/**
 * In-memory LRU cache for streaming listing results.
 *
 * Keyed by a deterministic hash of query parameters so that repeat visits
 * to the same filter combination are instant (no network request).
 */
import type { PropertyFeature } from '@/types';
import type { ParameterValues } from '@/components/FilterPanel';

interface CacheEntry {
  features: PropertyFeature[];
  timestamp: number;
}

const cache = new Map<string, CacheEntry>();
const MAX_ENTRIES = 5;

export function makeCacheKey(params: ParameterValues): string {
  const sorted = Object.entries(params)
    .filter(([, v]) => v !== undefined && v !== null && v !== '')
    .sort(([a], [b]) => a.localeCompare(b))
    .map(([k, v]) => `${k}=${v instanceof Date ? v.toISOString() : v}`);
  return sorted.join('&');
}

export function getCached(params: ParameterValues): PropertyFeature[] | null {
  const key = makeCacheKey(params);
  const entry = cache.get(key);
  if (!entry) return null;
  return entry.features;
}

export function setCached(params: ParameterValues, features: PropertyFeature[]): void {
  const key = makeCacheKey(params);
  if (cache.size >= MAX_ENTRIES && !cache.has(key)) {
    // Evict oldest entry (first inserted)
    const oldest = cache.keys().next().value;
    if (oldest) cache.delete(oldest);
  }
  cache.set(key, { features, timestamp: Date.now() });
}

export function invalidateAll(): void {
  cache.clear();
}