pragma solidity 0.5.7;
// produced by the Solididy File Flattener (c) David Appleton 2018
// contact : dave@akomba.com
// released under Apache 2.0 licence
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * NOTE: This is a feature of the next version of OpenZeppelin Contracts.
     * @dev Get it via `npm install @openzeppelin/contracts@next`.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        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-contracts/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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message 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.
     * NOTE: This is a feature of the next version of OpenZeppelin Contracts.
     * @dev Get it via `npm install @openzeppelin/contracts@next`.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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.
     *
     * NOTE: This is a feature of the next version of OpenZeppelin Contracts.
     * @dev Get it via `npm install @openzeppelin/contracts@next`.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

contract Ownable is Context {
    address private _owner;
    address private _nominatedOwner;

    event NewOwnerNominated(address indexed previousOwner, address indexed nominee);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Returns the address of the current nominated owner.
     */
    function nominatedOwner() external view returns (address) {
        return _nominatedOwner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _onlyOwner();
        _;
    }

    function _onlyOwner() internal view {
        require(_msgSender() == _owner, "caller is not owner");
    }

    /**
     * @dev Nominates a new owner `newOwner`.
     * Requires a follow-up `acceptOwnership`.
     * Can only be called by the current owner.
     */
    function nominateNewOwner(address newOwner) external onlyOwner {
        require(newOwner != address(0), "new owner is 0 address");
        emit NewOwnerNominated(_owner, newOwner);
        _nominatedOwner = newOwner;
    }

    /**
     * @dev Accepts ownership of the contract.
     */
    function acceptOwnership() external {
        require(_nominatedOwner == _msgSender(), "unauthorized");
        emit OwnershipTransferred(_owner, _nominatedOwner);
        _owner = _nominatedOwner;
    }

    /** Set `_owner` to the 0 address.
     * Only do this to deliberately lock in the current permissions.
     *
     * THIS CANNOT BE UNDONE! Call this only if you know what you're doing and why you're doing it!
     */
    function renounceOwnership(string calldata declaration) external onlyOwner {
        string memory requiredDeclaration = "I hereby renounce ownership of this contract forever.";
        require(
            keccak256(abi.encodePacked(declaration)) ==
            keccak256(abi.encodePacked(requiredDeclaration)),
            "declaration incorrect");

        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
}

contract ReserveEternalStorage is Ownable {

    using SafeMath for uint256;


    // ===== auth =====

    address public reserveAddress;

    event ReserveAddressTransferred(
        address indexed oldReserveAddress,
        address indexed newReserveAddress
    );

    /// On construction, set auth fields.
    constructor() public {
        reserveAddress = _msgSender();
        emit ReserveAddressTransferred(address(0), reserveAddress);
    }

    /// Only run modified function if sent by `reserveAddress`.
    modifier onlyReserveAddress() {
        require(_msgSender() == reserveAddress, "onlyReserveAddress");
        _;
    }

    /// Set `reserveAddress`.
    function updateReserveAddress(address newReserveAddress) external {
        require(newReserveAddress != address(0), "zero address");
        require(_msgSender() == reserveAddress || _msgSender() == owner(), "not authorized");
        emit ReserveAddressTransferred(reserveAddress, newReserveAddress);
        reserveAddress = newReserveAddress;
    }



    // ===== balance =====

    mapping(address => uint256) public balance;

    /// Add `value` to `balance[key]`, unless this causes integer overflow.
    ///
    /// @dev This is a slight divergence from the strict Eternal Storage pattern, but it reduces
    /// the gas for the by-far most common token usage, it's a *very simple* divergence, and
    /// `setBalance` is available anyway.
    function addBalance(address key, uint256 value) external onlyReserveAddress {
        balance[key] = balance[key].add(value);
    }

    /// Subtract `value` from `balance[key]`, unless this causes integer underflow.
    function subBalance(address key, uint256 value) external onlyReserveAddress {
        balance[key] = balance[key].sub(value);
    }

    /// Set `balance[key]` to `value`.
    function setBalance(address key, uint256 value) external onlyReserveAddress {
        balance[key] = value;
    }



    // ===== allowed =====

    mapping(address => mapping(address => uint256)) public allowed;

    /// Set `to`'s allowance of `from`'s tokens to `value`.
    function setAllowed(address from, address to, uint256 value) external onlyReserveAddress {
        allowed[from][to] = value;
    }
}