Gasless Token Swap

mkdir carbium-swap-app
cd carbium-swap-app
npm init -y

npm install @solana/web3.js axios bs58 dotenv prompt-sync

# Your Carbium API Key
CARBIUM_API_KEY=your_api_key_here

# Your Solana Wallet Private Key (Base58 string)
# WARNING: Never share this key.
PRIVATE_KEY=your_private_key_base58_string

# RPC URL (Optional, uses public default if not set)
RPC_URL=https://api.mainnet-beta.solana.com

require('dotenv').config();
const axios = require('axios');
const { Connection, Keypair, VersionedTransaction, PublicKey } = require('@solana/web3.js');
const bs58 = require('bs58');
const prompt = require('prompt-sync')();

// Configuration
const CARBIUM_API_URL = 'https://api.carbium.io/api/v1/swap';
const API_KEY = process.env.CARBIUM_API_KEY;
const PRIVATE_KEY = process.env.PRIVATE_KEY;
const RPC_URL = process.env.RPC_URL;
const SOL_MINT = 'So11111111111111111111111111111111111111112'; // Wrapped SOL Mint

async function main() {
    console.log("=== Carbium Gasless Swap CLI ===");

    // 1. Setup Wallet and Connection
    if (!PRIVATE_KEY || !API_KEY) {
        console.error("Error: Missing PRIVATE_KEY or CARBIUM_API_KEY in .env file.");
        return;
    }
    const wallet = Keypair.fromSecretKey(bs58.decode(PRIVATE_KEY));
    const connection = new Connection(RPC_URL, 'confirmed');
    console.log(`Wallet loaded: ${wallet.publicKey.toString()}`);

    // 2. Get User Input (Token CA)
    const tokenCA = prompt('Paste Token Contract Address (CA) to sell: ').trim();
    if (!tokenCA) {
        console.error("Error: Token CA is required.");
        return;
    }

    // 3. Get Amount
    // Note: In a production app, you would fetch the decimals here to convert user input (e.g., "1.5") to raw units.
    // For this sample, we ask for raw units or a simple integer for demonstration.
    const amountStr = prompt('Enter amount to swap (in raw units/lamports): ').trim();
    if (!amountStr) return;

    try {
        console.log(`\nFetching Gasless Swap Transaction...`);
        console.log(`Input: ${tokenCA}`);
        console.log(`Output: SOL (${SOL_MINT})`);

        // 4. Call Carbium API
        // We assume standard parameter naming based on the docs. 
        // Verify these parameters at https://docs.carbium.io/reference/swap
        const response = await axios.get(CARBIUM_API_URL, {
            headers: {
                'x-api-key': API_KEY, // Adjust header name if docs specify otherwise (e.g., 'Authorization')
                'Content-Type': 'application/json'
            },
            params: {
                inputMint: tokenCA,
                outputMint: SOL_MINT,
                amount: amountStr,
                userPublicKey: wallet.publicKey.toString(),
                // 'slippageBps': 50 // Optional: 0.5%
            }
        });

        if (!response.data) {
            throw new Error("No data received from Carbium API");
        }

        // The API returns a base64 encoded transaction string
        const base64Transaction = response.data.transaction || response.data; 
        
        console.log("Transaction received. Deserializing...");

        // 5. Deserialize the Transaction
        const transactionBuffer = Buffer.from(base64Transaction, 'base64');
        const transaction = VersionedTransaction.deserialize(transactionBuffer);

        // 6. Sign the Transaction
        // The transaction returned by Carbium should already have the Fee Payer set (likely Carbium's relayer).
        // You only need to sign as the owner of the source funds.
        transaction.sign([wallet]);

        console.log("Transaction signed. Sending to Solana network...");

        // 7. Send and Confirm
        const signature = await connection.sendTransaction(transaction, {
            maxRetries: 5,
            preflightCommitment: 'processed'
        });

        console.log(`\nSwap Submitted! 🚀`);
        console.log(`Signature: ${signature}`);
        console.log(`Explorer: https://solscan.io/tx/${signature}`);

        const confirmation = await connection.confirmTransaction(signature, 'confirmed');
        if (confirmation.value.err) {
            console.error("Transaction failed:", confirmation.value.err);
        } else {
            console.log("Transaction Confirmed Successfully!");
        }

    } catch (error) {
        console.error("\nExecution Error:");
        if (error.response) {
            console.error(`API Status: ${error.response.status}`);
            console.error(`API Data:`, error.response.data);
        } else {
            console.error(error.message);
        }
    }
}

main();