# All files / services WhatsAppCloudFAQService.js

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     /**
     * WhatsApp Cloud FAQ Service - Enhanced Version
     * Handles automatic FAQ responses with intelligent matching and learning capabilities
     *
     * Features:
     * - Advanced semantic search with multiple algorithms
     * - Intent detection and context awareness
     * - Machine learning-based improvements
     * - Smart caching and performance optimization
     * - Analytics and user behavior tracking
     *
     * @module services/WhatsAppCloudFAQService
     */

    const WhatsAppCloudFAQ = require('../models/WhatsAppCloudFAQ');
    const { pool } = require('../config/database');
    const { logger } = require('../config/logger');
    const { sendMessage: queueMessage } = require('./MessageService');

    // Cache for frequently accessed data
    const cache = new Map();
    const CACHE_TTL = 5 * 60 * 1000; // 5 minutes

    // Intent patterns for better classification
    const INTENT_PATTERNS = {
      greeting: /^(hi|hello|hey|good morning|good afternoon|good evening|oi|olá|bom dia|boa tarde|boa noite)/i,
      question: /^(what|how|when|where|why|who|qual|como|quando|onde|por que|quem)/i,
      help: /^(help|ajuda|socorro|support|suporte)/i,
      complaint: /^(problem|issue|erro|error|bug|não funciona|not working)/i,
      thanks: /^(thank|obrigad|valeu|thanks)/i,
      goodbye: /^(bye|tchau|goodbye|até logo|see you)/i
    };

    class WhatsAppCloudFAQService {
      /**
       * Check if FAQ tables exist
       * @returns {Promise<boolean>} True if tables exist
       */
      static async checkTablesExist() {
        try {
          const [tables] = await pool.query(`
            SELECT TABLE_NAME
            FROM information_schema.TABLES
            WHERE TABLE_SCHEMA = DATABASE()
            AND TABLE_NAME IN ('whatsapp_cloud_faqs', 'whatsapp_cloud_faq_settings', 'whatsapp_cloud_faq_usage')
          `);
          return tables.length === 3;
        } catch (error) {
          logger.error('Error checking FAQ tables', { error: error.message });
          return false;
        }
      }

      /**
       * Get cached data or fetch from database
       * @param {string} key - Cache key
       * @param {Function} fetchFn - Function to fetch data if not cached
       * @returns {Promise<any>} Cached or fresh data
       */
      static async getCached(key, fetchFn) {
        const cached = cache.get(key);
        if (cached && Date.now() - cached.timestamp < CACHE_TTL) {
          return cached.data;
        }

        const data = await fetchFn();
        cache.set(key, { data, timestamp: Date.now() });
        return data;
      }

      /**
       * Clear cache for specific tenant/account
       * @param {number} tenantId - Tenant ID
       * @param {number} accountId - Account ID
       */
      static clearCache(tenantId, accountId = null) {
        const pattern = `${tenantId}_${accountId || 'null'}`;
        for (const key of cache.keys()) {
          if (key.includes(pattern)) {
            cache.delete(key);
          }
        }
      }

      /**
       * Detect user intent from message
       * @param {string} message - User message
       * @returns {string} Detected intent
       */
      static detectIntent(message) {
        const cleanMessage = message.toLowerCase().trim();

        for (const [intent, pattern] of Object.entries(INTENT_PATTERNS)) {
          if (pattern.test(cleanMessage)) {
            return intent;
          }
        }

        return 'general';
      }

      /**
       * Enhanced message processing with intelligent matching
       * @param {number} tenantId - Tenant ID
       * @param {number} accountId - Account ID
       * @param {number} conversationId - Conversation ID
       * @param {string} messageText - Message text
       * @param {string} contactPhone - Contact phone number
       * @param {Object} context - Additional context (conversation history, user profile, etc.)
       * @returns {Promise<Object>} Processing result with match details
       */
      static async processMessage(tenantId, accountId, conversationId, messageText, contactPhone, context = {}) {
        try {
          // Check if tables exist first
          const tablesExist = await this.checkTablesExist();
          if (!tablesExist) {
            logger.debug('FAQ tables do not exist yet, skipping FAQ processing');
            return { matched: false, reason: 'tables_not_exist' };
          }

          // Get FAQ settings with caching
          const cacheKey = `settings_${tenantId}_${accountId}`;
          const settings = await this.getCached(cacheKey, () =>
            WhatsAppCloudFAQ.getSettings(tenantId, accountId)
          );

          if (!settings.auto_reply_enabled) {
            logger.debug('FAQ auto-reply disabled', { tenantId, accountId });
            return { matched: false, reason: 'disabled' };
          }

          // Detect intent
          const intent = this.detectIntent(messageText);
          logger.debug('Intent detected', { intent, message: messageText });

          // Handle special intents
          if (intent === 'greeting' && settings.welcome_message) {
            await this.sendMessage(tenantId, accountId, contactPhone, settings.welcome_message);
            return { matched: true, type: 'greeting', message: settings.welcome_message };
          }

          if (intent === 'thanks') {
            const thankYouMessage = 'You\'re welcome! 😊 Is there anything else I can help you with?';
            await this.sendMessage(tenantId, accountId, contactPhone, thankYouMessage);
            return { matched: true, type: 'thanks', message: thankYouMessage };
          }

          // Check if message is menu trigger
          const menuKeyword = (settings.menu_trigger_keyword || 'menu').toLowerCase();
          if (messageText.toLowerCase().trim() === menuKeyword && settings.menu_enabled) {
            const menuResult = await this.sendFAQMenu(tenantId, accountId, conversationId, contactPhone);
            return { matched: menuResult, type: 'menu' };
          }

          // Enhanced FAQ search with multiple algorithms
          const searchResult = await this.intelligentSearch(tenantId, accountId, messageText, context);

          if (!searchResult.matches || searchResult.matches.length === 0) {
            // No match found - send contextual no-match message
            if (settings.no_match_message) {
              const contextualMessage = await this.generateContextualNoMatchMessage(
                settings.no_match_message,
                intent,
                messageText
              );
              await this.sendMessage(tenantId, accountId, contactPhone, contextualMessage);
            }

            // Log failed search for learning
            await this.logFailedSearch(tenantId, accountId, conversationId, messageText, intent);

            return { matched: false, reason: 'no_match', intent, searchResult };
          }

          // Use best matching FAQ
          const bestMatch = searchResult.matches[0];

          // Check confidence threshold
          const minConfidence = settings.similarity_threshold || 0.70;
          if (bestMatch.confidence < minConfidence) {
            logger.debug('Match confidence too low', {
              confidence: bestMatch.confidence,
              threshold: minConfidence
            });

            // Suggest alternatives if confidence is moderate
            if (bestMatch.confidence > 0.5) {
              const suggestionMessage = await this.generateSuggestionMessage(searchResult.matches.slice(0, 3));
              await this.sendMessage(tenantId, accountId, contactPhone, suggestionMessage);
              return { matched: true, type: 'suggestion', matches: searchResult.matches.slice(0, 3) };
            }

            return { matched: false, reason: 'low_confidence', confidence: bestMatch.confidence };
          }

          // Send FAQ answer with personalization
          const personalizedAnswer = await this.personalizeAnswer(bestMatch.answer, context);
          await this.sendMessage(tenantId, accountId, contactPhone, personalizedAnswer);

          // Log successful FAQ usage with enhanced data
          await WhatsAppCloudFAQ.logUsage(
            tenantId,
            bestMatch.id,
            conversationId,
            'auto',
            messageText,
            {
              confidence: bestMatch.confidence,
              intent: intent,
              algorithm: searchResult.algorithm,
              context: context
            }
          );

          // Update FAQ performance metrics
          await this.updateFAQMetrics(tenantId, bestMatch.id, bestMatch.confidence, true);

          logger.info('Enhanced FAQ auto-reply sent', {
            tenantId,
            accountId,
            conversationId,
            faqId: bestMatch.id,
            question: bestMatch.question,
            confidence: bestMatch.confidence,
            intent: intent,
            algorithm: searchResult.algorithm
          });

          return {
            matched: true,
            type: 'faq',
            faq: bestMatch,
            confidence: bestMatch.confidence,
            intent: intent,
            algorithm: searchResult.algorithm
          };
        } catch (error) {
          logger.error('Error processing enhanced FAQ auto-reply', {
            tenantId,
            accountId,
            conversationId,
            error: error.message,
            stack: error.stack
          });
          return { matched: false, reason: 'error', error: error.message };
        }
      }

      /**
       * Intelligent search with multiple algorithms
       * @param {number} tenantId - Tenant ID
       * @param {number} accountId - Account ID
       * @param {string} query - Search query
       * @param {Object} context - Search context
       * @returns {Promise<Object>} Search results with confidence scores
       */
      static async intelligentSearch(tenantId, accountId, query, context = {}) {
        try {
          const cacheKey = `faqs_${tenantId}_${accountId}`;
          const faqs = await this.getCached(cacheKey, () =>
            WhatsAppCloudFAQ.getByTenantId(tenantId, accountId, true)
          );

          if (faqs.length === 0) {
            return { matches: [], algorithm: 'none' };
          }

          const cleanQuery = query.toLowerCase().trim();
          const queryWords = cleanQuery.split(/\s+/).filter(word => word.length > 2);

          // Multiple search algorithms
          const algorithms = [
            { name: 'exact_match', weight: 1.0, fn: this.exactMatchSearch },
            { name: 'keyword_match', weight: 0.9, fn: this.keywordMatchSearch },
            { name: 'semantic_similarity', weight: 0.8, fn: this.semanticSimilaritySearch },
            { name: 'fuzzy_match', weight: 0.7, fn: this.fuzzyMatchSearch },
            { name: 'context_aware', weight: 0.85, fn: this.contextAwareSearch }
          ];

          let allMatches = [];

          // Run all algorithms and combine results
          for (const algorithm of algorithms) {
            try {
              const matches = await algorithm.fn.call(this, faqs, cleanQuery, queryWords, context);

              // Apply algorithm weight to confidence scores
              const weightedMatches = matches.map(match => ({
                ...match,
                confidence: match.confidence * algorithm.weight,
                algorithm: algorithm.name
              }));

              allMatches = allMatches.concat(weightedMatches);
            } catch (error) {
              logger.warn(`Algorithm ${algorithm.name} failed`, { error: error.message });
            }
          }

          // Merge and deduplicate matches
          const mergedMatches = this.mergeMatches(allMatches);

          // Sort by confidence and apply learning boost
          const rankedMatches = await this.applyLearningBoost(tenantId, mergedMatches, context);

          // Return top matches
          const topMatches = rankedMatches.slice(0, 5);
          const bestAlgorithm = topMatches.length > 0 ? topMatches[0].algorithm : 'none';

          return {
            matches: topMatches,
            algorithm: bestAlgorithm,
            totalCandidates: allMatches.length,
            query: cleanQuery
          };
        } catch (error) {
          logger.error('Error in intelligent search', { error: error.message });
          return { matches: [], algorithm: 'error' };
        }
      }

      /**
       * Exact match search algorithm
       */
      static async exactMatchSearch(faqs, query, queryWords, context) {
        const matches = [];
        const normalize = (text) => String(text || '')
          .toLowerCase()
          .normalize('NFD')
          .replace(/[\u0300-\u036f]/g, '')
          .replace(/[^a-z0-9\s]/g, ' ')
          .replace(/\s+/g, ' ')
          .trim();
        const escapeRegex = (text) => text.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
        const normalizedQuery = normalize(query);
        const normalizedQueryWords = normalizedQuery.split(' ').filter(Boolean);

        for (const faq of faqs) {
          const question = normalize(faq.question);
          const answer = normalize(faq.answer);

          let confidence = 0;

          // Exact question match
          if (question === normalizedQuery && normalizedQuery) {
            confidence = 1.0;
          }
          // Exact phrase in question
          else if (normalizedQuery && question.includes(normalizedQuery)) {
            confidence = 0.9;
          }
          // Exact words in question
          else if (normalizedQueryWords.length > 0) {
            const allWordsMatch = normalizedQueryWords.every(word => new RegExp(`\\b${escapeRegex(word)}\\b`, 'i').test(question));
            if (allWordsMatch) {
              confidence = normalizedQueryWords.length > 1 ? 0.95 : 0.9;
            }
          }
          // Exact phrase in answer
          else if (normalizedQuery && answer.includes(normalizedQuery)) {
            confidence = 0.7;
          }

          if (confidence > 0) {
            matches.push({
              ...faq,
              confidence,
              matchType: 'exact',
              matchedText: query
            });
          }
        }

        return matches.sort((a, b) => b.confidence - a.confidence);
      }

      /**
       * Keyword match search algorithm
       */
      static async keywordMatchSearch(faqs, query, queryWords, context) {
        const matches = [];

        for (const faq of faqs) {
          const question = faq.question.toLowerCase();
          const answer = faq.answer.toLowerCase();
          const keywords = (faq.keywords || '').toLowerCase();

          let matchedWords = 0;
          let totalWords = queryWords.length;
          let keywordBonus = 0;

          // Count word matches
          for (const word of queryWords) {
            if (question.includes(word) || answer.includes(word)) {
              matchedWords++;
            }
            if (keywords.includes(word)) {
              matchedWords++;
              keywordBonus += 0.1;
            }
          }

          if (matchedWords > 0) {
            const confidence = (matchedWords / totalWords) + keywordBonus;
            matches.push({
              ...faq,
              confidence: Math.min(confidence, 1.0),
              matchType: 'keyword',
              matchedWords: matchedWords,
              totalWords: totalWords
            });
          }
        }

        return matches.sort((a, b) => b.confidence - a.confidence);
      }

      /**
       * Semantic similarity search using enhanced string similarity
       */
      static async semanticSimilaritySearch(faqs, query, queryWords, context) {
        const matches = [];

        for (const faq of faqs) {
          const questionSimilarity = this.calculateAdvancedSimilarity(query, faq.question.toLowerCase());
          const answerSimilarity = this.calculateAdvancedSimilarity(query, faq.answer.toLowerCase()) * 0.7;

          const maxSimilarity = Math.max(questionSimilarity, answerSimilarity);

          if (maxSimilarity > 0.3) {
            matches.push({
              ...faq,
              confidence: maxSimilarity,
              matchType: 'semantic',
              questionSimilarity,
              answerSimilarity
            });
          }
        }

        return matches.sort((a, b) => b.confidence - a.confidence);
      }

      /**
       * Fuzzy match search for typos and variations
       */
      static async fuzzyMatchSearch(faqs, query, queryWords, context) {
        const matches = [];

        for (const faq of faqs) {
          const question = faq.question.toLowerCase();
          const questionWords = question.split(/\s+/);

          let fuzzyScore = 0;
          let matchCount = 0;

          // Check each query word against question words
          for (const queryWord of queryWords) {
            let bestWordScore = 0;

            for (const questionWord of questionWords) {
              const similarity = this.calculateLevenshteinSimilarity(queryWord, questionWord);
              if (similarity > bestWordScore) {
                bestWordScore = similarity;
              }
            }

            if (bestWordScore > 0.7) {
              fuzzyScore += bestWordScore;
              matchCount++;
            }
          }

          if (matchCount > 0) {
            const confidence = (fuzzyScore / queryWords.length) * 0.8; // Reduce confidence for fuzzy matches
            matches.push({
              ...faq,
              confidence,
              matchType: 'fuzzy',
              fuzzyScore,
              matchCount
            });
          }
        }

        return matches.sort((a, b) => b.confidence - a.confidence);
      }

      /**
       * Context-aware search considering conversation history and user profile
       */
      static async contextAwareSearch(faqs, query, queryWords, context) {
        const matches = [];

        // Base keyword search
        const keywordMatches = await this.keywordMatchSearch(faqs, query, queryWords, context);

        for (const match of keywordMatches) {
          let contextBoost = 0;

          // Category preference based on recent interactions
          if (context.preferredCategory && match.category === context.preferredCategory) {
            contextBoost += 0.15;
          }

          // Time-based relevance (recent FAQs get slight boost)
          if (match.last_used_at) {
            const daysSinceUsed = (Date.now() - new Date(match.last_used_at).getTime()) / (1000 * 60 * 60 * 24);
            if (daysSinceUsed < 7) {
              contextBoost += 0.05;
            }
          }

          // Usage frequency boost
          if (match.usage_count > 10) {
            contextBoost += 0.1;
          }

          // Apply context boost
          const boostedConfidence = Math.min(match.confidence + contextBoost, 1.0);

          matches.push({
            ...match,
            confidence: boostedConfidence,
            matchType: 'context_aware',
            contextBoost
          });
        }

        return matches.sort((a, b) => b.confidence - a.confidence);
      }

      /**
       * Merge and deduplicate matches from different algorithms
       */
      static mergeMatches(allMatches) {
        const matchMap = new Map();

        for (const match of allMatches) {
          const key = match.id;

          if (matchMap.has(key)) {
            const existing = matchMap.get(key);
            // Keep the match with higher confidence
            if (match.confidence > existing.confidence) {
              matchMap.set(key, {
                ...match,
                algorithms: [...(existing.algorithms || [existing.algorithm]), match.algorithm]
              });
            } else {
              existing.algorithms = [...(existing.algorithms || [existing.algorithm]), match.algorithm];
            }
          } else {
            matchMap.set(key, match);
          }
        }

        return Array.from(matchMap.values());
      }

      /**
       * Apply machine learning boost based on historical performance
       */
      static async applyLearningBoost(tenantId, matches, context) {
        try {
          // Get FAQ performance metrics
          const performanceData = await this.getFAQPerformanceMetrics(tenantId);

          return matches.map(match => {
            const performance = performanceData.get(match.id);
            let learningBoost = 0;

            if (performance) {
              // Boost based on success rate
              if (performance.success_rate > 0.8) {
                learningBoost += 0.1;
              }

              // Boost based on user satisfaction (if available)
              if (performance.avg_rating > 4.0) {
                learningBoost += 0.05;
              }

              // Penalize frequently rejected FAQs
              if (performance.rejection_rate > 0.3) {
                learningBoost -= 0.1;
              }
            }

            return {
              ...match,
              confidence: Math.max(0, Math.min(1.0, match.confidence + learningBoost)),
              learningBoost
            };
          }).sort((a, b) => b.confidence - a.confidence);
        } catch (error) {
          logger.warn('Error applying learning boost', { error: error.message });
          return matches.sort((a, b) => b.confidence - a.confidence);
        }
      }
      /**
       * Send FAQ menu with enhanced formatting
       * @param {number} tenantId - Tenant ID
       * @param {number} accountId - Account ID
       * @param {number} conversationId - Conversation ID
       * @param {string} contactPhone - Contact phone number
       * @returns {Promise<boolean>} Success status
       */
      static async sendFAQMenu(tenantId, accountId, conversationId, contactPhone) {
        try {
          const settings = await WhatsAppCloudFAQ.getSettings(tenantId, accountId);
          const faqs = await WhatsAppCloudFAQ.getByTenantId(tenantId, accountId, true);

          if (faqs.length === 0) {
            await this.sendMessage(tenantId, accountId, contactPhone, 'No FAQs available at the moment.');
            return false;
          }

          // Build enhanced menu message
          let menuText = settings.menu_header || '📋 *Available Options*\n\nPlease select an option:';
          menuText += '\n\n';

          // Group FAQs by category for better organization
          const categorizedFAQs = this.groupFAQsByCategory(faqs);
          let optionNumber = 1;

          for (const [category, categoryFAQs] of Object.entries(categorizedFAQs)) {
            if (Object.keys(categorizedFAQs).length > 1) {
              menuText += `\n*${this.formatCategoryName(category)}*\n`;
            }

            for (const faq of categoryFAQs.slice(0, 5)) { // Limit to 5 per category
              const emoji = faq.emoji || '▪️';
              menuText += `${emoji} *${optionNumber}.* ${faq.question}\n`;
              optionNumber++;
            }
          }

          menuText += '\n' + (settings.menu_footer || 'Reply with the number of your choice or ask me directly!');

          await this.sendMessage(tenantId, accountId, contactPhone, menuText);

          logger.info('Enhanced FAQ menu sent', {
            tenantId,
            accountId,
            conversationId,
            faqCount: faqs.length,
            categories: Object.keys(categorizedFAQs).length
          });

          return true;
        } catch (error) {
          logger.error('Error sending FAQ menu', {
            tenantId,
            accountId,
            error: error.message
          });
          return false;
        }
      }

      /**
       * Group FAQs by category
       */
      static groupFAQsByCategory(faqs) {
        const grouped = {};

        for (const faq of faqs) {
          const category = faq.category || 'general';
          if (!grouped[category]) {
            grouped[category] = [];
          }
          grouped[category].push(faq);
        }

        // Sort categories by FAQ count
        const sortedCategories = Object.keys(grouped).sort((a, b) =>
          grouped[b].length - grouped[a].length
        );

        const result = {};
        for (const category of sortedCategories) {
          result[category] = grouped[category].sort((a, b) =>
            (b.usage_count || 0) - (a.usage_count || 0)
          );
        }

        return result;
      }

      /**
       * Format category name for display
       */
      static formatCategoryName(category) {
        const categoryNames = {
          general: '📝 General',
          support: '🛠️ Support',
          sales: '💰 Sales',
          billing: '💳 Billing',
          technical: '⚙️ Technical',
          other: '📂 Other'
        };

        return categoryNames[category] || `📁 ${category.charAt(0).toUpperCase() + category.slice(1)}`;
      }

      /**
       * Generate contextual no-match message
       */
      static async generateContextualNoMatchMessage(baseMessage, intent, originalMessage) {
        let contextualMessage = baseMessage;

        // Add intent-specific suggestions
        switch (intent) {
          case 'help':
            contextualMessage += '\n\n💡 Try typing "menu" to see available options, or contact our support team directly.';
            break;
          case 'complaint':
            contextualMessage += '\n\n🔧 For technical issues, please provide more details or contact our technical support team.';
            break;
          case 'question':
            contextualMessage += '\n\n❓ Try rephrasing your question or type "menu" to browse available topics.';
            break;
          default:
            contextualMessage += '\n\n📋 Type "menu" to see available options.';
        }

        return contextualMessage;
      }

      /**
       * Generate suggestion message for moderate confidence matches
       */
      static async generateSuggestionMessage(matches) {
        let message = '🤔 I found some related topics that might help:\n\n';

        matches.forEach((match, index) => {
          const emoji = match.emoji || '▪️';
          message += `${emoji} ${match.question}\n`;
        });

        message += '\n💬 Please let me know which one interests you, or ask your question differently.';

        return message;
      }

      /**
       * Personalize answer based on context
       */
      static async personalizeAnswer(answer, context) {
        let personalizedAnswer = answer;

        // Add user name if available
        if (context.userName) {
          personalizedAnswer = personalizedAnswer.replace(/\{name\}/g, context.userName);
        }

        // Add time-based greetings
        const hour = new Date().getHours();
        if (personalizedAnswer.includes('{greeting}')) {
          let greeting = 'Hello';
          if (hour < 12) greeting = 'Good morning';
          else if (hour < 18) greeting = 'Good afternoon';
          else greeting = 'Good evening';

          personalizedAnswer = personalizedAnswer.replace(/\{greeting\}/g, greeting);
        }

        // Add company name if available
        if (context.companyName) {
          personalizedAnswer = personalizedAnswer.replace(/\{company\}/g, context.companyName);
        }

        return personalizedAnswer;
      }

      /**
       * Log failed search for learning purposes
       */
      static async logFailedSearch(tenantId, accountId, conversationId, query, intent) {
        try {
          await pool.query(
            `INSERT INTO whatsapp_cloud_faq_failed_searches
             (tenant_id, account_id, conversation_id, query, intent, created_at)
             VALUES (?, ?, ?, ?, ?, NOW())
             ON DUPLICATE KEY UPDATE
             search_count = search_count + 1,
             last_searched_at = NOW()`,
            [tenantId, accountId, conversationId, query, intent]
          );
        } catch (error) {
          logger.warn('Error logging failed search', { error: error.message });
        }
      }

      /**
       * Update FAQ performance metrics
       */
      static async updateFAQMetrics(tenantId, faqId, confidence, wasSuccessful) {
        try {
          await pool.query(
            `INSERT INTO whatsapp_cloud_faq_metrics
             (tenant_id, faq_id, total_uses, successful_uses, avg_confidence, last_used_at)
             VALUES (?, ?, 1, ?, ?, NOW())
             ON DUPLICATE KEY UPDATE
             total_uses = total_uses + 1,
             successful_uses = successful_uses + ?,
             avg_confidence = (avg_confidence * (total_uses - 1) + ?) / total_uses,
             last_used_at = NOW()`,
            [tenantId, faqId, wasSuccessful ? 1 : 0, wasSuccessful ? 1 : 0, confidence]
          );
        } catch (error) {
          logger.warn('Error updating FAQ metrics', { error: error.message });
        }
      }

      /**
       * Get FAQ performance metrics for learning
       */
      static async getFAQPerformanceMetrics(tenantId) {
        try {
          const [rows] = await pool.query(
            `SELECT faq_id,
                    (successful_uses / total_uses) as success_rate,
                    avg_confidence,
                    total_uses,
                    successful_uses,
                    ((total_uses - successful_uses) / total_uses) as rejection_rate
             FROM whatsapp_cloud_faq_metrics
             WHERE tenant_id = ? AND total_uses > 0`,
            [tenantId]
          );

          const metricsMap = new Map();
          for (const row of rows) {
            metricsMap.set(row.faq_id, {
              success_rate: row.success_rate,
              avg_confidence: row.avg_confidence,
              total_uses: row.total_uses,
              successful_uses: row.successful_uses,
              rejection_rate: row.rejection_rate,
              avg_rating: 4.0 // Default rating, can be enhanced with user feedback
            });
          }

          return metricsMap;
        } catch (error) {
          logger.warn('Error getting FAQ performance metrics', { error: error.message });
          return new Map();
        }
      }

      /**
       * Advanced similarity calculation with multiple techniques
       */
      static calculateAdvancedSimilarity(str1, str2) {
        if (!str1 || !str2) return 0;

        // Combine multiple similarity algorithms
        const jaccardSim = this.calculateJaccardSimilarity(str1, str2);
        const cosineSim = this.calculateCosineSimilarity(str1, str2);
        const bigramSim = this.calculateSimilarity(str1, str2); // Original bigram similarity

        // Weighted combination
        return (jaccardSim * 0.3) + (cosineSim * 0.4) + (bigramSim * 0.3);
      }

      /**
       * Jaccard similarity for set-based comparison
       */
      static calculateJaccardSimilarity(str1, str2) {
        const set1 = new Set(str1.toLowerCase().split(/\s+/));
        const set2 = new Set(str2.toLowerCase().split(/\s+/));

        const intersection = new Set([...set1].filter(x => set2.has(x)));
        const union = new Set([...set1, ...set2]);

        return intersection.size / union.size;
      }

      /**
       * Cosine similarity for vector-based comparison
       */
      static calculateCosineSimilarity(str1, str2) {
        const words1 = str1.toLowerCase().split(/\s+/);
        const words2 = str2.toLowerCase().split(/\s+/);

        // Create word frequency vectors
        const allWords = [...new Set([...words1, ...words2])];
        const vector1 = allWords.map(word => words1.filter(w => w === word).length);
        const vector2 = allWords.map(word => words2.filter(w => w === word).length);

        // Calculate cosine similarity
        const dotProduct = vector1.reduce((sum, val, i) => sum + val * vector2[i], 0);
        const magnitude1 = Math.sqrt(vector1.reduce((sum, val) => sum + val * val, 0));
        const magnitude2 = Math.sqrt(vector2.reduce((sum, val) => sum + val * val, 0));

        if (magnitude1 === 0 || magnitude2 === 0) return 0;

        return dotProduct / (magnitude1 * magnitude2);
      }

      /**
       * Levenshtein distance-based similarity
       */
      static calculateLevenshteinSimilarity(str1, str2) {
        const distance = this.levenshteinDistance(str1, str2);
        const maxLength = Math.max(str1.length, str2.length);

        if (maxLength === 0) return 1;

        return 1 - (distance / maxLength);
      }

      /**
       * Calculate Levenshtein distance
       */
      static levenshteinDistance(str1, str2) {
        const matrix = [];

        for (let i = 0; i <= str2.length; i++) {
          matrix[i] = [i];
        }

        for (let j = 0; j <= str1.length; j++) {
          matrix[0][j] = j;
        }

        for (let i = 1; i <= str2.length; i++) {
          for (let j = 1; j <= str1.length; j++) {
            if (str2.charAt(i - 1) === str1.charAt(j - 1)) {
              matrix[i][j] = matrix[i - 1][j - 1];
            } else {
              matrix[i][j] = Math.min(
                matrix[i - 1][j - 1] + 1,
                matrix[i][j - 1] + 1,
                matrix[i - 1][j] + 1
              );
            }
          }
        }

        return matrix[str2.length][str1.length];
      }

      /**
       * Send WhatsApp message with improved account handling
       * @param {number} tenantId - Tenant ID
       * @param {number} accountId - Account ID (can be null)
       * @param {string} to - Recipient phone number
       * @param {string} message - Message text
       * @returns {Promise<boolean>} Success status
       */
      static async sendMessage(tenantId, accountId, to, message) {
        try {
          let account;

          if (accountId) {
            // Get specific account
            const [accounts] = await pool.execute(
              'SELECT * FROM whatsapp_cloud_accounts WHERE id = ? AND tenant_id = ?',
              [accountId, tenantId]
            );

            if (accounts.length === 0) {
              throw new Error(`Account ${accountId} not found for tenant ${tenantId}`);
            }

            account = accounts[0];
          } else {
            // Get default account for tenant
            const [accounts] = await pool.execute(
              'SELECT * FROM whatsapp_cloud_accounts WHERE tenant_id = ? AND (is_default = TRUE OR is_default IS NULL) ORDER BY is_default DESC, id ASC LIMIT 1',
              [tenantId]
            );

            if (accounts.length === 0) {
              throw new Error(`No WhatsApp Cloud account found for tenant ${tenantId}`);
            }

            account = accounts[0];
            logger.debug('Using default account for FAQ', {
              tenantId,
              accountId: account.id,
              accountName: account.account_name
            });
          }

          const normalizedTo = String(to || '').trim().replace(/[^\d]/g, '');
          if (!normalizedTo) {
            throw new Error('Invalid destination phone number');
          }
          const sendResult = await queueMessage({
            channel: 'cloud',
            tenantId,
            accountId: account.id,
            to: normalizedTo,
            messageType: 'text',
            content: message,
            awaitSend: true
          });

          if (!sendResult.success) {
            throw new Error(sendResult.error || 'Failed to send FAQ message');
          }

          logger.info('FAQ message sent successfully', {
            tenantId,
            accountId: account.id,
            accountName: account.account_name,
            to: normalizedTo,
            messageId: sendResult.messageId || null
          });

          return true;
        } catch (error) {
          logger.error('Error sending FAQ message', {
            tenantId,
            accountId,
            to,
            error: error.message,
            response: error.response?.data
          });
          return false;
        }
      }

      /**
       * Calculate similarity between two strings (simple implementation)
       * @param {string} str1 - First string
       * @param {string} str2 - Second string
       * @returns {number} Similarity score (0-1)
       */
      static calculateSimilarity(str1, str2) {
        const s1 = str1.toLowerCase().trim();
        const s2 = str2.toLowerCase().trim();

        if (s1 === s2) return 1;
        if (s1.length < 2 || s2.length < 2) return 0;

        const firstBigrams = new Map();
        for (let i = 0; i < s1.length - 1; i++) {
          const bigram = s1.substring(i, i + 2);
          const count = firstBigrams.has(bigram) ? firstBigrams.get(bigram) + 1 : 1;
          firstBigrams.set(bigram, count);
        }

        let intersectionSize = 0;
        for (let i = 0; i < s2.length - 1; i++) {
          const bigram = s2.substring(i, i + 2);
          const count = firstBigrams.has(bigram) ? firstBigrams.get(bigram) : 0;

          if (count > 0) {
            firstBigrams.set(bigram, count - 1);
            intersectionSize++;
          }
        }

        return (2.0 * intersectionSize) / (s1.length + s2.length - 2);
      }
    }

    module.exports = WhatsAppCloudFAQService;