package services

import (
	"errors"
	"time"

	"github.com/Nanqipro/YunQue-Tech-Projects/ai_english_learning/serve/internal/models"
	"gorm.io/gorm"
)

// StudyPlanService 学习计划服务
type StudyPlanService struct {
	db *gorm.DB
}

func NewStudyPlanService(db *gorm.DB) *StudyPlanService {
	return &StudyPlanService{db: db}
}

// CreateStudyPlan 创建学习计划
func (s *StudyPlanService) CreateStudyPlan(userID int64, planName string, description *string, dailyGoal int, 
	bookID *string, startDate time.Time, endDate *time.Time, remindTime *string, remindDays *string) (*models.StudyPlan, error) {
	
	// 验证参数
	if dailyGoal < 1 || dailyGoal > 200 {
		return nil, errors.New("每日目标必须在1-200之间")
	}
	
	// 如果指定了词汇书，获取总单词数
	totalWords := 0
	if bookID != nil && *bookID != "" {
		var count int64
		s.db.Model(&models.VocabularyBookWord{}).Where("book_id = ?", *bookID).Count(&count)
		totalWords = int(count)
	}
	
	plan := &models.StudyPlan{
		UserID:          userID,
		BookID:          bookID,
		PlanName:        planName,
		Description:     description,
		DailyGoal:       dailyGoal,
		TotalWords:      totalWords,
		LearnedWords:    0,
		StartDate:       startDate,
		EndDate:         endDate,
		Status:          "active",
		RemindTime:      remindTime,
		RemindDays:      remindDays,
		IsRemindEnabled: remindTime != nil && remindDays != nil,
		StreakDays:      0,
	}
	
	if err := s.db.Create(plan).Error; err != nil {
		return nil, err
	}
	
	return plan, nil
}

// GetUserStudyPlans 获取用户的学习计划列表
func (s *StudyPlanService) GetUserStudyPlans(userID int64, status string) ([]models.StudyPlan, error) {
	var plans []models.StudyPlan
	query := s.db.Where("user_id = ?", userID)
	
	if status != "" && status != "all" {
		query = query.Where("status = ?", status)
	}
	
	err := query.Order("created_at DESC").Find(&plans).Error
	return plans, err
}

// GetStudyPlanByID 获取学习计划详情
func (s *StudyPlanService) GetStudyPlanByID(planID, userID int64) (*models.StudyPlan, error) {
	var plan models.StudyPlan
	err := s.db.Where("id = ? AND user_id = ?", planID, userID).First(&plan).Error
	if err != nil {
		return nil, err
	}
	return &plan, nil
}

// UpdateStudyPlan 更新学习计划
func (s *StudyPlanService) UpdateStudyPlan(planID, userID int64, updates map[string]interface{}) (*models.StudyPlan, error) {
	var plan models.StudyPlan
	if err := s.db.Where("id = ? AND user_id = ?", planID, userID).First(&plan).Error; err != nil {
		return nil, err
	}
	
	// 验证dailyGoal
	if dailyGoal, ok := updates["daily_goal"].(int); ok {
		if dailyGoal < 1 || dailyGoal > 200 {
			return nil, errors.New("每日目标必须在1-200之间")
		}
	}
	
	if err := s.db.Model(&plan).Updates(updates).Error; err != nil {
		return nil, err
	}
	
	return &plan, nil
}

// DeleteStudyPlan 删除学习计划（软删除）
func (s *StudyPlanService) DeleteStudyPlan(planID, userID int64) error {
	result := s.db.Where("id = ? AND user_id = ?", planID, userID).Delete(&models.StudyPlan{})
	if result.Error != nil {
		return result.Error
	}
	if result.RowsAffected == 0 {
		return errors.New("计划不存在或无权删除")
	}
	return nil
}

// UpdatePlanStatus 更新计划状态
func (s *StudyPlanService) UpdatePlanStatus(planID, userID int64, status string) error {
	validStatuses := map[string]bool{
		"active":    true,
		"paused":    true,
		"completed": true,
		"cancelled": true,
	}
	
	if !validStatuses[status] {
		return errors.New("无效的状态")
	}
	
	updates := map[string]interface{}{
		"status": status,
	}
	
	if status == "completed" {
		now := time.Now()
		updates["completed_at"] = now
	}
	
	result := s.db.Model(&models.StudyPlan{}).
		Where("id = ? AND user_id = ?", planID, userID).
		Updates(updates)
	
	if result.Error != nil {
		return result.Error
	}
	if result.RowsAffected == 0 {
		return errors.New("计划不存在或无权修改")
	}
	
	return nil
}

// RecordStudyProgress 记录学习进度
func (s *StudyPlanService) RecordStudyProgress(planID, userID int64, wordsStudied, studyDuration int) error {
	var plan models.StudyPlan
	if err := s.db.Where("id = ? AND user_id = ?", planID, userID).First(&plan).Error; err != nil {
		return err
	}
	
	today := time.Now().Truncate(24 * time.Hour)
	
	// 检查今天是否已有记录
	var record models.StudyPlanRecord
	err := s.db.Where("plan_id = ? AND user_id = ? AND study_date = ?", planID, userID, today).First(&record).Error
	
	if err == gorm.ErrRecordNotFound {
		// 创建新记录
		record = models.StudyPlanRecord{
			PlanID:        planID,
			UserID:        userID,
			StudyDate:     today,
			WordsStudied:  wordsStudied,
			GoalCompleted: wordsStudied >= plan.DailyGoal,
			StudyDuration: studyDuration,
		}
		if err := s.db.Create(&record).Error; err != nil {
			return err
		}
	} else if err == nil {
		// 更新现有记录
		record.WordsStudied += wordsStudied
		record.StudyDuration += studyDuration
		record.GoalCompleted = record.WordsStudied >= plan.DailyGoal
		if err := s.db.Save(&record).Error; err != nil {
			return err
		}
	} else {
		return err
	}
	
	// 更新计划的已学单词数
	plan.LearnedWords += wordsStudied
	
	// 更新连续学习天数
	if plan.LastStudyDate != nil {
		lastDate := plan.LastStudyDate.Truncate(24 * time.Hour)
		yesterday := today.AddDate(0, 0, -1)
		
		if lastDate.Equal(yesterday) {
			plan.StreakDays++
		} else if !lastDate.Equal(today) {
			plan.StreakDays = 1
		}
	} else {
		plan.StreakDays = 1
	}
	
	plan.LastStudyDate = &today
	
	// 检查是否完成计划
	if plan.TotalWords > 0 && plan.LearnedWords >= plan.TotalWords {
		plan.Status = "completed"
		now := time.Now()
		plan.CompletedAt = &now
	}
	
	return s.db.Save(&plan).Error
}

// GetStudyPlanStatistics 获取学习计划统计
func (s *StudyPlanService) GetStudyPlanStatistics(planID, userID int64) (map[string]interface{}, error) {
	var plan models.StudyPlan
	if err := s.db.Where("id = ? AND user_id = ?", planID, userID).First(&plan).Error; err != nil {
		return nil, err
	}
	
	// 统计总学习天数
	var totalStudyDays int64
	s.db.Model(&models.StudyPlanRecord{}).
		Where("plan_id = ? AND user_id = ?", planID, userID).
		Count(&totalStudyDays)
	
	// 统计完成目标的天数
	var completedDays int64
	s.db.Model(&models.StudyPlanRecord{}).
		Where("plan_id = ? AND user_id = ? AND goal_completed = ?", planID, userID, true).
		Count(&completedDays)
	
	// 计算平均每日学习单词数
	var avgWords float64
	s.db.Model(&models.StudyPlanRecord{}).
		Select("AVG(words_studied) as avg_words").
		Where("plan_id = ? AND user_id = ?", planID, userID).
		Scan(&avgWords)
	
	// 计算完成率
	completionRate := 0.0
	if plan.TotalWords > 0 {
		completionRate = float64(plan.LearnedWords) / float64(plan.TotalWords) * 100
	}
	
	// 获取最近7天的学习记录
	var recentRecords []models.StudyPlanRecord
	s.db.Where("plan_id = ? AND user_id = ?", planID, userID).
		Order("study_date DESC").
		Limit(7).
		Find(&recentRecords)
	
	return map[string]interface{}{
		"plan":             plan,
		"total_study_days": totalStudyDays,
		"completed_days":   completedDays,
		"avg_words":        avgWords,
		"completion_rate":  completionRate,
		"recent_records":   recentRecords,
		"streak_days":      plan.StreakDays,
	}, nil
}

// GetTodayStudyPlans 获取今日需要执行的学习计划
func (s *StudyPlanService) GetTodayStudyPlans(userID int64) ([]map[string]interface{}, error) {
	var plans []models.StudyPlan
	today := time.Now().Truncate(24 * time.Hour)
	weekday := int(time.Now().Weekday())
	if weekday == 0 {
		weekday = 7 // 将周日从0改为7
	}
	
	// 查找活跃的计划
	err := s.db.Where("user_id = ? AND status = ? AND start_date <= ?", userID, "active", today).
		Find(&plans).Error
	
	if err != nil {
		return nil, err
	}
	
	result := make([]map[string]interface{}, 0)
	
	for _, plan := range plans {
		// 检查今天是否已完成
		var record models.StudyPlanRecord
		err := s.db.Where("plan_id = ? AND user_id = ? AND study_date = ?", plan.ID, userID, today).
			First(&record).Error
		
		todayCompleted := err == nil && record.GoalCompleted
		todayProgress := 0
		if err == nil {
			todayProgress = record.WordsStudied
		}
		
		// 检查是否需要提醒
		needRemind := false
		if plan.IsRemindEnabled && plan.RemindDays != nil {
			// 简单检查：这里可以根据RemindDays判断今天是否需要提醒
			needRemind = true
		}
		
		result = append(result, map[string]interface{}{
			"plan":            plan,
			"today_completed": todayCompleted,
			"today_progress":  todayProgress,
			"need_remind":     needRemind,
		})
	}
	
	return result, nil
}