> For the complete documentation index, see [llms.txt](https://abc.bharatblockchain.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://abc.bharatblockchain.io/hedera/tutorials/smartcontract-service/revoke-document.md).

# Revoke Document

### Summary:

The script executes a transaction on a smart contract deployed on the Hedera network to revoke a seal using a specific hash. It showcases how to send transactions to the smart contract and process the transaction receipts and event logs emitted by the contract.

### 1. Imports and Environment Setup:

```javascript
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`) and the `dotenv` module to load environment variables from a `.env` file located in the `SmartContract_Service` directory.
* It imports the `Web3` library to decode event logs emitted by the smart contract.

### 2. Environment Variables Retrieval and Validation:

```javascript
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");
}
```

* It 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:

```javascript
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:

```javascript
async function main() {
    const contractExecTx = await new ContractExecuteTransaction()
        .setContractId(contractId)
        .setGas(100000)
        .setFunction("revokeSeal", 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("DocumentRevoced", logStringHex, logTopics.slice(1));
    });

    process.exit();
}
```

* It defines the `main()` function, which is the entry point of the script.
* It creates a transaction to execute the `revokeSeal` function of the smart contract with the provided hash parameter.
* The transaction is submitted to the Hedera network, and the result (transaction receipt) is retrieved.
* Event logs emitted by the smart contract during the transaction execution are decoded using the `decodeEvent()` function.

### 5. Event Decoding Function:

```javascript
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;
}
```

* It defines the `decodeEvent()` function to decode event logs emitted by the smart contract using the contract's ABI definition.

### 6. Execution:

```javascript
main();
```

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