localStorageWithExpiry

/**
 * localStorage persists data until it is explicitly removed. Sometimes that is
 * exactly what you want, but sometimes stored values should become invalid after
 * a period of time.
 *
 * This class wraps localStorage and supports storing string values with an
 * optional expiry time. Values can expire via:
 * - ttl: time-to-live in milliseconds (relative to now)
 * - expiresAt: absolute timestamp or Date object
 *
 * This is a small wrapper focused on core expiry logic, not a full Storage API
 * replacement.
 */
export default class LocalStorageWithExpiry {
  /**
   * Retrieve a value from localStorage if it has not expired.
   * Returns null if the key does not exist or has expired.
   *
   * @param {string} key
   * @returns {string | null}
   */
  getItem(key) {
    const stored = localStorage.getItem(key);
    if (stored == null) {
      return null;
    }

    try {
      const { value, expiresAt } = JSON.parse(stored);

      // Check expiry: if expiresAt is in the past, item has expired.
      if (expiresAt != null && Date.now() > expiresAt) {
        // Clean up expired item.
        localStorage.removeItem(key);
        return null;
      }

      return value;
    } catch (e) {
      // Fallback: return the raw string if not JSON or no expiry metadata.
      return stored;
    }
  }

  /**
   * Store a value in localStorage with optional expiry.
   *
   * @param {string} key - Storage key
   * @param {string} value - Value to store
   * @param {{ ttl?: number, expiresAt?: number | Date }} [options] - Expiry options
   *   - ttl: milliseconds from now until expiry
   *   - expiresAt: absolute timestamp (ms) or Date object
   * @returns {void}
   */
  setItem(key, value, options) {
    let expiresAt = null;

    if (options) {
      if (options.ttl != null && options.expiresAt != null) {
        throw new TypeError('ttl and expiresAt cannont coexists');
      }
      if (options.ttl != null) {
        // Relative expiry: ttl milliseconds from now.
        expiresAt = Date.now() + options.ttl;
      } else if (options.expiresAt != null) {
        // Absolute expiry: use provided timestamp or Date.
        expiresAt =
          options.expiresAt instanceof Date
            ? options.expiresAt.getTime()
            : options.expiresAt;
      }
    }

    // Store value + expiry metadata as JSON.
    const payload = { value, expiresAt };
    localStorage.setItem(key, JSON.stringify(payload));
  }
}