pragma solidity ^0.7.0;

import { DSMath } from "../../common/math.sol";
import { Basic } from "../../common/basic.sol";
import { TokenInterface } from "../../common/interfaces.sol";
import { AugustusSwapperInterface } from "./interface.sol";

abstract contract Helpers is DSMath, Basic {
	struct SwapData {
		TokenInterface sellToken;
		TokenInterface buyToken;
		uint256 _sellAmt;
		uint256 _buyAmt;
		uint256 unitAmt;
		bytes callData;
	}

	address internal constant paraswap =
		0xDEF171Fe48CF0115B1d80b88dc8eAB59176FEe57;

	function _swapHelper(SwapData memory swapData, uint256 wftmAmt)
		internal
		returns (uint256 buyAmt)
	{
		TokenInterface buyToken = swapData.buyToken;
		(uint256 _buyDec, uint256 _sellDec) = getTokensDec(
			buyToken,
			swapData.sellToken
		);
		uint256 _sellAmt18 = convertTo18(_sellDec, swapData._sellAmt);
		uint256 _slippageAmt = convert18ToDec(
			_buyDec,
			wmul(swapData.unitAmt, _sellAmt18)
		);

		uint256 initalBal = getTokenBal(buyToken);

		(bool success, ) = paraswap.call{ value: wftmAmt }(swapData.callData);
		if (!success) revert("paraswap-failed");

		uint256 finalBal = getTokenBal(buyToken);

		buyAmt = sub(finalBal, initalBal);

		require(_slippageAmt <= buyAmt, "Too much slippage");
	}

	function _swap(SwapData memory swapData, uint256 setId)
		internal
		returns (SwapData memory)
	{
		TokenInterface _sellAddr = swapData.sellToken;

		uint256 ftmAmt;

		if (address(_sellAddr) == ftmAddr) {
			ftmAmt = swapData._sellAmt;
		} else {
			address tokenProxy = AugustusSwapperInterface(paraswap)
				.getTokenTransferProxy();
			approve(TokenInterface(_sellAddr), tokenProxy, swapData._sellAmt);
		}

		swapData._buyAmt = _swapHelper(swapData, ftmAmt);

		setUint(setId, swapData._buyAmt);

		return swapData;
	}
}