Example: Cross-Chain ENS Resolution

Resolve an Ethereum ENS name on another chain.

What if you want to use your mainnet ENS address on other chains?

In this example, we fetch data from mainnet to resolve an ENS address on chain, then store the results into a mapping. We deploy a custom ENSUtil contract on mainnet that combines registry.resolver(namehash).addr(namehash) into a single function, so we only need one cross chain call.

Extra logic could be added to the callback handler, to interact with the resolved address in some way.

pragma solidity ^0.8.14;

import {IERC721} from "openzeppelin/token/ERC721/IERC721.sol";
import {TelepathyOracle} from "src/oracle/TelepathyOracle.sol";
import {OracleCallbackBase} from "src/oracle/OracleCallbackBase.sol";
import {ENSUtil} from "src/examples/ens/ENSUtil.sol";

struct Request {
    address sender;
    bytes32 node;
}

struct ResolvedAddress {
    bool success;
    address addr;
    uint88 timestamp;
}

/// @title ENSQueryExample
/// @notice Example contract that queries mainnet to resolve an ENS name on chain
contract ENSQueryExample is OracleCallbackBase {
    address ensUtil;
    TelepathyOracle oracle;

    /// @notice Maps oracle nonce to the address that requested the claim and the requested node
    mapping(uint256 => Request) public requests;
    /// @notice Maps resolved ENS names to their addresses (could be outdated)
    mapping(bytes32 => ResolvedAddress) public addresses;

    constructor(address _oracle, address _ensUtil) OracleCallbackBase(_oracle) {
        oracle = TelepathyOracle(_oracle);
        ensUtil = _ensUtil;
    }

    function sendQuery(bytes32 _node) external returns (uint256) {
        uint256 nonce = oracle.requestCrossChain(
            address(ensUtil),
            abi.encodeWithSelector(ENSUtil.resolve.selector, _node),
            address(this)
        );
        requests[nonce] = Request(msg.sender, _node);
        return nonce;
    }

    function handleOracleResponse(
        uint256 _nonce,
        bytes memory _responseData,
        bool _responseSuccess
    ) internal override {
        address resolved;
        if (_responseSuccess) {
            resolved = abi.decode(_responseData, (address));
        }
        bytes32 node = requests[_nonce].node;
        delete requests[_nonce];
        // node => resolved
        addresses[node] = ResolvedAddress(
            _responseSuccess,
            resolved,
            uint88(block.timestamp)
        );
        // we can add extra effects here if desired
    }
}