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106function tokensVested(address sender, uint256 timestamp) public view returns (uint256 vestedTokens) {
107    // returns 0 before (start time + cliff period)
108    // initial release is obtained after cliff
109    if (timestamp >= _startTime + _cliffPeriod) {
110        uint256 timeVestedSoFar = Math.min(timestamp - _startTime, _vestingPeriod);
111        uint256 stake = _stakes[sender].totalTokens;
112        // compute initial release as fraction where 10**18 is total
113        uint256 initialRelease = (stake * _initialReleaseFraction) / 10**18;
114        // return initial release + the remainder proportionally to time from vesting start
115        // mul first for best precision, v.8 compiler reverts on overflows
116        vestedTokens = ((stake - initialRelease) * timeVestedSoFar) / _vestingPeriod + initialRelease;
117    }
118}
119
120function release() public {
121    address sender = msg.sender;
122
123    uint256 unlockAmount = tokensVested(sender, block.timestamp) - unlockedTokensOf(sender);
124    UnlockState storage stake = _stakes[sender];
125
126    // this should never happen
127    assert(stake.totalTokens >= stake.unlockedTokens + unlockAmount);
128
129    stake.unlockedTokens += unlockAmount;
130
131    emit LogRelease(sender, unlockAmount);
132
133    token().safeTransfer(sender, unlockAmount);
134}

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78function token() public view returns (IERC20) {
79    return _token;
80}
81
82function startTime() public view returns (uint256) {
83    return _startTime;
84}
85
86function vestingPeriod() public view returns (uint256) {
87    return _vestingPeriod;
88}
89
90function initialReleaseFraction() public view returns (uint256) {
91    return _initialReleaseFraction;
92}
93
94function cliffPeriod() public view returns (uint256) {
95    return _cliffPeriod;
96}