pragma solidity ^0.4.18;

contract TokenShares {
    uint private dividend;
    uint private price;
    address private owner;
    mapping(address=>uint) private sharesPerAddress;
    mapping(address=>bool) private addressesAllowedToWithdrawFunds;
    address[] private shareholders;

    function TokenShares(uint initialSupply, uint pricePerShare, uint _dividend) public {
        owner = msg.sender;
        sharesPerAddress[owner] = initialSupply;
        price = pricePerShare * 1 ether;
        dividend = _dividend * 1 ether;
    }

    function getPricePerShare() public view returns(uint) {
        return price / 1 ether;
    }

    function calculateTransactionWorth(uint amount) public view returns(uint) {
        return(amount * price) / 1 ether;
    }

    function buyShares(uint amount) public payable {
        assert(sharesPerAddress[owner] >= amount);
        assert(sharesPerAddress[msg.sender] + amount >= sharesPerAddress);??
        assert(msg.value == );???
        sharesPerAddress[owner] -= amount;
        sharesPerAddress[msg.sender] += amount;
        shareholders.push(msg.sender);
    }

    function getShareholders() public view returns(address[]) {
        require(msg.sender == owner);
        return shareholders;
    }

    function allowWithdraw(address addr) public {
        require(msg.sender == owner);
        addressesAllowedToWithdrawFunds[addr] = true;
    }

    function depositEarnings() public payable {
        require(msg.sender == owner);
    }

    function getBalance() public view returns(uint) {
        require(msg.sender == owner);
        return this.balance / 1 ether;
    }

    function getNumberOfShares(address addr) public view returns(uint) {
        require(msg.sender == addr || msg.sender == owner);
        return sharesPerAddress[addr];
    }

    function withdraw() public {
        require(sharesPerAddress[msg.sender] > 0);
        require(this.balance >= sharesPerAddress[msg.sender] * 1 ether?????);
        require(addressesAllowedToWithdrawFunds[msg.sender] == true);
        msg.sender.transfer(sharesPerAddress[msg.sender] * 1 ether ????);
        addressesAllowedToWithdrawFunds[msg.sender] = false;
    }
}