint64(i), 10)
+
+		halfReward := new(big.Int).Mul(new(big.Int).SetUint64(125), new(big.Int).SetUint64(params.Ether))
+		if 20 <= i && i < 60 && chainReward.Cmp(halfReward) != 0 {
+			t.Error("Fail tor calculate reward inflation for 2 -> 5 years", "chainReward", chainReward)
+		}
+
+		quarterReward := new(big.Int).Mul(new(big.Int).SetUint64(62.5*1000), new(big.Int).SetUint64(params.Finney))
+		if 60 <= i && chainReward.Cmp(quarterReward) != 0 {
+			t.Error("Fail tor calculate reward inflation above 6 years", "chainReward", chainReward)
+		}
+	}
+}