Add Google Calendar sync: OAuth connect flow, dedicated Бронирования calendar, best-effort event create/update/delete on booking changes

src/app/api/google/callback/route.ts

@@ -0,0 +1,43 @@
+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" });
+}