106 lines
3.3 KiB
Solidity
106 lines
3.3 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.6.0;
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import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
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import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
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import "@openzeppelin/contracts/math/Math.sol";
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import "@openzeppelin/contracts/math/SafeMath.sol";
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import "./ENS.sol";
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/**
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* @title Vesting
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* @dev A token holder contract that can release its token balance gradually like a
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* typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
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* owner.
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*/
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contract Vesting is EnsResolve {
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using SafeERC20 for IERC20;
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using SafeMath for uint256;
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uint256 public constant SECONDS_PER_MONTH = 30 days;
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event Released(uint256 amount);
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// beneficiary of tokens after they are released
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address public immutable beneficiary;
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IERC20 public immutable token;
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uint256 public immutable cliffInMonths;
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uint256 public immutable startTimestamp;
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uint256 public immutable durationInMonths;
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uint256 public released;
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/**
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* @dev Creates a vesting contract that vests its balance of any ERC20 token to the
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* _beneficiary, monthly in a linear fashion until duration has passed. By then all
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* of the balance will have vested.
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* @param _beneficiary address of the beneficiary to whom vested tokens are transferred
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* @param _cliffInMonths duration in months of the cliff in which tokens will begin to vest
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* @param _durationInMonths duration in months of the period in which the tokens will vest
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*/
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constructor(
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bytes32 _token,
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address _beneficiary,
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uint256 _startTimestamp,
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uint256 _cliffInMonths,
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uint256 _durationInMonths
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) public {
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require(_beneficiary != address(0), "Beneficiary cannot be empty");
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require(_cliffInMonths <= _durationInMonths, "Cliff is greater than duration");
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token = IERC20(resolve(_token));
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beneficiary = _beneficiary;
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durationInMonths = _durationInMonths;
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cliffInMonths = _cliffInMonths;
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startTimestamp = _startTimestamp == 0 ? blockTimestamp() : _startTimestamp;
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}
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/**
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* @notice Transfers vested tokens to beneficiary.
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*/
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function release() external {
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uint256 vested = vestedAmount();
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require(vested > 0, "No tokens to release");
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released = released.add(vested);
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token.safeTransfer(beneficiary, vested);
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emit Released(vested);
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}
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/**
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* @dev Calculates the amount that has already vested but hasn't been released yet.
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*/
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function vestedAmount() public view returns (uint256) {
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if (blockTimestamp() < startTimestamp) {
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return 0;
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}
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uint256 elapsedTime = blockTimestamp().sub(startTimestamp);
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uint256 elapsedMonths = elapsedTime.div(SECONDS_PER_MONTH);
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if (elapsedMonths < cliffInMonths) {
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return 0;
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}
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// If over vesting duration, all tokens vested
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if (elapsedMonths >= durationInMonths) {
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return token.balanceOf(address(this));
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} else {
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uint256 currentBalance = token.balanceOf(address(this));
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uint256 totalBalance = currentBalance.add(released);
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uint256 vested = totalBalance.mul(elapsedMonths).div(durationInMonths);
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uint256 unreleased = vested.sub(released);
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// currentBalance can be 0 in case of vesting being revoked earlier.
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return Math.min(currentBalance, unreleased);
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}
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}
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function blockTimestamp() public view virtual returns (uint256) {
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return block.timestamp;
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}
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}
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