// File: BoredApePixelClub.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.3;

import "./BoredApeYachtClub.sol";


contract BoredApePixelClub is ERC721, Ownable {
    using SafeMath for uint;

    BoredApeYachtClub private _boredApeYachtClub;

    uint private constant _PRICE = 30000000000000000;

    string private _provenanceHash = '';

    uint256 private _maxSupply;

    bool private _activeSale = false;

    event WithdrawCompleted(address indexed recipient, uint amount);

    event ReserveCompleted(address indexed recipient, uint tokenId);

    event BaseURIUpdated(string newBaseURI);

    event ProvenanceHashUpdated(string newProvenanceHash);

    event BAYCAddressUpdated(address newBoredApeYachtClubAddress);

    event PurchaseCompleted(address indexed recipient, uint numberOfTokens, uint payment);

    constructor(string memory name, string memory symbol, uint maxSupply, address boredApeYachtClubAddress) ERC721(name, symbol) {
        _boredApeYachtClub = BoredApeYachtClub(boredApeYachtClubAddress);
        _maxSupply = maxSupply;
    }

    function flipSaleState() public onlyOwner {
        _activeSale = !_activeSale;
    }

    function withdraw() public onlyOwner {
        uint balance = address(this).balance;
        msg.sender.transfer(balance);

        emit WithdrawCompleted(msg.sender, balance);
    }

    function reserve(uint tokenId) public onlyOwner {
        require(!_exists(tokenId), "Token has already been minted");

        _safeMint(msg.sender, tokenId);

        emit ReserveCompleted(msg.sender, tokenId);
    }

    function numberBoredApesBought() public view returns (uint) {
        return _boredApeYachtClub.balanceOf(msg.sender);
    }

    function getNumberAvailableApes() public view returns (uint) {
        uint numberAvailable = 0;
        uint numberBAYC = numberBoredApesBought();

        for (uint i= 0; i < numberBAYC; i++) {
            uint tokenIndex = _boredApeYachtClub.tokenOfOwnerByIndex(msg.sender, i);
            if (!_exists(tokenIndex)) {
                numberAvailable++;
            }
        }

        return numberAvailable;
    }

    function random(uint range, uint nonce) public view returns (uint) {
        uint randomNumber = uint(keccak256(abi.encodePacked(block.timestamp, msg.sender, nonce))) % range;
        return randomNumber;
    }

    function purchase(uint numberOfTokens) public payable {
        require(_PRICE.mul(numberOfTokens) <= msg.value, "Ether value sent is not correct");
        require(_activeSale, "Sale must be active to mint");
        require(totalSupply().add(numberOfTokens) <= _maxSupply, "Minting would exceed max supply");

        uint numberBAYC = numberBoredApesBought();
        uint numberMinted = 0;

        uint startIndex = random(numberBAYC, numberBAYC);

        for (uint i = startIndex; i < numberBAYC + startIndex; i++) {

            uint tokenIndex = _boredApeYachtClub.tokenOfOwnerByIndex(msg.sender, i % numberBAYC);

            if (!_exists(tokenIndex)) {
                _safeMint(msg.sender, tokenIndex);

                numberMinted++;

                if (numberMinted == numberOfTokens) {
                    emit PurchaseCompleted(msg.sender, numberOfTokens, msg.value);
                    return;
                }
            }
        }

        // We can only reach this line if numberOfTokens is greater than the number of available tokens
        require(false, "Number of requested tokens exceeds available tokens");
    }

    function provenanceHash() public view virtual returns (string memory) {
        return _provenanceHash;
    }

    function price() public view virtual returns (uint) {
        return _PRICE;
    }

    function maxSupply() public view virtual returns (uint) {
        return _maxSupply;
    }

    function activeSale() public view virtual returns (bool) {
        return _activeSale;
    }

    function setBaseURI(string memory baseURI) public onlyOwner {
        _setBaseURI(baseURI);

        emit BaseURIUpdated(baseURI);
    }

    function setProvenanceHash(string memory newProvenanceHash) public onlyOwner {
        _provenanceHash = newProvenanceHash;

        emit ProvenanceHashUpdated(newProvenanceHash);
    }

    function setBoredApeYachtClubAddress(address boredApeYachtClubAddress) public onlyOwner {
        _boredApeYachtClub = BoredApeYachtClub(boredApeYachtClubAddress);

        emit BAYCAddressUpdated(boredApeYachtClubAddress);
    }
}

// File: BoredApeYachtClub.sol



/**
 *Submitted for verification at Etherscan.io on 2021-04-22
*/

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

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
return msg.sender;
}

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

// File: @openzeppelin/contracts/introspection/IERC165.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
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);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



pragma solidity >=0.6.2 <0.8.0;


/**
 * @dev Required interface of an ERC721 compliant contract.
 */
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;
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Metadata.sol



pragma solidity >=0.6.2 <0.8.0;


/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
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);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Enumerable.sol



pragma solidity >=0.6.2 <0.8.0;


/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
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);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
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);
}

// File: @openzeppelin/contracts/introspection/ERC165.sol



pragma solidity >=0.6.0 <0.8.0;


/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
abstract 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 virtual 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;
}
}

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



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
/**
 * @dev Returns the addition of two unsigned integers, with an overflow flag.
 *
 * _Available since v3.4._
 */
function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
uint256 c = a + b;
if (c < a) return (false, 0);
return (true, c);
}

/**
 * @dev Returns the substraction of two unsigned integers, with an overflow flag.
 *
 * _Available since v3.4._
 */
function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
if (b > a) return (false, 0);
return (true, a - b);
}

/**
 * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
 *
 * _Available since v3.4._
 */
function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
// benefit is lost if 'b' is also tested.
// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
if (a == 0) return (true, 0);
uint256 c = a * b;
if (c / a != b) return (false, 0);
return (true, c);
}

/**
 * @dev Returns the division of two unsigned integers, with a division by zero flag.
 *
 * _Available since v3.4._
 */
function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
if (b == 0) return (false, 0);
return (true, a / b);
}

/**
 * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
 *
 * _Available since v3.4._
 */
function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
if (b == 0) return (false, 0);
return (true, a % b);
}

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

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

/**
 * @dev Returns the multiplication of two unsigned integers, reverting on
 * overflow.
 *
 * Counterpart to Solidity's `*` operator.
 *
 * Requirements:
 *
 * - Multiplication cannot overflow.
 */
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) return 0;
uint256 c = a * b;
require(c / a == b, "SafeMath: multiplication overflow");
return c;
}

/**
 * @dev Returns the integer division of two unsigned integers, reverting on
 * division by zero. The result is rounded towards zero.
 *
 * Counterpart to Solidity's `/` operator. Note: this function uses a
 * `revert` opcode (which leaves remaining gas untouched) while Solidity
 * uses an invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function div(uint256 a, uint256 b) internal pure returns (uint256) {
require(b > 0, "SafeMath: division by zero");
return a / b;
}

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

/**
 * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
 * overflow (when the result is negative).
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {trySub}.
 *
 * Counterpart to Solidity's `-` operator.
 *
 * Requirements:
 *
 * - Subtraction cannot overflow.
 */
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b <= a, errorMessage);
return a - b;
}

/**
 * @dev Returns the integer division of two unsigned integers, reverting with custom message on
 * division by zero. The result is rounded towards zero.
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {tryDiv}.
 *
 * Counterpart to Solidity's `/` operator. Note: this function uses a
 * `revert` opcode (which leaves remaining gas untouched) while Solidity
 * uses an invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b > 0, errorMessage);
return a / b;
}

/**
 * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
 * reverting with custom message when dividing by zero.
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {tryMod}.
 *
 * Counterpart to Solidity's `%` operator. This function uses a `revert`
 * opcode (which leaves remaining gas untouched) while Solidity uses an
 * invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b > 0, errorMessage);
return a % b;
}
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
/**
 * @dev Returns true if `account` is a contract.
 *
 * [IMPORTANT]
 * ====
 * It is unsafe to assume that an address for which this function returns
 * false is an externally-owned account (EOA) and not a contract.
 *
 * Among others, `isContract` will return false for the following
 * types of addresses:
 *
 *  - an externally-owned account
 *  - a contract in construction
 *  - an address where a contract will be created
 *  - an address where a contract lived, but was destroyed
 * ====
 */
function isContract(address account) internal view returns (bool) {
// This method relies on extcodesize, which returns 0 for contracts in
// construction, since the code is only stored at the end of the
// constructor execution.

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

/**
 * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
 * `recipient`, forwarding all available gas and reverting on errors.
 *
 * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
 * of certain opcodes, possibly making contracts go over the 2300 gas limit
 * imposed by `transfer`, making them unable to receive funds via
 * `transfer`. {sendValue} removes this limitation.
 *
 * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
 *
 * IMPORTANT: because control is transferred to `recipient`, care must be
 * taken to not create reentrancy vulnerabilities. Consider using
 * {ReentrancyGuard} or the
 * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
 */
function sendValue(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");

// solhint-disable-next-line avoid-low-level-calls, avoid-call-value
(bool success, ) = recipient.call{ value: amount }("");
require(success, "Address: unable to send value, recipient may have reverted");
}

/**
 * @dev Performs a Solidity function call using a low level `call`. A
 * plain`call` is an unsafe replacement for a function call: use this
 * function instead.
 *
 * If `target` reverts with a revert reason, it is bubbled up by this
 * function (like regular Solidity function calls).
 *
 * Returns the raw returned data. To convert to the expected return value,
 * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
 *
 * Requirements:
 *
 * - `target` must be a contract.
 * - calling `target` with `data` must not revert.
 *
 * _Available since v3.1._
 */
function functionCall(address target, bytes memory data) internal returns (bytes memory) {
return functionCall(target, data, "Address: low-level call failed");
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
 * `errorMessage` as a fallback revert reason when `target` reverts.
 *
 * _Available since v3.1._
 */
function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
return functionCallWithValue(target, data, 0, errorMessage);
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but also transferring `value` wei to `target`.
 *
 * Requirements:
 *
 * - the calling contract must have an ETH balance of at least `value`.
 * - the called Solidity function must be `payable`.
 *
 * _Available since v3.1._
 */
function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
}

/**
 * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
 * with `errorMessage` as a fallback revert reason when `target` reverts.
 *
 * _Available since v3.1._
 */
function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
require(address(this).balance >= value, "Address: insufficient balance for call");
require(isContract(target), "Address: call to non-contract");

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

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but performing a static call.
 *
 * _Available since v3.3._
 */
function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
return functionStaticCall(target, data, "Address: low-level static call failed");
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
 * but performing a static call.
 *
 * _Available since v3.3._
 */
function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
require(isContract(target), "Address: static call to non-contract");

// solhint-disable-next-line avoid-low-level-calls
(bool success, bytes memory returndata) = target.staticcall(data);
return _verifyCallResult(success, returndata, errorMessage);
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but performing a delegate call.
 *
 * _Available since v3.4._
 */
function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
return functionDelegateCall(target, data, "Address: low-level delegate call failed");
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
 * but performing a delegate call.
 *
 * _Available since v3.4._
 */
function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
require(isContract(target), "Address: delegate call to non-contract");

// solhint-disable-next-line avoid-low-level-calls
(bool success, bytes memory returndata) = target.delegatecall(data);
return _verifyCallResult(success, returndata, errorMessage);
}

function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
if (success) {
return returndata;
} else {
// Look for revert reason and bubble it up if present
if (returndata.length > 0) {
// The easiest way to bubble the revert reason is using memory via assembly

// solhint-disable-next-line no-inline-assembly
assembly {
let returndata_size := mload(returndata)
revert(add(32, returndata), returndata_size)
}
} else {
revert(errorMessage);
}
}
}
}

// File: @openzeppelin/contracts/utils/EnumerableSet.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
// To implement this library for multiple types with as little code
// repetition as possible, we write it in terms of a generic Set type with
// bytes32 values.
// The Set implementation uses private functions, and user-facing
// implementations (such as AddressSet) are just wrappers around the
// underlying Set.
// This means that we can only create new EnumerableSets for types that fit
// in bytes32.

struct Set {
// Storage of set values
bytes32[] _values;

// Position of the value in the `values` array, plus 1 because index 0
// means a value is not in the set.
mapping (bytes32 => uint256) _indexes;
}

/**
 * @dev Add a value to a set. O(1).
 *
 * Returns true if the value was added to the set, that is if it was not
 * already present.
 */
function _add(Set storage set, bytes32 value) private returns (bool) {
if (!_contains(set, value)) {
set._values.push(value);
// The value is stored at length-1, but we add 1 to all indexes
// and use 0 as a sentinel value
set._indexes[value] = set._values.length;
return true;
} else {
return false;
}
}

/**
 * @dev Removes a value from a set. O(1).
 *
 * Returns true if the value was removed from the set, that is if it was
 * present.
 */
function _remove(Set storage set, bytes32 value) private returns (bool) {
// We read and store the value's index to prevent multiple reads from the same storage slot
uint256 valueIndex = set._indexes[value];

if (valueIndex != 0) { // Equivalent to contains(set, value)
// To delete an element from the _values array in O(1), we swap the element to delete with the last one in
// the array, and then remove the last element (sometimes called as 'swap and pop').
// This modifies the order of the array, as noted in {at}.

uint256 toDeleteIndex = valueIndex - 1;
uint256 lastIndex = set._values.length - 1;

// When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
// so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

bytes32 lastvalue = set._values[lastIndex];

// Move the last value to the index where the value to delete is
set._values[toDeleteIndex] = lastvalue;
// Update the index for the moved value
set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

// Delete the slot where the moved value was stored
set._values.pop();

// Delete the index for the deleted slot
delete set._indexes[value];

return true;
} else {
return false;
}
}

/**
 * @dev Returns true if the value is in the set. O(1).
 */
function _contains(Set storage set, bytes32 value) private view returns (bool) {
return set._indexes[value] != 0;
}

/**
 * @dev Returns the number of values on the set. O(1).
 */
function _length(Set storage set) private view returns (uint256) {
return set._values.length;
}

/**
 * @dev Returns the value stored at position `index` in the set. O(1).
 *
 * Note that there are no guarantees on the ordering of values inside the
 * array, and it may change when more values are added or removed.
 *
 * Requirements:
 *
 * - `index` must be strictly less than {length}.
 */
function _at(Set storage set, uint256 index) private view returns (bytes32) {
require(set._values.length > index, "EnumerableSet: index out of bounds");
return set._values[index];
}

// Bytes32Set

struct Bytes32Set {
Set _inner;
}

/**
 * @dev Add a value to a set. O(1).
 *
 * Returns true if the value was added to the set, that is if it was not
 * already present.
 */
function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
return _add(set._inner, value);
}

/**
 * @dev Removes a value from a set. O(1).
 *
 * Returns true if the value was removed from the set, that is if it was
 * present.
 */
function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
return _remove(set._inner, value);
}

/**
 * @dev Returns true if the value is in the set. O(1).
 */
function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
return _contains(set._inner, value);
}

/**
 * @dev Returns the number of values in the set. O(1).
 */
function length(Bytes32Set storage set) internal view returns (uint256) {
return _length(set._inner);
}

/**
 * @dev Returns the value stored at position `index` in the set. O(1).
 *
 * Note that there are no guarantees on the ordering of values inside the
 * array, and it may change when more values are added or removed.
 *
 * Requirements:
 *
 * - `index` must be strictly less than {length}.
 */
function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
return _at(set._inner, index);
}

// AddressSet

struct AddressSet {
Set _inner;
}

/**
 * @dev Add a value to a set. O(1).
 *
 * Returns true if the value was added to the set, that is if it was not
 * already present.
 */
function add(AddressSet storage set, address value) internal returns (bool) {
return _add(set._inner, bytes32(uint256(uint160(value))));
}

/**
 * @dev Removes a value from a set. O(1).
 *
 * Returns true if the value was removed from the set, that is if it was
 * present.
 */
function remove(AddressSet storage set, address value) internal returns (bool) {
return _remove(set._inner, bytes32(uint256(uint160(value))));
}

/**
 * @dev Returns true if the value is in the set. O(1).
 */
function contains(AddressSet storage set, address value) internal view returns (bool) {
return _contains(set._inner, bytes32(uint256(uint160(value))));
}

/**
 * @dev Returns the number of values in the set. O(1).
 */
function length(AddressSet storage set) internal view returns (uint256) {
return _length(set._inner);
}

/**
 * @dev Returns the value stored at position `index` in the set. O(1).
 *
 * Note that there are no guarantees on the ordering of values inside the
 * array, and it may change when more values are added or removed.
 *
 * Requirements:
 *
 * - `index` must be strictly less than {length}.
 */
function at(AddressSet storage set, uint256 index) internal view returns (address) {
return address(uint160(uint256(_at(set._inner, index))));
}


// UintSet

struct UintSet {
Set _inner;
}

/**
 * @dev Add a value to a set. O(1).
 *
 * Returns true if the value was added to the set, that is if it was not
 * already present.
 */
function add(UintSet storage set, uint256 value) internal returns (bool) {
return _add(set._inner, bytes32(value));
}

/**
 * @dev Removes a value from a set. O(1).
 *
 * Returns true if the value was removed from the set, that is if it was
 * present.
 */
function remove(UintSet storage set, uint256 value) internal returns (bool) {
return _remove(set._inner, bytes32(value));
}

/**
 * @dev Returns true if the value is in the set. O(1).
 */
function contains(UintSet storage set, uint256 value) internal view returns (bool) {
return _contains(set._inner, bytes32(value));
}

/**
 * @dev Returns the number of values on the set. O(1).
 */
function length(UintSet storage set) internal view returns (uint256) {
return _length(set._inner);
}

/**
 * @dev Returns the value stored at position `index` in the set. O(1).
 *
 * Note that there are no guarantees on the ordering of values inside the
 * array, and it may change when more values are added or removed.
 *
 * Requirements:
 *
 * - `index` must be strictly less than {length}.
 */
function at(UintSet storage set, uint256 index) internal view returns (uint256) {
return uint256(_at(set._inner, index));
}
}

// File: @openzeppelin/contracts/utils/EnumerableMap.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing an enumerable variant of Solidity's
 * https://solidity.readthedocs.io/en/latest/types.html#mapping-types[`mapping`]
 * type.
 *
 * Maps have the following properties:
 *
 * - Entries are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Entries are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableMap for EnumerableMap.UintToAddressMap;
 *
 *     // Declare a set state variable
 *     EnumerableMap.UintToAddressMap private myMap;
 * }
 * ```
 *
 * As of v3.0.0, only maps of type `uint256 -> address` (`UintToAddressMap`) are
 * supported.
 */
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 Tries to returns the value associated with `key`.  O(1).
 * Does not revert if `key` is not in the map.
 */
function _tryGet(Map storage map, bytes32 key) private view returns (bool, bytes32) {
uint256 keyIndex = map._indexes[key];
if (keyIndex == 0) return (false, 0); // Equivalent to contains(map, key)
return (true, map._entries[keyIndex - 1]._value); // All indexes are 1-based
}

/**
 * @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) {
uint256 keyIndex = map._indexes[key];
require(keyIndex != 0, "EnumerableMap: nonexistent key"); // Equivalent to contains(map, key)
return map._entries[keyIndex - 1]._value; // All indexes are 1-based
}

/**
 * @dev Same as {_get}, with a custom error message when `key` is not in the map.
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {_tryGet}.
 */
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(uint160(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(uint160(uint256(value))));
}

/**
 * @dev Tries to returns the value associated with `key`.  O(1).
 * Does not revert if `key` is not in the map.
 *
 * _Available since v3.4._
 */
function tryGet(UintToAddressMap storage map, uint256 key) internal view returns (bool, address) {
(bool success, bytes32 value) = _tryGet(map._inner, bytes32(key));
return (success, address(uint160(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(uint160(uint256(_get(map._inner, bytes32(key)))));
}

/**
 * @dev Same as {get}, with a custom error message when `key` is not in the map.
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {tryGet}.
 */
function get(UintToAddressMap storage map, uint256 key, string memory errorMessage) internal view returns (address) {
return address(uint160(uint256(_get(map._inner, bytes32(key), errorMessage))));
}
}

// File: @openzeppelin/contracts/utils/Strings.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev String operations.
 */
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--] = bytes1(uint8(48 + temp % 10));
temp /= 10;
}
return string(buffer);
}
}

// File: @openzeppelin/contracts/token/ERC721/ERC721.sol



pragma solidity >=0.6.0 <0.8.0;












/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
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) private _tokenURIs;

// Base URI
string private _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('name()')) == 0x06fdde03
 *     bytes4(keccak256('symbol()')) == 0x95d89b41
 *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
 *
 *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
 */
bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;

/*
 *     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_METADATA);
_registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
}

/**
 * @dev See {IERC721-balanceOf}.
 */
function balanceOf(address owner) public view virtual 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 virtual override returns (address) {
return _tokenOwners.get(tokenId, "ERC721: owner query for nonexistent token");
}

/**
 * @dev See {IERC721Metadata-name}.
 */
function name() public view virtual override returns (string memory) {
return _name;
}

/**
 * @dev See {IERC721Metadata-symbol}.
 */
function symbol() public view virtual 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];
string memory base = baseURI();

// If there is no base URI, return the token URI.
if (bytes(base).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(base, _tokenURI));
}
// If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.
return string(abi.encodePacked(base, 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 virtual returns (string memory) {
return _baseURI;
}

/**
 * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
 */
function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
return _holderTokens[owner].at(index);
}

/**
 * @dev See {IERC721Enumerable-totalSupply}.
 */
function totalSupply() public view virtual 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 virtual 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 = ERC721.ownerOf(tokenId);
require(to != owner, "ERC721: approval to current owner");

require(_msgSender() == owner || ERC721.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 virtual 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 virtual 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 virtual 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 virtual returns (bool) {
require(_exists(tokenId), "ERC721: operator query for nonexistent token");
address owner = ERC721.ownerOf(tokenId);
return (spender == owner || getApproved(tokenId) == spender || ERC721.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 = ERC721.ownerOf(tokenId); // internal owner

_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(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own"); // internal owner
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);
}

/**
 * @dev Approve `to` to operate on `tokenId`
 *
 * Emits an {Approval} event.
 */
function _approve(address to, uint256 tokenId) internal virtual {
_tokenApprovals[tokenId] = to;
emit Approval(ERC721.ownerOf(tokenId), to, tokenId); // internal owner
}

/**
 * @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 { }
}

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



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
address private _owner;

event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

/**
 * @dev Initializes the contract setting the deployer as the initial owner.
 */
constructor () internal {
address msgSender = _msgSender();
_owner = msgSender;
emit OwnershipTransferred(address(0), msgSender);
}

/**
 * @dev Returns the address of the current owner.
 */
function owner() public view virtual returns (address) {
return _owner;
}

/**
 * @dev Throws if called by any account other than the owner.
 */
modifier onlyOwner() {
require(owner() == _msgSender(), "Ownable: caller is not the owner");
_;
}

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

/**
 * @dev Transfers ownership of the contract to a new account (`newOwner`).
 * Can only be called by the current owner.
 */
function transferOwnership(address newOwner) public virtual onlyOwner {
require(newOwner != address(0), "Ownable: new owner is the zero address");
emit OwnershipTransferred(_owner, newOwner);
_owner = newOwner;
}
}

// File: contracts/BoredApeYachtClub.sol


pragma solidity ^0.7.0;



/**
 * @title BoredApeYachtClub contract
 * @dev Extends ERC721 Non-Fungible Token Standard basic implementation
 */
contract BoredApeYachtClub is ERC721, Ownable {
using SafeMath for uint256;

string public BAYC_PROVENANCE = "";

uint256 public startingIndexBlock;

uint256 public startingIndex;

uint256 public constant apePrice = 80000000000000000; //0.08 ETH

uint public constant maxApePurchase = 20;

uint256 public MAX_APES;

bool public saleIsActive = false;

uint256 public REVEAL_TIMESTAMP;

constructor(string memory name, string memory symbol, uint256 maxNftSupply, uint256 saleStart) ERC721(name, symbol) {
MAX_APES = maxNftSupply;
REVEAL_TIMESTAMP = saleStart + (86400 * 9);
}

function withdraw() public onlyOwner {
uint balance = address(this).balance;
msg.sender.transfer(balance);
}

/**
 * Set some Bored Apes aside
 */
function reserveApes() public onlyOwner {
uint supply = totalSupply();
uint i;
for (i = 0; i < 30; i++) {
_safeMint(msg.sender, supply + i);
}
}

/**
 * DM Gargamel in Discord that you're standing right behind him.
 */
function setRevealTimestamp(uint256 revealTimeStamp) public onlyOwner {
REVEAL_TIMESTAMP = revealTimeStamp;
}

/*
* Set provenance once it's calculated
*/
function setProvenanceHash(string memory provenanceHash) public onlyOwner {
BAYC_PROVENANCE = provenanceHash;
}

function setBaseURI(string memory baseURI) public onlyOwner {
_setBaseURI(baseURI);
}

/*
* Pause sale if active, make active if paused
*/
function flipSaleState() public onlyOwner {
saleIsActive = !saleIsActive;
}

/**
* Mints Bored Apes
*/
function mintApe(uint numberOfTokens) public payable {
require(saleIsActive, "Sale must be active to mint Ape");
require(numberOfTokens <= maxApePurchase, "Can only mint 20 tokens at a time");
require(totalSupply().add(numberOfTokens) <= MAX_APES, "Purchase would exceed max supply of Apes");
require(apePrice.mul(numberOfTokens) <= msg.value, "Ether value sent is not correct");

for(uint i = 0; i < numberOfTokens; i++) {
uint mintIndex = totalSupply();
if (totalSupply() < MAX_APES) {
_safeMint(msg.sender, mintIndex);
}
}

// If we haven't set the starting index and this is either 1) the last saleable token or 2) the first token to be sold after
// the end of pre-sale, set the starting index block
if (startingIndexBlock == 0 && (totalSupply() == MAX_APES || block.timestamp >= REVEAL_TIMESTAMP)) {
startingIndexBlock = block.number;
}
}

/**
 * Set the starting index for the collection
 */
function setStartingIndex() public {
require(startingIndex == 0, "Starting index is already set");
require(startingIndexBlock != 0, "Starting index block must be set");

startingIndex = uint(blockhash(startingIndexBlock)) % MAX_APES;
// Just a sanity case in the worst case if this function is called late (EVM only stores last 256 block hashes)
if (block.number.sub(startingIndexBlock) > 255) {
startingIndex = uint(blockhash(block.number - 1)) % MAX_APES;
}
// Prevent default sequence
if (startingIndex == 0) {
startingIndex = startingIndex.add(1);
}
}

/**
 * Set the starting index block for the collection, essentially unblocking
 * setting starting index
 */
function emergencySetStartingIndexBlock() public onlyOwner {
require(startingIndex == 0, "Starting index is already set");

startingIndexBlock = block.number;
}
}