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// SPDX-License-Identifier: MIT
// The SPDX-License-Identifier specifies the license for the code.

pragma solidity ^0.8.0;
// Indicates that the code should be compiled using a Solidity compiler version equal to or higher than 0.8.0.

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
// Imports interfaces for ERC721 and ERC20 tokens, Ownable contract, and SafeMath for safe arithmetic operations.

contract NFTStaking is Ownable {
    using SafeMath for uint256;
    // The contract inherits from the Ownable contract, and SafeMath is used for safe arithmetic operations.

IERC721 public nftToken;
    IERC20 public nativeToken;
    // Declarations of interfaces for ERC721 and ERC20 tokens.

uint256 public stakingRewardRate = 1;
    uint256 public totalStakedNFTs;
    // Public variables to store staking parameters.

mapping(address => uint256) public stakedNFTs;
    mapping(address => uint256) public lastClaimTime;
    // Mapping to track the number of staked NFTs and the last claim time for each user.

event NFTStaked(address indexed user, uint256 amount);
    event TokensClaimed(address indexed user, uint256 amount);
    // Events to log NFT staking and token claiming.

constructor(address _nftToken, address _nativeToken) {
        nftToken = IERC721(_nftToken);
        nativeToken = IERC20(_nativeToken);
        // Constructor to set the addresses of the ERC721 and ERC20 tokens.

}

function stakeNFT(uint256 tokenId) external {
        require(nftToken.ownerOf(tokenId) == msg.sender, "You do not own this NFT");
        require(nftToken.getApproved(tokenId) == address(this), "Contract not approved to transfer NFT");
        // Checks if the caller owns the NFT and if the contract is approved to transfer the NFT.

nftToken.transferFrom(msg.sender, address(this), tokenId);
        stakedNFTs[msg.sender] = stakedNFTs[msg.sender].add(1);
        totalStakedNFTs = totalStakedNFTs.add(1);
        lastClaimTime[msg.sender] = block.timestamp;
        // Transfers the NFT to the contract, updates staking information, and records the last claim time.

emit NFTStaked(msg.sender, tokenId);
        // Emits an event log for the NFT staking.

}

function claimTokens() external {
        uint256 reward = calculateReward(msg.sender);
        require(reward > 0, "No tokens to claim");
        // Checks if there are tokens to claim.

lastClaimTime[msg.sender] = block.timestamp;
        nativeToken.transfer(msg.sender, reward);
        // Updates the last claim time and transfers the earned tokens to the user.

emit TokensClaimed(msg.sender, reward);
        // Emits an event log for the tokens claimed.

}

function calculateReward(address user) public view returns (uint256) {
        uint256 elapsedTime = block.timestamp.sub(lastClaimTime[user]);
        uint256 stakedAmount = stakedNFTs[user];
        return stakedAmount.mul(stakingRewardRate).mul(elapsedTime).div(1 days);
        // Calculates the reward based on staking parameters and elapsed time.

}

function setStakingRewardRate(uint256 _stakingRewardRate) external onlyOwner {
        stakingRewardRate = _stakingRewardRate;
        // Allows the contract owner to set the staking reward rate.

}
}