contract Debase is ERC20, Initializable {
    // PLEASE READ BEFORE CHANGING ANY ACCOUNTING OR MATH
    // Anytime there is division, there is a risk of numerical instability from rounding errors. In
    // order to minimize this risk, we adhere to the following guidelines:
    // 1) The conversion rate adopted is the number of gons that equals 1 fragment.
    //    The inverse rate must not be used--TOTAL_GONS is always the numerator and _totalSupply is
    //    always the denominator. (i.e. If you want to convert gons to fragments instead of
    //    multiplying by the inverse rate, you should divide by the normal rate)
    // 2) Gon balances converted into Fragments are always rounded down (truncated).
    //
    // We make the following guarantees:
    // - If address 'A' transfers x Fragments to address 'B'. A's resulting external balance will
    //   be decreased by precisely x Fragments, and B's external balance will be precisely
    //   increased by x Fragments.
    //
    // We do not guarantee that the sum of all balances equals the result of calling totalSupply().
    // This is because, for any conversion function 'f()' that has non-zero rounding error,
    // f(x0) + f(x1) + ... + f(xn) is not always equal to f(x0 + x1 + ... xn).
    using SafeMath for uint256;
    using SafeMathInt for int256;

    event LogRebase(uint256 indexed epoch_, uint256 totalSupply_);

    // Used for authentication
    address public debasePolicy;

    modifier onlyDebasePolicy() {
        require(msg.sender == debasePolicy);
        _;
    }

    modifier validRecipient(address to) {
        require(to != address(0x0));
        require(to != address(this));
        _;
    }

    uint256 private constant DECIMALS = 18;
    uint256 private constant MAX_UINT256 = ~uint256(0);
    uint256 private constant INITIAL_FRAGMENTS_SUPPLY = 100000 * 10**DECIMALS;

    // TOTAL_GONS is a multiple of INITIAL_FRAGMENTS_SUPPLY so that _gonsPerFragment is an integer.
    // Use the highest value that fits in a uint256 for max granularity.
    uint256 private constant TOTAL_GONS = MAX_UINT256 -
        (MAX_UINT256 % INITIAL_FRAGMENTS_SUPPLY);

    // MAX_SUPPLY = maximum integer < (sqrt(4*TOTAL_GONS + 1) - 1) / 2
    uint256 private constant MAX_SUPPLY = ~uint128(0); // (2^128) - 1

    uint256 private _totalSupply;
    uint256 private _gonsPerFragment;
    mapping(address => uint256) private _gonBalances;

    // This is denominated in Fragments, because the gons-fragments conversion might change before
    // it's fully paid.
    mapping(address => mapping(address => uint256)) private _allowedFragments;

    constructor() public ERC20("Debase", "DEBASE", uint8(DECIMALS)) {}

    /**
     * @notice Initializes with the policy,SUsdV2,susd pool as parameters. 
               The function then sets the total supply to the initial supply and calculates the gon per fragment. 
               It also sets the value and the gons for both the SUsdV2 and susd reward pools.
     * @param debaseSUsdV2Pool_ Address of the Debase SUsdV2 pool contract
     * @param debaseSUsdPool_ Address of the Debase Susd pool contract
     * @param debasePolicy_ Address of the Debase policy contract
     */
    function initialize(
        address debaseSUsdV2Pool_,
        uint256 debaseSUsdV2TotalRatio,
        address debaseSUsdPool_,
        uint256 debaseSUsdTotalRatio,
        address debasePolicy_
    ) external initializer {
        require(debaseSUsdTotalRatio.add(debaseSUsdV2TotalRatio) == 100);

        debasePolicy = debasePolicy_;

        _totalSupply = INITIAL_FRAGMENTS_SUPPLY;
        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

        uint256 debaseSUsdV2PoolVal = _totalSupply
            .mul(debaseSUsdV2TotalRatio)
            .div(100);
        uint256 debaseSUsdV2PoolGons = debaseSUsdV2PoolVal.mul(
            _gonsPerFragment
        );

        uint256 debaseSUsdPoolVal = _totalSupply.mul(debaseSUsdTotalRatio).div(
            100
        );
        uint256 debaseSUsdPoolGons = debaseSUsdPoolVal.mul(_gonsPerFragment);

        _gonBalances[debaseSUsdV2Pool_] = debaseSUsdV2PoolGons;
        _gonBalances[debaseSUsdPool_] = debaseSUsdPoolGons;

        emit Transfer(address(0x0), debaseSUsdV2Pool_, debaseSUsdV2PoolVal);
        emit Transfer(address(0x0), debaseSUsdPool_, debaseSUsdPoolVal);
    }

    /**
     * @dev Notifies Fragments contract about a new rebase cycle.
     * @param supplyDelta The number of new fragment tokens to add into circulation via expansion.
     * @return The total number of fragments after the supply adjustment.
     */
    function rebase(uint256 epoch, int256 supplyDelta)
        external
        onlyDebasePolicy
        returns (uint256)
    {
        if (supplyDelta == 0) {
            emit LogRebase(epoch, _totalSupply);
            return _totalSupply;
        }

        if (supplyDelta < 0) {
            _totalSupply = _totalSupply.sub(uint256(supplyDelta.abs()));
        } else {
            _totalSupply = _totalSupply.add(uint256(supplyDelta));
        }

        if (_totalSupply > MAX_SUPPLY) {
            _totalSupply = MAX_SUPPLY;
        }

        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

        // From this point forward, _gonsPerFragment is taken as the source of truth.
        // We recalculate a new _totalSupply to be in agreement with the _gonsPerFragment
        // conversion rate.
        // This means our applied supplyDelta can deviate from the requested supplyDelta,
        // but this deviation is guaranteed to be < (_totalSupply^2)/(TOTAL_GONS - _totalSupply).
        //
        // In the case of _totalSupply <= MAX_UINT128 (our current supply cap), this
        // deviation is guaranteed to be < 1, so we can omit this step. If the supply cap is
        // ever increased, it must be re-included.
        // _totalSupply = TOTAL_GONS.div(_gonsPerFragment)

        emit LogRebase(epoch, _totalSupply);
        return _totalSupply;
    }

    /**
     * @return The total number of fragments.
     */
    function totalSupply() public override view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @param who The address to query.
     * @return The balance of the specified address.
     */
    function balanceOf(address who) public override view returns (uint256) {
        return _gonBalances[who].div(_gonsPerFragment);
    }

    /**
     * @dev Transfer tokens to a specified address.
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     * @return True on success, false otherwise.
     */
    function transfer(address to, uint256 value)
        public
        override
        validRecipient(to)
        returns (bool)
    {
        uint256 gonValue = value.mul(_gonsPerFragment);
        _gonBalances[msg.sender] = _gonBalances[msg.sender].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(msg.sender, to, value);
        return true;
    }

    /**
     * @dev Function to check the amount of tokens that an owner has allowed to a spender.
     * @param owner_ The address which owns the funds.
     * @param spender The address which will spend the funds.
     * @return The number of tokens still available for the spender.
     */
    function allowance(address owner_, address spender)
        public
        override
        view
        returns (uint256)
    {
        return _allowedFragments[owner_][spender];
    }

    /**
     * @dev Transfer tokens from one address to another.
     * @param from The address you want to send tokens from.
     * @param to The address you want to transfer to.
     * @param value The amount of tokens to be transferred.
     */
    function transferFrom(
        address from,
        address to,
        uint256 value
    ) public override validRecipient(to) returns (bool) {
        _allowedFragments[from][msg.sender] = _allowedFragments[from][msg
            .sender]
            .sub(value);

        uint256 gonValue = value.mul(_gonsPerFragment);
        _gonBalances[from] = _gonBalances[from].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(from, to, value);

        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of
     * msg.sender. This method is included for ERC20 compatibility.
     * increaseAllowance and decreaseAllowance should be used instead.
     * Changing an allowance with this method brings the risk that someone may transfer both
     * the old and the new allowance - if they are both greater than zero - if a transfer
     * transaction is mined before the later approve() call is mined.
     *
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     */
    function approve(address spender, uint256 value)
        public
        override
        returns (bool)
    {
        _allowedFragments[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner has allowed to a spender.
     * This method should be used instead of approve() to avoid the double approval vulnerability
     * described above.
     * @param spender The address which will spend the funds.
     * @param addedValue The amount of tokens to increase the allowance by.
     */
    function increaseAllowance(address spender, uint256 addedValue)
        public
        override
        returns (bool)
    {
        _allowedFragments[msg.sender][spender] = _allowedFragments[msg
            .sender][spender]
            .add(addedValue);
        emit Approval(
            msg.sender,
            spender,
            _allowedFragments[msg.sender][spender]
        );
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner has allowed to a spender.
     *
     * @param spender The address which will spend the funds.
     * @param subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue)
        public
        override
        returns (bool)
    {
        uint256 oldValue = _allowedFragments[msg.sender][spender];
        if (subtractedValue >= oldValue) {
            _allowedFragments[msg.sender][spender] = 0;
        } else {
            _allowedFragments[msg.sender][spender] = oldValue.sub(
                subtractedValue
            );
        }
        emit Approval(
            msg.sender,
            spender,
            _allowedFragments[msg.sender][spender]
        );
        return true;
    }
}
/**
 * @title uFragments ERC20 token
 * @dev This is part of an implementation of the uFragments Ideal Money protocol.
 *      uFragments is a normal ERC20 token, but its supply can be adjusted by splitting and
 *      combining tokens proportionally across all wallets.
 *
 *      uFragment balances are internally represented with a hidden denomination, 'gons'.
 *      We support splitting the currency in expansion and combining the currency on contraction by
 *      changing the exchange rate between the hidden 'gons' and the public 'fragments'.
 */
function initialize(
    address debaseSUsdV2Pool_,
    uint256 debaseSUsdV2TotalRatio,
    address debaseSUsdPool_,
    uint256 debaseSUsdTotalRatio,
    address debasePolicy_
) external initializer {
    require(debaseSUsdTotalRatio.add(debaseSUsdV2TotalRatio) == 100);

    debasePolicy = debasePolicy_;

    _totalSupply = INITIAL_FRAGMENTS_SUPPLY;
    _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

    uint256 debaseSUsdV2PoolVal = _totalSupply
        .mul(debaseSUsdV2TotalRatio)
        .div(100);
    uint256 debaseSUsdV2PoolGons = debaseSUsdV2PoolVal.mul(
        _gonsPerFragment
    );

    uint256 debaseSUsdPoolVal = _totalSupply.mul(debaseSUsdTotalRatio).div(
        100
    );
    uint256 debaseSUsdPoolGons = debaseSUsdPoolVal.mul(_gonsPerFragment);

    _gonBalances[debaseSUsdV2Pool_] = debaseSUsdV2PoolGons;
    _gonBalances[debaseSUsdPool_] = debaseSUsdPoolGons;

    emit Transfer(address(0x0), debaseSUsdV2Pool_, debaseSUsdV2PoolVal);
    emit Transfer(address(0x0), debaseSUsdPool_, debaseSUsdPoolVal);
}

/**
 * @notice Initializes with the policy,SUsdV2,susd pool as parameters.
 The function then sets the total supply to the initial supply and calculates the gon per fragment.
 It also sets the value and the gons for both the SUsdV2 and susd reward pools.
 * @param debaseSUsdV2Pool_ Address of the Debase SUsdV2 pool contract
 * @param debaseSUsdPool_ Address of the Debase Susd pool contract
 * @param debasePolicy_ Address of the Debase policy contract
 */