const { Queue, Worker } = require('bullmq');
const Redis = require('ioredis');
const config = require('./config.json');

/**
 * BullMQ Connection Configuration - Direct Redis connection
 */
const redisConfig = config.redis;

// Connection options for BullMQ (BullMQ will create connections using these options)
const connectionOptions = {
  host: redisConfig.cluster[0].host,
  port: redisConfig.cluster[0].port,
  password: redisConfig.password,
  db: redisConfig.db,
  maxRetriesPerRequest: null,
  enableReadyCheck: false,
};

// Create a shared Redis connection for direct Redis operations
const bullMQConnection = new Redis(connectionOptions);

console.log('📊 BullMQ Redis Connection:', {
  host: connectionOptions.host,
  port: connectionOptions.port,
  db: connectionOptions.db,
});

bullMQConnection.on('connect', () => {
  console.log('✅ BullMQ Redis connected');
});

bullMQConnection.on('error', (err) => {
  console.error('❌ BullMQ Redis error:', err.message);
});

/**
 * Default job options
 */
const defaultJobOptions = {
  attempts: 3,
  backoff: {
    type: 'exponential',
    delay: 2000,
  },
  removeOnComplete: {
    age: 24 * 3600, // Keep completed jobs for 24 hours
    count: 1000,
  },
  removeOnFail: {
    age: 7 * 24 * 3600, // Keep failed jobs for 7 days
  },
};

/**
 * Queue definitions for different operations
 */
const QueueNames = {
  DATABASE_WRITE: 'database-write',
  NOTIFICATION: 'notification',
  ATTENDANCE_PROCESS: 'attendance-process',
  GRADE_CALCULATION: 'grade-calculation',
  REPORT_GENERATION: 'report-generation',
};

/**
 * Create queues with connection options
 */
const queues = {};

Object.values(QueueNames).forEach(queueName => {
  queues[queueName] = new Queue(queueName, {
    connection: connectionOptions,  // Use connection options, not instance
    prefix: process.env.BULLMQ_PREFIX || 'vcb',
    defaultJobOptions,
  });
  
  queues[queueName].on('error', (error) => {
    console.error(`❌ Queue ${queueName} error:`, error.message);
  });
  
  console.log(`✅ Queue ${queueName} initialized`);
});

/**
 * Add job to database write queue
 * @param {string} operation - Operation type: 'create', 'update', 'delete'
 * @param {string} model - Model name
 * @param {object} data - Data to be written
 * @param {object} options - Additional options
 */
const addDatabaseWriteJob = async (operation, model, data, options = {}) => {
  try {
    const job = await queues[QueueNames.DATABASE_WRITE].add(
      `${operation}-${model}`,
      {
        operation,
        model,
        data,
        timestamp: new Date().toISOString(),
        userId: options.userId,
        ...options,
      },
      {
        priority: options.priority || 5,
        delay: options.delay || 0,
      }
    );
    
    console.log(`✅ Database write job added: ${job.id} (${operation} ${model})`);
    return job;
  } catch (error) {
    console.error(`❌ Error adding database write job:`, error.message);
    throw error;
  }
};

/**
 * Add notification job
 */
const addNotificationJob = async (type, recipients, content, options = {}) => {
  try {
    const job = await queues[QueueNames.NOTIFICATION].add(
      `send-${type}`,
      {
        type,
        recipients,
        content,
        timestamp: new Date().toISOString(),
        ...options,
      },
      {
        priority: options.priority || 5,
      }
    );
    
    console.log(`✅ Notification job added: ${job.id}`);
    return job;
  } catch (error) {
    console.error(`❌ Error adding notification job:`, error.message);
    throw error;
  }
};

/**
 * Add attendance processing job
 */
const addAttendanceProcessJob = async (schoolId, date, options = {}) => {
  try {
    const job = await queues[QueueNames.ATTENDANCE_PROCESS].add(
      'process-attendance',
      {
        schoolId,
        date,
        timestamp: new Date().toISOString(),
        ...options,
      },
      {
        priority: options.priority || 3,
      }
    );
    
    console.log(`✅ Attendance process job added: ${job.id}`);
    return job;
  } catch (error) {
    console.error(`❌ Error adding attendance process job:`, error.message);
    throw error;
  }
};

/**
 * Add grade calculation job
 */
const addGradeCalculationJob = async (studentId, academicYearId, options = {}) => {
  try {
    const job = await queues[QueueNames.GRADE_CALCULATION].add(
      'calculate-grades',
      {
        studentId,
        academicYearId,
        timestamp: new Date().toISOString(),
        ...options,
      },
      {
        priority: options.priority || 4,
      }
    );
    
    console.log(`✅ Grade calculation job added: ${job.id}`);
    return job;
  } catch (error) {
    console.error(`❌ Error adding grade calculation job:`, error.message);
    throw error;
  }
};

/**
 * Get queue metrics
 */
const getQueueMetrics = async (queueName) => {
  try {
    const queue = queues[queueName];
    if (!queue) {
      throw new Error(`Queue ${queueName} not found`);
    }
    
    const [waiting, active, completed, failed, delayed] = await Promise.all([
      queue.getWaitingCount(),
      queue.getActiveCount(),
      queue.getCompletedCount(),
      queue.getFailedCount(),
      queue.getDelayedCount(),
    ]);
    
    return {
      queueName,
      waiting,
      active,
      completed,
      failed,
      delayed,
      total: waiting + active + completed + failed + delayed,
    };
  } catch (error) {
    console.error(`❌ Error getting queue metrics:`, error.message);
    throw error;
  }
};

/**
 * Close all queues
 */
const closeQueues = async () => {
  try {
    await Promise.all(
      Object.values(queues).map(queue => queue.close())
    );
    console.log('✅ All BullMQ queues closed');
  } catch (error) {
    console.error('❌ Error closing queues:', error.message);
  }
};

module.exports = {
  queues,
  QueueNames,
  addDatabaseWriteJob,
  addNotificationJob,
  addAttendanceProcessJob,
  addGradeCalculationJob,
  getQueueMetrics,
  closeQueues,
  bullMQConnection,
  connectionOptions,
  defaultJobOptions,
};