/**
 * Example: QueryCache Telemetry Integration
 *
 * Shows how to integrate OpenTelemetry observability into QueryCache.
 */

import { recordCacheAccess, recordMetric } from '../src/observability';

class QueryCacheWithTelemetry {
  /**
   * Example: Cache get with telemetry
   */
  get<T = any>(key: string): T | undefined {
    const entry = this.cache.get(key);

    // Record cache hit/miss
    recordCacheAccess(key, entry !== undefined);

    if (!entry) {
      return undefined;
    }

    // Check expiration
    const now = Date.now();
    if (now - entry.timestamp > entry.ttl) {
      this.cache.delete(key);

      // Record expired entry as miss
      recordCacheAccess(key, false);

      // Record expiration metric
      recordMetric('operation', {
        operationType: 'cache_expiration',
        tableName: 'cache',
      });

      return undefined;
    }

    // Update statistics
    entry.hits++;

    // Record hit with metadata
    recordMetric('cache_hit', { key });

    return entry.value as T;
  }

  /**
   * Example: Cache set with telemetry
   */
  set<T = any>(key: string, value: T, ttl: number = 300000): void {
    const size = this.estimateSize(value);

    // Check if we need to evict
    if (this.cache.size >= this.maxSize) {
      this.evictLRU();

      // Record eviction
      recordMetric('operation', {
        operationType: 'cache_eviction',
        tableName: 'cache',
      });
    }

    // Store entry
    this.cache.set(key, {
      value,
      key,
      timestamp: Date.now(),
      ttl,
      size,
      hits: 0,
    });

    // Record cache write
    recordMetric('operation', {
      operationType: 'cache_write',
      tableName: 'cache',
      resultSize: size,
    });
  }

  /**
   * Example: Cache invalidation with telemetry
   */
  invalidateCategory(category: string): number {
    let count = 0;
    const keysToDelete: string[] = [];

    for (const [key] of this.cache) {
      if (key.startsWith(`${category}:`)) {
        keysToDelete.push(key);
      }
    }

    for (const key of keysToDelete) {
      this.cache.delete(key);
      count++;
    }

    // Record invalidation
    recordMetric('operation', {
      operationType: 'cache_invalidation',
      tableName: 'cache',
      resultSize: count,
    });

    return count;
  }

  /**
   * Example: Cache statistics with telemetry
   */
  getStatistics(): any {
    const stats = {
      hits: this.hits,
      misses: this.misses,
      hitRate: 0,
      size: this.cache.size,
      capacity: this.maxSize,
      evictions: this.evictions,
      memoryUsed: 0,
      entriesByCategory: {},
    };

    // Calculate hit rate
    const total = stats.hits + stats.misses;
    stats.hitRate = total > 0 ? (stats.hits / total) * 100 : 0;

    // Record statistics as metrics
    recordMetric('operation', {
      operationType: 'cache_stats_request',
      tableName: 'cache',
    });

    return stats;
  }

  /**
   * Example: Prune expired entries with telemetry
   */
  pruneExpired(): number {
    const now = Date.now();
    const keysToDelete: string[] = [];

    for (const [key, entry] of this.cache) {
      if (now - entry.timestamp > entry.ttl) {
        keysToDelete.push(key);
      }
    }

    for (const key of keysToDelete) {
      this.cache.delete(key);
    }

    // Record pruning
    recordMetric('operation', {
      operationType: 'cache_prune',
      tableName: 'cache',
      resultSize: keysToDelete.length,
    });

    return keysToDelete.length;
  }

  // Placeholder methods and properties
  private cache = new Map();
  private maxSize = 1000;
  private hits = 0;
  private misses = 0;
  private evictions = 0;
  private estimateSize(value: any): number {
    return 100;
  }
  private evictLRU(): void {}
}

/**
 * Integration Summary for QueryCache:
 *
 * 1. Record metrics in:
 *    - get() - cache hits/misses
 *    - set() - cache writes
 *    - invalidateCategory() - invalidations
 *    - pruneExpired() - expiration cleanup
 *    - evictLRU() - evictions
 *
 * 2. Use recordCacheAccess() for:
 *    - All cache access operations
 *    - Expired entry detection
 *
 * 3. Custom metrics for:
 *    - Cache hit rate
 *    - Memory usage
 *    - Eviction frequency
 *    - Entries by category
 */

export { QueryCacheWithTelemetry };