StabilityFeeTreasury is meant to allow other contracts or EOAs to pull funds (stability fees) in order to finance their operations. The treasury is set up as a secondaryReceiver in the TaxCollector. Anyone can periodically call the contract in order to recompute an optimal amount of fees that should be kept in the treasury and send any additional surplus to the extraSurplusReceiver.authorizedAccounts[usr: address] - addAuthorization/removeAuthorization - auth mechanismsallowance[receiver: address] - total withdrawal allowancepulledPerBlock[usr: address, blockNr: uint256] - total amount pulled by a user on a specific blocksafeEngine - address of the SAFEEnginecoinJoin - system coin adapter addressextraSurplusReceiver - address that receives extra unused funds from the treasurytreasuryCapacity - maximum amount of stability fees should be kept in the treasuryminimumFundsRequired - minimum amount of stability fees that must be kept in the treasury at all timesexpensesMultiplier - multiplier for the expenses incurred since the last transferSurplusFunds call. Ensures there's a buffer of funds on top of the expected expenses until the next transferSurplusFunds callsurplusTransferDelay - delay between two transferSurplusFunds callsexpensesAccumulator - total expenses incurred since treasury deploymentaccumulatorTag - latest snapshot of expensesAccumulatorlatestSurplusTransferTime - last timestamp when transferSurplusFunds was calledcontractEnabled - global settlement flagAllowance - struct that specifies the total and the per-block withdrawal allowance for an address. Contains:total - the total allowance (in RAD)perBlock - the per-block allowance (in RAD)isAuthorized - checks whether an address is part of authorizedAddresses (and thus can call authed functions).accountNotTreasury - checks that the receiver account for treasury funds is not the treasury itselfmodifyParameters() - authorized function for changing treasury parametersdisableContract() - disable the treasury and transfer all of its funds to theextraSurplusReceiverjoinAllCoins() - join any ERC20 system coins that the treasury has into internal coin form (SAFEEngine.coinBalance)getAllowance(account: address) - get the total and the per-block allowance for a usersetTotalAllowance(account: address, rad: uint256) - authorized function that changes the total allowed amount an address can withdraw from the treasurysetPerBlockAllowance(account: address, rad: uint256) - authorized function that changes the amount that an address can withdraw from the treasury every blockgiveFunds(account: address, rad: uint256) - governance controlled function that transfers stability fees from the treasury to a destination addresstakeFunds(account: address, rad: uint256) - governance controlled function that transfers stability fees from a target address to the treasurypullFunds(dstAccount: address, token: address, wad: uint256) - take funds from the treasury. Reverts if the caller is not allowed to withdraw or if their per-block allowance doesn't allow ittransferSurplusFunds() - recalculate the amount of stability fees that should remain in the treasury and transfer additional funds to the extraSurplusReceiverAddAuthorization - emitted when a new address becomes authorized. Contains:account - the new authorized accountRemoveAuthorization - emitted when an address is de-authorized. Contains:account - the address that was de-authorizedModifyParameters - emitted when a parameter is updated.DisableContract - emitted when the contract is disabled.SetTotalAllowance - emitted when the total allowance for an address is set. Contains:account - the account whose allowance was changedrad - the new total allowance for the accountSetPerBlockAllowance - emitted when the per-block allowance for an address is set. Contains:account - the account whose per-block allowance was changedrad - the new total allowance for the accountGiveFunds - emitted when governance offers funds to an address. Contains:account - the account that received fundsrad - the amount of funds that were givenexpensesAccumulator - the sum of all the expenses incurred since the contract was deployedTakeFunds - emitted when governance calls the treasury to take funds from an address. Contains:account - the account the treasury takes system coins fromrad - the amount of (internal) system coins to take (expressed as RAD)PullFunds - emitted when an approved address pulls funds from the treasury. Contains:sender - the msg.sender that called pullFundsdstAccount - the address that received fundstoken - the address of the token being transferred (in this case it's always the address of the ERC20 system coin)rad - the total amount of internal system coins transferredexpensesAccumulator - the sum of all the expenses incurred since the contract was deployedTransferSurplusFunds - emitted when surplus funds above the optimum amount are sent to the accounting engine. Contains:extraSurplusReceiver - the address that received the extra fundsfundsToTransfer - the amount of funds sentTaxCollector or by anyone who is willing to send system coins (either internally or as ERC20 tokens) to it. Governance can also use takeFunds to transfer internal system coins from a source address to the treasury.
Governance is in charge with setting up authorized addresses that can pullFunds out of the treasury (if their total or per-block allowance permits) as well as setting treasury parameters in order to determine the optimum amount of funds that should remain in the contract at any time. We define "optimum" as a multiplier (expensesMultiplier) of the latest expenses incurred by the treasury since the last transferSurplusFunds call. transferSurplusFunds is the way the treasury recalculates the amount of funds it should keep in reserves and transfers any surplus to the extraSurplusReceiver. Note that there is a surplusTransferDelay time delay between recalculating the optimum and transferring surplus out of the contract.extraSurplusReceiveror to the Treasury ItselfextraSurplusReceiver using giveFunds, expensesAccumulator will not increase. In case an address wants to pullFunds and send them to the extraSurplusReceiver, pullFunds will revert.
pullFunds will silently fail if the dstAccount is the treasury contract itself, whereas giveFunds will revert.