Smart Contracts &
Blockchain
in india

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

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

/**
 * @title AlphasoftToken — Example ERC-20 with Staking
 * @author Alphasoft Global | alphasoftglobal.com
 */
contract AlphasoftToken is ERC20, Ownable, ReentrancyGuard {

    uint256 public constant MAX_SUPPLY = 100_000_000 * 10**18;
    uint256 public stakingAPR = 12;  // 12% annual

    struct Stake {
        uint256 amount;
        uint256 startTime;
        bool    active;
    }

    mapping(address => Stake) public stakes;

    event Staked(address indexed user, uint256 amount);
    event Unstaked(address indexed user, uint256 reward);

    constructor() ERC20("AlphasoftToken", "ASG") {
        _mint(msg.sender, MAX_SUPPLY);
    }

    function stake(uint256 _amount) external nonReentrant {
        require(_amount > 0, "Amount must be > 0");
        require(!stakes[msg.sender].active, "Already staking");
        _transfer(msg.sender, address(this), _amount);
        stakes[msg.sender] = Stake(_amount, block.timestamp, true);
        emit Staked(msg.sender, _amount);
    }

    function unstake() external nonReentrant {
        Stake memory s = stakes[msg.sender];
        require(s.active, "No active stake");
        uint256 duration = block.timestamp - s.startTime;
        uint256 reward = (s.amount * stakingAPR * duration) / (365 days * 100);
        stakes[msg.sender].active = false;
        _transfer(address(this), msg.sender, s.amount + reward);
        emit Unstaked(msg.sender, reward);
    }
}