1. Summary

The SingleSpotDebtCeilingSetter is meant to recompute the debtCeiling for a single collateral type inside the SAFEEngine. The setter inherits functionality from the IncreasingTreasuryReimbursement.

2. Contract Variables & Functions

Variables

• manualSetters[usr: address] - addManualSetter/removeManualSetter - auth mechanism for addresses that can call manualUpdateCeiling

• maxCollateralCeiling - the max amount of system coins that can be generated using the collateral type with collateralName

• minCollateralCeiling - the min amount of system coins that must be generated using the collateral type with collateralName

• ceilingPercentageChange - premium on top of the current amount of debt (backed by the collateral type with collateralName) minted. This is used to calculate a new ceiling

• lastUpdateTime - when the debt ceiling was last updated

• updateDelay - enforced time gap between calls

• lastManualUpdateTime - last timestamp of a manual update

• blockIncreaseWhenRevalue - flag that blocks an increase in the debt ceiling when the redemption rate is positive

• blockDecreaseWhenDevalue - flag that blocks a decrease in the debt ceiling when the redemption rate is negative

• collateralName - the targeted collateral's name

• safeEngine - the SAFEEngine contract

• oracleRelayer - the OracleRelayer contract

Functions

• modifyParameters - modifies contract parameters

• autoUpdateCeiling(feeReceiver: address) external - periodically updates the debt ceiling for the collateral type with collateralName. Can be called by anyone

• manualUpdateCeiling() - authed function that allows manualSetters to update the debt ceiling whenever they want

• getNextCollateralCeiling() public view returns (uint256) - view function meant to return the new and upcoming debt ceiling. It also checks for allowsIncrease and allowsDecrease

• getRawUpdatedCeiling() external view returns (uint256) - view function meant to return the new and upcoming debt ceiling. It does not perform checks for allowsIncrease and allowsDecrease

• allowsIncrease(redemptionRate: uint256, currentDebtCeiling: uint256, updatedCeiling: uint256) public view returns (allowsIncrease: bool) - view function meant to return whether an increase in the debt ceiling is currently allowed

• allowsDecrease(redemptionRate: uint256, currentDebtCeiling: uint256, updatedCeiling: uint256) public view returns (allowsDecrease: bool) - view function meant to return whether a decrease in the debt ceiling is currently allowed

Modifiers

• isManualSetter - checks whether an address is part of manualSetters.

Events

• AddManualSetter - emitted when a new manual setter is added. Contains:

  • account - new manual setter address

• RemoveManualSetter - emitted when a manual setter address is removed/blacklisted. Contains:

  • account - the setter address that's removed

• UpdateCeiling - emitted when a new ceiling is computed and set. Contains:

  • nextCeiling - the new ceiling

3. Walkthrough

autoUpdateCeiling and manualUpdateCeiling can both be used to recompute the debt ceiling for the collateral type with collateralName, although manualUpdateCeiling can only be called by whitelisted manualSetters. Both autoUpdateCeiling and manualUpdateCeiling call getNextCollateralCeiling to calculate the new ceiling.

getNextCollateralCeiling takes into account allowsIncrease and allowsDecrease to determine whether it is allowed to computed a higher or a lower ceiling (compared to the current one).

Both allowsIncrease and allowsDecrease look at the current redemptionRate as well as at blockIncreaseWhenRevalue and blockDecreaseWhenDevalue to see whether they should allow or disallow an increase or decrease in the debt ceiling. blockIncreaseWhenRevalue and blockDecreaseWhenDevalue are by default set to zero so increases or decreases are always allowed, no matter what sign the redemption rate has.