Contract Source Code:

// File contracts/libraries/SafeMath.sol

// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;


library SafeMath {

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

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

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }

    function sqrrt(uint256 a) internal pure returns (uint c) {
        if (a > 3) {
            c = a;
            uint b = add( div( a, 2), 1 );
            while (b < c) {
                c = b;
                b = div( add( div( a, b ), b), 2 );
            }
        } else if (a != 0) {
            c = 1;
        }
    }
}


// File contracts/libraries/Address.sol

pragma solidity 0.7.5;


library Address {

    function isContract(address account) internal view returns (bool) {

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }

    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            if (returndata.length > 0) {

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }

    function addressToString(address _address) internal pure returns(string memory) {
        bytes32 _bytes = bytes32(uint256(_address));
        bytes memory HEX = "0123456789abcdef";
        bytes memory _addr = new bytes(42);

        _addr[0] = '0';
        _addr[1] = 'x';

        for(uint256 i = 0; i < 20; i++) {
            _addr[2+i*2] = HEX[uint8(_bytes[i + 12] >> 4)];
            _addr[3+i*2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
        }

        return string(_addr);

    }
}


// File contracts/interfaces/IERC20.sol

pragma solidity 0.7.5;

interface IERC20 {
    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}


// File contracts/libraries/SafeERC20.sol

pragma solidity 0.7.5;


library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {

        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function _callOptionalReturn(IERC20 token, bytes memory data) private {

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}


// File contracts/libraries/FullMath.sol

pragma solidity 0.7.5;

library FullMath {
    function fullMul(uint256 x, uint256 y) private pure returns (uint256 l, uint256 h) {
        uint256 mm = mulmod(x, y, uint256(-1));
        l = x * y;
        h = mm - l;
        if (mm < l) h -= 1;
    }

    function fullDiv(
        uint256 l,
        uint256 h,
        uint256 d
    ) private pure returns (uint256) {
        uint256 pow2 = d & -d;
        d /= pow2;
        l /= pow2;
        l += h * ((-pow2) / pow2 + 1);
        uint256 r = 1;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        return l * r;
    }

    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 d
    ) internal pure returns (uint256) {
        (uint256 l, uint256 h) = fullMul(x, y);
        uint256 mm = mulmod(x, y, d);
        if (mm > l) h -= 1;
        l -= mm;
        require(h < d, 'FullMath::mulDiv: overflow');
        return fullDiv(l, h, d);
    }
}


// File contracts/libraries/FixedPoint.sol

pragma solidity 0.7.5;

library Babylonian {

    function sqrt(uint256 x) internal pure returns (uint256) {
        if (x == 0) return 0;

        uint256 xx = x;
        uint256 r = 1;
        if (xx >= 0x100000000000000000000000000000000) {
            xx >>= 128;
            r <<= 64;
        }
        if (xx >= 0x10000000000000000) {
            xx >>= 64;
            r <<= 32;
        }
        if (xx >= 0x100000000) {
            xx >>= 32;
            r <<= 16;
        }
        if (xx >= 0x10000) {
            xx >>= 16;
            r <<= 8;
        }
        if (xx >= 0x100) {
            xx >>= 8;
            r <<= 4;
        }
        if (xx >= 0x10) {
            xx >>= 4;
            r <<= 2;
        }
        if (xx >= 0x8) {
            r <<= 1;
        }
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1; // Seven iterations should be enough
        uint256 r1 = x / r;
        return (r < r1 ? r : r1);
    }
}

library BitMath {

    function mostSignificantBit(uint256 x) internal pure returns (uint8 r) {
        require(x > 0, 'BitMath::mostSignificantBit: zero');

        if (x >= 0x100000000000000000000000000000000) {
            x >>= 128;
            r += 128;
        }
        if (x >= 0x10000000000000000) {
            x >>= 64;
            r += 64;
        }
        if (x >= 0x100000000) {
            x >>= 32;
            r += 32;
        }
        if (x >= 0x10000) {
            x >>= 16;
            r += 16;
        }
        if (x >= 0x100) {
            x >>= 8;
            r += 8;
        }
        if (x >= 0x10) {
            x >>= 4;
            r += 4;
        }
        if (x >= 0x4) {
            x >>= 2;
            r += 2;
        }
        if (x >= 0x2) r += 1;
    }
}


library FixedPoint {

    struct uq112x112 {
        uint224 _x;
    }

    struct uq144x112 {
        uint256 _x;
    }

    uint8 private constant RESOLUTION = 112;
    uint256 private constant Q112 = 0x10000000000000000000000000000;
    uint256 private constant Q224 = 0x100000000000000000000000000000000000000000000000000000000;
    uint256 private constant LOWER_MASK = 0xffffffffffffffffffffffffffff; // decimal of UQ*x112 (lower 112 bits)

    function decode(uq112x112 memory self) internal pure returns (uint112) {
        return uint112(self._x >> RESOLUTION);
    }

    function decode112with18(uq112x112 memory self) internal pure returns (uint) {

        return uint(self._x) / 5192296858534827;
    }

    function fraction(uint256 numerator, uint256 denominator) internal pure returns (uq112x112 memory) {
        require(denominator > 0, 'FixedPoint::fraction: division by zero');
        if (numerator == 0) return FixedPoint.uq112x112(0);

        if (numerator <= uint144(-1)) {
            uint256 result = (numerator << RESOLUTION) / denominator;
            require(result <= uint224(-1), 'FixedPoint::fraction: overflow');
            return uq112x112(uint224(result));
        } else {
            uint256 result = FullMath.mulDiv(numerator, Q112, denominator);
            require(result <= uint224(-1), 'FixedPoint::fraction: overflow');
            return uq112x112(uint224(result));
        }
    }
    
    // square root of a UQ112x112
    // lossy between 0/1 and 40 bits
    function sqrt(uq112x112 memory self) internal pure returns (uq112x112 memory) {
        if (self._x <= uint144(-1)) {
            return uq112x112(uint224(Babylonian.sqrt(uint256(self._x) << 112)));
        }

        uint8 safeShiftBits = 255 - BitMath.mostSignificantBit(self._x);
        safeShiftBits -= safeShiftBits % 2;
        return uq112x112(uint224(Babylonian.sqrt(uint256(self._x) << safeShiftBits) << ((112 - safeShiftBits) / 2)));
    }
}


// File contracts/interfaces/ITreasury.sol

pragma solidity 0.7.5;

interface ITreasury {
    function deposit(address _principleTokenAddress, uint _amountPrincipleToken, uint _amountPayoutToken) external;
    function valueOfToken( address _principleTokenAddress, uint _amount ) external view returns ( uint value_ );
}


// File contracts/types/Ownable.sol

pragma solidity 0.7.5;

contract Ownable {

    address public policy;

    constructor () {
        policy = msg.sender;
    }

    modifier onlyPolicy() {
        require( policy == msg.sender, "Ownable: caller is not the owner" );
        _;
    }
    
    function transferManagment(address _newOwner) external onlyPolicy() {
        require( _newOwner != address(0) );
        policy = _newOwner;
    }
}


// File contracts/OlympusProCustomBond.sol

pragma solidity 0.7.5;




contract CustomBond is Ownable {
    using FixedPoint for *;
    using SafeERC20 for IERC20;
    using SafeMath for uint;
    
    /* ======== EVENTS ======== */

    event BondCreated( uint deposit, uint payout, uint expires );
    event BondRedeemed( address recipient, uint payout, uint remaining );
    event BondPriceChanged( uint internalPrice, uint debtRatio );
    event ControlVariableAdjustment( uint initialBCV, uint newBCV, uint adjustment, bool addition );
    
    
     /* ======== STATE VARIABLES ======== */
    
    IERC20 immutable payoutToken; // token paid for principal
    IERC20 immutable principalToken; // inflow token
    ITreasury immutable customTreasury; // pays for and receives principal
    address immutable olympusDAO;
    address olympusTreasury; // receives fee

    uint public totalPrincipalBonded;
    uint public totalPayoutGiven;
    
    Terms public terms; // stores terms for new bonds
    Adjust public adjustment; // stores adjustment to BCV data
    FeeTiers[] private feeTiers; // stores fee tiers

    mapping( address => Bond ) public bondInfo; // stores bond information for depositors

    uint public totalDebt; // total value of outstanding bonds; used for pricing
    uint public lastDecay; // reference block for debt decay

    address immutable subsidyRouter; // pays subsidy in OHM to custom treasury
    uint payoutSinceLastSubsidy; // principal accrued since subsidy paid
    
    /* ======== STRUCTS ======== */

    struct FeeTiers {
        uint tierCeilings; // principal bonded till next tier
        uint fees; // in ten-thousandths (i.e. 33300 = 3.33%)
    }

    // Info for creating new bonds
    struct Terms {
        uint controlVariable; // scaling variable for price
        uint vestingTerm; // in blocks
        uint minimumPrice; // vs principal value
        uint maxPayout; // in thousandths of a %. i.e. 500 = 0.5%
        uint maxDebt; // payout token decimal debt ratio, max % total supply created as debt
    }

    // Info for bond holder
    struct Bond {
        uint payout; // payout token remaining to be paid
        uint vesting; // Blocks left to vest
        uint lastBlock; // Last interaction
        uint truePricePaid; // Price paid (principal tokens per payout token) in ten-millionths - 4000000 = 0.4
    }

    // Info for incremental adjustments to control variable 
    struct Adjust {
        bool add; // addition or subtraction
        uint rate; // increment
        uint target; // BCV when adjustment finished
        uint buffer; // minimum length (in blocks) between adjustments
        uint lastBlock; // block when last adjustment made
    }
    
    /* ======== CONSTRUCTOR ======== */

    constructor(
        address _customTreasury, 
        address _payoutToken, 
        address _principalToken, 
        address _olympusTreasury,
        address _subsidyRouter, 
        address _initialOwner, 
        address _olympusDAO,
        uint[] memory _tierCeilings, 
        uint[] memory _fees
    ) {
        require( _customTreasury != address(0) );
        customTreasury = ITreasury( _customTreasury );
        require( _payoutToken != address(0) );
        payoutToken = IERC20( _payoutToken );
        require( _principalToken != address(0) );
        principalToken = IERC20( _principalToken );
        require( _olympusTreasury != address(0) );
        olympusTreasury = _olympusTreasury;
        require( _subsidyRouter != address(0) );
        subsidyRouter = _subsidyRouter;
        require( _initialOwner != address(0) );
        policy = _initialOwner;
        require( _olympusDAO != address(0) );
        olympusDAO = _olympusDAO;
        require(_tierCeilings.length == _fees.length, "tier length and fee length not the same");

        for(uint i; i < _tierCeilings.length; i++) {
            feeTiers.push( FeeTiers({
                tierCeilings: _tierCeilings[i],
                fees: _fees[i]
            }));
        }
    }

    /* ======== INITIALIZATION ======== */
    
    /**
     *  @notice initializes bond parameters
     *  @param _controlVariable uint
     *  @param _vestingTerm uint
     *  @param _minimumPrice uint
     *  @param _maxPayout uint
     *  @param _maxDebt uint
     *  @param _initialDebt uint
     */
    function initializeBond( 
        uint _controlVariable, 
        uint _vestingTerm,
        uint _minimumPrice,
        uint _maxPayout,
        uint _maxDebt,
        uint _initialDebt
    ) external onlyPolicy() {
        require( currentDebt() == 0, "Debt must be 0 for initialization" );
        terms = Terms ({
            controlVariable: _controlVariable,
            vestingTerm: _vestingTerm,
            minimumPrice: _minimumPrice,
            maxPayout: _maxPayout,
            maxDebt: _maxDebt
        });
        totalDebt = _initialDebt;
        lastDecay = block.number;
    }
    
    
    /* ======== POLICY FUNCTIONS ======== */

    enum PARAMETER { VESTING, PAYOUT, DEBT }
    /**
     *  @notice set parameters for new bonds
     *  @param _parameter PARAMETER
     *  @param _input uint
     */
    function setBondTerms ( PARAMETER _parameter, uint _input ) external onlyPolicy() {
        if ( _parameter == PARAMETER.VESTING ) { // 0
            require( _input >= 10000, "Vesting must be longer than 36 hours" );
            terms.vestingTerm = _input;
        } else if ( _parameter == PARAMETER.PAYOUT ) { // 1
            require( _input <= 1000, "Payout cannot be above 1 percent" );
            terms.maxPayout = _input;
        } else if ( _parameter == PARAMETER.DEBT ) { // 2
            terms.maxDebt = _input;
        }
    }

    /**
     *  @notice set control variable adjustment
     *  @param _addition bool
     *  @param _increment uint
     *  @param _target uint
     *  @param _buffer uint
     */
    function setAdjustment ( 
        bool _addition,
        uint _increment, 
        uint _target,
        uint _buffer 
    ) external onlyPolicy() {
        require( _increment <= terms.controlVariable.mul( 30 ).div( 1000 ), "Increment too large" );

        adjustment = Adjust({
            add: _addition,
            rate: _increment,
            target: _target,
            buffer: _buffer,
            lastBlock: block.number
        });
    }

    /**
     *  @notice change address of Olympus Treasury
     *  @param _olympusTreasury uint
     */
    function changeOlympusTreasury(address _olympusTreasury) external {
        require( msg.sender == olympusDAO, "Only Olympus DAO" );
        olympusTreasury = _olympusTreasury;
    }

    /**
     *  @notice subsidy controller checks payouts since last subsidy and resets counter
     *  @return payoutSinceLastSubsidy_ uint
     */
    function paySubsidy() external returns ( uint payoutSinceLastSubsidy_ ) {
        require( msg.sender == subsidyRouter, "Only subsidy controller" );

        payoutSinceLastSubsidy_ = payoutSinceLastSubsidy;
        payoutSinceLastSubsidy = 0;
    }
    
    /* ======== USER FUNCTIONS ======== */
    
    /**
     *  @notice deposit bond
     *  @param _amount uint
     *  @param _maxPrice uint
     *  @param _depositor address
     *  @return uint
     */
    function deposit(uint _amount, uint _maxPrice, address _depositor) external returns (uint) {
        require( _depositor != address(0), "Invalid address" );

        decayDebt();
        require( totalDebt <= terms.maxDebt, "Max capacity reached" );
        
        uint nativePrice = trueBondPrice();

        require( _maxPrice >= nativePrice, "Slippage limit: more than max price" ); // slippage protection

        uint value = customTreasury.valueOfToken( address(principalToken), _amount );
        uint payout = _payoutFor( value ); // payout to bonder is computed

        require( payout >= 10 ** payoutToken.decimals() / 100, "Bond too small" ); // must be > 0.01 payout token ( underflow protection )
        require( payout <= maxPayout(), "Bond too large"); // size protection because there is no slippage

        // profits are calculated
        uint fee = payout.mul( currentOlympusFee() ).div( 1e6 );

        /**
            principal is transferred in
            approved and
            deposited into the treasury, returning (_amount - profit) payout token
         */
        principalToken.safeTransferFrom( msg.sender, address(this), _amount );
        principalToken.approve( address(customTreasury), _amount );
        customTreasury.deposit( address(principalToken), _amount, payout );
        
        if ( fee != 0 ) { // fee is transferred to dao 
            payoutToken.transfer(olympusTreasury, fee);
        }
        
        // total debt is increased
        totalDebt = totalDebt.add( value );
                
        // depositor info is stored
        bondInfo[ _depositor ] = Bond({ 
            payout: bondInfo[ _depositor ].payout.add( payout.sub(fee) ),
            vesting: terms.vestingTerm,
            lastBlock: block.number,
            truePricePaid: trueBondPrice()
        });

        // indexed events are emitted
        emit BondCreated( _amount, payout, block.number.add( terms.vestingTerm ) );
        emit BondPriceChanged( _bondPrice(), debtRatio() );

        totalPrincipalBonded = totalPrincipalBonded.add(_amount); // total bonded increased
        totalPayoutGiven = totalPayoutGiven.add(payout); // total payout increased
        payoutSinceLastSubsidy = payoutSinceLastSubsidy.add( payout ); // subsidy counter increased

        adjust(); // control variable is adjusted
        return payout; 
    }
    
    /** 
     *  @notice redeem bond for user
     *  @return uint
     */ 
    function redeem(address _depositor) external returns (uint) {
        Bond memory info = bondInfo[ _depositor ];
        uint percentVested = percentVestedFor( _depositor ); // (blocks since last interaction / vesting term remaining)

        if ( percentVested >= 10000 ) { // if fully vested
            delete bondInfo[ _depositor ]; // delete user info
            emit BondRedeemed( _depositor, info.payout, 0 ); // emit bond data
            payoutToken.transfer( _depositor, info.payout );
            return info.payout;

        } else { // if unfinished
            // calculate payout vested
            uint payout = info.payout.mul( percentVested ).div( 10000 );

            // store updated deposit info
            bondInfo[ _depositor ] = Bond({
                payout: info.payout.sub( payout ),
                vesting: info.vesting.sub( block.number.sub( info.lastBlock ) ),
                lastBlock: block.number,
                truePricePaid: info.truePricePaid
            });

            emit BondRedeemed( _depositor, payout, bondInfo[ _depositor ].payout );
            payoutToken.transfer( _depositor, payout );
            return payout;
        }
        
    }
    
    /* ======== INTERNAL HELPER FUNCTIONS ======== */

    /**
     *  @notice makes incremental adjustment to control variable
     */
    function adjust() internal {
        uint blockCanAdjust = adjustment.lastBlock.add( adjustment.buffer );
        if( adjustment.rate != 0 && block.number >= blockCanAdjust ) {
            uint initial = terms.controlVariable;
            if ( adjustment.add ) {
                terms.controlVariable = terms.controlVariable.add( adjustment.rate );
                if ( terms.controlVariable >= adjustment.target ) {
                    adjustment.rate = 0;
                }
            } else {
                terms.controlVariable = terms.controlVariable.sub( adjustment.rate );
                if ( terms.controlVariable <= adjustment.target ) {
                    adjustment.rate = 0;
                }
            }
            adjustment.lastBlock = block.number;
            emit ControlVariableAdjustment( initial, terms.controlVariable, adjustment.rate, adjustment.add );
        }
    }

    /**
     *  @notice reduce total debt
     */
    function decayDebt() internal {
        totalDebt = totalDebt.sub( debtDecay() );
        lastDecay = block.number;
    }

    /**
     *  @notice calculate current bond price and remove floor if above
     *  @return price_ uint
     */
    function _bondPrice() internal returns ( uint price_ ) {
        price_ = terms.controlVariable.mul( debtRatio() ).div( 10 ** (uint256(payoutToken.decimals()).sub(5)) );
        if ( price_ < terms.minimumPrice ) {
            price_ = terms.minimumPrice;        
        } else if ( terms.minimumPrice != 0 ) {
            terms.minimumPrice = 0;
        }
    }


    /* ======== VIEW FUNCTIONS ======== */

    /**
     *  @notice calculate current bond premium
     *  @return price_ uint
     */
    function bondPrice() public view returns ( uint price_ ) {        
        price_ = terms.controlVariable.mul( debtRatio() ).div( 10 ** (uint256(payoutToken.decimals()).sub(5)) );
        if ( price_ < terms.minimumPrice ) {
            price_ = terms.minimumPrice;
        }
    }

    /**
     *  @notice calculate true bond price a user pays
     *  @return price_ uint
     */
    function trueBondPrice() public view returns ( uint price_ ) {
        price_ = bondPrice().add(bondPrice().mul( currentOlympusFee() ).div( 1e6 ) );
    }

    /**
     *  @notice determine maximum bond size
     *  @return uint
     */
    function maxPayout() public view returns ( uint ) {
        return payoutToken.totalSupply().mul( terms.maxPayout ).div( 100000 );
    }

    /**
     *  @notice calculate total interest due for new bond
     *  @param _value uint
     *  @return uint
     */
    function _payoutFor( uint _value ) internal view returns ( uint ) {
        return FixedPoint.fraction( _value, bondPrice() ).decode112with18().div( 1e11 );
    }

    /**
     *  @notice calculate user's interest due for new bond, accounting for Olympus Fee
     *  @param _value uint
     *  @return uint
     */
    function payoutFor( uint _value ) external view returns ( uint ) {
        uint total = FixedPoint.fraction( _value, bondPrice() ).decode112with18().div( 1e11 );
        return total.sub(total.mul( currentOlympusFee() ).div( 1e6 ));
    }

    /**
     *  @notice calculate current ratio of debt to payout token supply
     *  @notice protocols using Olympus Pro should be careful when quickly adding large %s to total supply
     *  @return debtRatio_ uint
     */
    function debtRatio() public view returns ( uint debtRatio_ ) {   
        debtRatio_ = FixedPoint.fraction( 
            currentDebt().mul( 10 ** payoutToken.decimals() ), 
            payoutToken.totalSupply()
        ).decode112with18().div( 1e18 );
    }

    /**
     *  @notice calculate debt factoring in decay
     *  @return uint
     */
    function currentDebt() public view returns ( uint ) {
        return totalDebt.sub( debtDecay() );
    }

    /**
     *  @notice amount to decay total debt by
     *  @return decay_ uint
     */
    function debtDecay() public view returns ( uint decay_ ) {
        uint blocksSinceLast = block.number.sub( lastDecay );
        decay_ = totalDebt.mul( blocksSinceLast ).div( terms.vestingTerm );
        if ( decay_ > totalDebt ) {
            decay_ = totalDebt;
        }
    }


    /**
     *  @notice calculate how far into vesting a depositor is
     *  @param _depositor address
     *  @return percentVested_ uint
     */
    function percentVestedFor( address _depositor ) public view returns ( uint percentVested_ ) {
        Bond memory bond = bondInfo[ _depositor ];
        uint blocksSinceLast = block.number.sub( bond.lastBlock );
        uint vesting = bond.vesting;

        if ( vesting > 0 ) {
            percentVested_ = blocksSinceLast.mul( 10000 ).div( vesting );
        } else {
            percentVested_ = 0;
        }
    }

    /**
     *  @notice calculate amount of payout token available for claim by depositor
     *  @param _depositor address
     *  @return pendingPayout_ uint
     */
    function pendingPayoutFor( address _depositor ) external view returns ( uint pendingPayout_ ) {
        uint percentVested = percentVestedFor( _depositor );
        uint payout = bondInfo[ _depositor ].payout;

        if ( percentVested >= 10000 ) {
            pendingPayout_ = payout;
        } else {
            pendingPayout_ = payout.mul( percentVested ).div( 10000 );
        }
    }

    /**
     *  @notice current fee Olympus takes of each bond
     *  @return currentFee_ uint
     */
    function currentOlympusFee() public view returns( uint currentFee_ ) {
        uint tierLength = feeTiers.length;
        for(uint i; i < tierLength; i++) {
            if(totalPrincipalBonded < feeTiers[i].tierCeilings || i == tierLength - 1 ) {
                return feeTiers[i].fees;
            }
        }
    }
    
}