// File: contracts/GovernanceMothership.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/utils/EnumerableSet.sol";
import "./interfaces/IGovernanceModule.sol";
import "./utils/BalanceAccounting.sol";


contract GovernanceMothership is Ownable, BalanceAccounting {
    using SafeMath for uint256;
    using EnumerableSet for EnumerableSet.AddressSet;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event AddModule(address indexed module);
    event RemoveModule(address indexed module);

    IERC20 public immutable inchToken;

    EnumerableSet.AddressSet private _modules;

    constructor(IERC20 _inchToken) public {
        inchToken = _inchToken;
    }

    function name() external pure returns(string memory) {
        return "1INCH Token (Staked)";
    }

    function symbol() external pure returns(string memory) {
        return "st1INCH";
    }

    function decimals() external pure returns(uint8) {
        return 18;
    }

    function stake(uint256 amount) external {
        require(amount > 0, "Empty stake is not allowed");

        inchToken.transferFrom(msg.sender, address(this), amount);
        _mint(msg.sender, amount);
        _notifyFor(msg.sender, balanceOf(msg.sender));
        emit Transfer(address(0), msg.sender, amount);
    }

    function unstake(uint256 amount) external {
        require(amount > 0, "Empty unstake is not allowed");

        _burn(msg.sender, amount);
        _notifyFor(msg.sender, balanceOf(msg.sender));
        inchToken.transfer(msg.sender, amount);
        emit Transfer(msg.sender, address(0), amount);
    }

    function notify() external {
        _notifyFor(msg.sender, balanceOf(msg.sender));
    }

    function notifyFor(address account) external {
        _notifyFor(account, balanceOf(account));
    }

    function batchNotifyFor(address[] memory accounts) external {
        uint256 modulesLength = _modules.length();
        uint256[] memory balances = new uint256[](accounts.length);
        for (uint256 j = 0; j < accounts.length; ++j) {
            balances[j] = balanceOf(accounts[j]);
        }
        for (uint256 i = 0; i < modulesLength; ++i) {
            IGovernanceModule(_modules.at(i)).notifyStakesChanged(accounts, balances);
        }
    }

    function addModule(address module) external onlyOwner {
        require(_modules.add(module), "Module already registered");
        emit AddModule(module);
    }

    function removeModule(address module) external onlyOwner {
        require(_modules.remove(module), "Module was not registered");
        emit RemoveModule(module);
    }

    function _notifyFor(address account, uint256 balance) private {
        bytes32[] memory cached = _modules._inner._values;
        for (uint256 i = 0; i < cached.length; ++i) {
            IGovernanceModule(address(uint256(cached[i]))).notifyStakeChanged(account, balance);
        }
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/Context.sol";
/**
 * @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.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    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 virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the 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 virtual 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 virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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 Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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.
     *
     * IMPORTANT: 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);
}

// File: @openzeppelin/contracts/utils/EnumerableSet.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: contracts/interfaces/IGovernanceModule.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;


interface IGovernanceModule {
    function notifyStakeChanged(address account, uint256 newBalance) external;
    function notifyStakesChanged(address[] calldata accounts, uint256[] calldata newBalances) external;
}

// File: contracts/utils/BalanceAccounting.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "@openzeppelin/contracts/math/SafeMath.sol";


contract BalanceAccounting {
    using SafeMath for uint256;

    uint256 private _totalSupply;
    mapping(address => uint256) private _balances;

    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    function _mint(address account, uint256 amount) internal virtual {
        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
    }

    function _burn(address account, uint256 amount) internal virtual {
        _balances[account] = _balances[account].sub(amount, "Burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
    }

    function _set(address account, uint256 amount) internal virtual returns(uint256 oldAmount) {
        oldAmount = _balances[account];
        if (oldAmount != amount) {
            _balances[account] = amount;
            _totalSupply = _totalSupply.add(amount).sub(oldAmount);
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: contracts/utils/BaseRewards.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./BalanceAccounting.sol";


contract BaseRewards is Ownable, BalanceAccounting {
    event RewardAdded(uint256 reward);
    event RewardPaid(address indexed user, uint256 reward);

    uint256 public constant DURATION = 7 days;

    address public rewardDistribution;
    IERC20 public immutable gift;
    uint256 public periodFinish;
    uint256 public rewardRate;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;
    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;

    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();
        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
        }

        _;
    }

    modifier onlyRewardDistribution() {
        require(msg.sender == rewardDistribution, "Access denied");
        _;
    }

    constructor(IERC20 _gift) public {
        gift = _gift;
    }

    function lastTimeRewardApplicable() public view returns (uint256) {
        return Math.min(block.timestamp, periodFinish);
    }

    function rewardPerToken() public view returns (uint256) {
        if (totalSupply() == 0) {
            return rewardPerTokenStored;
        }
        return
            rewardPerTokenStored.add(
                lastTimeRewardApplicable()
                    .sub(lastUpdateTime)
                    .mul(rewardRate)
                    .mul(1e18)
                    .div(totalSupply())
            );
    }

    function earned(address account) public view returns (uint256) {
        return
            balanceOf(account)
                .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(rewards[account]);
    }

    function getReward() public updateReward(msg.sender) {
        uint256 reward = rewards[msg.sender];
        if (reward > 0) {
            rewards[msg.sender] = 0;
            gift.transfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }

    function notifyRewardAmount(uint256 reward) external onlyRewardDistribution updateReward(address(0)) {
        if (block.timestamp >= periodFinish) {
            rewardRate = reward.div(DURATION);
        } else {
            uint256 remaining = periodFinish.sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRate);
            rewardRate = reward.add(leftover).div(DURATION);
        }

        uint balance = gift.balanceOf(address(this));
        require(rewardRate <= balance.div(DURATION), "Reward is too big");

        lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp.add(DURATION);
        emit RewardAdded(reward);
    }

    function setRewardDistribution(address _rewardDistribution) external onlyOwner {
        rewardDistribution = _rewardDistribution;
    }
}

// File: @openzeppelin/contracts/math/Math.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../../utils/Context.sol";
import "./IERC20.sol";
import "../../math/SafeMath.sol";

/**
 * @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 {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * 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 Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

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

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual 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. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * 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 view virtual returns (uint8) {
        return _decimals;
    }

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

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override 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 virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

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

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        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 `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        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 virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][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 virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        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 virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _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 virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

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

    /**
     * @dev Destroys `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 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This 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 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

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

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

// File: contracts/StepVesting.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";


contract StepVesting is Ownable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    event ReceiverChanged(address oldWallet, address newWallet);

    uint256 public immutable started;
    IERC20 public immutable token;
    uint256 public immutable cliffDuration;
    uint256 public immutable stepDuration;
    uint256 public immutable cliffAmount;
    uint256 public immutable stepAmount;
    uint256 public immutable numOfSteps;

    address public receiver;
    uint256 public claimed;

    modifier onlyReceiver {
        require(msg.sender == receiver, "access denied");
        _;
    }

    constructor(
        IERC20 _token,
        uint256 _started,
        uint256 _cliffDuration,
        uint256 _stepDuration,
        uint256 _cliffAmount,
        uint256 _stepAmount,
        uint256 _numOfSteps,
        address _receiver
    ) public {
        token = _token;
        started = _started;
        cliffDuration = _cliffDuration;
        stepDuration = _stepDuration;
        cliffAmount = _cliffAmount;
        stepAmount = _stepAmount;
        numOfSteps = _numOfSteps;
        setReceiver(_receiver);
    }

    function available() public view returns(uint256) {
        return claimable().sub(claimed);
    }

    function claimable() public view returns(uint256) {
        if (block.timestamp < started.add(cliffDuration)) {
            return 0;
        }

        uint256 passedSinceCliff = block.timestamp.sub(started.add(cliffDuration));
        uint256 stepsPassed = Math.min(numOfSteps, passedSinceCliff.div(stepDuration));
        return cliffAmount.add(
            stepsPassed.mul(stepAmount)
        );
    }

    function setReceiver(address _receiver) public onlyOwner {
        require(_receiver != address(0), "Receiver is zero address");
        emit ReceiverChanged(receiver, _receiver);
        receiver = _receiver;
    }

    function kill(address target) external onlyOwner {
        require(target != address(0), "Transfer to zero address");
        uint256 amount = token.balanceOf(address(this));
        token.safeTransfer(target, amount);
    }

    function claim() external onlyReceiver {
        uint256 amount = available();
        claimed = claimed.add(amount);
        token.safeTransfer(msg.sender, amount);
    }
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @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 IERC20;` 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));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    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, "SafeERC20: decreased allowance below zero");
        _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. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "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");
        }
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on 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 Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: contracts/libraries/UniERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";


library UniERC20 {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    function isETH(IERC20 token) internal pure returns(bool) {
        return (address(token) == address(0));
    }

    function uniBalanceOf(IERC20 token, address account) internal view returns (uint256) {
        if (isETH(token)) {
            return account.balance;
        } else {
            return token.balanceOf(account);
        }
    }

    function uniTransfer(IERC20 token, address payable to, uint256 amount) internal {
        if (amount > 0) {
            if (isETH(token)) {
                to.transfer(amount);
            } else {
                token.safeTransfer(to, amount);
            }
        }
    }

    function uniTransferFrom(IERC20 token, address payable from, address to, uint256 amount) internal {
        if (amount > 0) {
            if (isETH(token)) {
                require(msg.value >= amount, "UniERC20: not enough value");
                require(from == msg.sender, "from is not msg.sender");
                require(to == address(this), "to is not this");
                if (msg.value > amount) {
                    // Return remainder if exist
                    from.transfer(msg.value.sub(amount));
                }
            } else {
                token.safeTransferFrom(from, to, amount);
            }
        }
    }
}

// File: contracts/modules/GovernanceRewards.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "./BaseGovernanceModule.sol";
import "../libraries/UniERC20.sol";
import "../utils/BaseRewards.sol";


contract GovernanceRewards is BaseGovernanceModule, BaseRewards {
    using SafeMath for uint256;
    using UniERC20 for IERC20;

    // solhint-disable-next-line no-empty-blocks
    constructor(IERC20 _gift, address _mothership) public BaseGovernanceModule(_mothership) BaseRewards(_gift) {}

    function _notifyStakeChanged(address account, uint256 newBalance) internal override updateReward(account) {
        _set(account, newBalance);
    }

    function rescueFunds(IERC20 token, uint256 amount) external onlyOwner {
        require(token != gift, "Can't rescue gift");

        token.uniTransfer(msg.sender, amount);
    }
}

// File: contracts/modules/BaseGovernanceModule.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../interfaces/IGovernanceModule.sol";


abstract contract BaseGovernanceModule is IGovernanceModule {
    address public immutable mothership;

    modifier onlyMothership {
        require(msg.sender == mothership, "Access restricted to mothership");

        _;
    }

    constructor(address _mothership) public {
        mothership = _mothership;
    }

    function notifyStakesChanged(address[] calldata accounts, uint256[] calldata newBalances) external override onlyMothership {
        require(accounts.length == newBalances.length, "Arrays length should be equal");

        for(uint256 i = 0; i < accounts.length; ++i) {
            _notifyStakeChanged(accounts[i], newBalances[i]);
        }
    }

    function notifyStakeChanged(address account, uint256 newBalance) external override onlyMothership {
        _notifyStakeChanged(account, newBalance);
    }

    function _notifyStakeChanged(address account, uint256 newBalance) internal virtual;
}

// File: contracts/modules/ExchangeGovernance.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../libraries/ExchangeConstants.sol";
import "../libraries/LiquidVoting.sol";
import "../libraries/SafeCast.sol";
import "../utils/BalanceAccounting.sol";
import "./BaseGovernanceModule.sol";


contract ExchangeGovernance is BaseGovernanceModule, BalanceAccounting {
    using Vote for Vote.Data;
    using LiquidVoting for LiquidVoting.Data;
    using VirtualVote for VirtualVote.Data;
    using SafeCast for uint256;

    event LeftoverGovernanceShareUpdate(address indexed user, uint256 vote, bool isDefault, uint256 amount);
    event LeftoverReferralShareUpdate(address indexed user, uint256 vote, bool isDefault, uint256 amount);

    LiquidVoting.Data private _leftoverGovernanceShare;

    constructor(address _mothership) public BaseGovernanceModule(_mothership) {
        _leftoverGovernanceShare.data.result = ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE.toUint104();
    }

    function parameters() external view returns(uint256 govShare, uint256 refShare) {
        govShare = _leftoverGovernanceShare.data.current();
        refShare = ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(govShare);
    }

    function leftoverGovernanceShare() external view returns(uint256) {
        return _leftoverGovernanceShare.data.current();
    }

    function leftoverGovernanceShareVotes(address user) external view returns(uint256) {
        return _leftoverGovernanceShare.votes[user].get(ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE);
    }

    function virtualLeftoverGovernanceShare() external view returns(uint104, uint104, uint48) {
        return (_leftoverGovernanceShare.data.oldResult, _leftoverGovernanceShare.data.result, _leftoverGovernanceShare.data.time);
    }

    //

    function leftoverReferralShare() external view returns(uint256) {
        return ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(_leftoverGovernanceShare.data.current());
    }

    function leftoverReferralShareVotes(address user) external view returns(uint256) {
        return ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(_leftoverGovernanceShare.votes[user].get(ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE));
    }

    function virtualLeftoverReferralShare() external view returns(uint104, uint104, uint48) {
        return (
            ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(_leftoverGovernanceShare.data.oldResult).toUint104(),
            ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(_leftoverGovernanceShare.data.result).toUint104(),
            _leftoverGovernanceShare.data.time
        );
    }

    ///

    function leftoverShareVote(uint256 govShare) external {
        uint256 refShare = ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(govShare, "Governance share is too high");

        uint256 balance = balanceOf(msg.sender);
        uint256 supply = totalSupply();

        _leftoverGovernanceShare.updateVote(
            msg.sender,
            _leftoverGovernanceShare.votes[msg.sender],
            Vote.init(govShare),
            balance,
            supply,
            ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE,
            _emitLeftoverGovernanceShareVoteUpdate
        );

        _emitLeftoverReferralShareVoteUpdate(msg.sender, refShare, false, balance);
    }

    function discardLeftoverShareVote() external {
        uint256 balance = balanceOf(msg.sender);
        uint256 supply = totalSupply();

        _leftoverGovernanceShare.updateVote(
           msg.sender,
           _leftoverGovernanceShare.votes[msg.sender],
           Vote.init(),
           balance,
           supply,
           ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE,
           _emitLeftoverGovernanceShareVoteUpdate
        );

        _emitLeftoverReferralShareVoteUpdate(msg.sender, ExchangeConstants._DEFAULT_LEFTOVER_REF_SHARE, true, balance);
    }

    function _notifyStakeChanged(address account, uint256 newBalance) internal override {
        uint256 balance = _set(account, newBalance);
        if (newBalance == balance) {
            return;
        }

        Vote.Data memory govShareVote = _leftoverGovernanceShare.votes[account];
        uint256 refShare = ExchangeConstants._LEFTOVER_TOTAL_SHARE.sub(govShareVote.get(ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE));
        uint256 supply = totalSupply();

        _leftoverGovernanceShare.updateBalance(
            account,
            govShareVote,
            balance,
            newBalance,
            supply,
            ExchangeConstants._DEFAULT_LEFTOVER_GOV_SHARE,
            _emitLeftoverGovernanceShareVoteUpdate
        );

        _emitLeftoverReferralShareVoteUpdate(
            account,
            refShare,
            govShareVote.isDefault(),
            newBalance
        );
    }

    function _emitLeftoverGovernanceShareVoteUpdate(address user, uint256 newDefaultShare, bool isDefault, uint256 balance) private {
        emit LeftoverGovernanceShareUpdate(user, newDefaultShare, isDefault, balance);
    }

    function _emitLeftoverReferralShareVoteUpdate(address user, uint256 newDefaultShare, bool isDefault, uint256 balance) private {
        emit LeftoverReferralShareUpdate(user, newDefaultShare, isDefault, balance);
    }
}

// File: contracts/libraries/ExchangeConstants.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;


library ExchangeConstants {
    uint256 internal constant _LEFTOVER_TOTAL_SHARE = 1e18;          // 100%
    uint256 internal constant _DEFAULT_LEFTOVER_GOV_SHARE = 0.8e18;  //  80%
    uint256 internal constant _DEFAULT_LEFTOVER_REF_SHARE = 0.2e18;  //  20%
}

// File: contracts/libraries/LiquidVoting.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "./SafeCast.sol";
import "./VirtualVote.sol";
import "./Vote.sol";


library LiquidVoting {
    using SafeMath for uint256;
    using SafeCast for uint256;
    using Vote for Vote.Data;
    using VirtualVote for VirtualVote.Data;

    struct Data {
        VirtualVote.Data data;
        uint256 _weightedSum;
        uint256 _defaultVotes;
        mapping(address => Vote.Data) votes;
    }

    function updateVote(
        LiquidVoting.Data storage self,
        address user,
        Vote.Data memory oldVote,
        Vote.Data memory newVote,
        uint256 balance,
        uint256 totalSupply,
        uint256 defaultVote,
        function(address, uint256, bool, uint256) emitEvent
    ) internal {
        return _update(self, user, oldVote, newVote, balance, balance, totalSupply, defaultVote, emitEvent);
    }

    function updateBalance(
        LiquidVoting.Data storage self,
        address user,
        Vote.Data memory oldVote,
        uint256 oldBalance,
        uint256 newBalance,
        uint256 newTotalSupply,
        uint256 defaultVote,
        function(address, uint256, bool, uint256) emitEvent
    ) internal {
        return _update(self, user, oldVote, newBalance == 0 ? Vote.init() : oldVote, oldBalance, newBalance, newTotalSupply, defaultVote, emitEvent);
    }

    function _update(
        LiquidVoting.Data storage self,
        address user,
        Vote.Data memory oldVote,
        Vote.Data memory newVote,
        uint256 oldBalance,
        uint256 newBalance,
        uint256 newTotalSupply,
        uint256 defaultVote,
        function(address, uint256, bool, uint256) emitEvent
    ) private {
        uint256 oldWeightedSum = self._weightedSum;
        uint256 newWeightedSum = oldWeightedSum;
        uint256 oldDefaultVotes = self._defaultVotes;
        uint256 newDefaultVotes = oldDefaultVotes;

        if (oldVote.isDefault()) {
            newDefaultVotes = newDefaultVotes.sub(oldBalance);
        } else {
            newWeightedSum = newWeightedSum.sub(oldBalance.mul(oldVote.get(defaultVote)));
        }

        if (newVote.isDefault()) {
            newDefaultVotes = newDefaultVotes.add(newBalance);
        } else {
            newWeightedSum = newWeightedSum.add(newBalance.mul(newVote.get(defaultVote)));
        }

        if (newWeightedSum != oldWeightedSum) {
            self._weightedSum = newWeightedSum;
        }

        if (newDefaultVotes != oldDefaultVotes) {
            self._defaultVotes = newDefaultVotes;
        }

        {
            uint256 newResult = newTotalSupply == 0 ? defaultVote : newWeightedSum.add(newDefaultVotes.mul(defaultVote)).div(newTotalSupply);
            VirtualVote.Data memory data = self.data;

            if (newResult != data.result) {
                VirtualVote.Data storage sdata = self.data;
                (sdata.oldResult, sdata.result, sdata.time) = (
                    data.current().toUint104(),
                    newResult.toUint104(),
                    block.timestamp.toUint48()
                );
            }
        }

        if (!newVote.eq(oldVote)) {
            self.votes[user] = newVote;
        }

        emitEvent(user, newVote.get(defaultVote), newVote.isDefault(), newBalance);
    }
}

// File: contracts/libraries/SafeCast.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

library SafeCast {
    function toUint216(uint256 value) internal pure returns (uint216) {
        require(value < 2**216, "value does not fit in 216 bits");
        return uint216(value);
    }

    function toUint104(uint256 value) internal pure returns (uint104) {
        require(value < 2**104, "value does not fit in 104 bits");
        return uint104(value);
    }

    function toUint48(uint256 value) internal pure returns (uint48) {
        require(value < 2**48, "value does not fit in 48 bits");
        return uint48(value);
    }

    function toUint40(uint256 value) internal pure returns (uint40) {
        require(value < 2**40, "value does not fit in 40 bits");
        return uint40(value);
    }
}

// File: contracts/libraries/VirtualVote.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";


library VirtualVote {
    using SafeMath for uint256;

    uint256 private constant _VOTE_DECAY_PERIOD = 1 days;

    struct Data {
        uint104 oldResult;
        uint104 result;
        uint48 time;
    }

    function current(VirtualVote.Data memory self) internal view returns(uint256) {
        uint256 timePassed = Math.min(_VOTE_DECAY_PERIOD, block.timestamp.sub(self.time));
        uint256 timeRemain = _VOTE_DECAY_PERIOD.sub(timePassed);
        return uint256(self.oldResult).mul(timeRemain).add(
            uint256(self.result).mul(timePassed)
        ).div(_VOTE_DECAY_PERIOD);
    }
}

// File: contracts/libraries/Vote.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;


library Vote {
    struct Data {
        uint256 value;
    }

    function eq(Vote.Data memory self, Vote.Data memory vote) internal pure returns(bool) {
        return self.value == vote.value;
    }

    function init() internal pure returns(Vote.Data memory data) {
        return Vote.Data({
            value: 0
        });
    }

    function init(uint256 vote) internal pure returns(Vote.Data memory data) {
        return Vote.Data({
            value: vote + 1
        });
    }

    function isDefault(Data memory self) internal pure returns(bool) {
        return self.value == 0;
    }

    function get(Data memory self, uint256 defaultVote) internal pure returns(uint256) {
        if (self.value > 0) {
            return self.value - 1;
        }
        return defaultVote;
    }

    function get(Data memory self, function() external view returns(uint256) defaultVoteFn) internal view returns(uint256) {
        if (self.value > 0) {
            return self.value - 1;
        }
        return defaultVoteFn();
    }
}

// File: contracts/mocks/GovernanceModuleMock.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../modules/BaseGovernanceModule.sol";
import "../utils/BalanceAccounting.sol";


contract GovernanceModuleMock is BaseGovernanceModule, BalanceAccounting {
    // solhint-disable-next-line no-empty-blocks
    constructor(address _mothership) public BaseGovernanceModule(_mothership) {}

    function _notifyStakeChanged(address account, uint256 newBalance) internal override {
        _set(account, newBalance);
    }
}

// File: contracts/mocks/TokenMock.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";


contract TokenMock is ERC20, Ownable {
    // solhint-disable-next-line no-empty-blocks
    constructor(string memory name, string memory symbol) public ERC20(name, symbol) {}

    function mint(address account, uint256 amount) external onlyOwner {
        _mint(account, amount);
    }

    function burn(address account, uint256 amount) external onlyOwner {
        _burn(account, amount);
    }
}