course/frontend/src/lib/storage.ts

const isBrowser = typeof window !== 'undefined';

const rootKey = 'uooc-progress';

export const storageKeys = {
  accessToken: `${rootKey}:access-token`,
  selectedPlatformId: (userId: number) => `${rootKey}:user:${userId}:selected-platform-id`,
  selectedCourseIds: (userId: number) => `${rootKey}:user:${userId}:selected-course-map`,
  courseOptions: (userId: number) => `${rootKey}:user:${userId}:course-options`,
  progressSnapshots: (userId: number) => `${rootKey}:user:${userId}:progress-snapshots`,
};

export function readText(key: string, fallback = ''): string {
  if (!isBrowser) {
    return fallback;
  }

  return window.localStorage.getItem(key) ?? fallback;
}

export function writeText(key: string, value: string): void {
  if (!isBrowser) {
    return;
  }

  window.localStorage.setItem(key, value);
}

export function removeKey(key: string): void {
  if (!isBrowser) {
    return;
  }

  window.localStorage.removeItem(key);
}

export function readJson<T>(key: string, fallback: T): T {
  if (!isBrowser) {
    return fallback;
  }

  const raw = window.localStorage.getItem(key);
  if (!raw) {
    return fallback;
  }

  try {
    return JSON.parse(raw) as T;
  } catch {
    return fallback;
  }
}

export function writeJson<T>(key: string, value: T): void {
  if (!isBrowser) {
    return;
  }

  window.localStorage.setItem(key, JSON.stringify(value));
}