// Contract: Collection
// Target function: function mint(uint256 quantity) public payable
entrant call");
        _status = _ENTERED;

        _;
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

contract ERC721A is
    Context,
    ERC165,
    IERC721,
    IERC721Metadata,
    IERC721Enumerable
{
    using Address for address;
    using Strings for uint256;

    struct TokenOwnership {
        address addr;
        uint64 startTimestamp;
    }

    struct AddressData {
        uint128 balance;
        uint128 numberMinted;
    }

    uint256 private currentIndex = 0;

    uint256 internal immutable collectionSize;
    uint256 internal immutable maxBatchSize;
    string private _name;
    string private _symbol;
    // An empty struct value does not necessarily mean the token is unowned. See ownershipOf implementation for details.
    mapping(uint256 => TokenOwnership) private _ownerships;
    mapping(address => AddressData) private _addressData;
    mapping(uint256 => address) private _tokenApprovals;
    mapping(address => mapping(address => bool)) private _operatorApprovals;
    constructor(
        string memory name_,
        string memory symbol_,
        uint256 maxBatchSize_,
        uint256 collectionSize_
    ) {
        require(
            collectionSize_ > 0,
            "ERC721A: collection must have a nonzero supply"
        );
        require(maxBatchSize_ > 0, "ERC721A: max batch size must be nonzero");
        _name = name_;
        _symbol = symbol_;
        maxBatchSize = maxBatchSize_;
        collectionSize = collectionSize_;
    }
    function totalSupply() public view override returns (uint256) {
        return currentIndex;
    }
    function tokenByIndex(uint256 index)
        public
        view
        override
        returns (uint256)
    {
        require(index < totalSupply(), "ERC721A: global index out of bounds");
        return index;
    }
    function tokenOfOwnerByIndex(address owner, uint256 index)
        public
        view
        override
        returns (uint256)
    {
        require(index < balanceOf(owner), "ERC721A: owner index out of bounds");
        uint256 numMintedSoFar = totalSupply();
        uint256 tokenIdsIdx = 0;
        address currOwnershipAddr = address(0);
        for (uint256 i = 0; i < numMintedSoFar; i++) {
            TokenOwnership memory ownership = _ownerships[i];
            if (ownership.addr != address(0)) {
                currOwnershipAddr = ownership.addr;
            }
            if (currOwnershipAddr == owner) {
                if (tokenIdsIdx == index) {
                    return i;
                }
                tokenIdsIdx++;
            }
        }
        revert("ERC721A: unable to get token of owner by index");
    }
    function supportsInterface(bytes4 interfaceId)
        public
        view
        virtual
        override(ERC165, IERC165)
        returns (bool)
    {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            interfaceId == type(IERC721Enumerable).interfaceId ||
            super.supportsInterface(interfaceId);
    }
    function balanceOf(address owner) public view override returns (uint256) {
        require(
            owner != address(0),
            "ERC721A: balance query for the zero address"
        );
        return uint256(_addressData[owner].balance);
    }

    function _numberMinted(address owner) internal view returns (uint256) {
        require(
            owner != address(0),
            "ERC721A: number minted query for the zero address"
        );
        return uint256(_addressData[owner].numberMinted);
    }

    function ownershipOf(uint256 tokenId)
        internal
        view
        returns (TokenOwnership memory)
    {
        require(_exists(tokenId), "ERC721A: owner query for nonexistent token");

        uint256 lowestTokenToCheck;
        if (tokenId >= maxBatchSize) {
            lowestTokenToCheck = tokenId - maxBatchSize + 1;
        }

        for (uint256 curr = tokenId; curr >= lowestTokenToCheck; curr--) {
            TokenOwnership memory ownership = _ownerships[curr];
            if (ownership.addr != address(0)) {
                return ownership;
            }
        }

        revert("ERC721A: unable to determine the owner of token");
    }
    function ownerOf(uint256 tokenId) public view override returns (address) {
        return ownershipOf(tokenId).addr;
    }
    function name() public view virtual override returns (string memory) {
        return _name;
    }
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }
    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        require(
            _exists(tokenId),
            "ERC721Metadata: URI query for nonexistent token"
        );

        string memory baseURI = _baseURI();
        return
            bytes(baseURI).length > 0
                ? string(abi.encodePacked(baseURI, tokenId.toString()))
                : "";
    }
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }
    function approve(address to, uint256 tokenId) public override {
        address owner = ERC721A.ownerOf(tokenId);
        require(to != owner, "ERC721A: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721A: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId, owner);
    }
    function getApproved(uint256 tokenId)
        public
        view
        override
        returns (address)
    {
        require(
            _exists(tokenId),
            "ERC721A: approved query for nonexistent token"
        );

        return _tokenApprovals[tokenId];
    }
    function setApprovalForAll(address operator, bool approved)
        public
        override
    {
        require(operator != _msgSender(), "ERC721A: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
    }
    function isApprovedForAll(address owner, address operator)
        public
        view
        virtual
        override
        returns (bool)
    {
        return _operatorApprovals[owner][operator];
    }
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public override {
        _transfer(from, to, tokenId);
    }
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public override {
        safeTransferFrom(from, to, tokenId, "");
    }
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) public override {
        _transfer(from, to, tokenId);
        require(
            _checkOnERC721Received(from, to, tokenId, _data),
            "ERC721A: transfer to non ERC721Receiver implementer"
        );
    }
    function _exists(uint256 tokenId) internal view returns (bool) {
        return tokenId < currentIndex;
    }

    function _safeMint(address to, uint256 quantity) internal {
        _safeMint(to, quantity, "");
    }
    function _safeMint(
        address to,
        uint256 quantity,
        bytes memory _data
    ) internal {
        uint256 startTokenId = currentIndex;
        require(to != address(0), "ERC721A: mint to the zero address");
        require(!_exists(startTokenId), "ERC721A: token already minted");
        require(quantity <= maxBatchSize, "ERC721A: quantity to mint too high");

        _beforeTokenTransfers(address(0), to, startTokenId, quantity);

        AddressData memory addressData = _addressData[to];
        _addressData[to] = AddressData(
            addressData.balance + uint128(quantity),
            addressData.numberMinted + uint128(quantity)
        );
        _ownerships[startTokenId] = TokenOwnership(to, uint64(block.timestamp));

        uint256 updatedIndex = startTokenId;

        for (uint256 i = 0; i < quantity; i++) {
            emit Transfer(address(0), to, updatedIndex);
            require(
                _checkOnERC721Received(address(0), to, updatedIndex, _data),
                "ERC721A: transfer to non ERC721Receiver implementer"
            );
            updatedIndex++;
        }

        currentIndex = updatedIndex;
        _afterTokenTransfers(address(0), to, startTokenId, quantity);
    }
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) private {
        TokenOwnership memory prevOwnership = ownershipOf(tokenId);

        bool isApprovedOrOwner = (_msgSender() == prevOwnership.addr ||
            getApproved(tokenId) == _msgSender() ||
            isApprovedForAll(prevOwnership.addr, _msgSender()));

        require(
            isApprovedOrOwner,
            "ERC721A: transfer caller is not owner nor approved"
        );

        require(
            prevOwnership.addr == from,
            "ERC721A: transfer from incorrect owner"
        );
        require(to != address(0), "ERC721A: transfer to the zero address");

        _beforeTokenTransfers(from, to, tokenId, 1);
        _approve(address(0), tokenId, prevOwnership.addr);

        _addressData[from].balance -= 1;
        _addressData[to].balance += 1;
        _ownerships[tokenId] = TokenOwnership(to, uint64(block.timestamp));
        // Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
        uint256 nextTokenId = tokenId + 1;
        if (_ownerships[nextTokenId].addr == address(0)) {
            if (_exists(nextTokenId)) {
                _ownerships[nextTokenId] = TokenOwnership(
                    prevOwnership.addr,
                    prevOwnership.startTimestamp
                );
            }
        }

        emit Transfer(from, to, tokenId);
        _afterTokenTransfers(from, to, tokenId, 1);
    }
    function _approve(
        address to,
        uint256 tokenId,
        address owner
    ) private {
        _tokenApprovals[tokenId] = to;
        emit Approval(owner, to, tokenId);
    }

    uint256 public nextOwnerToExplicitlySet = 0;
    function _setOwnersExplicit(uint256 quantity) internal {
        uint256 oldNextOwnerToSet = nextOwnerToExplicitlySet;
        require(quantity > 0, "quantity must be nonzero");
        uint256 endIndex = oldNextOwnerToSet + quantity - 1;
        if (endIndex > collectionSize - 1) {
            endIndex = collectionSize - 1;
        }
        require(_exists(endIndex), "not enough minted yet for this cleanup");
        for (uint256 i = oldNextOwnerToSet; i <= endIndex; i++) {
            if (_ownerships[i].addr == address(0)) {
                TokenOwnership memory ownership = ownershipOf(i);
                _ownerships[i] = TokenOwnership(
                    ownership.addr,
                    ownership.startTimestamp
                );
            }
        }
        nextOwnerToExplicitlySet = endIndex + 1;
    }
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (to.isContract()) {
            try
                IERC721Receiver(to).onERC721Received(
                    _msgSender(),
                    from,
                    tokenId,
                    _data
                )
            returns (bytes4 retval) {
                return retval == IERC721Receiver(to).onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert(
                        "ERC721A: transfer to non ERC721Receiver implementer"
                    );
                } else {
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }
    function _beforeTokenTransfers(
        address from,
        address to,
        uint256 startTokenId,
        uint256 quantity
    ) internal virtual {}
    function _afterTokenTransfers(
        address from,
        address to,
        uint256 startTokenId,
        uint256 quantity
    ) internal virtual {}
}

library MerkleProof {
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }
    function processProof(bytes32[] memory proof, bytes32 leaf)
        internal
        pure
        returns (bytes32)
    {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                computedHash = _efficientHash(computedHash, proofElement);
            } else {
                computedHash = _efficientHash(proofElement, computedHash);
            }
        }
        return computedHash;
    }

    function _efficientHash(bytes32 a, bytes32 b)
        private
        pure
        returns (bytes32 value)
    {
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}

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);
}

// Collection contract is licensed under the GPLv3 license.

contract Collection is Ownable, ERC721A {

    using Strings for uint256;

    struct Tier {
        uint256 maxTokens;
        uint256 price;
    }

    uint256 constant private _weiUnit = 1000000000000000000;

    Tier[] private _tiers;

    mapping(uint256 => string) private _tokenURIs;
    bool public isPublicSaleOpen = false;

    string public baseURI = "";
    string public _extension = ".json";
    string public constant collectionName = "GreenInvest: Massms Collection";
    string public constant collectionSymbol = "GRI";
    
    uint256 internal _USDThreshold = 2;

    address public ETHUSDAddress = 0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419; // ETH/USD price feeder contract address
    
    AggregatorV3Interface internal priceFeed;

    mapping(address => bool) public preSaleList;

    constructor() ERC721A(collectionName, collectionSymbol, 1000, 10000) {
        _tiers.push(Tier(5000, 220));
        _tiers.push(Tier(8000, 440));
        _tiers.push(Tier(10000, 880));

        priceFeed = AggregatorV3Interface(ETHUSDAddress);
    }