[Vue composable] useExpirableStorage

useExpirableStorage.ts

const LS_KEY_PREFIX = '__expirable-storage-';

export interface ExpirableStorage<T = any> {
  getItem(key: string): T | null;
  hasItem(key: string): boolean;
  setItem(key: string, value: T, expiresAt: number): void;
}

/** 설정한 기간이 지나면 파기되는 스토리지를 만든다. */
export function useExpirableStorage<T = any>(
  storageKey: string,
): ExpirableStorage<T> {
  const storageMap = loadStorage(LS_KEY_PREFIX + storageKey);

  return {
    getItem(key) {
      updateAndSaveStorage(storageMap);
      return storageMap.get(key)?.value ?? null;
    },
    hasItem(key) {
      updateAndSaveStorage(storageMap);
      return storageMap.has(key);
    },
    setItem(key, value, expiresAt) {
      storageMap.set(key, { value, expiresAt });
      updateAndSaveStorage(storageMap);
    },
  };
}

interface ExpirableStorageItem {
  expiresAt: number;
  value: any;
}

type ExpirableStorageMap = Map<string, ExpirableStorageItem>;

function updateAndSaveStorage(storage: ExpirableStorageMap) {
  const now = Date.now();
  const keysToDelete: string[] = [];

  for (const [key, { expiresAt }] of storage.entries()) {
    if (now >= expiresAt) {
      keysToDelete.push(key);
    }
  }

  for (const key of keysToDelete) {
    storage.delete(key);
  }
}

function loadStorage(key: string): Map<string, ExpirableStorageItem> {
  try {
    const storedItem = localStorage.getItem(key);
    if (!storedItem) return new Map();

    const parsed = JSON.parse(storedItem);
    if (!Array.isArray(parsed)) return new Map();

    return new Map(parsed);
  } catch {
    return new Map();
  }
}

function saveStorage(key: string, storage: ExpirableStorageMap) {
  const json = JSON.stringify(Array.from(storage.entries()));
  localStorage.setItem(key, json);
}