Updated math.sol to use SafeMath from OZ;

update migration to deploy CurveSBTCProtocol;
Added Curvesbtc.sol sell method and got it compiled;

contracts/common/math.sol

@@ -1,36 +1,41 @@
 pragma solidity ^0.6.0;
 
+import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
+
 contract DSMath {
-    uint constant WAD = 10 ** 18;
-    uint constant RAY = 10 ** 27;
+  uint constant WAD = 10 ** 18;
+  uint constant RAY = 10 ** 27;
 
-    function add(uint x, uint y) internal pure returns (uint z) {
-        require((z = x + y) >= x, "math-not-safe");
-    }
+  function add(uint x, uint y) internal pure returns (uint z) {
+    SafeMath.add(x, y);
+  }
 
-    function sub(uint x, uint y) internal pure returns (uint z) {
-        require((z = x - y) <= x, "ds-math-sub-underflow");
-    }
+  function sub(uint x, uint y) internal pure returns (uint z) {
+    SafeMath.sub(x, y);
+  }
 
-    function mul(uint x, uint y) internal pure returns (uint z) {
-        require(y == 0 || (z = x * y) / y == x, "math-not-safe");
-    }
+  function mul(uint x, uint y) internal pure returns (uint z) {
+    SafeMath.mul(x, y);
+  }
 
+  function div(uint x, uint y) internal pure returns (uint z) {
+    SafeMath.div(x, y);
+  }
 
-    function wmul(uint x, uint y) internal pure returns (uint z) {
-        z = add(mul(x, y), WAD / 2) / WAD;
-    }
+  function wmul(uint x, uint y) internal pure returns (uint z) {
+    z = SafeMath.add(SafeMath.mul(x, y), WAD / 2) / WAD;
+  }
 
-    function wdiv(uint x, uint y) internal pure returns (uint z) {
-        z = add(mul(x, WAD), y / 2) / y;
-    }
+  function wdiv(uint x, uint y) internal pure returns (uint z) {
+    z = SafeMath.add(SafeMath.mul(x, WAD), y / 2) / y;
+  }
 
-    function rdiv(uint x, uint y) internal pure returns (uint z) {
-        z = add(mul(x, RAY), y / 2) / y;
-    }
+  function rdiv(uint x, uint y) internal pure returns (uint z) {
+    z = SafeMath.add(SafeMath.mul(x, RAY), y / 2) / y;
+  }
 
-    function rmul(uint x, uint y) internal pure returns (uint z) {
-        z = add(mul(x, y), RAY / 2) / RAY;
-    }
+  function rmul(uint x, uint y) internal pure returns (uint z) {
+    z = SafeMath.add(SafeMath.mul(x, y), RAY / 2) / RAY;
+  }
 
-}
+}

contracts/connectors/curvesbtc.sol

@@ -0,0 +1,115 @@
+pragma solidity ^0.6.0;
+
+// import files from common directory
+import { MemoryInterface, EventInterface} from "../common/interfaces.sol";
+import { Stores } from "../common/stores.sol";
+import { DSMath } from "../common/math.sol";
+
+// import files from OZ
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import {SafeCast} from "@openzeppelin/contracts/utils/SafeCast.sol";
+
+interface ICurve {
+  function coins(int128 tokenId) external view returns (address token);
+  function calc_token_amount(uint256[3] calldata amounts, bool deposit) external returns (uint256 amount);
+  function add_liquidity(uint256[3] calldata amounts, uint256 min_mint_amount) external;
+  function get_dy(int128 sellTokenId, int128 buyTokenId, uint256 sellTokenAmt) external returns (uint256 buyTokenAmt);
+  function exchange(int128 sellTokenId, int128 buyTokenId, uint256 sellTokenAmt, uint256 minBuyToken) external;
+  function remove_liquidity_imbalance(uint256[3] calldata amounts, uint256 max_burn_amount) external;
+  function calc_withdraw_one_coin(uint256 _token_amount, int128 i) external returns (uint256 amount);
+}
+
+contract CurveSBTCHelpers is Stores, DSMath{
+  /**
+  * @dev Return Curve Swap Address
+  */
+  function getCurveSwapAddr() internal pure returns (address) {
+    return 0x7fC77b5c7614E1533320Ea6DDc2Eb61fa00A9714;
+  }
+
+  /**
+  * @dev Return Curve Token Address
+  */
+  function getCurveTokenAddr() internal pure returns (address) {
+    return 0x075b1bb99792c9E1041bA13afEf80C91a1e70fB3;
+  }
+
+  function convert18ToDec(uint _dec, uint256 _amt) internal pure returns (uint256 amt) {
+    amt = div(_amt, 10 ** (18 - _dec));
+  }
+
+  function convertTo18(uint _dec, uint256 _amt) internal pure returns (uint256 amt) {
+    amt = mul(_amt, 10 ** (18 - _dec));
+  }
+
+  function getTokenI(address token) internal pure returns (int128 i) {
+    if (token == address(0xEB4C2781e4ebA804CE9a9803C67d0893436bB27D)) {
+      // RenBTC Token
+      i = 0;
+    } else if (token == address(0x2260FAC5E5542a773Aa44fBCfeDf7C193bc2C599)) {
+      // WBTC Token
+      i = 1;
+    } else if (token == address(0xfE18be6b3Bd88A2D2A7f928d00292E7a9963CfC6)) {
+      // SBTC Token
+      i = 2;
+    } else {
+      revert("token-not-found.");
+    }
+  }
+}
+
+contract CurveSBTCProtocol is CurveSBTCHelpers {
+
+  // Events
+  event LogSell(
+    address indexed buyToken,
+    address indexed sellToken,
+    uint256 buyAmt,
+    uint256 sellAmt,
+    uint256 getId,
+    uint256 setId
+  );
+  event LogDeposit(address token, uint256 amt, uint256 mintAmt, uint256 getId, uint256 setId);
+  event LogWithdraw(address token, uint256 amt, uint256 burnAmt, uint256 getId,  uint256 setId);
+
+  /**
+  * @dev Sell Stable ERC20_Token.
+  * @param buyAddr buying token address.
+  * @param sellAddr selling token amount.
+  * @param sellAmt selling token amount.
+  * @param unitAmt unit amount of buyAmt/sellAmt with slippage.
+  * @param getId Get token amount at this ID from `InstaMemory` Contract.
+  * @param setId Set token amount at this ID in `InstaMemory` Contract.
+  */
+  function sell(
+    address buyAddr,
+    address sellAddr,
+    uint sellAmt,
+    uint unitAmt,
+    uint getId,
+    uint setId
+  ) external payable {
+    uint _sellAmt = getUint(getId, sellAmt);
+    ICurve curve = ICurve(getCurveSwapAddr());
+    ERC20 _buyToken = ERC20(buyAddr);
+    ERC20 _sellToken = ERC20(sellAddr);
+    _sellAmt = _sellAmt == uint(-1) ? _sellToken.balanceOf(address(this)) : _sellAmt;
+    _sellToken.approve(address(curve), _sellAmt);
+
+    uint _slippageAmt = convert18ToDec(_buyToken.decimals(), wmul(unitAmt, convertTo18(_sellToken.decimals(), _sellAmt)));
+
+    uint intialBal = _buyToken.balanceOf(address(this));
+    curve.exchange(getTokenI(sellAddr), getTokenI(buyAddr), _sellAmt, _slippageAmt);
+    uint finalBal = _buyToken.balanceOf(address(this));
+
+    uint _buyAmt = sub(finalBal, intialBal);
+
+    setUint(setId, _buyAmt);
+
+    emit LogSell(buyAddr, sellAddr, _buyAmt, _sellAmt, getId, setId);
+    bytes32 _eventCode = keccak256("LogSell(address,address,uint256,uint256,uint256,uint256)");
+    bytes memory _eventParam = abi.encode(buyAddr, sellAddr, _buyAmt, _sellAmt, getId, setId);
+    emitEvent(_eventCode, _eventParam);
+  }
+
+}

migrations/2_deploy_connector.js

@@ -1,5 +1,7 @@
-const Connector = artifacts.require("CurveProtocol"); // Change the Connector name while deploying.
+const CurveProtocol = artifacts.require("CurveProtocol");
+const CurveSBTCProtocol = artifacts.require("CurveSBTCProtocol");
 
 module.exports = function(deployer) {
-  deployer.deploy(Connector);
+  deployer.deploy(CurveProtocol);
+  deployer.deploy(CurveSBTCProtocol);
 };