Stream OpenAI API Responses

import OpenAI from "openai";

export default {
	async fetch(request, env, ctx): Promise<Response> {
		const openai = new OpenAI({
			apiKey: env.OPENAI_API_KEY,
		});

		// Create a TransformStream to handle streaming data
		let { readable, writable } = new TransformStream();
		let writer = writable.getWriter();
		const textEncoder = new TextEncoder();

		ctx.waitUntil(
			(async () => {
				const stream = await openai.chat.completions.create({
					model: "gpt-4o-mini",
					messages: [{ role: "user", content: "Tell me a story" }],
					stream: true,
				});

				// loop over the data as it is streamed and write to the writable
				for await (const part of stream) {
					writer.write(
						textEncoder.encode(part.choices[0]?.delta?.content || ""),
					);
				}
				writer.close();
			})(),
		);

		// Send the readable back to the browser
		return new Response(readable);
	},
} satisfies ExportedHandler<Env>;

import { Hono } from "hono";
import { streamText } from "hono/streaming";
import OpenAI from "openai";

interface Env {
	OPENAI_API_KEY: string;
}

const app = new Hono<{ Bindings: Env }>();

app.get("*", async (c) => {
	const openai = new OpenAI({
		apiKey: c.env.OPENAI_API_KEY,
	});

	const chatStream = await openai.chat.completions.create({
		model: "gpt-4o-mini",
		messages: [{ role: "user", content: "Tell me a story" }],
		stream: true,
	});

	return streamText(c, async (stream) => {
		for await (const message of chatStream) {
			await stream.write(message.choices[0].delta.content || "");
		}
		stream.close();
	});
});

export default app;