// shared/modules/google-reviews/cache.ts - LRU Cache Implementation
import type { CacheEntry, GetGoogleReviewsRequest, GoogleReviewsResponse } from "./types.js";
const MAX_CACHE_SIZE = 200;
const CACHE_TTL_MS = 24 * 60 * 60 * 1000; // 24 hours
/**
* Generic LRU (Least Recently Used) cache implementation.
* Uses Map insertion order for LRU eviction.
*/
export class LRUCache<T> {
private cache = new Map<string, CacheEntry<T>>();
private maxSize: number;
private ttlMs: number;
constructor(maxSize: number = MAX_CACHE_SIZE, ttlMs: number = CACHE_TTL_MS) {
this.maxSize = maxSize;
this.ttlMs = ttlMs;
}
/**
* Get a value from the cache.
* Returns undefined if not found or expired.
* Refreshes position on access (LRU behavior).
*/
get(key: string): T | undefined {
const entry = this.cache.get(key);
if (!entry) {
return undefined;
}
const now = Date.now();
// Check if expired
if (entry.expiresAt <= now) {
this.cache.delete(key);
return undefined;
}
// Refresh position in Map (delete and re-add for LRU)
this.cache.delete(key);
entry.accessedAt = now;
this.cache.set(key, entry);
return entry.data;
}
/**
* Set a value in the cache.
* Evicts oldest entries if at capacity.
*/
set(key: string, data: T): void {
const now = Date.now();
// If key already exists, delete it first (to update position)
if (this.cache.has(key)) {
this.cache.delete(key);
}
// Evict oldest entries if at capacity
while (this.cache.size >= this.maxSize) {
// Map.keys().next() returns the oldest (first inserted) key
const oldestKey = this.cache.keys().next().value;
if (oldestKey !== undefined) {
this.cache.delete(oldestKey);
}
}
this.cache.set(key, {
data,
expiresAt: now + this.ttlMs,
accessedAt: now,
});
}
/**
* Check if key exists and is not expired
*/
has(key: string): boolean {
const entry = this.cache.get(key);
if (!entry) return false;
if (entry.expiresAt <= Date.now()) {
this.cache.delete(key);
return false;
}
return true;
}
/**
* Delete a key from the cache
*/
delete(key: string): boolean {
return this.cache.delete(key);
}
/**
* Clear all entries
*/
clear(): void {
this.cache.clear();
}
/**
* Get current cache size
*/
get size(): number {
return this.cache.size;
}
}
/**
* Simple hash function for strings.
* Used to include restaurant name in cache key.
*/
export function simpleHash(str: string): string {
let hash = 0;
for (let i = 0; i < str.length; i++) {
const char = str.charCodeAt(i);
hash = ((hash << 5) - hash) + char;
hash = hash & hash; // Convert to 32-bit integer
}
// Convert to positive hex string
return Math.abs(hash).toString(16);
}
/**
* Create a cache key for Google Reviews requests.
* Includes restaurantId, name hash, and rounded coordinates.
*/
export function createCacheKey(request: GetGoogleReviewsRequest): string {
// Round lat/lng to 4 decimal places (~11m precision)
const lat = parseFloat(request.latitude).toFixed(4);
const lng = parseFloat(request.longitude).toFixed(4);
// Include name hash to differentiate restaurants at same location
const nameHash = simpleHash(request.restaurantName.toLowerCase());
return `${request.restaurantId}-${nameHash}-${lat}-${lng}`;
}
// Singleton cache instance for Google Reviews
export const googleReviewsCache = new LRUCache<GoogleReviewsResponse>(MAX_CACHE_SIZE, CACHE_TTL_MS);
