Staking.sol

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract Staking {
    mapping(address => uint) timestamp;
    mapping(address => uint) amount;
    IERC20 rewardToken;
    IERC20 stakedToken;

    constructor(IERC20 _rewardToken, IERC20 _stakedToken) {
        rewardToken = _rewardToken;
        stakedToken = _stakedToken;
    }

    function stake(uint _amount) external {
        timestamp[msg.sender] = block.timestamp;
        amount[msg.sender] = _amount;
        require(stakedToken.transferFrom(msg.sender, address(this), _amount), "F");
    }

    function unstake() external {
        uint duration = block.timestamp - timestamp[msg.sender];
        uint _reward = duration * amount[msg.sender] / 365 days;
        uint _amount = amount[msg.sender];
        amount[msg.sender] = timestamp[msg.sender] = 0;
        require(stakedToken.transfer(msg.sender, _reward), "F");
        require(rewardToken.transfer(msg.sender, _amount), "F");
    }
}