next-chat/app/api/proxy.ts

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

export async function handle(
  req: NextRequest,
  { params }: { params: { path: string[] } },
) {
  console.log("[Proxy Route] params ", params);

  if (req.method === "OPTIONS") {
    return NextResponse.json({ body: "OK" }, { status: 200 });
  }

  // remove path params from searchParams
  req.nextUrl.searchParams.delete("path");
  req.nextUrl.searchParams.delete("provider");

  const subpath = params.path.join("/");
  const fetchUrl = `${req.headers.get(
    "x-base-url",
  )}/${subpath}?${req.nextUrl.searchParams.toString()}`;
  const skipHeaders = ["connection", "host", "origin", "referer", "cookie"];
  const headers = new Headers(
    Array.from(req.headers.entries()).filter((item) => {
      if (
        item[0].indexOf("x-") > -1 ||
        item[0].indexOf("sec-") > -1 ||
        skipHeaders.includes(item[0])
      ) {
        return false;
      }
      return true;
    }),
  );
  const controller = new AbortController();
  const fetchOptions: RequestInit = {
    headers,
    method: req.method,
    body: req.body,
    // to fix #2485: https://stackoverflow.com/questions/55920957/cloudflare-worker-typeerror-one-time-use-body
    redirect: "manual",
    // @ts-ignore
    duplex: "half",
    signal: controller.signal,
  };

  const timeoutId = setTimeout(
    () => {
      controller.abort();
    },
    10 * 60 * 1000,
  );

  try {
    const res = await fetch(fetchUrl, fetchOptions);
    // to prevent browser prompt for credentials
    const newHeaders = new Headers(res.headers);
    newHeaders.delete("www-authenticate");
    // to disable nginx buffering
    newHeaders.set("X-Accel-Buffering", "no");

    // The latest version of the OpenAI API forced the content-encoding to be "br" in json response
    // So if the streaming is disabled, we need to remove the content-encoding header
    // Because Vercel uses gzip to compress the response, if we don't remove the content-encoding header
    // The browser will try to decode the response with brotli and fail
    newHeaders.delete("content-encoding");

    return new Response(res.body, {
      status: res.status,
      statusText: res.statusText,
      headers: newHeaders,
    });
  } finally {
    clearTimeout(timeoutId);
  }
}