43 lines
957 B
TypeScript
43 lines
957 B
TypeScript
export class Cache<T> {
|
|
private cache: Map<string | null, { date: number; value: T; }>;
|
|
private lifetime: number;
|
|
|
|
constructor(lifetime: Cache<never>['lifetime']) {
|
|
this.cache = new Map();
|
|
this.lifetime = lifetime;
|
|
}
|
|
|
|
public set(key: string | null, value: T): void {
|
|
this.cache.set(key, {
|
|
date: Date.now(),
|
|
value,
|
|
});
|
|
}
|
|
|
|
public get(key: string | null): T | undefined {
|
|
const cached = this.cache.get(key);
|
|
if (cached == null) return undefined;
|
|
if ((Date.now() - cached.date) > this.lifetime) {
|
|
this.cache.delete(key);
|
|
return undefined;
|
|
}
|
|
return cached.value;
|
|
}
|
|
|
|
public delete(key: string | null) {
|
|
this.cache.delete(key);
|
|
}
|
|
|
|
public async fetch(key: string | null, fetcher: () => Promise<T>): Promise<T> {
|
|
const cachedValue = this.get(key);
|
|
if (cachedValue !== undefined) {
|
|
// Cache HIT
|
|
return cachedValue;
|
|
}
|
|
|
|
// Cache MISS
|
|
const value = await fetcher();
|
|
this.set(key, value);
|
|
return value;
|
|
}
|
|
}
|