TokenVesting

1// SPDX-License-Identifier: MIT
2pragma solidity ^0.8.20;
3 
4interface IERC20 {
5    function transfer(address to, uint256 amount) external returns (bool);
6    function balanceOf(address account) external view returns (uint256);
7}
8 
9contract TokenVesting {
10    IERC20 public immutable token;
11    address public immutable beneficiary;
12    uint256 public immutable start;
13    uint256 public immutable cliff;
14    uint256 public immutable duration;
15    uint256 public released;
16 
17    event Released(uint256 amount);
18 
19    constructor(address token_, address beneficiary_, uint256 cliffDays_, uint256 vestingDays_) {
20        require(beneficiary_ != address(0), "ZERO_BENEFICIARY");
21        require(vestingDays_ > 0, "ZERO_DURATION");
22        token = IERC20(token_);
23        beneficiary = beneficiary_;
24        start = block.timestamp;
25        cliff = block.timestamp + cliffDays_ * 1 days;
26        duration = vestingDays_ * 1 days;
27    }
28 
29    function vestedAmount() public view returns (uint256) {
30        uint256 totalBalance = token.balanceOf(address(this)) + released;
31        if (block.timestamp < cliff) return 0;
32        if (block.timestamp >= start + duration) return totalBalance;
33        return (totalBalance * (block.timestamp - start)) / duration;
34    }
35 
36    function releasable() public view returns (uint256) {
37        return vestedAmount() - released;
38    }
39 
40    function release() external {
41        uint256 amount = releasable();
42        require(amount > 0, "NOTHING_VESTED");
43        released += amount;
44        require(token.transfer(beneficiary, amount), "TRANSFER_FAILED");
45        emit Released(amount);
46    }
47}