import { EventEmitter } from 'events';
/**
 * Individual cache operation record
 */
export interface CacheOperationRecord {
    type: 'get' | 'set' | 'delete' | 'clear';
    layer: string;
    hit: boolean;
    latency: number;
    error?: string;
    key?: string;
    timestamp: Date;
}
/**
 * Cache operation metrics
 */
export interface CacheMetrics {
    /** Total number of operations */
    totalOperations: number;
    /** Hit/miss statistics */
    hits: number;
    misses: number;
    hitRate: number;
    /** Latency metrics (ms) */
    avgLatency: number;
    minLatency: number;
    maxLatency: number;
    p95Latency: number;
    p99Latency: number;
    /** Operation counts by type */
    gets: number;
    sets: number;
    deletes: number;
    clears: number;
    /** Size metrics */
    totalKeys: number;
    totalSize: number;
    /** Error metrics */
    errors: number;
    errorRate: number;
    /** Layer-specific metrics */
    layerMetrics: {
        cls: {
            hits: number;
            misses: number;
            avgLatency: number;
        };
        memory: {
            hits: number;
            misses: number;
            avgLatency: number;
            size: number;
        };
        redis: {
            hits: number;
            misses: number;
            avgLatency: number;
        };
    };
    /** Time window for these metrics */
    timeWindow: {
        start: Date;
        end: Date;
        duration: number;
    };
}
/**
 * Cache metrics service
 *
 * Collects and analyzes cache performance metrics
 */
export declare class CacheMetricsService extends EventEmitter {
    private readonly logger;
    private readonly operations;
    private readonly maxOperations;
    private readonly maxAge;
    constructor();
    /**
     * Record a cache operation
     */
    recordOperation(type: 'get' | 'set' | 'delete' | 'clear', layer: string, hit: boolean, latency: number, error?: string, key?: string): void;
    /**
     * Get metrics for a time window
     */
    getMetrics(timeWindowMs?: number): CacheMetrics;
    /**
     * Get real-time metrics snapshot
     */
    getSnapshot(): Partial<CacheMetrics>;
    /**
     * Get top slow operations
     */
    getSlowOperations(limit?: number): CacheOperationRecord[];
    /**
     * Get most accessed keys
     */
    getMostAccessedKeys(limit?: number): {
        key: string;
        count: number;
        avgLatency: number;
    }[];
    /**
     * Get error breakdown
     */
    getErrorBreakdown(): {
        error: string;
        count: number;
        lastOccurrence: Date;
    }[];
    /**
     * Reset all metrics
     */
    resetMetrics(): void;
    /**
     * Export metrics for external monitoring systems
     */
    exportMetrics(format?: 'prometheus' | 'json'): string;
    /**
     * Clean up old operation records
     */
    private cleanupOldRecords;
    /**
     * Create empty metrics object
     */
    private createEmptyMetrics;
    /**
     * Calculate layer-specific metrics
     */
    private calculateLayerMetrics;
    /**
     * Calculate average of array
     */
    private average;
    /**
     * Calculate percentile
     */
    private percentile;
    /**
     * Get unique key count
     */
    private getUniqueKeyCount;
    /**
     * Estimate total cache size
     */
    private estimateTotalSize;
    /**
     * Convert metrics to Prometheus format
     */
    private toPrometheusFormat;
}