middleware.ts

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

/** Sliding window rate limit for live research API (abuse / cost protection). */
const WINDOW_MS = 60_000;
const MAX_REQUESTS = 45;

type GlobalWithRl = typeof globalThis & { __researchLiveRl?: Map<string, number[]> };

function clientKey(req: NextRequest): string {
  const forwarded = req.headers.get("x-forwarded-for");
  const first = forwarded?.split(",")[0]?.trim();
  return first || req.headers.get("x-real-ip") || "unknown";
}

export function middleware(req: NextRequest) {
  const g = globalThis as GlobalWithRl;
  if (!g.__researchLiveRl) g.__researchLiveRl = new Map<string, number[]>();

  const now = Date.now();
  const key = clientKey(req);
  const prev = g.__researchLiveRl.get(key) ?? [];
  const windowed = prev.filter((t) => now - t < WINDOW_MS);

  if (windowed.length >= MAX_REQUESTS) {
    return NextResponse.json(
      { error: "Too many requests", retryAfterSec: Math.ceil(WINDOW_MS / 1000) },
      {
        status: 429,
        headers: { "Retry-After": String(Math.ceil(WINDOW_MS / 1000)) },
      }
    );
  }

  windowed.push(now);
  g.__researchLiveRl.set(key, windowed);
  return NextResponse.next();
}

export const config = {
  matcher: "/api/research/live",
};