55 lines
1.3 KiB
TypeScript
55 lines
1.3 KiB
TypeScript
export class Cache<T> {
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private cache: Map<string | null, { date: number; value: T; }>;
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private lifetime: number;
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constructor(lifetime: Cache<never>['lifetime']) {
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this.cache = new Map();
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this.lifetime = lifetime;
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}
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public set(key: string | null, value: T): void {
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this.cache.set(key, {
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date: Date.now(),
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value,
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});
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}
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public get(key: string | null): T | undefined {
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const cached = this.cache.get(key);
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if (cached == null) return undefined;
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if ((Date.now() - cached.date) > this.lifetime) {
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this.cache.delete(key);
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return undefined;
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}
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return cached.value;
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}
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public delete(key: string | null) {
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this.cache.delete(key);
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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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* optional: キャッシュが存在してもvalidatorでfalseを返すとキャッシュ無効扱いにします
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*/
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public async fetch(key: string | null, fetcher: () => Promise<T>, validator?: (cachedValue: T) => boolean): Promise<T> {
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const cachedValue = this.get(key);
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if (cachedValue !== undefined) {
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if (validator) {
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if (validator(cachedValue)) {
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// Cache HIT
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return cachedValue;
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}
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} else {
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// Cache HIT
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return cachedValue;
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}
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}
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// Cache MISS
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const value = await fetcher();
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this.set(key, value);
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return value;
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}
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}
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