Writing and Broadcasting Contract Interactions on OP_NET

In this section, you’ll learn how to interact with smart contracts on the OP_NET metaprotocol, following a similar approach as shown in the token approval process. This guide will demonstrate how to craft and broadcast contract interactions, from writing the calldata to executing the transaction.

Step 1: Install Required Packages

Ensure you have the necessary dependencies installed to interact with OP_NET smart contracts.

npm install opnet bitcoinjs-lib
# or
yarn add opnet bitcoinjs-lib

Step 2: Set Up the Provider

First, you need to set up the provider to communicate with the OP_NET metaprotocol.

import * as bitcoinjs from "bitcoinjs-lib";
import { JSONRpcProvider } from "opnet";

// Define the OP_NET RPC provider
const rpcUrl = "https://regtest.opnet.org";
const provider = new JSONRpcProvider(rpcUrl);

// Define the Bitcoin network (e.g., regtest, mainnet)
const network = bitcoinjs.networks.regtest;

Step 3: Interact with a Contract

Now, we'll write an example function to interact with a smart contract. Similar to the approve() method shown previously, this process involves creating calldata, signing the transaction, and broadcasting it.

import {
  IInteractionParameters,
  OPNetLimitedProvider,
  TransactionFactory,
  Wallet,
} from "@btc-vision/transaction";
import { getContract, IOP_20Contract, OP_20_ABI, UTXO } from "opnet";

/**
 * Interacts with a smart contract on OP_NET.
 *
 * @param {Wallet} walletGet - The wallet object containing keypairs and addresses.
 * @param {string} contractAddress - The address of the smart contract.
 * @param {UTXO[]} utxos - The UTXOs for funding the transaction.
 * @returns Contract interaction result
 */
async function interactWithContract(
  walletGet: Wallet,
  contractAddress: string,
  utxos: UTXO[]
) {
  try {
    // Get the contract instance using the OP_20 ABI
    const contract = getContract<IOP_20Contract>(
      contractAddress,
      OP_20_ABI,
      provider,
      walletGet.p2tr
    );

    // Construct the calldata for the contract interaction (e.g., calling a function in the contract)
    const calldata = contract.someMethodToCall();

    // Create transaction parameters for the contract interaction
    const interactionParameters: IInteractionParameters = {
      from: walletGet.p2tr,
      to: contract.address.toString(),
      utxos, // UTXOs to fund the transaction
      signer: walletGet.keypair, // Wallet's keypair for signing the transaction
      network, // The BitcoinJS network
      feeRate: 100, // Fee rate in satoshis per byte
      priorityFee: 5000n, // Priority fee for faster transaction
      calldata: calldata as Buffer, // The calldata for the contract interaction
    };

    // Create and sign the transaction
    const transactionFactory = new TransactionFactory();
    const signedTx = await transactionFactory.signInteraction(
      interactionParameters
    );

    // Broadcast the transaction
    const limitedProvider = new OPNetLimitedProvider(
      "https://regtest.opnet.org"
    ); // Initialize the OP_NET limited provider
    const firstTxBroadcast = await limitedProvider.broadcastTransaction(
      signedTx[0],
      false
    );
    if (!firstTxBroadcast || !firstTxBroadcast.success) {
      throw new Error("First transaction broadcast failed.");
    }

    const secondTxBroadcast = await limitedProvider.broadcastTransaction(
      signedTx[1],
      false
    );
    if (!secondTxBroadcast || !secondTxBroadcast.success) {
      throw new Error("Second transaction broadcast failed.");
    }

    return { success: true };
  } catch (error) {
    console.error("Contract interaction failed:", error);
    return { success: false, message: error };
  }
}

// Example usage:
async function main() {
  const walletWif = "your-wallet-private-key-in-wif-format"; // Replace with your WIF private key
  const walletGet = Wallet.fromWif(walletWif, network); // Import wallet using WIF format
  const contractAddress = "your-contract-address"; // Replace with your contract's address

  const utxos = await provider.utxoManager.getUTXOs({
    address: walletGet.p2tr,
  });

  const result = await interactWithContract(walletGet, contractAddress, utxos);
  if (result.success) {
    console.log("Contract interaction successful.");
  } else {
    console.error("Interaction failed:", result.message);
  }
}

main();