Integrate Across Swap API

npm init -y
npm install viem

touch bridge.ts

import {
  createWalletClient,
  createPublicClient,
  http,
  parseUnits,
} from "viem";
import { arbitrum } from "viem/chains";
import { privateKeyToAccount } from "viem/accounts";

const BASE_URL = "https://app.across.to/api";

// ── Helpers ──────────────────────────────────────────────

async function getChains() {
  const res = await fetch(`${BASE_URL}/swap/chains`);
  return res.json();
}

async function getTokens(chainId: number) {
  const res = await fetch(`${BASE_URL}/swap/tokens?chainId=${chainId}`);
  return res.json();
}

function findChain(chains: any[], name: string) {
  const chain = chains.find(
    (c: any) => c.name.toLowerCase() === name.toLowerCase()
  );
  if (!chain) throw new Error(`Chain "${name}" not found`);
  return chain;
}

function findToken(tokens: any[], symbol: string) {
  const token = tokens.find(
    (t: any) => t.symbol.toUpperCase() === symbol.toUpperCase()
  );
  if (!token) throw new Error(`Token "${symbol}" not found`);
  return token;
}

// ── Main ─────────────────────────────────────────────────

async function main() {
  // Setup wallet
  const account = privateKeyToAccount(
    process.env.PRIVATE_KEY as `0x${string}`
  );
  const walletClient = createWalletClient({
    account,
    chain: arbitrum,
    transport: http(),
  });
  const publicClient = createPublicClient({
    chain: arbitrum,
    transport: http(),
  });

  console.log(`Wallet: ${account.address}\n`);

  // ── Step 1: Discover chains ──────────────────────────
  console.log("Step 1: Discovering chains...");
  const chains = await getChains();
  const origin = findChain(chains, "Arbitrum");
  const destination = findChain(chains, "Base");
  console.log(`  Origin:      ${origin.name} (${origin.chainId})`);
  console.log(`  Destination: ${destination.name} (${destination.chainId})\n`);

  // ── Step 2: Look up tokens ───────────────────────────
  console.log("Step 2: Looking up USDC on both chains...");
  const originTokens = await getTokens(origin.chainId);
  const destTokens = await getTokens(destination.chainId);
  const inputToken = findToken(originTokens, "USDC");
  const outputToken = findToken(destTokens, "USDC");
  console.log(`  Input:  ${inputToken.symbol} (${inputToken.address}) — ${inputToken.decimals} decimals`);
  console.log(`  Output: ${outputToken.symbol} (${outputToken.address}) — ${outputToken.decimals} decimals\n`);

  // ── Step 3: Get a quote ──────────────────────────────
  console.log("Step 3: Fetching quote for 1 USDC...");
  const amount = parseUnits("1", inputToken.decimals).toString();

  const searchParams = new URLSearchParams({
    tradeType: "minOutput",
    originChainId: origin.chainId.toString(),
    destinationChainId: destination.chainId.toString(),
    inputToken: inputToken.address,
    outputToken: outputToken.address,
    amount,
    depositor: account.address,
  });

  const quoteRes = await fetch(`${BASE_URL}/swap/approval?${searchParams}`);
  const quote = await quoteRes.json();

  if (!quote.swapTx) {
    throw new Error(`Quote failed: ${JSON.stringify(quote, null, 2)}`);
  }

  console.log(`  Cross-swap type:   ${quote.crossSwapType}`);
  console.log(`  Expected fill:     ${quote.expectedFillTime}s`);
  console.log(`  Approvals needed:  ${quote.approvalTxns?.length ?? 0}`);
  console.log(`  Simulation passed: ${quote.swapTx.simulationSuccess}\n`);

  // ── Step 4: Execute approvals ────────────────────────
  if (quote.approvalTxns?.length) {
    console.log("Step 4: Executing approvals...");
    for (const approvalTx of quote.approvalTxns) {
      const hash = await walletClient.sendTransaction({
        to: approvalTx.to as `0x${string}`,
        data: approvalTx.data as `0x${string}`,
      });
      console.log(`  Approval tx: ${hash}`);
      await publicClient.waitForTransactionReceipt({ hash });
      console.log(`  Confirmed.`);
    }
    console.log();
  } else {
    console.log("Step 4: No approvals needed — skipping.\n");
  }

  // ── Step 5: Execute bridge ───────────────────────────
  console.log("Step 5: Sending bridge transaction...");
  const hash = await walletClient.sendTransaction({
    to: quote.swapTx.to as `0x${string}`,
    data: quote.swapTx.data as `0x${string}`,
    value: quote.swapTx.value ? BigInt(quote.swapTx.value) : 0n,
    gas: quote.swapTx.gas ? BigInt(quote.swapTx.gas) : undefined,
  });
  console.log(`  Bridge tx: ${hash}`);

  const receipt = await publicClient.waitForTransactionReceipt({ hash });
  console.log(`  Confirmed in block ${receipt.blockNumber}`);
  console.log(`\n  View on Arbiscan: ${origin.explorerUrl}/tx/${hash}`);
  console.log(`  Your USDC will arrive on Base in ~${quote.expectedFillTime} seconds.`);
}

main().catch(console.error);

PRIVATE_KEY=0xYOUR_PRIVATE_KEY npx tsx bridge.ts

Wallet: 0xYourAddress

Step 1: Discovering chains...
  Origin:      Arbitrum (42161)
  Destination: Base (8453)

Step 2: Looking up USDC on both chains...
  Input:  USDC (0xaf88d065e77c8cC2239327C5EDb3A432268e5831) — 6 decimals
  Output: USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) — 6 decimals

Step 3: Fetching quote for 1 USDC...
  Cross-swap type:   bridgeableToBridgeable
  Expected fill:     2s
  Approvals needed:  1
  Simulation passed: true

Step 4: Executing approvals...
  Approval tx: 0xabc123...
  Confirmed.

Step 5: Sending bridge transaction...
  Bridge tx: 0xdef456...
  Confirmed in block 284719304

  View on Arbiscan: https://arbiscan.io/tx/0xdef456...
  Your USDC will arrive on Base in ~2 seconds.