import { NextRequest, NextResponse } from "next/server";
import { getToken } from "next-auth/jwt";
import { rateLimit } from "@/lib/rate-limit";
import {
  ADMIN_GATE_HEADER,
  ADMIN_PATHNAME_HEADER,
  adminGateToken,
} from "@/lib/admin-gate";

export async function proxy(request: NextRequest) {
  const pathname = request.nextUrl.pathname;

  // ── ADMIN GUARD ──────────────────────────────────────────────────────────
  if (pathname.startsWith("/admin")) {
    // Stamp the path so src/app/admin/layout.tsx can run its own session check
    // and still tell /admin/login apart, plus a secret-derived token proving
    // this proxy ran. set() overwrites any client-supplied value; if the proxy
    // is bypassed entirely neither header is valid and the layout fails closed.
    const withPath = new Headers(request.headers);
    withPath.set(ADMIN_PATHNAME_HEADER, pathname);
    withPath.set(ADMIN_GATE_HEADER, await adminGateToken());
    const forward = { request: { headers: withPath } };

    // Allow the login page and NextAuth API routes through without session check
    if (
      pathname === "/admin/login" ||
      pathname.startsWith("/api/auth")
    ) {
      return NextResponse.next(forward);
    }

    const token = await getToken({
      req: request,
      secret: process.env.NEXTAUTH_SECRET,
    });

    if (!token) {
      const loginUrl = new URL("/admin/login", request.url);
      loginUrl.searchParams.set("callbackUrl", pathname);
      return NextResponse.redirect(loginUrl);
    }

    return NextResponse.next(forward);
  }

  // ── CLIENT TOKEN/SLUG GUARD ──────────────────────────────────────────────
  if (pathname.startsWith("/client/")) {
    const slugOrTokenMatch = pathname.match(/^\/client\/([a-zA-Z0-9_-]+)/);
    if (!slugOrTokenMatch) {
      return NextResponse.rewrite(new URL("/not-found", request.url));
    }

    // Client slugs carry far less entropy than the 21-char nanoid tokens
    // (see C-2 in .planning/SECURITY-SCAN.md), so this path must not be
    // brute-forceable at speed. Was previously applied only to /quote.
    const clientIp =
      request.headers.get("x-forwarded-for") ||
      request.headers.get("x-real-ip") ||
      "unknown";
    if (!rateLimit(`client:${clientIp}`, 20, 60 * 1000)) {
      return NextResponse.json(
        { error: "Troppi accessi. Riprova tra un minuto." },
        { status: 429 }
      );
    }

    const slugOrToken = slugOrTokenMatch[1];

    try {
      // Use localhost to avoid hairpin NAT issues in Docker.
      // request.url is the external hostname (via Traefik); inside the container the app is on localhost.
      const port = process.env.PORT ?? "3000";
      const base = `http://localhost:${port}`;

      const internalHeaders = {
        "x-internal-secret": process.env.INTERNAL_SECRET ?? "",
      };

      // Try slug first (D-06) — user-friendly slugs before token fallback
      let res = await fetch(
        `${base}/api/internal/validate-slug?slug=${encodeURIComponent(slugOrToken)}`,
        { headers: internalHeaders }
      );

      // If slug not found, fall back to token validation (existing links continue to work)
      if (!res.ok) {
        res = await fetch(
          `${base}/api/internal/validate-token?token=${encodeURIComponent(slugOrToken)}`,
          { headers: internalHeaders }
        );
      }

      if (!res.ok) {
        return NextResponse.rewrite(new URL("/not-found", request.url));
      }

      return NextResponse.next();
    } catch {
      return NextResponse.rewrite(new URL("/not-found", request.url));
    }
  }

  // ── PUBLIC QUOTE ROUTES (rate limited) ───────────────────────────────────
  if (pathname.match(/^\/quote\/[a-zA-Z0-9_-]{21}\/?$/)) {
    const ip = request.headers.get("x-forwarded-for") || request.headers.get("x-real-ip") || "unknown";
    const allowed = rateLimit(ip, 3, 60 * 1000); // 3 views per minute

    if (!allowed) {
      return NextResponse.json(
        { error: "Troppi accessi. Riprova tra un minuto." },
        { status: 429 }
      );
    }
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/admin/:path*", "/client/:path*", "/quote/:path*"],
};