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

pragma solidity ^0.5.0;

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

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

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

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

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * 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/ERC20Detailed.sol

pragma solidity ^0.5.0;


/**
 * @dev Optional functions from the ERC20 standard.
 */
contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for `name`, `symbol`, and `decimals`. All three of
     * these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

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

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

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

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

pragma solidity ^0.5.0;

/*
 * @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.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

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

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

pragma solidity ^0.5.0;

/**
 * @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.
     *
     * _Available since v2.4.0._
     */
    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.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

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

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    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/ERC20.sol

pragma solidity ^0.5.0;




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

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

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

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

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

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

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public 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 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 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 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 {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

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

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

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

        _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 is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal {
        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 Destroys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See {_burn} and {_approve}.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
    }
}

// File: @openzeppelin/contracts/GSN/IRelayRecipient.sol

pragma solidity ^0.5.0;

/**
 * @dev Base interface for a contract that will be called via the GSN from {IRelayHub}.
 *
 * TIP: You don't need to write an implementation yourself! Inherit from {GSNRecipient} instead.
 */
interface IRelayRecipient {
    /**
     * @dev Returns the address of the {IRelayHub} instance this recipient interacts with.
     */
    function getHubAddr() external view returns (address);

    /**
     * @dev Called by {IRelayHub} to validate if this recipient accepts being charged for a relayed call. Note that the
     * recipient will be charged regardless of the execution result of the relayed call (i.e. if it reverts or not).
     *
     * The relay request was originated by `from` and will be served by `relay`. `encodedFunction` is the relayed call
     * calldata, so its first four bytes are the function selector. The relayed call will be forwarded `gasLimit` gas,
     * and the transaction executed with a gas price of at least `gasPrice`. `relay`'s fee is `transactionFee`, and the
     * recipient will be charged at most `maxPossibleCharge` (in wei). `nonce` is the sender's (`from`) nonce for
     * replay attack protection in {IRelayHub}, and `approvalData` is a optional parameter that can be used to hold a signature
     * over all or some of the previous values.
     *
     * Returns a tuple, where the first value is used to indicate approval (0) or rejection (custom non-zero error code,
     * values 1 to 10 are reserved) and the second one is data to be passed to the other {IRelayRecipient} functions.
     *
     * {acceptRelayedCall} is called with 50k gas: if it runs out during execution, the request will be considered
     * rejected. A regular revert will also trigger a rejection.
     */
    function acceptRelayedCall(
        address relay,
        address from,
        bytes calldata encodedFunction,
        uint256 transactionFee,
        uint256 gasPrice,
        uint256 gasLimit,
        uint256 nonce,
        bytes calldata approvalData,
        uint256 maxPossibleCharge
    )
        external
        view
        returns (uint256, bytes memory);

    /**
     * @dev Called by {IRelayHub} on approved relay call requests, before the relayed call is executed. This allows to e.g.
     * pre-charge the sender of the transaction.
     *
     * `context` is the second value returned in the tuple by {acceptRelayedCall}.
     *
     * Returns a value to be passed to {postRelayedCall}.
     *
     * {preRelayedCall} is called with 100k gas: if it runs out during exection or otherwise reverts, the relayed call
     * will not be executed, but the recipient will still be charged for the transaction's cost.
     */
    function preRelayedCall(bytes calldata context) external returns (bytes32);

    /**
     * @dev Called by {IRelayHub} on approved relay call requests, after the relayed call is executed. This allows to e.g.
     * charge the user for the relayed call costs, return any overcharges from {preRelayedCall}, or perform
     * contract-specific bookkeeping.
     *
     * `context` is the second value returned in the tuple by {acceptRelayedCall}. `success` is the execution status of
     * the relayed call. `actualCharge` is an estimate of how much the recipient will be charged for the transaction,
     * not including any gas used by {postRelayedCall} itself. `preRetVal` is {preRelayedCall}'s return value.
     *
     *
     * {postRelayedCall} is called with 100k gas: if it runs out during execution or otherwise reverts, the relayed call
     * and the call to {preRelayedCall} will be reverted retroactively, but the recipient will still be charged for the
     * transaction's cost.
     */
    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external;
}

// File: @openzeppelin/contracts/GSN/IRelayHub.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface for `RelayHub`, the core contract of the GSN. Users should not need to interact with this contract
 * directly.
 *
 * See the https://github.com/OpenZeppelin/openzeppelin-gsn-helpers[OpenZeppelin GSN helpers] for more information on
 * how to deploy an instance of `RelayHub` on your local test network.
 */
interface IRelayHub {
    // Relay management

    /**
     * @dev Adds stake to a relay and sets its `unstakeDelay`. If the relay does not exist, it is created, and the caller
     * of this function becomes its owner. If the relay already exists, only the owner can call this function. A relay
     * cannot be its own owner.
     *
     * All Ether in this function call will be added to the relay's stake.
     * Its unstake delay will be assigned to `unstakeDelay`, but the new value must be greater or equal to the current one.
     *
     * Emits a {Staked} event.
     */
    function stake(address relayaddr, uint256 unstakeDelay) external payable;

    /**
     * @dev Emitted when a relay's stake or unstakeDelay are increased
     */
    event Staked(address indexed relay, uint256 stake, uint256 unstakeDelay);

    /**
     * @dev Registers the caller as a relay.
     * The relay must be staked for, and not be a contract (i.e. this function must be called directly from an EOA).
     *
     * This function can be called multiple times, emitting new {RelayAdded} events. Note that the received
     * `transactionFee` is not enforced by {relayCall}.
     *
     * Emits a {RelayAdded} event.
     */
    function registerRelay(uint256 transactionFee, string calldata url) external;

    /**
     * @dev Emitted when a relay is registered or re-registerd. Looking at these events (and filtering out
     * {RelayRemoved} events) lets a client discover the list of available relays.
     */
    event RelayAdded(address indexed relay, address indexed owner, uint256 transactionFee, uint256 stake, uint256 unstakeDelay, string url);

    /**
     * @dev Removes (deregisters) a relay. Unregistered (but staked for) relays can also be removed.
     *
     * Can only be called by the owner of the relay. After the relay's `unstakeDelay` has elapsed, {unstake} will be
     * callable.
     *
     * Emits a {RelayRemoved} event.
     */
    function removeRelayByOwner(address relay) external;

    /**
     * @dev Emitted when a relay is removed (deregistered). `unstakeTime` is the time when unstake will be callable.
     */
    event RelayRemoved(address indexed relay, uint256 unstakeTime);

    /** Deletes the relay from the system, and gives back its stake to the owner.
     *
     * Can only be called by the relay owner, after `unstakeDelay` has elapsed since {removeRelayByOwner} was called.
     *
     * Emits an {Unstaked} event.
     */
    function unstake(address relay) external;

    /**
     * @dev Emitted when a relay is unstaked for, including the returned stake.
     */
    event Unstaked(address indexed relay, uint256 stake);

    // States a relay can be in
    enum RelayState {
        Unknown, // The relay is unknown to the system: it has never been staked for
        Staked, // The relay has been staked for, but it is not yet active
        Registered, // The relay has registered itself, and is active (can relay calls)
        Removed    // The relay has been removed by its owner and can no longer relay calls. It must wait for its unstakeDelay to elapse before it can unstake
    }

    /**
     * @dev Returns a relay's status. Note that relays can be deleted when unstaked or penalized, causing this function
     * to return an empty entry.
     */
    function getRelay(address relay) external view returns (uint256 totalStake, uint256 unstakeDelay, uint256 unstakeTime, address payable owner, RelayState state);

    // Balance management

    /**
     * @dev Deposits Ether for a contract, so that it can receive (and pay for) relayed transactions.
     *
     * Unused balance can only be withdrawn by the contract itself, by calling {withdraw}.
     *
     * Emits a {Deposited} event.
     */
    function depositFor(address target) external payable;

    /**
     * @dev Emitted when {depositFor} is called, including the amount and account that was funded.
     */
    event Deposited(address indexed recipient, address indexed from, uint256 amount);

    /**
     * @dev Returns an account's deposits. These can be either a contracts's funds, or a relay owner's revenue.
     */
    function balanceOf(address target) external view returns (uint256);

    /**
     * Withdraws from an account's balance, sending it back to it. Relay owners call this to retrieve their revenue, and
     * contracts can use it to reduce their funding.
     *
     * Emits a {Withdrawn} event.
     */
    function withdraw(uint256 amount, address payable dest) external;

    /**
     * @dev Emitted when an account withdraws funds from `RelayHub`.
     */
    event Withdrawn(address indexed account, address indexed dest, uint256 amount);

    // Relaying

    /**
     * @dev Checks if the `RelayHub` will accept a relayed operation.
     * Multiple things must be true for this to happen:
     *  - all arguments must be signed for by the sender (`from`)
     *  - the sender's nonce must be the current one
     *  - the recipient must accept this transaction (via {acceptRelayedCall})
     *
     * Returns a `PreconditionCheck` value (`OK` when the transaction can be relayed), or a recipient-specific error
     * code if it returns one in {acceptRelayedCall}.
     */
    function canRelay(
        address relay,
        address from,
        address to,
        bytes calldata encodedFunction,
        uint256 transactionFee,
        uint256 gasPrice,
        uint256 gasLimit,
        uint256 nonce,
        bytes calldata signature,
        bytes calldata approvalData
    ) external view returns (uint256 status, bytes memory recipientContext);

    // Preconditions for relaying, checked by canRelay and returned as the corresponding numeric values.
    enum PreconditionCheck {
        OK,                         // All checks passed, the call can be relayed
        WrongSignature,             // The transaction to relay is not signed by requested sender
        WrongNonce,                 // The provided nonce has already been used by the sender
        AcceptRelayedCallReverted,  // The recipient rejected this call via acceptRelayedCall
        InvalidRecipientStatusCode  // The recipient returned an invalid (reserved) status code
    }

    /**
     * @dev Relays a transaction.
     *
     * For this to succeed, multiple conditions must be met:
     *  - {canRelay} must `return PreconditionCheck.OK`
     *  - the sender must be a registered relay
     *  - the transaction's gas price must be larger or equal to the one that was requested by the sender
     *  - the transaction must have enough gas to not run out of gas if all internal transactions (calls to the
     * recipient) use all gas available to them
     *  - the recipient must have enough balance to pay the relay for the worst-case scenario (i.e. when all gas is
     * spent)
     *
     * If all conditions are met, the call will be relayed and the recipient charged. {preRelayedCall}, the encoded
     * function and {postRelayedCall} will be called in that order.
     *
     * Parameters:
     *  - `from`: the client originating the request
     *  - `to`: the target {IRelayRecipient} contract
     *  - `encodedFunction`: the function call to relay, including data
     *  - `transactionFee`: fee (%) the relay takes over actual gas cost
     *  - `gasPrice`: gas price the client is willing to pay
     *  - `gasLimit`: gas to forward when calling the encoded function
     *  - `nonce`: client's nonce
     *  - `signature`: client's signature over all previous params, plus the relay and RelayHub addresses
     *  - `approvalData`: dapp-specific data forwared to {acceptRelayedCall}. This value is *not* verified by the
     * `RelayHub`, but it still can be used for e.g. a signature.
     *
     * Emits a {TransactionRelayed} event.
     */
    function relayCall(
        address from,
        address to,
        bytes calldata encodedFunction,
        uint256 transactionFee,
        uint256 gasPrice,
        uint256 gasLimit,
        uint256 nonce,
        bytes calldata signature,
        bytes calldata approvalData
    ) external;

    /**
     * @dev Emitted when an attempt to relay a call failed.
     *
     * This can happen due to incorrect {relayCall} arguments, or the recipient not accepting the relayed call. The
     * actual relayed call was not executed, and the recipient not charged.
     *
     * The `reason` parameter contains an error code: values 1-10 correspond to `PreconditionCheck` entries, and values
     * over 10 are custom recipient error codes returned from {acceptRelayedCall}.
     */
    event CanRelayFailed(address indexed relay, address indexed from, address indexed to, bytes4 selector, uint256 reason);

    /**
     * @dev Emitted when a transaction is relayed. 
     * Useful when monitoring a relay's operation and relayed calls to a contract
     *
     * Note that the actual encoded function might be reverted: this is indicated in the `status` parameter.
     *
     * `charge` is the Ether value deducted from the recipient's balance, paid to the relay's owner.
     */
    event TransactionRelayed(address indexed relay, address indexed from, address indexed to, bytes4 selector, RelayCallStatus status, uint256 charge);

    // Reason error codes for the TransactionRelayed event
    enum RelayCallStatus {
        OK,                      // The transaction was successfully relayed and execution successful - never included in the event
        RelayedCallFailed,       // The transaction was relayed, but the relayed call failed
        PreRelayedFailed,        // The transaction was not relayed due to preRelatedCall reverting
        PostRelayedFailed,       // The transaction was relayed and reverted due to postRelatedCall reverting
        RecipientBalanceChanged  // The transaction was relayed and reverted due to the recipient's balance changing
    }

    /**
     * @dev Returns how much gas should be forwarded to a call to {relayCall}, in order to relay a transaction that will
     * spend up to `relayedCallStipend` gas.
     */
    function requiredGas(uint256 relayedCallStipend) external view returns (uint256);

    /**
     * @dev Returns the maximum recipient charge, given the amount of gas forwarded, gas price and relay fee.
     */
    function maxPossibleCharge(uint256 relayedCallStipend, uint256 gasPrice, uint256 transactionFee) external view returns (uint256);

     // Relay penalization. 
     // Any account can penalize relays, removing them from the system immediately, and rewarding the
    // reporter with half of the relay's stake. The other half is burned so that, even if the relay penalizes itself, it
    // still loses half of its stake.

    /**
     * @dev Penalize a relay that signed two transactions using the same nonce (making only the first one valid) and
     * different data (gas price, gas limit, etc. may be different).
     *
     * The (unsigned) transaction data and signature for both transactions must be provided.
     */
    function penalizeRepeatedNonce(bytes calldata unsignedTx1, bytes calldata signature1, bytes calldata unsignedTx2, bytes calldata signature2) external;

    /**
     * @dev Penalize a relay that sent a transaction that didn't target `RelayHub`'s {registerRelay} or {relayCall}.
     */
    function penalizeIllegalTransaction(bytes calldata unsignedTx, bytes calldata signature) external;

    /**
     * @dev Emitted when a relay is penalized.
     */
    event Penalized(address indexed relay, address sender, uint256 amount);

    /**
     * @dev Returns an account's nonce in `RelayHub`.
     */
    function getNonce(address from) external view returns (uint256);
}

// File: @openzeppelin/contracts/GSN/GSNRecipient.sol

pragma solidity ^0.5.0;




/**
 * @dev Base GSN recipient contract: includes the {IRelayRecipient} interface
 * and enables GSN support on all contracts in the inheritance tree.
 *
 * TIP: This contract is abstract. The functions {IRelayRecipient-acceptRelayedCall},
 *  {_preRelayedCall}, and {_postRelayedCall} are not implemented and must be
 * provided by derived contracts. See the
 * xref:ROOT:gsn-strategies.adoc#gsn-strategies[GSN strategies] for more
 * information on how to use the pre-built {GSNRecipientSignature} and
 * {GSNRecipientERC20Fee}, or how to write your own.
 */
contract GSNRecipient is IRelayRecipient, Context {
    // Default RelayHub address, deployed on mainnet and all testnets at the same address
    address private _relayHub = 0xD216153c06E857cD7f72665E0aF1d7D82172F494;

    uint256 constant private RELAYED_CALL_ACCEPTED = 0;
    uint256 constant private RELAYED_CALL_REJECTED = 11;

    // How much gas is forwarded to postRelayedCall
    uint256 constant internal POST_RELAYED_CALL_MAX_GAS = 100000;

    /**
     * @dev Emitted when a contract changes its {IRelayHub} contract to a new one.
     */
    event RelayHubChanged(address indexed oldRelayHub, address indexed newRelayHub);

    /**
     * @dev Returns the address of the {IRelayHub} contract for this recipient.
     */
    function getHubAddr() public view returns (address) {
        return _relayHub;
    }

    /**
     * @dev Switches to a new {IRelayHub} instance. This method is added for future-proofing: there's no reason to not
     * use the default instance.
     *
     * IMPORTANT: After upgrading, the {GSNRecipient} will no longer be able to receive relayed calls from the old
     * {IRelayHub} instance. Additionally, all funds should be previously withdrawn via {_withdrawDeposits}.
     */
    function _upgradeRelayHub(address newRelayHub) internal {
        address currentRelayHub = _relayHub;
        require(newRelayHub != address(0), "GSNRecipient: new RelayHub is the zero address");
        require(newRelayHub != currentRelayHub, "GSNRecipient: new RelayHub is the current one");

        emit RelayHubChanged(currentRelayHub, newRelayHub);

        _relayHub = newRelayHub;
    }

    /**
     * @dev Returns the version string of the {IRelayHub} for which this recipient implementation was built. If
     * {_upgradeRelayHub} is used, the new {IRelayHub} instance should be compatible with this version.
     */
    // This function is view for future-proofing, it may require reading from
    // storage in the future.
    function relayHubVersion() public view returns (string memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return "1.0.0";
    }

    /**
     * @dev Withdraws the recipient's deposits in `RelayHub`.
     *
     * Derived contracts should expose this in an external interface with proper access control.
     */
    function _withdrawDeposits(uint256 amount, address payable payee) internal {
        IRelayHub(_relayHub).withdraw(amount, payee);
    }

    // Overrides for Context's functions: when called from RelayHub, sender and
    // data require some pre-processing: the actual sender is stored at the end
    // of the call data, which in turns means it needs to be removed from it
    // when handling said data.

    /**
     * @dev Replacement for msg.sender. Returns the actual sender of a transaction: msg.sender for regular transactions,
     * and the end-user for GSN relayed calls (where msg.sender is actually `RelayHub`).
     *
     * IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.sender`, and use {_msgSender} instead.
     */
    function _msgSender() internal view returns (address payable) {
        if (msg.sender != _relayHub) {
            return msg.sender;
        } else {
            return _getRelayedCallSender();
        }
    }

    /**
     * @dev Replacement for msg.data. Returns the actual calldata of a transaction: msg.data for regular transactions,
     * and a reduced version for GSN relayed calls (where msg.data contains additional information).
     *
     * IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.data`, and use {_msgData} instead.
     */
    function _msgData() internal view returns (bytes memory) {
        if (msg.sender != _relayHub) {
            return msg.data;
        } else {
            return _getRelayedCallData();
        }
    }

    // Base implementations for pre and post relayedCall: only RelayHub can invoke them, and data is forwarded to the
    // internal hook.

    /**
     * @dev See `IRelayRecipient.preRelayedCall`.
     *
     * This function should not be overriden directly, use `_preRelayedCall` instead.
     *
     * * Requirements:
     *
     * - the caller must be the `RelayHub` contract.
     */
    function preRelayedCall(bytes calldata context) external returns (bytes32) {
        require(msg.sender == getHubAddr(), "GSNRecipient: caller is not RelayHub");
        return _preRelayedCall(context);
    }

    /**
     * @dev See `IRelayRecipient.preRelayedCall`.
     *
     * Called by `GSNRecipient.preRelayedCall`, which asserts the caller is the `RelayHub` contract. Derived contracts
     * must implement this function with any relayed-call preprocessing they may wish to do.
     *
     */
    function _preRelayedCall(bytes memory context) internal returns (bytes32);

    /**
     * @dev See `IRelayRecipient.postRelayedCall`.
     *
     * This function should not be overriden directly, use `_postRelayedCall` instead.
     *
     * * Requirements:
     *
     * - the caller must be the `RelayHub` contract.
     */
    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external {
        require(msg.sender == getHubAddr(), "GSNRecipient: caller is not RelayHub");
        _postRelayedCall(context, success, actualCharge, preRetVal);
    }

    /**
     * @dev See `IRelayRecipient.postRelayedCall`.
     *
     * Called by `GSNRecipient.postRelayedCall`, which asserts the caller is the `RelayHub` contract. Derived contracts
     * must implement this function with any relayed-call postprocessing they may wish to do.
     *
     */
    function _postRelayedCall(bytes memory context, bool success, uint256 actualCharge, bytes32 preRetVal) internal;

    /**
     * @dev Return this in acceptRelayedCall to proceed with the execution of a relayed call. Note that this contract
     * will be charged a fee by RelayHub
     */
    function _approveRelayedCall() internal pure returns (uint256, bytes memory) {
        return _approveRelayedCall("");
    }

    /**
     * @dev See `GSNRecipient._approveRelayedCall`.
     *
     * This overload forwards `context` to _preRelayedCall and _postRelayedCall.
     */
    function _approveRelayedCall(bytes memory context) internal pure returns (uint256, bytes memory) {
        return (RELAYED_CALL_ACCEPTED, context);
    }

    /**
     * @dev Return this in acceptRelayedCall to impede execution of a relayed call. No fees will be charged.
     */
    function _rejectRelayedCall(uint256 errorCode) internal pure returns (uint256, bytes memory) {
        return (RELAYED_CALL_REJECTED + errorCode, "");
    }

    /*
     * @dev Calculates how much RelayHub will charge a recipient for using `gas` at a `gasPrice`, given a relayer's
     * `serviceFee`.
     */
    function _computeCharge(uint256 gas, uint256 gasPrice, uint256 serviceFee) internal pure returns (uint256) {
        // The fee is expressed as a percentage. E.g. a value of 40 stands for a 40% fee, so the recipient will be
        // charged for 1.4 times the spent amount.
        return (gas * gasPrice * (100 + serviceFee)) / 100;
    }

    function _getRelayedCallSender() private pure returns (address payable result) {
        // We need to read 20 bytes (an address) located at array index msg.data.length - 20. In memory, the array
        // is prefixed with a 32-byte length value, so we first add 32 to get the memory read index. However, doing
        // so would leave the address in the upper 20 bytes of the 32-byte word, which is inconvenient and would
        // require bit shifting. We therefore subtract 12 from the read index so the address lands on the lower 20
        // bytes. This can always be done due to the 32-byte prefix.

        // The final memory read index is msg.data.length - 20 + 32 - 12 = msg.data.length. Using inline assembly is the
        // easiest/most-efficient way to perform this operation.

        // These fields are not accessible from assembly
        bytes memory array = msg.data;
        uint256 index = msg.data.length;

        // solhint-disable-next-line no-inline-assembly
        assembly {
            // Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
            result := and(mload(add(array, index)), 0xffffffffffffffffffffffffffffffffffffffff)
        }
        return result;
    }

    function _getRelayedCallData() private pure returns (bytes memory) {
        // RelayHub appends the sender address at the end of the calldata, so in order to retrieve the actual msg.data,
        // we must strip the last 20 bytes (length of an address type) from it.

        uint256 actualDataLength = msg.data.length - 20;
        bytes memory actualData = new bytes(actualDataLength);

        for (uint256 i = 0; i < actualDataLength; ++i) {
            actualData[i] = msg.data[i];
        }

        return actualData;
    }
}

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

pragma solidity ^0.5.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be 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(isOwner(), "Ownable: caller is not the owner");
        _;
    }

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

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

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

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

// File: interface/IStormXToken.sol

pragma solidity 0.5.16;


contract IStormXToken is ERC20 {
  function unlockedBalanceOf(address account) public view returns (uint256);
}

// File: contracts/StormXGSNRecipient.sol

pragma solidity 0.5.16;






contract StormXGSNRecipient is GSNRecipient, Ownable {

  using SafeMath for uint256;

  // Variables and constants for supporting GSN
  uint256 constant INSUFFICIENT_BALANCE = 11;
  uint256 public chargeFee;
  address public stormXReserve;

  // importing ``StormXToken.sol`` results in infinite loop
  // using only an interface
  IStormXToken public token;
  
  event StormXReserveSet(address newAddress);
  event ChargeFeeSet(uint256 newFee);

  /**
   * @param tokenAddress address of `StormXToken.sol`
   * @param reserve address that receives GSN charge fee
   */
  constructor(address tokenAddress, address reserve) public {
    require(tokenAddress != address(0), "Invalid token address");
    require(reserve != address(0), "Invalid reserve address");

    token = IStormXToken(tokenAddress);
    stormXReserve = reserve;
    // decimals of StormXToken is 18
    chargeFee = 10 * (10 ** 18);
  }

  /**
   * Note: the documentation is copied from
   * `openzeppelin-contracts/contracts/GSN/IRelayRecipient.sol`
   * @dev Called by {IRelayHub} to validate
   * if this recipient accepts being charged for a relayed call.
   * Note that the recipient will be charged regardless of the execution result of the relayed call
   * (i.e. if it reverts or not).
   *
   * The relay request was originated by `from` and will be served by `relay`.
   * `encodedFunction` is the relayed call calldata,
   * so its first four bytes are the function selector.
   * The relayed call will be forwarded `gasLimit` gas,
   * and the transaction executed with a gas price of at least `gasPrice`.
   * `relay`'s fee is `transactionFee`,
   * and the recipient will be charged at most `maxPossibleCharge` (in wei).
   * `nonce` is the sender's (`from`) nonce for replay attack protection in {IRelayHub},
   * and `approvalData` is a optional parameter that can be used to hold a signature
   * over all or some of the previous values.
   *
   * Returns a tuple, where the first value is used to indicate approval (0)
   * or rejection (custom non-zero error code, values 1 to 10 are reserved)
   * and the second one is data to be passed to the other {IRelayRecipient} functions.
   *
   * {acceptRelayedCall} is called with 50k gas: if it runs out during execution,
   * the request will be considered
   * rejected. A regular revert will also trigger a rejection.
   */
  function acceptRelayedCall(
    address relay,
    address from,
    bytes calldata encodedFunction,
    uint256 transactionFee,
    uint256 gasPrice,
    uint256 gasLimit,
    uint256 nonce,
    bytes calldata approvalData,
    uint256 maxPossibleCharge
  )
    external
    view
    returns (uint256, bytes memory) {
      (bool accept, bool chargeBefore) = _acceptRelayedCall(from, encodedFunction);
      if (accept) {
        return  _approveRelayedCall(abi.encode(from, chargeBefore));
      } else {
        return _rejectRelayedCall(INSUFFICIENT_BALANCE);
      }
    }

  /**
   * @dev Sets the address of StormX's reserve
   * @param newReserve the new address of StormX's reserve
   * @return success status of the setting
   */
  function setStormXReserve(address newReserve) public onlyOwner returns (bool) {
    require(newReserve != address(0), "Invalid reserve address");
    stormXReserve = newReserve;
    emit StormXReserveSet(newReserve);
    return true;
  }

 /**
   * @dev Sets the charge fee for GSN calls
   * @param newFee the new charge fee
   * @return success status of the setting
   */
  function setChargeFee(uint256 newFee) public onlyOwner returns (bool) {
    chargeFee = newFee;
    emit ChargeFeeSet(newFee);
    return true;
  }

  /**
   * @dev Checks whether to accept a GSN relayed call
   * @param from the user originating the GSN relayed call
   * @param encodedFunction the function call to relay, including data
   * @return ``accept`` indicates whether to accept the relayed call
   *         ``chargeBefore`` indicates whether to charge before executing encoded function
   */
  function _acceptRelayedCall(
    address from,
    bytes memory encodedFunction
  ) internal view returns (bool accept, bool chargeBefore);

  function _preRelayedCall(bytes memory context) internal returns (bytes32) {
    (address user, bool chargeBefore) = abi.decode(context, (address, bool));
    // charge the user with specified amount of fee
    // if the user is not calling ``convert()``
    if (chargeBefore) {
      require(
        token.transferFrom(user, stormXReserve, chargeFee),
        "Charging fails before executing the function"
      );
    }
    return "";
  }

  function _postRelayedCall(
    bytes memory context,
    bool success,
    uint256 actualCharge,
    bytes32 preRetVal
  ) internal {
    (address user, bool chargeBefore) = abi.decode(context, (address, bool));
    if (!chargeBefore) {
      require(
        token.transferFrom(user, stormXReserve, chargeFee),
        "Charging fails after executing the function"
      );
    }
  }

  /**
   * @dev Reads a bytes4 value from a position in a byte array.
   * Note: for reference, see source code
   * https://etherscan.io/address/0xD216153c06E857cD7f72665E0aF1d7D82172F494#code
   * @param b Byte array containing a bytes4 value.
   * @param index Index in byte array of bytes4 value.
   * @return bytes4 value from byte array.
   */
  function readBytes4(
    bytes memory b,
    uint256 index
  ) internal
    pure
    returns (bytes4 result)
  {
    require(
      b.length >= index + 4,
      "GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED"
    );

    // Arrays are prefixed by a 32 byte length field
    index += 32;

    // Read the bytes4 from array memory
    assembly {
      result := mload(add(b, index))
      // Solidity does not require us to clean the trailing bytes.
      // We do it anyway
      result := and(result, 0xFFFFFFFF00000000000000000000000000000000000000000000000000000000)
    }
    return result;
  }

  /**
   * @dev Reads a bytes32 value from a position in a byte array.
   * Note: for reference, see source code
   * https://etherscan.io/address/0xD216153c06E857cD7f72665E0aF1d7D82172F494#code
   * @param b Byte array containing a bytes32 value.
   * @param index Index in byte array of bytes32 value.
   * @return bytes32 value from byte array.
   */
  function readBytes32(
    bytes memory b,
    uint256 index
  )
    internal
    pure
    returns (bytes32 result)
  {
    require(
      b.length >= index + 32,
      "GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED"
    );

    // Arrays are prefixed by a 256 bit length parameter
    index += 32;

    // Read the bytes32 from array memory
    assembly {
      result := mload(add(b, index))
    }
    return result;
  }
  
  /**
   * @dev Reads a uint256 value from a position in a byte array.
   * Note: for reference, see source code
   * https://etherscan.io/address/0xD216153c06E857cD7f72665E0aF1d7D82172F494#code
   * @param b Byte array containing a uint256 value.
   * @param index Index in byte array of uint256 value.
   * @return uint256 value from byte array.
   */
  function readUint256(
    bytes memory b,
    uint256 index
  ) internal
    pure
    returns (uint256 result)
  {
    result = uint256(readBytes32(b, index));
    return result;
  }

 /**
  * @dev extract parameter from encoded-function block.
  * Note: for reference, see source code
  * https://etherscan.io/address/0xD216153c06E857cD7f72665E0aF1d7D82172F494#code
  * https://solidity.readthedocs.io/en/develop/abi-spec.html#formal-specification-of-the-encoding
  * note that the type of the parameter must be static.
  * the return value should be casted to the right type.
  * @param msgData encoded calldata
  * @param index in byte array of bytes memory
  * @return the parameter extracted from call data
  */
  function getParam(bytes memory msgData, uint index) internal pure returns (uint256) {
    return readUint256(msgData, 4 + index * 32);
  }
}

// File: contracts/StormXToken.sol

pragma solidity 0.5.16;






contract StormXToken is
  StormXGSNRecipient,
  ERC20,
  ERC20Detailed("StormX", "STMX", 18) {

  using SafeMath for uint256;

  bool public transfersEnabled;
  mapping(address => bool) public autoStakingDisabled;
  bool public initialized = false;
  address public swap;
  address public rewardRole;

  // Variables for staking feature
  mapping(address => uint256) public lockedBalanceOf;

  event TokenLocked(address indexed account, uint256 amount);
  event TokenUnlocked(address indexed account, uint256 amount);
  event TransfersEnabled(bool newStatus);
  event SwapAddressAdded(address swap);
  event RewardRoleAssigned(address rewardRole);
  event AutoStakingSet(address indexed account, bool status);

  modifier transfersAllowed {
    require(transfersEnabled, "Transfers not available");
    _;
  }

  modifier onlyAuthorized {
    require(_msgSender() == owner() || _msgSender() == rewardRole, "Not authorized");
    _;
  }

  /**
   * @param reserve address of the StormX's reserve that receives GSN charge fee
   * GSN charged fees and remaining tokens
   * after the token migration is closed
   */
  constructor(address reserve)
    // solhint-disable-next-line visibility-modifier-order
    StormXGSNRecipient(address(this), reserve) public {
    }

  /**
   * @param account address of the user this function queries unlocked balance for
   * @return the amount of unlocked tokens of the given address
   *         i.e. the amount of manipulable tokens of the given address
   */
  function unlockedBalanceOf(address account) public view returns (uint256) {
    return balanceOf(account).sub(lockedBalanceOf[account]);
  }

  /**
   * @dev Locks specified amount of tokens for the user
   *      Locked tokens are not manipulable until being unlocked
   *      Locked tokens are still reported as owned by the user
   *      when ``balanceOf()`` is called
   * @param amount specified amount of tokens to be locked
   * @return success status of the locking
   */
  function lock(uint256 amount) public returns (bool) {
    address account = _msgSender();
    require(unlockedBalanceOf(account) >= amount, "Not enough unlocked tokens");
    lockedBalanceOf[account] = lockedBalanceOf[account].add(amount);
    emit TokenLocked(account, amount);
    return true;
  }

  /**
   * @dev Unlocks specified amount of tokens for the user
   *      Unlocked tokens are manipulable until being locked
   * @param amount specified amount of tokens to be unlocked
   * @return success status of the unlocking
   */
  function unlock(uint256 amount) public returns (bool) {
    address account = _msgSender();
    require(lockedBalanceOf[account] >= amount, "Not enough locked tokens");
    lockedBalanceOf[account] = lockedBalanceOf[account].sub(amount);
    emit TokenUnlocked(account, amount);
    return true;
  }

  /**
   * @dev The only difference from standard ERC20 ``transferFrom()`` is that
   *     it only succeeds if the sender has enough unlocked tokens
   *     Note: this function is also used by every StormXGSNRecipient
   *           when charging.
   * @param sender address of the sender
   * @param recipient address of the recipient
   * @param amount specified amount of tokens to be transferred
   * @return success status of the transferring
   */
  function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
    require(unlockedBalanceOf(sender) >= amount, "Not enough unlocked token balance of sender");
    // if the msg.sender is charging ``sender`` for a GSN fee
    // allowance does not apply
    // so that no user approval is required for GSN calls
    if (_msgSender() == address(this) || _msgSender() == swap) {
      _transfer(sender, recipient, amount);
      return true;
    } else {
      return super.transferFrom(sender, recipient, amount);
    }
  }

  /**
   * @dev The only difference from standard ERC20 ``transfer()`` is that
   *     it only succeeds if the user has enough unlocked tokens
   * @param recipient address of the recipient
   * @param amount specified amount of tokens to be transferred
   * @return success status of the transferring
   */
  function transfer(address recipient, uint256 amount) public returns (bool) {
    require(unlockedBalanceOf(_msgSender()) >= amount, "Not enough unlocked token balance");
    return super.transfer(recipient, amount);
  }

  /**
   * @dev Transfers tokens in batch
   * @param recipients an array of recipient addresses
   * @param values an array of specified amount of tokens to be transferred
   * @return success status of the batch transferring
   */
  function transfers(
    address[] memory recipients,
    uint256[] memory values
  ) public transfersAllowed returns (bool) {
    require(recipients.length == values.length, "Input lengths do not match");

    for (uint256 i = 0; i < recipients.length; i++) {
      transfer(recipients[i], values[i]);
    }
    return true;
  }

  /**
   * @dev Enables the method ``transfers()`` if ``enable=true``,
   * and disables ``transfers()`` otherwise
   * @param enable the expected new availability of the method ``transfers()``
   */
  function enableTransfers(bool enable) public onlyOwner returns (bool) {
    transfersEnabled = enable;
    emit TransfersEnabled(enable);
    return true;
  }

  function mint(address account, uint256 amount) public {
    require(initialized, "The contract is not initialized yet");
    require(_msgSender() == swap, "not authorized to mint");
    _mint(account, amount);
  }

  /**
   * @dev Initializes this contract
   *      Sets address ``swap`` as the only valid minter for this token
   *      Note: must be called before token migration opens in ``Swap.sol``
   * @param _swap address of the deployed contract ``Swap.sol``
   */
  function initialize(address _swap) public onlyOwner {
    require(!initialized, "cannot initialize twice");
    require(_swap != address(0), "invalid swap address");
    swap = _swap;
    transfersEnabled = true;
    emit TransfersEnabled(true);
    initialized = true;
    emit SwapAddressAdded(_swap);
  }

  /**
   * @dev Assigns `rewardRole` to the specified address
   * @param account address to be assigned as the `rewardRole`
   */
  function assignRewardRole(address account) public onlyOwner {
    rewardRole = account;
    emit RewardRoleAssigned(account);
  }

  /**
   * @dev Transfers tokens to users as rewards
   * @param recipient address that receives the rewarded tokens
   * @param amount amount of rewarded tokens
   */
  function reward(address recipient, uint256 amount) public onlyAuthorized {
    require(recipient != address(0), "Invalid recipient address provided");

    require(transfer(recipient, amount), "Transfer fails when rewarding a user");
    // If `autoStakingDisabled[user] == false`,
    // auto staking is enabled for current user
    if (!autoStakingDisabled[recipient]) {
      lockedBalanceOf[recipient] = lockedBalanceOf[recipient].add(amount);
      emit TokenLocked(recipient, amount);
    }
  }

  /**
   * @dev Rewards users in batch
   * @param recipients an array of recipient address
   * @param values an array of specified amount of tokens to be rewarded
   */
  function rewards(address[] memory recipients, uint256[] memory values) public onlyAuthorized {
    require(recipients.length == values.length, "Input lengths do not match");

    for (uint256 i = 0; i < recipients.length; i++) {
      reward(recipients[i], values[i]);
    }
  }

  /**
   * @dev Sets auto-staking feature status for users
   * If `enabled = true`, rewarded tokens will be automatically staked for the message sender
   * Else, rewarded tokens will not be automatically staked for the message sender.
   * @param enabled expected status of the user's auto-staking feature status
   */
  function setAutoStaking(bool enabled) public {
    // If `enabled == false`, set `autoStakingDisabled[user] = true`
    autoStakingDisabled[_msgSender()] = !enabled;
    emit AutoStakingSet(_msgSender(), enabled);
  }

  /**
   * @dev Checks whether to accept a GSN relayed call
   * @param from the user originating the GSN relayed call
   * @param encodedFunction the function call to relay, including data
   * @return ``accept`` indicates whether to accept the relayed call
   *         ``chargeBefore`` indicates whether to charge before executing encoded function
   */
  function _acceptRelayedCall(
    address from,
    bytes memory encodedFunction
  ) internal view returns (bool accept, bool chargeBefore) {
    bool chargeBefore = true;
    uint256 unlockedBalance = unlockedBalanceOf(from);
    if (unlockedBalance < chargeFee) {
      // charge users after executing the encoded function
      chargeBefore = false;
      bytes4 selector = readBytes4(encodedFunction, 0);
      if (selector == bytes4(keccak256("unlock(uint256)"))) {
        // unlocked token balance for the user if transaction succeeds
        uint256 amount = uint256(getParam(encodedFunction, 0)).add(unlockedBalance);
        return (amount >= chargeFee, chargeBefore);
      } else if (selector == bytes4(keccak256("transferFrom(address,address,uint256)"))) {
        address sender = address(getParam(encodedFunction, 0));
        address recipient = address(getParam(encodedFunction, 1));
        uint256 amount = getParam(encodedFunction, 2);

        bool accept = recipient == from &&
          // no real effect of `transferfrom()` if `sender == recipient`
          sender != recipient &&
          // `from` can have enough unlocked token balance after the transaction
          amount.add(unlockedBalance) >= chargeFee &&
          // check `transferFrom()` can be executed successfully
          unlockedBalanceOf(sender) >= amount &&
          allowance(sender, from) >= amount;
        return (accept, chargeBefore);
      } else {
        // if rejects the call, the value of chargeBefore does not matter
        return (false, chargeBefore);
      }
    } else {
      return (true, chargeBefore);
    }
  }
}