Super Simple NFT staking

DamnSimpleNftStake.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/IERC721.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/utils/ERC721Holder.sol ";

contract NftStaker {
    IERC721 public parentNFT;

    struct Stake {
        uint256 tokenId;
        uint256 timestamp;
    }

    // map staker address to stake details
    mapping(address => Stake) public stakes;

    // map staker to total staking time 
    mapping(address => uint256) public stakingTime;    

    constructor() {
        parentNFT = IERC721(0xdccB0e678bEA8FE3d97921CbFF85Be757a223312); // Change it to your NFT contract addr
    }

    function stake(uint256 _tokenId) public {
        stakes[msg.sender] = Stake(_tokenId, block.timestamp); 
        parentNFT.safeTransferFrom(msg.sender, address(this), _tokenId, "0x00");
    } 

    function unstake() public {
        parentNFT.safeTransferFrom(address(this), msg.sender, stakes[msg.sender].tokenId, "0x00");
        stakingTime[msg.sender] += (block.timestamp - stakes[msg.sender].timestamp);
        delete stakes[msg.sender];
    }      

     function onERC721Received(
        address,
        address,
        uint256,
        bytes memory
    ) external pure returns (bytes4) {
        return bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"));
    }

}