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Custom Validation Hook

This guide will outline how to create a custom validation hook for a CCA auction. Hooks are powerful extensions to CCA which unlock a wide range of features like bidding limits, allowlisting, and more.

Prerequisites​

  • Foundry
  • Basic understanding of the CCA contracts and Solidity

If you haven't already, please check out the quickstart guide.

Interface​

All validation hooks must implement the IValidationHook interface.

interface IValidationHook {
    function validate(uint256 maxPrice, uint128 amount, address owner, address sender, bytes calldata hookData) external;
}

This function is called by the auction contract during bid submission. To reject a bid, your hook MUST revert.

Parameters​

  • maxPrice: The maximum price the bidder is willing to pay
  • amount: The amount of currency the user is bidding
  • owner: The address of the user who will receive any purchased tokens or refunded currency
  • sender: The address of the user who is submitting the bid
  • hookData: Any extra data

Note that hookData is arbitrarily specified by the bidder and should NOT be trusted.

Introspection​

It is highly recommended to implement basic ERC165 introspection support for your hook. This will allow users to query for which capabilities the hook supports.

interface IERC165 {
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

You can also inherit from the base contract ValidationHookIntrospection which automatically implements support for IERC165 and IValidationHook. Make sure to override the supportsInterface function to return true for your specific hook interface.

interface ICustomValidationHook is IValidationHook, IERC165 {
    // Your custom hook interface here
}

contract CustomValidationHook is ValidationHookIntrospection {
    function supportsInterface(bytes4 interfaceId) public view override(ValidationHookIntrospection, IERC165) returns (bool) {
        return super.supportsInterface(interfaceId) || interfaceId == type(ICustomValidationHook).interfaceId;
    }
}

Deployment​

Hooks must be deployed before the auction is created as they must be set in the validationHook parameter of the auction. If your hook requires that only the auction is able to call validate, you can initialize the hook after deployment.

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