Read with MoltNode.
Trade with Chord.

import { createPublicClient, createWalletClient, erc20Abi, http, parseUnits } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";

const USDC = "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913";
const ETH = "0x0000000000000000000000000000000000000000"; // the zero address = the chain's native coin

const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`);
const rpc = http("https://moltnode.ag/base"); // reads and broadcasts go through MoltNode
const client = createPublicClient({ chain: base, transport: rpc });
const wallet = createWalletClient({ account, chain: base, transport: rpc });

// 1. Chord: best route + unsigned transaction + a simulation from this wallet
const q = await fetch("https://api.getchord.xyz/v1/meta/quote?" + new URLSearchParams({
  chain: "base", tokenIn: USDC, tokenOut: ETH,
  amount: parseUnits("10", 6).toString(), taker: account.address,
})).then((r) => r.json());
if (!q.tx) throw new Error(q.fallbackReason ?? "no route");

// 2. Approve exactly the amount when the input is an ERC-20
if (q.approval) {
  const hash = await wallet.writeContract({
    address: q.approval.token, abi: erc20Abi, functionName: "approve",
    args: [q.approval.spender, BigInt(q.approval.amount)],
  });
  await client.waitForTransactionReceipt({ hash });
}

// 3. Sign and send the swap through MoltNode
const hash = await wallet.sendTransaction({
  to: q.tx.to, data: q.tx.data, value: BigInt(q.tx.value),
  gas: q.tx.gas ? BigInt(q.tx.gas) : undefined,
});
const receipt = await client.waitForTransactionReceipt({ hash });
console.log(receipt.status, "got at least", q.minAmountOut, "wei of ETH");