assistant-ui--assistant-ui/examples/with-langgraph/app/api/[..._path]/route.ts

import { type NextRequest, NextResponse } from "next/server";

function getCorsHeaders() {
  return {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "GET, POST, PUT, PATCH, DELETE, OPTIONS",
    "Access-Control-Allow-Headers": "*",
  };
}

async function handleRequest(req: NextRequest, method: string) {
  try {
    const path = req.nextUrl.pathname.replace(/^\/?api\//, "");
    const url = new URL(req.url);
    const searchParams = new URLSearchParams(url.search);
    searchParams.delete("_path");
    searchParams.delete("nxtP_path");
    const queryString = searchParams.toString()
      ? `?${searchParams.toString()}`
      : "";

    const options: RequestInit = {
      method,
      headers: {
        "x-api-key": process.env.LANGCHAIN_API_KEY || "",
      },
    };

    if (["POST", "PUT", "PATCH"].includes(method)) {
      options.body = await req.text();
    }

    const res = await fetch(
      `${process.env.LANGGRAPH_API_URL}/${path}${queryString}`,
      options,
    );

    const headers = new Headers(res.headers);
    headers.delete("content-encoding");
    headers.delete("content-length");
    headers.delete("transfer-encoding");
    const corsHeaders = getCorsHeaders();
    for (const [key, value] of Object.entries(corsHeaders)) {
      headers.set(key, value);
    }

    return new NextResponse(res.body, {
      status: res.status,
      statusText: res.statusText,
      headers,
    });
  } catch (e: unknown) {
    if (e instanceof Error) {
      const typedError = e as Error & { status?: number };
      return NextResponse.json(
        { error: typedError.message },
        { status: typedError.status ?? 500 },
      );
    }
    return NextResponse.json({ error: "Unknown error" }, { status: 500 });
  }
}

export const GET = (req: NextRequest) => handleRequest(req, "GET");
export const POST = (req: NextRequest) => handleRequest(req, "POST");
export const PUT = (req: NextRequest) => handleRequest(req, "PUT");
export const PATCH = (req: NextRequest) => handleRequest(req, "PATCH");
export const DELETE = (req: NextRequest) => handleRequest(req, "DELETE");
export const OPTIONS = () =>
  new NextResponse(null, {
    status: 204,
    headers: getCorsHeaders(),
  });