import { createHash, randomBytes } from "node:crypto";

/**
 * Long-lived, random, rotatable secret for a personal calendar-subscription
 * URL (/calendar/<token>.ics) — treated like an API key, not a
 * short-lived link: only its hash is stored, so a database leak alone
 * can't be used to subscribe to anyone's calendar, and rotating it
 * (overwriting the stored hash) immediately invalidates the old URL.
 */
export function generateCalendarFeedToken(): string {
  return randomBytes(32).toString("hex");
}

export function hashCalendarFeedToken(token: string): string {
  return createHash("sha256").update(token).digest("hex");
}

export function calendarFeedUrl(token: string): string {
  const serverUrl = process.env.NEXT_PUBLIC_SERVER_URL || "http://localhost:3000";
  return `${serverUrl}/calendar/${token}.ics`;
}