1/**
2 * Copyright (c) 2021-2022 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 *     http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16
17const TAG = 'DiskLruCache';
18
19/**
20 * A class provides persistent operation for memory cache.
21 */
22export default class DiskLruCache {
23  private readonly cache;
24  private readonly capacity;
25
26  constructor(capacity = 100) {
27    this.cache = new Map();
28    this.capacity = capacity;
29    this.initMap(); //read cache from local
30  }
31
32  /**
33   * Init the cache whether the file has data.
34   */
35  initMap(): void {
36  }
37
38  /**
39   * Get cache from disk.
40   *
41   * @param {string} key - key of the cache map
42   * @return {object} - target cache object
43   */
44  getCache(key: string) {
45    if (this.cache.has(key)) {
46      // exist and update
47      const temp = this.cache.get(key);
48      //delete the old cache
49      this.cache.delete(key);
50      //update the cache to recent use
51      this.cache.set(key, temp);
52      //update local cache to recent use
53      return temp;
54    }
55    return -1;
56  }
57
58  /**
59   * Put cache to disk.
60   *
61   * @param {string} key - key of the cache map
62   * @param {object} value - value of the cache map
63   */
64  putCache(key: string, value: object | string): void {
65    if (this.cache.has(key)) {
66      // exist and update
67      this.cache.delete(key);
68    } else if (this.cache.size >= this.capacity) {
69      // if size > capacity ,remove the old
70      this.remove(this.cache.keys().next().value);
71    }
72    //update the cache to recent use
73    this.cache.set(key, value);
74  }
75
76  /**
77   * Remove cache of corresponding key.
78   *
79   * @param {string} key - key of the cache map
80   */
81  remove(key: string): void {
82    this.cache.delete(key);
83  }
84
85  /**
86   * Clear cache of disk.
87   */
88  clear(): void {
89    this.cache.clear();
90  }
91}