package license

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

	"gorm.io/gorm"
)

func inferPlanType(lic model.License) string {
	if lic.IsTrial {
		return "trial"
	}
	if lic.Duration <= 0 || lic.EndDate.Equal(model.PermanentEndDate) || lic.EndDate.Year() >= 2099 {
		return "perpetual"
	}
	// 先判月度，再判体验/包年，避免 monthly 成为死代码 // Logan.Li
	if lic.Duration <= 31 {
		return "monthly"
	}
	if lic.Duration <= 180 {
		return "trial"
	}
	return "yearly"
}

func licenseClientPayload(lic model.License) map[string]interface{} {
	return map[string]interface{}{
		"expires_at":  lic.EndDate.Format("2006-01-02 15:04:05"),
		"days_left":   utils.CalculateDaysLeft(lic.EndDate),
		"max_devices": lic.MaxActivations,
		"plan_type":   inferPlanType(lic),
	}
}

// Verify 客户端 License 验证 // Logan.Li
func (s *LicenseService) Verify(req dto.LicenseVerifyRequest) (*dto.LicenseVerifyResponse, error) {
	var lic model.License
	if err := s.db.Preload("Product").Where("license_key = ?", req.LicenseKey).First(&lic).Error; err != nil {
		return &dto.LicenseVerifyResponse{Valid: false, Message: "无效的 License"}, nil
	}

	if req.ProductID > 0 && lic.ProductID != req.ProductID {
		return &dto.LicenseVerifyResponse{Valid: false, Message: "License 与产品不匹配"}, nil
	}

	switch lic.Status {
	case model.LicenseStatusRevoked:
		return &dto.LicenseVerifyResponse{Valid: false, Message: "License 已被吊销"}, nil
	case model.LicenseStatusSuspended:
		return &dto.LicenseVerifyResponse{Valid: false, Message: "License 已被暂停"}, nil
	case model.LicenseStatusExpired:
		return &dto.LicenseVerifyResponse{Valid: false, Message: "License 已过期"}, nil
	}

	if utils.IsLicenseExpired(lic.EndDate) {
		lic.Status = model.LicenseStatusExpired
		s.db.Save(&lic)
		return &dto.LicenseVerifyResponse{Valid: false, Message: "License 已过期"}, nil
	}

	return &dto.LicenseVerifyResponse{
		Valid:       true,
		LicenseKey:  lic.LicenseKey,
		ProductID:   lic.ProductID,
		ProductName: lic.Product.Name,
		ProductCode: lic.Product.Code,
		Features:    utils.ParseFeatures(lic.Product.Features),
		Status:      lic.Status,
		ExpiresAt:   lic.EndDate.Format("2006-01-02 15:04:05"),
		DaysLeft:    utils.CalculateDaysLeft(lic.EndDate),
		MaxDevices:  lic.MaxActivations,
		PlanType:    inferPlanType(lic),
		Message:     "验证成功",
	}, nil
}

// Activate 客户端激活 License（事务 + 条件占座，消除 TOCTOU） // Logan.Li
func (s *LicenseService) Activate(req dto.LicenseActivateRequest, clientIP string) (map[string]interface{}, error) {
	var payload map[string]interface{}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		var lic model.License
		if err := tx.Where("license_key = ?", req.LicenseKey).First(&lic).Error; err != nil {
			return errors.New("无效的 License")
		}
		if lic.Status == model.LicenseStatusRevoked || lic.Status == model.LicenseStatusSuspended {
			return errors.New("License 已被吊销或暂停")
		}
		if lic.Status == model.LicenseStatusExpired || utils.IsLicenseExpired(lic.EndDate) {
			return errors.New("License 已过期")
		}

		now := time.Now()
		var existing model.Activation
		if err := tx.Where("license_id = ? AND device_id = ?", lic.ID, req.DeviceID).
			First(&existing).Error; err == nil {
			updates := map[string]interface{}{
				"last_seen_at": now,
				"is_online":    true,
				"device_name":  req.DeviceName,
				"device_info":  req.DeviceInfo,
				"ip":           clientIP,
			}
			if existing.Status != "active" {
				updates["status"] = "active"
				res := tx.Model(&model.License{}).
					Where("id = ? AND current_activations < max_activations", lic.ID).
					Update("current_activations", gorm.Expr("current_activations + 1"))
				if res.Error != nil {
					return res.Error
				}
				if res.RowsAffected == 0 {
					return errors.New("已达到最大激活数量限制")
				}
			}
			if err := tx.Model(&existing).Updates(updates).Error; err != nil {
				return err
			}
			if err := tx.First(&lic, lic.ID).Error; err != nil {
				return err
			}
			payload = licenseClientPayload(lic)
			return nil
		}

		res := tx.Model(&model.License{}).
			Where("id = ? AND current_activations < max_activations", lic.ID).
			Updates(map[string]interface{}{
				"current_activations": gorm.Expr("current_activations + 1"),
				"status":              model.LicenseStatusActive,
			})
		if res.Error != nil {
			return res.Error
		}
		if res.RowsAffected == 0 {
			return errors.New("已达到最大激活数量限制")
		}

		if err := tx.Create(&model.Activation{
			LicenseID:   lic.ID,
			DeviceID:    req.DeviceID,
			DeviceName:  req.DeviceName,
			DeviceInfo:  req.DeviceInfo,
			IP:          clientIP,
			Status:      "active",
			IsOnline:    true,
			ActivatedAt: now,
			LastSeenAt:  now,
		}).Error; err != nil {
			return errors.New("激活失败")
		}
		if err := tx.First(&lic, lic.ID).Error; err != nil {
			return err
		}
		payload = licenseClientPayload(lic)
		return nil
	})
	if err != nil {
		return nil, err
	}
	return payload, nil
}

// Deactivate 客户端停用（仅 active→inactive 才减席位） // Logan.Li
func (s *LicenseService) Deactivate(req dto.LicenseDeactivateRequest) error {
	return s.db.Transaction(func(tx *gorm.DB) error {
		var lic model.License
		if err := tx.Where("license_key = ?", req.LicenseKey).First(&lic).Error; err != nil {
			return errors.New("无效的 License")
		}
		res := tx.Model(&model.Activation{}).
			Where("license_id = ? AND device_id = ? AND status = ?", lic.ID, req.DeviceID, "active").
			Updates(map[string]interface{}{"status": "inactive", "is_online": false})
		if res.Error != nil {
			return res.Error
		}
		if res.RowsAffected > 0 {
			return tx.Model(&model.License{}).
				Where("id = ? AND current_activations > 0", lic.ID).
				Update("current_activations", gorm.Expr("current_activations - 1")).Error
		}
		return nil
	})
}

// Heartbeat 客户端心跳 // Logan.Li
func (s *LicenseService) Heartbeat(req dto.LicenseHeartbeatRequest) (map[string]interface{}, error) {
	var lic model.License
	if err := s.db.Where("license_key = ?", req.LicenseKey).First(&lic).Error; err != nil {
		return nil, errors.New("无效的 License")
	}

	if lic.Status == model.LicenseStatusRevoked || lic.Status == model.LicenseStatusSuspended {
		return nil, errors.New("License 已被吊销或暂停")
	}
	if lic.Status == model.LicenseStatusExpired || utils.IsLicenseExpired(lic.EndDate) {
		return nil, errors.New("License 已过期")
	}

	s.db.Model(&model.Activation{}).
		Where("license_id = ? AND device_id = ?", lic.ID, req.DeviceID).
		Updates(map[string]interface{}{"last_seen_at": time.Now(), "is_online": true})

	return licenseClientPayload(lic), nil
}

// ListDevicesByKey returns activations for a license key (client self-service). // Logan.Li
func (s *LicenseService) ListDevicesByKey(licenseKey string) ([]dto.ActivationResponse, int, error) {
	var lic model.License
	if err := s.db.Where("license_key = ?", licenseKey).First(&lic).Error; err != nil {
		return nil, 0, errors.New("无效的 License")
	}
	var activations []model.Activation
	if err := s.db.Where("license_id = ? AND status = ?", lic.ID, "active").Order("activated_at DESC").Find(&activations).Error; err != nil {
		return nil, 0, errors.New("获取设备列表失败")
	}
	results := make([]dto.ActivationResponse, 0, len(activations))
	for _, a := range activations {
		results = append(results, toActivationResponse(a))
	}
	return results, lic.MaxActivations, nil
}