app/api/chat/route.ts

import { OpenAIStream, StreamingTextResponse } from 'ai';
import OpenAI from 'openai';

import { auth } from '@/auth';
import { nanoid } from '@/lib/utils';
import {
	ChatCompletionContentPart,
	ChatCompletionMessageParam,
} from 'openai/resources';

export const runtime = 'edge';

const openai = new OpenAI({
	apiKey: process.env.OPENAI_API_KEY,
});

export async function POST(req: Request) {
	const json = await req.json();
	const { messages, image } = json as {
		messages: ChatCompletionMessageParam[];
		image: string;
	};

	const userId = (await auth())?.user.id;

	if (!userId) {
		return new Response('Unauthorized', {
			status: 401,
		});
	}

	const messagesWithImage: ChatCompletionMessageParam[] = messages.map(
		message => {
			if (message.role !== 'user') return message;
			const contentWithImage: ChatCompletionContentPart[] = [
				{
					type: 'text',
					text: message.content as string,
				},
				{
					type: 'image_url',
					image_url: { url: image },
				},
			];
			return {
				role: 'user',
				content: contentWithImage,
			};
		},
	);

	const res = await openai.chat.completions.create({
		model: 'gpt-4-vision-preview',
		messages: messagesWithImage,
		temperature: 0.7,
		stream: true,
		max_tokens: 300,
	});

	const stream = OpenAIStream(res, {
		async onCompletion(completion) {
			const title = json.messages[0].content.substring(0, 100);
			const id = json.id ?? nanoid();
			const createdAt = Date.now();
			const payload = {
				id,
				title,
				userId,
				createdAt,
				messages: [
					...messages,
					{
						content: completion,
						role: 'assistant',
					},
				],
			};
		},
	});

	return new StreamingTextResponse(stream);
}