SY.buyBond() returns gain

BondModel is pure, and receives dependancies as params
YieldOracle no longer depends on currentCumulatives()
computations are now based on cToken.exchangeRateCurrent()

contracts/IController.sol

@@ -4,7 +4,7 @@ pragma abicoder v2;
 
 import "./Governed.sol";
 
-contract IController is Governed {
+abstract contract IController is Governed {
 
     address public oracle; // IYieldOracle
 
@@ -99,4 +99,6 @@ contract IController is Governed {
     {
       feesOwner = newVal_;
     }
+
+    function providerRatePerDay() external virtual returns (uint256);
 }

contracts/IProvider.sol

@@ -23,6 +23,6 @@ interface IProvider {
     function transferFees() external;
 
     // current total underlying balance as measured by the provider pool
-    function underlyingBalance() external view returns (uint256);
+    function underlyingBalance() external returns (uint256);
 
 }

contracts/ISmartYield.sol

@@ -36,7 +36,7 @@ interface ISmartYield {
 
     function currentTime() external view returns(uint256);
 
-    function buyBond(uint256 principalAmount_, uint256 minGain_, uint256 deadline_, uint16 forDays_) external;
+    function buyBond(uint256 principalAmount_, uint256 minGain_, uint256 deadline_, uint16 forDays_) external returns (uint256);
 
     function redeemBond(uint256 bondId_) external;
 
@@ -56,7 +56,7 @@ interface ISmartYield {
     /**
      * token purchase price
      */
-    function price() external view returns (uint256);
+    function price() external returns (uint256);
 
     function abondPaid() external view returns (uint256);
 
@@ -67,18 +67,16 @@ interface ISmartYield {
     /**
      * @notice current total underlying balance, without accruing interest
      */
-    function underlyingTotal() external view returns (uint256);
+    function underlyingTotal() external returns (uint256);
 
     /**
      * @notice current underlying loanable, without accruing interest
      */
-    function underlyingLoanable() external view returns (uint256);
+    function underlyingLoanable() external returns (uint256);
 
-    function underlyingJuniors() external view returns (uint256);
+    function underlyingJuniors() external returns (uint256);
 
-    function providerRatePerDay() external view returns (uint256);
+    function bondGain(uint256 principalAmount_, uint16 forDays_) external returns (uint256);
 
-    function bondGain(uint256 principalAmount_, uint16 forDays_) external view returns (uint256);
-
-    function maxBondDailyRate() external view returns (uint256);
+    function maxBondDailyRate() external returns (uint256);
 }

contracts/SmartYield.sol

@@ -193,13 +193,15 @@ contract SmartYield is
     }
 
     // Purchase a senior bond with principalAmount_ underlying for forDays_, buyer gets a bond with gain >= minGain_ or revert. deadline_ is timestamp before which tx is not rejected.
+    // returns gain
     function buyBond(
         uint256 principalAmount_,
         uint256 minGain_,
         uint256 deadline_,
         uint16 forDays_
     )
       external override
+      returns (uint256)
     {
         _beforeProviderOp();
 
@@ -218,6 +220,15 @@ contract SmartYield is
             "SY: buyBond forDays"
         );
 
+        uint256 issuedAt = this.currentTime();
+
+        // ---
+
+        address buyer = msg.sender;
+
+        IProvider(pool)._takeUnderlying(buyer, principalAmount_);
+        IProvider(pool)._depositProvider(principalAmount_, 0);
+
         uint256 gain = this.bondGain(principalAmount_, forDays_);
 
         require(
@@ -235,15 +246,6 @@ contract SmartYield is
           "SY: buyBond underlyingLoanable"
         );
 
-        uint256 issuedAt = this.currentTime();
-
-        // ---
-
-        address buyer = msg.sender;
-
-        IProvider(pool)._takeUnderlying(buyer, principalAmount_);
-        IProvider(pool)._depositProvider(principalAmount_, 0);
-
         SeniorBond memory b =
             SeniorBond(
                 principalAmount_,
@@ -256,6 +258,8 @@ contract SmartYield is
         _mintBond(buyer, b);
 
         emit BuySeniorBond(buyer, seniorBondId, principalAmount_, gain, forDays_);
+
+        return gain;
     }
 
     // buy an nft with tokenAmount_ jTokens, that matures at abond maturesAt
@@ -371,32 +375,31 @@ contract SmartYield is
         emit RedeemJuniorBond(payTo, jBondId_, payAmnt);
     }
 
-
-    function providerRatePerDay()
-      external view virtual override
-    returns (uint256)
-    {
-        return MathUtils.min(
-          IController(controller).BOND_MAX_RATE_PER_DAY(),
-          IYieldOracle(IController(controller).oracle()).consult(1 days)
-        );
-    }
-
     // given a principal amount and a number of days, compute the guaranteed bond gain, excluding principal
     function bondGain(uint256 principalAmount_, uint16 forDays_)
-      external view override
+      external override
     returns (uint256)
     {
-        return IBondModel(IController(controller).bondModel()).gain(address(this), principalAmount_, forDays_);
+      return IBondModel(IController(controller).bondModel()).gain(
+        this.underlyingTotal(),
+        this.underlyingLoanable(),
+        IController(controller).providerRatePerDay(),
+        principalAmount_,
+        forDays_
+      );
     }
 
     // returns the maximum theoretically possible daily rate for senior bonds,
     // in reality the actual rate given to a bond will always be lower due to slippage
     function maxBondDailyRate()
-      external view override
+      external override
     returns (uint256)
     {
-        return IBondModel(IController(controller).bondModel()).maxDailyRate(address(this));
+      return IBondModel(IController(controller).bondModel()).maxDailyRate(
+        this.underlyingTotal(),
+        this.underlyingLoanable(),
+        IController(controller).providerRatePerDay()
+      );
     }
 
   // /externals
@@ -413,29 +416,29 @@ contract SmartYield is
 
     // jToken price * 1e18
     function price()
-      public view override
+      public override
     returns (uint256)
     {
         uint256 ts = totalSupply();
         return (ts == 0) ? 1e18 : (this.underlyingJuniors() * 1e18) / ts;
     }
 
     function underlyingTotal()
-      public view virtual override
+      public virtual override
     returns(uint256)
     {
       return IProvider(pool).underlyingBalance() - IProvider(pool).underlyingFees() - underlyingLiquidatedJuniors;
     }
 
     function underlyingJuniors()
-      public view virtual override
+      public virtual override
     returns (uint256)
     {
         return this.underlyingTotal() - abond.principal - this.abondPaid();
     }
 
     function underlyingLoanable()
-      public view virtual override
+      public virtual override
     returns (uint256)
     {
         // underlyingTotal - abond.principal - abond.gain - queued withdrawls

contracts/external-interfaces/compound-finance/ICToken.sol

@@ -7,6 +7,7 @@ interface ICToken {
     function redeemUnderlying(uint redeemAmount) external returns (uint256);
     function accrueInterest() external returns (uint256);
     function exchangeRateStored() external view returns (uint256);
+    function exchangeRateCurrent() external returns (uint256);
     function supplyRatePerBlock() external view returns (uint256);
     function totalBorrows() external view returns (uint256);
     function getCash() external view returns (uint256);

contracts/mocks/barnbridge/SmartYieldForModelMock.sol → contracts/mocks/barnbridge/SmartYieldForModelMock.sol.REMOVED

@@ -36,7 +36,7 @@ contract SmartYieldForModelMock is HasClock, SmartYield {
     }
 
     function checkGas(uint256 principal, uint16 forDays) public {
-      _lastCheckGas = IBondModel(IController(controller).bondModel()).gain(address(this), principal, forDays);
+      //_lastCheckGas = IBondModel(IController(controller).bondModel()).gain(address(this), principal, forDays);
     }
 
     function setMockValues(uint256 underlyingLoanable_, uint256 underlyingTotal_, uint256 providerRatePerDay_) public {

contracts/model/BondModelV1.sol

@@ -12,43 +12,39 @@ contract BondModelV1 is IBondModel {
     using SafeMath for uint256;
 
     function gain(
-        address pool_,
+        uint256 total_,
+        uint256 loanable_,
+        uint256 dailyRate_,
         uint256 principal_,
         uint16 forDays_
     )
-      external view override
+      external pure override
     returns (uint256)
     {
-        uint256 loanable = ISmartYield(pool_).underlyingLoanable();
-        uint256 total = ISmartYield(pool_).underlyingTotal();
-        uint256 dailyRate = ISmartYield(pool_).providerRatePerDay();
-
         uint256 aproxGain = MathUtils.compound2(
           principal_,
           //dailyRate * (loanable * 1e18 / (total + principal)) / 1e18,
-          uint256(1e18).mul(dailyRate).mul(loanable) / (total + principal_) / 1e18,
+          uint256(1e18).mul(dailyRate_).mul(loanable_) / (total_ + principal_) / 1e18,
           forDays_
         ).sub(principal_);
 
-        uint256 rate = uint256(1e18).mul(dailyRate).mul(loanable.sub(aproxGain, "BondModelV1: liquidity")) / (total + principal_) / 1e18;
+        uint256 rate = uint256(1e18).mul(dailyRate_).mul(loanable_.sub(aproxGain, "BondModelV1: liquidity")) / (total_ + principal_) / 1e18;
 
         return MathUtils.compound2(principal_, rate, forDays_).sub(principal_);
     }
 
     function maxDailyRate(
-      address pool_
+      uint256 total_,
+      uint256 loanable_,
+      uint256 dailyRate_
     )
-      external view override
+      external pure override
     returns (uint256)
     {
-      uint256 total = ISmartYield(pool_).underlyingTotal();
-      if (0 == total) {
+      if (0 == total_) {
         return 0;
       }
-
-      uint256 loanable = ISmartYield(pool_).underlyingLoanable();
-      uint256 dailyRate = ISmartYield(pool_).providerRatePerDay();
-      return uint256(1e18).mul(dailyRate).mul(loanable) / (total) / 1e18;
+      return uint256(1e18).mul(dailyRate_).mul(loanable_) / (total_) / 1e18;
     }
 
 }

contracts/model/IBondModel.sol

@@ -4,8 +4,8 @@ pragma abicoder v2;
 
 interface IBondModel {
 
-    function gain(address pool_, uint256 principal_, uint16 forDays_) external view returns (uint256);
+    function gain(uint256 total_, uint256 loanable_, uint256 dailyRate_, uint256 principal_, uint16 forDays_) external pure returns (uint256);
 
-    function maxDailyRate(address pool_) external view returns (uint256);
+    function maxDailyRate(uint256 total_, uint256 loanable_, uint256 dailyRate_) external pure returns (uint256);
 
 }

contracts/oracle/IYieldOracle.sol

@@ -5,5 +5,5 @@ pragma abicoder v2;
 interface IYieldOracle {
     function update() external;
 
-    function consult(uint256 forInterval) external view returns (uint256 amountOut);
+    function consult(uint256 forInterval) external returns (uint256 amountOut);
 }

contracts/oracle/IYieldOraclelizable.sol

@@ -7,13 +7,6 @@ interface IYieldOraclelizable {
     // oracle should call this when updating
     function cumulatives()
       external
-    returns(uint256 cumulativeSecondlyYield);
+    returns(uint256 cumulativeYield);
 
-    // returns cumulative yield up to currentTime()
-    function currentCumulatives()
-      external view
-    returns (uint256 cumulativeSecondlyYield);
-
-    // needs to return block.timestamp, otherwise used for mocks
-    function currentTime() external view returns (uint256);
 }

contracts/oracle/YieldOracle.sol

@@ -74,7 +74,7 @@ contract YieldOracle is IYieldOracle {
         view
         returns (Observation storage firstObservation)
     {
-        uint8 observationIndex = observationIndexOf(pool.currentTime());
+        uint8 observationIndex = observationIndexOf(block.timestamp);
         // no overflow issue. if observationIndex + 1 overflows, result is still zero.
         uint8 firstObservationIndex = (observationIndex + 1) % granularity;
         firstObservation = yieldObservations[firstObservationIndex];
@@ -84,14 +84,14 @@ contract YieldOracle is IYieldOracle {
     // once per epoch period.
     function update() external virtual override {
         // get the observation for the current period
-        uint8 observationIndex = observationIndexOf(pool.currentTime());
+        uint8 observationIndex = observationIndexOf(block.timestamp);
         Observation storage observation = yieldObservations[observationIndex];
 
         // we only want to commit updates once per period (i.e. windowSize / granularity)
-        uint256 timeElapsed = pool.currentTime() - observation.timestamp;
+        uint256 timeElapsed = block.timestamp - observation.timestamp;
         if (timeElapsed > periodSize) {
             (uint256 yieldCumulative) = pool.cumulatives();
-            observation.timestamp = pool.currentTime();
+            observation.timestamp = block.timestamp;
             observation.yieldCumulative = yieldCumulative;
         }
     }
@@ -113,14 +113,13 @@ contract YieldOracle is IYieldOracle {
     // update must have been called for the bucket corresponding to timestamp `now - windowSize`
     function consult(uint256 forInterval)
         external
-        view
         override
         virtual
         returns (uint256 yieldForInterval)
     {
         Observation storage firstObservation = getFirstObservationInWindow();
 
-        uint256 timeElapsed = pool.currentTime() - firstObservation.timestamp;
+        uint256 timeElapsed = block.timestamp - firstObservation.timestamp;
 
         if (!(timeElapsed <= windowSize)) {
             // originally:
@@ -143,7 +142,7 @@ contract YieldOracle is IYieldOracle {
             return 0;
         }
 
-        (uint256 yieldCumulative) = pool.currentCumulatives();
+        (uint256 yieldCumulative) = pool.cumulatives();
 
         return
             computeAmountOut(