# A Complete Example

Below is a complete example using \`hardhat.js for onchain interaction, and node-fetch for the pathfinder API query.

```javascript
require("@nomiclabs/hardhat-ethers");
const { assert } = require("console");
const fs = require("fs")
const fetch = (...args) => import('node-fetch').then(({ default: fetch }) => fetch(...args));

async function main() {

    const ONE_ETH = ethers.constants.WeiPerEther;

    // First, we query the BrainDex Pathfinder service for a route.

    // Construct pathfinder query data
    const data =
    {
        "chain_id": 1284,
        "amount_in": ONE_ETH._hex,
        "token_in": "0xAcc15dC74880C9944775448304B263D191c6077F",
        "token_out": "0x818ec0a7fe18ff94269904fced6ae3dae6d6dc0b",
        "max_hops": 3,
        "min_splits": 0,    
        "max_splits": 3,
        "count": 5
    }

    // Make the route request
    const response = await fetch('https://api.braindex.io/app/myAppId', {
        method: 'post',
        body: JSON.stringify(data),
        headers: { 'Content-Type': 'application/json' }
    });

    // Parse our response
    const res = await response.json(); // parses JSON response into native JavaScript objects

    console.log(res.amount_out);

    // Now that we have our route response, we can query the chain to confirm our price.

    // Load the contract ABI interface
    const bdexAbiFile = fs.readFileSync('./abi/brainDexRouterAbi.json', "utf-8")
    const bdexAbi = JSON.parse(bdexAbiFile);

    // Get onchain signer
    const [signer] = await ethers.getSigners();

    // Initialize the router contract
    const BrainDexRouter = "0xe2eA8cb03481B83402e6159cf95A63A934255C6b";
    const router = new ethers.Contract(BrainDexRouter, bdexAbi, signer);

    const amtOutQuote = ethers.BigNumber.from(res.amount_out);

    // Confirm our price quote by passing the swap_paths 
    // field of the pathfinder response to the contract.
    const priceConfirm = await router.getMultiSwapAmountOut(res.swap_paths);

    // Note that there may be some small differences due to price movements 
    // between query and confirmation times.
    assert(amtOutQuote.eq(priceConfirm), "Price mismatch!");

    // We have found that the gas estimate can be underneath of what is expected, 
    // so we buffer by 1.2x

    const gasEstimate = await router.estimateGas.multiSwapTokensForTokens(
        data.token_in,
        data.token_out,
        signer.address,
        ONE_ETH,
        ethers.BigNumber.from(1), // Must be at least 1.
        ethers.BigNumber.from(1775120065),
        res.swap_paths,
    )

    const bufferedGasEstimate = gasEstimate.mul(12).div(10);

    // Perform a swap. Note that this requires that the signer have approved 
    // the contract beforehand.
    const tx = await router.multiSwapTokensForTokens(
        data.token_in,
        data.token_out,
        signer.address,
        ONE_ETH,
        ethers.BigNumber.from(1), // In production, this value should be propagated by user slippage settings. Must be at least 1.
        ethers.BigNumber.from(1775120065),
        res.swap_paths,
        {
            gasLimit: bufferedGasEstimate,
        }
    )

    console.log(tx.hash);
}

main().catch((error) => {
    console.error(error);
    process.exitCode = 1;
});
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://braindex.gitbook.io/braindex-documentation/developer-documentation/a-complete-example.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.