53 lines
1.2 KiB
TypeScript
53 lines
1.2 KiB
TypeScript
/*
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* SPDX-FileCopyrightText: syuilo and misskey-project
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* SPDX-License-Identifier: AGPL-3.0-only
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*/
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import { ref } from 'vue';
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export class Cache<T> {
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private cachedAt: number | null = null;
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public value = ref<T | undefined>();
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private lifetime: number;
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private fetcher: () => Promise<T>;
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constructor(lifetime: Cache<never>['lifetime'], fetcher: () => Promise<T>) {
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this.lifetime = lifetime;
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this.fetcher = fetcher;
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}
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public set(value: T): void {
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this.cachedAt = Date.now();
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this.value.value = value;
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}
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private get(): T | undefined {
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if (this.cachedAt == null) return undefined;
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if ((Date.now() - this.cachedAt) > this.lifetime) {
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this.value.value = undefined;
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this.cachedAt = null;
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return undefined;
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}
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return this.value.value;
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}
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public delete() {
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this.cachedAt = null;
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}
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/**
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* キャッシュがあればそれを返し、無ければfetcherを呼び出して結果をキャッシュ&返します
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*/
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public async fetch(): Promise<T> {
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const cachedValue = this.get();
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if (cachedValue !== undefined) {
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// Cache HIT
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return cachedValue;
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}
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// Cache MISS
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const value = await this.fetcher();
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this.set(value);
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return value;
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}
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}
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