EUR0 Classical Oracle

Unlike other Usual protocols, the ClassicalOracle contract has been merged with the AbstractOracle one

High-Level Overview

The ClassicalOracle contract is used by DaoCollateral to fetch the price of external tokens. The price of tokens is used for minting and redeeming the right amount of EUR0. It is an upgradable contract.

Contract Summary

The logic contained in ClassicalOracle includes:

• Initializing tokenToOracleInfo for each supported token with a ChainlinkV3Aggregator-compatible price feed

• Converting the price of the oracle of arbitrary decimals into wad (18 decimals)

• Computing a quote (USD value) for a given token and amount of tokens

• Making sure stablecoins haven’t depegged

• Allowing the admin to set the maximum allowed price variation for stablecoins

• Interacting with the aggregator to fetch the latest price and its number of decimals

Inherited Contracts

• IOracle: Common interface used by other contracts and external service (e.g. the dApp) to interact with the ClassicalOracle. Ensures function signatures are the ones expected by these external actors.

• Initializable: Allows to handle contract setup and upgrades.

Functionality Breakdown

After deploying the contract, the administrator should initialize the price feed for all supported collateral thanks to the initializeTokenOracle function.

When another contract or external service calls getPrice or getQuote, the contract calls the virtual function _latestRoundData passing the desired token as parameter. This function is implemented in ClassicalOracle and retrieves the associated price aggregator for this token, then calls decimals and latestRoundData.

Functions Description

Public/External Functions

• initializeTokenOracle(address token, address dataSource, uint64 timeout, bool isStablecoin): Registers a new supported token or updates the data source (price aggregator) for an existing token. The new price feed must have been last updated within the last timeout seconds. This check is only performed once. If isStablecoin is true, the depeg check will be enabled and getPrice/getQuote will revert if the price is not around $1.

• getMaxDepegThreshold(): Returns the current maximum allowed price variation for stablecoins in basis points (e.g. with a value of 500, getPrice and getQuote will revert if the price of a stablecoin is outside the range $0.95-$1.05). View function.

• setMaxDepegThreshold(uint256 maxAuthorizedDepegPrice): Updates the maximum allowed price variation and emits a SetMaxDepegThreshold event. Nonpayable function. Reserved for admin use only.

• getPrice(address token): Returns the price of the given token scaled to 18 decimals (e.g. a return value of 3e18 means the token price is $3). Reverts if the token is a stablecoin and it’s outside of the allowed price variation range. View function.

• getQuote(address token): Returns the USD value equivalent to the given amount of the given token (e.g. if the token price is $3, calling with 1e6 will return 3e6, no matter the number of decimals of the token). Reverts if the token is a stablecoin and it’s outside of the allowed price variation range. View function.