whitelisted, conditioned, time-restricted

gistfile1.txt

// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/// @notice Basic ERC20 implementation.
contract TestERC20 {
    string public name;
    string public symbol;
    uint8 constant public decimals = 18;
    uint256 public totalSupply;
    uint256 public deadline;

    address public owner;

    bool public thingHappened;
    
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;

    mapping(address => bool) public whitelisted;
    
    event Transfer(address indexed from, address indexed to, uint amount);
    event Approval(address indexed owner, address indexed spender, uint amount);
    
    constructor(string memory _name, string memory _symbol, uint _totalSupply, uint256 _deadline, address account) {
        name = _name;
        symbol = _symbol;
        totalSupply = _totalSupply;
        deadline = _deadline;
        balanceOf[msg.sender] = _totalSupply;
        thingHappened = false;
        owner = msg.sender;
        whitelisted[account] = true;
        emit Transfer(address(0), msg.sender, _totalSupply);
    }

    modifier TimePassed {
        require(block.timestamp > deadline);

        _;
    }

    modifier OnlyOwner {
        require(msg.sender == owner);

        _;
    }

    modifier ThingHappened {
        require(thingHappened);

        _;
    }

    modifier OnlyWhitelisted(address from, address to) {
        require(whitelisted[from] && whitelisted[to]);

        _;
    }
    
    function approve(address to, uint amount) external TimePassed OnlyWhitelisted(msg.sender, to) ThingHappened returns (bool) {
        allowance[msg.sender][to] = amount;
        emit Approval(msg.sender, to, amount);
        return true;
    }
    
    function transfer(address to, uint amount) external TimePassed OnlyWhitelisted(msg.sender, to) ThingHappened returns (bool) {
        balanceOf[msg.sender] -= amount;
        balanceOf[to] += amount;
        emit Transfer(msg.sender, to, amount);
        return true;
    }
    
    function transferFrom(address from, address to, uint amount) external TimePassed OnlyWhitelisted(from, to) ThingHappened returns (bool) {
        if (allowance[from][msg.sender] != type(uint).max) 
            allowance[from][msg.sender] -= amount;
        balanceOf[from] -= amount;
        balanceOf[to] += amount;
        emit Transfer(from, to, amount);
        return true;
    }

    function addToWhitelist(address account) external OnlyOwner {
        whitelisted[account] = true;
    }

    function addOwner(address account) external OnlyOwner {
        owner = account;
    }

    function sayThingHappened() external OnlyOwner {
        thingHappened = true;
    }
}