const { Worker, Queue } = require('bullmq');
const { connectionOptions } = require('../config/bullmq');
const models = require('../models');
const { Op } = require('sequelize');

/**
 * Lesson Data Fill Worker
 * Worker này lấy các lesson từ database và tạo task xử lý dữ liệu lên BullMQ
 * - Liệt kê các từ vựng hoặc ngữ pháp của lesson
 * - Ghi thành task lên BullMQ với label 'process_data'
 */
class LessonDataFillWorker {
  constructor() {
    // Queue để ghi task process_data
    this.processDataQueue = new Queue('process-data', {
      connection: connectionOptions,
      prefix: process.env.BULLMQ_PREFIX || 'vcb',
      defaultJobOptions: {
        attempts: 3,
        backoff: {
          type: 'exponential',
          delay: 2000,
        },
        removeOnComplete: {
          age: 24 * 3600,
          count: 1000,
        },
        removeOnFail: {
          age: 7 * 24 * 3600,
        },
      },
    });

    // Worker để xử lý các lesson
    this.worker = new Worker(
      'lesson-data-fill',
      async (job) => await this.processJob(job),
      {
        connection: connectionOptions,
        prefix: process.env.BULLMQ_PREFIX || 'vcb',
        concurrency: 3,
        limiter: {
          max: 10,
          duration: 1000,
        },
      }
    );

    this.setupEventHandlers();
  }

  /**
   * Process job - Lấy lessons và tạo task xử lý
   */
  async processJob(job) {
    console.log(`[LessonDataFillWorker] Starting job ${job.id}`);
    
    try {
      const { batchSize = 50, offset = 0, filters = {} } = job.data;
      
      // Lấy lessons từ database
      const lessons = await this.getLessons(batchSize, offset, filters);
      
      console.log(`[LessonDataFillWorker] Found ${lessons.length} lessons`);
      
      // Xử lý từng lesson
      const tasks = [];
      for (const lesson of lessons) {
        const taskData = await this.extractLessonData(lesson);
        
        if (taskData) {
          // Tạo task lên BullMQ
          const task = await this.createProcessDataTask(taskData);
          tasks.push(task);
        }
      }
      
      console.log(`[LessonDataFillWorker] ✅ Created ${tasks.length} process_data tasks`);
      
      return {
        success: true,
        lessonsProcessed: lessons.length,
        tasksCreated: tasks.length,
        offset,
        hasMore: lessons.length === batchSize,
      };
      
    } catch (error) {
      console.error(`[LessonDataFillWorker] ❌ Error:`, error.message);
      throw error;
    }
  }

  /**
   * Lấy lessons từ database
   */
  async getLessons(limit, offset, filters) {
    const whereClause = {
      is_published: true,
      lesson_type: 'json_content',
      content_json: {
        [Op.ne]: null,
      },
    };

    // Thêm filters nếu có
    if (filters.lesson_content_type) {
      whereClause.lesson_content_type = filters.lesson_content_type;
    }
    if (filters.chapter_id) {
      whereClause.chapter_id = filters.chapter_id;
    }

    const lessons = await models.Lesson.findAll({
      where: whereClause,
      limit,
      offset,
      order: [['created_at', 'DESC']],
      include: [
        {
          model: models.Chapter,
          as: 'chapter',
          attributes: ['id', 'chapter_number', 'chapter_title', 'subject_id'],
        },
      ],
    });

    return lessons;
  }

  /**
   * Trích xuất dữ liệu từ lesson
   */
  async extractLessonData(lesson) {
    try {
      const contentJson = lesson.content_json;
      
      if (!contentJson || typeof contentJson !== 'object') {
        return null;
      }

      const lessonData = {
        lesson_id: lesson.id,
        lesson_title: lesson.lesson_title,
        lesson_number: lesson.lesson_number,
        lesson_content_type: lesson.lesson_content_type,
        chapter_id: lesson.chapter_id,
        chapter_title: lesson.chapter?.chapter_title,
        vocabularies: [],
        grammars: [],
      };

      // Trích xuất vocabulary IDs
      if (contentJson.vocabulary_ids && Array.isArray(contentJson.vocabulary_ids)) {
        lessonData.vocabularies = contentJson.vocabulary_ids;
        console.log(`[LessonDataFillWorker] Lesson ${lesson.id}: ${lessonData.vocabularies.length} vocabularies`);
      }

      // Trích xuất grammar IDs
      if (contentJson.grammar_ids && Array.isArray(contentJson.grammar_ids)) {
        lessonData.grammars = contentJson.grammar_ids;
        console.log(`[LessonDataFillWorker] Lesson ${lesson.id}: ${lessonData.grammars.length} grammars`);
      }

      // Xử lý review lessons (có thể chứa cả vocab và grammar)
      if (contentJson.sections && Array.isArray(contentJson.sections)) {
        for (const section of contentJson.sections) {
          if (section.vocabulary_ids && Array.isArray(section.vocabulary_ids)) {
            lessonData.vocabularies.push(...section.vocabulary_ids);
          }
          if (section.grammar_ids && Array.isArray(section.grammar_ids)) {
            lessonData.grammars.push(...section.grammar_ids);
          }
        }
        
        // Loại bỏ duplicate IDs
        lessonData.vocabularies = [...new Set(lessonData.vocabularies)];
        lessonData.grammars = [...new Set(lessonData.grammars)];
      }

      // Chỉ return nếu có vocabulary hoặc grammar
      if (lessonData.vocabularies.length > 0 || lessonData.grammars.length > 0) {
        return lessonData;
      }

      return null;
      
    } catch (error) {
      console.error(`[LessonDataFillWorker] Error extracting lesson data:`, error.message);
      return null;
    }
  }

  /**
   * Tạo task process_data lên BullMQ
   */
  async createProcessDataTask(lessonData) {
    try {
      const job = await this.processDataQueue.add(
        'process_data',
        {
          type: 'lesson_data',
          lesson: lessonData,
          timestamp: new Date().toISOString(),
        },
        {
          priority: 5,
          jobId: `lesson-${lessonData.lesson_id}-${Date.now()}`,
        }
      );

      console.log(`[LessonDataFillWorker] ✅ Created task: ${job.id} for lesson ${lessonData.lesson_id}`);
      
      return {
        jobId: job.id,
        lessonId: lessonData.lesson_id,
      };
      
    } catch (error) {
      console.error(`[LessonDataFillWorker] ❌ Error creating task:`, error.message);
      throw error;
    }
  }

  /**
   * Setup event handlers
   */
  setupEventHandlers() {
    this.worker.on('completed', (job) => {
      console.log(`[LessonDataFillWorker] ✅ Job ${job.id} completed`);
    });

    this.worker.on('failed', (job, err) => {
      console.error(`[LessonDataFillWorker] ❌ Job ${job?.id} failed:`, err.message);
    });

    this.worker.on('error', (err) => {
      console.error(`[LessonDataFillWorker] ❌ Worker error:`, err.message);
    });

    this.worker.on('ready', () => {
      console.log('[LessonDataFillWorker] 🚀 Worker ready');
    });

    this.processDataQueue.on('error', (err) => {
      console.error(`[ProcessDataQueue] ❌ Queue error:`, err.message);
    });
  }

  /**
   * Graceful shutdown
   */
  async close() {
    console.log('[LessonDataFillWorker] Closing worker...');
    await this.worker.close();
    await this.processDataQueue.close();
    console.log('[LessonDataFillWorker] Worker closed');
  }
}

// Export class và instance để sử dụng
module.exports = LessonDataFillWorker;

// Nếu chạy trực tiếp file này
if (require.main === module) {
  const worker = new LessonDataFillWorker();
  
  // Graceful shutdown
  process.on('SIGTERM', async () => {
    console.log('SIGTERM received, closing worker...');
    await worker.close();
    process.exit(0);
  });
  
  process.on('SIGINT', async () => {
    console.log('SIGINT received, closing worker...');
    await worker.close();
    process.exit(0);
  });
  
  console.log('🚀 Lesson Data Fill Worker started');
}