package entitlement

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

	"gorm.io/gorm"
)

// EntitlementService 客户权益业务逻辑层 // Logan.Li
type EntitlementService struct {
	db *gorm.DB
}

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

// List 分页/筛选查询权益 // Logan.Li
func (s *EntitlementService) List(page, pageSize int, customerID, productID uint) ([]dto.EntitlementResponse, int64, error) {
	var entitlements []model.CustomerEntitlement
	var total int64

	query := s.db.Model(&model.CustomerEntitlement{}).Preload("Customer").Preload("Product").Preload("Plan")
	if customerID > 0 {
		query = query.Where("customer_id = ?", customerID)
	}
	if productID > 0 {
		query = query.Where("product_id = ?", productID)
	}

	query.Count(&total)
	if err := query.Order("created_at DESC").
		Offset((page - 1) * pageSize).Limit(pageSize).
		Find(&entitlements).Error; err != nil {
		return nil, 0, err
	}

	results := make([]dto.EntitlementResponse, 0, len(entitlements))
	for _, e := range entitlements {
		results = append(results, s.toResponse(e))
	}
	return results, total, nil
}

// GetByID 获取权益详情 // Logan.Li
func (s *EntitlementService) GetByID(id uint) (*dto.EntitlementResponse, error) {
	var ent model.CustomerEntitlement
	if err := s.db.Preload("Customer").Preload("Product").Preload("Plan").First(&ent, id).Error; err != nil {
		return nil, errors.New("权益记录不存在")
	}
	resp := s.toResponse(ent)
	return &resp, nil
}

// Revoke 吊销权益 // Logan.Li
func (s *EntitlementService) Revoke(id uint) error {
	var ent model.CustomerEntitlement
	if err := s.db.First(&ent, id).Error; err != nil {
		return errors.New("权益记录不存在")
	}
	return s.db.Transaction(func(tx *gorm.DB) error {
		ent.Status = "revoked"
		if err := tx.Save(&ent).Error; err != nil {
			return err
		}
		// 同步吊销关联 License // Logan.Li
		if ent.LicenseID > 0 {
			tx.Model(&model.License{}).Where("id = ?", ent.LicenseID).
				Updates(map[string]interface{}{"status": model.LicenseStatusRevoked, "revoke_reason": "权益被吊销"})
		}
		return nil
	})
}

// Renew 续费订阅（按计划延长有效期） // Logan.Li
func (s *EntitlementService) Renew(id, planID uint) (*dto.EntitlementResponse, error) {
	var ent model.CustomerEntitlement
	if err := s.db.First(&ent, id).Error; err != nil {
		return nil, errors.New("权益记录不存在")
	}
	var plan model.Plan
	if err := s.db.First(&plan, planID).Error; err != nil {
		return nil, errors.New("定价计划不存在")
	}

	now := time.Now()
	var validUntil *time.Time
	if plan.Duration == 0 {
		validUntil = nil // 永久
	} else {
		var base time.Time
		if ent.ValidUntil != nil && ent.ValidUntil.After(now) {
			base = *ent.ValidUntil
		} else {
			base = now
		}
		end := base.AddDate(0, 0, plan.Duration)
		validUntil = &end
	}

	ent.Status = "active"
	ent.ValidFrom = now
	ent.ValidUntil = validUntil
	ent.PlanID = planID
	ent.PlanType = plan.PlanType
	if err := s.db.Save(&ent).Error; err != nil {
		return nil, errors.New("续费失败")
	}

	// 同步延长关联 License 有效期 // Logan.Li
	if ent.LicenseID > 0 {
		var lic model.License
		s.db.First(&lic, ent.LicenseID)
		if plan.Duration == 0 {
			lic.EndDate = model.PermanentEndDate
		} else {
			base := lic.EndDate
			if utils.IsLicenseExpired(lic.EndDate) {
				base = now
			}
			lic.EndDate = base.AddDate(0, 0, plan.Duration)
		}
		lic.Status = model.LicenseStatusActive
		s.db.Save(&lic)
	}

	s.db.Preload("Customer").Preload("Product").Preload("Plan").First(&ent, id)
	resp := s.toResponse(ent)
	return &resp, nil
}

// GetByEmail 按邮箱查询客户权益（客户端接口） // Logan.Li
func (s *EntitlementService) GetByEmail(email string) ([]dto.EntitlementResponse, error) {
	var customer model.Customer
	if err := s.db.Where("email = ?", email).First(&customer).Error; err != nil {
		return []dto.EntitlementResponse{}, nil
	}

	var entitlements []model.CustomerEntitlement
	s.db.Where("customer_id = ?", customer.ID).
		Preload("Product").Preload("Plan").
		Find(&entitlements)

	results := make([]dto.EntitlementResponse, 0, len(entitlements))
	for _, e := range entitlements {
		results = append(results, s.toResponse(e))
	}
	return results, nil
}

// toResponse 模型转响应 DTO // Logan.Li
func (s *EntitlementService) toResponse(e model.CustomerEntitlement) dto.EntitlementResponse {
	resp := dto.EntitlementResponse{
		ID:         e.ID,
		CustomerID: e.CustomerID,
		ProductID:  e.ProductID,
		PlanID:     e.PlanID,
		PlanType:   e.PlanType,
		LicenseKey: e.LicenseKey,
		Status:     e.Status,
		ValidFrom:  e.ValidFrom.Format("2006-01-02 15:04:05"),
		Renewable:  e.Renewable,
	}
	if e.Customer.ID > 0 {
		resp.CustomerName = e.Customer.Name
	}
	if e.Product.ID > 0 {
		resp.ProductName = e.Product.Name
	}
	if e.Plan.ID > 0 {
		resp.PlanName = e.Plan.Name
	}
	if e.ValidUntil != nil {
		s := e.ValidUntil.Format("2006-01-02 15:04:05")
		resp.ValidUntil = &s
		resp.DaysLeft = utils.CalculateDaysLeft(*e.ValidUntil)
	} else {
		resp.DaysLeft = 9999 // 永久
	}
	// 查设备数 // Logan.Li
	if e.LicenseID > 0 {
		var lic model.License
		s.db.First(&lic, e.LicenseID)
		resp.MaxDevices = lic.MaxActivations
		var count int64
		s.db.Model(&model.Activation{}).Where("license_id = ?", e.LicenseID).Count(&count)
		resp.CurrentDevices = int(count)
	}
	return resp
}