Swap API › Classic Swap

Let's go over an example of how to perform a token swap using the 1inch Classic Swap API.

Before You Start

You must have a valid 1inch API Key. You can get one from the 1inch Business.
Your wallet must have:
- USDC (or the token you're swapping) on Base
- ETH on Base to pay gas fees

Typescript Program

Loads configuration variables (private key, wallet address, RPC URL, and 1inch Business Portal API key) from the environment or a local .env file
Connects to the Base chain using viem
Checks the allowance of the token being swapped and increases the approval if necessary
Uses the /swap endpoint to construct the swap transaction
It signs and broadcasts the transaction

Dependencies

node v18.17.1
npm v10.9.2

Bash
1
npm install dotenv ethers

Example

TypeScript
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import dotenv from 'dotenv';
import { Wallet, JsonRpcProvider, Contract } from 'ethers';

dotenv.config();

const requiredEnvVars = ['PRIVATE_KEY', 'API_KEY', 'RPC_URL'];
for (const key of requiredEnvVars) {
  if (!process.env[key]) {
    console.error(`Missing required environment variable: ${key}`);
    process.exit(1);
  }
}

const AGGREGATION_ROUTER_V6 = '0x111111125421ca6dc452d289314280a0f8842a65';
const usdcBase = '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913';
const wethBase = '0x4200000000000000000000000000000000000006';
const BASE_CHAIN_ID = 8453;
const baseUrl = `https://api.1inch.com/swap/v6.1/${BASE_CHAIN_ID}`;

const config = {
  aggregationRouter: AGGREGATION_ROUTER_V6,

  privateKey: process.env.PRIVATE_KEY!,
  apiKey: process.env.API_KEY!,
  rpcUrl: process.env.RPC_URL!,

  srcTokenAddress: usdcBase,
  dstTokenAddress: wethBase,
  amountToSwap: '100000',
  slippage: 1, // 1%
};

const erc20ABI = [
  {
    constant: true,
    inputs: [
      { name: 'owner', type: 'address' },
      { name: 'spender', type: 'address' },
    ],
    name: 'allowance',
    outputs: [{ name: '', type: 'uint256' }],
    payable: false,
    stateMutability: 'view',
    type: 'function',
  },
  {
    constant: false,
    inputs: [
      { name: 'spender', type: 'address' },
      { name: 'amount', type: 'uint256' },
    ],
    name: 'approve',
    outputs: [{ name: '', type: 'bool' }],
    payable: false,
    stateMutability: 'nonpayable',
    type: 'function',
  },
];

type TransactionPayload = {
  to: string;
  data: string;
  value: bigint;
};

type TxResponse = {
  tx: TransactionPayload;
};

const provider = new JsonRpcProvider(config.rpcUrl);
const wallet = new Wallet(config.privateKey, provider);

function buildQueryURL(path: string, params: Record<string, string>): string {
  const url = new URL(baseUrl + path);
  url.search = new URLSearchParams(params).toString();
  return url.toString();
}

async function call1inchAPI<T>(
  endpointPath: string,
  queryParams: Record<string, string>,
): Promise<T> {
  const url = buildQueryURL(endpointPath, queryParams);

  const response = await fetch(url, {
    method: 'GET',
    headers: {
      Accept: 'application/json',
      Authorization: `Bearer ${config.apiKey}`,
    },
  });

  if (!response.ok) {
    const body = await response.text();
    throw new Error(`1inch API returned status ${response.status}: ${body}`);
  }

  return (await response.json()) as T;
}

async function signAndSendTransaction(tx: TransactionPayload): Promise<string> {
  try {
    const txResponse = await wallet.sendTransaction({
      to: tx.to,
      data: tx.data,
      value: tx.value,
    });

    return txResponse.hash;
  } catch (err) {
    console.error('Transaction signing or broadcasting failed');
    console.error('Transaction data:', tx);
    throw err;
  }
}

async function checkAllowance(
  tokenAddress: string,
  spenderAddress: string,
): Promise<bigint> {
  console.log('Checking token allowance...');

  const tokenContract = new Contract(tokenAddress, erc20ABI, provider);
  const allowance = await tokenContract.allowance(
    wallet.address,
    spenderAddress,
  );

  console.log('Allowance:', allowance.toString());

  return allowance;
}

async function approveIfNeeded(
  tokenAddress: string,
  spenderAddress: string,
  requiredAmount: bigint,
): Promise<void> {
  const allowance = await checkAllowance(tokenAddress, spenderAddress);

  if (allowance >= requiredAmount) {
    console.log('Allowance is sufficient for the swap.');
    return;
  }

  console.log('Insufficient allowance. Approving exact amount needed...');

  const tokenContract = new Contract(tokenAddress, erc20ABI, wallet);

  const tx = await tokenContract.approve(spenderAddress, requiredAmount);

  console.log('Approval transaction sent. Hash:', tx.hash);
  console.log('Waiting for confirmation...');

  await tx.wait();

  console.log('Approval confirmed!');
}

async function performSwap(): Promise<void> {
  const swapParams = {
    src: config.srcTokenAddress,
    dst: config.dstTokenAddress,
    amount: config.amountToSwap,
    from: wallet.address.toLowerCase(),
    slippage: config.slippage.toString(),
    disableEstimate: 'false',
    allowPartialFill: 'false',
  };

  console.log('Fetching swap transaction...');
  const swapTx = await call1inchAPI<TxResponse>('/swap', swapParams);

  console.log('Swap transaction:', swapTx.tx);

  const txHash = await signAndSendTransaction(swapTx.tx);
  console.log('Swap transaction sent. Hash:', txHash);
}

async function main() {
  try {
    await approveIfNeeded(
      config.srcTokenAddress,
      config.aggregationRouter,
      BigInt(config.amountToSwap),
    );
    await performSwap();
  } catch (err) {
    console.error('Error:', (err as any)?.response?.data || err);
  }
}

main().catch((err) => {
  console.error('Unhandled error in main:', err);
  process.exit(1);
});

Go Program

Uses the official 1inch Go SDK to perform a token swap on the Base chain:

Loads configuration variables (private key, RPC URL, and 1inch Business Portal API key) from the environment
Connects to the Base chain using the SDK
Uses the GetApproveAllowance function in the SDK to call the /approve/allowance REST endpoint to check if your wallet has granted the proper USDC allowance to the 1inch router
If the allowance is insufficient, it uses the GetApproveTransaction function in the SDK to call the /approve/transaction REST endpoint to construct and send an approval transaction
Then, it uses the GetSwap function in the SDK to call the /swap REST endpoint to construct the swap transaction
It signs and broadcasts these transactions using the SDK client

Dependencies

go v1.24.5

Bash
1
2
go get github.com/1inch/1inch-sdk-go/sdk-clients/aggregation
go get github.com/ethereum/go-ethereum

Code

GO
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package main

import (
    "context"
    "fmt"
    "log"
    "math/big"
    "os"
    "time"

    "github.com/1inch/1inch-sdk-go/constants"
    "github.com/1inch/1inch-sdk-go/sdk-clients/aggregation"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/hexutil"
)

var (
    privateKey     = os.Getenv("PRIVATE_KEY")
    nodeUrl        = os.Getenv("RPC_URL")
    devPortalToken = os.Getenv("DEV_PORTAL_API_KEY")
)

const (
    UsdcBase   = "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
    WethBase   = "0x4200000000000000000000000000000000000006"
    amountUsdc = "100000" // 0.1 USDC (6 decimals)
)

func main() {
    config, err := aggregation.NewConfiguration(aggregation.ConfigurationParams{
        NodeUrl:    nodeUrl,
        PrivateKey: privateKey,
        ChainId:    constants.BaseChainId,
        ApiUrl:     "https://api.1inch.com",
        ApiKey:     devPortalToken,
    })
    if err != nil {
        log.Fatalf("Failed to create configuration: %v\n", err)
    }
    client, err := aggregation.NewClient(config)
    if err != nil {
        log.Fatalf("Failed to create client: %v\n", err)
    }
    ctx := context.Background()

    walletAddr := client.Wallet.Address().Hex()

    // Step 1: Check Allowance
    allowanceData, err := client.GetApproveAllowance(ctx, aggregation.GetAllowanceParams{
        TokenAddress:  UsdcBase,
        WalletAddress: walletAddr,
    })
    if err != nil {
        log.Fatalf("Failed to get allowance: %v\n", err)
    }
    allowance := new(big.Int)
    allowance.SetString(allowanceData.Allowance, 10)

    amountToSwap := new(big.Int)
    amountToSwap.SetString(amountUsdc, 10)

    // Step 2: Approve if needed
    if allowance.Cmp(amountToSwap) < 0 {
        fmt.Println("Insufficient allowance. Approving...")
        approveData, err := client.GetApproveTransaction(ctx, aggregation.GetApproveParams{
            TokenAddress: UsdcBase,
            Amount:       amountUsdc,
        })
        if err != nil {
            log.Fatalf("Failed to get approve data: %v\n", err)
        }
        data, err := hexutil.Decode(approveData.Data)
        if err != nil {
            log.Fatalf("Failed to decode approve data: %v\n", err)
        }
        to := common.HexToAddress(approveData.To)

        tx, err := client.TxBuilder.New().SetData(data).SetTo(&to).Build(ctx)
        if err != nil {
            log.Fatalf("Failed to build approve transaction: %v\n", err)
        }
        signedTx, err := client.Wallet.Sign(tx)
        if err != nil {
            log.Fatalf("Failed to sign approve transaction: %v\n", err)
        }
        err = client.Wallet.BroadcastTransaction(ctx, signedTx)
        if err != nil {
            log.Fatalf("Failed to broadcast approve transaction: %v\n", err)
        }

        fmt.Printf("Approve transaction sent: https://basescan.org/tx/%s\n", signedTx.Hash().Hex())

        // Wait for approval to be mined
        for {
            receipt, _ := client.Wallet.TransactionReceipt(ctx, signedTx.Hash())
            if receipt != nil {
                fmt.Println("Approve transaction confirmed.")
                break
            }
            time.Sleep(2 * time.Second)
        }
    } else {
        fmt.Println("Sufficient allowance already present.")
    }

    // Step 3: Perform Swap
    swapData, err := client.GetSwap(ctx, aggregation.GetSwapParams{
        Src:      UsdcBase,
        Dst:      WethBase,
        Amount:   amountUsdc,
        From:     walletAddr,
        Slippage: 1, // 1% slippage
    })
    if err != nil {
        log.Fatalf("Failed to get swap data: %v\n", err)
    }

    tx, err := client.TxBuilder.New().
        SetData(swapData.TxNormalized.Data).
        SetTo(&swapData.TxNormalized.To).
        SetGas(swapData.TxNormalized.Gas).
        SetValue(swapData.TxNormalized.Value).
        Build(ctx)
    if err != nil {
        log.Fatalf("Failed to build transaction: %v\n", err)
    }
    signedTx, err := client.Wallet.Sign(tx)
    if err != nil {
        log.Fatalf("Failed to sign transaction: %v\n", err)
    }

    err = client.Wallet.BroadcastTransaction(ctx, signedTx)
    if err != nil {
        log.Fatalf("Failed to broadcast transaction: %v\n", err)
    }

    fmt.Printf("Swap transaction sent: https://basescan.org/tx/%s\n", signedTx.Hash().Hex())

    // Wait for swap transaction to be mined
    for {
        receipt, _ := client.Wallet.TransactionReceipt(ctx, signedTx.Hash())
        if receipt != nil {
            fmt.Println("Swap transaction confirmed!")
            break
        }
        time.Sleep(2 * time.Second)
    }
}

Quick start

Before You Start

Typescript Program

Dependencies

Example

Go Program

Dependencies

Code

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