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Storage.ts
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Storage.ts
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/**
* Copyright 2019 The AMP HTML Authors. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS-IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import type { Document } from './dom/Document';
import type { DocumentStub } from './dom/DocumentLite';
import { GetOrSet } from '../transfer/Messages';
import { StorageLocation } from '../transfer/TransferrableStorage';
import { TransferrableMutationType } from '../transfer/TransferrableMutation';
import { store } from './strings';
import { transfer } from './MutationTransfer';
/**
* @see https://developer.mozilla.org/en-US/docs/Web/API/Storage
*/
export interface Storage {
length: number;
key(n: number): string | null;
getItem(key: string): string | null;
setItem(key: string, value: string): void;
removeItem(key: string): void;
clear(): void;
}
/**
* @param document
* @param location
* @param data
*/
export function createStorage(document: Document | DocumentStub, location: StorageLocation, data: { [key: string]: string }): Storage {
const storage: any = Object.assign(Object.create(null), data);
// Define properties on a prototype-less object instead of a class so that
// it behaves more like normal objects, e.g. bracket notation and JSON.stringify.
const define = Object.defineProperty;
define(storage, 'length', {
get() {
return Object.keys(this).length;
},
});
define(storage, 'key', {
value(n: number) {
const keys = Object.keys(this);
return n >= 0 && n < keys.length ? keys[n] : null;
},
});
define(storage, 'getItem', {
value(key: string): string | null {
const value = this[key];
return value ? value : null;
},
});
define(storage, 'setItem', {
value(key: string, value: string): void {
const stringValue = String(value);
this[key] = stringValue;
transfer(document, [TransferrableMutationType.STORAGE, GetOrSet.SET, location, store(key), store(stringValue)]);
},
});
define(storage, 'removeItem', {
value(key: string): void {
delete this[key];
transfer(document, [
TransferrableMutationType.STORAGE,
GetOrSet.SET,
location,
store(key),
0, // value == 0 represents deletion.
]);
},
});
define(storage, 'clear', {
value(): void {
Object.keys(this).forEach((key) => {
delete this[key];
});
transfer(document, [
TransferrableMutationType.STORAGE,
GetOrSet.SET,
location,
0, // key == 0 represents all keys.
0, // value == 0 represents deletion.
]);
},
});
return storage as Storage;
}