/**
 * SMI-644: Cache Entry Data Structure
 * Enhanced cache entry with TTL tracking and hit count for popularity detection
 */
import type { SearchResult } from './lru.js';
/**
 * TTL tiers based on query popularity
 */
export declare enum TTLTier {
    /** Popular queries (>10 hits/hour): 4 hours */
    POPULAR = 14400000,
    /** Standard queries: 1 hour */
    STANDARD = 3600000,
    /** Rare queries (<1 hit/day): 15 minutes */
    RARE = 900000
}
/**
 * Popularity thresholds for TTL determination
 */
export declare const POPULARITY_THRESHOLDS: {
    /** Hits per hour to be considered "popular" */
    readonly POPULAR_HITS_PER_HOUR: 10;
    /** Minimum age (ms) before evaluating popularity */
    readonly MIN_AGE_FOR_EVALUATION: number;
};
/**
 * Enhanced cache entry with TTL and popularity tracking
 */
export interface CacheEntry<T = SearchResult[]> {
    /** Unique cache key */
    key: string;
    /** Cached data */
    data: T;
    /** Total count for search results */
    totalCount: number;
    /** Creation timestamp (ms) */
    createdAt: number;
    /** Expiration timestamp (ms) */
    expiresAt: number;
    /** Number of cache hits */
    hitCount: number;
    /** Last access timestamp (ms) */
    lastAccessedAt: number;
    /** Current TTL tier */
    ttlTier: TTLTier;
}
/**
 * Serialized format for persistent storage
 */
export interface SerializedCacheEntry {
    key: string;
    data_json: string;
    total_count: number;
    created_at: number;
    expires_at: number;
    hit_count: number;
    last_accessed_at: number;
    ttl_tier: number;
}
/**
 * Create a new cache entry with default TTL
 */
export declare function createCacheEntry<T = SearchResult[]>(key: string, data: T, totalCount: number, ttlTier?: TTLTier): CacheEntry<T>;
/**
 * Record a hit on a cache entry
 * Returns updated entry (immutable pattern)
 */
export declare function recordHit<T>(entry: CacheEntry<T>): CacheEntry<T>;
/**
 * Calculate TTL tier based on hit rate
 */
export declare function calculateTTLTier(createdAt: number, hitCount: number, now?: number): TTLTier;
/**
 * Check if cache entry is expired
 */
export declare function isExpired<T>(entry: CacheEntry<T>, now?: number): boolean;
/**
 * Check if entry should be refreshed (approaching expiration)
 * Returns true if within 10% of TTL remaining
 */
export declare function shouldRefresh<T>(entry: CacheEntry<T>, now?: number): boolean;
/**
 * Validate cache key for security (standards.md §4)
 * Prevents injection attacks through cache keys
 */
export declare function isValidCacheKey(key: string): boolean;
/**
 * Serialize cache entry for persistence
 * Uses safe JSON serialization to prevent prototype pollution
 */
export declare function serializeCacheEntry<T>(entry: CacheEntry<T>): SerializedCacheEntry;
/**
 * Deserialize cache entry from persistence
 * Validates data to prevent prototype pollution (security: standards.md §4)
 */
export declare function deserializeCacheEntry<T = SearchResult[]>(serialized: SerializedCacheEntry): CacheEntry<T>;
/**
 * Get human-readable TTL tier name
 */
export declare function getTTLTierName(tier: TTLTier): string;
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