// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

library SafeMath {
    function tryAdd(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    function trySub(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    function tryMul(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    function tryDiv(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    function tryMod(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

interface IDexRouter {
    function factory() external pure returns (address);

    function WETH() external pure returns (address);

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable;

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;
}

interface IERC20Extended {
    function totalSupply() external view returns (uint256);

    function decimals() external view returns (uint8);

    function symbol() external view returns (string memory);

    function name() external view returns (string memory);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    function allowance(address _owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

interface IDividendDistributor {
    function setDistributionCriteria(
        uint256 _minPeriod,
        uint256 _minDistribution
    ) external;

    function setShare(address shareholder, uint256 amount) external;

    function deposit() external payable;

    function process(uint256 gas) external;

    function claimDividend(address _user) external;

    function getPaidEarnings(address shareholder)
        external
        view
        returns (uint256);

    function getUnpaidEarnings(address shareholder)
        external
        view
        returns (uint256);

    function totalDistributed() external view returns (uint256);
}


contract DividendDistributor is IDividendDistributor {
    using SafeMath for uint256;

    address public token;

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

    IERC20Extended public USDC =
        IERC20Extended(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);
    IDexRouter public router;

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

    mapping(address => Share) public shares;

    uint256 public totalShares;
    uint256 public totalDividends;
    uint256 public totalDistributed;
    uint256 public dividendsPerShare;
    uint256 public dividendsPerShareAccuracyFactor = 10**36;

    uint256 public minPeriod = 1 hours;
    uint256 public minDistribution = 1 * (10**USDC.decimals());

    uint256 currentIndex;

    bool initialized;
    modifier initializer() {
        require(!initialized);
        _;
        initialized = true;
    }

    modifier onlyToken() {
        require(msg.sender == token);
        _;
    }

    constructor(address router_) {
        token = msg.sender;
        router = IDexRouter(router_);
    }

    function setDistributionCriteria(
        uint256 _minPeriod,
        uint256 _minDistribution
    ) external override onlyToken {
        minPeriod = _minPeriod;
        minDistribution = _minDistribution;
    }

    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 onlyToken {
        uint256 balanceBefore = USDC.balanceOf(address(this));

        address[] memory path = new address[](2);
        path[0] = router.WETH();
        path[1] = address(USDC);

        router.swapExactETHForTokensSupportingFeeOnTransferTokens{
            value: msg.value
        }(0, path, address(this), block.timestamp);

        uint256 amount = USDC.balanceOf(address(this)).sub(balanceBefore);

        totalDividends = totalDividends.add(amount);
        dividendsPerShare = dividendsPerShare.add(
            dividendsPerShareAccuracyFactor.mul(amount).div(totalShares)
        );
    }

    function process(uint256 gas) external override onlyToken {
        uint256 shareholderCount = shareholders.length;

        if (shareholderCount == 0) {
            return;
        }

        uint256 gasUsed = 0;
        uint256 gasLeft = gasleft();

        uint256 iterations = 0;

        while (gasUsed < gas && iterations < shareholderCount) {
            if (currentIndex >= shareholderCount) {
                currentIndex = 0;
            }

            if (shouldDistribute(shareholders[currentIndex])) {
                distributeDividend(shareholders[currentIndex]);
            }

            gasUsed = gasUsed.add(gasLeft.sub(gasleft()));
            gasLeft = gasleft();
            currentIndex++;
            iterations++;
        }
    }

    function shouldDistribute(address shareholder)
        internal
        view
        returns (bool)
    {
        return
            shareholderClaims[shareholder] + minPeriod < block.timestamp &&
            getUnpaidEarnings(shareholder) > minDistribution;
    }

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

        uint256 amount = getUnpaidEarnings(shareholder);
        if (amount > 0) {
            totalDistributed = totalDistributed.add(amount);
            USDC.transfer(shareholder, amount);
            shareholderClaims[shareholder] = block.timestamp;
            shares[shareholder].totalRealised = shares[shareholder]
                .totalRealised
                .add(amount);
            shares[shareholder].totalExcluded = getCumulativeDividends(
                shares[shareholder].amount
            );
        }
    }

    function claimDividend(address _user) external {
        distributeDividend(_user);
    }

    function getPaidEarnings(address shareholder)
        public
        view
        returns (uint256)
    {
        return shares[shareholder].totalRealised;
    }

    function getUnpaidEarnings(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();
    }
}

{
  "compilationTarget": {
    "DividendDistributor.sol": "DividendDistributor"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": false,
    "runs": 200
  },
  "remappings": []
}