NablaBackstopPool

The backstop pool takes most of the risk of a set of swap pools backed by it. Whenever a swap pool is low on reserves and a LPer wants to withdraw some liquidity, they can conduct an insurance withdrawal (burn swap pool shares, reimbursed in backstop liquidity) to avoid paying a high slippage. The backstop pool owns all excess liquidity in its swap pools, but is also liable for potential liquidity gaps. In return, the backstop pool receives a cut of the swap fees.

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Withdrawal

struct Withdrawal {
  uint128 startClaimPeriod;
  uint128 endClaimPeriod;
  uint256 sharesToBurn;
}

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SwapPoolConfig

struct SwapPoolConfig {
  uint128 insuranceFeeBps;
  bool isCovered;
}

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router

contract IRouter router

router instance for this backstop pool

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getBackedPool

function getBackedPool(uint256 _index) external view returns (address swapPool_)

enumerate swap pools backed by this backstop pool

Parameters

Name	Type	Description
_index	uint256	index of the swap pool in coveredSwapPools array

Return Values

Name	Type	Description
swapPool_	address	swap pool address

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getBackedPoolCount

function getBackedPoolCount() external view returns (uint256 count_)

get swap pool count backed by this backstop pool

Return Values

Name	Type	Description
count_	uint256	number of swap pools

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getInsuranceFee

function getInsuranceFee(address _swapPool) external view returns (uint256 feeBps_)

get insurance withdrawal fee for a given swap pool

Parameters

Name	Type	Description
_swapPool	address	address of the swap pool

Return Values

Name	Type	Description
feeBps_	uint256	insurance witdrawal fee, in basis points (0.01%)

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deposit

function deposit(uint256 _depositAmount, uint256 _minLPAmountOut, uint256 _deadline, bytes[] _priceUpdateData) external payable returns (uint256 sharesToMint_)

Deposits amount of tokens into pool Will change cov ratio of pool, will increase delta to 0

By calling this function the price feeds get updated (IPriceOracleAdapter.updatePriceFeeds)

Parameters

Name	Type	Description
_depositAmount	uint256	The amount of backstop pool tokens to be deposited
_minLPAmountOut	uint256	The minimum amount of backstop pool LP tokens to mint
_deadline	uint256	Unix timestamp after which the transaction will revert
_priceUpdateData	bytes[]	Array of price update data of all assets involved (backstop pool and all swapPools as within coveredSwapPools[])

Return Values

Name	Type	Description
sharesToMint_	uint256	Total number of backstop pool LP tokens minted

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initiateWithdraw

function initiateWithdraw(uint256 _sharesToBurn) external returns (bool success_)

Starts the withdrawal process or overrides an existing one The user must finalize the withdrawal after the delay period has passed but before the claim period ends through finalizeWithdrawBackstopLiquidity() or finalizeWithdrawExcessSwapLiquidity()

Parameters

Name	Type	Description
_sharesToBurn	uint256	The liquidity to be withdrawn, an amount of backstop pool LP tokens

Return Values

Name	Type	Description
success_	bool	Confirmation of success

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cancelWithdraw

function cancelWithdraw() external returns (bool success_)

Cancels an initiated withdrawal

Return Values

Name	Type	Description
success_	bool	Confirmation of success

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finalizeWithdrawBackstopLiquidity

function finalizeWithdrawBackstopLiquidity(uint256 _minimumAmount, uint256 _deadline, bytes[] _priceUpdateData) external payable returns (uint256 payoutAmount_)

Finalizes the withdrawal process after the delay period has passed but before the claim period ends Withdraws backstop liquidity amount of asset ensuring minimum amount required

By calling this function the price feeds get updated (IPriceOracleAdapter.updatePriceFeeds)

Parameters

Name	Type	Description
_minimumAmount	uint256	Reject withdrawal if resulting amount is below
_deadline	uint256	Unix timestamp after which the transaction will revert
_priceUpdateData	bytes[]	Array of price update data of all assets involved (backstop pool and all swapPools as within coveredSwapPools[])

Return Values

Name	Type	Description
payoutAmount_	uint256	Amount of asset() tokens withdrawn

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redeemSwapPoolShares

function redeemSwapPoolShares(address _swapPool, uint256 _shares, uint256 _minAmountOut, uint256 _deadline, bytes[] _priceUpdateData) external payable returns (uint256 amountOut_)

Withdraw from a swap pool using backstop liquidity without slippage (backstop burn) only possible if swap pool's coverage ratio < 100%

By calling this function the price feeds get updated (IPriceOracleAdapter.updatePriceFeeds)

Parameters

Name	Type	Description
_swapPool	address	swap pool address
_shares	uint256	number of swap pool LP tokens to redeem, uses decimals of swap pool
_minAmountOut	uint256	minimum amount of backstop liquidity to receive, uses decimals of backstop pool
_deadline	uint256	Unix timestamp after which the transaction will revert
_priceUpdateData	bytes[]	Array of price update data of all assets involved (backstop pool and this swapPool)

Return Values

Name	Type	Description
amountOut_	uint256	amount of backstop liquidity paid-out, uses decimals of backstop pool

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finalizeWithdrawExcessSwapLiquidity

function finalizeWithdrawExcessSwapLiquidity(address _swapPool, uint256 _minAmount, uint256 _deadline, bytes[] _priceUpdateData) external payable returns (uint256 swapAmount_)

Finalizes the withdrawal process after the delay period has passed but before the claim period ends Withdraw from backstop pool, but receive excess liquidity of a swap pool instead of backstop liquidity

By calling this function the price feeds get updated (IPriceOracleAdapter.updatePriceFeeds)

Parameters

Name	Type	Description
_swapPool	address	swap pool address, must have a coverage ratio > 100%
_minAmount	uint256	minimum amount of swap pool liquidity to receive, uses decimals of swap pool
_deadline	uint256	Unix timestamp after which the transaction will revert
_priceUpdateData	bytes[]	Array of price update data of all assets involved (backstop pool and all swapPools as within coveredSwapPools[])

Return Values

Name	Type	Description
swapAmount_	uint256	amount of swap pool liquidity paid-out, uses decimals of swap pool

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redeemCrossSwapPoolShares

function redeemCrossSwapPoolShares(address _swapPool, address _targetSwapPool, uint256 _shares, uint256 _minAmount, uint256 _deadline, bytes[] _priceUpdateData) external payable returns (uint256 finalAmount_)

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getTotalPoolWorth

function getTotalPoolWorth(uint256[] _allTokenPrices) public view returns (int256 value_, int256 totalExcessLiquidity_)

return worth of the whole backstop pool in asset(), incl. all swap pools' excess liquidity and the backstop pool's liabilities this is a fixed point number, using the backstop pool decimals

ignoring if pools are paused or not, since liabilities still apply and we don't want the backstop pool worth to jump

Parameters

Name	Type	Description
_allTokenPrices	uint256[]	array of all token prices ([0] backstop pool token, [1] swap pool token_i, [2] swap pool token_i+1, ... [n] swap pool token_n) as within coveredSwapPools[]

Return Values

Name	Type	Description
value_	int256	total value of all backstop pool shares, in asset()
totalExcessLiquidity_	int256	total excess liquidity of all swap pools, in asset()

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sharesTargetWorth

function sharesTargetWorth(uint256 _sharesToBurn, uint256[] _allTokenPrices) public view returns (uint256 amount_)

Returns the worth of an amount of pool shares (LP tokens) in underlying principle

Parameters

Name	Type	Description
_sharesToBurn	uint256	The number of LP tokens to burn
_allTokenPrices	uint256[]	array of all token prices ([0] backstop pool token, [1] swap pool token_i, [2] swap pool token_i+1, ... [n] swap pool token_n) as within coveredSwapPools[]

Return Values

Name	Type	Description
amount_	uint256	The amount of asset() tokens that the shares are worth

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getPoolState

function getPoolState(uint256[] _allTokenPrices) external view returns (uint256 reserves_, int256 totalPoolWorth_, uint256 totalSupply_)

returns the backstop pool state

Parameters

Name	Type	Description
_allTokenPrices	uint256[]	array of all token prices ([0] backstop pool token, [1] swap pool token_i, [2] swap pool token_i+1, ... [n] swap pool token_n) as within coveredSwapPools[]

Return Values

Name	Type	Description
reserves_	uint256	current amount of asset in this pool
totalPoolWorth_	int256	total worth of the pool in asset()
totalSupply_	uint256	total amount of LP tokens minted

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getWithdrawal

function getWithdrawal(address _sender) external view returns (uint128 startClaimPeriod_, uint128 endClaimPeriod_, uint256 sharesToBurn_)

Get information about a user's initiated withdrawal

Parameters

Name	Type	Description
_sender	address	The user who initiated the withdrawal

Return Values

Name	Type	Description
startClaimPeriod_	uint128	The time when the withdrawal can be finalized, a unix timestamp
endClaimPeriod_	uint128	The time when the withdrawal can no longer be finalized, a unix timestamp
sharesToBurn_	uint256	The amount of LP tokens to burn

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getWithdrawalDelayAndClaimPeriod

function getWithdrawalDelayAndClaimPeriod() external view returns (uint128 delay_, uint128 claimPeriod_)

Get the delay and claim period for withdrawals

Return Values

Name	Type	Description
delay_	uint128	The delay before initiated withdrawals can be finalized, in seconds
claimPeriod_	uint128	The period within which initiated withdrawals can be claimed, in seconds