// SPDX-License-Identifier: MIT

pragma solidity >0.5.4;

import "@openzeppelin/contracts-upgradeable/token/ERC20/presets/ERC20PresetMinterPauserUpgradeable.sol";

import "@openzeppelin/contracts-upgradeable/utils/math/SafeMathUpgradeable.sol";
import "../utils/DSMath.sol";

contract cDAIMock is DSMath, ERC20PresetMinterPauserUpgradeable {
	using SafeMathUpgradeable for uint256;

	ERC20PresetMinterPauserUpgradeable dai;

	uint256 exchangeRate = 200000000000000000000000000; // initial exchange rate 0.02 from original cToken
	uint256 mantissa = 28;

	constructor(ERC20PresetMinterPauserUpgradeable _dai) initializer {
		__ERC20PresetMinterPauser_init("Compound DAI", "cDAI");
		dai = _dai;
	}

	function underlying() public view returns (address) {
		return address(dai);
	}

	function mint(uint256 daiAmount) public returns (uint256) {
		dai.transferFrom(msg.sender, address(this), daiAmount);
		//mul by 1e10 to match to precision of 1e28 of the exchange rate
		_mint(
			msg.sender,
			((daiAmount / 1e10) * (10**mantissa)) / exchangeRateStored() // based on https://compound.finance/docs#protocol-math
		);

		return 0;
	}

	function redeem(uint256 cdaiAmount) public returns (uint256) {
		uint256 daiAmount = (cdaiAmount * 1e10 * exchangeRateStored()) / 1e28; // based on https://compound.finance/docs#protocol-math
		//div to reduce precision from 1e28 of exchange rate to 1e27 that DSMath works on
		// uint256 daiAmount = cdaiAmount.mul(100).div(99);
		_burn(msg.sender, cdaiAmount);
		dai.transfer(msg.sender, daiAmount);
		return 0;
	}

	function redeemUnderlying(uint256 daiAmount) public returns (uint256) {
		uint256 cdaiAmount = ((daiAmount / 1e10) * (10**mantissa)) /
			exchangeRateStored(); // based on https://compound.finance/docs#protocol-math
		_burn(msg.sender, cdaiAmount);
		dai.transfer(msg.sender, daiAmount);
		return 0;
	}

	function exchangeRateCurrent() public returns (uint256) {
		exchangeRate += uint256(1e28).div(100);
		return exchangeRate;
	}

	function exchangeRateStored() public view returns (uint256) {
		return exchangeRate;
	}

	function decimals() public pure override returns (uint8) {
		return 8;
	}

	function increasePriceWithMultiplier(uint256 multiplier) public {
		exchangeRate += multiplier * uint256(1e28).div(100);
	}
}