feat(StakeManager): optimizations on processAccount

.gas-snapshot

@@ -1,9 +1,9 @@
 CreateVaultTest:testDeployment() (gas: 9774)
 CreateVaultTest:test_createVault() (gas: 692936)
 ExecuteAccountTest:testDeployment() (gas: 28720)
-ExecuteAccountTest:test_ExecuteAccountMintMP() (gas: 3856635)
+ExecuteAccountTest:test_ExecuteAccountMintMP() (gas: 3860579)
 ExecuteAccountTest:test_RevertWhen_InvalidLimitEpoch() (gas: 1154886)
-ExecuteAccountTest:test_ShouldNotMintMoreThanCap() (gas: 110522900)
+ExecuteAccountTest:test_ShouldNotMintMoreThanCap() (gas: 110612896)
 ExecuteEpochTest:testDeployment() (gas: 28720)
 ExecuteEpochTest:testNewDeployment() (gas: 30815)
 ExecuteEpochTest:test_ExecuteEpochShouldIncreaseEpoch() (gas: 94810)
@@ -14,17 +14,17 @@ LeaveTest:testDeployment() (gas: 28720)
 LeaveTest:test_RevertWhen_NoPendingMigration() (gas: 1154760)
 LeaveTest:test_RevertWhen_SenderIsNotVault() (gas: 10750)
 LockTest:testDeployment() (gas: 28720)
-LockTest:test_NewLockupPeriod() (gas: 1143587)
-LockTest:test_RevertWhen_InvalidNewLockupPeriod() (gas: 1135204)
-LockTest:test_RevertWhen_InvalidUpdateLockupPeriod() (gas: 1231813)
+LockTest:test_NewLockupPeriod() (gas: 1143392)
+LockTest:test_RevertWhen_InvalidNewLockupPeriod() (gas: 1135009)
+LockTest:test_RevertWhen_InvalidUpdateLockupPeriod() (gas: 1230470)
 LockTest:test_RevertWhen_SenderIsNotVault() (gas: 10630)
-LockTest:test_ShouldIncreaseBonusMP() (gas: 1123687)
-LockTest:test_UpdateLockupPeriod() (gas: 1281200)
+LockTest:test_ShouldIncreaseBonusMP() (gas: 1123492)
+LockTest:test_UpdateLockupPeriod() (gas: 1260809)
 MigrateTest:testDeployment() (gas: 28720)
 MigrateTest:test_RevertWhen_NoPendingMigration() (gas: 1152399)
 MigrateTest:test_RevertWhen_SenderIsNotVault() (gas: 10750)
 MigrationInitializeTest:testDeployment() (gas: 28720)
-MigrationInitializeTest:test_RevertWhen_MigrationPending() (gas: 5716968)
+MigrationInitializeTest:test_RevertWhen_MigrationPending() (gas: 5745821)
 MigrationStakeManagerTest:testDeployment() (gas: 28720)
 MigrationStakeManagerTest:testNewDeployment() (gas: 30859)
 MigrationStakeManagerTest:test_ExecuteEpochShouldNotIncreaseEpochInMigration() (gas: 105686)
@@ -39,17 +39,17 @@ StakeTest:test_RevertWhen_RestakeWithLock() (gas: 1160132)
 StakeTest:test_RevertWhen_SenderIsNotVault() (gas: 10651)
 StakeTest:test_RevertWhen_StakeIsTooLow() (gas: 745253)
 StakeTest:test_RevertWhen_StakeTokenTransferFails() (gas: 175040)
-StakeTest:test_StakeWithoutLockUpTimeMintsMultiplierPoints() (gas: 1029215)
+StakeTest:test_StakeWithoutLockUpTimeMintsMultiplierPoints() (gas: 1029020)
 StakedTokenTest:testStakeToken() (gas: 7616)
 UnstakeTest:testDeployment() (gas: 28742)
 UnstakeTest:test_RevertWhen_AmountMoreThanBalance() (gas: 1133014)
 UnstakeTest:test_RevertWhen_FundsLocked() (gas: 1158758)
 UnstakeTest:test_RevertWhen_SenderIsNotVault() (gas: 10653)
-UnstakeTest:test_UnstakeShouldBurnMultiplierPoints() (gas: 5497531)
-UnstakeTest:test_UnstakeShouldReturnFund_NoLockUp() (gas: 1026695)
-UnstakeTest:test_UnstakeShouldReturnFund_WithLockUp() (gas: 1115820)
+UnstakeTest:test_UnstakeShouldBurnMultiplierPoints() (gas: 5535740)
+UnstakeTest:test_UnstakeShouldReturnFund_NoLockUp() (gas: 1026500)
+UnstakeTest:test_UnstakeShouldReturnFund_WithLockUp() (gas: 1114672)
 UserFlowsTest:testDeployment() (gas: 28720)
-UserFlowsTest:test_PendingMPToBeMintedCannotBeGreaterThanTotalSupplyMP(uint8) (runs: 1001, μ: 69673434, ~: 32945058)
-UserFlowsTest:test_StakeWithLockUpTimeLocksStake() (gas: 1116708)
-UserFlowsTest:test_StakedSupplyShouldIncreaseAndDecreaseAgain() (gas: 1951147)
+UserFlowsTest:test_PendingMPToBeMintedCannotBeGreaterThanTotalSupplyMP(uint8) (runs: 1001, μ: 68072901, ~: 30146840)
+UserFlowsTest:test_StakeWithLockUpTimeLocksStake() (gas: 1115560)
+UserFlowsTest:test_StakedSupplyShouldIncreaseAndDecreaseAgain() (gas: 1950757)
 VaultFactoryTest:testDeployment() (gas: 9774)

contracts/StakeManager.sol

@@ -449,15 +449,18 @@ contract StakeManager is Ownable {
             userReward += userEpochReward;
             iEpoch.epochReward -= userEpochReward;
             iEpoch.totalSupply -= userSupply;
-            //TODO: remove epoch when iEpoch.totalSupply reaches zero
+            if (iEpoch.totalSupply == 0) {
+                pendingReward -= iEpoch.epochReward;
+                delete epochs[userEpoch];
+            }
         }
         account.epoch = userEpoch;
         if (userReward > 0) {
             pendingReward -= userReward;
             stakedToken.transfer(account.rewardAddress, userReward);
         }
-        mpDifference = account.totalMP - mpDifference; //TODO: optimize, this only needed for migration
         if (address(migration) != address(0)) {
+            mpDifference = account.totalMP - mpDifference;
             migration.increaseTotalMP(mpDifference);
         }
     }