Design Patterns MCP Server

/** * Factory Pattern for Embedding Strategy Creation * Creates appropriate embedding strategies based on configuration and availability */ import { EmbeddingStrategy, SimpleHashEmbeddingStrategy, TransformersEmbeddingStrategy, OllamaEmbeddingStrategy, } from '../strategies/embedding-strategy.js'; interface EmbeddingFactoryConfig { preferredStrategy?: 'transformers' | 'ollama' | 'simple-hash'; ollamaBaseUrl?: string; fallbackToSimple?: boolean; enableLogging?: boolean; } export class EmbeddingStrategyFactory { private static instance: EmbeddingStrategyFactory; private strategies: Map<string, EmbeddingStrategy> = new Map(); private config: EmbeddingFactoryConfig; private constructor(config: EmbeddingFactoryConfig = {}) { this.config = { preferredStrategy: 'transformers', fallbackToSimple: true, enableLogging: false, ...config, }; } /** * Singleton pattern for factory instance */ static getInstance(config?: EmbeddingFactoryConfig): EmbeddingStrategyFactory { if (!EmbeddingStrategyFactory.instance) { EmbeddingStrategyFactory.instance = new EmbeddingStrategyFactory(config); } return EmbeddingStrategyFactory.instance; } /** * Create and return the best available embedding strategy */ async createStrategy(): Promise<EmbeddingStrategy> { const cacheKey = `${this.config.preferredStrategy}_${this.config.ollamaBaseUrl}`; // Return cached strategy if available const cachedStrategy = this.strategies.get(cacheKey); if (cachedStrategy && (await cachedStrategy.isAvailable())) { return cachedStrategy; } else if (cachedStrategy) { // Remove unavailable strategy from cache this.strategies.delete(cacheKey); } // Try preferred strategy first let strategy = this.tryCreatePreferredStrategy(); if (strategy && (await strategy.isAvailable())) { this.strategies.set(cacheKey, strategy); this.log(`Using ${strategy.name} embedding strategy`); return strategy; } // Fallback chain const fallbackStrategies = this.getFallbackOrder(); for (const strategyType of fallbackStrategies) { strategy = this.createSpecificStrategy(strategyType); if (strategy && (await strategy.isAvailable())) { this.strategies.set(cacheKey, strategy); this.log(`Falling back to ${strategy.name} embedding strategy`); return strategy; } } // Final fallback to simple hash if enabled if (this.config.fallbackToSimple) { strategy = new SimpleHashEmbeddingStrategy(); this.strategies.set(cacheKey, strategy); this.log('Using simple hash embedding strategy as final fallback'); return strategy; } throw new Error('No embedding strategy available'); } /** * Create specific strategy by type */ createSpecificStrategy(type: string): EmbeddingStrategy | null { switch (type) { case 'transformers': return new TransformersEmbeddingStrategy(); case 'ollama': return new OllamaEmbeddingStrategy(this.config.ollamaBaseUrl); case 'simple-hash': return new SimpleHashEmbeddingStrategy(); default: return null; } } /** * Get all available strategies with their status */ async getAvailableStrategies(): Promise< Array<{ name: string; available: boolean; model: string }> > { const strategies = [ new TransformersEmbeddingStrategy(), new OllamaEmbeddingStrategy(this.config.ollamaBaseUrl), new SimpleHashEmbeddingStrategy(), ]; const results = await Promise.all( strategies.map(async strategy => ({ name: strategy.name, available: await strategy.isAvailable(), model: strategy.model, })) ); return results; } /** * Clear strategy cache (useful for testing or configuration changes) */ clearCache(): void { this.strategies.clear(); } /** * Update factory configuration */ updateConfig(newConfig: Partial<EmbeddingFactoryConfig>): void { this.config = { ...this.config, ...newConfig }; this.clearCache(); // Clear cache when config changes } private tryCreatePreferredStrategy(): EmbeddingStrategy | null { if (!this.config.preferredStrategy) return null; return this.createSpecificStrategy(this.config.preferredStrategy); } private getFallbackOrder(): string[] { const { preferredStrategy } = this.config; const allStrategies = ['transformers', 'ollama', 'simple-hash']; // Remove preferred strategy from fallbacks to avoid duplication return allStrategies.filter(s => s !== preferredStrategy); } private log(message: string): void { if (this.config.enableLogging) { console.log(`[EmbeddingFactory] ${message}`); } } } // Note: createEmbeddingStrategy function removed as it was unused /** * Convenience function to check available strategies */ export async function getAvailableEmbeddingStrategies( config?: EmbeddingFactoryConfig ): Promise<Array<{ name: string; available: boolean; model: string }>> { const factory = EmbeddingStrategyFactory.getInstance(config); return factory.getAvailableStrategies(); }