// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

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

contract TokenVesting is ReentrancyGuard {
    IERC20 public token;
    struct VestingSchedule {
        address beneficiary;
        uint256 totalAmount;
        uint256 released;
        uint256 start;
        uint256 duration;
        uint256 cliff;
    }

    mapping(bytes32 => VestingSchedule) public schedules;

    constructor(address _token) {
        token = IERC20(_token);
    }

    function createSchedule(
        address beneficiary,
        uint256 amount,
        uint256 start,
        uint256 duration,
        uint256 cliff
    ) external returns (bytes32 vestingId) {
        vestingId = keccak256(abi.encodePacked(beneficiary, start, duration, amount));
        schedules[vestingId] = VestingSchedule(beneficiary, amount, 0, start, duration, cliff);
        token.transferFrom(msg.sender, address(this), amount);
    }

    function vestedAmount(bytes32 vestingId) public view returns (uint256) {
        VestingSchedule storage s = schedules[vestingId];
        if (block.timestamp < s.start + s.cliff) return 0;
        if (block.timestamp >= s.start + s.duration) return s.totalAmount;
        return (s.totalAmount * (block.timestamp - s.start)) / s.duration;
    }

    function release(bytes32 vestingId) external nonReentrant {
        VestingSchedule storage s = schedules[vestingId];
        uint256 releasable = vestedAmount(vestingId) - s.released;
        require(releasable > 0, "Nothing to release");
        s.released += releasable;
        token.transfer(s.beneficiary, releasable);
    }
}