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/*
* SPDX-FileCopyrightText: syuilo and misskey-project
* SPDX-License-Identifier: AGPL-3.0-only
*/
import { ref } from 'vue';
export class Cache<T> {
private cachedAt: number | null = null;
public value = ref<T | undefined>();
private lifetime: number;
private fetcher: () => Promise<T>;
constructor(lifetime: Cache<never>['lifetime'], fetcher: () => Promise<T>) {
this.lifetime = lifetime;
this.fetcher = fetcher;
}
public set(value: T): void {
this.cachedAt = Date.now();
this.value.value = value;
}
private get(): T | undefined {
if (this.cachedAt == null) return undefined;
if ((Date.now() - this.cachedAt) > this.lifetime) {
this.value.value = undefined;
this.cachedAt = null;
return undefined;
}
return this.value.value;
}
public delete() {
this.cachedAt = null;
}
/**
* 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
*/
public async fetch(): Promise<T> {
const cachedValue = this.get();
if (cachedValue !== undefined) {
// Cache HIT
return cachedValue;
}
// Cache MISS
const value = await this.fetcher();
this.set(value);
return value;
}
}
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