export const runtime = "nodejs";

import { NextResponse } from "next/server";
import { cookies } from "next/headers";
import { requireAdminSession } from "@/lib/auth/require";
import { connectGoogleCalendar } from "@/lib/google/calendar";

const STATE_COOKIE = "google_oauth_state";

function redirectToSettings(request: Request, params: Record<string, string>) {
  const url = new URL("/settings/google", request.url);
  for (const [k, v] of Object.entries(params)) url.searchParams.set(k, v);
  return NextResponse.redirect(url);
}

export async function GET(request: Request) {
  const { session, response } = await requireAdminSession();
  if (!session) return response;

  const url = new URL(request.url);
  const code = url.searchParams.get("code");
  const state = url.searchParams.get("state");
  const error = url.searchParams.get("error");

  const cookieStore = await cookies();
  const expectedState = cookieStore.get(STATE_COOKIE)?.value;
  cookieStore.delete(STATE_COOKIE);

  if (error) {
    return redirectToSettings(request, { error: "Доступ не предоставлен" });
  }
  if (!code || !state || !expectedState || state !== expectedState) {
    return redirectToSettings(request, { error: "Некорректный ответ от Google — попробуйте подключить снова" });
  }

  try {
    await connectGoogleCalendar(code, session.user.id);
  } catch (err) {
    return redirectToSettings(request, { error: err instanceof Error ? err.message : "Не удалось подключить Google Calendar" });
  }

  return redirectToSettings(request, { connected: "1" });
}