Sequential Dutch Auctioneer (SDA)

The Base SDA contract is an implementation of the Auctioneer Interface that uses a Sequential Dutch Auction pricing system to buy a target amount of quote tokens or sell a target amount of base tokens over the duration of a market.

The contract is abstract since it leaves final implementation of the createMarket function to a contract that inherits it.

Data Structures (Structs)

MarketParams

Parameters to create a new SDA market. Encoded as bytes and provided as input to createMarket.

struct MarketParams {
    ERC20 payoutToken;
    ERC20 quoteToken;
    address callbackAddr;
    bool capacityInQuote;
    uint256 capacity;
    uint256 formattedInitialPrice;
    uint256 formattedMinimumPrice;
    uint32 debtBuffer;
    uint48 vesting;
    uint48 conclusion;
    uint32 depositInterval;
    int8 scaleAdjustment;
}

Field	Type	Description
payoutToken	ERC20 (address)	Payout Token (token paid out by market and provided by creator)
quoteToken	ERC20 (address)	Quote Token (token to be received by the market and provided by purchaser)
callbackAddr	address	Callback contract address, should conform to IBondCallback. If 0x00, tokens will be transferred from market owner. Using a callback requires whitelisting by the protocol
capacityInQuote	bool	Is Capacity in Quote Token?
capacity	uint256	Capacity (amount in quote token decimals or amount in payout token decimals). Set capacityInQuote flag appropriately
formattedInitialPrice	uint256	Initial price of the market as a ratio of quote tokens per payout token, see note below on formatting
formattedMinimumPrice	uint256	Minimum price of the market as a ratio of quote tokens per payout token, see note below on formatting
debtBuffer	uint32	Debt buffer. Percent with 3 decimals. Percentage over the initial debt to allow the market to accumulate at anyone time. Works as a circuit breaker for the market in case external conditions incentivize massive buying (e.g. stablecoin depeg). Minimum is the greater of 10% or initial max payout as a percentage of capacity
vesting	uint48	Is fixed term ? Vesting length (seconds) : Vesting expiry (timestamp). A 'vesting' param longer than 50 years is considered a timestamp for fixed expiry
conclusion	uint48	Timestamp that the market will conclude on. Must be at least 1 day (86400 seconds) after creation
depositInterval	uint32	Target deposit interval for purchases (in seconds). Determines the maxPayout of the market. Minimum is 1 hour (3600 seconds)
scaleAdjustment	int8	Market scaling adjustment factor, ranges from -24 to +24. See note below on how to calculate

Calculating Formatted Price and Scale Adjustment

In order to support a broad range of tokens, with different decimal configurations and prices, we calculate an optimal scaling factor for each market. Specifically, the scale adjustment allows the SDA to support tokens with 6 to 18 configured decimals and with prices that differ by up to 24 decimal places (if the tokens have the configured decimals, less if not). To implement this, the market creator must provide a scale adjustment factor and format the price correctly.

First, you need the price of each token in a common unit, e.g. dollars or ether.

Then, if $\Phi_p$ is the price of the payout token and $\Phi_q$ is the price of quote token in the common unit, it can expressed in base 10 (or scientific) notation as:

$$\Phi_p = \phi_p \times 10^{d_{\phi p}}$$

$$\Phi_q = \phi_q \times 10^{d_{\phi q}}$$

where:

• $\phi_p$ is the coefficient of the payout token price and ​$d_{\phi p}$​ is the number of price decimals for the payout token (aka the significand of the price).
• $\phi_q$​ is the coefficient of the quote token price and $d_{\phi q}$​ is the number of price decimals for the quote token.

Example: If the price of WETH is $1,500, then we would deconstruct it as $1.5 \times 10^3$​. Therefore $\phi = 1.5$ and $d_{\phi} = 3$.

Now, using the price values and the configured number of decimals for each token, we can calculate the scale adjustment.

$$s = d_p - d_q - \left\lfloor\frac{d_{\phi p} - d_{\phi q}}{2}\right\rfloor$$

where:

• $d_p$ is the configured payout token decimals (e.g. WETH has 18 configured decimals)
• $d_q$ is the configured quote token decimals.
• $d_{\phi p}$ and $d_{\phi q}$ are as defined above.

Example:

• Let WETH be the quote token and OHM be the payout token. WETH has 18 configured decimals and OHM has 9 configured decimals. Assume the market price of WETH is $1,500 -> $1.5 \times 10^3$and the market price of OHM is $10 -> $1 \times 10^1$.​
• Then, the scale adjustment is $s = 9 - 18 - \left\lfloor\frac{1-3}{2}\right\rfloor = -9 + 1 = -8$​

Once we have the scale adjustment, we can format the initial price using the variables defined above. We're starting the market at the current market price by using the token prices at the time of creation. This is optimal in most situations, but there may be circumstances where it makes sense to choose a different starting price (e.g. you want delayed activity or activity only if the price increases in the short-term).

$$\Phi_0 = \frac{\phi_p}{\phi_q} \times 10^{36 + s + d_q - d_p +d_{\phi p} - d_{\phi q}}$$

Example: Continuing with the WETH and OHM example from above, we format the initial price as:

$$\Phi_0 = \frac{1}{1.5} \times 10^{36+(-8)+18-9+1-3} = 0.666.. \times 10^{35} = 0.00666.. \times 10^{37}$$

The difference between the scale and the full decimal difference can result in the price ratio shifting some decimal places. However, we can find the appropriate price factor by considering what we expect the ratio to be from the initial prices. 10 / 1500 = 0.00666.., so we can see the proper price factor is 10^37.

The minimum formatted price can then be extrapolated from the initial price. The above initial price example can be interpreted as 0.00666.. WETH per OHM. Therefore, if you want to receive a minimum of 0.005 WETH per OHM, you would set minimum price as: $\Phi_{min} = 0.005 \times 10^{37}$.

Any alternative way to confirm your minimum price is correct is to redo the same calculation as used to determine initial price, with an updated minimum price for the payout token. Using the 0.005 WETH per OHM value, that would be an OHM price of $7.5 ($1500 x 0.005 = $7.5).

BondMarket

The BondMarket struct contains the core data about a bond market.

struct BondMarket {
    address owner; 
    ERC20 payoutToken;
    ERC20 quoteToken; 
    address callbackAddr; 
    bool capacityInQuote; 
    uint256 capacity;
    uint256 totalDebt;
    uint256 minPrice; 
    uint256 maxPayout; 
    uint256 sold; 
    uint256 purchased; 
    uint256 scale; 
}

Field	Type	Description
owner	address	Market owner. Sends payout tokens, receives quote tokens (defaults to creator)
payoutToken	ERC20 (address)	Payout Token (token paid out by market and provided by creator)
quoteToken	ERC20 (address)	Quote Token (token to be received by the market and provided by purchaser)
callbackAddr	address	Address to call for any operations on bond purchase. Must inherit to IBondCallback
capacityInQuote	bool	Capacity limit is in payment token (true) or in payout (false, default)
capacity	uint256	Capacity remaining
totalDebt	uint256	Total payout token debt from market
minPrice	uint256	Minimum price (debt will stop decaying to maintain this)
maxPayout	uint256	Max payout tokens out in one order
sold	uint256	Payout tokens out
purchased	uint256	Quote tokens in
scale	uint256	Scaling factor for the market (see MarketParams struct)

BondTerms

struct BondTerms {
    uint256 controlVariable; 
    uint256 maxDebt; 
    uint48 vesting; 
    uint48 conclusion; 
}

Field	Type	Description
controlVariable	uint256	Scaling variable for price
maxDebt	uint256	Max payout token debt accrued
vesting	uint48	Length of time from deposit to expiry if fixed-term, vesting timestamp if fixed-expiry
conclusion	uint48	Timestamp when market no longer offered

BondMetadata

struct BondMetadata {
    uint48 lastTune; 
    uint48 lastDecay; 
    uint32 length; 
    uint32 depositInterval; 
    uint32 tuneInterval; 
    uint32 tuneAdjustmentDelay; 
    uint32 debtDecayInterval; 
    uint256 tuneIntervalCapacity; 
    uint256 tuneBelowCapacity; 
    uint256 lastTuneDebt; 
}

Field	Type	Description
lastTune	uint48	Last timestamp when control variable was tuned
lastDecay	uint48	Last timestamp when market was created and debt was decayed
length	uint32	Time from creation to conclusion
depositInterval	uint32	Target frequency of deposits
tuneInterval	uint32	Frequency of tuning
tuneAdjustmentDelay	uint32	Time to implement downward tuning adjustments
debtDecayInterval	uint32	Interval over which debt should decay completely
tuneIntervalCapacity	uint256	Capacity expected to be used during a tuning interval
tuneBelowCapacity	uint256	Capacity that the next tuning will occur at
lastTuneDebt	uint256	Target debt calculated at last tuning

Methods

closeMarket

function closeMarket(uint256 id_) external nonpayable

Disable existing bond marketMust be market owner

Parameters

Name	Type	Description
id_	uint256	ID of market to close

createMarket

function createMarket(bytes params_) external nonpayable returns (uint256)

Creates a new bond market

See specific auctioneer implementations for details on encoding the parameters.

Parameters

Name	Type	Description
params_	bytes	Configuration data needed for market creation, encoded in a bytes array

Returns

Name	Type	Description
id	uint256	ID of new bond market

currentCapacity

function currentCapacity(uint256 id_) external view returns (uint256)

Returns current capacity of a market

Parameters

Name	Type	Description
id_	uint256	undefined

Returns

Name	Type	Description
_0	uint256	undefined

currentControlVariable

function currentControlVariable(uint256 id_) external view returns (uint256)

Up to date control variable

Accounts for control variable adjustment

Parameters

Name	Type	Description
id_	uint256	ID of market

Returns

Name	Type	Description
_0	uint256	Control variable for market in payout token decimals

currentDebt

function currentDebt(uint256 id_) external view returns (uint256)

Calculate debt factoring in decay

Accounts for debt decay since last deposit

Parameters

Name	Type	Description
id_	uint256	ID of market

Returns

Name	Type	Description
_0	uint256	Current debt for market in payout token decimals

getAggregator

function getAggregator() external view returns (contract IBondAggregator)

Returns the Aggregator that services the Auctioneer

Returns

Name	Type	Description
_0	contract IBondAggregator	undefined

getMarketInfoForPurchase

function getMarketInfoForPurchase(uint256 id_) external view returns (address owner, address callbackAddr, contract ERC20 payoutToken, contract ERC20 quoteToken, uint48 vesting, uint256 maxPayout)

Provides information for the Teller to execute purchases on a Market

Parameters

Name	Type	Description
id_	uint256	Market ID

Returns

Name	Type	Description
owner	address	Address of the market owner (tokens transferred from this address if no callback)
callbackAddr	address	Address of the callback contract to get tokens for payouts
payoutToken	contract ERC20	Payout Token (token paid out) for the Market
quoteToken	contract ERC20	Quote Token (token received) for the Market
vesting	uint48	Timestamp or duration for vesting, implementation-dependent
maxPayout	uint256	Maximum amount of payout tokens you can purchase in one transaction

getTeller

function getTeller() external view returns (contract IBondTeller)

Returns the Teller that services the Auctioneer

Returns

Name	Type	Description
teller	contract IBondTeller	Address of the Teller contract servicing the Auctioneer

isInstantSwap

function isInstantSwap(uint256 id_) external view returns (bool)

Does market send payout immediately

Parameters

Name	Type	Description
id_	uint256	Market ID to search for

Returns

Name	Type	Description
_0	bool	undefined

isLive

function isLive(uint256 id_) external view returns (bool)

Is a given market accepting deposits

Parameters

Name	Type	Description
id_	uint256	ID of market

Returns

Name	Type	Description
_0	bool	undefined

marketPrice

function marketPrice(uint256 id_) external view returns (uint256)

Calculate current market price of payout token in quote tokens

Accounts for debt and control variable decay since last deposit (vs _marketPrice())

Parameters

Name	Type	Description
id_	uint256	ID of market

Returns

Name	Type	Description
_0	uint256	Price for market in configured decimals (see MarketParams)

marketScale

function marketScale(uint256 id_) external view returns (uint256)

Scale value to use when converting between quote token and payout token amounts with marketPrice()

Parameters

Name	Type	Description
id_	uint256	ID of market

Returns

Name	Type	Description
_0	uint256	Scaling factor for market in configured decimals

maxAmountAccepted

function maxAmountAccepted(uint256 id_, address referrer_) external view returns (uint256)

Returns maximum amount of quote token accepted by the market

Parameters

Name	Type	Description
id_	uint256	ID of market
referrer_	address	Address of referrer, used to get fees to calculate accurate payout amount. Inputting the zero address will take into account just the protocol fee.

Returns

Name	Type	Description
_0	uint256	undefined

ownerOf

function ownerOf(uint256 id_) external view returns (address)

Returns the address of the market owner

Parameters

Name	Type	Description
id_	uint256	ID of market

Returns

Name	Type	Description
_0	address	undefined

payoutFor

function payoutFor(uint256 amount_, uint256 id_, address referrer_) external view returns (uint256)

Payout due for amount of quote tokens

Accounts for debt and control variable decay so it is up to date

Parameters

Name	Type	Description
amount_	uint256	Amount of quote tokens to spend
id_	uint256	ID of market
referrer_	address	Address of referrer, used to get fees to calculate accurate payout amount. Inputting the zero address will take into account just the protocol fee.

Returns

Name	Type	Description
_0	uint256	amount of payout tokens to be paid

pullOwnership

function pullOwnership(uint256 id_) external nonpayable

Accept ownership of a marketMust be market newOwner

The existing owner must call pushOwnership prior to the newOwner calling this function

Parameters

Name	Type	Description
id_	uint256	Market ID

purchaseBond

function purchaseBond(uint256 id_, uint256 amount_, uint256 minAmountOut_) external nonpayable returns (uint256 payout)

Exchange quote tokens for a bond in a specified marketMust be teller

Parameters

Name	Type	Description
id_	uint256	ID of the Market the bond is being purchased from
amount_	uint256	Amount to deposit in exchange for bond (after fee has been deducted)
minAmountOut_	uint256	Minimum acceptable amount of bond to receive. Prevents frontrunning

Returns

Name	Type	Description
payout	uint256	Amount of payout token to be received from the bond

pushOwnership

function pushOwnership(uint256 id_, address newOwner_) external nonpayable

Designate a new owner of a market. Must be existing market owner to call.

Doesn't change permissions until newOwner calls pullOwnership

Parameters

Name	Type	Description
id_	uint256	Market ID
newOwner_	address	New address to give ownership to

setAllowNewMarkets

function setAllowNewMarkets(bool status_) external nonpayable

Change the status of the auctioneer to allow creation of new markets

Setting to false and allowing active markets to end will sunset the auctioneer

Parameters

Name	Type	Description
status_	bool	Allow market creation (true) : Disallow market creation (false)

setCallbackAuthStatus

function setCallbackAuthStatus(address creator_, bool status_) external nonpayable

Change whether a market creator is allowed to use a callback address in their markets or notMust be guardian

Callback is believed to be safe, but a whitelist is implemented to prevent abuse

Parameters

Name	Type	Description
creator_	address	Address of market creator
status_	bool	Allow callback (true) : Disallow callback (false)

setDefaults

function setDefaults(uint32[6] defaults_) external nonpayable

Set the auctioneer defaultsMust be policy

The defaults set here are important to avoid edge cases in market behavior, e.g. a very short market reacts doesn't tune wellOnly applies to new markets that are created after the change

Parameters

Name	Type	Description
defaults_	uint32[6]	Array of default values 1. Tune interval - amount of time between tuning adjustments 2. Tune adjustment delay - amount of time to apply downward tuning adjustments 3. Minimum debt decay interval - minimum amount of time to let debt decay to zero 4. Minimum deposit interval - minimum amount of time to wait between deposits 5. Minimum market duration - minimum amount of time a market can be created for 6. Minimum debt buffer - the minimum amount of debt over the initial debt to trigger a market shutdown

setIntervals

function setIntervals(uint256 id_, uint32[3] intervals_) external nonpayable

Set market intervals to different values than the defaultsMust be market owner

Changing the intervals could cause markets to behave in unexpected way tuneInterval should be greater than tuneAdjustmentDelay

Parameters

Name	Type	Description
id_	uint256	Market ID
intervals_	uint32[3]	Array of intervals (3) 1. Tune interval - Frequency of tuning 2. Tune adjustment delay - Time to implement downward tuning adjustments 3. Debt decay interval - Interval over which debt should decay completely