# Call - code sample

{% hint style="info" %}
The full repository for this code sample can be found here <https://github.com/SigmaGmbH/swisstronik-tutorials/tree/main/ERC20_interaction>
{% endhint %}

### Making Calls in Swisstronik

Let's implement a function called `sendShieldedQuery` to make a call to a smart contract, using SwisstronikJS.

{% hint style="info" %}
For this example, we have deployed an ERC20 token at `0x7D804090e7a1FF0709d743d115bccE6757Bbe208`. Let's create the code to make a call to the function `totalSupply()`
{% endhint %}

1. Open your Hardhat project and run  `npm i @swisstronik/utils` it from the main directory.

{% hint style="warning" %}
NOTE: If you don't know how to set up a Hardhat project, please review the [Contract deployment - Hardhat ](https://docs.swisstronik.com/swisstronik-docs/development/guides/contract-deployment-hardhat/1.-setting-up-the-hardhat-environment)
{% endhint %}

2. Create a file `totalSupply.js` within the scripts folder in your Hardhat project, this file will contain the code to run the call to get the total supply.
3. Import SwisstronikJS & Hardhat in the `totalSupply.js` script

{% code lineNumbers="true" %}

```javascript
const hre = require("hardhat");
const { encryptDataField, decryptNodeResponse } = require("@swisstronik/utils");
```

{% endcode %}

4. Let's add the code to implement a function called `sendShieldedQuery` to use `encryptDataField()` and `decryptNodeResponse()`

{% hint style="success" %}
You can reuse this `sendShieldedQuery` code snippet to make calls to any smart contracts in the Swisstronik blockchain.
{% endhint %}

<pre class="language-javascript" data-line-numbers><code class="lang-javascript"><strong>const hre = require("hardhat");
</strong>const { encryptDataField, decryptNodeResponse } = require("@swisstronik/utils");

/**
 * Make a shielded query/call on the Swisstronik blockchain.
 *
 * @param {object} provider - The provider object for making the call.
 * @param {string} destination - The contract address to call.
 * @param {string} data - Encoded data for the function call.
 *
 * @returns {Uint8Array} - Encrypted response from the blockchain.
 */
const sendShieldedQuery = async (provider, destination, data) => {
  // Obtain the RPC link from the network configuration
  const rpcLink = hre.network.config.url;

  // Encrypt the call data using SwisstronikJS's encryption function
  const [encryptedData, usedEncryptionKey] = await encryptDataField(rpcLink, data);

  // Execute the query/call using the provider
  const response = await provider.call({
    to: destination,
    data: encryptedData,
  });

  // Decrypt the response using SwisstronikJS's decryption function
  return await decryptNodeResponse(rpcLink, response, usedEncryptionKey);
};
</code></pre>

5. Let's add the `main` function to use the `sendShieldedQuery` to make a call to the `function totalSupply() external view returns (uint256)` in the ERC20 smart contract.

{% hint style="success" %}
You can reuse this script to make calls in Swisstronik (make sure you are calling a reading-only function) and don't forget to replace the variables marked with the `replace_` prefix with your own values in the `main` function
{% endhint %}

{% code lineNumbers="true" %}

```javascript
const hre = require("hardhat");
const { encryptDataField, decryptNodeResponse } = require("@swisstronik/utils");

/**
 * Make a shielded query/call on the Swisstronik blockchain.
 *
 * @param {object} provider - The provider object for making the call.
 * @param {string} destination - The contract address to call.
 * @param {string} data - Encoded data for the function call.
 *
 * @returns {Uint8Array} - Encrypted response from the blockchain.
 */
const sendShieldedQuery = async (provider, destination, data) => {
  // Obtain the RPC link from the network configuration
  const rpcLink = hre.network.config.url;

  // Encrypt the call data using SwisstronikJS's encryption function
  const [encryptedData, usedEncryptionKey] = await encryptDataField(rpcLink, data);

  // Execute the query/call using the provider
  const response = await provider.call({
    to: destination,
    data: encryptedData,
  });

  // Decrypt the response using SwisstronikJS's decryption function
  return await decryptNodeResponse(rpcLink, response, usedEncryptionKey);
};
// Main function to interact with the contract and retrieve data
async function main() {
  // Address of the deployed contract
  const replace_contractAddress = "0x7D804090e7a1FF0709d743d115bccE6757Bbe208";

  // Get the signer (your account)
  const [signer] = await hre.ethers.getSigners();

  // Create a contract instance
  const replace_contractFactory = await hre.ethers.getContractFactory("TestToken");
  const contract = replace_contractFactory.attach(replace_contractAddress);

  // Perform a shielded query to retrieve data from the contract
  const replace_functionName = "totalSupply";
  const replace_functionArgs = ""; // Replace with specific arguments if required
  const responseMessage = await sendShieldedQuery(signer.provider, replace_contractAddress, contract.interface.encodeFunctionData(replace_functionName, replace_functionArgs));

  // Decode the Uint8Array response into a readable string
  console.log("Decoded response:", contract.interface.decodeFunctionResult(replace_functionName, responseMessage)[0]);
}

// Using async/await pattern to handle errors properly
main().catch((error) => {
  console.error(error);
  process.exitCode = 1;
});
```

{% endcode %}

6. Run `npx hardhat run scripts/totalSupply.js --network swisstronik`
7. You should see the decoded number printed in your console 🎉