dip-13.1: coupon transfer fix

protocol/contracts/dao/Getters.sol

@@ -116,9 +116,6 @@ contract Getters is State {
     }
 
     function balanceOfCoupons(address account, uint256 epoch) public view returns (uint256) {
-        if (outstandingCoupons(epoch) == 0) {
-            return 0;
-        }
         return _state.accounts[account].coupons[epoch];
     }
 
@@ -150,6 +147,10 @@ contract Getters is State {
      * Epoch
      */
 
+    function price() public view returns (uint256) {
+        return _state13.price.asUint256();
+    }
+
     function epoch() public view returns (uint256) {
         return _state.epoch.current;
     }

protocol/contracts/dao/Implementation.sol

@@ -35,7 +35,7 @@ contract Implementation is State, Bonding, Market, Regulator, Govern {
         mintToAccount(msg.sender, 150e18); // 150 DSD to committer
         // contributor  rewards:
         mintToAccount(0xF414CFf71eCC35320Df0BB577E3Bc9B69c9E1f07, 1000e18); // 1000 DSD to devnull
-        mintToAccount(0x35F32d099fb9E08b706A6fa41D639EEB69F8A906, 2000e18); // 2000 DSD to degendegen9
+        mintToAccount(0x35F32d099fb9E08b706A6fa41D639EEB69F8A906, 3000e18); // 3000 DSD to degendegen9
     }
 
     function advance() external incentivized {

protocol/contracts/dao/Market.sol

@@ -144,10 +144,20 @@ contract Market is Comptroller, Curve {
     function redeemCoupons(uint256 couponEpoch, uint256 amount) external {
         require(_state13.price.greaterThan(Decimal.one()), "Market: not in expansion");
         require(epoch().sub(couponEpoch) >= 2, "Market: Too early to redeem");
-		require(amount != 0, "Market: Amount too low");
+        require(amount != 0, "Market: Amount too low");
 
-        uint256 couponAmount = balanceOfCoupons(msg.sender, couponEpoch)
-            .mul(amount).div(balanceOfCouponUnderlying(msg.sender, couponEpoch), "Market: No underlying");
+        uint256 underlying = balanceOfCouponUnderlying(msg.sender, couponEpoch);
+        require(underlying >= amount, "Market: Insufficient coupon underlying balance");
+
+        uint256 couponAmount;
+        if (outstandingCoupons(couponEpoch) == 0) {
+            // coupons have expired
+            _state.accounts[msg.sender].coupons[couponEpoch] = 0;
+        } else {
+            // coupons have not expired
+            couponAmount = _state.accounts[msg.sender].coupons[couponEpoch]
+                .mul(amount).div(underlying, "Market: No underlying");
+        }
 
         uint256 totalAmount = couponAmount.add(amount);
 
@@ -178,10 +188,20 @@ contract Market is Comptroller, Curve {
     function redeemCoupons(uint256 couponEpoch, uint256 amount, uint256 minOutput) external {
         require(_state13.price.greaterThan(Decimal.one()), "Market: not in expansion");
         require(epoch().sub(couponEpoch) >= 2, "Market: Too early to redeem");
-		require(amount != 0, "Market: Amount too low");
+        require(amount != 0, "Market: Amount too low");
 
-        uint256 couponAmount = balanceOfCoupons(msg.sender, couponEpoch)
-            .mul(amount).div(balanceOfCouponUnderlying(msg.sender, couponEpoch), "Market: No underlying");
+        uint256 underlying = balanceOfCouponUnderlying(msg.sender, couponEpoch);
+        require(underlying >= amount, "Market: Insufficient coupon underlying balance");
+
+        uint256 couponAmount;
+        if (outstandingCoupons(couponEpoch) == 0) {
+            // coupons have expired
+            _state.accounts[msg.sender].coupons[couponEpoch] = 0;
+        } else {
+            // coupons have not expired
+            couponAmount = _state.accounts[msg.sender].coupons[couponEpoch]
+                .mul(amount).div(underlying, "Market: No underlying");
+        }
 
         uint256 totalAmount = couponAmount.add(amount);
 
@@ -226,9 +246,28 @@ contract Market is Comptroller, Curve {
     function transferCoupons(address sender, address recipient, uint256 epoch, uint256 amount) external {
         require(sender != address(0), "Market: Coupon transfer from the zero address");
         require(recipient != address(0), "Market: Coupon transfer to the zero address");
+        require(amount != 0, "Market: Amount too low");
+
+        uint256 underlying = balanceOfCouponUnderlying(sender, epoch);
+        require(underlying >= amount, "Market: Insufficient coupon underlying balance");
 
-        decrementBalanceOfCoupons(sender, epoch, amount, "Market: Insufficient coupon balance");
-        incrementBalanceOfCoupons(recipient, epoch, amount);
+        uint256 couponAmount;
+        if (outstandingCoupons(epoch) == 0) {
+            // coupons have expired
+            _state.accounts[sender].coupons[epoch] = 0;
+        } else {
+            // coupons have not expired
+            couponAmount = _state.accounts[sender].coupons[epoch]
+                .mul(amount).div(underlying, "Market: No underlying");
+        }
+
+        decrementBalanceOfCouponUnderlying(sender, epoch, amount, "Market: Insufficient coupon underlying balance");
+        incrementBalanceOfCouponUnderlying(recipient, epoch, amount);
+
+        if (couponAmount != 0) {
+            decrementBalanceOfCoupons(sender, epoch, couponAmount, "Market: Insufficient coupon balance");
+            incrementBalanceOfCoupons(recipient, epoch, couponAmount);
+        }
 
         if (msg.sender != sender && allowanceCoupons(sender, msg.sender) != uint256(-1)) {
             decrementAllowanceCoupons(sender, msg.sender, amount, "Market: Insufficient coupon approval");