package services

import (
	"context"
	"errors"
	"fmt"
	"time"

	"gorm.io/gorm"

	"go.uber.org/zap"

	"tyapi-server/internal/domains/product/entities"
	"tyapi-server/internal/domains/product/repositories"
	"tyapi-server/internal/domains/product/repositories/queries"
)

// ProductSubscriptionService 产品订阅领域服务
// 负责产品订阅相关的业务逻辑，包括订阅验证、订阅管理等
type ProductSubscriptionService struct {
	productRepo      repositories.ProductRepository
	subscriptionRepo repositories.SubscriptionRepository
	logger           *zap.Logger
}

// NewProductSubscriptionService 创建产品订阅领域服务
func NewProductSubscriptionService(
	productRepo repositories.ProductRepository,
	subscriptionRepo repositories.SubscriptionRepository,
	logger *zap.Logger,
) *ProductSubscriptionService {
	return &ProductSubscriptionService{
		productRepo:      productRepo,
		subscriptionRepo: subscriptionRepo,
		logger:           logger,
	}
}

// UserSubscribedProductByCode 查找用户已订阅的产品
func (s *ProductSubscriptionService) UserSubscribedProductByCode(ctx context.Context, userID string, productCode string) (*entities.Subscription, error) {
	product, err := s.productRepo.FindByCode(ctx, productCode)
	if err != nil {
		return nil, err
	}
	subscription, err := s.subscriptionRepo.FindByUserAndProduct(ctx, userID, product.ID)
	if err != nil {
		return nil, err
	}
	return subscription, nil
}

// GetUserSubscribedProduct 查找用户已订阅的产品
func (s *ProductSubscriptionService) GetUserSubscribedProduct(ctx context.Context, userID string, productID string) (*entities.Subscription, error) {
	subscription, err := s.subscriptionRepo.FindByUserAndProduct(ctx, userID, productID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, nil
		}
		return nil, err
	}
	return subscription, nil
}

// CanUserSubscribeProduct 检查用户是否可以订阅产品
func (s *ProductSubscriptionService) CanUserSubscribeProduct(ctx context.Context, userID string, productID string) (bool, error) {
	// 检查产品是否存在且可订阅
	product, err := s.productRepo.GetByID(ctx, 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(ctx, userID, productID)
	if err == nil && existingSubscription != nil {
		return false, errors.New("用户已有该产品的订阅")
	}

	return true, nil
}

// CreateSubscription 创建订阅
func (s *ProductSubscriptionService) CreateSubscription(ctx context.Context, userID, productID string) (*entities.Subscription, error) {
	// 检查是否可以订阅
	canSubscribe, err := s.CanUserSubscribeProduct(ctx, userID, productID)
	if err != nil {
		return nil, err
	}
	if !canSubscribe {
		return nil, errors.New("无法订阅该产品")
	}

	// 获取产品信息以获取价格
	product, err := s.productRepo.GetByID(ctx, productID)
	if err != nil {
		return nil, fmt.Errorf("产品不存在: %w", err)
	}

	// 创建订阅
	subscription := &entities.Subscription{
		UserID:    userID,
		ProductID: productID,
		Price:     product.Price,
	}

	createdSubscription, err := s.subscriptionRepo.Create(ctx, *subscription)
	if err != nil {
		s.logger.Error("创建订阅失败", zap.Error(err))
		return nil, fmt.Errorf("创建订阅失败: %w", err)
	}

	s.logger.Info("订阅创建成功",
		zap.String("subscription_id", createdSubscription.ID),
		zap.String("user_id", userID),
		zap.String("product_id", productID),
	)

	return &createdSubscription, nil
}

// ListSubscriptions 获取订阅列表
func (s *ProductSubscriptionService) ListSubscriptions(ctx context.Context, query *queries.ListSubscriptionsQuery) ([]*entities.Subscription, int64, error) {
	return s.subscriptionRepo.ListSubscriptions(ctx, query)
}

// GetUserSubscriptions 获取用户订阅列表
func (s *ProductSubscriptionService) GetUserSubscriptions(ctx context.Context, userID string) ([]*entities.Subscription, error) {
	return s.subscriptionRepo.FindByUserID(ctx, userID)
}

// GetSubscriptionByID 根据ID获取订阅
func (s *ProductSubscriptionService) GetSubscriptionByID(ctx context.Context, subscriptionID string) (*entities.Subscription, error) {
	subscription, err := s.subscriptionRepo.GetByID(ctx, subscriptionID)
	if err != nil {
		return nil, fmt.Errorf("订阅不存在: %w", err)
	}
	return &subscription, nil
}

// CancelSubscription 取消订阅
func (s *ProductSubscriptionService) CancelSubscription(ctx context.Context, subscriptionID string) error {
	// 由于订阅实体没有状态字段，这里直接删除订阅
	if err := s.subscriptionRepo.Delete(ctx, subscriptionID); err != nil {
		s.logger.Error("取消订阅失败", zap.Error(err))
		return fmt.Errorf("取消订阅失败: %w", err)
	}

	s.logger.Info("订阅取消成功",
		zap.String("subscription_id", subscriptionID),
	)

	return nil
}

// GetProductStats 获取产品统计信息
func (s *ProductSubscriptionService) GetProductStats(ctx context.Context) (map[string]int64, error) {
	stats := make(map[string]int64)

	total, err := s.productRepo.CountByCategory(ctx, "")
	if err == nil {
		stats["total"] = total
	}

	enabled, err := s.productRepo.CountEnabled(ctx)
	if err == nil {
		stats["enabled"] = enabled
	}

	visible, err := s.productRepo.CountVisible(ctx)
	if err == nil {
		stats["visible"] = visible
	}

	return stats, nil
}

func (s *ProductSubscriptionService) SaveSubscription(ctx context.Context, subscription *entities.Subscription) error {
	exists, err := s.subscriptionRepo.Exists(ctx, subscription.ID)
	if err != nil {
		return fmt.Errorf("检查订阅是否存在失败: %w", err)
	}
	if exists {
		return s.subscriptionRepo.Update(ctx, *subscription)
	} else {
		_, err := s.subscriptionRepo.Create(ctx, *subscription)
		if err != nil {
			return fmt.Errorf("创建订阅失败: %w", err)
		}
		return nil
	}
}

// IncrementSubscriptionAPIUsage 增加订阅API使用次数（使用乐观锁，带重试机制）
func (s *ProductSubscriptionService) IncrementSubscriptionAPIUsage(ctx context.Context, subscriptionID string, increment int64) error {
	const maxRetries = 3
	const baseDelay = 10 * time.Millisecond

	for attempt := 0; attempt < maxRetries; attempt++ {
		// 使用乐观锁直接更新数据库
		err := s.subscriptionRepo.IncrementAPIUsageWithOptimisticLock(ctx, subscriptionID, increment)
		if err == nil {
			// 更新成功
			if attempt > 0 {
				s.logger.Info("订阅API使用次数更新成功（重试后）",
					zap.String("subscription_id", subscriptionID),
					zap.Int64("increment", increment),
					zap.Int("retry_count", attempt))
			} else {
				s.logger.Info("订阅API使用次数更新成功",
					zap.String("subscription_id", subscriptionID),
					zap.Int64("increment", increment))
			}
			return nil
		}

		// 检查是否是版本冲突错误
		if errors.Is(err, gorm.ErrRecordNotFound) {
			// 版本冲突，等待后重试
			if attempt < maxRetries-1 {
				delay := time.Duration(attempt+1) * baseDelay
				s.logger.Debug("订阅版本冲突，准备重试",
					zap.String("subscription_id", subscriptionID),
					zap.Int("attempt", attempt+1),
					zap.Duration("delay", delay))
				time.Sleep(delay)
				continue
			}
			// 最后一次重试失败
			s.logger.Error("订阅不存在或版本冲突，重试次数已用完",
				zap.String("subscription_id", subscriptionID),
				zap.Int("max_retries", maxRetries),
				zap.Error(err))
			return fmt.Errorf("订阅不存在或已被其他操作修改（重试%d次后失败）: %w", maxRetries, err)
		}

		// 其他错误直接返回，不重试
		s.logger.Error("更新订阅API使用次数失败",
			zap.String("subscription_id", subscriptionID),
			zap.Int64("increment", increment),
			zap.Error(err))
		return fmt.Errorf("更新订阅API使用次数失败: %w", err)
	}

	return fmt.Errorf("更新失败，已重试%d次", maxRetries)
}