Retirement Fund

This retirement fund is what economists call a commitment device (opens new window). I’m trying to make sure I hold on to 1 ether for retirement.

I’ve committed 1 ether to the contract below, and I won’t withdraw it until 10 years have passed. If I do withdraw early, 10% of my ether goes to the beneficiary (you!).

I really don’t want you to have 0.1 of my ether, so I’m resolved to leave those funds alone until 10 years from now. Good luck!

// SPDX-License-Identifier: MIT
//   ref. https://capturetheether.com/challenges/math/retirement-fund/
pragma solidity ^0.8.11;

contract RetirementFund {
    uint256 startBalance;
    address owner = msg.sender;
    address beneficiary;
    uint256 expiration;

    constructor(address _player) payable {
        require(msg.value == 1 gwei);

        expiration = block.timestamp + 3650 days;
        beneficiary = _player;
        startBalance = msg.value;
    }

    function isComplete() public view returns (bool) {
        return address(this).balance == 0;
    }

    function withdraw() public {
        require(msg.sender == owner);

        if (block.timestamp < expiration) {
            // early withdrawal incurs a 10% penalty
            payable(msg.sender).transfer(address(this).balance * 9 / 10);
        } else {
            payable(msg.sender).transfer(address(this).balance);
        }
    }

    function collectPenalty() public {
        require(msg.sender == beneficiary);

        // an early withdrawal occurred
        require(startBalance != address(this).balance);

        // penalty is what's left
        payable(msg.sender).transfer(address(this).balance);
    }
}