# All files / framework/query QueryCache.ts

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     import { QueryBuilder } from './QueryBuilder';
    import { BaseModel } from '../models/BaseModel';

    export interface CacheEntry<T> {
      key: string;
      data: T[];
      timestamp: number;
      ttl: number;
      hitCount: number;
    }

    export interface CacheStats {
      totalRequests: number;
      cacheHits: number;
      cacheMisses: number;
      hitRate: number;
      size: number;
      maxSize: number;
    }

    export class QueryCache {
      private cache: Map<string, CacheEntry<any>> = new Map();
      private maxSize: number;
      private defaultTTL: number;
      private stats: CacheStats;

      constructor(maxSize: number = 1000, defaultTTL: number = 300000) {
        // 5 minutes default
        this.maxSize = maxSize;
        this.defaultTTL = defaultTTL;
        this.stats = {
          totalRequests: 0,
          cacheHits: 0,
          cacheMisses: 0,
          hitRate: 0,
          size: 0,
          maxSize,
        };
      }

      generateKey<T extends BaseModel>(query: QueryBuilder<T>): string {
        const model = query.getModel();
        const conditions = query.getConditions();
        const relations = query.getRelations();
        const sorting = query.getSorting();
        const limit = query.getLimit();
        const offset = query.getOffset();

        // Create a deterministic cache key
        const keyParts = [
          model.name,
          model.scope,
          JSON.stringify(conditions.sort((a, b) => a.field.localeCompare(b.field))),
          JSON.stringify(relations.sort()),
          JSON.stringify(sorting),
          limit?.toString() || 'no-limit',
          offset?.toString() || 'no-offset',
        ];

        // Create hash of the key parts
        return this.hashString(keyParts.join('|'));
      }

      async get<T extends BaseModel>(query: QueryBuilder<T>): Promise<T[] | null> {
        this.stats.totalRequests++;

        const key = this.generateKey(query);
        const entry = this.cache.get(key);

        if (!entry) {
          this.stats.cacheMisses++;
          this.updateHitRate();
          return null;
        }

        // Check if entry has expired
        if (Date.now() - entry.timestamp > entry.ttl) {
          this.cache.delete(key);
          this.stats.cacheMisses++;
          this.updateHitRate();
          return null;
        }

        // Update hit count and stats
        entry.hitCount++;
        this.stats.cacheHits++;
        this.updateHitRate();

        // Convert cached data back to model instances
        const modelClass = query.getModel() as any; // Type assertion for abstract class
        return entry.data.map((item) => new modelClass(item));
      }

      set<T extends BaseModel>(query: QueryBuilder<T>, data: T[], customTTL?: number): void {
        const key = this.generateKey(query);
        const ttl = customTTL || this.defaultTTL;

        // Serialize model instances to plain objects for caching
        const serializedData = data.map((item) => item.toJSON());

        const entry: CacheEntry<any> = {
          key,
          data: serializedData,
          timestamp: Date.now(),
          ttl,
          hitCount: 0,
        };

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

        this.cache.set(key, entry);
        this.stats.size = this.cache.size;
      }

      invalidate<T extends BaseModel>(query: QueryBuilder<T>): boolean {
        const key = this.generateKey(query);
        const deleted = this.cache.delete(key);
        this.stats.size = this.cache.size;
        return deleted;
      }

      invalidateByModel(modelName: string): number {
        let deletedCount = 0;

        for (const [key, _entry] of this.cache.entries()) {
          if (key.startsWith(this.hashString(modelName))) {
            this.cache.delete(key);
            deletedCount++;
          }
        }

        this.stats.size = this.cache.size;
        return deletedCount;
      }

      invalidateByUser(userId: string): number {
        let deletedCount = 0;

        for (const [key, entry] of this.cache.entries()) {
          // Check if the cached entry contains user-specific data
          if (this.entryContainsUser(entry, userId)) {
            this.cache.delete(key);
            deletedCount++;
          }
        }

        this.stats.size = this.cache.size;
        return deletedCount;
      }

      clear(): void {
        this.cache.clear();
        this.stats.size = 0;
        this.stats.totalRequests = 0;
        this.stats.cacheHits = 0;
        this.stats.cacheMisses = 0;
        this.stats.hitRate = 0;
      }

      getStats(): CacheStats {
        return { ...this.stats };
      }

      // Cache warming - preload frequently used queries
      async warmup<T extends BaseModel>(queries: QueryBuilder<T>[]): Promise<void> {
        console.log(`🔥 Warming up cache with ${queries.length} queries...`);

        const promises = queries.map(async (query) => {
          try {
            const results = await query.exec();
            this.set(query, results);
            console.log(`✓ Cached query for ${query.getModel().name}`);
          } catch (error) {
            console.warn(`Failed to warm cache for ${query.getModel().name}:`, error);
          }
        });

        await Promise.all(promises);
        console.log(`✅ Cache warmup completed`);
      }

      // Get cache entries sorted by various criteria
      getPopularEntries(limit: number = 10): Array<{ key: string; hitCount: number; age: number }> {
        return Array.from(this.cache.entries())
          .map(([key, entry]) => ({
            key,
            hitCount: entry.hitCount,
            age: Date.now() - entry.timestamp,
          }))
          .sort((a, b) => b.hitCount - a.hitCount)
          .slice(0, limit);
      }

      getExpiredEntries(): string[] {
        const now = Date.now();
        const expired: string[] = [];

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

        return expired;
      }

      // Cleanup expired entries
      cleanup(): number {
        const expired = this.getExpiredEntries();

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

        this.stats.size = this.cache.size;
        return expired.length;
      }

      // Configure cache behavior
      setMaxSize(size: number): void {
        this.maxSize = size;
        this.stats.maxSize = size;

        // Evict entries if current size exceeds new max
        while (this.cache.size > size) {
          this.evictLeastUsed();
        }
      }

      setDefaultTTL(ttl: number): void {
        this.defaultTTL = ttl;
      }

      // Cache analysis
      analyzeUsage(): {
        totalEntries: number;
        averageHitCount: number;
        averageAge: number;
        memoryUsage: number;
      } {
        const entries = Array.from(this.cache.values());
        const now = Date.now();

        const totalHits = entries.reduce((sum, entry) => sum + entry.hitCount, 0);
        const totalAge = entries.reduce((sum, entry) => sum + (now - entry.timestamp), 0);

        // Rough memory usage estimation
        const memoryUsage = entries.reduce((sum, entry) => {
          return sum + JSON.stringify(entry.data).length;
        }, 0);

        return {
          totalEntries: entries.length,
          averageHitCount: entries.length > 0 ? totalHits / entries.length : 0,
          averageAge: entries.length > 0 ? totalAge / entries.length : 0,
          memoryUsage,
        };
      }

      private evictLeastUsed(): void {
        if (this.cache.size === 0) return;

        // Find entry with lowest hit count and oldest timestamp
        let leastUsedKey: string | null = null;
        let leastUsedScore = Infinity;

        for (const [key, entry] of this.cache.entries()) {
          // Score based on hit count and age (lower is worse)
          const age = Date.now() - entry.timestamp;
          const score = entry.hitCount - age / 1000000; // Age penalty

          if (score < leastUsedScore) {
            leastUsedScore = score;
            leastUsedKey = key;
          }
        }

        if (leastUsedKey) {
          this.cache.delete(leastUsedKey);
          this.stats.size = this.cache.size;
        }
      }

      private entryContainsUser(entry: CacheEntry<any>, userId: string): boolean {
        // Check if the cached data contains user-specific information
        try {
          const dataStr = JSON.stringify(entry.data);
          return dataStr.includes(userId);
        } catch {
          return false;
        }
      }

      private updateHitRate(): void {
        if (this.stats.totalRequests > 0) {
          this.stats.hitRate = this.stats.cacheHits / this.stats.totalRequests;
        }
      }

      private hashString(str: string): string {
        let hash = 0;
        if (str.length === 0) return hash.toString();

        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
        }

        return Math.abs(hash).toString(36);
      }
    }