// SPDX-License-Identifier: MIT
pragma solidity ^0.8.21;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract NTAKE is Ownable, ReentrancyGuard {
    using SafeMath for uint256;

    IERC20 public navisToken;
    mapping(address => uint256) public stakedBalances;
    mapping(address => uint256) public lastStakeTimestamp;

    uint256 public constant BONUS_PERIOD = 30 days;
    uint256 public constant BONUS_MULTIPLIER = 2; // Bonus multiplier for the first 30 days

    uint256 public constant UNSTAKING_PERIOD = 7 days;
    uint256 public constant PENALTY_MULTIPLIER = 2; // Penalty multiplier for unstaking within 7 days

    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 stakedAmount, uint256 receivedAmount);

    constructor(address _navisToken) {
        navisToken = IERC20(_navisToken);
    }

    function stake(uint256 amount) external nonReentrant {
        require(amount > 0, "Amount must be greater than zero");

        // Calculate bonus for early stakers
        uint256 bonusMultiplier = (block.timestamp.sub(lastStakeTimestamp[msg.sender]) <= BONUS_PERIOD) ? BONUS_MULTIPLIER : 1;
        uint256 stakingAmount = amount.mul(bonusMultiplier);

        require(navisToken.transferFrom(msg.sender, address(this), stakingAmount), "Transfer failed");

        stakedBalances[msg.sender] = stakedBalances[msg.sender].add(stakingAmount);
        lastStakeTimestamp[msg.sender] = block.timestamp;

        emit Staked(msg.sender, stakingAmount);
    }

    function withdraw(uint256 amount) external nonReentrant {
        require(amount > 0, "Amount must be greater than zero");
        require(amount <= stakedBalances[msg.sender], "Insufficient staked balance");

        uint256 stakedAmount = stakedBalances[msg.sender];
        uint256 withdrawalAmount = calculateWithdrawalAmount(stakedAmount, amount);

        // Apply penalty for early unstaking
        if (block.timestamp.sub(lastStakeTimestamp[msg.sender]) < UNSTAKING_PERIOD) {
            uint256 penalty = amount.mul(PENALTY_MULTIPLIER).div(100);
            withdrawalAmount = withdrawalAmount.sub(penalty);
        }

        stakedBalances[msg.sender] = stakedBalances[msg.sender].sub(withdrawalAmount);
        navisToken.transfer(msg.sender, withdrawalAmount);

        emit Withdrawn(msg.sender, stakedAmount, withdrawalAmount);
    }

    function calculateWithdrawalAmount(uint256 stakedAmount, uint256 requestedAmount) internal view returns (uint256) {
        // Implement your withdrawal logic, considering any fees or conditions
        // This function can be customized based on your specific requirements
        return requestedAmount;
    }
}