# Yield Reserve [Git Source](https://github.com/Sperax/USDs-v2/blob/ff71faf9d7e40d2b2764e5e8f2acc631f31489aa/contracts/buyback/YieldReserve.sol) **Inherits:** ReentrancyGuard, Ownable **Author:** Sperax Foundation This contract allows users to swap supported stable-coins for yield earned by the USDs protocol. It sends USDs to the Dripper contract for rebase and to the Buyback Contract for buyback. ## **State Variables** ### **vault** ```solidity address public vault; ``` ### **oracle** ```solidity address public oracle; ``` ### **buyback** ```solidity address public buyback; ``` ### **dripper** ```solidity address public dripper; ``` ### **buybackPercentage** ```solidity uint256 public buybackPercentage; ``` ### **tokenData** ```solidity mapping(address => TokenData) public tokenData; ``` ## **Functions** ### **constructor** Constructor of the YieldReserve contract. ```solidity constructor(address _buyback, address _vault, address _oracle, address _dripper); ``` **Parameters** | Name | Type | Description | | --------- | ------- | -------------------------------- | | \_buyback | address | Address of the Buyback contract. | | \_vault | address | Address of the Vault. | | \_oracle | address | Address of the Oracle. | | \_dripper | address | Address of the Dripper contract. | ### **swap** Swap function to be called by frontend users. ```solidity function swap(address _srcToken, address _dstToken, uint256 _amountIn, uint256 _minAmountOut) external; ``` **Parameters** | Name | Type | Description | | -------------- | ------- | ------------------------------- | | \_srcToken | address | Source/Input token. | | \_dstToken | address | Destination/Output token. | | \_amountIn | uint256 | Input token amount. | | \_minAmountOut | uint256 | Minimum output tokens expected. | ### **toggleSrcTokenPermission** Allow or disallow a specific `token` for use as a source/input token. ```solidity function toggleSrcTokenPermission(address _token, bool _isAllowed) external onlyOwner; ``` **Parameters** | Name | Type | Description | | ----------- | ------- | ---------------------------------------------------------------------------------------------------- | | \_token | address | Address of the token to be allowed or disallowed. | | \_isAllowed | bool | If set to true, the token will be allowed as a source/input token; otherwise, it will be disallowed. | ### **toggleDstTokenPermission** Allow or disallow a specific `token` for use as a destination/output token. *Reverts if caller is not owner.* ```solidity function toggleDstTokenPermission(address _token, bool _isAllowed) external onlyOwner; ``` **Parameters** | Name | Type | Description | | ----------- | ------- | ---------------------------------------------------------------------------------------------------------- | | \_token | address | Address of the token to be allowed or disallowed. | | \_isAllowed | bool | If set to true, the token will be allowed as a destination/output token; otherwise, it will be disallowed. | ### **withdraw** Emergency withdrawal function for unexpected situations. ```solidity function withdraw(address _token, address _receiver, uint256 _amount) external onlyOwner; ``` **Parameters** | Name | Type | Description | | ---------- | ------- | ------------------------------------- | | \_token | address | Address of the asset to be withdrawn. | | \_receiver | address | Address of the receiver of tokens. | | \_amount | uint256 | Amount of tokens to be withdrawn. | ### **updateBuybackPercentage** Set the percentage of newly minted USDs to be sent to the Buyback contract. *Reverts if caller is not owner.* *The remaining USDs are sent to VaultCore for rebase.* ```solidity function updateBuybackPercentage(uint256 _toBuyback) public onlyOwner; ``` **Parameters** | Name | Type | Description | | ----------- | ------- | ------------------------------------------------------------ | | \_toBuyback | uint256 | The percentage of USDs sent to Buyback (e.g., 3000 for 30%). | ### **updateBuyback** Update the address of the Buyback contract. *Reverts if caller is not owner.* ```solidity function updateBuyback(address _newBuyBack) public onlyOwner; ``` **Parameters** | Name | Type | Description | | ------------ | ------- | ------------------------------------ | | \_newBuyBack | address | New address of the Buyback contract. | ### **updateOracle** Update the address of the Oracle contract. *Reverts if caller is not owner.* ```solidity function updateOracle(address _newOracle) public onlyOwner; ``` **Parameters** | Name | Type | Description | | ----------- | ------- | ----------------------------------- | | \_newOracle | address | New address of the Oracle contract. | ### **updateDripper** Update the address of the Dripper contract. *Reverts if caller is not owner.* ```solidity function updateDripper(address _newDripper) public onlyOwner; ``` **Parameters** | Name | Type | Description | | ------------ | ------- | ------------------------------------ | | \_newDripper | address | New address of the Dripper contract. | ### **updateVault** Update the address of the VaultCore contract. *Reverts if caller is not owner.* ```solidity function updateVault(address _newVault) public onlyOwner; ``` **Parameters** | Name | Type | Description | | ---------- | ------- | -------------------------------------- | | \_newVault | address | New address of the VaultCore contract. | ### **swap** Swap allowed source token for allowed destination token. ```solidity function swap(address _srcToken, address _dstToken, uint256 _amountIn, uint256 _minAmountOut, address _receiver) public nonReentrant; ``` **Parameters** | Name | Type | Description | | -------------- | ------- | ------------------------------- | | \_srcToken | address | Source/Input token. | | \_dstToken | address | Destination/Output token. | | \_amountIn | uint256 | Input token amount. | | \_minAmountOut | uint256 | Minimum output tokens expected. | | \_receiver | address | Receiver of the tokens. | ### **mintUSDs** Mints USDs directly with the allowed collaterals for USDs. *Only collaterals configured in USDs vault are allowed to be used for minting.* ```solidity function mintUSDs(address _token) public nonReentrant; ``` **Parameters** | Name | Type | Description | | ------- | ------- | ---------------------------------- | | \_token | address | Address of token to mint USDs with | ### **getTokenBForTokenA** Get an estimate of the output token amount for a given input token amount. ```solidity function getTokenBForTokenA(address _srcToken, address _dstToken, uint256 _amountIn) public view returns (uint256); ``` **Parameters** | Name | Type | Description | | ---------- | ------- | --------------------------- | | \_srcToken | address | Input token address. | | \_dstToken | address | Output token address. | | \_amountIn | uint256 | Input amount of \_srcToken. | **Returns** | Name | Type | Description | | ---- | ------- | ------------------------------ | | | uint256 | Estimated output token amount. | ### **\_sendUSDs** Distributes USDs to the Buyback and Dripper contracts based on buybackPercentage. *Sends a portion of the USDs balance to the Buyback contract and the remaining to the Dripper contract for rebase.* ```solidity function _sendUSDs() private; ``` ## **Events** ### **Swapped** ```solidity event Swapped( address indexed srcToken, address indexed dstToken, address indexed dstReceiver, uint256 amountIn, uint256 amountOut ); ``` ### **USDsMintedViaSwapper** ```solidity event USDsMintedViaSwapper(address indexed collateralAddr, uint256 usdsMinted); ``` ### **Withdrawn** ```solidity event Withdrawn(address indexed token, address indexed receiver, uint256 amount); ``` ### **BuybackPercentageUpdated** ```solidity event BuybackPercentageUpdated(uint256 toBuyback); ``` ### **BuybackUpdated** ```solidity event BuybackUpdated(address newBuyback); ``` ### **OracleUpdated** ```solidity event OracleUpdated(address newOracle); ``` ### **VaultUpdated** ```solidity event VaultUpdated(address newVault); ``` ### **DripperUpdated** ```solidity event DripperUpdated(address newDripper); ``` ### **USDsSent** ```solidity event USDsSent(uint256 toBuyback, uint256 toDripper); ``` ### **SrcTokenPermissionUpdated** ```solidity event SrcTokenPermissionUpdated(address indexed token, bool isAllowed); ``` ### **DstTokenPermissionUpdated** ```solidity event DstTokenPermissionUpdated(address indexed token, bool isAllowed); ``` ## **Errors** ### **InvalidSourceToken** ```solidity error InvalidSourceToken(); ``` ### **InvalidDestinationToken** ```solidity error InvalidDestinationToken(); ``` ### **AlreadyInDesiredState** ```solidity error AlreadyInDesiredState(); ``` ### **TokenPriceFeedMissing** ```solidity error TokenPriceFeedMissing(); ``` ## **Structs** ### **TokenData** ```solidity struct TokenData { bool srcAllowed; bool dstAllowed; uint160 conversionFactor; } ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.sperax.io/master/technical-documents/smart-contracts/yield-reserve.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.