Custom Contract Development

For more complex dApps requiring custom logic, Mailbox contracts can be integrated directly into custom contracts:

Example: Using IMailbox Interface

import { IMailbox } from "@ssv/src/core/interfaces/IMailbox.sol";

contract CustomCrossChainDApp {
    IMailbox public immutable mailbox;
    
    constructor(address _mailbox) {
        mailbox = IMailbox(_mailbox);
    }
    
    function sendMessage(uint256 destinationChain, address targetContract, 
                        uint256 sessionId, string memory messageType, bytes memory data) external {
        mailbox.write(destinationChain, targetContract, sessionId, messageType, data);
    }
    
    function processMessage(uint256 sourceChain, address sourceContract, 
                          uint256 sessionId, string memory messageType) external {
        bytes memory m = mailbox.read(sourceChain, sourceContract, sessionId, messageType);
        
        if (m.length == 0) {
            revert EmptyMessage();
        }
        
        // Decode the message data
        (address sender, address receiver, uint256 amount) = abi.decode(m, (address, address, uint256));
        
        // Process the message
        // ... custom logic here ...
        
        // Send acknowledgment
        bytes memory ack = abi.encode("OK");
        mailbox.write(sourceChain, sourceContract, sessionId, "ACK", ack);
    }
}

Reading and Writing Messages

The IMailbox interface provides two core functions for cross-chain communication:

• write(uint256 chainId, address contract, uint256 sessionId, string messageType, bytes data) - Send message to another chain
• read(uint256 chainId, address contract, uint256 sessionId, string messageType) - Read message from another chain

This approach provides full control over cross-chain logic while maintaining atomicity guarantees.