package services

import (
	"errors"
	"fmt"
	"strings"
	"tyapi-server/internal/domains/product/entities"
	"tyapi-server/internal/domains/product/repositories"
)

// ProductService 产品领域服务
type ProductService struct {
	productRepo    repositories.ProductRepository
	categoryRepo   repositories.ProductCategoryRepository
	subscriptionRepo repositories.SubscriptionRepository
}

// NewProductService 创建产品领域服务
func NewProductService(
	productRepo repositories.ProductRepository,
	categoryRepo repositories.ProductCategoryRepository,
	subscriptionRepo repositories.SubscriptionRepository,
) *ProductService {
	return &ProductService{
		productRepo:    productRepo,
		categoryRepo:   categoryRepo,
		subscriptionRepo: subscriptionRepo,
	}
}

// ValidateProduct 验证产品
func (s *ProductService) ValidateProduct(product *entities.Product) error {
	if product == nil {
		return errors.New("产品不能为空")
	}
	
	if strings.TrimSpace(product.Name) == "" {
		return errors.New("产品名称不能为空")
	}
	
	if strings.TrimSpace(product.Code) == "" {
		return errors.New("产品编号不能为空")
	}
	
	if product.Price < 0 {
		return errors.New("产品价格不能为负数")
	}
	
	// 验证分类是否存在
	if product.CategoryID != "" {
		category, err := s.categoryRepo.GetByID(nil, product.CategoryID)
		if err != nil {
			return fmt.Errorf("产品分类不存在: %w", err)
		}
		if !category.IsValid() {
			return errors.New("产品分类已禁用或删除")
		}
	}
	
	return nil
}

// ValidateProductCode 验证产品编号唯一性
func (s *ProductService) ValidateProductCode(code string, excludeID string) error {
	if strings.TrimSpace(code) == "" {
		return errors.New("产品编号不能为空")
	}
	
	existingProduct, err := s.productRepo.FindByCode(nil, code)
	if err == nil && existingProduct != nil && existingProduct.ID != excludeID {
		return errors.New("产品编号已存在")
	}
	
	return nil
}

// CanUserSubscribeProduct 检查用户是否可以订阅产品
func (s *ProductService) CanUserSubscribeProduct(userID string, productID string) (bool, error) {
	// 检查产品是否存在且可订阅
	product, err := s.productRepo.GetByID(nil, productID)
	if err != nil {
		return false, fmt.Errorf("产品不存在: %w", err)
	}
	
	if !product.CanBeSubscribed() {
		return false, errors.New("产品不可订阅")
	}
	
	// 检查用户是否已有该产品的订阅
	existingSubscription, err := s.subscriptionRepo.FindByUserAndProduct(nil, userID, productID)
	if err == nil && existingSubscription != nil {
		return false, errors.New("用户已有该产品的订阅")
	}
	
	return true, nil
}

// GetProductWithCategory 获取产品及其分类信息
func (s *ProductService) GetProductWithCategory(productID string) (*entities.Product, error) {
	product, err := s.productRepo.GetByID(nil, productID)
	if err != nil {
		return nil, fmt.Errorf("产品不存在: %w", err)
	}
	
	// 加载分类信息
	if product.CategoryID != "" {
		category, err := s.categoryRepo.GetByID(nil, product.CategoryID)
		if err == nil {
			product.Category = &category
		}
	}
	
	return &product, nil
}

// GetVisibleProducts 获取可见产品列表
func (s *ProductService) GetVisibleProducts() ([]*entities.Product, error) {
	return s.productRepo.FindVisible(nil)
}

// GetEnabledProducts 获取启用产品列表
func (s *ProductService) GetEnabledProducts() ([]*entities.Product, error) {
	return s.productRepo.FindEnabled(nil)
}

// GetProductsByCategory 根据分类获取产品
func (s *ProductService) GetProductsByCategory(categoryID string) ([]*entities.Product, error) {
	return s.productRepo.FindByCategoryID(nil, categoryID)
}

// GetProductStats 获取产品统计信息
func (s *ProductService) GetProductStats() (map[string]int64, error) {
	stats := make(map[string]int64)
	
	total, err := s.productRepo.CountByCategory(nil, "")
	if err == nil {
		stats["total"] = total
	}
	
	enabled, err := s.productRepo.CountEnabled(nil)
	if err == nil {
		stats["enabled"] = enabled
	}
	
	visible, err := s.productRepo.CountVisible(nil)
	if err == nil {
		stats["visible"] = visible
	}
	
	return stats, nil
}