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Next.js Route Handlers

RAGChat integrates with Next.js route handlers out of the box. Here’s how to use it:

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Basic usage

import { ragChat } from "@/utils/rag-chat";
import { NextResponse } from "next/server";

export const POST = async (req: Request) => {
  // 👇 user message
  const { message } = await req.json();
  const { output } = await ragChat.chat(message);
  return NextResponse.json({ output });
};

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Streaming responses

To stream the response from a route handler:

import { ragChat } from "@/utils/rag-chat";

export const POST = async (req: Request) => {
  const { message } = await req.json();
  const { output } = await ragChat.chat(message, { streaming: true });
  return new Response(output);
};

On the frontend, you can read the streamed data like this:

"use client"

export const ChatComponent = () => {
  const [response, setResponse] = useState('');

  async function fetchStream() {
    const response = await fetch("/api/chat", {
      method: "POST",
      body: JSON.stringify({ message: "Your question here" }),
    });

    if (!response.body) {
      console.error("No response body");
      return;
    }

    const reader = response.body.getReader();
    const decoder = new TextDecoder();

    while (true) {
      const { done, value } = await reader.read();
      if (done) break;

      const chunk = decoder.decode(value, { stream: true });
      setResponse(prev => prev + chunk);
    }
  }

  useEffect(() => {
    fetchStream();
  }, []);

  return <div>{response}</div>;
}

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Next.js Server Actions

RAGChat supports Next.js server actions natively. First, define your server action:

"use server";

import { ragChat } from "@/utils/rag-chat";
import { createServerActionStream } from "@upstash/rag-chat/nextjs";

export const serverChat = async (message: string) => {
  const { output } = await ragChat.chat(message, { streaming: true });

  // 👇 adapter to let us stream from server actions
  return createServerActionStream(output);
};

Second, use the server action in your client component:

"use client";

import { readServerActionStream } from "@upstash/rag-chat/nextjs";

export const ChatComponent = () => {
  const [response, setResponse] = useState('');

  const clientChat = async () => {
    const stream = await serverChat("How are you?");

    for await (const chunk of readServerActionStream(stream)) {
      setResponse(prev => prev + chunk);
    }
  };

  return (
    <div>
      <button onClick={clientChat}>Start Chat</button>
      <div>{response}</div>
    </div>
  );
};

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