package analytics

import (
	"backend/internal/dto"
	"backend/internal/model"
	"time"

	"gorm.io/gorm"
)

// AnalyticsService 数据分析业务逻辑层 // Logan.Li
type AnalyticsService struct {
	db *gorm.DB
}

// NewAnalyticsService 创建 service 实例 // Logan.Li
func NewAnalyticsService(db *gorm.DB) *AnalyticsService {
	return &AnalyticsService{db: db}
}

// GetDashboardStats 仪表板统计 // Logan.Li
func (s *AnalyticsService) GetDashboardStats() (*dto.DashboardStats, error) {
	var stats dto.DashboardStats

	s.db.Model(&model.License{}).Count(&stats.TotalLicenses)
	s.db.Model(&model.License{}).Where("status = ?", model.LicenseStatusActive).Count(&stats.ActiveLicenses)

	// 本月新增 // Logan.Li
	now := time.Now()
	monthStart := time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, now.Location())
	s.db.Model(&model.License{}).Where("created_at >= ?", monthStart).Count(&stats.NewThisMonth)

	// 即将到期（30 天内） // Logan.Li
	thirtyDaysLater := now.AddDate(0, 0, 30)
	s.db.Model(&model.License{}).
		Where("status = ? AND end_date > ? AND end_date < ?", model.LicenseStatusActive, now, thirtyDaysLater).
		Count(&stats.ExpiringSoon)

	s.db.Model(&model.Customer{}).Count(&stats.TotalCustomers)
	s.db.Model(&model.Product{}).Count(&stats.TotalProducts)

	// 在线设备（5 分钟内有心跳） // Logan.Li
	fiveMinAgo := now.Add(-5 * time.Minute)
	s.db.Model(&model.Activation{}).Where("is_online = ? AND last_seen_at >= ?", true, fiveMinAgo).Count(&stats.OnlineDevices)

	// 本月收入 // Logan.Li
	s.db.Model(&model.Order{}).
		Where("status = ? AND paid_at >= ?", "paid", monthStart).
		Select("COALESCE(SUM(amount), 0)").
		Scan(&stats.MonthlyRevenue)

	return &stats, nil
}

// GetExpiringLicenses 即将到期 License 列表 // Logan.Li
func (s *AnalyticsService) GetExpiringLicenses(days int) ([]dto.ExpiringLicenseItem, error) {
	if days <= 0 {
		days = 30
	}
	now := time.Now()
	deadline := now.AddDate(0, 0, days)

	var licenses []model.License
	s.db.Preload("Customer").Preload("Product").
		Where("status = ? AND end_date > ? AND end_date < ?", model.LicenseStatusActive, now, deadline).
		Order("end_date ASC").Limit(20).Find(&licenses)

	results := make([]dto.ExpiringLicenseItem, 0, len(licenses))
	for _, l := range licenses {
		results = append(results, dto.ExpiringLicenseItem{
			ID:           l.ID,
			LicenseKey:   l.LicenseKey,
			CustomerName: l.Customer.Name,
			ProductName:  l.Product.Name,
			EndDate:      l.EndDate.Format("2006-01-02"),
			DaysLeft:     int(l.EndDate.Sub(now).Hours() / 24),
		})
	}
	return results, nil
}

// GetRecentActivities 最近操作活动 // Logan.Li
func (s *AnalyticsService) GetRecentActivities(limit int) ([]dto.RecentActivityItem, error) {
	if limit <= 0 {
		limit = 10
	}
	var logs []model.AuditLog
	s.db.Order("created_at DESC").Limit(limit).Find(&logs)

	results := make([]dto.RecentActivityItem, 0, len(logs))
	for _, l := range logs {
		results = append(results, dto.RecentActivityItem{
			ID:         l.ID,
			Username:   l.Username,
			Action:     l.Action,
			TargetType: l.TargetType,
			TargetName: l.TargetName,
			Detail:     l.Detail,
			CreatedAt:  l.CreatedAt.Format("2006-01-02 15:04:05"),
		})
	}
	return results, nil
}

// GetOnlineStats 在线统计 // Logan.Li
func (s *AnalyticsService) GetOnlineStats() (map[string]interface{}, error) {
	now := time.Now()
	fiveMinAgo := now.Add(-5 * time.Minute)

	var onlineDevices int64
	var totalActivations int64
	s.db.Model(&model.Activation{}).Where("is_online = ? AND last_seen_at >= ?", true, fiveMinAgo).Count(&onlineDevices)
	s.db.Model(&model.Activation{}).Where("status = ?", "active").Count(&totalActivations)

	return map[string]interface{}{
		"online_devices":      onlineDevices,
		"total_activations":   totalActivations,
		"offline_devices":     totalActivations - onlineDevices,
	}, nil
}

// GetRevenueStats 收入统计（近 6 个月） // Logan.Li
func (s *AnalyticsService) GetRevenueStats() ([]dto.RevenuePoint, error) {
	now := time.Now()
	results := make([]dto.RevenuePoint, 0, 6)
	for i := 5; i >= 0; i-- {
		monthStart := time.Date(now.Year(), now.Month()-time.Month(i), 1, 0, 0, 0, 0, now.Location())
		nextMonth := monthStart.AddDate(0, 1, 0)
		var amount float64
		s.db.Model(&model.Order{}).
			Where("status = ? AND created_at >= ? AND created_at < ?", "paid", monthStart, nextMonth).
			Select("COALESCE(SUM(amount), 0)").
			Scan(&amount)
		results = append(results, dto.RevenuePoint{
			Period: monthStart.Format("2006-01"),
			Amount: amount,
		})
	}
	return results, nil
}

// GetLicenseGrowth License 增长趋势（近 6 个月） // Logan.Li
func (s *AnalyticsService) GetLicenseGrowth() ([]dto.LicenseGrowthPoint, error) {
	now := time.Now()
	results := make([]dto.LicenseGrowthPoint, 0, 6)
	for i := 5; i >= 0; i-- {
		monthEnd := time.Date(now.Year(), now.Month()-time.Month(i)+1, 0, 23, 59, 59, 0, now.Location())
		var count int64
		s.db.Model(&model.License{}).Where("created_at <= ?", monthEnd).Count(&count)
		results = append(results, dto.LicenseGrowthPoint{
			Date:  monthEnd.Format("2006-01"),
			Count: count,
		})
	}
	return results, nil
}

// GetProductDistribution 产品分布 // Logan.Li
func (s *AnalyticsService) GetProductDistribution() ([]dto.ProductDistribution, error) {
	var results []dto.ProductDistribution
	s.db.Model(&model.License{}).
		Select("products.name as product_name, count(licenses.id) as count").
		Joins("LEFT JOIN products ON products.id = licenses.product_id").
		Group("licenses.product_id").
		Scan(&results)
	return results, nil
}