Jesus Navalon
54 lines
1.5 KiB
TypeScript
54 lines
1.5 KiB
TypeScript
import { Injectable } from '@angular/core';
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// Cache expiration time. (In a real shop this should not be the beast approach due to stock changes)
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const CACHE_TTL_MS = 60 * 60 * 1000;
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// Prefix for cache keys to avoid collisions with other localStorage entries.
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const CACHE_PREFIX = 'itx-cache:';
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interface CacheEntry<T> {
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timestamp: number;
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data: T;
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}
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// Generic cache service
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@Injectable({ providedIn: 'root' })
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export class CacheService {
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// returns cached item if it exists and is not expired, otherwise fetches it using the provided fetcher function.
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async getOrFetch<T>(key: string, fetcher: () => Promise<T>): Promise<T> {
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const cached = this.read<T>(key);
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if (cached && Date.now() - cached.timestamp < CACHE_TTL_MS) {
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return cached.data;
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}
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const data = await fetcher();
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this.write(key, data);
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return data;
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}
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// Clears all cache entries managed by this service.
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clear(): void {
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Object.keys(localStorage)
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.filter((key) => key.startsWith(CACHE_PREFIX))
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.forEach((key) => localStorage.removeItem(key));
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}
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private read<T>(key: string): CacheEntry<T> | null {
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const raw = localStorage.getItem(CACHE_PREFIX + key);
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if (!raw) {
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return null;
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}
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try {
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return JSON.parse(raw) as CacheEntry<T>;
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} catch {
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// corrupted data
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return null;
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}
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}
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private write<T>(key: string, data: T): void {
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const entry: CacheEntry<T> = { timestamp: Date.now(), data };
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localStorage.setItem(CACHE_PREFIX + key, JSON.stringify(entry));
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}
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}
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