added fee connector

contracts/connectors/fee.sol

@@ -0,0 +1,78 @@
+pragma solidity ^0.6.0;
+pragma experimental ABIEncoderV2;
+
+interface MemoryInterface {
+    function getUint(uint _id) external returns (uint _num);
+    function setUint(uint _id, uint _val) external;
+}
+
+contract DSMath {
+    uint256 constant WAD = 10 ** 18;
+
+    function add(uint x, uint y) internal pure returns (uint z) {
+        require((z = x + y) >= x, "math-not-safe");
+    }
+
+    function mul(uint x, uint y) internal pure returns (uint z) {
+        require(y == 0 || (z = x * y) / y == x, "math-not-safe");
+    }
+
+    function wmul(uint x, uint y) internal pure returns (uint z) {
+        z = add(mul(x, y), WAD / 2) / WAD;
+    }
+}
+
+contract Setup is DSMath {
+
+     /**
+     * @dev Return InstAaMemory Address.
+     */
+    function getMemoryAddr() internal pure returns (address) {
+        return 0x8a5419CfC711B2343c17a6ABf4B2bAFaBb06957F;
+    }
+
+    /**
+     * @dev Get Uint value from InstaMemory Contract.
+    */
+    function getUint(uint getId, uint val) internal returns (uint returnVal) {
+        returnVal = getId == 0 ? val : MemoryInterface(getMemoryAddr()).getUint(getId);
+    }
+
+    /**
+     * @dev Set Uint value in InstaMemory Contract.
+    */
+    function setUint(uint setId, uint val) internal {
+        if (setId != 0) MemoryInterface(getMemoryAddr()).setUint(setId, val);
+    }
+
+     /**
+     * @dev Connector ID and Type. TODO: change.
+     */
+    function connectorID() public pure returns(uint _type, uint _id) {
+        (_type, _id) = (1, 37);
+    }
+
+}
+
+
+contract FeeResolver is Setup {
+
+    /**
+     * @dev Calculate fee
+     */
+    function calculateFee(uint amount, uint fee, uint getId, uint setId) external payable {
+        require(fee <= 5 * 10 ** 16, "Fee-more-than-5%"); // TODO: change
+        uint _amt = getUint(getId, amount);
+
+        uint feeAmt = wmul(_amt, fee);
+
+        uint totalAmt = add(_amt, feeAmt);
+
+        setUint(setId, totalAmt);
+    }
+}
+
+
+contract ConnectFee is FeeResolver {
+    string public constant name = "Fee-v1";
+}