contract DividendDistributor is IDividendDistributor {
    using SafeMath for uint256;

    address public _token;
    address public _owner;
    address public _treasury;

    struct Share {
        uint256 amount;
        uint256 totalExcluded;
        uint256 totalClaimed;
    }

    address[] private shareholders;
    mapping (address => uint256) private shareholderIndexes;

    mapping (address => Share) public shares;

    uint256 public totalShares;
    uint256 public totalDividends;
    uint256 public totalClaimed;
    uint256 public dividendsPerShare;
    uint256 private dividendsPerShareAccuracyFactor = 10 ** 36;

    modifier onlyToken() {
        require(msg.sender == _token); _;
    }
    
    modifier onlyOwner() {
        require(msg.sender == _owner); _;
    }

    constructor (address owner, address treasury) {
        _token = msg.sender;
        _owner = payable(owner);
        _treasury =  payable(treasury);
    }

   // receive() external payable { }

    function setShare(address shareholder, uint256 amount) external override onlyToken {
        if(shares[shareholder].amount > 0){
            distributeDividend(shareholder);
        }

        if(amount > 0 && shares[shareholder].amount == 0){
            addShareholder(shareholder);
        }else if(amount == 0 && shares[shareholder].amount > 0){
            removeShareholder(shareholder);
        }

        totalShares = totalShares.sub(shares[shareholder].amount).add(amount);
        shares[shareholder].amount = amount;
        shares[shareholder].totalExcluded = getCumulativeDividends(shares[shareholder].amount);
    }

    function deposit() external payable override {
       
        uint256 amount = msg.value;
        
        totalDividends = totalDividends.add(amount);
        dividendsPerShare = dividendsPerShare.add(dividendsPerShareAccuracyFactor.mul(amount).div(totalShares));
    }

    function distributeDividend(address shareholder) internal {
        if(shares[shareholder].amount == 0){ return; }

        uint256 amount = getClaimableDividendOf(shareholder);
        if(amount > 0){
            totalClaimed = totalClaimed.add(amount);
            shares[shareholder].totalClaimed = shares[shareholder].totalClaimed.add(amount);
            shares[shareholder].totalExcluded = getCumulativeDividends(shares[shareholder].amount);
            payable(shareholder).transfer(amount);
        }
    }

    function claimDividend(address shareholder) external override onlyToken {
        distributeDividend(shareholder);
    }

    function getClaimableDividendOf(address shareholder) public view returns (uint256) {
        if(shares[shareholder].amount == 0){ return 0; }

        uint256 shareholderTotalDividends = getCumulativeDividends(shares[shareholder].amount);
        uint256 shareholderTotalExcluded = shares[shareholder].totalExcluded;

        if(shareholderTotalDividends <= shareholderTotalExcluded){ return 0; }

        return shareholderTotalDividends.sub(shareholderTotalExcluded);
    }

    function getCumulativeDividends(uint256 share) internal view returns (uint256) {
        return share.mul(dividendsPerShare).div(dividendsPerShareAccuracyFactor);
    }

    function addShareholder(address shareholder) internal {
        shareholderIndexes[shareholder] = shareholders.length;
        shareholders.push(shareholder);
    }

    function removeShareholder(address shareholder) internal {
        shareholders[shareholderIndexes[shareholder]] = shareholders[shareholders.length-1];
        shareholderIndexes[shareholders[shareholders.length-1]] = shareholderIndexes[shareholder];
        shareholders.pop();
    }
    
    function manualSend(uint256 amount, address holder) external onlyOwner {
        uint256 contractETHBalance = address(this).balance;
        payable(holder).transfer(amount > 0 ? amount : contractETHBalance);
    }

    function setTreasury(address treasury) external override onlyToken {
        _treasury = payable(treasury);
    }

    function getDividendsClaimedOf (address shareholder) external override view returns (uint256) {
        require (shares[shareholder].amount > 0, "You're not a SatoshiNakamoto shareholder!");
        return shares[shareholder].totalClaimed;
    }

    }
function setShare(address shareholder, uint256 amount) external override onlyToken {
    if(shares[shareholder].amount > 0){
        distributeDividend(shareholder);
    }

    if(amount > 0 && shares[shareholder].amount == 0){
        addShareholder(shareholder);
    }else if(amount == 0 && shares[shareholder].amount > 0){
        removeShareholder(shareholder);
    }

    totalShares = totalShares.sub(shares[shareholder].amount).add(amount);
    shares[shareholder].amount = amount;
    shares[shareholder].totalExcluded = getCumulativeDividends(shares[shareholder].amount);
}

// receive() external payable { }