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1/*
2 * Copyright 2022, The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17export class PersistentStoreProxy {
18  static new<T extends object>(key: string, defaultState: T, storage: Storage): T {
19    const storedState = JSON.parse(storage.getItem(key) ?? '{}');
20    const currentState = mergeDeep({}, structuredClone(defaultState));
21    mergeDeepKeepingStructure(currentState, storedState);
22    return wrapWithPersistentStoreProxy(key, currentState, storage) as T;
23  }
24}
25
26function wrapWithPersistentStoreProxy(
27  storeKey: string,
28  object: object,
29  storage: Storage,
30  baseObject: object = object
31): object {
32  const updatableProps: string[] = [];
33
34  for (const [key, value] of Object.entries(object)) {
35    if (typeof value === 'string' || typeof value === 'boolean' || value === undefined) {
36      if (!Array.isArray(object)) {
37        updatableProps.push(key);
38      }
39    } else {
40      (object as any)[key] = wrapWithPersistentStoreProxy(storeKey, value, storage, baseObject);
41    }
42  }
43
44  const proxyObj = new Proxy(object, {
45    set: (target, prop, newValue) => {
46      if (typeof prop === 'symbol') {
47        throw Error("Can't use symbol keys only strings");
48      }
49      if (Array.isArray(target) && typeof prop === 'number') {
50        target[prop] = newValue;
51        storage.setItem(storeKey, JSON.stringify(baseObject));
52        return true;
53      }
54      if (!Array.isArray(target) && updatableProps.includes(prop)) {
55        (target as any)[prop] = newValue;
56        storage.setItem(storeKey, JSON.stringify(baseObject));
57        return true;
58      }
59      throw Error(
60        `Object property '${prop}' is not updatable. Can only update leaf keys: [${updatableProps}]`
61      );
62    },
63  });
64
65  return proxyObj;
66}
67
68function isObject(item: any): boolean {
69  return item && typeof item === 'object' && !Array.isArray(item);
70}
71
72/**
73 * Merge sources into the target keeping the structure of the target.
74 * @param target the object we mutate by merging the data from source into, but keep the object structure of
75 * @param source the object we merge into target
76 * @return the mutated target object
77 */
78function mergeDeepKeepingStructure(target: any, source: any): any {
79  if (isObject(target) && isObject(source)) {
80    for (const key in target) {
81      if (source[key] === undefined) {
82        continue;
83      }
84
85      if (isObject(target[key]) && isObject(source[key])) {
86        mergeDeepKeepingStructure(target[key], source[key]);
87        continue;
88      }
89
90      if (!isObject(target[key]) && !isObject(source[key])) {
91        Object.assign(target, {[key]: source[key]});
92        continue;
93      }
94    }
95  }
96
97  return target;
98}
99
100function mergeDeep(target: any, ...sources: any): any {
101  if (!sources.length) return target;
102  const source = sources.shift();
103
104  if (isObject(target) && isObject(source)) {
105    for (const key in source) {
106      if (isObject(source[key])) {
107        if (!target[key]) Object.assign(target, {[key]: {}});
108        mergeDeep(target[key], source[key]);
109      } else {
110        Object.assign(target, {[key]: source[key]});
111      }
112    }
113  }
114
115  return mergeDeep(target, ...sources);
116}
117