//SPDX-License-Identifier: MIT
pragma solidity 0.8.4;
import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "./GlobalsAndUtility.sol";
import "./helpers/IERC20Burnable.sol";
contract Staking is GlobalsAndUtility {
    using SafeERC20 for IERC20Burnable;
    constructor(
        IERC20Burnable _stakingToken, // MUST BE BURNABLE
        uint40 _launchTime,
        address _originAddr
    )
    {
        require(IERC20Metadata(address(_stakingToken)).decimals() == TOKEN_DECIMALS, "STAKING: incompatible token decimals");
        //require(_launchTime >= block.timestamp, "STAKING: launch must be in future");
        require(_originAddr != address(0), "STAKING: origin address is 0");
        stakingToken = _stakingToken;
        launchTime = _launchTime;
        originAddr = _originAddr;
        /* Initialize global shareRate to 1 */
        globals.shareRate = uint40(1 * SHARE_RATE_SCALE);
    }
    /**
     * @dev PUBLIC FACING: Open a stake.
     * @param newStakedAmount Amount of staking token to stake
     * @param newStakedDays Number of days to stake
     */
    function stakeStart(uint256 newStakedAmount, uint256 newStakedDays)
        external
    {
        GlobalsCache memory g;
        _globalsLoad(g);
        /* Enforce the minimum stake time */
        require(newStakedDays >= MIN_STAKE_DAYS, "STAKING: newStakedDays lower than minimum");
        /* Enforce the maximum stake time */
        require(newStakedDays <= MAX_STAKE_DAYS, "STAKING: newStakedDays higher than maximum");
        /* Check if log data needs to be updated */
        _dailyDataUpdateAuto(g);
        _stakeStart(g, newStakedAmount, newStakedDays);
        /* Remove staked amount from balance of staker */
        stakingToken.safeTransferFrom(msg.sender, address(this), newStakedAmount);
        _globalsSync(g);
    }
    /**
     * @dev PUBLIC FACING: Unlocks a completed stake, distributing the proceeds of any penalty
     * immediately. The staker must still call stakeEnd() to retrieve their stake return (if any).
     * @param stakerAddr Address of staker
     * @param stakeIndex Index of stake within stake list
     * @param stakeIdParam The stake's id
     */
    function stakeGoodAccounting(address stakerAddr, uint256 stakeIndex, uint40 stakeIdParam)
        external
    {
        GlobalsCache memory g;
        _globalsLoad(g);
        /* require() is more informative than the default assert() */
        require(stakeLists[stakerAddr].length != 0, "STAKING: Empty stake list");
        require(stakeIndex < stakeLists[stakerAddr].length, "STAKING: stakeIndex invalid");
        StakeStore storage stRef = stakeLists[stakerAddr][stakeIndex];
        /* Get stake copy */
        StakeCache memory st;
        _stakeLoad(stRef, stakeIdParam, st);
        /* Stake must have served full term */
        require(g._currentDay >= st._lockedDay + st._stakedDays, "STAKING: Stake not fully served");
        /* Stake must still be locked */
        require(st._unlockedDay == 0, "STAKING: Stake already unlocked");
        /* Check if log data needs to be updated */
        _dailyDataUpdateAuto(g);
        /* Unlock the completed stake */
        _stakeUnlock(g, st);
        /* stakeReturn value is unused here */
        (, uint256 payout, uint256 penalty, uint256 cappedPenalty) = _stakePerformance(
            st,
            st._stakedDays
        );
        emit StakeGoodAccounting(
            stakerAddr,
            stakeIdParam,
            msg.sender,
            uint40(block.timestamp),
            uint128(st._stakedAmount),
            uint128(st._stakeShares),
            uint128(payout),
            uint128(penalty)
        );
        if (cappedPenalty != 0) {
            _splitPenaltyProceeds(g, cappedPenalty);
        }
        /* st._unlockedDay has changed */
        _stakeUpdate(stRef, st);
        _globalsSync(g);
    }
    /**
     * @dev PUBLIC FACING: Closes a stake. The order of the stake list can change so
     * a stake id is used to reject stale indexes.
     * @param stakeIndex Index of stake within stake list
     * @param stakeIdParam The stake's id
     * @return stakeReturn payout penalty
     */
    function stakeEnd(uint256 stakeIndex, uint40 stakeIdParam)
        external
        returns (uint256 stakeReturn, uint256 payout, uint256 penalty, uint256 cappedPenalty)
    {
        GlobalsCache memory g;
        _globalsLoad(g);
        StakeStore[] storage stakeListRef = stakeLists[msg.sender];
        /* require() is more informative than the default assert() */
        require(stakeListRef.length != 0, "STAKING: Empty stake list");
        require(stakeIndex < stakeListRef.length, "STAKING: stakeIndex invalid");
        /* Get stake copy */
        StakeCache memory st;
        _stakeLoad(stakeListRef[stakeIndex], stakeIdParam, st);
        /* Check if log data needs to be updated */
        _dailyDataUpdateAuto(g);
        require(g._currentDay >= st._lockedDay + HARD_LOCK_DAYS, "STAKING: hard lock period");
        uint256 servedDays = 0;
        bool prevUnlocked = (st._unlockedDay != 0);
        if (prevUnlocked) {
            /* Previously unlocked in stakeGoodAccounting(), so must have served full term */
            servedDays = st._stakedDays;
        } else {
            _stakeUnlock(g, st);
            servedDays = g._currentDay - st._lockedDay;
            if (servedDays > st._stakedDays) {
                servedDays = st._stakedDays;
            }
        }
        (stakeReturn, payout, penalty, cappedPenalty) = _stakePerformance(st, servedDays);
        emit StakeEnd(
            msg.sender,
            stakeIdParam,
            uint40(block.timestamp),
            uint128(st._stakedAmount),
            uint128(st._stakeShares),
            uint128(payout),
            uint128(penalty),
            uint16(servedDays),
            prevUnlocked
        );
        if (cappedPenalty != 0 && !prevUnlocked) {
            /* Split penalty proceeds only if not previously unlocked by stakeGoodAccounting() */
            _splitPenaltyProceeds(g, cappedPenalty);
        }
        /* Pay the stake return, if any, to the staker */
        if (stakeReturn != 0) {
            stakingToken.safeTransfer(msg.sender, stakeReturn);
            /* Update the share rate if necessary */
            _shareRateUpdate(g, st, stakeReturn);
        }
        g._lockedStakeTotal -= st._stakedAmount;
        _stakeRemove(stakeListRef, stakeIndex);
        _globalsSync(g);
        return (
            stakeReturn,
            payout,
            penalty,
            cappedPenalty
        );
    }
 
    function fundRewards(
        uint128 amountPerDay,
        uint16 daysCount,
        uint16 shiftInDays
    )
        external
    {
        require(daysCount <= 365, "STAKING: too many days");
        stakingToken.safeTransferFrom(msg.sender, address(this), amountPerDay * daysCount);
        uint256 currentDay = _currentDay() + 1;
        uint256 fromDay = currentDay + shiftInDays;
        for (uint256 day = fromDay; day < fromDay + daysCount; day++) {
            dailyData[day].dayPayoutTotal += amountPerDay;
        }
        emit RewardsFund(amountPerDay, daysCount, shiftInDays);
    }
    /**
     * @dev PUBLIC FACING: Return the current stake count for a staker address
     * @param stakerAddr Address of staker
     */
    function stakeCount(address stakerAddr)
        external
        view
        returns (uint256)
    {
        return stakeLists[stakerAddr].length;
    }
    /**
     * @dev Open a stake.
     * @param g Cache of stored globals
     * @param newStakedAmount Amount of staking token to stake
     * @param newStakedDays Number of days to stake
     */
    function _stakeStart(
        GlobalsCache memory g,
        uint256 newStakedAmount,
        uint256 newStakedDays
    )
        internal
    {
        uint256 bonusShares = stakeStartBonusShares(newStakedAmount, newStakedDays);
        uint256 newStakeShares = (newStakedAmount + bonusShares) * SHARE_RATE_SCALE / g._shareRate;
        /* Ensure newStakedAmount is enough for at least one stake share */
        require(newStakeShares != 0, "STAKING: newStakedAmount must be at least minimum shareRate");
        /*
            The stakeStart timestamp will always be part-way through the current
            day, so it needs to be rounded-up to the next day to ensure all
            stakes align with the same fixed calendar days. The current day is
            already rounded-down, so rounded-up is current day + 1.
        */
        uint256 newLockedDay = g._currentDay + 1;
        /* Create Stake */
        uint40 newStakeId = ++g._latestStakeId;
        _stakeAdd(
            stakeLists[msg.sender],
            newStakeId,
            newStakedAmount,
            newStakeShares,
            newLockedDay,
            newStakedDays
        );
        emit StakeStart(
            msg.sender,
            newStakeId,
            uint40(block.timestamp),
            uint128(newStakedAmount),
            uint128(newStakeShares),
            uint16(newStakedDays)
        );
        /* Stake is added to total in the next round, not the current round */
        g._nextStakeSharesTotal += newStakeShares;
        /* Track total staked amount for inflation calculations */
        g._lockedStakeTotal += newStakedAmount;
        /* Remove his share from the pool when his stake ends */
        dailyData[newLockedDay + newStakedDays].sharesToBeRemoved += uint128(newStakeShares);
    }
    /* 
    Returns the same values as function stakeEnd. However, this function makes 
    it possible to anyone view the stakeReturn etc. for any staker. 
    The results can be obsolete if there are no daily updates.
    */
    function getStakeStatus(
        address staker, 
        uint256 stakeIndex, 
        uint40 stakeIdParam
    ) 
        external
        view
        returns (uint256 stakeReturn, uint256 payout, uint256 penalty, uint256 cappedPenalty)
    {
        GlobalsCache memory g;
        _globalsLoad(g);
        StakeStore[] storage stakeListRef = stakeLists[staker];
        require(stakeListRef.length != 0, "STAKING: Empty stake list");
        require(stakeIndex < stakeListRef.length, "STAKING: stakeIndex invalid");
        StakeCache memory st;
        _stakeLoad(stakeListRef[stakeIndex], stakeIdParam, st);
        require(g._currentDay >= st._lockedDay + HARD_LOCK_DAYS, "STAKING: hard lock period");
        uint256 servedDays = 0;
        bool prevUnlocked = (st._unlockedDay != 0);
        if (prevUnlocked) {
            servedDays = st._stakedDays;
        } else {
            st._unlockedDay = g._currentDay;
            servedDays = g._currentDay - st._lockedDay;
            if (servedDays > st._stakedDays) {
                servedDays = st._stakedDays;
            }
        }
        (stakeReturn, payout, penalty, cappedPenalty) = _stakePerformance(st, servedDays);
    }
    /**
     * @dev Calculates total stake payout including rewards for a multi-day range
     * @param stakeSharesParam Param from stake to calculate bonuses for
     * @param beginDay First day to calculate bonuses for
     * @param endDay Last day (non-inclusive) of range to calculate bonuses for
     * @return payout
     */
    function _calcPayoutRewards(
        uint256 stakeSharesParam,
        uint256 beginDay,
        uint256 endDay
    )
        private
        view
        returns (uint256 payout)
    {
        uint256 accRewardPerShare = dailyData[endDay - 1].accRewardPerShare - dailyData[beginDay - 1].accRewardPerShare;
        payout = stakeSharesParam * accRewardPerShare / ACC_REWARD_MULTIPLIER;
        return payout;
    }
    /**
     * @dev Calculate bonus shares for a new stake, if any
     * @param newStakedAmount Amount of staking token
     * @param newStakedDays Number of days to stake
     */
    function stakeStartBonusShares(uint256 newStakedAmount, uint256 newStakedDays)
        public
        pure
        returns (uint256 bonusShares)
    {
        uint256 cappedExtraDays = 0;
        /* Must be more than 1 day for Longer-Pays-Better */
        if (newStakedDays > 1) {
            cappedExtraDays = newStakedDays <= LPB_MAX_DAYS ? newStakedDays - 1 : LPB_MAX_DAYS;
        }
        uint256 cappedStakedAmount = newStakedAmount >= BPB_FROM_AMOUNT ? newStakedAmount - BPB_FROM_AMOUNT : 0;
        if (cappedStakedAmount > BPB_MAX) {
            cappedStakedAmount = BPB_MAX;
        }
        bonusShares = cappedExtraDays * BPB + cappedStakedAmount * LPB;
        bonusShares = newStakedAmount * bonusShares / (LPB * BPB);
        return bonusShares;
    }
    function _stakeUnlock(GlobalsCache memory g, StakeCache memory st)
        private
    {
        st._unlockedDay = g._currentDay;
        uint256 endDay = st._lockedDay + st._stakedDays;
        
        if (g._currentDay <= endDay) {
            dailyData[endDay].sharesToBeRemoved -= uint128(st._stakeShares);
            g._stakeSharesTotal -= st._stakeShares;
        }
    }
    function _stakePerformance(StakeCache memory st, uint256 servedDays)
        private
        view
        returns (uint256 stakeReturn, uint256 payout, uint256 penalty, uint256 cappedPenalty)
    {
        if (servedDays < st._stakedDays) {
            (payout, penalty) = _calcPayoutAndEarlyPenalty(
                st._lockedDay,
                st._stakedDays,
                servedDays,
                st._stakeShares
            );
            stakeReturn = st._stakedAmount + payout;
        } else {
            // servedDays must == stakedDays here
            payout = _calcPayoutRewards(
                st._stakeShares,
                st._lockedDay,
                st._lockedDay + servedDays
            );
            stakeReturn = st._stakedAmount + payout;
            penalty = _calcLatePenalty(st._lockedDay, st._stakedDays, st._unlockedDay, stakeReturn);
        }
        if (penalty != 0) {
            if (penalty > stakeReturn) {
                /* Cannot have a negative stake return */
                cappedPenalty = stakeReturn;
                stakeReturn = 0;
            } else {
                /* Remove penalty from the stake return */
                cappedPenalty = penalty;
                stakeReturn -= cappedPenalty;
            }
        }
        return (stakeReturn, payout, penalty, cappedPenalty);
    }
    function _calcPayoutAndEarlyPenalty(
        uint256 lockedDayParam,
        uint256 stakedDaysParam,
        uint256 servedDays,
        uint256 stakeSharesParam
    )
        private
        view
        returns (uint256 payout, uint256 penalty)
    {
        uint256 servedEndDay = lockedDayParam + servedDays;
        /* 50% of stakedDays (rounded up) with a minimum applied */
        uint256 penaltyDays = (stakedDaysParam + 1) / 2;
        if (penaltyDays < EARLY_PENALTY_MIN_DAYS) {
            penaltyDays = EARLY_PENALTY_MIN_DAYS;
        }
        if (penaltyDays < servedDays) {
            /*
                Simplified explanation of intervals where end-day is non-inclusive:
                penalty:    [lockedDay  ...  penaltyEndDay)
                delta:                      [penaltyEndDay  ...  servedEndDay)
                payout:     [lockedDay  .......................  servedEndDay)
            */
            uint256 penaltyEndDay = lockedDayParam + penaltyDays;
            penalty = _calcPayoutRewards(stakeSharesParam, lockedDayParam, penaltyEndDay);
            uint256 delta = _calcPayoutRewards(stakeSharesParam, penaltyEndDay, servedEndDay);
            payout = penalty + delta;
            return (payout, penalty);
        }
        /* penaltyDays >= servedDays  */
        payout = _calcPayoutRewards(stakeSharesParam, lockedDayParam, servedEndDay);
        if (penaltyDays == servedDays) {
            penalty = payout;
        } else {
            /*
                (penaltyDays > servedDays) means not enough days served, so fill the
                penalty days with the average payout from only the days that were served.
            */
            penalty = payout * penaltyDays / servedDays;
        }
        return (payout, penalty);
    }
    function _calcLatePenalty(
        uint256 lockedDayParam,
        uint256 stakedDaysParam,
        uint256 unlockedDayParam,
        uint256 rawStakeReturn
    )
        private
        pure
        returns (uint256)
    {
        /* Allow grace time before penalties accrue */
        uint256 maxUnlockedDay = lockedDayParam + stakedDaysParam + LATE_PENALTY_GRACE_DAYS;
        if (unlockedDayParam <= maxUnlockedDay) {
            return 0;
        }
        /* Calculate penalty as a percentage of stake return based on time */
        return rawStakeReturn * (unlockedDayParam - maxUnlockedDay) / LATE_PENALTY_SCALE_DAYS;
    }
    function _splitPenaltyProceeds(GlobalsCache memory g, uint256 penalty)
        private
    {
        /* Split a penalty 50:50 between (Origin + burn) and stakePenaltyTotal */
        uint256 splitPenalty = penalty / 2;
        if (splitPenalty != 0) {
            //30% of the total penalty is sent to origin address
            uint256 originPenalty = splitPenalty * 3 / 5;
            stakingToken.safeTransfer(originAddr, originPenalty);
            //20% of the total penalty is burned
            stakingToken.burn(splitPenalty - originPenalty);
        }
        /* Use the other half of the penalty to account for an odd-numbered penalty */
        splitPenalty = penalty - splitPenalty;
        g._stakePenaltyTotal += splitPenalty;
    }
    function _shareRateUpdate(GlobalsCache memory g, StakeCache memory st, uint256 stakeReturn)
        private
    {
        if (stakeReturn > st._stakedAmount) {
            /*
                Calculate the new shareRate that would yield the same number of shares if
                the user re-staked this stakeReturn, factoring in any bonuses they would
                receive in stakeStart().
            */
            uint256 bonusShares = stakeStartBonusShares(stakeReturn, st._stakedDays);
            uint256 newShareRate = (stakeReturn + bonusShares) * SHARE_RATE_SCALE / st._stakeShares;
            if (newShareRate > SHARE_RATE_MAX) {
                /*
                    Realistically this can't happen, but there are contrived theoretical
                    scenarios that can lead to extreme values of newShareRate, so it is
                    capped to prevent them anyway.
                */
                newShareRate = SHARE_RATE_MAX;
            }
            if (newShareRate > g._shareRate) {
                g._shareRate = newShareRate;
                emit ShareRateChange(
                    st._stakeId,
                    uint40(block.timestamp),
                    uint40(newShareRate)
                );
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "../IERC20.sol";
/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);
    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);
    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "../IERC20.sol";
import "../../../utils/Address.sol";
/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;
    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }
    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }
    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }
    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }
    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.
        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}
//SPDX-License-Identifier: MIT
pragma solidity 0.8.4;
import "./helpers/IERC20Burnable.sol";
abstract contract GlobalsAndUtility {
    event DailyDataUpdate(
        address indexed updaterAddr,
        uint40 timestamp,
        uint16 beginDay,
        uint16 endDay,
        bool isAutoUpdate
    );
    event StakeStart(
        address indexed stakerAddr,
        uint40 indexed stakeId,
        uint40 timestamp,
        uint128 stakedAmount,
        uint128 stakeShares,
        uint16 stakedDays
    );
    event StakeGoodAccounting(        
        address indexed stakerAddr,
        uint40 indexed stakeId,
        address indexed senderAddr,
        uint40 timestamp,
        uint128 stakedAmount,
        uint128 stakeShares,
        uint128 payout,
        uint128 penalty
    );
    event StakeEnd(
        address indexed stakerAddr,
        uint40 indexed stakeId,
        uint40 timestamp,
        uint128 stakedAmount,
        uint128 stakeShares,
        uint128 payout,
        uint128 penalty,
        uint16 servedDays,
        bool prevUnlocked
    );
    event ShareRateChange(
        uint40 indexed stakeId,
        uint40 timestamp,
        uint40 shareRate
    );
    event RewardsFund(
        uint128 amountPerDay,
        uint16 daysCount,
        uint16 shiftInDays
    );
    IERC20Burnable public stakingToken;
    uint40 public launchTime;
    address public originAddr;
    uint256 internal constant ACC_REWARD_MULTIPLIER = 1e36;
    uint256 internal constant TOKEN_DECIMALS = 18;
    /* Stake timing parameters */
    uint256 internal constant HARD_LOCK_DAYS = 14;
    uint256 internal constant MIN_STAKE_DAYS = 30;
    uint256 internal constant MAX_STAKE_DAYS = 1095;
    uint256 internal constant EARLY_PENALTY_MIN_DAYS = 30;
    uint256 internal constant LATE_PENALTY_GRACE_DAYS = 30;
    uint256 internal constant LATE_PENALTY_SCALE_DAYS = 100;
    /* Stake shares Longer Pays Better bonus constants used by _stakeStartBonusShares() */
    uint256 private constant LPB_BONUS_PERCENT = 600;
    uint256 private constant LPB_BONUS_MAX_PERCENT = 1800;
    uint256 internal constant LPB = 364 * 100 / LPB_BONUS_PERCENT;
    uint256 internal constant LPB_MAX_DAYS = LPB * LPB_BONUS_MAX_PERCENT / 100;
    /* Stake shares Bigger Pays Better bonus constants used by _stakeStartBonusShares() */
    uint256 private constant BPB_BONUS_PERCENT = 50;
    uint256 internal constant BPB_MAX = 1e6 * 10 ** TOKEN_DECIMALS;
    uint256 internal constant BPB = BPB_MAX * 100 / BPB_BONUS_PERCENT;
    uint256 internal constant BPB_FROM_AMOUNT = 50000 * 10 ** TOKEN_DECIMALS;
    /* Share rate is scaled to increase precision */
    uint256 internal constant SHARE_RATE_SCALE = 1e5;
    /* Share rate max (after scaling) */
    uint256 internal constant SHARE_RATE_UINT_SIZE = 40;
    uint256 internal constant SHARE_RATE_MAX = (1 << SHARE_RATE_UINT_SIZE) - 1;
    /* Globals expanded for memory (except _latestStakeId) and compact for storage */
    struct GlobalsCache {
        uint256 _lockedStakeTotal;
        uint256 _nextStakeSharesTotal;
        uint256 _stakePenaltyTotal;
        uint256 _stakeSharesTotal;
        uint40 _latestStakeId;
        uint256 _shareRate;
        uint256 _dailyDataCount;
        uint256 _currentDay;
    }
    struct GlobalsStore {
        uint128 lockedStakeTotal;
        uint128 nextStakeSharesTotal;
        uint128 stakePenaltyTotal;
        uint128 stakeSharesTotal;
        uint40 latestStakeId;
        uint40 shareRate;
        uint16 dailyDataCount;
    }
    GlobalsStore public globals;
    /* Daily data */
    struct DailyDataStore {
        uint128 dayPayoutTotal;
        uint128 sharesToBeRemoved;
        uint256 accRewardPerShare;
    }
    mapping(uint256 => DailyDataStore) public dailyData;
    /* Stake expanded for memory (except _stakeId) and compact for storage */
    struct StakeCache {
        uint256 _stakedAmount;
        uint256 _stakeShares;
        uint40 _stakeId;
        uint256 _lockedDay;
        uint256 _stakedDays;
        uint256 _unlockedDay;
    }
    struct StakeStore {
        uint128 stakedAmount;
        uint128 stakeShares;
        uint40 stakeId;
        uint16 lockedDay;
        uint16 stakedDays;
        uint16 unlockedDay;
    }
    mapping(address => StakeStore[]) public stakeLists;
    /* Temporary state for calculating daily rounds */
    struct DailyRoundState {
        uint256 _payoutTotal;
        uint256 _accRewardPerShare;
    }
    /**
     * @dev PUBLIC FACING: Optionally update daily data for a smaller
     * range to reduce gas cost for a subsequent operation
     * @param beforeDay Only update days before this day number (optional; 0 for current day)
     */
    function dailyDataUpdate(uint256 beforeDay)
        external
    {
        GlobalsCache memory g;
        _globalsLoad(g);
        if (beforeDay != 0) {
            require(beforeDay <= g._currentDay, "STAKING: beforeDay cannot be in the future");
            _dailyDataUpdate(g, beforeDay, false);
        } else {
            /* Default to updating before current day */
            _dailyDataUpdate(g, g._currentDay, false);
        }
        _globalsSync(g);
    }
    /**
     * @dev PUBLIC FACING: External helper to return multiple values of daily data with
     * a single call. Ugly implementation due to limitations of the standard ABI encoder.
     * @param beginDay First day of data range
     * @param endDay Last day (non-inclusive) of data range
     * @return listDayAccRewardPerShare and listDayPayoutTotal
     */
    function dailyDataRange(uint256 beginDay, uint256 endDay)
        external
        view
        returns (uint256[] memory listDayAccRewardPerShare, uint256[] memory listDayPayoutTotal)
    {
        require(beginDay < endDay, "STAKING: range invalid");
        listDayAccRewardPerShare = new uint256[](endDay - beginDay);
        listDayPayoutTotal = new uint256[](endDay - beginDay);
        uint256 src = beginDay;
        uint256 dst = 0;
        do {
            listDayAccRewardPerShare[dst] = dailyData[src].accRewardPerShare;
            listDayPayoutTotal[dst++] = dailyData[src].dayPayoutTotal;
        } while (++src < endDay);
    }
    /**
     * @dev PUBLIC FACING: External helper to return most global info with a single call.
     * @return global variables
     */
    function globalInfo()
        external
        view
        returns (GlobalsCache memory)
    {
        GlobalsCache memory g;
        _globalsLoad(g);
        return g;
    }
    /**
     * @dev PUBLIC FACING: External helper for the current day number since launch time
     * @return Current day number (zero-based)
     */
    function currentDay()
        external
        view
        returns (uint256)
    {
        return _currentDay();
    }
    function _currentDay()
        internal
        view
        returns (uint256)
    {
        return (block.timestamp - launchTime) / 1 days;
    }
    function _dailyDataUpdateAuto(GlobalsCache memory g)
        internal
    {
        _dailyDataUpdate(g, g._currentDay, true);
    }
    function _globalsLoad(GlobalsCache memory g)
        internal
        view
    {
        g._lockedStakeTotal = globals.lockedStakeTotal;
        g._nextStakeSharesTotal = globals.nextStakeSharesTotal;
        g._stakeSharesTotal = globals.stakeSharesTotal;
        g._stakePenaltyTotal = globals.stakePenaltyTotal;
        g._latestStakeId = globals.latestStakeId;
        g._shareRate = globals.shareRate;
        g._dailyDataCount = globals.dailyDataCount;
        
        g._currentDay = _currentDay();
    }
    function _globalsSync(GlobalsCache memory g)
        internal
    {
        globals.lockedStakeTotal = uint128(g._lockedStakeTotal);
        globals.nextStakeSharesTotal = uint128(g._nextStakeSharesTotal);
        globals.stakeSharesTotal = uint128(g._stakeSharesTotal);
        globals.stakePenaltyTotal = uint128(g._stakePenaltyTotal);
        globals.latestStakeId = g._latestStakeId;
        globals.shareRate = uint40(g._shareRate);
        globals.dailyDataCount = uint16(g._dailyDataCount);
    }
    function _stakeLoad(StakeStore storage stRef, uint40 stakeIdParam, StakeCache memory st)
        internal
        view
    {
        /* Ensure caller's stakeIndex is still current */
        require(stakeIdParam == stRef.stakeId, "STAKING: stakeIdParam not in stake");
        st._stakedAmount = stRef.stakedAmount;
        st._stakeShares = stRef.stakeShares;
        st._stakeId = stRef.stakeId;
        st._lockedDay = stRef.lockedDay;
        st._stakedDays = stRef.stakedDays;
        st._unlockedDay = stRef.unlockedDay;
    }
    function _stakeUpdate(StakeStore storage stRef, StakeCache memory st)
        internal
    {
        stRef.stakedAmount = uint128(st._stakedAmount);
        stRef.stakeShares = uint128(st._stakeShares);
        stRef.stakeId = st._stakeId;
        stRef.lockedDay = uint16(st._lockedDay);
        stRef.stakedDays = uint16(st._stakedDays);
        stRef.unlockedDay = uint16(st._unlockedDay);
    }
    function _stakeAdd(
        StakeStore[] storage stakeListRef,
        uint40 newStakeId,
        uint256 newstakedAmount,
        uint256 newStakeShares,
        uint256 newLockedDay,
        uint256 newStakedDays
    )
        internal
    {
        stakeListRef.push(
            StakeStore(
                uint128(newstakedAmount),
                uint128(newStakeShares),
                newStakeId,
                uint16(newLockedDay),
                uint16(newStakedDays),
                uint16(0) // unlockedDay
            )
        );
    }
    /**
     * @dev Efficiently delete from an unordered array by moving the last element
     * to the "hole" and reducing the array length. Can change the order of the list
     * and invalidate previously held indexes.
     * @notice stakeListRef length and stakeIndex are already ensured valid in stakeEnd()
     * @param stakeListRef Reference to stakeLists[stakerAddr] array in storage
     * @param stakeIndex Index of the element to delete
     */
    function _stakeRemove(StakeStore[] storage stakeListRef, uint256 stakeIndex)
        internal
    {
        uint256 lastIndex = stakeListRef.length - 1;
        /* Skip the copy if element to be removed is already the last element */
        if (stakeIndex != lastIndex) {
            /* Copy last element to the requested element's "hole" */
            stakeListRef[stakeIndex] = stakeListRef[lastIndex];
        }
        stakeListRef.pop();
    }
    function _dailyRoundCalc(GlobalsCache memory g, DailyRoundState memory rs, uint256 day)
        private
        view
    {
        rs._payoutTotal = dailyData[day].dayPayoutTotal;
        rs._accRewardPerShare = day == 0 ? 0 : dailyData[day - 1].accRewardPerShare;
        if (g._stakePenaltyTotal != 0) {
            rs._payoutTotal += g._stakePenaltyTotal;
            g._stakePenaltyTotal = 0;
        }
        if (g._stakeSharesTotal > 0) {
            rs._accRewardPerShare += rs._payoutTotal * ACC_REWARD_MULTIPLIER / g._stakeSharesTotal;
        }
    }
    function _dailyRoundCalcAndStore(GlobalsCache memory g, DailyRoundState memory rs, uint256 day)
        private
    {
        g._stakeSharesTotal -= dailyData[day].sharesToBeRemoved;
        _dailyRoundCalc(g, rs, day);
        dailyData[day].accRewardPerShare = rs._accRewardPerShare;
        if (g._stakeSharesTotal > 0) {
            dailyData[day].dayPayoutTotal = uint128(rs._payoutTotal);
        } else {
            // nobody staking that day, move the reward to the next day if any
            dailyData[day + 1].dayPayoutTotal += uint128(rs._payoutTotal);
        }
    }
    function _dailyDataUpdate(GlobalsCache memory g, uint256 beforeDay, bool isAutoUpdate)
        private
    {
        if (g._dailyDataCount >= beforeDay) {
            /* Already up-to-date */
            return;
        }
        DailyRoundState memory rs;
        uint256 day = g._dailyDataCount;
        _dailyRoundCalcAndStore(g, rs, day);
        /* Stakes started during this day are added to the total the next day */
        if (g._nextStakeSharesTotal != 0) {
            g._stakeSharesTotal += g._nextStakeSharesTotal;
            g._nextStakeSharesTotal = 0;
        }
        while (++day < beforeDay) {
            _dailyRoundCalcAndStore(g, rs, day);
        }
        emit DailyDataUpdate(
            msg.sender,
            uint40(block.timestamp),
            uint16(g._dailyDataCount),
            uint16(day),
            isAutoUpdate
        );
        g._dailyDataCount = day;
    }
}
//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
interface IERC20Burnable is IERC20 {
    function burn(uint256 amount) external;
}// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/IERC20.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through `transferFrom`. This is
     * zero by default.
     *
     * This value changes when `approve` or `transferFrom` are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an `Approval` event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to `approve`. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // 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-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

pragma solidity ^0.5.0;



/**
 * @dev Implementation of the `IERC20` interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using `_mint`.
 * For a generic mechanism see `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an `Approval` event is emitted on calls to `transferFrom`.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard `decreaseAllowance` and `increaseAllowance`
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See `IERC20.approve`.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    /**
     * @dev See `IERC20.totalSupply`.
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IERC20.transfer`.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IERC20.allowance`.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IERC20.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of `ERC20`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to `transfer`, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a `Transfer` event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a `Transfer` event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

     /**
     * @dev Destoys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a `Transfer` event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an `Approval` event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Destoys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See `_burn` and `_approve`.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, msg.sender, _allowances[account][msg.sender].sub(amount));
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20Detailed.sol

pragma solidity ^0.5.0;


/**
 * @dev Optional functions from the ERC20 standard.
 */
contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for `name`, `symbol`, and `decimals`. All three of
     * these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei.
     *
     * > Note that this information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * `IERC20.balanceOf` and `IERC20.transfer`.
     */
    function decimals() public view returns (uint8) {
        return _decimals;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20Burnable.sol

pragma solidity ^0.5.0;


/**
 * @dev Extension of `ERC20` that allows token holders to destroy both their own
 * tokens and those that they have an allowance for, in a way that can be
 * recognized off-chain (via event analysis).
 */
contract ERC20Burnable is ERC20 {
    /**
     * @dev Destoys `amount` tokens from the caller.
     *
     * See `ERC20._burn`.
     */
    function burn(uint256 amount) public {
        _burn(msg.sender, amount);
    }

    /**
     * @dev See `ERC20._burnFrom`.
     */
    function burnFrom(address account, uint256 amount) public {
        _burnFrom(account, amount);
    }
}

// File: openzeppelin-solidity/contracts/ownership/Ownable.sol

pragma solidity ^0.5.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be aplied to your functions to restrict their use to
 * the owner.
 */
contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), _owner);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * > Note: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: contracts/Token.sol

pragma solidity ^0.5.0;





contract Token is ERC20, ERC20Detailed, ERC20Burnable, Ownable {

    string private _name = "DAO Maker Token";
    string private constant _symbol = "DAO";
    uint   private constant _numTokens = 312000000;
    
    event NameChanged(string newName, address by);

    constructor () public ERC20Detailed(_name, _symbol, 18) {
        _mint(msg.sender, _numTokens * (10 ** uint256(decimals())));
    }
    
    function changeName(string memory name) public onlyOwner{
        _name = name;
        emit NameChanged(name, msg.sender);
    }
    
    function name() public view returns (string memory) {
        return _name;
    }
}