Writing your message sending contract

Here’s how you write a contract on Sepolia that dispatches a message using Hashi’s Yaho contract. This message will be relayed to Chiado and trigger the callback.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IYaho {
    function dispatchMessageToAdapters(
        uint256 targetChainId,
        uint256 threshold,
        address targetAddress,
        bytes memory data,
        address[] memory reporters,
        address[] memory adapters
    ) external;
}

contract SepoliaSender {
    IYaho public yaho = IYaho(0x21eAB033C7D2DF6A67AeF6C5Bda9A7F151eB9f52);  // Yaho address on Sepolia
    uint256 public threshold;
    address[] public reporters;
    address[] public adapters;

    constructor(address _yaho, uint256 _threshold, address[] memory _reporters, address[] memory _adapters) {
        threshold = _threshold;
        reporters = _reporters;
        adapters = _adapters;
    }

    // Function to send a cross-chain message to Chiado
    function sendMessageToChiado(
        uint256 targetChainId, 
        address targetAddress, 
        string memory _message
    ) public {
        bytes memory data = abi.encode(_message);
        yaho.dispatchMessageToAdapters(targetChainId, threshold, targetAddress, data, reporters, adapters);
    }
}

Explanation:

• The contract interacts with the Yaho contract on Sepolia to dispatch a message to Chiado using dispatchMessageToAdapters.

• The sendMessageToChiado function takes the target chain ID(10200 for Chiado), target address (ChiadoReceiver contract on Chiado), and the message to be sent.

• The reporters, adapters, and threshold are passed into the Yaho contract for cross-chain message validation and relaying.

Deployment:

• Deploy this contract on Sepolia, passing the reporters, adapters, and threshold into the constructor.

• A list of reporters and adapters contract can be found in: Oracles

• Yaho contract address can be found in Yaho & Yaru

• Threshold must equal to expectedThreshold in Receiver contract.