// File: contracts/ComptrollerInterface.sol

pragma solidity ^0.5.16;

contract ComptrollerInterface {
    /// @notice Indicator that this is a Comptroller contract (for inspection)
    bool public constant isComptroller = true;

    /*** Assets You Are In ***/

    function enterMarkets(address[] calldata sTokens) external returns (uint[] memory);
    function exitMarket(address sToken) external returns (uint);

    /*** Policy Hooks ***/

    function mintAllowed(address sToken, address minter, uint mintAmount) external returns (uint);
    function mintVerify(address sToken, address minter, uint mintAmount, uint mintTokens) external;

    function redeemAllowed(address sToken, address redeemer, uint redeemTokens) external returns (uint);
    function redeemVerify(address sToken, address redeemer, uint redeemAmount, uint redeemTokens) external;

    function borrowAllowed(address sToken, address borrower, uint borrowAmount) external returns (uint);
    function borrowVerify(address sToken, address borrower, uint borrowAmount) external;

    function repayBorrowAllowed(
        address sToken,
        address payer,
        address borrower,
        uint repayAmount) external returns (uint);
    function repayBorrowVerify(
        address sToken,
        address payer,
        address borrower,
        uint repayAmount,
        uint borrowerIndex) external;

    function liquidateBorrowAllowed(
        address sTokenBorrowed,
        address sTokenCollateral,
        address liquidator,
        address borrower,
        uint repayAmount) external returns (uint);
    function liquidateBorrowVerify(
        address sTokenBorrowed,
        address sTokenCollateral,
        address liquidator,
        address borrower,
        uint repayAmount,
        uint seizeTokens) external;

    function seizeAllowed(
        address sTokenCollateral,
        address sTokenBorrowed,
        address liquidator,
        address borrower,
        uint seizeTokens) external returns (uint);
    function seizeVerify(
        address sTokenCollateral,
        address sTokenBorrowed,
        address liquidator,
        address borrower,
        uint seizeTokens) external;

    function transferAllowed(address sToken, address src, address dst, uint transferTokens) external returns (uint);
    function transferVerify(address sToken, address src, address dst, uint transferTokens) external;

    /*** Liquidity/Liquidation Calculations ***/

    function liquidateCalculateSeizeTokens(
        address sTokenBorrowed,
        address sTokenCollateral,
        uint repayAmount) external view returns (uint, uint);
}

interface IComptroller {
    /*** Reserve Info ***/
    function reserveGuardian() external view returns (address payable);
    function reserveAddress() external view returns (address payable);
}

// File: contracts/InterestRateModel.sol

pragma solidity ^0.5.16;

/**
  * @title Strike's InterestRateModel Interface
  * @author Strike
  */
contract InterestRateModel {
    /// @notice Indicator that this is an InterestRateModel contract (for inspection)
    bool public constant isInterestRateModel = true;

    /**
      * @notice Calculates the current borrow interest rate per block
      * @param cash The total amount of cash the market has
      * @param borrows The total amount of borrows the market has outstanding
      * @param reserves The total amount of reserves the market has
      * @return The borrow rate per block (as a percentage, and scaled by 1e18)
      */
    function getBorrowRate(uint cash, uint borrows, uint reserves) external view returns (uint);

    /**
      * @notice Calculates the current supply interest rate per block
      * @param cash The total amount of cash the market has
      * @param borrows The total amount of borrows the market has outstanding
      * @param reserves The total amount of reserves the market has
      * @param reserveFactorMantissa The current reserve factor the market has
      * @return The supply rate per block (as a percentage, and scaled by 1e18)
      */
    function getSupplyRate(uint cash, uint borrows, uint reserves, uint reserveFactorMantissa) external view returns (uint);

}

// File: contracts/STokenInterfaces.sol

pragma solidity ^0.5.16;


contract STokenStorage {
    /**
     * @dev Guard variable for re-entrancy checks
     */
    bool internal _notEntered;

    /**
     * @notice EIP-20 token name for this token
     */
    string public name;

    /**
     * @notice EIP-20 token symbol for this token
     */
    string public symbol;

    /**
     * @notice EIP-20 token decimals for this token
     */
    uint8 public decimals;

    /**
     * @notice Maximum borrow rate that can ever be applied (.0005% / block)
     */

    uint internal constant borrowRateMaxMantissa = 0.0005e16;

    /**
     * @notice Maximum fraction of interest that can be set aside for reserves
     */
    uint internal constant reserveFactorMaxMantissa = 1e18;

    /**
     * @notice Administrator for this contract
     */
    address payable public admin;

    /**
     * @notice Pending administrator for this contract
     */
    address payable public pendingAdmin;

    /**
     * @notice Contract which oversees inter-sToken operations
     */
    ComptrollerInterface public comptroller;

    /**
     * @notice Model which tells what the current interest rate should be
     */
    InterestRateModel public interestRateModel;

    /**
     * @notice Initial exchange rate used when minting the first STokens (used when totalSupply = 0)
     */
    uint internal initialExchangeRateMantissa;

    /**
     * @notice Fraction of interest currently set aside for reserves
     */
    uint public reserveFactorMantissa;

    /**
     * @notice Block number that interest was last accrued at
     */
    uint public accrualBlockNumber;

    /**
     * @notice Accumulator of the total earned interest rate since the opening of the market
     */
    uint public borrowIndex;

    /**
     * @notice Total amount of outstanding borrows of the underlying in this market
     */
    uint public totalBorrows;

    /**
     * @notice Total amount of reserves of the underlying held in this market
     */
    uint public totalReserves;

    /**
     * @notice Total number of tokens in circulation
     */
    uint public totalSupply;

    /**
     * @notice Official record of token balances for each account
     */
    mapping (address => uint) internal accountTokens;

    /**
     * @notice Approved token transfer amounts on behalf of others
     */
    mapping (address => mapping (address => uint)) internal transferAllowances;

    /**
     * @notice Container for borrow balance information
     * @member principal Total balance (with accrued interest), after applying the most recent balance-changing action
     * @member interestIndex Global borrowIndex as of the most recent balance-changing action
     */
    struct BorrowSnapshot {
        uint principal;
        uint interestIndex;
    }

    /**
     * @notice Mapping of account addresses to outstanding borrow balances
     */
    mapping(address => BorrowSnapshot) internal accountBorrows;

    /**
     * @notice Share of seized collateral that is added to reserves
     */
    uint public constant protocolSeizeShareMantissa = 5e16; //5%

}

contract STokenInterface is STokenStorage {
    /**
     * @notice Indicator that this is a SToken contract (for inspection)
     */
    bool public constant isSToken = true;


    /*** Market Events ***/

    /**
     * @notice Event emitted when interest is accrued
     */
    event AccrueInterest(uint cashPrior, uint interestAccumulated, uint borrowIndex, uint totalBorrows);

    /**
     * @notice Event emitted when tokens are minted
     */
    event Mint(address minter, uint mintAmount, uint mintTokens);

    /**
     * @notice Event emitted when tokens are redeemed
     */
    event Redeem(address redeemer, uint redeemAmount, uint redeemTokens);

    /**
     * @notice Event emitted when underlying is borrowed
     */
    event Borrow(address borrower, uint borrowAmount, uint accountBorrows, uint totalBorrows);

    /**
     * @notice Event emitted when a borrow is repaid
     */
    event RepayBorrow(address payer, address borrower, uint repayAmount, uint accountBorrows, uint totalBorrows);

    /**
     * @notice Event emitted when a borrow is liquidated
     */
    event LiquidateBorrow(address liquidator, address borrower, uint repayAmount, address sTokenCollateral, uint seizeTokens);


    /*** Admin Events ***/

    /**
     * @notice Event emitted when pendingAdmin is changed
     */
    event NewPendingAdmin(address oldPendingAdmin, address newPendingAdmin);

    /**
     * @notice Event emitted when pendingAdmin is accepted, which means admin is updated
     */
    event NewAdmin(address oldAdmin, address newAdmin);

    /**
     * @notice Event emitted when comptroller is changed
     */
    event NewComptroller(ComptrollerInterface oldComptroller, ComptrollerInterface newComptroller);

    /**
     * @notice Event emitted when interestRateModel is changed
     */
    event NewMarketInterestRateModel(InterestRateModel oldInterestRateModel, InterestRateModel newInterestRateModel);

    /**
     * @notice Event emitted when the reserve factor is changed
     */
    event NewReserveFactor(uint oldReserveFactorMantissa, uint newReserveFactorMantissa);

    /**
     * @notice Event emitted when the reserves are added
     */
    event ReservesAdded(address benefactor, uint addAmount, uint newTotalReserves);

    /**
     * @notice Event emitted when the reserves are reduced
     */
    event ReservesReduced(address admin, uint reduceAmount, uint newTotalReserves);

    /**
     * @notice Event emitted when the reserves are transfered
     */
    event TransferReserves(address guardian, address reserveAddress, uint reduceAmount, uint newTotalReserves);

    /**
     * @notice EIP20 Transfer event
     */
    event Transfer(address indexed from, address indexed to, uint amount);

    /**
     * @notice EIP20 Approval event
     */
    event Approval(address indexed owner, address indexed spender, uint amount);

    /**
     * @notice Failure event
     */
    event Failure(uint error, uint info, uint detail);


    /*** User Interface ***/

    function transfer(address dst, uint amount) external returns (bool);
    function transferFrom(address src, address dst, uint amount) external returns (bool);
    function approve(address spender, uint amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function balanceOfUnderlying(address owner) external returns (uint);
    function getAccountSnapshot(address account) external view returns (uint, uint, uint, uint);
    function borrowRatePerBlock() external view returns (uint);
    function supplyRatePerBlock() external view returns (uint);
    function totalBorrowsCurrent() external returns (uint);
    function borrowBalanceCurrent(address account) external returns (uint);
    function borrowBalanceStored(address account) public view returns (uint);
    function exchangeRateCurrent() public returns (uint);
    function exchangeRateStored() public view returns (uint);
    function getCash() external view returns (uint);
    function accrueInterest() public returns (uint);
    function seize(address liquidator, address borrower, uint seizeTokens) external returns (uint);


    /*** Admin Functions ***/

    function _setPendingAdmin(address payable newPendingAdmin) external returns (uint);
    function _acceptAdmin() external returns (uint);
    function _setComptroller(ComptrollerInterface newComptroller) public returns (uint);
    function _setReserveFactor(uint newReserveFactorMantissa) external returns (uint);
    function _reduceReserves(uint reduceAmount) external returns (uint);
    function _setInterestRateModel(InterestRateModel newInterestRateModel) public returns (uint);
}

contract SErc20Storage {
    /**
     * @notice Underlying asset for this SToken
     */
    address public underlying;
}

contract SErc20Interface is SErc20Storage {

    /*** User Interface ***/

    function mint(uint mintAmount) external returns (uint);
    function redeem(uint redeemTokens) external returns (uint);
    function redeemUnderlying(uint redeemAmount) external returns (uint);
    function borrow(uint borrowAmount) external returns (uint);
    function repayBorrow(uint repayAmount) external returns (uint);
    function repayBorrowBehalf(address borrower, uint repayAmount) external returns (uint);
    function liquidateBorrow(address borrower, uint repayAmount, STokenInterface sTokenCollateral) external returns (uint);


    /*** Admin Functions ***/

    function _addReserves(uint addAmount) external returns (uint);
}

contract SDelegationStorage {
    /**
     * @notice Implementation address for this contract
     */
    address public implementation;
}

contract SDelegatorInterface is SDelegationStorage {
    /**
     * @notice Emitted when implementation is changed
     */
    event NewImplementation(address oldImplementation, address newImplementation);

    /**
     * @notice Called by the admin to update the implementation of the delegator
     * @param implementation_ The address of the new implementation for delegation
     * @param allowResign Flag to indicate whether to call _resignImplementation on the old implementation
     * @param becomeImplementationData The encoded bytes data to be passed to _becomeImplementation
     */
    function _setImplementation(address implementation_, bool allowResign, bytes memory becomeImplementationData) public;
}

contract SDelegateInterface is SDelegationStorage {
    /**
     * @notice Called by the delegator on a delegate to initialize it for duty
     * @dev Should revert if any issues arise which make it unfit for delegation
     * @param data The encoded bytes data for any initialization
     */
    function _becomeImplementation(bytes memory data) public;

    /**
     * @notice Called by the delegator on a delegate to forfeit its responsibility
     */
    function _resignImplementation() public;
}

// File: contracts/SErc20Delegator.sol

pragma solidity ^0.5.16;

/**
 * @title Strike's SErc20Delegator Contract
 * @notice STokens which wrap an EIP-20 underlying and delegate to an implementation
 * @author Strike
 */
contract SErc20Delegator is STokenInterface, SErc20Interface, SDelegatorInterface {
    /**
     * @notice Construct a new money market
     * @param underlying_ The address of the underlying asset
     * @param comptroller_ The address of the Comptroller
     * @param interestRateModel_ The address of the interest rate model
     * @param initialExchangeRateMantissa_ The initial exchange rate, scaled by 1e18
     * @param name_ ERC-20 name of this token
     * @param symbol_ ERC-20 symbol of this token
     * @param decimals_ ERC-20 decimal precision of this token
     * @param admin_ Address of the administrator of this token
     * @param implementation_ The address of the implementation the contract delegates to
     * @param becomeImplementationData The encoded args for becomeImplementation
     */
    constructor(address underlying_,
                ComptrollerInterface comptroller_,
                InterestRateModel interestRateModel_,
                uint initialExchangeRateMantissa_,
                string memory name_,
                string memory symbol_,
                uint8 decimals_,
                address payable admin_,
                address implementation_,
                bytes memory becomeImplementationData) public {
        // Creator of the contract is admin during initialization
        admin = msg.sender;

        // First delegate gets to initialize the delegator (i.e. storage contract)
        delegateTo(implementation_, abi.encodeWithSignature("initialize(address,address,address,uint256,string,string,uint8)",
                                                            underlying_,
                                                            comptroller_,
                                                            interestRateModel_,
                                                            initialExchangeRateMantissa_,
                                                            name_,
                                                            symbol_,
                                                            decimals_));

        // New implementations always get set via the settor (post-initialize)
        _setImplementation(implementation_, false, becomeImplementationData);

        // Set the proper admin now that initialization is done
        admin = admin_;
    }

    /**
     * @notice Called by the admin to update the implementation of the delegator
     * @param implementation_ The address of the new implementation for delegation
     * @param allowResign Flag to indicate whether to call _resignImplementation on the old implementation
     * @param becomeImplementationData The encoded bytes data to be passed to _becomeImplementation
     */
    function _setImplementation(address implementation_, bool allowResign, bytes memory becomeImplementationData) public {
        require(msg.sender == admin, "SErc20Delegator::_setImplementation: Caller must be admin");

        if (allowResign) {
            delegateToImplementation(abi.encodeWithSignature("_resignImplementation()"));
        }

        address oldImplementation = implementation;
        implementation = implementation_;

        delegateToImplementation(abi.encodeWithSignature("_becomeImplementation(bytes)", becomeImplementationData));

        emit NewImplementation(oldImplementation, implementation);
    }

    /**
     * @notice Sender supplies assets into the market and receives sTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param mintAmount The amount of the underlying asset to supply
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function mint(uint mintAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("mint(uint256)", mintAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Sender redeems sTokens in exchange for the underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted`
     * @param redeemTokens The number of sTokens to redeem into underlying
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeem(uint redeemTokens) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("redeem(uint256)", redeemTokens));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Sender redeems sTokens in exchange for a specified amount of underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param redeemAmount The amount of underlying to redeem
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemUnderlying(uint redeemAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("redeemUnderlying(uint256)", redeemAmount));
        return abi.decode(data, (uint));
    }

    /**
      * @notice Sender borrows assets from the protocol to their own address
      * @param borrowAmount The amount of the underlying asset to borrow
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function borrow(uint borrowAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("borrow(uint256)", borrowAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Sender repays their own borrow
     * @param repayAmount The amount to repay
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function repayBorrow(uint repayAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("repayBorrow(uint256)", repayAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Sender repays a borrow belonging to borrower
     * @param borrower the account with the debt being payed off
     * @param repayAmount The amount to repay
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function repayBorrowBehalf(address borrower, uint repayAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("repayBorrowBehalf(address,uint256)", borrower, repayAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice The sender liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this sToken to be liquidated
     * @param sTokenCollateral The market in which to seize collateral from the borrower
     * @param repayAmount The amount of the underlying borrowed asset to repay
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function liquidateBorrow(address borrower, uint repayAmount, STokenInterface sTokenCollateral) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("liquidateBorrow(address,uint256,address)", borrower, repayAmount, sTokenCollateral));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transfer(address dst, uint amount) external returns (bool) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("transfer(address,uint256)", dst, amount));
        return abi.decode(data, (bool));
    }

    /**
     * @notice Transfer `amount` tokens from `src` to `dst`
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferFrom(address src, address dst, uint256 amount) external returns (bool) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("transferFrom(address,address,uint256)", src, dst, amount));
        return abi.decode(data, (bool));
    }

    /**
     * @notice Approve `spender` to transfer up to `amount` from `src`
     * @dev This will overwrite the approval amount for `spender`
     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
     * @param spender The address of the account which may transfer tokens
     * @param amount The number of tokens that are approved (-1 means infinite)
     * @return Whether or not the approval succeeded
     */
    function approve(address spender, uint256 amount) external returns (bool) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("approve(address,uint256)", spender, amount));
        return abi.decode(data, (bool));
    }

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param owner The address of the account which owns the tokens to be spent
     * @param spender The address of the account which may transfer tokens
     * @return The number of tokens allowed to be spent (-1 means infinite)
     */
    function allowance(address owner, address spender) external view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("allowance(address,address)", owner, spender));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Get the token balance of the `owner`
     * @param owner The address of the account to query
     * @return The number of tokens owned by `owner`
     */
    function balanceOf(address owner) external view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("balanceOf(address)", owner));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Get the underlying balance of the `owner`
     * @dev This also accrues interest in a transaction
     * @param owner The address of the account to query
     * @return The amount of underlying owned by `owner`
     */
    function balanceOfUnderlying(address owner) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("balanceOfUnderlying(address)", owner));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Get a snapshot of the account's balances, and the cached exchange rate
     * @dev This is used by comptroller to more efficiently perform liquidity checks.
     * @param account Address of the account to snapshot
     * @return (possible error, token balance, borrow balance, exchange rate mantissa)
     */
    function getAccountSnapshot(address account) external view returns (uint, uint, uint, uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("getAccountSnapshot(address)", account));
        return abi.decode(data, (uint, uint, uint, uint));
    }

    /**
     * @notice Returns the current per-block borrow interest rate for this sToken
     * @return The borrow interest rate per block, scaled by 1e18
     */
    function borrowRatePerBlock() external view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("borrowRatePerBlock()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Returns the current per-block supply interest rate for this sToken
     * @return The supply interest rate per block, scaled by 1e18
     */
    function supplyRatePerBlock() external view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("supplyRatePerBlock()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Returns the current total borrows plus accrued interest
     * @return The total borrows with interest
     */
    function totalBorrowsCurrent() external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("totalBorrowsCurrent()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Accrue interest to updated borrowIndex and then calculate account's borrow balance using the updated borrowIndex
     * @param account The address whose balance should be calculated after updating borrowIndex
     * @return The calculated balance
     */
    function borrowBalanceCurrent(address account) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("borrowBalanceCurrent(address)", account));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Return the borrow balance of account based on stored data
     * @param account The address whose balance should be calculated
     * @return The calculated balance
     */
    function borrowBalanceStored(address account) public view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("borrowBalanceStored(address)", account));
        return abi.decode(data, (uint));
    }

   /**
     * @notice Accrue interest then return the up-to-date exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateCurrent() public returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("exchangeRateCurrent()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Calculates the exchange rate from the underlying to the SToken
     * @dev This function does not accrue interest before calculating the exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateStored() public view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("exchangeRateStored()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Get cash balance of this sToken in the underlying asset
     * @return The quantity of underlying asset owned by this contract
     */
    function getCash() external view returns (uint) {
        bytes memory data = delegateToViewImplementation(abi.encodeWithSignature("getCash()"));
        return abi.decode(data, (uint));
    }

    /**
      * @notice Applies accrued interest to total borrows and reserves.
      * @dev This calculates interest accrued from the last checkpointed block
      *      up to the current block and writes new checkpoint to storage.
      */
    function accrueInterest() public returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("accrueInterest()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Transfers collateral tokens (this market) to the liquidator.
     * @dev Will fail unless called by another sToken during the process of liquidation.
     *  Its absolutely critical to use msg.sender as the borrowed sToken and not a parameter.
     * @param liquidator The account receiving seized collateral
     * @param borrower The account having collateral seized
     * @param seizeTokens The number of sTokens to seize
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function seize(address liquidator, address borrower, uint seizeTokens) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("seize(address,address,uint256)", liquidator, borrower, seizeTokens));
        return abi.decode(data, (uint));
    }

    /*** Admin Functions ***/

    /**
      * @notice Begins transfer of admin rights. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
      * @dev Admin function to begin change of admin. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
      * @param newPendingAdmin New pending admin.
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setPendingAdmin(address payable newPendingAdmin) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_setPendingAdmin(address)", newPendingAdmin));
        return abi.decode(data, (uint));
    }

    /**
      * @notice Sets a new comptroller for the market
      * @dev Admin function to set a new comptroller
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setComptroller(ComptrollerInterface newComptroller) public returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_setComptroller(address)", newComptroller));
        return abi.decode(data, (uint));
    }

    /**
      * @notice accrues interest and sets a new reserve factor for the protocol using _setReserveFactorFresh
      * @dev Admin function to accrue interest and set a new reserve factor
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setReserveFactor(uint newReserveFactorMantissa) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_setReserveFactor(uint256)", newReserveFactorMantissa));
        return abi.decode(data, (uint));
    }

    /**
      * @notice Accepts transfer of admin rights. msg.sender must be pendingAdmin
      * @dev Admin function for pending admin to accept role and update admin
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _acceptAdmin() external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_acceptAdmin()"));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Accrues interest and adds reserves by transferring from admin
     * @param addAmount Amount of reserves to add
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _addReserves(uint addAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_addReserves(uint256)", addAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Accrues interest and reduces reserves by transferring to admin
     * @param reduceAmount Amount of reduction to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _reduceReserves(uint reduceAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_reduceReserves(uint256)", reduceAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Accrues interest and reduces reserves by transferring to reserve address
     * @param reduceAmount Amount of reduction to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _transferReserves(uint reduceAmount) external returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_transferReserves(uint256)", reduceAmount));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Accrues interest and updates the interest rate model using _setInterestRateModelFresh
     * @dev Admin function to accrue interest and update the interest rate model
     * @param newInterestRateModel the new interest rate model to use
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setInterestRateModel(InterestRateModel newInterestRateModel) public returns (uint) {
        bytes memory data = delegateToImplementation(abi.encodeWithSignature("_setInterestRateModel(address)", newInterestRateModel));
        return abi.decode(data, (uint));
    }

    /**
     * @notice Internal method to delegate execution to another contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     * @param callee The contract to delegatecall
     * @param data The raw data to delegatecall
     * @return The returned bytes from the delegatecall
     */
    function delegateTo(address callee, bytes memory data) internal returns (bytes memory) {
        (bool success, bytes memory returnData) = callee.delegatecall(data);
        assembly {
            if eq(success, 0) {
                revert(add(returnData, 0x20), returndatasize)
            }
        }
        return returnData;
    }

    /**
     * @notice Delegates execution to the implementation contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     * @param data The raw data to delegatecall
     * @return The returned bytes from the delegatecall
     */
    function delegateToImplementation(bytes memory data) public returns (bytes memory) {
        return delegateTo(implementation, data);
    }

    /**
     * @notice Delegates execution to an implementation contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     *  There are an additional 2 prefix uints from the wrapper returndata, which we ignore since we make an extra hop.
     * @param data The raw data to delegatecall
     * @return The returned bytes from the delegatecall
     */
    function delegateToViewImplementation(bytes memory data) public view returns (bytes memory) {
        (bool success, bytes memory returnData) = address(this).staticcall(abi.encodeWithSignature("delegateToImplementation(bytes)", data));
        assembly {
            if eq(success, 0) {
                revert(add(returnData, 0x20), returndatasize)
            }
        }
        return abi.decode(returnData, (bytes));
    }

    /**
     * @notice Delegates execution to an implementation contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     */
    function () external payable {
        require(msg.value == 0,"SErc20Delegator:fallback: cannot send value to fallback");

        // delegate all other functions to current implementation
        (bool success, ) = implementation.delegatecall(msg.data);

        assembly {
            let free_mem_ptr := mload(0x40)
            returndatacopy(free_mem_ptr, 0, returndatasize)

            switch success
            case 0 { revert(free_mem_ptr, returndatasize) }
            default { return(free_mem_ptr, returndatasize) }
        }
    }
}