/**
 * 数据统计和分析工具
 */

const { Storage } = require('./storage.js')
const { logger } = require('./logger.js')

class Analytics {
  /**
   * 获取学习统计数据
   */
  static getStudyStats() {
    const gpaCourses = Storage.get('gpaCourses', [])
    const countdowns = Storage.get('countdowns', [])
    const favoriteCourses = Storage.get('favoriteCourses', [])

    const stats = {
      // GPA统计
      gpa: {
        total: gpaCourses.length,
        average: this._calculateAverageGPA(gpaCourses),
        highest: this._getHighestScore(gpaCourses),
        lowest: this._getLowestScore(gpaCourses),
        trend: this._calculateGPATrend(gpaCourses)
      },

      // 课程统计
      courses: {
        total: favoriteCourses.length,
        byCategory: this._groupByCategory(gpaCourses),
        completionRate: this._calculateCompletionRate(gpaCourses)
      },

      // 考试倒计时
      exams: {
        total: countdowns.length,
        upcoming: countdowns.filter(c => c.days > 0).length,
        thisWeek: countdowns.filter(c => c.days <= 7 && c.days > 0).length
      },

      // 学习时长统计（模拟数据）
      studyTime: {
        today: 0,
        week: 0,
        month: 0
      }
    }

    return stats
  }

  /**
   * 计算平均GPA
   */
  static _calculateAverageGPA(courses) {
    if (courses.length === 0) return 0

    let totalPoints = 0
    let totalCredits = 0

    courses.forEach(course => {
      const gradePoint = this._scoreToGradePoint(course.score)
      totalPoints += gradePoint * course.credit
      totalCredits += course.credit
    })

    return totalCredits > 0 ? (totalPoints / totalCredits).toFixed(2) : 0
  }

  /**
   * 分数转绩点
   */
  static _scoreToGradePoint(score) {
    if (score >= 60) {
      return parseFloat((score / 10 - 5).toFixed(2))
    }
    return 0
  }

  /**
   * 获取最高分
   */
  static _getHighestScore(courses) {
    if (courses.length === 0) return 0
    return Math.max(...courses.map(c => c.score))
  }

  /**
   * 获取最低分
   */
  static _getLowestScore(courses) {
    if (courses.length === 0) return 0
    return Math.min(...courses.map(c => c.score))
  }

  /**
   * 计算GPA趋势
   */
  static _calculateGPATrend(courses) {
    if (courses.length < 2) return []

    // 按时间排序（假设ID越大时间越新）
    const sorted = [...courses].sort((a, b) => a.id - b.id)

    const trend = []
    let runningTotal = 0
    let runningCredits = 0

    sorted.forEach(course => {
      const gradePoint = this._scoreToGradePoint(course.score)
      runningTotal += gradePoint * course.credit
      runningCredits += course.credit

      const gpa = runningCredits > 0 ? (runningTotal / runningCredits).toFixed(2) : 0

      trend.push({
        name: course.name,
        gpa: parseFloat(gpa),
        score: course.score
      })
    })

    return trend
  }

  /**
   * 按分类分组
   */
  static _groupByCategory(courses) {
    const grouped = {}

    courses.forEach(course => {
      const category = course.category || '其他'
      if (!grouped[category]) {
        grouped[category] = {
          count: 0,
          totalScore: 0,
          avgScore: 0
        }
      }

      grouped[category].count++
      grouped[category].totalScore += course.score
    })

    // 计算平均分
    Object.keys(grouped).forEach(key => {
      grouped[key].avgScore = (grouped[key].totalScore / grouped[key].count).toFixed(1)
    })

    return grouped
  }

  /**
   * 计算完成率
   */
  static _calculateCompletionRate(courses) {
    if (courses.length === 0) return 0
    const passed = courses.filter(c => c.score >= 60).length
    return ((passed / courses.length) * 100).toFixed(1)
  }

  /**
   * 生成学习报告
   */
  static generateReport() {
    const stats = this.getStudyStats()

    const report = {
      summary: {
        gpa: stats.gpa.average,
        totalCourses: stats.courses.total,
        passRate: stats.courses.completionRate
      },
      highlights: [],
      suggestions: []
    }

    // 添加亮点
    if (parseFloat(stats.gpa.average) >= 3.5) {
      report.highlights.push('GPA优秀，继续保持！')
    }

    if (parseFloat(stats.courses.completionRate) === 100) {
      report.highlights.push('所有课程全部通过，非常棒！')
    }

    // 添加建议
    if (parseFloat(stats.gpa.average) < 2.5) {
      report.suggestions.push('建议加强学习，提高GPA')
    }

    if (stats.exams.thisWeek > 0) {
      report.suggestions.push(`本周有${stats.exams.thisWeek}场考试，请做好准备`)
    }

    logger.info('生成学习报告', report)

    return report
  }

  /**
   * 导出数据
   */
  static exportData() {
    const data = {
      gpaCourses: Storage.get('gpaCourses', []),
      favoriteCourses: Storage.get('favoriteCourses', []),
      schedule: Storage.get('schedule', {}),
      countdowns: Storage.get('countdowns', []),
      exportTime: new Date().toISOString()
    }

    logger.info('导出数据', { recordCount: data.gpaCourses.length })

    return data
  }

  /**
   * 导入数据
   */
  static importData(data) {
    try {
      if (data.gpaCourses) {
        Storage.set('gpaCourses', data.gpaCourses)
      }

      if (data.favoriteCourses) {
        Storage.set('favoriteCourses', data.favoriteCourses)
      }

      if (data.schedule) {
        Storage.set('schedule', data.schedule)
      }

      if (data.countdowns) {
        Storage.set('countdowns', data.countdowns)
      }

      logger.info('导入数据成功', { recordCount: data.gpaCourses?.length || 0 })

      return { success: true }
    } catch (error) {
      logger.error('导入数据失败', error)
      return { success: false, error }
    }
  }
}

/**
 * 智能推荐系统
 */
class RecommendationEngine {
  /**
   * 推荐课程
   */
  static recommendCourses(allCourses, userCourses) {
    const recommendations = []

    // 基于用户已选课程推荐相关课程
    const userCategories = [...new Set(userCourses.map(c => c.category))]

    allCourses.forEach(course => {
      let score = 0

      // 相同分类加分
      if (userCategories.includes(course.category)) {
        score += 3
      }

      // 热门课程加分
      if (course.enrolled / course.capacity > 0.8) {
        score += 2
      }

      // 高评分课程加分
      if (course.rating && course.rating >= 4.5) {
        score += 2
      }

      // 还有名额的课程加分
      if (course.enrolled < course.capacity) {
        score += 1
      }

      if (score > 0) {
        recommendations.push({
          course,
          score,
          reason: this._getRecommendReason(score)
        })
      }
    })

    // 按分数排序
    recommendations.sort((a, b) => b.score - a.score)

    return recommendations.slice(0, 5)
  }

  /**
   * 获取推荐理由
   */
  static _getRecommendReason(score) {
    if (score >= 6) return '强烈推荐'
    if (score >= 4) return '推荐'
    return '可以考虑'
  }

  /**
   * 学习建议
   */
  static getStudySuggestions(stats) {
    const suggestions = []

    // GPA建议
    if (parseFloat(stats.gpa.average) < 2.0) {
      suggestions.push({
        type: 'gpa',
        level: 'warning',
        message: '当前GPA较低，建议加强学习',
        action: '查看学习计划'
      })
    } else if (parseFloat(stats.gpa.average) >= 3.5) {
      suggestions.push({
        type: 'gpa',
        level: 'success',
        message: 'GPA优秀，继续保持！',
        action: '分享经验'
      })
    }

    // 考试提醒
    if (stats.exams.thisWeek > 0) {
      suggestions.push({
        type: 'exam',
        level: 'info',
        message: `本周有${stats.exams.thisWeek}场考试`,
        action: '查看倒计时'
      })
    }

    return suggestions
  }
}

module.exports = {
  Analytics,
  RecommendationEngine
}