// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;
pragma experimental ABIEncoderV2;

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);
}


library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * 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);
}

interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
      * @dev Safely transfers `tokenId` token from `from` to `to`.
      *
      * Requirements:
      *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
      * - `tokenId` token must exist and be owned by `from`.
      * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
      * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
      *
      * Emits a {Transfer} event.
      */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
}

interface IERC721Metadata is IERC721 {

    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

interface IERC721Enumerable is IERC721 {

    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}


interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(address operator, address from, uint256 tokenId, bytes calldata data)
    external returns (bytes4);
}


contract ERC165 is IERC165 {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_ERC165 = 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 ERC165 itself here
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) public view override returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual ERC165 interface is automatic and
     * registering its interface id is not required.
     *
     * See {IERC165-supportsInterface}.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal virtual {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}


library EnumerableMap {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Map type with
    // bytes32 keys and values.
    // The Map implementation uses private functions, and user-facing
    // implementations (such as Uint256ToAddressMap) are just wrappers around
    // the underlying Map.
    // This means that we can only create new EnumerableMaps for types that fit
    // in bytes32.

    struct MapEntry {
        bytes32 _key;
        bytes32 _value;
    }

    struct Map {
        // Storage of map keys and values
        MapEntry[] _entries;

        // Position of the entry defined by a key in the `entries` array, plus 1
        // because index 0 means a key is not in the map.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Adds a key-value pair to a map, or updates the value for an existing
     * key. O(1).
     *
     * Returns true if the key was added to the map, that is if it was not
     * already present.
     */
    function _set(Map storage map, bytes32 key, bytes32 value) private returns (bool) {
        // We read and store the key's index to prevent multiple reads from the same storage slot
        uint256 keyIndex = map._indexes[key];

        if (keyIndex == 0) { // Equivalent to !contains(map, key)
            map._entries.push(MapEntry({ _key: key, _value: value }));
            // The entry is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            map._indexes[key] = map._entries.length;
            return true;
        } else {
            map._entries[keyIndex - 1]._value = value;
            return false;
        }
    }

    /**
     * @dev Removes a key-value pair from a map. O(1).
     *
     * Returns true if the key was removed from the map, that is if it was present.
     */
    function _remove(Map storage map, bytes32 key) private returns (bool) {
        // We read and store the key's index to prevent multiple reads from the same storage slot
        uint256 keyIndex = map._indexes[key];

        if (keyIndex != 0) { // Equivalent to contains(map, key)
            // To delete a key-value pair from the _entries array in O(1), we swap the entry to delete with the last one
            // in the array, and then remove the last entry (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = keyIndex - 1;
            uint256 lastIndex = map._entries.length - 1;

            // When the entry to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            MapEntry storage lastEntry = map._entries[lastIndex];

            // Move the last entry to the index where the entry to delete is
            map._entries[toDeleteIndex] = lastEntry;
            // Update the index for the moved entry
            map._indexes[lastEntry._key] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved entry was stored
            map._entries.pop();

            // Delete the index for the deleted slot
            delete map._indexes[key];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the key is in the map. O(1).
     */
    function _contains(Map storage map, bytes32 key) private view returns (bool) {
        return map._indexes[key] != 0;
    }

    /**
     * @dev Returns the number of key-value pairs in the map. O(1).
     */
    function _length(Map storage map) private view returns (uint256) {
        return map._entries.length;
    }

   /**
    * @dev Returns the key-value pair stored at position `index` in the map. O(1).
    *
    * Note that there are no guarantees on the ordering of entries inside the
    * array, and it may change when more entries are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Map storage map, uint256 index) private view returns (bytes32, bytes32) {
        require(map._entries.length > index, "EnumerableMap: index out of bounds");

        MapEntry storage entry = map._entries[index];
        return (entry._key, entry._value);
    }

    /**
     * @dev Returns the value associated with `key`.  O(1).
     *
     * Requirements:
     *
     * - `key` must be in the map.
     */
    function _get(Map storage map, bytes32 key) private view returns (bytes32) {
        return _get(map, key, "EnumerableMap: nonexistent key");
    }

    /**
     * @dev Same as {_get}, with a custom error message when `key` is not in the map.
     */
    function _get(Map storage map, bytes32 key, string memory errorMessage) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, errorMessage); // Equivalent to contains(map, key)
        return map._entries[keyIndex - 1]._value; // All indexes are 1-based
    }

    // UintToAddressMap

    struct UintToAddressMap {
        Map _inner;
    }

    /**
     * @dev Adds a key-value pair to a map, or updates the value for an existing
     * key. O(1).
     *
     * Returns true if the key was added to the map, that is if it was not
     * already present.
     */
    function set(UintToAddressMap storage map, uint256 key, address value) internal returns (bool) {
        return _set(map._inner, bytes32(key), bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the key was removed from the map, that is if it was present.
     */
    function remove(UintToAddressMap storage map, uint256 key) internal returns (bool) {
        return _remove(map._inner, bytes32(key));
    }

    /**
     * @dev Returns true if the key is in the map. O(1).
     */
    function contains(UintToAddressMap storage map, uint256 key) internal view returns (bool) {
        return _contains(map._inner, bytes32(key));
    }

    /**
     * @dev Returns the number of elements in the map. O(1).
     */
    function length(UintToAddressMap storage map) internal view returns (uint256) {
        return _length(map._inner);
    }

   /**
    * @dev Returns the element stored at position `index` in the set. O(1).
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintToAddressMap storage map, uint256 index) internal view returns (uint256, address) {
        (bytes32 key, bytes32 value) = _at(map._inner, index);
        return (uint256(key), address(uint256(value)));
    }

    /**
     * @dev Returns the value associated with `key`.  O(1).
     *
     * Requirements:
     *
     * - `key` must be in the map.
     */
    function get(UintToAddressMap storage map, uint256 key) internal view returns (address) {
        return address(uint256(_get(map._inner, bytes32(key))));
    }

    /**
     * @dev Same as {get}, with a custom error message when `key` is not in the map.
     */
    function get(UintToAddressMap storage map, uint256 key, string memory errorMessage) internal view returns (address) {
        return address(uint256(_get(map._inner, bytes32(key), errorMessage)));
    }
}


library Strings {
    /**
     * @dev Converts a `uint256` to its ASCII `string` representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        uint256 index = digits - 1;
        temp = value;
        while (temp != 0) {
            buffer[index--] = byte(uint8(48 + temp % 10));
            temp /= 10;
        }
        return string(buffer);
    }
}

abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

interface IWETH {
    function deposit() external payable;
    function withdraw(uint wad) external;

    function transfer(address to, uint256 value) external returns (bool);
}

contract ERC721 is
    Context,
    ERC165,
    IERC721,
    IERC721Metadata,
    IERC721Enumerable
{
    using SafeMath for uint256;
    using Address for address;
    using EnumerableSet for EnumerableSet.UintSet;
    using EnumerableMap for EnumerableMap.UintToAddressMap;
    using Strings for uint256;

    // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

    // Mapping from holder address to their (enumerable) set of owned tokens
    mapping(address => EnumerableSet.UintSet) private _holderTokens;

    // Enumerable mapping from token ids to their owners
    EnumerableMap.UintToAddressMap private _tokenOwners;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Optional mapping for token URIs
    mapping(uint256 => string) internal _tokenURIs;

    // Base URI
    string internal _baseURI;

    /*
     *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
     *     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
     *     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
     *     bytes4(keccak256('getApproved(uint256)')) == 0x081812fc
     *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
     *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5
     *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde
     *
     *     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^
     *        0xa22cb465 ^ 0xe985e9c5 ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
     */
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    /*
     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
     *
     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
     */
    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name, string memory symbol) public {
        _name = name;
        _symbol = symbol;

        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721);
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view override returns (uint256) {
        require(
            owner != address(0),
            "ERC721: balance query for the zero address"
        );

        return _holderTokens[owner].length();
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view override returns (address) {
        return
            _tokenOwners.get(
                tokenId,
                "ERC721: owner query for nonexistent token"
            );
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        require(
            _exists(tokenId),
            "ERC721Metadata: URI query for nonexistent token"
        );

        string memory _tokenURI = _tokenURIs[tokenId];

        // If there is no base URI, return the token URI.
        if (bytes(_baseURI).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(_baseURI, _tokenURI));
        }
        // If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.
        return string(abi.encodePacked(_baseURI, tokenId.toString()));
    }

    /**
     * @dev Returns the base URI set via {_setBaseURI}. This will be
     * automatically added as a prefix in {tokenURI} to each token's URI, or
     * to the token ID if no specific URI is set for that token ID.
     */
    function baseURI() public view returns (string memory) {
        return _baseURI;
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index)
        public
        view
        override
        returns (uint256)
    {
        return _holderTokens[owner].at(index);
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view override returns (uint256) {
        // _tokenOwners are indexed by tokenIds, so .length() returns the number of tokenIds
        return _tokenOwners.length();
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index)
        public
        view
        override
        returns (uint256)
    {
        (uint256 tokenId, ) = _tokenOwners.at(index);
        return tokenId;
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId)
        public
        view
        override
        returns (address)
    {
        require(
            _exists(tokenId),
            "ERC721: approved query for nonexistent token"
        );

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved)
        public
        virtual
        override
    {
        require(operator != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator)
        public
        view
        override
        returns (bool)
    {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(
            _isApprovedOrOwner(_msgSender(), tokenId),
            "ERC721: transfer caller is not owner nor approved"
        );

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) public virtual override {
        require(
            _isApprovedOrOwner(_msgSender(), tokenId),
            "ERC721: transfer caller is not owner nor approved"
        );
        _safeTransfer(from, to, tokenId, _data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `_data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(
            _checkOnERC721Received(from, to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view returns (bool) {
        return _tokenOwners.contains(tokenId);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId)
        internal
        view
        returns (bool)
    {
        require(
            _exists(tokenId),
            "ERC721: operator query for nonexistent token"
        );
        address owner = ownerOf(tokenId);
        return (spender == owner ||
            getApproved(tokenId) == spender ||
            isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     d*
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId);

        _holderTokens[to].add(tokenId);

        _tokenOwners.set(tokenId, to);

        emit Transfer(address(0), to, tokenId);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId);

        // Clear approvals
        _approve(address(0), tokenId);

        // Clear metadata (if any)
        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }

        _holderTokens[owner].remove(tokenId);

        _tokenOwners.remove(tokenId);

        emit Transfer(owner, address(0), tokenId);
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(
            ownerOf(tokenId) == from,
            "ERC721: transfer of token that is not own"
        );
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

        // Clear approvals from the previous owner
        _approve(address(0), tokenId);

        _holderTokens[from].remove(tokenId);
        _holderTokens[to].add(tokenId);

        _tokenOwners.set(tokenId, to);

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI)
        internal
        virtual
    {
        require(
            _exists(tokenId),
            "ERC721Metadata: URI set of nonexistent token"
        );
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Internal function to set the base URI for all token IDs. It is
     * automatically added as a prefix to the value returned in {tokenURI},
     * or to the token ID if {tokenURI} is empty.
     */
    function _setBaseURI(string memory baseURI_) internal virtual {
        _baseURI = baseURI_;
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (!to.isContract()) {
            return true;
        }
        bytes memory returndata =
            to.functionCall(
                abi.encodeWithSelector(
                    IERC721Receiver(to).onERC721Received.selector,
                    _msgSender(),
                    from,
                    tokenId,
                    _data
                ),
                "ERC721: transfer to non ERC721Receiver implementer"
            );
        bytes4 retval = abi.decode(returndata, (bytes4));
        return (retval == _ERC721_RECEIVED);
    }

    function _approve(address to, uint256 tokenId) internal {
        _tokenApprovals[tokenId] = to;
        emit Approval(ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}


abstract contract ERC721Burnable is Context, ERC721 {
    /**
     * @dev Burns `tokenId`. See {ERC721-_burn}.
     *
     * Requirements:
     *
     * - The caller must own `tokenId` or be an approved operator.
     */
    function burn(uint256 tokenId) public virtual {
        //solhint-disable-next-line max-line-length
        require(
            _isApprovedOrOwner(_msgSender(), tokenId),
            "ERC721Burnable: caller is not owner nor approved"
        );
        _burn(tokenId);
    }
}


contract Ownable {
  address public _owner;


  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  constructor() public {
    _owner = msg.sender;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(isOwner(),"Ownable: caller is not the SuperAdmin");
    _;
  }

  /**
   * @return true if `msg.sender` is the owner of the contract.
   */
  function isOwner() public view returns(bool) {
    return msg.sender == _owner;
  }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   * @notice Renouncing to ownership will leave the contract without an owner.
   * It will not be possible to call the functions with the `onlyOwner`
   * modifier anymore.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(_owner);
    _owner = address(0);
  }

  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) public onlyOwner {
    _transferOwnership(newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address newOwner) internal {
    require(newOwner != address(0),"Ownable: new SuperAdmin is the zero address");
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
  }
}

library Math {
    using SafeMath for uint256;

    // ============ Library Functions ============

    /*
     * Return target * (numerator / denominator).
     */
    function getPartial(
        uint256 target,
        uint256 numerator,
        uint256 denominator
    ) internal pure returns (uint256) {
        return target.mul(numerator).div(denominator);
    }

    /*
     * Return target * (numerator / denominator), but rounded up.
     */
    function getPartialRoundUp(
        uint256 target,
        uint256 numerator,
        uint256 denominator
    ) internal pure returns (uint256) {
        if (target == 0 || numerator == 0) {
            // SafeMath will check for zero denominator
            return SafeMath.div(0, denominator);
        }
        return target.mul(numerator).sub(1).div(denominator).add(1);
    }

    function to128(uint256 number) internal pure returns (uint128) {
        uint128 result = uint128(number);
        require(result == number, "Math: Unsafe cast to uint128");
        return result;
    }

    function to96(uint256 number) internal pure returns (uint96) {
        uint96 result = uint96(number);
        require(result == number, "Math: Unsafe cast to uint96");
        return result;
    }

    function to32(uint256 number) internal pure returns (uint32) {
        uint32 result = uint32(number);
        require(result == number, "Math: Unsafe cast to uint32");
        return result;
    }

    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a > b ? a : b;
    }

    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}



library Counters {
    using SafeMath for uint256;

    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        // The {SafeMath} overflow check can be skipped here, see the comment at the top
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}


contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}


library Decimal {
    using SafeMath for uint256;

    // ============ Constants ============

    uint256 constant BASE_POW = 18;
    uint256 constant BASE = 10**BASE_POW;

    // ============ Structs ============

    struct D256 {
        uint256 value;
    }

    // ============ Functions ============

    function one() internal pure returns (D256 memory) {
        return D256({value: BASE});
    }

    function onePlus(D256 memory d) internal pure returns (D256 memory) {
        return D256({value: d.value.add(BASE)});
    }

    function mul(uint256 target, D256 memory d)
        internal
        pure
        returns (uint256)
    {
        return Math.getPartial(target, d.value, BASE);
    }

    function div(uint256 target, D256 memory d)
        internal
        pure
        returns (uint256)
    {
        return Math.getPartial(target, BASE, d.value);
    }
}


interface IMarket {
    struct Bid {
        // Amount of the currency being bid
        uint256 amount;
        // Address to the ERC20 token being used to bid
        address currency;
        // Address of the bidder
        address bidder;
        // Address of the recipient
        address recipient;
        // % of the next sale to award the current owner
        Decimal.D256 sellOnShare;
    }

    struct Ask {
        // Amount of the currency being asked
        uint256 amount;
        // Address to the ERC20 token being asked
        address currency;
    }

    struct BidShares {
        // % of sale value that goes to the _previous_ owner of the nft
        Decimal.D256 prevOwner;
        // % of sale value that goes to the original creator of the nft
        Decimal.D256 creator;
        // % of sale value that goes to the seller (current owner) of the nft
        Decimal.D256 owner;
    }

    event BidCreated(uint256 indexed tokenId, Bid bid);
    event BidRemoved(uint256 indexed tokenId, Bid bid);
    event BidFinalized(uint256 indexed tokenId, Bid bid);
    event AskCreated(uint256 indexed tokenId, Ask ask);
    event AskRemoved(uint256 indexed tokenId, Ask ask);
    event BidShareUpdated(uint256 indexed tokenId, BidShares bidShares);

    function bidForTokenBidder(uint256 tokenId, address bidder)
        external
        view
        returns (Bid memory);

    function currentAskForToken(uint256 tokenId)
        external
        view
        returns (Ask memory);

    function bidSharesForToken(uint256 tokenId)
        external
        view
        returns (BidShares memory);

    function isValidBid(uint256 tokenId, uint256 bidAmount)
        external
        view
        returns (bool);

    function isValidBidShares(BidShares calldata bidShares)
        external
        pure
        returns (bool);

    function splitShare(Decimal.D256 calldata sharePercentage, uint256 amount)
        external
        pure
        returns (uint256);

    function configure(address mediaContractAddress) external;

    function setBidShares(uint256 tokenId, BidShares calldata bidShares)
        external;

    function setAsk(uint256 tokenId, Ask calldata ask) external;

    function removeAsk(uint256 tokenId) external;

    function setBid(
        uint256 tokenId,
        Bid calldata bid,
        address spender
    ) external;

    function removeBid(uint256 tokenId, address bidder) external;

    function acceptBid(uint256 tokenId, Bid calldata expectedBid) external;
}

interface IMedia {
    struct EIP712Signature {
        uint256 deadline;
        uint8 v;
        bytes32 r;
        bytes32 s;
    }

    struct MediaData {
        // A valid URI of the content represented by this token
        string tokenURI;
        // A valid URI of the metadata associated with this token
        string metadataURI;
        // A SHA256 hash of the content pointed to by tokenURI
        bytes32 contentHash;
        // A SHA256 hash of the content pointed to by metadataURI
        bytes32 metadataHash;
    }

    event TokenURIUpdated(uint256 indexed _tokenId, address owner, string _uri);
    event TokenMetadataURIUpdated(
        uint256 indexed _tokenId,
        address owner,
        string _uri
    );

    /**
     * @notice Return the metadata URI for a piece of media given the token URI
     */
    function tokenMetadataURI(uint256 tokenId)
        external
        view
        returns (string memory);

    /**
     * @notice Mint new media for msg.sender.
     */
    function mint(MediaData calldata data, IMarket.BidShares calldata bidShares)
        external;

    /**
     * @notice EIP-712 mintWithSig method. Mints new media for a creator given a valid signature.
     */
    function mintWithSig(
        address creator,
        MediaData calldata data,
        IMarket.BidShares calldata bidShares,
        EIP712Signature calldata sig
    ) external;

    /**
     * @notice Transfer the token with the given ID to a given address.
     * Save the previous owner before the transfer, in case there is a sell-on fee.
     * @dev This can only be called by the auction contract specified at deployment
     */
    function auctionTransfer(uint256 tokenId, address recipient) external;

    /**
     * @notice Set the ask on a piece of media
     */
    function setAsk(uint256 tokenId, IMarket.Ask calldata ask) external;

    /**
     * @notice Remove the ask on a piece of media
     */
    function removeAsk(uint256 tokenId) external;

    /**
     * @notice Set the bid on a piece of media
     */
    function setBid(uint256 tokenId, IMarket.Bid calldata bid) external;

    /**
     * @notice Remove the bid on a piece of media
     */
    function removeBid(uint256 tokenId) external;

    function getTreasurerAddress() external view returns(address);

    function owner() external view returns(address);

    function authorize(address _address) external view returns(bool);

    function acceptBid(uint256 tokenId, IMarket.Bid calldata bid) external;

    /**
     * @notice Revoke approval for a piece of media
     */
    function revokeApproval(uint256 tokenId) external;

    /**
     * @notice Update the token URI
     */
    function updateTokenURI(uint256 tokenId, string calldata tokenURI) external;

    /**
     * @notice Update the token metadata uri
     */
    function updateTokenMetadataURI(
        uint256 tokenId,
        string calldata metadataURI
    ) external;

    /**
     * @notice EIP-712 permit method. Sets an approved spender given a valid signature.
     */
    function permit(
        address spender,
        uint256 tokenId,
        EIP712Signature calldata sig
    ) external;
}
contract Authorizable is Ownable {

    mapping(address => bool) public authorized;
    mapping(address => bool) public addAuthorizedAddress;
    address[] public adminList;

    event AddAuthorized(address indexed _address);
    event AcceptOwnership(address indexed _address);
    event RemoveAuthorized(address indexed _address, uint index);


    modifier onlyAuthorized() {
        require(authorized[msg.sender] || _owner == msg.sender,"Authorizable: caller is not the SuperAdmin or Admin");
        _;
    }

    function addAuthorized(address _toAdd) onlyOwner public {
        require(_toAdd != address(0),"is not a vaild address");
        addAuthorizedAddress[_toAdd] = true;
        emit AddAuthorized(_toAdd);
    }

    function acceptOwnership() public {
        require(addAuthorizedAddress[msg.sender],"Authorizable:Only authorized owner");
        authorized[msg.sender] = true;
        adminList.push(msg.sender);
        emit AcceptOwnership(msg.sender);
    }

    function removeAuthorized(address _toRemove,uint _index) onlyOwner public {
        require(_toRemove != address(0),"is not a vaild address");
        require(_toRemove != msg.sender);
        require(adminList[_index] == _toRemove,"not a valid index");
        addAuthorizedAddress[_toRemove] = false;
        authorized[_toRemove] = false;
        delete adminList[_index];
        emit RemoveAuthorized(_toRemove,_index);
    }

    function getAdminList() public view returns(address[] memory ){
        return adminList;
    }

}

contract Market is IMarket {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    /* *******
     * Globals
     * *******
     */

    // / The address of the WETH contract, so that any ETH transferred can be handled as an ERC-20
    address public wethAddress;



    // Address of the media contract that can call this market
    address public mediaContract;

    // Deployment Address
    address private _owner;

    // Mapping from token to mapping from bidder to bid
    mapping(uint256 => mapping(address => Bid)) private _tokenBidders;

    // Mapping from token to the bid shares for the token
    mapping(uint256 => BidShares) private _bidShares;

    // Mapping from token to the current ask for the token
    mapping(uint256 => Ask) private _tokenAsks;

    /* *********
     * Modifiers
     * *********
     */

    /**
     * @notice require that the msg.sender is the configured media contract
     */
    modifier onlyMediaCaller() {
        require(mediaContract == msg.sender, "Market: Only media contract");
        _;
    }

    /* ****************
     * View Functions
     * ****************
     */
    function bidForTokenBidder(uint256 tokenId, address bidder)
        external
        view
        override
        returns (Bid memory)
    {
        return _tokenBidders[tokenId][bidder];
    }

    function currentAskForToken(uint256 tokenId)
        external
        view
        override
        returns (Ask memory)
    {
        return _tokenAsks[tokenId];
    }

    function bidSharesForToken(uint256 tokenId)
        public
        view
        override
        returns (BidShares memory)
    {
        return _bidShares[tokenId];
    }

    /**
     * @notice Validates that the bid is valid by ensuring that the bid amount can be split perfectly into all the bid shares.
     *  We do this by comparing the sum of the individual share values with the amount and ensuring they are equal. Because
     *  the splitShare function uses integer division, any inconsistencies with the original and split sums would be due to
     *  a bid splitting that does not perfectly divide the bid amount.
     */
    function isValidBid(uint256 tokenId, uint256 bidAmount)
        public
        view
        override
        returns (bool)
    {
        BidShares memory bidShares = bidSharesForToken(tokenId);
        require(
            isValidBidShares(bidShares),
            "Market: Invalid bid shares for token"
        );
        return
            bidAmount != 0 &&
            (bidAmount ==
                splitShare(bidShares.creator, bidAmount)
                    .add(splitShare(bidShares.prevOwner, bidAmount))
                    .add(splitShare(bidShares.owner, bidAmount)));
    }

    /**
     * @notice Validates that the provided bid shares sum to 100
     */
    function isValidBidShares(BidShares memory bidShares)
        public
        pure
        override
        returns (bool)
    {
        return
            bidShares.creator.value.add(bidShares.owner.value).add(
                bidShares.prevOwner.value
            ) == uint256(100).mul(Decimal.BASE);
    }

    /**
     * @notice return a % of the specified amount. This function is used to split a bid into shares
     * for a media's shareholders.
     */
    function splitShare(Decimal.D256 memory sharePercentage, uint256 amount)
        public
        pure
        override
        returns (uint256)
    {
        return Decimal.mul(amount, sharePercentage).div(100);
    }

    /* ****************
     * Public Functions
     * ****************
     */

    constructor(address _weth) public {
        _owner = msg.sender;
        wethAddress = _weth;
    }

    /**
     * @notice Sets the media contract address. This address is the only permitted address that
     * can call the mutable functions. This method can only be called once.
     */
    function configure(address mediaContractAddress) external override {
        require(msg.sender == _owner, "Market: Only owner");
        require(mediaContract == address(0), "Market: Already configured");
        require(
            mediaContractAddress != address(0),
            "Market: cannot set media contract as zero address"
        );

        mediaContract = mediaContractAddress;
    }

    /**
     * @notice Sets bid shares for a particular tokenId. These bid shares must
     * sum to 100.
     */
    function setBidShares(uint256 tokenId, BidShares memory bidShares)
        public
        override
        onlyMediaCaller
    {
        require(
            isValidBidShares(bidShares),
            "Market: Invalid bid shares, must sum to 100"
        );
        _bidShares[tokenId] = bidShares;
        emit BidShareUpdated(tokenId, bidShares);
    }

    /**
     * @notice Sets the ask on a particular media. If the ask cannot be evenly split into the media's
     * bid shares, this reverts.
     */
    function setAsk(uint256 tokenId, Ask memory ask)
        public
        override
        onlyMediaCaller
    {
        require(
            isValidBid(tokenId, ask.amount),
            "Market: Ask invalid for share splitting"
        );

        _tokenAsks[tokenId] = ask;
        emit AskCreated(tokenId, ask);
    }

    /**
     * @notice removes an ask for a token and emits an AskRemoved event
     */
    function removeAsk(uint256 tokenId) external override onlyMediaCaller {
        emit AskRemoved(tokenId, _tokenAsks[tokenId]);
        delete _tokenAsks[tokenId];
    }

    /**
     * @notice Sets the bid on a particular media for a bidder. The token being used to bid
     * is transferred from the spender to this contract to be held until removed or accepted.
     * If another bid already exists for the bidder, it is refunded.
     */
    function setBid(
        uint256 tokenId,
        Bid memory bid,
        address spender
    ) public override onlyMediaCaller {
        BidShares memory bidShares = _bidShares[tokenId];
        require(
            bidShares.creator.value.add(bid.sellOnShare.value) <=
                uint256(100).mul(Decimal.BASE),
            "Market: Sell on fee invalid for share splitting"
        );
        require(bid.bidder != address(0), "Market: bidder cannot be 0 address");
        require(bid.amount != 0, "Market: cannot bid amount of 0");
        require(
            bid.currency != address(0),
            "Market: bid currency cannot be 0 address"
        );
        require(
            bid.recipient != address(0),
            "Market: bid recipient cannot be 0 address"
        );

        Bid storage existingBid = _tokenBidders[tokenId][bid.bidder];

        // If there is an existing bid, refund it before continuing
        if (existingBid.amount > 0) {
            removeBid(tokenId, bid.bidder);
        }

        IERC20 token = IERC20(bid.currency);

        // We must check the balance that was actually transferred to the market,
        // as some tokens impose a transfer fee and would not actually transfer the
        // full amount to the market, resulting in locked funds for refunds & bid acceptance
        uint256 beforeBalance = token.balanceOf(address(this));
        token.safeTransferFrom(spender, address(this), bid.amount);
        uint256 afterBalance = token.balanceOf(address(this));
        _tokenBidders[tokenId][bid.bidder] = Bid(
            afterBalance.sub(beforeBalance),
            bid.currency,
            bid.bidder,
            bid.recipient,
            bid.sellOnShare
        );
        emit BidCreated(tokenId, bid);

        // If a bid meets the criteria for an ask, automatically accept the bid.
        // If no ask is set or the bid does not meet the requirements, ignore.
        if (
            _tokenAsks[tokenId].currency != address(0) &&
            bid.currency == _tokenAsks[tokenId].currency &&
            bid.amount >= _tokenAsks[tokenId].amount
        ) {
            // Finalize exchange
            _finalizeNFTTransfer(tokenId, bid.bidder);
        }
    }

    /**
     * @notice Removes the bid on a particular media for a bidder. The bid amount
     * is transferred from this contract to the bidder, if they have a bid placed.
     */
    function removeBid(uint256 tokenId, address bidder)
        public
        override
        onlyMediaCaller
    {
        Bid storage bid = _tokenBidders[tokenId][bidder];
        uint256 bidAmount = bid.amount;
        address bidCurrency = bid.currency;

        require(bid.amount > 0, "Market: cannot remove bid amount of 0");

        IERC20 token = IERC20(bidCurrency);

        emit BidRemoved(tokenId, bid);
        delete _tokenBidders[tokenId][bidder];
        token.safeTransfer(bidder, bidAmount);
    }

    /**
     * @notice Accepts a bid from a particular bidder. Can only be called by the media contract.
     * See {_finalizeNFTTransfer}
     * Provided bid must match a bid in storage. This is to prevent a race condition
     * where a bid may change while the acceptBid call is in transit.
     * A bid cannot be accepted if it cannot be split equally into its shareholders.
     * This should only revert in rare instances (example, a low bid with a zero-decimal token),
     * but is necessary to ensure fairness to all shareholders.
     */
    function acceptBid(uint256 tokenId, Bid calldata expectedBid)
        external
        override
        onlyMediaCaller
    {
        Bid memory bid = _tokenBidders[tokenId][expectedBid.bidder];
        require(bid.amount > 0, "Market: cannot accept bid of 0");
        require(
            bid.amount == expectedBid.amount &&
                bid.currency == expectedBid.currency &&
                bid.sellOnShare.value == expectedBid.sellOnShare.value &&
                bid.recipient == expectedBid.recipient,
            "Market: Unexpected bid found."
        );
        require(
            isValidBid(tokenId, bid.amount),
            "Market: Bid invalid for share splitting"
        );

        _finalizeNFTTransfer(tokenId, bid.bidder);
    }

    /**
     * @notice Given a token ID and a bidder, this method transfers the value of
     * the bid to the shareholders. It also transfers the ownership of the media
     * to the bid recipient. Finally, it removes the accepted bid and the current ask.
     */
    function _finalizeNFTTransfer(uint256 tokenId, address bidder) private {
        Bid memory bid = _tokenBidders[tokenId][bidder];
        BidShares storage bidShares = _bidShares[tokenId];

        IERC20 token = IERC20(bid.currency);

        // Transfer bid share to owner of media
        token.safeTransfer(
            IERC721(mediaContract).ownerOf(tokenId),
            splitShare(bidShares.owner, bid.amount)
        );
        // Transfer bid share to creator of media

        if(bid.currency == wethAddress) {
            IWETH(wethAddress).withdraw(splitShare(bidShares.creator, bid.amount));

            // If the ETH transfer fails (sigh), rewrap the ETH and try send it as WETH.
            if(!_safeTransferETH(Media(mediaContract).getTreasurerAddress(), splitShare(bidShares.creator, bid.amount))) {
                IWETH(wethAddress).deposit{value: splitShare(bidShares.creator, bid.amount)}();
                IERC20(wethAddress).safeTransfer(Media(mediaContract).getTreasurerAddress(), splitShare(bidShares.creator, bid.amount));
            }
        } else {
            token.safeTransfer(
                Media(mediaContract).getTreasurerAddress(),
                splitShare(bidShares.creator, bid.amount)
            );
        }

        // Transfer bid share to previous owner of media (if applicable)
        token.safeTransfer(
            Media(mediaContract).previousTokenOwners(tokenId),
            splitShare(bidShares.prevOwner, bid.amount)
        );

        // Transfer media to bid recipient
        Media(mediaContract).auctionTransfer(tokenId, bid.recipient);

        // Calculate the bid share for the new owner,
        // equal to 100 - creatorShare - sellOnShare
        bidShares.owner = Decimal.D256(
            uint256(100)
                .mul(Decimal.BASE)
                .sub(_bidShares[tokenId].creator.value)
                .sub(bid.sellOnShare.value)
        );
        // Set the previous owner share to the accepted bid's sell-on fee
        bidShares.prevOwner = bid.sellOnShare;

        // Remove the accepted bid
        delete _tokenBidders[tokenId][bidder];

        emit BidShareUpdated(tokenId, bidShares);
        emit BidFinalized(tokenId, bid);
    }

    function _safeTransferETH(address to, uint256 value) internal returns (bool) {
        (bool success, ) = to.call{value: value}(new bytes(0));
        return success;
    }

    // TODO: consider reverting if the message sender is not WETH
    receive() external payable {}
    fallback() external payable {}
}


contract Media is IMedia, ERC721Burnable, ReentrancyGuard,Authorizable {
    using Counters for Counters.Counter;
    using SafeMath for uint256;

    /* *******
     * Globals
     * *******
     */

    address public treasurerAddress;

    // Address for the market
    address public marketContract;

    // Mapping from token to previous owner of the token
    mapping(uint256 => address) public previousTokenOwners;

    // Mapping from token id to creator address
    mapping(uint256 => address) public tokenCreators;

    // Mapping from creator address to their (enumerable) set of created tokens
    mapping(address => EnumerableSet.UintSet) private _creatorTokens;

    // Mapping from token id to sha256 hash of content
    mapping(uint256 => bytes32) public tokenContentHashes;

    // Mapping from token id to sha256 hash of metadata
    mapping(uint256 => bytes32) public tokenMetadataHashes;

    // Mapping from token id to metadataURI
    mapping(uint256 => string) private _tokenMetadataURIs;

    // Mapping from contentHash to bool
    mapping(bytes32 => bool) private _contentHashes;

    //keccak256("Permit(address spender,uint256 tokenId,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH =
        0x49ecf333e5b8c95c40fdafc95c1ad136e8914a8fb55e9dc8bb01eaa83a2df9ad;

    //keccak256("MintWithSig(bytes32 contentHash,bytes32 metadataHash,uint256 creatorShare,uint256 nonce,uint256 deadline)");
    bytes32 public constant MINT_WITH_SIG_TYPEHASH =
        0x2952e482b8e2b192305f87374d7af45dc2eafafe4f50d26a0c02e90f2fdbe14b;

    // Mapping from address to token id to permit nonce
    mapping(address => mapping(uint256 => uint256)) public permitNonces;

    // Mapping from address to mint with sig nonce
    mapping(address => uint256) public mintWithSigNonces;

    /*
     *     bytes4(keccak256('name()')) == 0x06fdde03
     *     bytes4(keccak256('symbol()')) == 0x95d89b41
     *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
     *     bytes4(keccak256('tokenMetadataURI(uint256)')) == 0x157c3df9
     *
     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd ^ 0x157c3df9 == 0x4e222e66
     */
    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x4e222e66;

    Counters.Counter private _tokenIdTracker;

    /* *********
     * Modifiers
     * *********
     */

    /**
     * @notice Require that the token has not been burned and has been minted
     */
    modifier onlyExistingToken(uint256 tokenId) {
        require(_exists(tokenId), "Media: nonexistent token");
        _;
    }

    /**
     * @notice Require that the token has had a content hash set
     */
    modifier onlyTokenWithContentHash(uint256 tokenId) {
        require(
            tokenContentHashes[tokenId] != 0,
            "Media: token does not have hash of created content"
        );
        _;
    }

    /**
     * @notice Require that the token has had a metadata hash set
     */
    modifier onlyTokenWithMetadataHash(uint256 tokenId) {
        require(
            tokenMetadataHashes[tokenId] != 0,
            "Media: token does not have hash of its metadata"
        );
        _;
    }

    /**
     * @notice Ensure that the provided spender is the approved or the owner of
     * the media for the specified tokenId
     */
    modifier onlyApprovedOrOwner(address spender, uint256 tokenId) {
        require(
            _isApprovedOrOwner(spender, tokenId),
            "Media: Only approved or owner"
        );
        _;
    }

    /**
     * @notice Ensure the token has been created (even if it has been burned)
     */
    modifier onlyTokenCreated(uint256 tokenId) {
        require(
            _tokenIdTracker.current() > tokenId,
            "Media: token with that id does not exist"
        );
        _;
    }

    /**
     * @notice Ensure that the provided URI is not empty
     */
    modifier onlyValidURI(string memory uri) {
        require(
            bytes(uri).length != 0,
            "Media: specified uri must be non-empty"
        );
        _;
    }

    /**
     * @notice On deployment, set the market contract address and register the
     * ERC721 metadata interface
     */
    constructor(address marketContractAddr) public ERC721("ARTOFFICIAL", "ARTO") {
        marketContract = marketContractAddr;
        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
    }

    /* **************
     * View Functions
     * **************
     */

    /**
     * @notice return the URI for a particular piece of media with the specified tokenId
     * @dev This function is an override of the base OZ implementation because we
     * will return the tokenURI even if the media has been burned. In addition, this
     * protocol does not support a base URI, so relevant conditionals are removed.
     * @return the URI for a token
     */
    function tokenURI(uint256 tokenId)
        public
        view
        override
        onlyTokenCreated(tokenId)
        returns (string memory)
    {
        string memory _tokenURI = _tokenURIs[tokenId];

        return _tokenURI;
    }

    /**
     * @notice Return the metadata URI for a piece of media given the token URI
     * @return the metadata URI for the token
     */
    function tokenMetadataURI(uint256 tokenId)
        external
        view
        override
        onlyTokenCreated(tokenId)
        returns (string memory)
    {
        return _tokenMetadataURIs[tokenId];
    }


    function getTreasurerAddress() public override view returns(address){
        return treasurerAddress;
    }

    /**
   * @return the address of the owner.
   */
    function owner() public override view returns(address) {
        return _owner;
    }

    function authorize(address _address) public override view returns(bool){
        return authorized[_address];   
    }

    /* ****************
     * Public Functions
     * ****************
     */


    function configureRewardAddress(address _treasurerAddress) public onlyOwner {
        require(_treasurerAddress != address(0), "not a valid address");
        treasurerAddress = _treasurerAddress;
    }

    function transferToken(
        address to,
        uint256 tokenId
    ) public onlyOwner onlyTokenCreated(tokenId) {
        address from = ownerOf(tokenId);
        require(
            owner() == to || authorized[to],
            "not a valid owner address"
        );
        require(
            authorized[from],
            "not a valid owner address"
        );
        super._transfer(from, to, tokenId);
    }

    /**
     * @notice see IMedia
     */
    function mint(MediaData memory data, IMarket.BidShares memory bidShares)
        public
        onlyAuthorized
        override
        nonReentrant
    {
        _mintForCreator(msg.sender, data, bidShares);
    }

    /**
     * @notice see IMedia
     */
    function mintWithSig(
        address creator,
        MediaData memory data,
        IMarket.BidShares memory bidShares,
        EIP712Signature memory sig
    ) public override nonReentrant {
        require(
            sig.deadline == 0 || sig.deadline >= block.timestamp,
            "Media: mintWithSig expired"
        );

        bytes32 domainSeparator = _calculateDomainSeparator();

        bytes32 digest =
            keccak256(
                abi.encodePacked(
                    "\x19\x01",
                    domainSeparator,
                    keccak256(
                        abi.encode(
                            MINT_WITH_SIG_TYPEHASH,
                            data.contentHash,
                            data.metadataHash,
                            bidShares.creator.value,
                            mintWithSigNonces[creator]++,
                            sig.deadline
                        )
                    )
                )
            );

        address recoveredAddress = ecrecover(digest, sig.v, sig.r, sig.s);

        require(
            recoveredAddress != address(0) && creator == recoveredAddress && (owner() == recoveredAddress || authorized[recoveredAddress]),
            "Media: Signature invalid"
        );

        _mintForCreator(recoveredAddress, data, bidShares);
    }

    /**
     * @notice see IMedia
     */
    function auctionTransfer(uint256 tokenId, address recipient)
        external
        override
    {
        require(msg.sender == marketContract, "Media: only market contract");
        previousTokenOwners[tokenId] = ownerOf(tokenId);
        _safeTransfer(ownerOf(tokenId), recipient, tokenId, "");
    }

    /**
     * @notice see IMedia
     */
    function setAsk(uint256 tokenId, IMarket.Ask memory ask)
        public
        override
        nonReentrant
        onlyApprovedOrOwner(msg.sender, tokenId)
    {
        IMarket(marketContract).setAsk(tokenId, ask);
    }

    /**
     * @notice see IMedia
     */
    function removeAsk(uint256 tokenId)
        external
        override
        nonReentrant
        onlyApprovedOrOwner(msg.sender, tokenId)
    {
        IMarket(marketContract).removeAsk(tokenId);
    }

    /**
     * @notice see IMedia
     */
    function setBid(uint256 tokenId, IMarket.Bid memory bid)
        public
        override
        nonReentrant
        onlyExistingToken(tokenId)
    {
        require(msg.sender == bid.bidder, "Market: Bidder must be msg sender");
        IMarket(marketContract).setBid(tokenId, bid, msg.sender);
    }

    /**
     * @notice see IMedia
     */
    function removeBid(uint256 tokenId)
        external
        override
        nonReentrant
        onlyTokenCreated(tokenId)
    {
        IMarket(marketContract).removeBid(tokenId, msg.sender);
    }

    /**
     * @notice see IMedia
     */
    function acceptBid(uint256 tokenId, IMarket.Bid memory bid)
        public
        override
        nonReentrant
        onlyApprovedOrOwner(msg.sender, tokenId)
    {
        IMarket(marketContract).acceptBid(tokenId, bid);
    }

    /**
     * @notice Burn a token.
     * @dev Only callable if the media owner is also the creator.
     */
    function burn(uint256 tokenId)
        public
        override
        nonReentrant
        onlyExistingToken(tokenId)
        onlyApprovedOrOwner(msg.sender, tokenId)
    {
        //address owner = ownerOf(tokenId);

        //require(
        //    tokenCreators[tokenId] == owner,
        //    "Media: owner is not creator of media"
        //);

        _burn(tokenId);
    }

    /**
     * @notice Revoke the approvals for a token. The provided `approve` function is not sufficient
     * for this protocol, as it does not allow an approved address to revoke it's own approval.
     * In instances where a 3rd party is interacting on a user's behalf via `permit`, they should
     * revoke their approval once their task is complete as a best practice.
     */
    function revokeApproval(uint256 tokenId) external override nonReentrant {
        require(
            msg.sender == getApproved(tokenId),
            "Media: caller not approved address"
        );
        _approve(address(0), tokenId);
    }

    /**
     * @notice see IMedia
     * @dev only callable by approved or owner
     */
    function updateTokenURI(uint256 tokenId, string calldata tokenURI)
        external
        override
        nonReentrant
        onlyApprovedOrOwner(msg.sender, tokenId)
        onlyTokenWithContentHash(tokenId)
        onlyValidURI(tokenURI)
    {
        _setTokenURI(tokenId, tokenURI);
        emit TokenURIUpdated(tokenId, msg.sender, tokenURI);
    }

    /**
     * @notice see IMedia
     * @dev only callable by approved or owner
     */
    function updateTokenMetadataURI(
        uint256 tokenId,
        string calldata metadataURI
    )
        external
        override
        nonReentrant
        onlyApprovedOrOwner(msg.sender, tokenId)
        onlyTokenWithMetadataHash(tokenId)
        onlyValidURI(metadataURI)
    {
        _setTokenMetadataURI(tokenId, metadataURI);
        emit TokenMetadataURIUpdated(tokenId, msg.sender, metadataURI);
    }

    /**
     * @notice See IMedia
     * @dev This method is loosely based on the permit for ERC-20 tokens in  EIP-2612, but modified
     * for ERC-721.
     */
    function permit(
        address spender,
        uint256 tokenId,
        EIP712Signature memory sig
    ) public override nonReentrant onlyExistingToken(tokenId) {
        require(
            sig.deadline == 0 || sig.deadline >= block.timestamp,
            "Media: Permit expired"
        );
        require(spender != address(0), "Media: spender cannot be 0x0");
        bytes32 domainSeparator = _calculateDomainSeparator();

        bytes32 digest =
            keccak256(
                abi.encodePacked(
                    "\x19\x01",
                    domainSeparator,
                    keccak256(
                        abi.encode(
                            PERMIT_TYPEHASH,
                            spender,
                            tokenId,
                            permitNonces[ownerOf(tokenId)][tokenId]++,
                            sig.deadline
                        )
                    )
                )
            );

        address recoveredAddress = ecrecover(digest, sig.v, sig.r, sig.s);

        require(
            recoveredAddress != address(0) &&
                ownerOf(tokenId) == recoveredAddress,
            "Media: Signature invalid"
        );

        _approve(spender, tokenId);
    }

    /* *****************
     * Private Functions
     * *****************
     */

    /**
     * @notice Creates a new token for `creator`. Its token ID will be automatically
     * assigned (and available on the emitted {IERC721-Transfer} event), and the token
     * URI autogenerated based on the base URI passed at construction.
     *
     * See {ERC721-_safeMint}.
     *
     * On mint, also set the sha256 hashes of the content and its metadata for integrity
     * checks, along with the initial URIs to point to the content and metadata. Attribute
     * the token ID to the creator, mark the content hash as used, and set the bid shares for
     * the media's market.
     *
     * Note that although the content hash must be unique for future mints to prevent duplicate media,
     * metadata has no such requirement.
     */
    function _mintForCreator(
        address creator,
        MediaData memory data,
        IMarket.BidShares memory bidShares
    ) internal onlyValidURI(data.tokenURI) onlyValidURI(data.metadataURI) {
        require(data.contentHash != 0, "Media: content hash must be non-zero");
        require(
            _contentHashes[data.contentHash] == false,
            "Media: a token has already been created with this content hash"
        );
        require(
            data.metadataHash != 0,
            "Media: metadata hash must be non-zero"
        );

        uint256 tokenId = _tokenIdTracker.current();

        _safeMint(creator, tokenId);
        _tokenIdTracker.increment();
        _setTokenContentHash(tokenId, data.contentHash);
        _setTokenMetadataHash(tokenId, data.metadataHash);
        _setTokenMetadataURI(tokenId, data.metadataURI);
        _setTokenURI(tokenId, data.tokenURI);
        _creatorTokens[creator].add(tokenId);
        _contentHashes[data.contentHash] = true;

        tokenCreators[tokenId] = creator;
        previousTokenOwners[tokenId] = creator;
        IMarket(marketContract).setBidShares(tokenId, bidShares);
    }

    function _setTokenContentHash(uint256 tokenId, bytes32 contentHash)
        internal
        virtual
        onlyExistingToken(tokenId)
    {
        tokenContentHashes[tokenId] = contentHash;
    }

    function _setTokenMetadataHash(uint256 tokenId, bytes32 metadataHash)
        internal
        virtual
        onlyExistingToken(tokenId)
    {
        tokenMetadataHashes[tokenId] = metadataHash;
    }

    function _setTokenMetadataURI(uint256 tokenId, string memory metadataURI)
        internal
        virtual
        onlyExistingToken(tokenId)
    {
        _tokenMetadataURIs[tokenId] = metadataURI;
    }

    /**
     * @notice Destroys `tokenId`.
     * @dev We modify the OZ _burn implementation to
     * maintain metadata and to remove the
     * previous token owner from the piece
     */
    function _burn(uint256 tokenId) internal override {
        string memory tokenURI = _tokenURIs[tokenId];

        super._burn(tokenId);

        if (bytes(tokenURI).length != 0) {
            _tokenURIs[tokenId] = tokenURI;
        }

        delete previousTokenOwners[tokenId];
    }

    /**
     * @notice transfer a token and remove the ask for it.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal override {
        IMarket(marketContract).removeAsk(tokenId);

        super._transfer(from, to, tokenId);
    }

    /**
     * @dev Calculates EIP712 DOMAIN_SEPARATOR based on the current contract and chain ID.
     */
    function _calculateDomainSeparator() internal view returns (bytes32) {
        uint256 chainID;
        /* solium-disable-next-line */
        assembly {
            chainID := chainid()
        }

        return
            keccak256(
                abi.encode(
                    keccak256(
                        "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
                    ),
                    keccak256(bytes("Arto")),
                    keccak256(bytes("1")),
                    chainID,
                    address(this)
                )
            );
    }
}