Example flow of sign in with Ethereum

signin-with-ethereum.mjs

import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { assetChainTestnet } from "viem/chains";
import dotenv from "dotenv";
import readline from 'readline';
import { stdin, stderr, exit, env } from 'process';
dotenv.config();

// Create readline interface for user input
const rl = readline.createInterface({
	input: stdin,
	output: stderr // Use stderr for prompts so stdout only contains the signature
});

// Function to prompt for user input
function prompt(question) {
	return new Promise((resolve) => {
		rl.question(question, (answer) => {
			resolve(answer);
		});
	});
}

async function main() {
	try {
		// Prompt for nonce value
		const stringFromBackendApi = await prompt("Enter the nonce value: ");
		const privateKey = env.PK;

		if (!stringFromBackendApi) {
			console.error("Error: Nonce value is required");
			rl.close();
			exit(1);
		}

		const account = privateKeyToAccount(privateKey);

		const client = createWalletClient({
			transport: http(),
			chain: assetChainTestnet,
			account,
		});

		const signature = await client.signMessage({
			account,
			message: `Sign in to Asset Chain Liquidity: ${stringFromBackendApi}`,
		});

		// Close readline before outputting signature
		rl.close();
		
		// Only output the signature to stdout (for piping)
		console.log(signature);
		
		// Output additional info to stderr
		console.error("\nSignature has been generated and copied to clipboard if piped to pbcopy.");
		
		return signature;
	} catch (error) {
		console.error("Error:", error.message);
		rl.close();
		exit(1);
	}
}

main();

// node sign-login.mjs --nonce=string | pbcopy