OKX DEX API Guide: Building a Solana Token Swap Interface

Ready to integrate DEX aggregation into your Solana DApp? This tutorial shows you how to interact with the OKX DEX API to perform token swaps on the Solana blockchain. Your implementation will use Web3.js and the OKX DEX API to create robust handling of quotes and swap execution. By default, this implementation demonstrates:

• Single-chain swaps: SOL to USDC on Solana
• Cross-chain capabilities: SOL to MATIC (Polygon)

DEX API Utility File Overview

This tutorial focuses on implementing dexUtils.js, a utility file that contains all the necessary functions for interacting with the OKX DEX API on Solana. This file handles:

• Network and token configurations
• Header construction
• API endpoint and call construction
• Quote retrieval
• Single-chain swaps
• Cross-chain quotes

Prerequisites

Before beginning, you need:

• Node.js installed (v16 or later)
• Basic knowledge of Solana development
• A Solana wallet address and private key
• OKX API credentials (API Key, Secret Key, and Passphrase) from the OKX Developer Portal
• A Project ID from the OKX Developer Portal
• Git installed on your machine
• RPC API credentials (API Key, dedicated Solana endpoint) from a node provider like like Quicknode

Setup

You have two options to get started:

Option 1: Local Development

1. Clone the repository and switch to the Solana branch:

git clone https://github.com/Julian-dev28/okx-os-evm-swap-app.git
cd okx-os-evm-swap-app
git checkout solana-cross-chain-swap

1. Install the dependencies:

npm install

1. Set up your environment variables:

REACT_APP_API_KEY=your_api_key
REACT_APP_SECRET_KEY=your_secret_key
REACT_APP_API_PASSPHRASE=your_passphrase
REACT_APP_PROJECT_ID=your_project_id
REACT_APP_USER_ADDRESS=your_wallet_address
REACT_APP_PRIVATE_KEY=your_private_key

Option 2: Using Replit

1. Fork the Replit project:
   OKX Solana Swap App

2. Add your environment variables in the Replit Secrets tab (located in the Tools panel):

   • Click on "Secrets"
   • Add each environment variable listed above

3. Click "Run" to start your development environment

Initial Configuration

Let's set up our configuration for interacting with Solana:

import { Connection } from "@solana/web3.js";
import base58 from "bs58";
import cryptoJS from "crypto-js";

// Constants for tokens and chain
export const NATIVE_SOL = "11111111111111111111111111111111";
export const WRAPPED_SOL = "So11111111111111111111111111111111111111112";
export const USDC_SOL = "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v";
export const SOLANA_CHAIN_ID = "501";

// Initialize Solana connection
export const connection = new Connection("https://mainnet.helius-rpc.com/?api-key=<API_KEY>", {
    confirmTransactionInitialTimeout: 5000,
    wsEndpoint: "wss://mainnet.helius-rpc.com/?api-key=<API_KEY>",
});

// Environment variables for API authentication
const apiKey = process.env.REACT_APP_API_KEY;
const secretKey = process.env.REACT_APP_SECRET_KEY;
const apiPassphrase = process.env.REACT_APP_API_PASSPHRASE;
const projectId = process.env.REACT_APP_PROJECT_ID;

// Base URL for API requests
const apiBaseUrl = "https://www.okx.com/api/v5/dex";

Getting Swap Quotes

Before executing a swap, we need to get a quote. Here's how to implement the quote functionality:

/**
 * Gets swap data and optimal route from the OKX DEX API
 * Note: Requires API credentials from OKX Developer Portal
 * 
 * @param {Object} params 
 * @param {string} params.chainId - "501" for Solana
 * @param {string} params.amount - Amount in lamports (1 SOL = 1e9 lamports)
 * @param {string} params.fromTokenAddress - Source token (e.g., NATIVE_SOL)
 * @param {string} params.toTokenAddress - Destination token (e.g., USDC_SOL)
 * @param {string} params.slippage - Slippage tolerance ("0.5" for 0.5%)
 * @param {string} params.userWalletAddress - Solana wallet address
 * @returns {Promise<Object>} Contains routerResult.toTokenAmount and transaction data
 */
export async function getSingleChainSwap(params) {
    if (!apiKey || !secretKey || !apiPassphrase || !projectId) {
        throw new Error("Missing API credentials");
    }

    const timestamp = new Date().toISOString();
    const requestPath = "/api/v5/dex/aggregator/swap";
    const queryString = "?" + new URLSearchParams(params).toString();
    const headers = getHeaders(timestamp, "GET", requestPath, queryString);

    console.log("Requesting swap quote with params:", params);

    const response = await fetch(
        `https://www.okx.com${requestPath}${queryString}`,
        { method: "GET", headers }
    );

    const data = await response.json();
    if (data.code !== "0") {
        throw new Error(`API Error: ${data.msg}`);
    }

    if (!data.data?.[0]?.routerResult?.toTokenAmount) {
        throw new Error("Invalid or missing output amount");
    }

    return data.data[0];
}

Executing Transactions

Here's the implementation for executing swap transactions on Solana:

/**
 * Executes a Solana transaction with retry logic and compute budget
 * @param {Object} txData - Transaction data from the API
 * @returns {Promise<Object>} Transaction result with explorer URL
 */
export async function executeTransaction(txData) {
    if (!userPrivateKey) {
        throw new Error("Private key not found");
    }

    try {
        // Get recent blockhash for transaction validity
        const recentBlockHash = await connection.getLatestBlockhash();
        const decodedTransaction = base58.decode(txData.data);

        // Create transaction object
        const tx = solanaWeb3.Transaction.from(decodedTransaction);
        tx.recentBlockhash = recentBlockHash.blockhash;

        // Create and add keypair for signing
        const feePayer = solanaWeb3.Keypair.fromSecretKey(
            base58.decode(userPrivateKey)
        );
        tx.partialSign(feePayer);

        // Send transaction with retry options
        const txId = await connection.sendRawTransaction(tx.serialize(), {
            skipPreflight: false,
            maxRetries: 5
        });

        // Wait for confirmation
        const confirmation = await connection.confirmTransaction({
            signature: txId,
            blockhash: recentBlockHash.blockhash,
            lastValidBlockHeight: recentBlockHash.lastValidBlockHeight
        }, 'confirmed');

        return {
            success: true,
            transactionId: txId,
            explorerUrl: `https://solscan.io/tx/${txId}`,
            confirmation
        };
    } catch (error) {
        console.error("Transaction failed:", error);
        throw error;
    }
}

React Component Implementation

The SolanaSwapTransaction component demonstrates how to implement the DEX API calls in a React interface:

git clone https://github.com/Julian-dev28/okx-os-evm-swap-app.git
cd okx-os-evm-swap-app
git checkout solana-cross-chain-swap

Additional Resources

• OKX DEX API Documentation
• Solana Documentation
• Source Code Repository

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Found this helpful? Don't forget to check out the boilerplate code and documentation linked above. Join the OKX OS Community to connect with other developers, and follow Julian on Twitter for more Solana development content!

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