pragma solidity 0.5.17;


// SPDX-License-Identifier: MIT
/**
 * @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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        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-contracts/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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message 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, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// Storage for a YAM token
contract YAMTokenStorage {

    using SafeMath for uint256;

    /**
     * @dev Guard variable for re-entrancy checks. Not currently used
     */
    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 Governor for this contract
     */
    address public gov;

    /**
     * @notice Pending governance for this contract
     */
    address public pendingGov;

    /**
     * @notice Approved rebaser for this contract
     */
    address public rebaser;

    /**
     * @notice Reserve address of YAM protocol
     */
    address public incentivizer;

    /**
     * @notice Total supply of YAMs
     */
    uint256 public totalSupply;

    /**
     * @notice Internal decimals used to handle scaling factor
     */
    uint256 public constant internalDecimals = 10**24;

    /**
     * @notice Used for percentage maths
     */
    uint256 public constant BASE = 10**18;

    /**
     * @notice Scaling factor that adjusts everyone's balances
     */
    uint256 public yamsScalingFactor;

    mapping (address => uint256) internal _yamBalances;

    mapping (address => mapping (address => uint256)) internal _allowedFragments;

    uint256 public initSupply;

}

contract YAMGovernanceStorage {
    /// @notice A record of each accounts delegate
    mapping (address => address) internal _delegates;

    /// @notice A checkpoint for marking number of votes from a given block
    struct Checkpoint {
        uint32 fromBlock;
        uint256 votes;
    }

    /// @notice A record of votes checkpoints for each account, by index
    mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;

    /// @notice The number of checkpoints for each account
    mapping (address => uint32) public numCheckpoints;

    /// @notice The EIP-712 typehash for the contract's domain
    bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");

    /// @notice The EIP-712 typehash for the delegation struct used by the contract
    bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");

    /// @notice A record of states for signing / validating signatures
    mapping (address => uint) public nonces;
}

contract YAMTokenInterface is YAMTokenStorage, YAMGovernanceStorage {

    /// @notice An event thats emitted when an account changes its delegate
    event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);

    /// @notice An event thats emitted when a delegate account's vote balance changes
    event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);

    /**
     * @notice Event emitted when tokens are rebased
     */
    event Rebase(uint256 epoch, uint256 prevYamsScalingFactor, uint256 newYamsScalingFactor);

    /*** Gov Events ***/

    /**
     * @notice Event emitted when pendingGov is changed
     */
    event NewPendingGov(address oldPendingGov, address newPendingGov);

    /**
     * @notice Event emitted when gov is changed
     */
    event NewGov(address oldGov, address newGov);

    /**
     * @notice Sets the rebaser contract
     */
    event NewRebaser(address oldRebaser, address newRebaser);

    /**
     * @notice Sets the incentivizer contract
     */
    event NewIncentivizer(address oldIncentivizer, address newIncentivizer);

    /* - ERC20 Events - */

    /**
     * @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);

    /* - Extra Events - */
    /**
     * @notice Tokens minted event
     */
    event Mint(address to, uint256 amount);

    // Public functions
    function transfer(address to, uint256 value) external returns(bool);
    function transferFrom(address from, address to, uint256 value) external returns(bool);
    function balanceOf(address who) external view returns(uint256);
    function balanceOfUnderlying(address who) external view returns(uint256);
    function allowance(address owner_, address spender) external view returns(uint256);
    function approve(address spender, uint256 value) external returns (bool);
    function increaseAllowance(address spender, uint256 addedValue) external returns (bool);
    function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool);
    function maxScalingFactor() external view returns (uint256);

    /* - Governance Functions - */
    function getPriorVotes(address account, uint blockNumber) external view returns (uint256);
    function delegateBySig(address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s) external;
    function delegate(address delegatee) external;
    function delegates(address delegator) external view returns (address);
    function getCurrentVotes(address account) external view returns (uint256);

    /* - Permissioned/Governance functions - */
    function mint(address to, uint256 amount) external returns (bool);
    function rebase(uint256 epoch, uint256 indexDelta, bool positive) external returns (uint256);
    function _setRebaser(address rebaser_) external;
    function _setIncentivizer(address incentivizer_) external;
    function _setPendingGov(address pendingGov_) external;
    function _acceptGov() external;
}

contract YAMGovernanceToken is YAMTokenInterface {

      /// @notice An event thats emitted when an account changes its delegate
    event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);

    /// @notice An event thats emitted when a delegate account's vote balance changes
    event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);

    /**
     * @notice Delegate votes from `msg.sender` to `delegatee`
     * @param delegator The address to get delegatee for
     */
    function delegates(address delegator)
        external
        view
        returns (address)
    {
        return _delegates[delegator];
    }

   /**
    * @notice Delegate votes from `msg.sender` to `delegatee`
    * @param delegatee The address to delegate votes to
    */
    function delegate(address delegatee) external {
        return _delegate(msg.sender, delegatee);
    }

    /**
     * @notice Delegates votes from signatory to `delegatee`
     * @param delegatee The address to delegate votes to
     * @param nonce The contract state required to match the signature
     * @param expiry The time at which to expire the signature
     * @param v The recovery byte of the signature
     * @param r Half of the ECDSA signature pair
     * @param s Half of the ECDSA signature pair
     */
    function delegateBySig(
        address delegatee,
        uint nonce,
        uint expiry,
        uint8 v,
        bytes32 r,
        bytes32 s
    )
        external
    {
        bytes32 domainSeparator = keccak256(
            abi.encode(
                DOMAIN_TYPEHASH,
                keccak256(bytes(name)),
                getChainId(),
                address(this)
            )
        );

        bytes32 structHash = keccak256(
            abi.encode(
                DELEGATION_TYPEHASH,
                delegatee,
                nonce,
                expiry
            )
        );

        bytes32 digest = keccak256(
            abi.encodePacked(
                "\x19\x01",
                domainSeparator,
                structHash
            )
        );

        address signatory = ecrecover(digest, v, r, s);
        require(signatory != address(0), "YAM::delegateBySig: invalid signature");
        require(nonce == nonces[signatory]++, "YAM::delegateBySig: invalid nonce");
        require(now <= expiry, "YAM::delegateBySig: signature expired");
        return _delegate(signatory, delegatee);
    }

    /**
     * @notice Gets the current votes balance for `account`
     * @param account The address to get votes balance
     * @return The number of current votes for `account`
     */
    function getCurrentVotes(address account)
        external
        view
        returns (uint256)
    {
        uint32 nCheckpoints = numCheckpoints[account];
        return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
    }

    /**
     * @notice Determine the prior number of votes for an account as of a block number
     * @dev Block number must be a finalized block or else this function will revert to prevent misinformation.
     * @param account The address of the account to check
     * @param blockNumber The block number to get the vote balance at
     * @return The number of votes the account had as of the given block
     */
    function getPriorVotes(address account, uint blockNumber)
        external
        view
        returns (uint256)
    {
        require(blockNumber < block.number, "YAM::getPriorVotes: not yet determined");

        uint32 nCheckpoints = numCheckpoints[account];
        if (nCheckpoints == 0) {
            return 0;
        }

        // First check most recent balance
        if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
            return checkpoints[account][nCheckpoints - 1].votes;
        }

        // Next check implicit zero balance
        if (checkpoints[account][0].fromBlock > blockNumber) {
            return 0;
        }

        uint32 lower = 0;
        uint32 upper = nCheckpoints - 1;
        while (upper > lower) {
            uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
            Checkpoint memory cp = checkpoints[account][center];
            if (cp.fromBlock == blockNumber) {
                return cp.votes;
            } else if (cp.fromBlock < blockNumber) {
                lower = center;
            } else {
                upper = center - 1;
            }
        }
        return checkpoints[account][lower].votes;
    }

    function _delegate(address delegator, address delegatee)
        internal
    {
        address currentDelegate = _delegates[delegator];
        uint256 delegatorBalance = _yamBalances[delegator]; // balance of underlying YAMs (not scaled);
        _delegates[delegator] = delegatee;

        emit DelegateChanged(delegator, currentDelegate, delegatee);

        _moveDelegates(currentDelegate, delegatee, delegatorBalance);
    }

    function _moveDelegates(address srcRep, address dstRep, uint256 amount) internal {
        if (srcRep != dstRep && amount > 0) {
            if (srcRep != address(0)) {
                // decrease old representative
                uint32 srcRepNum = numCheckpoints[srcRep];
                uint256 srcRepOld = srcRepNum > 0 ? checkpoints[srcRep][srcRepNum - 1].votes : 0;
                uint256 srcRepNew = srcRepOld.sub(amount);
                _writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
            }

            if (dstRep != address(0)) {
                // increase new representative
                uint32 dstRepNum = numCheckpoints[dstRep];
                uint256 dstRepOld = dstRepNum > 0 ? checkpoints[dstRep][dstRepNum - 1].votes : 0;
                uint256 dstRepNew = dstRepOld.add(amount);
                _writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
            }
        }
    }

    function _writeCheckpoint(
        address delegatee,
        uint32 nCheckpoints,
        uint256 oldVotes,
        uint256 newVotes
    )
        internal
    {
        uint32 blockNumber = safe32(block.number, "YAM::_writeCheckpoint: block number exceeds 32 bits");

        if (nCheckpoints > 0 && checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber) {
            checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
        } else {
            checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes);
            numCheckpoints[delegatee] = nCheckpoints + 1;
        }

        emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
    }

    function safe32(uint n, string memory errorMessage) internal pure returns (uint32) {
        require(n < 2**32, errorMessage);
        return uint32(n);
    }

    function getChainId() internal pure returns (uint) {
        uint256 chainId;
        assembly { chainId := chainid() }
        return chainId;
    }
}

/* import "./YAMTokenInterface.sol"; */
contract YAMToken is YAMGovernanceToken {
    // Modifiers
    modifier onlyGov() {
        require(msg.sender == gov);
        _;
    }

    modifier onlyRebaser() {
        require(msg.sender == rebaser);
        _;
    }

    modifier onlyMinter() {
        require(msg.sender == rebaser || msg.sender == incentivizer || msg.sender == gov, "not minter");
        _;
    }

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

    function initialize(
        string memory name_,
        string memory symbol_,
        uint8 decimals_
    )
        public
    {
        require(yamsScalingFactor == 0, "already initialized");
        name = name_;
        symbol = symbol_;
        decimals = decimals_;
    }


    /**
    * @notice Computes the current max scaling factor
    */
    function maxScalingFactor()
        external
        view
        returns (uint256)
    {
        return _maxScalingFactor();
    }

    function _maxScalingFactor()
        internal
        view
        returns (uint256)
    {
        // scaling factor can only go up to 2**256-1 = initSupply * yamsScalingFactor
        // this is used to check if yamsScalingFactor will be too high to compute balances when rebasing.
        return uint256(-1) / initSupply;
    }

    /**
    * @notice Mints new tokens, increasing totalSupply, initSupply, and a users balance.
    * @dev Limited to onlyMinter modifier
    */
    function mint(address to, uint256 amount)
        external
        onlyMinter
        returns (bool)
    {
        _mint(to, amount);
        return true;
    }

    function _mint(address to, uint256 amount)
        internal
    {
      // increase totalSupply
      totalSupply = totalSupply.add(amount);

      // get underlying value
      uint256 yamValue = amount.mul(internalDecimals).div(yamsScalingFactor);

      // increase initSupply
      initSupply = initSupply.add(yamValue);

      // make sure the mint didnt push maxScalingFactor too low
      require(yamsScalingFactor <= _maxScalingFactor(), "max scaling factor too low");

      // add balance
      _yamBalances[to] = _yamBalances[to].add(yamValue);

      // add delegates to the minter
      _moveDelegates(address(0), _delegates[to], yamValue);
      emit Mint(to, amount);
    }

    /* - ERC20 functionality - */

    /**
    * @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)
        external
        validRecipient(to)
        returns (bool)
    {
        // underlying balance is stored in yams, so divide by current scaling factor

        // note, this means as scaling factor grows, dust will be untransferrable.
        // minimum transfer value == yamsScalingFactor / 1e24;

        // get amount in underlying
        uint256 yamValue = value.mul(internalDecimals).div(yamsScalingFactor);

        // sub from balance of sender
        _yamBalances[msg.sender] = _yamBalances[msg.sender].sub(yamValue);

        // add to balance of receiver
        _yamBalances[to] = _yamBalances[to].add(yamValue);
        emit Transfer(msg.sender, to, value);

        _moveDelegates(_delegates[msg.sender], _delegates[to], yamValue);
        return true;
    }

    /**
    * @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)
        external
        validRecipient(to)
        returns (bool)
    {
        // decrease allowance
        _allowedFragments[from][msg.sender] = _allowedFragments[from][msg.sender].sub(value);

        // get value in yams
        uint256 yamValue = value.mul(internalDecimals).div(yamsScalingFactor);

        // sub from from
        _yamBalances[from] = _yamBalances[from].sub(yamValue);
        _yamBalances[to] = _yamBalances[to].add(yamValue);
        emit Transfer(from, to, value);

        _moveDelegates(_delegates[from], _delegates[to], yamValue);
        return true;
    }

    /**
    * @param who The address to query.
    * @return The balance of the specified address.
    */
    function balanceOf(address who)
      external
      view
      returns (uint256)
    {
      return _yamBalances[who].mul(yamsScalingFactor).div(internalDecimals);
    }

    /** @notice Currently returns the internal storage amount
    * @param who The address to query.
    * @return The underlying balance of the specified address.
    */
    function balanceOfUnderlying(address who)
      external
      view
      returns (uint256)
    {
      return _yamBalances[who];
    }

    /**
     * @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)
        external
        view
        returns (uint256)
    {
        return _allowedFragments[owner_][spender];
    }

    /**
     * @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)
        external
        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)
        external
        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)
        external
        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;
    }

    /* - Governance Functions - */

    /** @notice sets the rebaser
     * @param rebaser_ The address of the rebaser contract to use for authentication.
     */
    function _setRebaser(address rebaser_)
        external
        onlyGov
    {
        address oldRebaser = rebaser;
        rebaser = rebaser_;
        emit NewRebaser(oldRebaser, rebaser_);
    }

    /** @notice sets the incentivizer
     * @param incentivizer_ The address of the rebaser contract to use for authentication.
     */
    function _setIncentivizer(address incentivizer_)
        external
        onlyGov
    {
        address oldIncentivizer = incentivizer;
        incentivizer = incentivizer_;
        emit NewIncentivizer(oldIncentivizer, incentivizer_);
    }

    /** @notice sets the pendingGov
     * @param pendingGov_ The address of the rebaser contract to use for authentication.
     */
    function _setPendingGov(address pendingGov_)
        external
        onlyGov
    {
        address oldPendingGov = pendingGov;
        pendingGov = pendingGov_;
        emit NewPendingGov(oldPendingGov, pendingGov_);
    }

    /** @notice lets msg.sender accept governance
     *
     */
    function _acceptGov()
        external
    {
        require(msg.sender == pendingGov, "!pending");
        address oldGov = gov;
        gov = pendingGov;
        pendingGov = address(0);
        emit NewGov(oldGov, gov);
    }

    /* - Extras - */

    /**
    * @notice Initiates a new rebase operation, provided the minimum time period has elapsed.
    *
    * @dev The supply adjustment equals (totalSupply * DeviationFromTargetRate) / rebaseLag
    *      Where DeviationFromTargetRate is (MarketOracleRate - targetRate) / targetRate
    *      and targetRate is CpiOracleRate / baseCpi
    */
    function rebase(
        uint256 epoch,
        uint256 indexDelta,
        bool positive
    )
        external
        onlyRebaser
        returns (uint256)
    {
        if (indexDelta == 0) {
          emit Rebase(epoch, yamsScalingFactor, yamsScalingFactor);
          return totalSupply;
        }

        uint256 prevYamsScalingFactor = yamsScalingFactor;

        if (!positive) {
           yamsScalingFactor = yamsScalingFactor.mul(BASE.sub(indexDelta)).div(BASE);
        } else {
            uint256 newScalingFactor = yamsScalingFactor.mul(BASE.add(indexDelta)).div(BASE);
            if (newScalingFactor < _maxScalingFactor()) {
                yamsScalingFactor = newScalingFactor;
            } else {
              yamsScalingFactor = _maxScalingFactor();
            }
        }

        totalSupply = initSupply.mul(yamsScalingFactor).div(BASE);
        emit Rebase(epoch, prevYamsScalingFactor, yamsScalingFactor);
        return totalSupply;
    }
}

contract YAM is YAMToken {
    /**
     * @notice Initialize the new money market
     * @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
     */
    function initialize(
        string memory name_,
        string memory symbol_,
        uint8 decimals_,
        address initial_owner,
        uint256 initSupply_
    )
        public
    {
        require(initSupply_ > 0, "0 init supply");

        super.initialize(name_, symbol_, decimals_);

        initSupply = initSupply_.mul(10**24/ (BASE));
        totalSupply = initSupply_;
        yamsScalingFactor = BASE;
        _yamBalances[initial_owner] = initSupply_.mul(10**24 / (BASE));

        // owner renounces ownership after deployment as they need to set
        // rebaser and incentivizer
        // gov = gov_;
    }
}

contract YAMDelegationStorage {
    /**
     * @notice Implementation address for this contract
     */
    address public implementation;
}

contract YAMDelegatorInterface is YAMDelegationStorage {
    /**
     * @notice Emitted when implementation is changed
     */
    event NewImplementation(address oldImplementation, address newImplementation);

    /**
     * @notice Called by the gov 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 YAMDelegateInterface is YAMDelegationStorage {
    /**
     * @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;
}

contract YAMDelegate is YAM, YAMDelegateInterface {
    /**
     * @notice Construct an empty delegate
     */
    constructor() public {}

    /**
     * @notice Called by the delegator on a delegate to initialize it for duty
     * @param data The encoded bytes data for any initialization
     */
    function _becomeImplementation(bytes memory data) public {
        // Shh -- currently unused
        data;

        // Shh -- we don't ever want this hook to be marked pure
        if (false) {
            implementation = address(0);
        }

        require(msg.sender == gov, "only the gov may call _becomeImplementation");
    }

    /**
     * @notice Called by the delegator on a delegate to forfeit its responsibility
     */
    function _resignImplementation() public {
        // Shh -- we don't ever want this hook to be marked pure
        if (false) {
            implementation = address(0);
        }

        require(msg.sender == gov, "only the gov may call _resignImplementation");
    }
}

contract YAMDelegator is YAMTokenInterface, YAMDelegatorInterface {
    /**
     * @notice Construct a new YAM
     * @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 initSupply_ Initial token amount
     * @param implementation_ The address of the implementation the contract delegates to
     * @param becomeImplementationData The encoded args for becomeImplementation
     */
    constructor(
        string memory name_,
        string memory symbol_,
        uint8 decimals_,
        uint256 initSupply_,
        address implementation_,
        bytes memory becomeImplementationData
    )
        public
    {


        // Creator of the contract is gov during initialization
        gov = msg.sender;

        // First delegate gets to initialize the delegator (i.e. storage contract)
        delegateTo(
            implementation_,
            abi.encodeWithSignature(
                "initialize(string,string,uint8,address,uint256)",
                name_,
                symbol_,
                decimals_,
                msg.sender,
                initSupply_
            )
        );

        // New implementations always get set via the settor (post-initialize)
        _setImplementation(implementation_, false, becomeImplementationData);

    }

    /**
     * @notice Called by the gov 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 == gov, "YAMDelegator::_setImplementation: Caller must be gov");

        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 cTokens 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(address to, uint256 mintAmount)
        external
        returns (bool)
    {
        to; mintAmount; // Shh
        delegateAndReturn();
    }

    /**
     * @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, uint256 amount)
        external
        returns (bool)
    {
        dst; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @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)
    {
        src; dst; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @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)
    {
        spender; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @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
    )
        external
        returns (bool)
    {
        spender; addedValue; // Shh
        delegateAndReturn();
    }

    function maxScalingFactor()
        external
        view
        returns (uint256)
    {
        delegateToViewAndReturn();
    }

    function rebase(
        uint256 epoch,
        uint256 indexDelta,
        bool positive
    )
        external
        returns (uint256)
    {
        epoch; indexDelta; positive;
        delegateAndReturn();
    }

    /**
     * @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
    )
        external
        returns (bool)
    {
        spender; subtractedValue; // Shh
        delegateAndReturn();
    }

    /**
     * @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 (uint256)
    {
        owner; spender; // Shh
        delegateToViewAndReturn();
    }

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param delegator The address of the account which has designated a delegate
     * @return Address of delegatee
     */
    function delegates(
        address delegator
    )
        external
        view
        returns (address)
    {
        delegator; // Shh
        delegateToViewAndReturn();
    }

    /**
     * @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 (uint256)
    {
        owner; // Shh
        delegateToViewAndReturn();
    }

    /**
     * @notice Currently unused. For future compatability
     * @param owner The address of the account to query
     * @return The number of underlying tokens owned by `owner`
     */
    function balanceOfUnderlying(address owner)
        external
        view
        returns (uint256)
    {
        owner; // Shh
        delegateToViewAndReturn();
    }

    /*** Gov Functions ***/

    /**
      * @notice Begins transfer of gov rights. The newPendingGov must call `_acceptGov` to finalize the transfer.
      * @dev Gov function to begin change of gov. The newPendingGov must call `_acceptGov` to finalize the transfer.
      * @param newPendingGov New pending gov.
      */
    function _setPendingGov(address newPendingGov)
        external
    {
        newPendingGov; // Shh
        delegateAndReturn();
    }

    function _setRebaser(address rebaser_)
        external
    {
        rebaser_; // Shh
        delegateAndReturn();
    }

    function _setIncentivizer(address incentivizer_)
        external
    {
        incentivizer_; // Shh
        delegateAndReturn();
    }

    /**
      * @notice Accepts transfer of gov rights. msg.sender must be pendingGov
      * @dev Gov function for pending gov to accept role and update gov
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _acceptGov()
        external
    {
        delegateAndReturn();
    }


    function getPriorVotes(address account, uint blockNumber)
        external
        view
        returns (uint256)
    {
        account; blockNumber;
        delegateToViewAndReturn();
    }

    function delegateBySig(
        address delegatee,
        uint nonce,
        uint expiry,
        uint8 v,
        bytes32 r,
        bytes32 s
    )
        external
    {
        delegatee; nonce; expiry; v; r; s;
        delegateAndReturn();
    }

    function delegate(address delegatee)
        external
    {
        delegatee;
        delegateAndReturn();
    }

    function getCurrentVotes(address account)
        external
        view
        returns (uint256)
    {
        account;
        delegateToViewAndReturn();
    }

    /**
     * @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));
    }

    function delegateToViewAndReturn() private view returns (bytes memory) {
        (bool success, ) = address(this).staticcall(abi.encodeWithSignature("delegateToImplementation(bytes)", 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(add(free_mem_ptr, 0x40), returndatasize) }
        }
    }

    function delegateAndReturn() private returns (bytes memory) {
        (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) }
        }
    }

    /**
     * @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,"YAMDelegator:fallback: cannot send value to fallback");

        // delegate all other functions to current implementation
        delegateAndReturn();
    }
}