nodejs ping pong cli

cli.ts

import z from 'zod';

function arg(name: string, fallback?: string) {
	const i = process.argv.indexOf(`--${name}`);
	return i > -1 ? process.argv[i + 1] : fallback;
}

function pong(data: any) {
	process.stdout.write(JSON.stringify(data) + '\n');
}

async function ping<T extends z.ZodObject<any, any, any>>(
	commandName: string,
	schema: T,
	generator: (input: z.input<T>) => AsyncGenerator<any, void, unknown>
) {
	const [, , command, ...options] = process.argv;
	if (command === commandName) {
		const args: Record<string, string> = {};
		for (let i = 0; i < options.length; i++) {
			const arg = options[i];
			if (arg.startsWith('--')) {
				const key = arg.slice(2);
				const value = options[i + 1];
				args[key] = value;
				i++;
			}
		}
		for await (const event of generator(schema.parse(args))) {
			pong(event);
		}
	}
}

ping(
	'repeat',
	z.object({
		max: z.coerce.number().min(1),
		delay: z.coerce.number().min(0),
	}),
	async function* ({ max, delay }) {
		let count = 0;

		while (count < max) {
			await new Promise((resolve) => setTimeout(resolve, delay));
			count++;
			yield { count };
		}

		pong({ done: true });
	}
);

ping(
	'countdown',
	z.object({
		start: z.coerce.number().min(0),
		delay: z.coerce.number().min(0),
	}),
	async function* ({ start, delay }) {
		const surprise = arg('surprise', 'false');
		if (surprise === 'true') {
			throw new Error('Surprise error!');
		}
		let count = start;

		while (count > 0) {
			await new Promise((resolve) => setTimeout(resolve, delay));
			count--;
			yield { count };
		}

		pong({ done: true });
	}
);

// Usage:
// node pintg-pong-cli.js repeat --max 5 --delay 1000
// node ping-pong-cli.js countdown --start 5 --delay 1000