fix: error in curve integration of ExchangeIssuanceLeveraged (#133)

* Add double check on returned dy

* Remove calculator call and just swap all of maxAmountIn

* Fix wrong value in weth deposit

* chore(CI): pin node-version to 16.

as a temporary fix to our hardhat dep version not supporting node 18.

---------

Co-authored-by: SnakePoison <[email protected]>

Author: ckoopmann

.github/workflows/publish.yaml

@@ -12,6 +12,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+      - uses: actions/setup-node@v3
+        with:
+          node-version: 16
       - name: copy env
         run: cp .env.default .env
       - name: install

contracts/exchangeIssuance/DEXAdapter.sol

@@ -420,27 +420,27 @@ library DEXAdapter {
         require(_path.length == 2, "ExchangeIssuance: CURVE_WRONG_PATH_LENGTH");
         (int128 i, int128 j) = _getCoinIndices(_pool, _path[0], _path[1], ICurveAddressProvider(_addresses.curveAddressProvider));
 
-        uint256 amountIn = _getAmountInCurve(
-            _pool,
-            i,
-            j,
-            _amountOut,
-            _addresses
-        );
-        require(amountIn <= _maxAmountIn, "ExchangeIssuance: CURVE_OVERSPENT");
 
         if(_path[0] == ETH_ADDRESS){
-            IWETH(_addresses.weth).withdraw(amountIn);
+            IWETH(_addresses.weth).withdraw(_maxAmountIn);
         }
 
-        uint256 returnedAmountOut = _exchangeCurve(i, j, _pool, amountIn, _amountOut, _path[0]);
+        uint256 returnedAmountOut = _exchangeCurve(i, j, _pool, _maxAmountIn, _amountOut, _path[0]);
         require(_amountOut <= returnedAmountOut, "ExchangeIssuance: CURVE_UNDERBOUGHT");
 
+        uint256 swappedBackAmountIn;
+        if(returnedAmountOut > _amountOut){
+            swappedBackAmountIn = _exchangeCurve(j, i, _pool, returnedAmountOut.sub(_amountOut), 0, _path[1]);
+            if(_path[0] == ETH_ADDRESS){
+                IWETH(_addresses.weth).deposit{ value: swappedBackAmountIn }();
+            }
+        }
+
         if(_path[_path.length-1] == ETH_ADDRESS){
-            IWETH(_addresses.weth).deposit{ value: returnedAmountOut }();
+            IWETH(_addresses.weth).deposit{ value: _amountOut }();
         }
 
-        return amountIn;
+        return _maxAmountIn.sub(swappedBackAmountIn);
     }
 
     function _exchangeCurve(