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StakingToken.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "./IERC20.sol";

contract StakingToken is ReentrancyGuard {
    mapping(address => uint256) internal stakeholders;
    uint256 private _totalSupply;
    // IERC20 public stakingToken;

    // constructor( address _stakingToken) {
    //      stakingToken = IERC20(_stakingToken);
    // }

    /*========VIEWS==========*/
    function totalSupply() external view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) external view returns (uint256) {
        return stakeholders[account];
    }

    /*========FUNCTIONS==========*/
    function stake(uint256 amount,IERC20 stakingToken ) external nonReentrant {
        require(amount > 0, "Cannot stake 0");
        require(stakingToken.balanceOf(msg.sender) > 0, "Empty balance");
        _totalSupply += amount;
        stakeholders[msg.sender] += amount;
        // stakingToken.approve(address(this),amount);
        stakingToken.transferFrom(msg.sender,address(this), amount);
        emit Staked(msg.sender, amount);
    }

    function unstake(uint256 amount,IERC20 stakingToken) public nonReentrant {
        require(amount > 0, "Cannot withdraw 0");
        _totalSupply -= amount;
        stakeholders[msg.sender] -= amount;
        stakingToken.transfer(msg.sender, amount);
        emit Unstake(msg.sender, amount);
    }

    /*========EVENTS==========*/
    event Staked(address indexed user, uint256 amount);
    event Unstake(address indexed user, uint256 amount);
}