// SPDX-License-Identifier: MIT
pragma solidity ^0.7.6;

import { DSMath } from "../../common/math.sol";
import { Basic } from "../../common/basic.sol";
import { TokenInterface, AccountInterface } from "../../common/interfaces.sol";
import { ComptrollerInterface, CompoundMappingInterface, CETHInterface, CTokenInterface } from "./interface.sol";

abstract contract Helpers is DSMath, Basic {
	/**
	 * @dev Compound CEth
	 */
	CETHInterface internal constant cEth =
		CETHInterface(0x4Ddc2D193948926D02f9B1fE9e1daa0718270ED5);

	/**
	 * @dev Compound Comptroller
	 */
	ComptrollerInterface internal constant troller =
		ComptrollerInterface(0x3d9819210A31b4961b30EF54bE2aeD79B9c9Cd3B);

	/**
	 * @dev Compound Mapping
	 */
	CompoundMappingInterface internal constant compMapping =
		CompoundMappingInterface(0xe7a85d0adDB972A4f0A4e57B698B37f171519e88);

	struct ImportData {
		address[] cTokens; // is the list of all tokens the user has interacted with (supply/borrow) -> used to enter markets
		uint256[] borrowAmts;
		uint256[] supplyAmts;
		address[] borrowTokens;
		address[] supplyTokens;
		CTokenInterface[] borrowCtokens;
		CTokenInterface[] supplyCtokens;
		address[] supplyCtokensAddr;
		address[] borrowCtokensAddr;
	}

	struct ImportInputData {
		address userAccount;
		string[] supplyIds;
		string[] borrowIds;
	}

	/**
	 * @dev enter compound market
	 * @param _cotkens array of ctoken addresses to enter compound market
	 */
	function _enterMarkets(address[] memory _cotkens) internal {
		troller.enterMarkets(_cotkens);
	}
}

contract CompoundHelper is Helpers {
	/**
	 * @notice fetch the borrow details of the user
	 * @dev approve the cToken to spend (borrowed amount of) tokens to allow for repaying later
	 * @param _importInputData the struct containing borrowIds of the users borrowed tokens
	 * @param data struct used to store the final data on which the CompoundHelper contract functions operate
	 * @return ImportData the final value of param data
	 */
	function getBorrowAmounts(
		ImportInputData memory _importInputData,
		ImportData memory data
	) internal returns (ImportData memory) {
		if (_importInputData.borrowIds.length > 0) {
			// initialize arrays for borrow data
			uint256 _length = _importInputData.borrowIds.length;
			data.borrowTokens = new address[](_length);
			data.borrowCtokens = new CTokenInterface[](_length);
			data.borrowCtokensAddr = new address[](_length);
			data.borrowAmts = new uint256[](_length);

			// populate the arrays with borrow tokens, cToken addresses and instances, and borrow amounts
			for (uint256 i; i < _length; i++) {
				(address _token, address _cToken) = compMapping.getMapping(
					_importInputData.borrowIds[i]
				);

				require(
					_token != address(0) && _cToken != address(0),
					"ctoken mapping not found"
				);

				data.cTokens[i] = _cToken;

				data.borrowTokens[i] = _token;
				data.borrowCtokens[i] = CTokenInterface(_cToken);
				data.borrowCtokensAddr[i] = _cToken;
				data.borrowAmts[i] = data.borrowCtokens[i].borrowBalanceCurrent(
					_importInputData.userAccount
				);

				// give the resp. cToken address approval to spend tokens
				if (_token != ethAddr && data.borrowAmts[i] > 0) {
					// will be required when repaying the borrow amount on behalf of the user
					TokenInterface(_token).approve(_cToken, data.borrowAmts[i]);
				}
			}
		}
		return data;
	}

	/**
	 * @notice fetch the supply details of the user
	 * @dev only reads data from blockchain hence view
	 * @param _importInputData the struct containing supplyIds of the users supplied tokens
	 * @param data struct used to store the final data on which the CompoundHelper contract functions operate
	 * @return ImportData the final value of param data
	 */
	function getSupplyAmounts(
		ImportInputData memory _importInputData,
		ImportData memory data
	) internal view returns (ImportData memory) {
		// initialize arrays for supply data
		uint256 _length = _importInputData.supplyIds.length;
		data.supplyTokens = new address[](_length);
		data.supplyCtokens = new CTokenInterface[](_length);
		data.supplyCtokensAddr = new address[](_length);
		data.supplyAmts = new uint256[](_length);

		// populate arrays with supply data (supply tokens address, cToken addresses, cToken instances and supply amounts)
		for (uint256 i; i < _length; i++) {
			(address _token, address _cToken) = compMapping.getMapping(
				_importInputData.supplyIds[i]
			);

			require(
				_token != address(0) && _cToken != address(0),
				"ctoken mapping not found"
			);

			uint256 _supplyIndex = add(i, _importInputData.borrowIds.length);
			data.cTokens[_supplyIndex] = _cToken;

			data.supplyTokens[i] = _token;
			data.supplyCtokens[i] = CTokenInterface(_cToken);
			data.supplyCtokensAddr[i] = (_cToken);
			data.supplyAmts[i] = data.supplyCtokens[i].balanceOf(
				_importInputData.userAccount
			);
		}
		return data;
	}

	/**
	 * @notice repays the debt taken by user on Compound on its behalf to free its collateral for transfer
	 * @dev uses the cEth contract for ETH repays, otherwise the general cToken interface
	 * @param _userAccount the user address for which debt is to be repayed
	 * @param _cTokenContracts array containing all interfaces to the cToken contracts in which the user has debt positions
	 * @param _borrowAmts array containing the amount borrowed for each token
	 */
	function _repayUserDebt(
		address _userAccount,
		CTokenInterface[] memory _cTokenContracts,
		uint256[] memory _borrowAmts
	) internal {
		for (uint256 i; i < _cTokenContracts.length; i++) {
			if (_borrowAmts[i] > 0) {
				if (address(_cTokenContracts[i]) == address(cEth))
					cEth.repayBorrowBehalf{ value: _borrowAmts[i] }(
						_userAccount
					);
				else
					require(
						_cTokenContracts[i].repayBorrowBehalf(
							_userAccount,
							_borrowAmts[i]
						) == 0,
						"repayOnBehalf-failed"
					);
			}
		}
	}

	/**
	 * @notice used to transfer user's supply position on Compound to DSA
	 * @dev uses the transferFrom token in cToken contracts to transfer positions, requires approval from user first
	 * @param _userAccount address of the user account whose position is to be transferred
	 * @param _cTokenContracts array containing all interfaces to the cToken contracts in which the user has supply positions
	 * @param _amts array containing the amount supplied for each token
	 */
	function _transferTokensToDsa(
		address _userAccount,
		CTokenInterface[] memory _cTokenContracts,
		uint256[] memory _amts
	) internal {
		for (uint256 i; i < _cTokenContracts.length; i++)
			if (_amts[i] > 0)
				require(
					_cTokenContracts[i].transferFrom(
						_userAccount,
						address(this),
						_amts[i]
					),
					"ctoken-transfer-failed-allowance?"
				);
	}

	/**
	 * @notice borrows the user's debt positions from Compound via DSA, so that its debt positions get imported to DSA
	 * @dev actually borrow some extra amount than the original position to cover the flash loan fee
	 * @param _cTokenContracts array containing all interfaces to the cToken contracts in which the user has debt positions
	 * @param _amts array containing the amounts the user had borrowed originally from Compound plus the flash loan fee
	 * @param _flashLoanFees flash loan fee (in percentage and scaled up to 10**2)
	 */
	function _borrowDebtPosition(
		CTokenInterface[] memory _cTokenContracts,
		uint256[] memory _amts,
		uint256[] memory _flashLoanFees
	) internal {
		for (uint256 i; i < _cTokenContracts.length; i++)
			if (_amts[i] > 0)
				require(
					_cTokenContracts[i].borrow(
						add(_amts[i], _flashLoanFees[i])
					) == 0,
					"borrow-failed-collateral?"
				);
	}
}