import { Injectable, Logger } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository, Between, MoreThanOrEqual, LessThanOrEqual } from 'typeorm';
import { Cron, CronExpression } from '@nestjs/schedule';

import { AnalyticsRecord } from '@database/entities/analytics-record.entity';
import { AnalyticsSummary } from '@database/entities/analytics-summary.entity';
import { AnalyticsQueryDto, CreateAnalyticsRecordDto } from '../dto/analytics-query.dto';

@Injectable()
export class AnalyticsService {
  private readonly logger = new Logger(AnalyticsService.name);

  constructor(
    @InjectRepository(AnalyticsRecord)
    private readonly analyticsRecordRepository: Repository<AnalyticsRecord>,
    @InjectRepository(AnalyticsSummary)
    private readonly analyticsSummaryRepository: Repository<AnalyticsSummary>,
  ) {}

  /**
   * 记录分析事件
   */
  async recordEvent(createDto: CreateAnalyticsRecordDto, request?: any): Promise<AnalyticsRecord> {
    const now = new Date();
    
    const record = this.analyticsRecordRepository.create({
      ...createDto,
      timestamp: now,
      date: new Date(now.getFullYear(), now.getMonth(), now.getDate()),
      ipAddress: request?.ip,
      userAgent: request?.headers?.['user-agent'],
      sessionId: request?.headers?.['x-session-id'],
      requestId: request?.headers?.['x-request-id'],
    });

    const savedRecord = await this.analyticsRecordRepository.save(record);
    this.logger.debug(`记录分析事件: ${createDto.eventType} - ${createDto.eventName}`);
    
    return savedRecord;
  }

  /**
   * 批量记录事件
   */
  async recordEvents(events: CreateAnalyticsRecordDto[], request?: any): Promise<AnalyticsRecord[]> {
    const now = new Date();
    const date = new Date(now.getFullYear(), now.getMonth(), now.getDate());
    
    const records = events.map(event => 
      this.analyticsRecordRepository.create({
        ...event,
        timestamp: now,
        date,
        ipAddress: request?.ip,
        userAgent: request?.headers?.['user-agent'],
        sessionId: request?.headers?.['x-session-id'],
        requestId: request?.headers?.['x-request-id'],
      })
    );

    const savedRecords = await this.analyticsRecordRepository.save(records);
    this.logger.debug(`批量记录分析事件: ${events.length} 个`);
    
    return savedRecords;
  }

  /**
   * 查询分析数据
   */
  async queryAnalytics(queryDto: AnalyticsQueryDto): Promise<any> {
    const {
      metricType,
      entityType,
      entityId,
      startDate,
      endDate,
      period = 'day',
      groupBy,
      aggregation = 'count',
      limit = 1000,
    } = queryDto;

    // 构建查询条件
    const whereConditions: any = {
      eventName: metricType,
      timestamp: Between(new Date(startDate), new Date(endDate)),
    };

    if (entityType) {
      whereConditions.entityType = entityType;
    }

    if (entityId) {
      whereConditions.entityId = entityId;
    }

    // 如果有预计算的汇总数据，优先使用
    if (!groupBy && period && ['day', 'week', 'month'].includes(period)) {
      const summaryData = await this.querySummaryData(queryDto);
      if (summaryData.length > 0) {
        return this.formatSummaryData(summaryData, period);
      }
    }

    // 实时查询原始数据
    return await this.queryRawData(queryDto);
  }

  /**
   * 查询汇总数据
   */
  private async querySummaryData(queryDto: AnalyticsQueryDto): Promise<AnalyticsSummary[]> {
    const {
      metricType,
      entityType,
      entityId,
      startDate,
      endDate,
      period,
    } = queryDto;

    const whereConditions: any = {
      metricType,
      period,
      date: Between(new Date(startDate), new Date(endDate)),
    };

    if (entityType) {
      whereConditions.entityType = entityType;
    }

    if (entityId) {
      whereConditions.entityId = entityId;
    }

    return await this.analyticsSummaryRepository.find({
      where: whereConditions,
      order: { date: 'ASC' },
    });
  }

  /**
   * 查询原始数据
   */
  private async queryRawData(queryDto: AnalyticsQueryDto): Promise<any> {
    const {
      metricType,
      entityType,
      entityId,
      startDate,
      endDate,
      groupBy,
      aggregation,
      limit,
    } = queryDto;

    const queryBuilder = this.analyticsRecordRepository.createQueryBuilder('record');

    // 基础条件
    queryBuilder
      .where('record.eventName = :metricType', { metricType })
      .andWhere('record.timestamp BETWEEN :startDate AND :endDate', {
        startDate: new Date(startDate),
        endDate: new Date(endDate),
      });

    if (entityType) {
      queryBuilder.andWhere('record.entityType = :entityType', { entityType });
    }

    if (entityId) {
      queryBuilder.andWhere('record.entityId = :entityId', { entityId });
    }

    // 分组和聚合
    if (groupBy && groupBy.length > 0) {
      const groupFields = groupBy.map(field => `record.${field}`);
      queryBuilder.groupBy(groupFields.join(', '));
      
      groupFields.forEach(field => {
        queryBuilder.addSelect(field);
      });

      // 聚合函数
      switch (aggregation) {
        case 'count':
          queryBuilder.addSelect('COUNT(*)', 'value');
          break;
        case 'sum':
          queryBuilder.addSelect('SUM(record.value)', 'value');
          break;
        case 'avg':
          queryBuilder.addSelect('AVG(record.value)', 'value');
          break;
        case 'min':
          queryBuilder.addSelect('MIN(record.value)', 'value');
          break;
        case 'max':
          queryBuilder.addSelect('MAX(record.value)', 'value');
          break;
      }
    } else {
      // 时间序列聚合
      queryBuilder
        .select('DATE(record.timestamp)', 'date')
        .addSelect('COUNT(*)', 'count')
        .addSelect('AVG(record.value)', 'avgValue')
        .addSelect('SUM(record.value)', 'sumValue')
        .groupBy('DATE(record.timestamp)')
        .orderBy('date', 'ASC');
    }

    queryBuilder.limit(limit);

    return await queryBuilder.getRawMany();
  }

  /**
   * 格式化汇总数据
   */
  private formatSummaryData(summaries: AnalyticsSummary[], period: string): any {
    return summaries.map(summary => ({
      date: summary.date,
      period,
      totalCount: summary.totalCount,
      successCount: summary.successCount,
      failureCount: summary.failureCount,
      totalValue: summary.totalValue,
      averageValue: summary.averageValue,
      minValue: summary.minValue,
      maxValue: summary.maxValue,
      metrics: summary.metrics,
      dimensions: summary.dimensions,
    }));
  }

  /**
   * 获取实时指标
   */
  async getRealtimeMetrics(): Promise<any> {
    const now = new Date();
    const oneHourAgo = new Date(now.getTime() - 60 * 60 * 1000);
    const oneDayAgo = new Date(now.getTime() - 24 * 60 * 60 * 1000);

    const [
      lastHourEvents,
      lastDayEvents,
      topEvents,
      errorEvents,
    ] = await Promise.all([
      this.analyticsRecordRepository.count({
        where: { timestamp: MoreThanOrEqual(oneHourAgo) },
      }),
      this.analyticsRecordRepository.count({
        where: { timestamp: MoreThanOrEqual(oneDayAgo) },
      }),
      this.getTopEvents(10),
      this.analyticsRecordRepository.count({
        where: { 
          eventType: 'error_event',
          timestamp: MoreThanOrEqual(oneDayAgo),
        },
      }),
    ]);

    return {
      lastHourEvents,
      lastDayEvents,
      topEvents,
      errorEvents,
      timestamp: now,
    };
  }

  /**
   * 获取热门事件
   */
  async getTopEvents(limit: number = 10): Promise<any[]> {
    const oneDayAgo = new Date(Date.now() - 24 * 60 * 60 * 1000);

    return await this.analyticsRecordRepository
      .createQueryBuilder('record')
      .select('record.eventName', 'eventName')
      .addSelect('record.eventType', 'eventType')
      .addSelect('COUNT(*)', 'count')
      .where('record.timestamp >= :oneDayAgo', { oneDayAgo })
      .groupBy('record.eventName, record.eventType')
      .orderBy('count', 'DESC')
      .limit(limit)
      .getRawMany();
  }

  /**
   * 获取用户活动分析
   */
  async getUserActivityAnalytics(
    startDate: string, 
    endDate: string, 
    userId?: number
  ): Promise<any> {
    const queryBuilder = this.analyticsRecordRepository.createQueryBuilder('record');

    queryBuilder
      .select('DATE(record.timestamp)', 'date')
      .addSelect('COUNT(DISTINCT record.userId)', 'activeUsers')
      .addSelect('COUNT(*)', 'totalEvents')
      .addSelect('record.eventType', 'eventType')
      .where('record.timestamp BETWEEN :startDate AND :endDate', {
        startDate: new Date(startDate),
        endDate: new Date(endDate),
      })
      .andWhere('record.eventType = :eventType', { eventType: 'user_action' });

    if (userId) {
      queryBuilder.andWhere('record.userId = :userId', { userId });
    }

    queryBuilder
      .groupBy('DATE(record.timestamp), record.eventType')
      .orderBy('date', 'ASC');

    return await queryBuilder.getRawMany();
  }

  /**
   * 获取性能指标分析
   */
  async getPerformanceAnalytics(
    startDate: string, 
    endDate: string, 
    metricName?: string
  ): Promise<any> {
    const queryBuilder = this.analyticsRecordRepository.createQueryBuilder('record');

    queryBuilder
      .select('DATE(record.timestamp)', 'date')
      .addSelect('record.eventName', 'metricName')
      .addSelect('AVG(record.value)', 'averageValue')
      .addSelect('MIN(record.value)', 'minValue')
      .addSelect('MAX(record.value)', 'maxValue')
      .addSelect('COUNT(*)', 'count')
      .where('record.eventType = :eventType', { eventType: 'performance_metric' })
      .andWhere('record.timestamp BETWEEN :startDate AND :endDate', {
        startDate: new Date(startDate),
        endDate: new Date(endDate),
      })
      .andWhere('record.value IS NOT NULL');

    if (metricName) {
      queryBuilder.andWhere('record.eventName = :metricName', { metricName });
    }

    queryBuilder
      .groupBy('DATE(record.timestamp), record.eventName')
      .orderBy('date', 'ASC');

    return await queryBuilder.getRawMany();
  }

  /**
   * 获取错误分析
   */
  async getErrorAnalytics(
    startDate: string, 
    endDate: string
  ): Promise<any> {
    const [
      errorTrends,
      errorTypes,
      topErrors,
    ] = await Promise.all([
      this.getErrorTrends(startDate, endDate),
      this.getErrorTypes(startDate, endDate),
      this.getTopErrors(startDate, endDate),
    ]);

    return {
      trends: errorTrends,
      types: errorTypes,
      topErrors,
    };
  }

  /**
   * 获取错误趋势
   */
  private async getErrorTrends(startDate: string, endDate: string): Promise<any[]> {
    return await this.analyticsRecordRepository
      .createQueryBuilder('record')
      .select('DATE(record.timestamp)', 'date')
      .addSelect('COUNT(*)', 'errorCount')
      .where('record.eventType = :eventType', { eventType: 'error_event' })
      .andWhere('record.timestamp BETWEEN :startDate AND :endDate', {
        startDate: new Date(startDate),
        endDate: new Date(endDate),
      })
      .groupBy('DATE(record.timestamp)')
      .orderBy('date', 'ASC')
      .getRawMany();
  }

  /**
   * 获取错误类型分布
   */
  private async getErrorTypes(startDate: string, endDate: string): Promise<any[]> {
    return await this.analyticsRecordRepository
      .createQueryBuilder('record')
      .select('record.eventName', 'errorType')
      .addSelect('COUNT(*)', 'count')
      .where('record.eventType = :eventType', { eventType: 'error_event' })
      .andWhere('record.timestamp BETWEEN :startDate AND :endDate', {
        startDate: new Date(startDate),
        endDate: new Date(endDate),
      })
      .groupBy('record.eventName')
      .orderBy('count', 'DESC')
      .getRawMany();
  }

  /**
   * 获取热门错误
   */
  private async getTopErrors(startDate: string, endDate: string): Promise<any[]> {
    return await this.analyticsRecordRepository
      .createQueryBuilder('record')
      .select('record.eventName', 'errorName')
      .addSelect('record.eventData', 'errorData')
      .addSelect('COUNT(*)', 'count')
      .addSelect('MAX(record.timestamp)', 'lastOccurrence')
      .where('record.eventType = :eventType', { eventType: 'error_event' })
      .andWhere('record.timestamp BETWEEN :startDate AND :endDate', {
        startDate: new Date(startDate),
        endDate: new Date(endDate),
      })
      .groupBy('record.eventName, record.eventData')
      .orderBy('count', 'DESC')
      .limit(20)
      .getRawMany();
  }

  /**
   * 定时任务：汇总小时数据
   */
  @Cron(CronExpression.EVERY_HOUR)
  async summarizeHourlyData(): Promise<void> {
    const now = new Date();
    const oneHourAgo = new Date(now.getTime() - 60 * 60 * 1000);
    
    this.logger.log('开始汇总小时数据');
    
    try {
      await this.generateSummaries('hour', oneHourAgo, now);
      this.logger.log('小时数据汇总完成');
    } catch (error) {
      this.logger.error(`小时数据汇总失败: ${error.message}`);
    }
  }

  /**
   * 定时任务：汇总日数据
   */
  @Cron(CronExpression.EVERY_DAY_AT_2AM)
  async summarizeDailyData(): Promise<void> {
    const now = new Date();
    const yesterday = new Date(now.getTime() - 24 * 60 * 60 * 1000);
    
    this.logger.log('开始汇总日数据');
    
    try {
      await this.generateSummaries('day', yesterday, now);
      this.logger.log('日数据汇总完成');
    } catch (error) {
      this.logger.error(`日数据汇总失败: ${error.message}`);
    }
  }

  /**
   * 生成汇总数据
   */
  private async generateSummaries(
    period: string,
    startTime: Date,
    endTime: Date
  ): Promise<void> {
    // 获取需要汇总的指标类型
    const metricTypes = await this.analyticsRecordRepository
      .createQueryBuilder('record')
      .select('DISTINCT record.eventName', 'eventName')
      .addSelect('record.eventType', 'eventType')
      .addSelect('record.entityType', 'entityType')
      .where('record.timestamp BETWEEN :startTime AND :endTime', {
        startTime,
        endTime,
      })
      .getRawMany();

    for (const metric of metricTypes) {
      await this.generateSummaryForMetric(
        period,
        metric.eventName,
        metric.eventType,
        metric.entityType,
        startTime,
        endTime
      );
    }
  }

  /**
   * 为特定指标生成汇总
   */
  private async generateSummaryForMetric(
    period: string,
    eventName: string,
    eventType: string,
    entityType: string,
    startTime: Date,
    endTime: Date
  ): Promise<void> {
    const date = new Date(startTime.getFullYear(), startTime.getMonth(), startTime.getDate());

    // 计算汇总数据
    const summaryData = await this.analyticsRecordRepository
      .createQueryBuilder('record')
      .select('COUNT(*)', 'totalCount')
      .addSelect('SUM(CASE WHEN record.eventData->>"$.success" = "true" THEN 1 ELSE 0 END)', 'successCount')
      .addSelect('SUM(CASE WHEN record.eventData->>"$.success" = "false" THEN 1 ELSE 0 END)', 'failureCount')
      .addSelect('SUM(record.value)', 'totalValue')
      .addSelect('AVG(record.value)', 'averageValue')
      .addSelect('MIN(record.value)', 'minValue')
      .addSelect('MAX(record.value)', 'maxValue')
      .where('record.eventName = :eventName', { eventName })
      .andWhere('record.eventType = :eventType', { eventType })
      .andWhere('record.entityType = :entityType', { entityType })
      .andWhere('record.timestamp BETWEEN :startTime AND :endTime', {
        startTime,
        endTime,
      })
      .getRawOne();

    if (summaryData.totalCount > 0) {
      // 保存或更新汇总数据
      await this.analyticsSummaryRepository.upsert({
        metricType: eventName,
        entityType: entityType || 'global',
        period,
        date,
        totalCount: parseInt(summaryData.totalCount),
        successCount: parseInt(summaryData.successCount) || 0,
        failureCount: parseInt(summaryData.failureCount) || 0,
        totalValue: parseFloat(summaryData.totalValue) || 0,
        averageValue: parseFloat(summaryData.averageValue) || null,
        minValue: parseFloat(summaryData.minValue) || null,
        maxValue: parseFloat(summaryData.maxValue) || null,
      }, ['metricType', 'entityType', 'period', 'date']);
    }
  }

  /**
   * 清理过期数据
   */
  @Cron(CronExpression.EVERY_DAY_AT_3AM)
  async cleanupOldData(): Promise<void> {
    const retentionDays = parseInt(process.env.ANALYTICS_RETENTION_DAYS) || 90;
    const cutoffDate = new Date();
    cutoffDate.setDate(cutoffDate.getDate() - retentionDays);

    this.logger.log(`开始清理 ${retentionDays} 天前的分析数据`);

    try {
      const result = await this.analyticsRecordRepository
        .createQueryBuilder()
        .delete()
        .where('timestamp < :cutoffDate', { cutoffDate })
        .execute();

      this.logger.log(`清理完成，删除了 ${result.affected} 条记录`);
    } catch (error) {
      this.logger.error(`数据清理失败: ${error.message}`);
    }
  }
}