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



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../GSN/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.
 */
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 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/GSN/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/*
 * @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/math/Math.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @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/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @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, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

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

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

        return c;
    }

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

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

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

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

        return c;
    }

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

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

// File: @openzeppelin/contracts/proxy/Initializable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.4.24 <0.7.0;


/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 * 
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {UpgradeableProxy-constructor}.
 * 
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {

    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(_initializing || _isConstructor() || !_initialized, "Initializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    /// @dev Returns true if and only if the function is running in the constructor
    function _isConstructor() private view returns (bool) {
        // extcodesize checks the size of the code stored in an address, and
        // address returns the current address. Since the code is still not
        // deployed when running a constructor, any checks on its code size will
        // yield zero, making it an effective way to detect if a contract is
        // under construction or not.
        address self = address(this);
        uint256 cs;
        // solhint-disable-next-line no-inline-assembly
        assembly { cs := extcodesize(self) }
        return cs == 0;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../../GSN/Context.sol";
import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.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;
    using Address for address;

    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 returns (string memory) {
        return _name;
    }

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

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. 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 returns (uint8) {
        return _decimals;
    }

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

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view 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 {
        _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: @openzeppelin/contracts/token/ERC20/ERC20Burnable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../../GSN/Context.sol";
import "./ERC20.sol";

/**
 * @dev Extension of {ERC20} that allows token holders to destroy both their own
 * tokens and those that they have an allowance for, in a way that can be
 * recognized off-chain (via event analysis).
 */
abstract contract ERC20Burnable is Context, ERC20 {
    /**
     * @dev Destroys `amount` tokens from the caller.
     *
     * See {ERC20-_burn}.
     */
    function burn(uint256 amount) public virtual {
        _burn(_msgSender(), amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, deducting from the caller's
     * allowance.
     *
     * See {ERC20-_burn} and {ERC20-allowance}.
     *
     * Requirements:
     *
     * - the caller must have allowance for ``accounts``'s tokens of at least
     * `amount`.
     */
    function burnFrom(address account, uint256 amount) public virtual {
        uint256 decreasedAllowance = allowance(account, _msgSender()).sub(amount, "ERC20: burn amount exceeds allowance");

        _approve(account, _msgSender(), decreasedAllowance);
        _burn(account, amount);
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @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;

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;

/**
 * @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 in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

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

    /**
     * @dev 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");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../GSN/Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor () internal {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!_paused, "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(_paused, "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// File: contracts/interfaces/ENS.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;


interface IENS {
    function owner(bytes32 node) external view returns (address);
}
// File: contracts/interfaces/FeeManager.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

import { ITornadoInstance } from "./TornadoInstance.sol";

interface IFeeManager {
    function instanceFeeWithUpdate(
        ITornadoInstance _instance
    ) external returns (uint160);
}

// File: contracts/interfaces/TornadoInstance.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

interface ITornadoInstance {
    function token() external view returns (address);

    function denomination() external view returns (uint256);

    function deposit(bytes32 commitment) external payable;

    function withdraw(
        bytes calldata proof,
        bytes32 root,
        bytes32 nullifierHash,
        address payable recipient,
        address payable relayer,
        uint256 fee,
        uint256 refund
    ) external payable;
}

// File: contracts/interfaces/TornadoStakingRewards.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

interface ITornadoStakingRewards {
    function addBurnRewards(uint256 amount) external;
}

// File: contracts/libraries/EnsNamehash.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

/*
 * @dev Solidity implementation of the ENS namehash algorithm.
 *
 * Warning! Does not normalize or validate names before hashing.
 * Original version can be found here https://github.com/JonahGroendal/ens-namehash/
 */
library ENSNamehash {
    function namehash(bytes memory domain) internal pure returns (bytes32) {
        return namehash(domain, 0);
    }

    function namehash(bytes memory domain, uint256 i) internal pure returns (bytes32) {
        if (domain.length <= i) return 0x0000000000000000000000000000000000000000000000000000000000000000;

        uint256 len = labelLength(domain, i);

        return keccak256(abi.encodePacked(namehash(domain, i + len + 1), keccak(domain, i, len)));
    }

    function labelLength(bytes memory domain, uint256 i) private pure returns (uint256) {
        uint256 len;
        while (i + len != domain.length && domain[i + len] != 0x2e) {
            len++;
        }
        return len;
    }

    function keccak(bytes memory data, uint256 offset, uint256 len) private pure returns (bytes32 ret) {
        require(offset + len <= data.length);
        assembly {
            ret := keccak256(add(add(data, 32), offset), len)
        }
    }
}
// File: contracts/RelayerRegistry.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;
pragma experimental ABIEncoderV2;

import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { Initializable } from "@openzeppelin/contracts/proxy/Initializable.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import { EnsResolve } from "torn-token/contracts/ENS.sol";
import { TORN } from "torn-token/contracts/TORN.sol";
import { IENS } from "./interfaces/ENS.sol";
import { IFeeManager } from "./interfaces/FeeManager.sol";
import { ITornadoInstance } from "./interfaces/TornadoInstance.sol";
import { ITornadoStakingRewards } from "./interfaces/TornadoStakingRewards.sol";
import { ENSNamehash } from "./libraries/EnsNamehash.sol";

struct RelayerState {
    uint256 balance;
    bytes32 ensHash;
}

/**
 * @notice Registry contract, one of the main contracts of this protocol upgrade.
 *         The contract should store relayers' addresses and data attributed to the
 *         master address of the relayer. This data includes the relayers stake and
 *         his ensHash.
 *         A relayers master address has a number of subaddresses called "workers",
 *         these are all addresses which burn stake in communication with the proxy.
 *         If a relayer is not registered, he is not displayed on the frontend.
 * @dev CONTRACT RISKS:
 *      - if setter functions are compromised, relayer metadata would be at risk, including the noted amount of his balance
 *      - if burn function is compromised, relayers run the risk of being unable to handle withdrawals
 *      - the above risk also applies to the nullify balance function
 *
 */
contract RelayerRegistry is Initializable, EnsResolve {
    using SafeMath for uint256;
    using SafeERC20 for TORN;
    using ENSNamehash for bytes;

    TORN public immutable torn;
    address public immutable governance;
    IENS public immutable ens;
    ITornadoStakingRewards public immutable staking;
    IFeeManager public immutable feeManager;

    address public tornadoRouter;
    uint256 public minStakeAmount;

    mapping(address => RelayerState) public relayers;
    mapping(address => address) public workers;

    event RelayerBalanceNullified(address relayer);
    event WorkerRegistered(address relayer, address worker);
    event WorkerUnregistered(address relayer, address worker);
    event StakeAddedToRelayer(address relayer, uint256 amountStakeAdded);
    event StakeBurned(address relayer, uint256 amountBurned);
    event MinimumStakeAmount(uint256 minStakeAmount);
    event RouterRegistered(address tornadoRouter);
    event RelayerRegistered(bytes32 relayer, string ensName, address relayerAddress, uint256 stakedAmount);
    event RelayerUnregistered(address relayer);

    modifier onlyGovernance() {
        require(msg.sender == governance, "only governance");
        _;
    }

    modifier onlyTornadoRouter() {
        require(msg.sender == tornadoRouter, "only proxy");
        _;
    }

    modifier onlyRelayer(address sender, address relayer) {
        require(workers[sender] == relayer, "only relayer");
        _;
    }

    constructor(address _torn, address _governance, address _ens, address _staking, address _feeManager) public {
        torn = TORN(_torn);
        governance = _governance;
        ens = IENS(_ens);
        staking = ITornadoStakingRewards(_staking);
        feeManager = IFeeManager(_feeManager);
    }

    /**
     * @notice initialize function for upgradeability
     * @dev this contract will be deployed behind a proxy and should not assign values at logic address,
     *      params left out because self explainable
     *
     */
    function initialize(bytes32 _tornadoRouter) external initializer {
        tornadoRouter = resolve(_tornadoRouter);
    }

    /**
     * @notice This function should register a master address and optionally a set of workeres for a relayer + metadata
     * @dev Relayer can't steal other relayers workers since they are registered, and a wallet (msg.sender check) can always unregister itself
     * @param ensName ens name of the relayer
     * @param stake the initial amount of stake in TORN the relayer is depositing
     *
     */
    function register(string calldata ensName, uint256 stake, address[] calldata workersToRegister) external {
        _register(msg.sender, ensName, stake, workersToRegister);
    }

    /**
     * @dev Register function equivalent with permit-approval instead of regular approve.
     *
     */
    function registerPermit(
        string calldata ensName,
        uint256 stake,
        address[] calldata workersToRegister,
        address relayer,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        torn.permit(relayer, address(this), stake, deadline, v, r, s);
        _register(relayer, ensName, stake, workersToRegister);
    }

    function _register(
        address relayer,
        string calldata ensName,
        uint256 stake,
        address[] calldata workersToRegister
    ) internal {
        bytes32 ensHash = bytes(ensName).namehash();
        address domainOwner = ens.owner(ensHash);
        address ensNameWrapper = 0xD4416b13d2b3a9aBae7AcD5D6C2BbDBE25686401;

        require(domainOwner != ensNameWrapper, "only unwrapped ens domains");
        require(relayer == domainOwner, "only ens domain owner");
        require(workers[relayer] == address(0), "cant register again");
        RelayerState storage metadata = relayers[relayer];

        require(metadata.ensHash == bytes32(0), "registered already");
        require(stake >= minStakeAmount, "!min_stake");

        torn.safeTransferFrom(relayer, address(staking), stake);
        emit StakeAddedToRelayer(relayer, stake);

        metadata.balance = stake;
        metadata.ensHash = ensHash;
        workers[relayer] = relayer;

        for (uint256 i = 0; i < workersToRegister.length; i++) {
            address worker = workersToRegister[i];
            _registerWorker(relayer, worker);
        }

        emit RelayerRegistered(ensHash, ensName, relayer, stake);
    }

    /**
     * @notice This function should allow relayers to register more workeres
     * @param relayer Relayer which should send message from any worker which is already registered
     * @param worker Address to register
     *
     */
    function registerWorker(address relayer, address worker) external onlyRelayer(msg.sender, relayer) {
        _registerWorker(relayer, worker);
    }

    function _registerWorker(address relayer, address worker) internal {
        require(workers[worker] == address(0), "can't steal an address");
        workers[worker] = relayer;
        emit WorkerRegistered(relayer, worker);
    }

    /**
     * @notice This function should allow anybody to unregister an address they own
     * @dev designed this way as to allow someone to unregister themselves in case a relayer misbehaves
     *      - this should be followed by an action like burning relayer stake
     *      - there was an option of allowing the sender to burn relayer stake in case of malicious behaviour, this feature was not included in the end
     *      - reverts if trying to unregister master, otherwise contract would break. in general, there should be no reason to unregister master at all
     *
     */
    function unregisterWorker(address worker) external {
        if (worker != msg.sender) require(workers[worker] == msg.sender, "only owner of worker");
        require(workers[worker] != worker, "cant unregister master");
        emit WorkerUnregistered(workers[worker], worker);
        workers[worker] = address(0);
    }

    /**
     * @notice This function should allow governance to unregister relayer
     * @param relayer Address of the relayer
     *
     */
    function unregisterRelayer(address relayer) external onlyGovernance {
        nullifyBalance(relayer);
        delete relayers[relayer];
        delete workers[relayer];
        emit RelayerUnregistered(relayer);
    }

    /**
     * @notice This function should allow anybody to stake to a relayer more TORN
     * @param relayer Relayer main address to stake to
     * @param stake Stake to be added to relayer
     *
     */
    function stakeToRelayer(address relayer, uint256 stake) external {
        _stakeToRelayer(msg.sender, relayer, stake);
    }

    /**
     * @dev stakeToRelayer function equivalent with permit-approval instead of regular approve.
     * @param staker address from that stake is paid
     *
     */
    function stakeToRelayerPermit(
        address relayer,
        uint256 stake,
        address staker,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        torn.permit(staker, address(this), stake, deadline, v, r, s);
        _stakeToRelayer(staker, relayer, stake);
    }

    function _stakeToRelayer(address staker, address relayer, uint256 stake) internal {
        require(workers[relayer] == relayer, "!registered");
        torn.safeTransferFrom(staker, address(staking), stake);
        relayers[relayer].balance = stake.add(relayers[relayer].balance);
        emit StakeAddedToRelayer(relayer, stake);
    }

    /**
     * @notice This function should burn some relayer stake on withdraw and notify staking of this
     * @dev IMPORTANT FUNCTION:
     *      - This should be only called by the tornado proxy
     *      - Should revert if relayer does not call proxy from valid worker
     *      - Should not overflow
     *      - Should underflow and revert (SafeMath) on not enough stake (balance)
     * @param sender worker to check sender == relayer
     * @param relayer address of relayer who's stake is being burned
     * @param pool instance to get fee for
     *
     */
    function burn(address sender, address relayer, ITornadoInstance pool) external onlyTornadoRouter {
        address masterAddress = workers[sender];
        if (masterAddress == address(0)) {
            require(workers[relayer] == address(0), "Only custom relayer");
            return;
        }

        require(masterAddress == relayer, "only relayer");
        uint256 toBurn = feeManager.instanceFeeWithUpdate(pool);
        relayers[relayer].balance = relayers[relayer].balance.sub(toBurn);
        staking.addBurnRewards(toBurn);
        emit StakeBurned(relayer, toBurn);
    }

    /**
     * @notice This function should allow governance to set the minimum stake amount
     * @param minAmount new minimum stake amount
     *
     */
    function setMinStakeAmount(uint256 minAmount) external onlyGovernance {
        minStakeAmount = minAmount;
        emit MinimumStakeAmount(minAmount);
    }

    /**
     * @notice This function should allow governance to set a new tornado proxy address
     * @param tornadoRouterAddress address of the new proxy
     *
     */
    function setTornadoRouter(address tornadoRouterAddress) external onlyGovernance {
        tornadoRouter = tornadoRouterAddress;
        emit RouterRegistered(tornadoRouterAddress);
    }

    /**
     * @notice This function should allow governance to nullify a relayers balance
     * @dev IMPORTANT FUNCTION:
     *      - Should nullify the balance
     *      - Adding nullified balance as rewards was refactored to allow for the flexibility of these funds (for gov to operate with them)
     * @param relayer address of relayer who's balance is to nullify
     *
     */
    function nullifyBalance(address relayer) public onlyGovernance {
        address masterAddress = workers[relayer];
        require(relayer == masterAddress, "must be master");
        relayers[masterAddress].balance = 0;
        emit RelayerBalanceNullified(relayer);
    }

    /**
     * @notice This function should check if a worker is associated with a relayer
     * @param toResolve address to check
     * @return true if is associated
     *
     */
    function isRelayer(address toResolve) external view returns (bool) {
        return workers[toResolve] != address(0);
    }

    /**
     * @notice This function should check if a worker is registered to the relayer stated
     * @param relayer relayer to check
     * @param toResolve address to check
     * @return true if registered
     *
     */
    function isRelayerRegistered(address relayer, address toResolve) external view returns (bool) {
        return workers[toResolve] == relayer;
    }

    /**
     * @notice This function should get a relayers ensHash
     * @param relayer address to fetch for
     * @return relayer's ensHash
     *
     */
    function getRelayerEnsHash(address relayer) external view returns (bytes32) {
        return relayers[workers[relayer]].ensHash;
    }

    /**
     * @notice This function should get a relayers balance
     * @param relayer relayer who's balance is to fetch
     * @return relayer's balance
     *
     */
    function getRelayerBalance(address relayer) external view returns (uint256) {
        return relayers[workers[relayer]].balance;
    }
}

// File: torn-token/contracts/ECDSA.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

// A copy from https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237/files

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
  /**
   * @dev Returns the address that signed a hashed message (`hash`) with
   * `signature`. This address can then be used for verification purposes.
   *
   * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
   * this function rejects them by requiring the `s` value to be in the lower
   * half order, and the `v` value to be either 27 or 28.
   *
   * IMPORTANT: `hash` _must_ be the result of a hash operation for the
   * verification to be secure: it is possible to craft signatures that
   * recover to arbitrary addresses for non-hashed data. A safe way to ensure
   * this is by receiving a hash of the original message (which may otherwise
   * be too long), and then calling {toEthSignedMessageHash} on it.
   */
  function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
    // Check the signature length
    if (signature.length != 65) {
      revert("ECDSA: invalid signature length");
    }

    // Divide the signature in r, s and v variables
    bytes32 r;
    bytes32 s;
    uint8 v;

    // ecrecover takes the signature parameters, and the only way to get them
    // currently is to use assembly.
    // solhint-disable-next-line no-inline-assembly
    assembly {
      r := mload(add(signature, 0x20))
      s := mload(add(signature, 0x40))
      v := mload(add(signature, 0x41))
    }

    return recover(hash, v, r, s);
  }

  /**
   * @dev Overload of {ECDSA-recover-bytes32-bytes-} that receives the `v`,
   * `r` and `s` signature fields separately.
   */
  function recover(
    bytes32 hash,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) internal pure returns (address) {
    // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
    // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
    // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
    // signatures from current libraries generate a unique signature with an s-value in the lower half order.
    //
    // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
    // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
    // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
    // these malleable signatures as well.
    require(uint256(s) <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, "ECDSA: invalid signature 's' value");
    require(v == 27 || v == 28, "ECDSA: invalid signature 'v' value");

    // If the signature is valid (and not malleable), return the signer address
    address signer = ecrecover(hash, v, r, s);
    require(signer != address(0), "ECDSA: invalid signature");

    return signer;
  }

  /**
   * @dev Returns an Ethereum Signed Message, created from a `hash`. This
   * replicates the behavior of the
   * https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign[`eth_sign`]
   * JSON-RPC method.
   *
   * See {recover}.
   */
  function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
    // 32 is the length in bytes of hash,
    // enforced by the type signature above
    return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
  }
}

// File: torn-token/contracts/ENS.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

interface ENS {
  function resolver(bytes32 node) external view returns (Resolver);
}

interface Resolver {
  function addr(bytes32 node) external view returns (address);
}

contract EnsResolve {
  function resolve(bytes32 node) public view virtual returns (address) {
    ENS Registry = ENS(
      getChainId() == 1 ? 0x00000000000C2E074eC69A0dFb2997BA6C7d2e1e : 0x8595bFb0D940DfEDC98943FA8a907091203f25EE
    );
    return Registry.resolver(node).addr(node);
  }

  function bulkResolve(bytes32[] memory domains) public view returns (address[] memory result) {
    result = new address[](domains.length);
    for (uint256 i = 0; i < domains.length; i++) {
      result[i] = resolve(domains[i]);
    }
  }

  function getChainId() internal pure returns (uint256) {
    uint256 chainId;
    assembly {
      chainId := chainid()
    }
    return chainId;
  }
}

// File: torn-token/contracts/ERC20Permit.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

// Adapted copy from https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237/files

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

/**
 * @dev Extension of {ERC20} that allows token holders to use their tokens
 * without sending any transactions by setting {IERC20-allowance} with a
 * signature using the {permit} method, and then spend them via
 * {IERC20-transferFrom}.
 *
 * The {permit} signature mechanism conforms to the {IERC2612Permit} interface.
 */
abstract contract ERC20Permit is ERC20 {
  mapping(address => uint256) private _nonces;

  bytes32 private constant _PERMIT_TYPEHASH = keccak256(
    "Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
  );

  // Mapping of ChainID to domain separators. This is a very gas efficient way
  // to not recalculate the domain separator on every call, while still
  // automatically detecting ChainID changes.
  mapping(uint256 => bytes32) private _domainSeparators;

  constructor() internal {
    _updateDomainSeparator();
  }

  /**
   * @dev See {IERC2612Permit-permit}.
   *
   * If https://eips.ethereum.org/EIPS/eip-1344[ChainID] ever changes, the
   * EIP712 Domain Separator is automatically recalculated.
   */
  function permit(
    address owner,
    address spender,
    uint256 amount,
    uint256 deadline,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) public {
    require(blockTimestamp() <= deadline, "ERC20Permit: expired deadline");

    bytes32 hashStruct = keccak256(abi.encode(_PERMIT_TYPEHASH, owner, spender, amount, _nonces[owner], deadline));

    bytes32 hash = keccak256(abi.encodePacked(uint16(0x1901), _domainSeparator(), hashStruct));

    address signer = ECDSA.recover(hash, v, r, s);
    require(signer == owner, "ERC20Permit: invalid signature");

    _nonces[owner]++;
    _approve(owner, spender, amount);
  }

  /**
   * @dev See {IERC2612Permit-nonces}.
   */
  function nonces(address owner) public view returns (uint256) {
    return _nonces[owner];
  }

  function _updateDomainSeparator() private returns (bytes32) {
    uint256 _chainID = chainID();

    bytes32 newDomainSeparator = keccak256(
      abi.encode(
        keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
        keccak256(bytes(name())),
        keccak256(bytes("1")), // Version
        _chainID,
        address(this)
      )
    );

    _domainSeparators[_chainID] = newDomainSeparator;

    return newDomainSeparator;
  }

  // Returns the domain separator, updating it if chainID changes
  function _domainSeparator() private returns (bytes32) {
    bytes32 domainSeparator = _domainSeparators[chainID()];
    if (domainSeparator != 0x00) {
      return domainSeparator;
    } else {
      return _updateDomainSeparator();
    }
  }

  function chainID() public view virtual returns (uint256 _chainID) {
    assembly {
      _chainID := chainid()
    }
  }

  function blockTimestamp() public view virtual returns (uint256) {
    return block.timestamp;
  }
}

// File: torn-token/contracts/TORN.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Burnable.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Pausable.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "./ERC20Permit.sol";
import "./ENS.sol";

contract TORN is ERC20("TornadoCash", "TORN"), ERC20Burnable, ERC20Permit, Pausable, EnsResolve {
  using SafeERC20 for IERC20;

  uint256 public immutable canUnpauseAfter;
  address public immutable governance;
  mapping(address => bool) public allowedTransferee;

  event Allowed(address target);
  event Disallowed(address target);

  struct Recipient {
    bytes32 to;
    uint256 amount;
  }

  constructor(
    bytes32 _governance,
    uint256 _pausePeriod,
    Recipient[] memory _vestings
  ) public {
    address _resolvedGovernance = resolve(_governance);
    governance = _resolvedGovernance;
    allowedTransferee[_resolvedGovernance] = true;

    for (uint256 i = 0; i < _vestings.length; i++) {
      address to = resolve(_vestings[i].to);
      _mint(to, _vestings[i].amount);
      allowedTransferee[to] = true;
    }

    canUnpauseAfter = blockTimestamp().add(_pausePeriod);
    _pause();
    require(totalSupply() == 10000000 ether, "TORN: incorrect distribution");
  }

  modifier onlyGovernance() {
    require(_msgSender() == governance, "TORN: only governance can perform this action");
    _;
  }

  function changeTransferability(bool decision) public onlyGovernance {
    require(blockTimestamp() > canUnpauseAfter, "TORN: cannot change transferability yet");
    if (decision) {
      _unpause();
    } else {
      _pause();
    }
  }

  function addToAllowedList(address[] memory target) public onlyGovernance {
    for (uint256 i = 0; i < target.length; i++) {
      allowedTransferee[target[i]] = true;
      emit Allowed(target[i]);
    }
  }

  function removeFromAllowedList(address[] memory target) public onlyGovernance {
    for (uint256 i = 0; i < target.length; i++) {
      allowedTransferee[target[i]] = false;
      emit Disallowed(target[i]);
    }
  }

  function _beforeTokenTransfer(
    address from,
    address to,
    uint256 amount
  ) internal override {
    super._beforeTokenTransfer(from, to, amount);
    require(!paused() || allowedTransferee[from] || allowedTransferee[to], "TORN: paused");
    require(to != address(this), "TORN: invalid recipient");
  }

  /// @dev Method to claim junk and accidentally sent tokens
  function rescueTokens(
    IERC20 _token,
    address payable _to,
    uint256 _balance
  ) external onlyGovernance {
    require(_to != address(0), "TORN: can not send to zero address");

    if (_token == IERC20(0)) {
      // for Ether
      uint256 totalBalance = address(this).balance;
      uint256 balance = _balance == 0 ? totalBalance : Math.min(totalBalance, _balance);
      _to.transfer(balance);
    } else {
      // any other erc20
      uint256 totalBalance = _token.balanceOf(address(this));
      uint256 balance = _balance == 0 ? totalBalance : Math.min(totalBalance, _balance);
      require(balance > 0, "TORN: trying to send 0 balance");
      _token.safeTransfer(_to, balance);
    }
  }
}