pragma solidity ^0.5.0;

library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev Give an account access to this role.
     */
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    /**
     * @dev Remove an account's access to this role.
     */
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    /**
     * @dev Check if an account has this role.
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

contract MinterRole {
    using Roles for Roles.Role;

    event MinterAdded(address indexed account);
    event MinterRemoved(address indexed account);

    Roles.Role private _minters;

    constructor () internal {
        _addMinter(msg.sender);
    }

    modifier onlyMinter() {
        require(isMinter(msg.sender), "MinterRole: caller does not have the Minter role");
        _;
    }

    function isMinter(address account) public view returns (bool) {
        return _minters.has(account);
    }

    function addMinter(address account) public onlyMinter {
        _addMinter(account);
    }

    function renounceMinter() public {
        _removeMinter(msg.sender);
    }

    function _addMinter(address account) internal {
        _minters.add(account);
        emit MinterAdded(account);
    }

    function _removeMinter(address account) internal {
        _minters.remove(account);
        emit MinterRemoved(account);
    }
}

contract PauserRole {
    using Roles for Roles.Role;

    event PauserAdded(address indexed account);
    event PauserRemoved(address indexed account);

    Roles.Role private _pausers;

    constructor () internal {
        _addPauser(msg.sender);
    }

    modifier onlyPauser() {
        require(isPauser(msg.sender), "PauserRole: caller does not have the Pauser role");
        _;
    }

    function isPauser(address account) public view returns (bool) {
        return _pausers.has(account);
    }

    function addPauser(address account) public onlyPauser {
        _addPauser(account);
    }

    function renouncePauser() public {
        _removePauser(msg.sender);
    }

    function _addPauser(address account) internal {
        _pausers.add(account);
        emit PauserAdded(account);
    }

    function _removePauser(address account) internal {
        _pausers.remove(account);
        emit PauserRemoved(account);
    }
}

interface IKIP13 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * [KIP-13 section](http://kips.klaytn.com/KIPs/kip-13-interface_query_standard#how-interface-identifiers-are-defined)
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

contract KIP13 is IKIP13 {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_KIP13 = 0x01ffc9a7;

    /**
     * @dev Mapping of interface ids to whether or not it's supported.
     */
    mapping(bytes4 => bool) private _supportedInterfaces;

    constructor () internal {
        // Derived contracts need only register support for their own interfaces,
        // we register support for KIP13 itself here
        _registerInterface(_INTERFACE_ID_KIP13);
    }

    /**
     * @dev See `IKIP13.supportsInterface`.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual KIP13 interface is automatic and
     * registering its interface id is not required.
     *
     * See `IKIP13.supportsInterface`.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the KIP13 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal {
        require(interfaceId != 0xffffffff, "KIP13: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

contract Pausable is PauserRole {
    /**
     * @dev Emitted when the pause is triggered by a pauser (`account`).
     */
    event Paused(address account);

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

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state. Assigns the Pauser role
     * to the deployer.
     */
    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.
     */
    modifier whenNotPaused() {
        require(!_paused, "Pausable: paused");
        _;
    }

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

    /**
     * @dev Called by a pauser to pause, triggers stopped state.
     */
    function pause() public onlyPauser whenNotPaused {
        _paused = true;
        emit Paused(msg.sender);
    }

    /**
     * @dev Called by a pauser to unpause, returns to normal state.
     */
    function unpause() public onlyPauser whenPaused {
        _paused = false;
        emit Unpaused(msg.sender);
    }
}

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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

contract IKIP7 is IKIP13 {
    /**
     * @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.
     *
     * > 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 Moves `amount` tokens from the caller's account to `recipient`.
    */
    function safeTransfer(address recipient, uint256 amount, bytes memory data) public;

    /**
    * @dev  Moves `amount` tokens from the caller's account to `recipient`.
    */
    function safeTransfer(address recipient, uint256 amount) public;

    /**
    * @dev Moves `amount` tokens from `sender` to `recipient` using the allowance mechanism.
    * `amount` is then deducted from the caller's allowance.
    */
    function safeTransferFrom(address sender, address recipient, uint256 amount, bytes memory data) public;

    /**
    * @dev Moves `amount` tokens from `sender` to `recipient` using the allowance mechanism.
    * `amount` is then deducted from the caller's allowance.
    */
    function safeTransferFrom(address sender, address recipient, uint256 amount) public;

    /**
     * @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);
}

contract IKIP7Receiver {
    /**
     * @notice Handle the receipt of KIP-7 token
     * @dev The KIP-7 smart contract calls this function on the recipient
     *  after a `safeTransfer`. This function MAY throw to revert and reject the
     *  transfer. Return of other than the magic value MUST result in the
     *  transaction being reverted.
     *  Note: the contract address is always the message sender.
     * @param _operator The address which called `safeTransferFrom` function
     * @param _from The address which previously owned the token
     * @param _amount The token amount which is being transferred.
     * @param _data Additional data with no specified format
     * @return `bytes4(keccak256("onKIP7Received(address,address,uint256,bytes)"))`
     *  unless throwing
     */
    function onKIP7Received(address _operator, address _from, uint256 _amount, bytes memory _data) public returns (bytes4);
}

contract KIP7 is KIP13, IKIP7 {
    using SafeMath for uint256;
    using Address for address;

    // Equals to `bytes4(keccak256("onKIP7Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `IKIP7Receiver(0).onKIP7Received.selector`
    bytes4 private constant _KIP7_RECEIVED = 0x9d188c22;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

    /*
     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
     *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
     *     bytes4(keccak256('transfer(address,uint256)')) == 0xa9059cbb
     *     bytes4(keccak256('allowance(address,address)')) == 0xdd62ed3e
     *     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
     *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
     *     bytes4(keccak256("safeTransfer(address,uint256)")) == 0x423f6cef
     *     bytes4(keccak256("safeTransfer(address,uint256,bytes)")) == 0xeb795549
     *     bytes4(keccak256("safeTransferFrom(address,address,uint256)")) == 0x42842e0e
     *     bytes4(keccak256("safeTransferFrom(address,address,uint256,bytes)")) == 0xb88d4fde
     *
     *     => 0x18160ddd ^ 0x70a08231 ^ 0xa9059cbb ^ 0xdd62ed3e ^ 0x095ea7b3 ^ 0x23b872dd ^ 0x423f6cef ^ 0xeb795549 ^ 0x42842e0e ^ 0xb88d4fde == 0x65787371
     */
    bytes4 private constant _INTERFACE_ID_KIP7 = 0x65787371;

    constructor () public {
        // register the supported interfaces to conform to KIP7 via KIP13
        _registerInterface(_INTERFACE_ID_KIP7);
    }

    /**
     * @dev See `IKIP7.totalSupply`.
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IKIP7.balanceOf`.
     */
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IKIP7.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(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IKIP7.allowance`.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IKIP7.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IKIP7.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the KIP. See the note at the beginning of `KIP7`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - 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, msg.sender, _allowances[sender][msg.sender].sub(amount));
        return true;
    }

    /**
    * @dev  Moves `amount` tokens from the caller's account to `recipient`.
    */
    function safeTransfer(address recipient, uint256 amount) public {
        safeTransfer(recipient, amount, "");
    }

    /**
    * @dev Moves `amount` tokens from the caller's account to `recipient`.
    */
    function safeTransfer(address recipient, uint256 amount, bytes memory data) public {
        transfer(recipient, amount);
        require(_checkOnKIP7Received(msg.sender, recipient, amount, data), "KIP7: transfer to non KIP7Receiver implementer");
    }

    /**
    * @dev Moves `amount` tokens from `sender` to `recipient` using the allowance mechanism.
    * `amount` is then deducted from the caller's allowance.
    */
    function safeTransferFrom(address sender, address recipient, uint256 amount) public {
        safeTransferFrom(sender, recipient, amount, "");
    }

    /**
    * @dev Moves `amount` tokens from `sender` to `recipient` using the allowance mechanism.
    * `amount` is then deducted from the caller's allowance.
    */
    function safeTransferFrom(address sender, address recipient, uint256 amount, bytes memory data) public {
        transferFrom(sender, recipient, amount);
        require(_checkOnKIP7Received(sender, recipient, amount, data), "KIP7: transfer to non KIP7Receiver implementer");
    }

    /**
     * @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), "KIP7: transfer from the zero address");
        require(recipient != address(0), "KIP7: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _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), "KIP7: 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 value) internal {
        require(account != address(0), "KIP7: burn from the zero address");

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

    /**
     * @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 value) internal {
        require(owner != address(0), "KIP7: approve from the zero address");
        require(spender != address(0), "KIP7: approve to the zero address");

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

    /**
     * @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, msg.sender, _allowances[account][msg.sender].sub(amount));
    }

    /**
     * @dev Internal function to invoke `onKIP7Received` on a target address.
     * The call is not executed if the target address is not a contract.
     */
    function _checkOnKIP7Received(address sender, address recipient, uint256 amount, bytes memory _data)
        internal returns (bool)
    {
        if (!recipient.isContract()) {
            return true;
        }

        bytes4 retval = IKIP7Receiver(recipient).onKIP7Received(msg.sender, sender, amount, _data);
        return (retval == _KIP7_RECEIVED);
    }
}

contract KIP7Burnable is KIP13, KIP7 {
    /*
     *     bytes4(keccak256('burn(uint256)')) == 0x42966c68
     *     bytes4(keccak256('burnFrom(address,uint256)')) == 0x79cc6790
     *
     *     => 0x42966c68 ^ 0x79cc6790 == 0x3b5a0bf8
     */
    bytes4 private constant _INTERFACE_ID_KIP7BURNABLE = 0x3b5a0bf8;

    constructor () public {
        // register the supported interfaces to conform to KIP17 via KIP13
        _registerInterface(_INTERFACE_ID_KIP7BURNABLE);
    }
    
    /**
     * @dev Destroys `amount` tokens from the caller.
     *
     * See `KIP7._burn`.
     */
    function burn(uint256 amount) public {
        _burn(msg.sender, amount);
    }

    /**
     * @dev See `KIP7._burnFrom`.
     */
    function burnFrom(address account, uint256 amount) public {
        _burnFrom(account, amount);
    }
}

contract KIP7Metadata is KIP13, IKIP7 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /*
     *     bytes4(keccak256('name()')) == 0x06fdde03
     *     bytes4(keccak256('symbol()')) == 0x95d89b41
     *     bytes4(keccak256('decimals()')) == 0x313ce567
     *
     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0x313ce567 == 0xa219a025
     */
    bytes4 private constant _INTERFACE_ID_KIP7_METADATA = 0xa219a025;

    /**
     * @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;

        // register the supported interfaces to conform to KIP7 via KIP13
        _registerInterface(_INTERFACE_ID_KIP7_METADATA);
    }

    /**
     * @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 that this information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * `IKIP7.balanceOf` and `IKIP7.transfer`.
     */
    function decimals() public view returns (uint8) {
        return _decimals;
    }
}

contract KIP7Mintable is KIP13, KIP7, MinterRole {
    /*
     *     bytes4(keccak256('mint(address,uint256)')) == 0x40c10f19
     *     bytes4(keccak256('isMinter(address)')) == 0xaa271e1a
     *     bytes4(keccak256('addMinter(address)')) == 0x983b2d56
     *     bytes4(keccak256('renounceMinter()')) == 0x98650275
     *
     *     => 0x40c10f19 ^ 0xaa271e1a ^ 0x983b2d56 ^ 0x98650275 == 0xeab83e20
     */
    bytes4 private constant _INTERFACE_ID_KIP7MINTABLE = 0xeab83e20;

    constructor () public {
        // register the supported interfaces to conform to KIP17 via KIP13
        _registerInterface(_INTERFACE_ID_KIP7MINTABLE);
    }

    /**
     * @dev See `KIP7._mint`.
     *
     * Requirements:
     *
     * - the caller must have the `MinterRole`.
     */
    function mint(address account, uint256 amount) public onlyMinter returns (bool) {
        _mint(account, amount);
        return true;
    }
}

contract KIP7Pausable is KIP13, KIP7, Pausable {
    /*
     *     bytes4(keccak256('paused()')) == 0x5c975abb
     *     bytes4(keccak256('pause()')) == 0x8456cb59
     *     bytes4(keccak256('unpause()')) == 0x3f4ba83a
     *     bytes4(keccak256('isPauser(address)')) == 0x46fbf68e
     *     bytes4(keccak256('addPauser(address)')) == 0x82dc1ec4
     *     bytes4(keccak256('renouncePauser()')) == 0x6ef8d66d
     *
     *     => 0x5c975abb ^ 0x8456cb59 ^ 0x3f4ba83a ^ 0x46fbf68e ^ 0x82dc1ec4 ^ 0x6ef8d66d == 0x4d5507ff
     */
    bytes4 private constant _INTERFACE_ID_KIP7PAUSABLE = 0x4d5507ff;

    constructor () public {
        // register the supported interfaces to conform to KIP17 via KIP13
        _registerInterface(_INTERFACE_ID_KIP7PAUSABLE);
    }

    function transfer(address to, uint256 value) public whenNotPaused returns (bool) {
        return super.transfer(to, value);
    }

    function transferFrom(address from, address to, uint256 value) public whenNotPaused returns (bool) {
        return super.transferFrom(from, to, value);
    }

    function approve(address spender, uint256 value) public whenNotPaused returns (bool) {
        return super.approve(spender, value);
    }
}

contract KIP7Token is KIP7Mintable, KIP7Burnable, KIP7Pausable, KIP7Metadata {
    constructor(string memory name, string memory symbol, uint8 decimals, uint256 initialSupply) KIP7Metadata(name, symbol, decimals) public {
        _mint(msg.sender, initialSupply);
    }
}

library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * This test is non-exhaustive, and there may be false-negatives: during the
     * execution of a contract's constructor, its address will be reported as
     * not containing a contract.
     *
     * > It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     */
    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;
    }
}