// 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/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: @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: @openzeppelin/contracts/utils/Create2.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Helper to make usage of the `CREATE2` EVM opcode easier and safer.
 * `CREATE2` can be used to compute in advance the address where a smart
 * contract will be deployed, which allows for interesting new mechanisms known
 * as 'counterfactual interactions'.
 *
 * See the https://eips.ethereum.org/EIPS/eip-1014#motivation[EIP] for more
 * information.
 */
library Create2 {
    /**
     * @dev Deploys a contract using `CREATE2`. The address where the contract
     * will be deployed can be known in advance via {computeAddress}.
     *
     * The bytecode for a contract can be obtained from Solidity with
     * `type(contractName).creationCode`.
     *
     * Requirements:
     *
     * - `bytecode` must not be empty.
     * - `salt` must have not been used for `bytecode` already.
     * - the factory must have a balance of at least `amount`.
     * - if `amount` is non-zero, `bytecode` must have a `payable` constructor.
     */
    function deploy(uint256 amount, bytes32 salt, bytes memory bytecode) internal returns (address) {
        address addr;
        require(address(this).balance >= amount, "Create2: insufficient balance");
        require(bytecode.length != 0, "Create2: bytecode length is zero");
        // solhint-disable-next-line no-inline-assembly
        assembly {
            addr := create2(amount, add(bytecode, 0x20), mload(bytecode), salt)
        }
        require(addr != address(0), "Create2: Failed on deploy");
        return addr;
    }

    /**
     * @dev Returns the address where a contract will be stored if deployed via {deploy}. Any change in the
     * `bytecodeHash` or `salt` will result in a new destination address.
     */
    function computeAddress(bytes32 salt, bytes32 bytecodeHash) internal view returns (address) {
        return computeAddress(salt, bytecodeHash, address(this));
    }

    /**
     * @dev Returns the address where a contract will be stored if deployed via {deploy} from a contract located at
     * `deployer`. If `deployer` is this contract's address, returns the same value as {computeAddress}.
     */
    function computeAddress(bytes32 salt, bytes32 bytecodeHash, address deployer) internal pure returns (address) {
        bytes32 _data = keccak256(
            abi.encodePacked(bytes1(0xff), deployer, salt, bytecodeHash)
        );
        return address(uint160(uint256(_data)));
    }
}

// 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/GraphTokenLock.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;

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

import { Ownable as OwnableInitializable } from "./Ownable.sol";
import "./MathUtils.sol";
import "./IGraphTokenLock.sol";

/**
 * @title GraphTokenLock
 * @notice Contract that manages an unlocking schedule of tokens.
 * @dev The contract lock manage a number of tokens deposited into the contract to ensure that
 * they can only be released under certain time conditions.
 *
 * This contract implements a release scheduled based on periods and tokens are released in steps
 * after each period ends. It can be configured with one period in which case it is like a plain TimeLock.
 * It also supports revocation to be used for vesting schedules.
 *
 * The contract supports receiving extra funds than the managed tokens ones that can be
 * withdrawn by the beneficiary at any time.
 *
 * A releaseStartTime parameter is included to override the default release schedule and
 * perform the first release on the configured time. After that it will continue with the
 * default schedule.
 */
abstract contract GraphTokenLock is OwnableInitializable, IGraphTokenLock {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    uint256 private constant MIN_PERIOD = 1;

    // -- State --

    IERC20 public token;
    address public beneficiary;

    // Configuration

    // Amount of tokens managed by the contract schedule
    uint256 public managedAmount;

    uint256 public startTime; // Start datetime (in unixtimestamp)
    uint256 public endTime; // Datetime after all funds are fully vested/unlocked (in unixtimestamp)
    uint256 public periods; // Number of vesting/release periods

    // First release date for tokens (in unixtimestamp)
    // If set, no tokens will be released before releaseStartTime ignoring
    // the amount to release each period
    uint256 public releaseStartTime;
    // A cliff set a date to which a beneficiary needs to get to vest
    // all preceding periods
    uint256 public vestingCliffTime;
    Revocability public revocable; // Whether to use vesting for locked funds

    // State

    bool public isRevoked;
    bool public isInitialized;
    bool public isAccepted;
    uint256 public releasedAmount;
    uint256 public revokedAmount;

    // -- Events --

    event TokensReleased(address indexed beneficiary, uint256 amount);
    event TokensWithdrawn(address indexed beneficiary, uint256 amount);
    event TokensRevoked(address indexed beneficiary, uint256 amount);
    event BeneficiaryChanged(address newBeneficiary);
    event LockAccepted();
    event LockCanceled();

    /**
     * @dev Only allow calls from the beneficiary of the contract
     */
    modifier onlyBeneficiary() {
        require(msg.sender == beneficiary, "!auth");
        _;
    }

    /**
     * @notice Initializes the contract
     * @param _owner Address of the contract owner
     * @param _beneficiary Address of the beneficiary of locked tokens
     * @param _managedAmount Amount of tokens to be managed by the lock contract
     * @param _startTime Start time of the release schedule
     * @param _endTime End time of the release schedule
     * @param _periods Number of periods between start time and end time
     * @param _releaseStartTime Override time for when the releases start
     * @param _vestingCliffTime Override time for when the vesting start
     * @param _revocable Whether the contract is revocable
     */
    function _initialize(
        address _owner,
        address _beneficiary,
        address _token,
        uint256 _managedAmount,
        uint256 _startTime,
        uint256 _endTime,
        uint256 _periods,
        uint256 _releaseStartTime,
        uint256 _vestingCliffTime,
        Revocability _revocable
    ) internal {
        require(!isInitialized, "Already initialized");
        require(_owner != address(0), "Owner cannot be zero");
        require(_beneficiary != address(0), "Beneficiary cannot be zero");
        require(_token != address(0), "Token cannot be zero");
        require(_managedAmount > 0, "Managed tokens cannot be zero");
        require(_startTime != 0, "Start time must be set");
        require(_startTime < _endTime, "Start time > end time");
        require(_periods >= MIN_PERIOD, "Periods cannot be below minimum");
        require(_revocable != Revocability.NotSet, "Must set a revocability option");
        require(_releaseStartTime < _endTime, "Release start time must be before end time");
        require(_vestingCliffTime < _endTime, "Cliff time must be before end time");

        isInitialized = true;

        OwnableInitializable._initialize(_owner);
        beneficiary = _beneficiary;
        token = IERC20(_token);

        managedAmount = _managedAmount;

        startTime = _startTime;
        endTime = _endTime;
        periods = _periods;

        // Optionals
        releaseStartTime = _releaseStartTime;
        vestingCliffTime = _vestingCliffTime;
        revocable = _revocable;
    }

    /**
     * @notice Change the beneficiary of funds managed by the contract
     * @dev Can only be called by the beneficiary
     * @param _newBeneficiary Address of the new beneficiary address
     */
    function changeBeneficiary(address _newBeneficiary) external onlyBeneficiary {
        require(_newBeneficiary != address(0), "Empty beneficiary");
        beneficiary = _newBeneficiary;
        emit BeneficiaryChanged(_newBeneficiary);
    }

    /**
     * @notice Beneficiary accepts the lock, the owner cannot retrieve back the tokens
     * @dev Can only be called by the beneficiary
     */
    function acceptLock() external onlyBeneficiary {
        isAccepted = true;
        emit LockAccepted();
    }

    /**
     * @notice Owner cancel the lock and return the balance in the contract
     * @dev Can only be called by the owner
     */
    function cancelLock() external onlyOwner {
        require(isAccepted == false, "Cannot cancel accepted contract");

        token.safeTransfer(owner(), currentBalance());

        emit LockCanceled();
    }

    // -- Balances --

    /**
     * @notice Returns the amount of tokens currently held by the contract
     * @return Tokens held in the contract
     */
    function currentBalance() public view override returns (uint256) {
        return token.balanceOf(address(this));
    }

    // -- Time & Periods --

    /**
     * @notice Returns the current block timestamp
     * @return Current block timestamp
     */
    function currentTime() public view override returns (uint256) {
        return block.timestamp;
    }

    /**
     * @notice Gets duration of contract from start to end in seconds
     * @return Amount of seconds from contract startTime to endTime
     */
    function duration() public view override returns (uint256) {
        return endTime.sub(startTime);
    }

    /**
     * @notice Gets time elapsed since the start of the contract
     * @dev Returns zero if called before conctract starTime
     * @return Seconds elapsed from contract startTime
     */
    function sinceStartTime() public view override returns (uint256) {
        uint256 current = currentTime();
        if (current <= startTime) {
            return 0;
        }
        return current.sub(startTime);
    }

    /**
     * @notice Returns amount available to be released after each period according to schedule
     * @return Amount of tokens available after each period
     */
    function amountPerPeriod() public view override returns (uint256) {
        return managedAmount.div(periods);
    }

    /**
     * @notice Returns the duration of each period in seconds
     * @return Duration of each period in seconds
     */
    function periodDuration() public view override returns (uint256) {
        return duration().div(periods);
    }

    /**
     * @notice Gets the current period based on the schedule
     * @return A number that represents the current period
     */
    function currentPeriod() public view override returns (uint256) {
        return sinceStartTime().div(periodDuration()).add(MIN_PERIOD);
    }

    /**
     * @notice Gets the number of periods that passed since the first period
     * @return A number of periods that passed since the schedule started
     */
    function passedPeriods() public view override returns (uint256) {
        return currentPeriod().sub(MIN_PERIOD);
    }

    // -- Locking & Release Schedule --

    /**
     * @notice Gets the currently available token according to the schedule
     * @dev Implements the step-by-step schedule based on periods for available tokens
     * @return Amount of tokens available according to the schedule
     */
    function availableAmount() public view override returns (uint256) {
        uint256 current = currentTime();

        // Before contract start no funds are available
        if (current < startTime) {
            return 0;
        }

        // After contract ended all funds are available
        if (current > endTime) {
            return managedAmount;
        }

        // Get available amount based on period
        return passedPeriods().mul(amountPerPeriod());
    }

    /**
     * @notice Gets the amount of currently vested tokens
     * @dev Similar to available amount, but is fully vested when contract is non-revocable
     * @return Amount of tokens already vested
     */
    function vestedAmount() public view override returns (uint256) {
        // If non-revocable it is fully vested
        if (revocable == Revocability.Disabled) {
            return managedAmount;
        }

        // Vesting cliff is activated and it has not passed means nothing is vested yet
        if (vestingCliffTime > 0 && currentTime() < vestingCliffTime) {
            return 0;
        }

        return availableAmount();
    }

    /**
     * @notice Gets tokens currently available for release
     * @dev Considers the schedule and takes into account already released tokens
     * @return Amount of tokens ready to be released
     */
    function releasableAmount() public view virtual override returns (uint256) {
        // If a release start time is set no tokens are available for release before this date
        // If not set it follows the default schedule and tokens are available on
        // the first period passed
        if (releaseStartTime > 0 && currentTime() < releaseStartTime) {
            return 0;
        }

        // Vesting cliff is activated and it has not passed means nothing is vested yet
        // so funds cannot be released
        if (revocable == Revocability.Enabled && vestingCliffTime > 0 && currentTime() < vestingCliffTime) {
            return 0;
        }

        // A beneficiary can never have more releasable tokens than the contract balance
        uint256 releasable = availableAmount().sub(releasedAmount);
        return MathUtils.min(currentBalance(), releasable);
    }

    /**
     * @notice Gets the outstanding amount yet to be released based on the whole contract lifetime
     * @dev Does not consider schedule but just global amounts tracked
     * @return Amount of outstanding tokens for the lifetime of the contract
     */
    function totalOutstandingAmount() public view override returns (uint256) {
        return managedAmount.sub(releasedAmount).sub(revokedAmount);
    }

    /**
     * @notice Gets surplus amount in the contract based on outstanding amount to release
     * @dev All funds over outstanding amount is considered surplus that can be withdrawn by beneficiary.
     * Note this might not be the correct value for wallets transferred to L2 (i.e. an L2GraphTokenLockWallet), as the released amount will be
     * skewed, so the beneficiary might have to bridge back to L1 to release the surplus.
     * @return Amount of tokens considered as surplus
     */
    function surplusAmount() public view override returns (uint256) {
        uint256 balance = currentBalance();
        uint256 outstandingAmount = totalOutstandingAmount();
        if (balance > outstandingAmount) {
            return balance.sub(outstandingAmount);
        }
        return 0;
    }

    // -- Value Transfer --

    /**
     * @notice Releases tokens based on the configured schedule
     * @dev All available releasable tokens are transferred to beneficiary
     */
    function release() external override onlyBeneficiary {
        uint256 amountToRelease = releasableAmount();
        require(amountToRelease > 0, "No available releasable amount");

        releasedAmount = releasedAmount.add(amountToRelease);

        token.safeTransfer(beneficiary, amountToRelease);

        emit TokensReleased(beneficiary, amountToRelease);
    }

    /**
     * @notice Withdraws surplus, unmanaged tokens from the contract
     * @dev Tokens in the contract over outstanding amount are considered as surplus
     * @param _amount Amount of tokens to withdraw
     */
    function withdrawSurplus(uint256 _amount) external override onlyBeneficiary {
        require(_amount > 0, "Amount cannot be zero");
        require(surplusAmount() >= _amount, "Amount requested > surplus available");

        token.safeTransfer(beneficiary, _amount);

        emit TokensWithdrawn(beneficiary, _amount);
    }

    /**
     * @notice Revokes a vesting schedule and return the unvested tokens to the owner
     * @dev Vesting schedule is always calculated based on managed tokens
     */
    function revoke() external override onlyOwner {
        require(revocable == Revocability.Enabled, "Contract is non-revocable");
        require(isRevoked == false, "Already revoked");

        uint256 unvestedAmount = managedAmount.sub(vestedAmount());
        require(unvestedAmount > 0, "No available unvested amount");

        revokedAmount = unvestedAmount;
        isRevoked = true;

        token.safeTransfer(owner(), unvestedAmount);

        emit TokensRevoked(beneficiary, unvestedAmount);
    }
}

// File: contracts/GraphTokenLockManager.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/EnumerableSet.sol";
import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";

import "./MinimalProxyFactory.sol";
import "./IGraphTokenLockManager.sol";
import { GraphTokenLockWallet } from "./GraphTokenLockWallet.sol";

/**
 * @title GraphTokenLockManager
 * @notice This contract manages a list of authorized function calls and targets that can be called
 * by any TokenLockWallet contract and it is a factory of TokenLockWallet contracts.
 *
 * This contract receives funds to make the process of creating TokenLockWallet contracts
 * easier by distributing them the initial tokens to be managed.
 *
 * The owner can setup a list of token destinations that will be used by TokenLock contracts to
 * approve the pulling of funds, this way in can be guaranteed that only protocol contracts
 * will manipulate users funds.
 */
contract GraphTokenLockManager is Ownable, MinimalProxyFactory, IGraphTokenLockManager {
    using SafeERC20 for IERC20;
    using EnumerableSet for EnumerableSet.AddressSet;

    // -- State --

    mapping(bytes4 => address) public authFnCalls;
    EnumerableSet.AddressSet private _tokenDestinations;

    address public masterCopy;
    IERC20 internal _token;

    // -- Events --

    event MasterCopyUpdated(address indexed masterCopy);
    event TokenLockCreated(
        address indexed contractAddress,
        bytes32 indexed initHash,
        address indexed beneficiary,
        address token,
        uint256 managedAmount,
        uint256 startTime,
        uint256 endTime,
        uint256 periods,
        uint256 releaseStartTime,
        uint256 vestingCliffTime,
        IGraphTokenLock.Revocability revocable
    );

    event TokensDeposited(address indexed sender, uint256 amount);
    event TokensWithdrawn(address indexed sender, uint256 amount);

    event FunctionCallAuth(address indexed caller, bytes4 indexed sigHash, address indexed target, string signature);
    event TokenDestinationAllowed(address indexed dst, bool allowed);

    /**
     * Constructor.
     * @param _graphToken Token to use for deposits and withdrawals
     * @param _masterCopy Address of the master copy to use to clone proxies
     */
    constructor(IERC20 _graphToken, address _masterCopy) {
        require(address(_graphToken) != address(0), "Token cannot be zero");
        _token = _graphToken;
        setMasterCopy(_masterCopy);
    }

    // -- Factory --

    /**
     * @notice Sets the masterCopy bytecode to use to create clones of TokenLock contracts
     * @param _masterCopy Address of contract bytecode to factory clone
     */
    function setMasterCopy(address _masterCopy) public override onlyOwner {
        require(_masterCopy != address(0), "MasterCopy cannot be zero");
        masterCopy = _masterCopy;
        emit MasterCopyUpdated(_masterCopy);
    }

    /**
     * @notice Creates and fund a new token lock wallet using a minimum proxy
     * @param _owner Address of the contract owner
     * @param _beneficiary Address of the beneficiary of locked tokens
     * @param _managedAmount Amount of tokens to be managed by the lock contract
     * @param _startTime Start time of the release schedule
     * @param _endTime End time of the release schedule
     * @param _periods Number of periods between start time and end time
     * @param _releaseStartTime Override time for when the releases start
     * @param _revocable Whether the contract is revocable
     */
    function createTokenLockWallet(
        address _owner,
        address _beneficiary,
        uint256 _managedAmount,
        uint256 _startTime,
        uint256 _endTime,
        uint256 _periods,
        uint256 _releaseStartTime,
        uint256 _vestingCliffTime,
        IGraphTokenLock.Revocability _revocable
    ) external override onlyOwner {
        require(_token.balanceOf(address(this)) >= _managedAmount, "Not enough tokens to create lock");

        // Create contract using a minimal proxy and call initializer
        bytes memory initializer = abi.encodeWithSelector(
            GraphTokenLockWallet.initialize.selector,
            address(this),
            _owner,
            _beneficiary,
            address(_token),
            _managedAmount,
            _startTime,
            _endTime,
            _periods,
            _releaseStartTime,
            _vestingCliffTime,
            _revocable
        );
        address contractAddress = _deployProxy2(keccak256(initializer), masterCopy, initializer);

        // Send managed amount to the created contract
        _token.safeTransfer(contractAddress, _managedAmount);

        emit TokenLockCreated(
            contractAddress,
            keccak256(initializer),
            _beneficiary,
            address(_token),
            _managedAmount,
            _startTime,
            _endTime,
            _periods,
            _releaseStartTime,
            _vestingCliffTime,
            _revocable
        );
    }

    // -- Funds Management --

    /**
     * @notice Gets the GRT token address
     * @return Token used for transfers and approvals
     */
    function token() external view override returns (IERC20) {
        return _token;
    }

    /**
     * @notice Deposits tokens into the contract
     * @dev Even if the ERC20 token can be transferred directly to the contract
     * this function provide a safe interface to do the transfer and avoid mistakes
     * @param _amount Amount to deposit
     */
    function deposit(uint256 _amount) external override {
        require(_amount > 0, "Amount cannot be zero");
        _token.safeTransferFrom(msg.sender, address(this), _amount);
        emit TokensDeposited(msg.sender, _amount);
    }

    /**
     * @notice Withdraws tokens from the contract
     * @dev Escape hatch in case of mistakes or to recover remaining funds
     * @param _amount Amount of tokens to withdraw
     */
    function withdraw(uint256 _amount) external override onlyOwner {
        require(_amount > 0, "Amount cannot be zero");
        _token.safeTransfer(msg.sender, _amount);
        emit TokensWithdrawn(msg.sender, _amount);
    }

    // -- Token Destinations --

    /**
     * @notice Adds an address that can be allowed by a token lock to pull funds
     * @param _dst Destination address
     */
    function addTokenDestination(address _dst) external override onlyOwner {
        require(_dst != address(0), "Destination cannot be zero");
        require(_tokenDestinations.add(_dst), "Destination already added");
        emit TokenDestinationAllowed(_dst, true);
    }

    /**
     * @notice Removes an address that can be allowed by a token lock to pull funds
     * @param _dst Destination address
     */
    function removeTokenDestination(address _dst) external override onlyOwner {
        require(_tokenDestinations.remove(_dst), "Destination already removed");
        emit TokenDestinationAllowed(_dst, false);
    }

    /**
     * @notice Returns True if the address is authorized to be a destination of tokens
     * @param _dst Destination address
     * @return True if authorized
     */
    function isTokenDestination(address _dst) external view override returns (bool) {
        return _tokenDestinations.contains(_dst);
    }

    /**
     * @notice Returns an array of authorized destination addresses
     * @return Array of addresses authorized to pull funds from a token lock
     */
    function getTokenDestinations() external view override returns (address[] memory) {
        address[] memory dstList = new address[](_tokenDestinations.length());
        for (uint256 i = 0; i < _tokenDestinations.length(); i++) {
            dstList[i] = _tokenDestinations.at(i);
        }
        return dstList;
    }

    // -- Function Call Authorization --

    /**
     * @notice Sets an authorized function call to target
     * @dev Input expected is the function signature as 'transfer(address,uint256)'
     * @param _signature Function signature
     * @param _target Address of the destination contract to call
     */
    function setAuthFunctionCall(string calldata _signature, address _target) external override onlyOwner {
        _setAuthFunctionCall(_signature, _target);
    }

    /**
     * @notice Unsets an authorized function call to target
     * @dev Input expected is the function signature as 'transfer(address,uint256)'
     * @param _signature Function signature
     */
    function unsetAuthFunctionCall(string calldata _signature) external override onlyOwner {
        bytes4 sigHash = _toFunctionSigHash(_signature);
        authFnCalls[sigHash] = address(0);

        emit FunctionCallAuth(msg.sender, sigHash, address(0), _signature);
    }

    /**
     * @notice Sets an authorized function call to target in bulk
     * @dev Input expected is the function signature as 'transfer(address,uint256)'
     * @param _signatures Function signatures
     * @param _targets Address of the destination contract to call
     */
    function setAuthFunctionCallMany(
        string[] calldata _signatures,
        address[] calldata _targets
    ) external override onlyOwner {
        require(_signatures.length == _targets.length, "Array length mismatch");

        for (uint256 i = 0; i < _signatures.length; i++) {
            _setAuthFunctionCall(_signatures[i], _targets[i]);
        }
    }

    /**
     * @notice Sets an authorized function call to target
     * @dev Input expected is the function signature as 'transfer(address,uint256)'
     * @dev Function signatures of Graph Protocol contracts to be used are known ahead of time
     * @param _signature Function signature
     * @param _target Address of the destination contract to call
     */
    function _setAuthFunctionCall(string calldata _signature, address _target) internal {
        require(_target != address(this), "Target must be other contract");
        require(Address.isContract(_target), "Target must be a contract");

        bytes4 sigHash = _toFunctionSigHash(_signature);
        authFnCalls[sigHash] = _target;

        emit FunctionCallAuth(msg.sender, sigHash, _target, _signature);
    }

    /**
     * @notice Gets the target contract to call for a particular function signature
     * @param _sigHash Function signature hash
     * @return Address of the target contract where to send the call
     */
    function getAuthFunctionCallTarget(bytes4 _sigHash) public view override returns (address) {
        return authFnCalls[_sigHash];
    }

    /**
     * @notice Returns true if the function call is authorized
     * @param _sigHash Function signature hash
     * @return True if authorized
     */
    function isAuthFunctionCall(bytes4 _sigHash) external view override returns (bool) {
        return getAuthFunctionCallTarget(_sigHash) != address(0);
    }

    /**
     * @dev Converts a function signature string to 4-bytes hash
     * @param _signature Function signature string
     * @return Function signature hash
     */
    function _toFunctionSigHash(string calldata _signature) internal pure returns (bytes4) {
        return _convertToBytes4(abi.encodeWithSignature(_signature));
    }

    /**
     * @dev Converts function signature bytes to function signature hash (bytes4)
     * @param _signature Function signature
     * @return Function signature in bytes4
     */
    function _convertToBytes4(bytes memory _signature) internal pure returns (bytes4) {
        require(_signature.length == 4, "Invalid method signature");
        bytes4 sigHash;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sigHash := mload(add(_signature, 32))
        }
        return sigHash;
    }
}

// File: contracts/GraphTokenLockWallet.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;
pragma experimental ABIEncoderV2;

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

import "./GraphTokenLock.sol";
import "./IGraphTokenLockManager.sol";

/**
 * @title GraphTokenLockWallet
 * @notice This contract is built on top of the base GraphTokenLock functionality.
 * It allows wallet beneficiaries to use the deposited funds to perform specific function calls
 * on specific contracts.
 *
 * The idea is that supporters with locked tokens can participate in the protocol
 * but disallow any release before the vesting/lock schedule.
 * The beneficiary can issue authorized function calls to this contract that will
 * get forwarded to a target contract. A target contract is any of our protocol contracts.
 * The function calls allowed are queried to the GraphTokenLockManager, this way
 * the same configuration can be shared for all the created lock wallet contracts.
 *
 * NOTE: Contracts used as target must have its function signatures checked to avoid collisions
 * with any of this contract functions.
 * Beneficiaries need to approve the use of the tokens to the protocol contracts. For convenience
 * the maximum amount of tokens is authorized.
 * Function calls do not forward ETH value so DO NOT SEND ETH TO THIS CONTRACT.
 */
contract GraphTokenLockWallet is GraphTokenLock {
    using SafeMath for uint256;

    // -- State --

    IGraphTokenLockManager public manager;
    uint256 public usedAmount;

    // -- Events --

    event ManagerUpdated(address indexed _oldManager, address indexed _newManager);
    event TokenDestinationsApproved();
    event TokenDestinationsRevoked();

    // Initializer
    function initialize(
        address _manager,
        address _owner,
        address _beneficiary,
        address _token,
        uint256 _managedAmount,
        uint256 _startTime,
        uint256 _endTime,
        uint256 _periods,
        uint256 _releaseStartTime,
        uint256 _vestingCliffTime,
        Revocability _revocable
    ) external {
        _initialize(
            _owner,
            _beneficiary,
            _token,
            _managedAmount,
            _startTime,
            _endTime,
            _periods,
            _releaseStartTime,
            _vestingCliffTime,
            _revocable
        );
        _setManager(_manager);
    }

    // -- Admin --

    /**
     * @notice Sets a new manager for this contract
     * @param _newManager Address of the new manager
     */
    function setManager(address _newManager) external onlyOwner {
        _setManager(_newManager);
    }

    /**
     * @dev Sets a new manager for this contract
     * @param _newManager Address of the new manager
     */
    function _setManager(address _newManager) internal {
        require(_newManager != address(0), "Manager cannot be empty");
        require(Address.isContract(_newManager), "Manager must be a contract");

        address oldManager = address(manager);
        manager = IGraphTokenLockManager(_newManager);

        emit ManagerUpdated(oldManager, _newManager);
    }

    // -- Beneficiary --

    /**
     * @notice Approves protocol access of the tokens managed by this contract
     * @dev Approves all token destinations registered in the manager to pull tokens
     */
    function approveProtocol() external onlyBeneficiary {
        address[] memory dstList = manager.getTokenDestinations();
        for (uint256 i = 0; i < dstList.length; i++) {
            // Note this is only safe because we are using the max uint256 value
            token.approve(dstList[i], type(uint256).max);
        }
        emit TokenDestinationsApproved();
    }

    /**
     * @notice Revokes protocol access of the tokens managed by this contract
     * @dev Revokes approval to all token destinations in the manager to pull tokens
     */
    function revokeProtocol() external onlyBeneficiary {
        address[] memory dstList = manager.getTokenDestinations();
        for (uint256 i = 0; i < dstList.length; i++) {
            // Note this is only safe cause we're using 0 as the amount
            token.approve(dstList[i], 0);
        }
        emit TokenDestinationsRevoked();
    }

    /**
     * @notice Gets tokens currently available for release
     * @dev Considers the schedule, takes into account already released tokens and used amount
     * @return Amount of tokens ready to be released
     */
    function releasableAmount() public view override returns (uint256) {
        if (revocable == Revocability.Disabled) {
            return super.releasableAmount();
        }

        // -- Revocability enabled logic
        // This needs to deal with additional considerations for when tokens are used in the protocol

        // If a release start time is set no tokens are available for release before this date
        // If not set it follows the default schedule and tokens are available on
        // the first period passed
        if (releaseStartTime > 0 && currentTime() < releaseStartTime) {
            return 0;
        }

        // Vesting cliff is activated and it has not passed means nothing is vested yet
        // so funds cannot be released
        if (revocable == Revocability.Enabled && vestingCliffTime > 0 && currentTime() < vestingCliffTime) {
            return 0;
        }

        // A beneficiary can never have more releasable tokens than the contract balance
        // We consider the `usedAmount` in the protocol as part of the calculations
        // the beneficiary should not release funds that are used.
        uint256 releasable = availableAmount().sub(releasedAmount).sub(usedAmount);
        return MathUtils.min(currentBalance(), releasable);
    }

    /**
     * @notice Forward authorized contract calls to protocol contracts
     * @dev Fallback function can be called by the beneficiary only if function call is allowed
     */
    // solhint-disable-next-line no-complex-fallback
    fallback() external payable {
        // Only beneficiary can forward calls
        require(msg.sender == beneficiary, "Unauthorized caller");
        require(msg.value == 0, "ETH transfers not supported");

        // Function call validation
        address _target = manager.getAuthFunctionCallTarget(msg.sig);
        require(_target != address(0), "Unauthorized function");

        uint256 oldBalance = currentBalance();

        // Call function with data
        Address.functionCall(_target, msg.data);

        // Tracked used tokens in the protocol
        // We do this check after balances were updated by the forwarded call
        // Check is only enforced for revocable contracts to save some gas
        if (revocable == Revocability.Enabled) {
            // Track contract balance change
            uint256 newBalance = currentBalance();
            if (newBalance < oldBalance) {
                // Outflow
                uint256 diff = oldBalance.sub(newBalance);
                usedAmount = usedAmount.add(diff);
            } else {
                // Inflow: We can receive profits from the protocol, that could make usedAmount to
                // underflow. We set it to zero in that case.
                uint256 diff = newBalance.sub(oldBalance);
                usedAmount = (diff >= usedAmount) ? 0 : usedAmount.sub(diff);
            }
            require(usedAmount <= vestedAmount(), "Cannot use more tokens than vested amount");
        }
    }

    /**
     * @notice Receive function that always reverts.
     * @dev Only included to supress warnings, see https://github.com/ethereum/solidity/issues/10159
     */
    receive() external payable {
        revert("Bad call");
    }
}

// File: contracts/IGraphTokenLock.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;
pragma experimental ABIEncoderV2;

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

interface IGraphTokenLock {
    enum Revocability {
        NotSet,
        Enabled,
        Disabled
    }

    // -- Balances --

    function currentBalance() external view returns (uint256);

    // -- Time & Periods --

    function currentTime() external view returns (uint256);

    function duration() external view returns (uint256);

    function sinceStartTime() external view returns (uint256);

    function amountPerPeriod() external view returns (uint256);

    function periodDuration() external view returns (uint256);

    function currentPeriod() external view returns (uint256);

    function passedPeriods() external view returns (uint256);

    // -- Locking & Release Schedule --

    function availableAmount() external view returns (uint256);

    function vestedAmount() external view returns (uint256);

    function releasableAmount() external view returns (uint256);

    function totalOutstandingAmount() external view returns (uint256);

    function surplusAmount() external view returns (uint256);

    // -- Value Transfer --

    function release() external;

    function withdrawSurplus(uint256 _amount) external;

    function revoke() external;
}

// File: contracts/IGraphTokenLockManager.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;
pragma experimental ABIEncoderV2;

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

import "./IGraphTokenLock.sol";

interface IGraphTokenLockManager {
    // -- Factory --

    function setMasterCopy(address _masterCopy) external;

    function createTokenLockWallet(
        address _owner,
        address _beneficiary,
        uint256 _managedAmount,
        uint256 _startTime,
        uint256 _endTime,
        uint256 _periods,
        uint256 _releaseStartTime,
        uint256 _vestingCliffTime,
        IGraphTokenLock.Revocability _revocable
    ) external;

    // -- Funds Management --

    function token() external returns (IERC20);

    function deposit(uint256 _amount) external;

    function withdraw(uint256 _amount) external;

    // -- Allowed Funds Destinations --

    function addTokenDestination(address _dst) external;

    function removeTokenDestination(address _dst) external;

    function isTokenDestination(address _dst) external view returns (bool);

    function getTokenDestinations() external view returns (address[] memory);

    // -- Function Call Authorization --

    function setAuthFunctionCall(string calldata _signature, address _target) external;

    function unsetAuthFunctionCall(string calldata _signature) external;

    function setAuthFunctionCallMany(string[] calldata _signatures, address[] calldata _targets) external;

    function getAuthFunctionCallTarget(bytes4 _sigHash) external view returns (address);

    function isAuthFunctionCall(bytes4 _sigHash) external view returns (bool);
}

// File: contracts/MathUtils.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;

library MathUtils {
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
}

// File: contracts/MinimalProxyFactory.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;

import { Address } from "@openzeppelin/contracts/utils/Address.sol";
import { Create2 } from "@openzeppelin/contracts/utils/Create2.sol";

/**
 * @title MinimalProxyFactory: a factory contract for creating minimal proxies
 * @notice Adapted from https://github.com/OpenZeppelin/openzeppelin-sdk/blob/v2.5.0/packages/lib/contracts/upgradeability/ProxyFactory.sol
 * Based on https://eips.ethereum.org/EIPS/eip-1167
 */
contract MinimalProxyFactory {
    /// @dev Emitted when a new proxy is created
    event ProxyCreated(address indexed proxy);

    /**
     * @notice Gets the deterministic CREATE2 address for MinimalProxy with a particular implementation
     * @param _salt Bytes32 salt to use for CREATE2
     * @param _implementation Address of the proxy target implementation
     * @param _deployer Address of the deployer that creates the contract
     * @return Address of the counterfactual MinimalProxy
     */
    function getDeploymentAddress(
        bytes32 _salt,
        address _implementation,
        address _deployer
    ) public pure returns (address) {
        return Create2.computeAddress(_salt, keccak256(_getContractCreationCode(_implementation)), _deployer);
    }

    /**
     * @dev Deploys a MinimalProxy with CREATE2
     * @param _salt Bytes32 salt to use for CREATE2
     * @param _implementation Address of the proxy target implementation
     * @param _data Bytes with the initializer call
     * @return Address of the deployed MinimalProxy
     */
    function _deployProxy2(bytes32 _salt, address _implementation, bytes memory _data) internal returns (address) {
        address proxyAddress = Create2.deploy(0, _salt, _getContractCreationCode(_implementation));

        emit ProxyCreated(proxyAddress);

        // Call function with data
        if (_data.length > 0) {
            Address.functionCall(proxyAddress, _data);
        }

        return proxyAddress;
    }

    /**
     * @dev Gets the MinimalProxy bytecode
     * @param _implementation Address of the proxy target implementation
     * @return MinimalProxy bytecode
     */
    function _getContractCreationCode(address _implementation) internal pure returns (bytes memory) {
        bytes10 creation = 0x3d602d80600a3d3981f3;
        bytes10 prefix = 0x363d3d373d3d3d363d73;
        bytes20 targetBytes = bytes20(_implementation);
        bytes15 suffix = 0x5af43d82803e903d91602b57fd5bf3;
        return abi.encodePacked(creation, prefix, targetBytes, suffix);
    }
}

// File: contracts/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;

/**
 * @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.
 *
 * The owner account will be passed on initialization of 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.
 */
contract Ownable {
    /// @dev Owner of the contract, can be retrieved with the public owner() function
    address private _owner;
    /// @dev Since upgradeable contracts might inherit this, we add a storage gap
    /// to allow adding variables here without breaking the proxy storage layout
    uint256[50] private __gap;

    /// @dev Emitted when ownership of the contract is transferred
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function _initialize(address owner) internal {
        _owner = owner;
        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(_owner == msg.sender, "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() external 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) external virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}