json-render/examples/chat/app/api/generate/route.ts

import { agent } from "@/lib/agent";
import { minuteRateLimit, dailyRateLimit } from "@/lib/rate-limit";
import {
  convertToModelMessages,
  createUIMessageStream,
  createUIMessageStreamResponse,
  type UIMessage,
} from "ai";
import { pipeJsonRender } from "@json-render/core";
import { headers } from "next/headers";

export const maxDuration = 60;

export async function POST(req: Request) {
  const headersList = await headers();
  const ip = headersList.get("x-forwarded-for")?.split(",")[0] ?? "anonymous";

  const [minuteResult, dailyResult] = await Promise.all([
    minuteRateLimit.limit(ip),
    dailyRateLimit.limit(ip),
  ]);

  if (!minuteResult.success || !dailyResult.success) {
    const isMinuteLimit = !minuteResult.success;
    return new Response(
      JSON.stringify({
        error: "Rate limit exceeded",
        message: isMinuteLimit
          ? "Too many requests. Please wait a moment before trying again."
          : "Daily limit reached. Please try again tomorrow.",
      }),
      {
        status: 429,
        headers: { "Content-Type": "application/json" },
      },
    );
  }

  const body = await req.json();
  const uiMessages: UIMessage[] = body.messages;

  if (!uiMessages || !Array.isArray(uiMessages) || uiMessages.length === 0) {
    return new Response(
      JSON.stringify({ error: "messages array is required" }),
      {
        status: 400,
        headers: { "Content-Type": "application/json" },
      },
    );
  }

  const modelMessages = await convertToModelMessages(uiMessages);
  const result = await agent.stream({ messages: modelMessages });

  const stream = createUIMessageStream({
    execute: async ({ writer }) => {
      writer.merge(pipeJsonRender(result.toUIMessageStream()));
    },
  });

  return createUIMessageStreamResponse({ stream });
}