pragma solidity >=0.4.21 <0.6.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through `transferFrom`. This is
     * zero by default.
     *
     * This value changes when `approve` or `transferFrom` are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an `Approval` event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to `approve`. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

/**
 * @dev Implementation of the `IERC20` interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using `_mint`.
 * For a generic mechanism see `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an `Approval` event is emitted on calls to `transferFrom`.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard `decreaseAllowance` and `increaseAllowance`
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See `IERC20.approve`.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    /**
     * @dev See `IERC20.totalSupply`.
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IERC20.transfer`.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IERC20.allowance`.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IERC20.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of `ERC20`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to `transfer`, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a `Transfer` event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a `Transfer` event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

     /**
     * @dev Destoys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a `Transfer` event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an `Approval` event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Destoys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See `_burn` and `_approve`.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, msg.sender, _allowances[account][msg.sender].sub(amount));
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be aplied to your functions to restrict their use to
 * the owner.
 */
contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), _owner);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * > Note: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// Compound finance ERC20 market interface
interface CERC20 {
  function mint(uint mintAmount) external returns (uint);
  function redeemUnderlying(uint redeemAmount) external returns (uint);
  function borrow(uint borrowAmount) external returns (uint);
  function repayBorrow(uint repayAmount) external returns (uint);
  function borrowBalanceCurrent(address account) external returns (uint);
  function exchangeRateCurrent() external returns (uint);
  function transfer(address recipient, uint256 amount) external returns (bool);

  function balanceOf(address account) external view returns (uint);
  function decimals() external view returns (uint);
  function underlying() external view returns (address);
  function exchangeRateStored() external view returns (uint);
}

// Compound finance comptroller
interface Comptroller {
  function enterMarkets(address[] calldata cTokens) external returns (uint[] memory);
  function markets(address cToken) external view returns (bool isListed, uint256 collateralFactorMantissa);
}

contract PooledCDAI is ERC20, Ownable {
  uint256 internal constant PRECISION = 10 ** 18;

  address public constant COMPTROLLER_ADDRESS = 0x3d9819210A31b4961b30EF54bE2aeD79B9c9Cd3B;
  address public constant CDAI_ADDRESS = 0xF5DCe57282A584D2746FaF1593d3121Fcac444dC;
  address public constant DAI_ADDRESS = 0x89d24A6b4CcB1B6fAA2625fE562bDD9a23260359;

  string private _name;
  string private _symbol;

  address public beneficiary; // the account that will receive the interests from Compound

  event Mint(address indexed sender, address indexed to, uint256 amount);
  event Burn(address indexed sender, address indexed to, uint256 amount);
  event WithdrawInterest(address indexed sender, address beneficiary, uint256 amount, bool indexed inDAI);
  event SetBeneficiary(address oldBeneficiary, address newBeneficiary);

  /**
    * @dev Sets the values for `name` and `symbol`. Both of
    * these values are immutable: they can only be set once during
    * construction.
    */
  constructor (string memory name, string memory symbol, address _beneficiary) public {
    _name = name;
    _symbol = symbol;

    // Set beneficiary
    require(_beneficiary != address(0), "Beneficiary can't be zero");
    beneficiary = _beneficiary;
    emit SetBeneficiary(address(0), _beneficiary);

    // Enter cDAI market
    Comptroller troll = Comptroller(COMPTROLLER_ADDRESS);
    address[] memory cTokens = new address[](1);
    cTokens[0] = CDAI_ADDRESS;
    uint[] memory errors = troll.enterMarkets(cTokens);
    require(errors[0] == 0, "Failed to enter cDAI market");
  }

  /**
    * @dev Returns the name of the token.
    */
  function name() public view returns (string memory) {
    return _name;
  }

  /**
    * @dev Returns the symbol of the token, usually a shorter version of the
    * name.
    */
  function symbol() public view returns (string memory) {
    return _symbol;
  }

  /**
    * @dev Returns the number of decimals used to get its user representation.
    * For example, if `decimals` equals `2`, a balance of `505` tokens should
    * be displayed to a user as `5,05` (`505 / 10 ** 2`).
    *
    * Tokens usually opt for a value of 18, imitating the relationship between
    * Ether and Wei.
    *
    * NOTE: This information is only used for _display_ purposes: it in
    * no way affects any of the arithmetic of the contract, including
    * {IERC20-balanceOf} and {IERC20-transfer}.
    */
  function decimals() public pure returns (uint8) {
    return 18;
  }

  function mint(address to, uint256 amount) public returns (bool) {
    // transfer `amount` DAI from msg.sender
    ERC20 dai = ERC20(DAI_ADDRESS);
    require(dai.transferFrom(msg.sender, address(this), amount), "Failed to transfer DAI from msg.sender");

    // use `amount` DAI to mint cDAI
    CERC20 cDAI = CERC20(CDAI_ADDRESS);
    require(dai.approve(CDAI_ADDRESS, 0), "Failed to clear DAI allowance");
    require(dai.approve(CDAI_ADDRESS, amount), "Failed to set DAI allowance");
    require(cDAI.mint(amount) == 0, "Failed to mint cDAI");

    // mint `amount` pcDAI for `to`
    _mint(to, amount);

    // emit event
    emit Mint(msg.sender, to, amount);

    return true;
  }

  function burn(address to, uint256 amount) public returns (bool) {
    // burn `amount` pcDAI for msg.sender
    _burn(msg.sender, amount);

    // burn cDAI for `amount` DAI
    CERC20 cDAI = CERC20(CDAI_ADDRESS);
    require(cDAI.redeemUnderlying(amount) == 0, "Failed to redeem");

    // transfer DAI to `to`
    ERC20 dai = ERC20(DAI_ADDRESS);
    require(dai.transfer(to, amount), "Failed to transfer DAI to target");

    // emit event
    emit Burn(msg.sender, to, amount);

    return true;
  }

  function accruedInterestCurrent() public returns (uint256) {
    CERC20 cDAI = CERC20(CDAI_ADDRESS);
    return cDAI.exchangeRateCurrent().mul(cDAI.balanceOf(address(this))).div(PRECISION).sub(totalSupply());
  }

  function accruedInterestStored() public view returns (uint256) {
    CERC20 cDAI = CERC20(CDAI_ADDRESS);
    return cDAI.exchangeRateStored().mul(cDAI.balanceOf(address(this))).div(PRECISION).sub(totalSupply());
  }

  function withdrawInterestInDAI() public returns (bool) {
    // calculate amount of interest in DAI
    uint256 interestAmount = accruedInterestCurrent();

    // burn cDAI
    CERC20 cDAI = CERC20(CDAI_ADDRESS);
    require(cDAI.redeemUnderlying(interestAmount) == 0, "Failed to redeem");

    // transfer DAI to beneficiary
    ERC20 dai = ERC20(DAI_ADDRESS);
    require(dai.transfer(beneficiary, interestAmount), "Failed to transfer DAI to beneficiary");

    emit WithdrawInterest(msg.sender, beneficiary, interestAmount, true);

    return true;
  }

  function withdrawInterestInCDAI() public returns (bool) {
    // calculate amount of cDAI to transfer
    CERC20 cDAI = CERC20(CDAI_ADDRESS);
    uint256 interestAmountInCDAI = accruedInterestCurrent().mul(PRECISION).div(cDAI.exchangeRateCurrent());

    // transfer cDAI to beneficiary
    require(cDAI.transfer(beneficiary, interestAmountInCDAI), "Failed to transfer cDAI to beneficiary");

    // emit event
    emit WithdrawInterest(msg.sender, beneficiary, interestAmountInCDAI, false);

    return true;
  }

  function setBeneficiary(address newBeneficiary) public onlyOwner returns (bool) {
    require(newBeneficiary != address(0), "Beneficiary can't be zero");
    emit SetBeneficiary(beneficiary, newBeneficiary);

    beneficiary = newBeneficiary;

    return true;
  }

  function() external payable {
    revert("Contract doesn't support receiving Ether");
  }
}

contract PooledCDAIFactory {
  event CreatePool(address sender, address pool, bool indexed renounceOwnership);

  function createPCDAI(string memory name, string memory symbol, address _beneficiary, bool renounceOwnership) public returns (PooledCDAI) {
    PooledCDAI pcDAI = _createPCDAI(name, symbol, _beneficiary, renounceOwnership);
    emit CreatePool(msg.sender, address(pcDAI), renounceOwnership);
    return pcDAI;
  }

  function _createPCDAI(string memory name, string memory symbol, address _beneficiary, bool renounceOwnership) internal returns (PooledCDAI) {
    PooledCDAI pcDAI = new PooledCDAI(name, symbol, _beneficiary);
    if (renounceOwnership) {
      pcDAI.renounceOwnership();
    } else {
      pcDAI.transferOwnership(msg.sender);
    }
    return pcDAI;
  }
}

contract MetadataPooledCDAIFactory is PooledCDAIFactory {
  event CreatePoolWithMetadata(address sender, address pool, bool indexed renounceOwnership, bytes metadata);

  function createPCDAIWithMetadata(
    string memory name,
    string memory symbol,
    address _beneficiary,
    bool renounceOwnership,
    bytes memory metadata
  ) public returns (PooledCDAI) {
    PooledCDAI pcDAI = _createPCDAI(name, symbol, _beneficiary, renounceOwnership);
    emit CreatePoolWithMetadata(msg.sender, address(pcDAI), renounceOwnership, metadata);
  }
}

interface KyberNetworkProxy {
  function getExpectedRate(ERC20 src, ERC20 dest, uint srcQty) external view
      returns (uint expectedRate, uint slippageRate);

  function tradeWithHint(
    ERC20 src, uint srcAmount, ERC20 dest, address payable destAddress, uint maxDestAmount,
    uint minConversionRate, address walletId, bytes calldata hint) external payable returns(uint);
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

/**
 * @dev Collection of functions related to the address type,
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * This test is non-exhaustive, and there may be false-negatives: during the
     * execution of a contract's constructor, its address will be reported as
     * not containing a contract.
     *
     * > It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
}

/**
  @dev An extension to PooledCDAI that enables minting & burning pcDAI using ETH & ERC20 tokens
    supported by Kyber Network, rather than just DAI. There's no need to deploy one for each pool,
    since it uses pcDAI as a black box.
 */
contract PooledCDAIKyberExtension {
  using SafeERC20 for ERC20;
  using SafeERC20 for PooledCDAI;
  using SafeMath for uint256;

  address public constant DAI_ADDRESS = 0x89d24A6b4CcB1B6fAA2625fE562bDD9a23260359;
  address public constant KYBER_ADDRESS = 0x818E6FECD516Ecc3849DAf6845e3EC868087B755;
  ERC20 internal constant ETH_TOKEN_ADDRESS = ERC20(0x00eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee);
  bytes internal constant PERM_HINT = "PERM"; // Only use permissioned reserves from Kyber
  uint internal constant MAX_QTY   = (10**28); // 10B tokens

  function mintWithETH(PooledCDAI pcDAI, address to) public payable returns (bool) {
    // convert `msg.value` ETH to DAI
    ERC20 dai = ERC20(DAI_ADDRESS);
    (uint256 actualDAIAmount, uint256 actualETHAmount) = _kyberTrade(ETH_TOKEN_ADDRESS, msg.value, dai);

    // mint `actualDAIAmount` pcDAI
    _mint(pcDAI, to, actualDAIAmount);

    // return any leftover ETH
    if (actualETHAmount < msg.value) {
      msg.sender.transfer(msg.value.sub(actualETHAmount));
    }

    return true;
  }

  function mintWithToken(PooledCDAI pcDAI, address tokenAddress, address to, uint256 amount) public returns (bool) {
    require(tokenAddress != address(ETH_TOKEN_ADDRESS), "Use mintWithETH() instead");
    require(tokenAddress != DAI_ADDRESS, "Use mint() instead");

    // transfer `amount` token from msg.sender
    ERC20 token = ERC20(tokenAddress);
    token.safeTransferFrom(msg.sender, address(this), amount);

    // convert `amount` token to DAI
    ERC20 dai = ERC20(DAI_ADDRESS);
    (uint256 actualDAIAmount, uint256 actualTokenAmount) = _kyberTrade(token, amount, dai);

    // mint `actualDAIAmount` pcDAI
    _mint(pcDAI, to, actualDAIAmount);

    // return any leftover tokens
    if (actualTokenAmount < amount) {
      token.safeTransfer(msg.sender, amount.sub(actualTokenAmount));
    }

    return true;
  }

  function burnToETH(PooledCDAI pcDAI, address payable to, uint256 amount) public returns (bool) {
    // burn `amount` pcDAI for msg.sender to get DAI
    _burn(pcDAI, amount);

    // convert `amount` DAI to ETH
    ERC20 dai = ERC20(DAI_ADDRESS);
    (uint256 actualETHAmount, uint256 actualDAIAmount) = _kyberTrade(dai, amount, ETH_TOKEN_ADDRESS);

    // transfer `actualETHAmount` ETH to `to`
    to.transfer(actualETHAmount);

    // transfer any leftover DAI
    if (actualDAIAmount < amount) {
      dai.safeTransfer(msg.sender, amount.sub(actualDAIAmount));
    }

    return true;
  }

  function burnToToken(PooledCDAI pcDAI, address tokenAddress, address to, uint256 amount) public returns (bool) {
    require(tokenAddress != address(ETH_TOKEN_ADDRESS), "Use burnToETH() instead");
    require(tokenAddress != DAI_ADDRESS, "Use burn() instead");

    // burn `amount` pcDAI for msg.sender to get DAI
    _burn(pcDAI, amount);

    // convert `amount` DAI to token
    ERC20 dai = ERC20(DAI_ADDRESS);
    ERC20 token = ERC20(tokenAddress);
    (uint256 actualTokenAmount, uint256 actualDAIAmount) = _kyberTrade(dai, amount, token);

    // transfer `actualTokenAmount` token to `to`
    token.safeTransfer(to, actualTokenAmount);

    // transfer any leftover DAI
    if (actualDAIAmount < amount) {
      dai.safeTransfer(msg.sender, amount.sub(actualDAIAmount));
    }

    return true;
  }

  function _mint(PooledCDAI pcDAI, address to, uint256 actualDAIAmount) internal {
    ERC20 dai = ERC20(DAI_ADDRESS);
    dai.safeApprove(address(pcDAI), 0);
    dai.safeApprove(address(pcDAI), actualDAIAmount);
    require(pcDAI.mint(to, actualDAIAmount), "Failed to mint pcDAI");
  }

  function _burn(PooledCDAI pcDAI, uint256 amount) internal {
    // transfer `amount` pcDAI from msg.sender
    pcDAI.safeTransferFrom(msg.sender, address(this), amount);

    // burn `amount` pcDAI for DAI
    require(pcDAI.burn(address(this), amount), "Failed to burn pcDAI");
  }

  /**
   * @notice Get the token balance of an account
   * @param _token the token to be queried
   * @param _addr the account whose balance will be returned
   * @return token balance of the account
   */
  function _getBalance(ERC20 _token, address _addr) internal view returns(uint256) {
    if (address(_token) == address(ETH_TOKEN_ADDRESS)) {
      return uint256(_addr.balance);
    }
    return uint256(_token.balanceOf(_addr));
  }

  function _toPayableAddr(address _addr) internal pure returns (address payable) {
    return address(uint160(_addr));
  }

  /**
   * @notice Wrapper function for doing token conversion on Kyber Network
   * @param _srcToken the token to convert from
   * @param _srcAmount the amount of tokens to be converted
   * @param _destToken the destination token
   * @return _destPriceInSrc the price of the dest token, in terms of source tokens
   *         _srcPriceInDest the price of the source token, in terms of dest tokens
   *         _actualDestAmount actual amount of dest token traded
   *         _actualSrcAmount actual amount of src token traded
   */
  function _kyberTrade(ERC20 _srcToken, uint256 _srcAmount, ERC20 _destToken)
    internal
    returns(
      uint256 _actualDestAmount,
      uint256 _actualSrcAmount
    )
  {
    // Get current rate & ensure token is listed on Kyber
    KyberNetworkProxy kyber = KyberNetworkProxy(KYBER_ADDRESS);
    (, uint256 rate) = kyber.getExpectedRate(_srcToken, _destToken, _srcAmount);
    require(rate > 0, "Price for token is 0 on Kyber");

    uint256 beforeSrcBalance = _getBalance(_srcToken, address(this));
    uint256 msgValue;
    if (_srcToken != ETH_TOKEN_ADDRESS) {
      msgValue = 0;
      _srcToken.safeApprove(KYBER_ADDRESS, 0);
      _srcToken.safeApprove(KYBER_ADDRESS, _srcAmount);
    } else {
      msgValue = _srcAmount;
    }
    _actualDestAmount = kyber.tradeWithHint.value(msgValue)(
      _srcToken,
      _srcAmount,
      _destToken,
      _toPayableAddr(address(this)),
      MAX_QTY,
      rate,
      0x8B2315243349f461045854beec3c5aFA84f600B6,
      PERM_HINT
    );
    require(_actualDestAmount > 0, "Received 0 dest token");
    if (_srcToken != ETH_TOKEN_ADDRESS) {
      _srcToken.safeApprove(KYBER_ADDRESS, 0);
    }

    _actualSrcAmount = beforeSrcBalance.sub(_getBalance(_srcToken, address(this)));
  }
}