Seal Document

Summary:

The script interacts with a deployed smart contract on the Hedera network by executing a function call and decoding the emitted events. It showcases how to send transactions to the smart contract and parse the resulting event data.

1. Imports and Environment Setup:

const {
    Client,
    ContractFunctionParameters,
    ContractExecuteTransaction,
    PrivateKey,
} = require("@hashgraph/sdk");
require('dotenv').config({ path: 'SmartContract_Service/.env' });

const Web3 = require('web3');
const web3 = new Web3;
let abi;

• It imports necessary modules from the Hedera JavaScript SDK (@hashgraph/sdk), including Client, ContractFunctionParameters, ContractExecuteTransaction, and PrivateKey.

• It also imports the dotenv module to load environment variables from a .env file located in the SmartContract_Service directory.

• The script imports the Web3 module to interact with the Ethereum-like smart contract and creates a web3 instance.

2. Environment Variables Retrieval and Validation:

const myAccountId = process.env.MY_ACCOUNT_ID;
const myPrivateKey = PrivateKey.fromString(process.env.MY_PRIVATE_KEY);
const contractId = process.env.CONTRACT_ID;
const hash = process.env.HASH;

if (myAccountId == null || myPrivateKey == null) {
    throw new Error("Environment variables myAccountId and myPrivateKey must be present");
}

• The script retrieves the account ID, private key, contract ID, and hash from the .env file.

• It checks whether these variables are present; otherwise, it throws an error.

3. Client Setup:

const client = Client.forTestnet();
client.setOperator(myAccountId, myPrivateKey);

• It creates a client instance for the Hedera testnet and sets the operator account using the user's account ID and private key.

4. Main Function:

async function main() {
    // Transaction to update the contract message
    const contractExecTx = await new ContractExecuteTransaction()
        .setContractId(contractId)
        .setGas(100000)
        .setFunction("seal", new ContractFunctionParameters().addString(hash));

    const submitExecTx = await contractExecTx.execute(client);
    const receipt2 = await submitExecTx.getReceipt(client);

    console.log("The transaction status is " + receipt2.status.toString());

    const record = await submitExecTx.getRecord(client);

    record.contractFunctionResult.logs.forEach(log => {
        let logStringHex = '0x'.concat(Buffer.from(log.data).toString('hex')));
        let logTopics = [];
        log.topics.forEach(topic => {
            logTopics.push('0x'.concat(Buffer.from(topic).toString('hex')));
        });
        decodeEvent("DocumentSealed", logStringHex, logTopics.slice(1));
    });

    process.exit();
}

• The main() function is the entry point of the script.

• It creates a transaction to execute a function (seal) on the smart contract with the given contract ID and hash parameter.

• The transaction is executed on the Hedera network, and its receipt is retrieved to confirm the execution status.

• Events emitted by the smart contract function call are parsed and decoded using the decodeEvent function.

5. Event Decoding Function:

function decodeEvent(eventName, log, topics) {
    const abiFile = require("../artifacts/contracts/eseal.sol/Eseal.json");
    abi = abiFile.abi;
    const eventAbi = abi.find(event => (event.name === eventName && event.type === "event"));
    const decodedLog = web3.eth.abi.decodeLog(eventAbi.inputs, log, topics);
    console.log(decodedLog);
    return decodedLog;
}

• The decodeEvent function decodes the event contents using the ABI definition of the event.

• It loads the ABI file of the smart contract and finds the event ABI based on the event name.

• The event data is decoded using web3.eth.abi.decodeLog.

6. Execution:

main();

• This line calls the main() function to start the execution of the script.