NFT Drops Gated by Accesslists

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract Accesslist is ERC721, Ownable {
    bytes32 public merkleRoot;
    uint256 public nextTokenId;
    mapping(address => bool) public claimed;

    constructor() ERC721("ExampleNFT", "NFT") {
        merkleRoot = 0x0;
    }

    function isWhiteListed(bytes32[] memory proof, bytes32 leaf) public view returns(bool) {
        return MerkleProof.verify(proof, merkleRoot, leaf);
    }

    function setMerkleRoot(bytes32 merkleRoot_) external onlyOwner {
        merkleRoot = merkleRoot_;
    }

    function mint(address to, bytes32[] calldata merkleProof) public payable {
        require(claimed[to] == false, "already claimed");
        claimed[to] = true;
        require(
            isWhiteListed(
                merkleProof,
                keccak256(abi.encodePacked(to))
            ),
            "invalid merkle proof"
        );
        nextTokenId++;
        _mint(to, nextTokenId);
    }
}

mapping(address => uint256) public whitelistMapping;

function presale(address _to, uint256 _count) external payable {
    // ensure _to address has tokens left to mint
    require(whitelistMapping[_to] > 0, "no whitelist tokens for user");

    // decrement mapping for user
    whitelistMapping[_to] -= _count;

    // presale minting logic here
}