// SPDX-License-Identifier: SimPL-2.0
pragma solidity ^0.7.0;

contract DailySign {
    uint256 constant SECONDS_PER_DAY = 24 * 60 * 60;
    int256 constant OFFSET19700101 = 2440588;
    uint256 TIMEZONE_OFFSET = 28800;
    mapping(address => mapping(uint256 => bool)) public signRecords;

    function timestampToDate(uint256 timestamp)
        internal
        pure
        returns (
            uint256 year,
            uint256 month,
            uint256 day
        )
    {
        (year, month, day) = _daysToDate(timestamp / SECONDS_PER_DAY);
    }

    function _daysToDate(uint256 _days)
        internal
        pure
        returns (
            uint256 year,
            uint256 month,
            uint256 day
        )
    {
        int256 __days = int256(_days);

        int256 L = __days + 68569 + OFFSET19700101;
        int256 N = (4 * L) / 146097;
        L = L - (146097 * N + 3) / 4;
        int256 _year = (4000 * (L + 1)) / 1461001;
        L = L - (1461 * _year) / 4 + 31;
        int256 _month = (80 * L) / 2447;
        int256 _day = L - (2447 * _month) / 80;
        L = _month / 11;
        _month = _month + 2 - 12 * L;
        _year = 100 * (N - 49) + _year + L;

        year = uint256(_year);
        month = uint256(_month);
        day = uint256(_day);
    }

    function signIn() external {
        (uint256 year, uint256 month, uint256 day) = timestampToDate(
            block.timestamp + TIMEZONE_OFFSET
        );
        uint256 nowDate = year * 10000 + month * 100 + day;
        require(signRecords[msg.sender][nowDate] == false, "already signed");
        signRecords[msg.sender][nowDate] = true;
        emit SignIn(msg.sender, nowDate);
    }

    function getDate(uint256 timestamp) public view returns (uint256 date) {
        if (timestamp == 0) {
            timestamp = block.timestamp;
        }
        timestamp += TIMEZONE_OFFSET;
        (uint256 year, uint256 month, uint256 day) = timestampToDate(timestamp);
        uint256 nowDate = year * 10000 + month * 100 + day;
        return nowDate;
    }

    event SignIn(address user, uint256 date);
}

{
  "compilationTarget": {
    "contracts/dailySign.sol": "DailySign"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}