package service

import (
	"fmt"

	"dd_fiber_api/internal/question"
	"dd_fiber_api/internal/question/dao"
)

// KnowledgeTreeService 知识树服务
type KnowledgeTreeService struct {
	knowledgeTreeDAO dao.KnowledgeTreeDAOInterface
}

// NewKnowledgeTreeService 创建知识树服务
func NewKnowledgeTreeService(knowledgeTreeDAO dao.KnowledgeTreeDAOInterface) *KnowledgeTreeService {
	return &KnowledgeTreeService{
		knowledgeTreeDAO: knowledgeTreeDAO,
	}
}

// CreateKnowledgeTreeNode 创建知识树节点
func (s *KnowledgeTreeService) CreateKnowledgeTreeNode(req *CreateKnowledgeTreeNodeRequest) (*question.KnowledgeTree, error) {
	nodeID := question.GenerateID()
	now := question.GetCurrentTimestamp()

	node := &question.KnowledgeTree{
		ID:        nodeID,
		Type:      req.Type,
		Title:     req.Title,
		ParentID:  req.ParentID,
		CreatedAt: now,
		UpdatedAt: now,
	}

	if err := s.knowledgeTreeDAO.Create(node); err != nil {
		return nil, fmt.Errorf("创建知识树节点失败: %v", err)
	}

	return node, nil
}

// GetKnowledgeTreeNode 获取知识树节点
func (s *KnowledgeTreeService) GetKnowledgeTreeNode(id string) (*question.KnowledgeTree, error) {
	return s.knowledgeTreeDAO.GetByID(id)
}

// GetKnowledgeTreeNames 获取知识树名称，返回 id -> 标题 的映射；不存在的节点跳过，不报错
func (s *KnowledgeTreeService) GetKnowledgeTreeNames(ids []string) (map[string]string, error) {
	idToName := make(map[string]string, len(ids))
	for _, id := range ids {
		if id == "" {
			continue
		}
		tree, err := s.knowledgeTreeDAO.GetByID(id)
		if err != nil {
			// 知识树节点不存在或已删除时跳过，不影响整体结果
			continue
		}
		idToName[id] = tree.Title
	}
	return idToName, nil
}

// GetAllKnowledgeTreeNodes 获取所有知识树节点（扁平列表）
func (s *KnowledgeTreeService) GetAllKnowledgeTreeNodes(treeType question.KnowledgeTreeType) ([]*question.KnowledgeTree, error) {
	return s.knowledgeTreeDAO.GetAll(treeType)
}

// GetKnowledgeTreeByParentID 根据父节点ID获取子节点列表
func (s *KnowledgeTreeService) GetKnowledgeTreeByParentID(parentID string, treeType question.KnowledgeTreeType) ([]*question.KnowledgeTree, error) {
	return s.knowledgeTreeDAO.GetByParentID(parentID, treeType)
}

// GetKnowledgeTree 获取完整树形结构
func (s *KnowledgeTreeService) GetKnowledgeTree(treeType question.KnowledgeTreeType) ([]*question.KnowledgeTree, error) {
	return s.knowledgeTreeDAO.GetTree(treeType)
}

// UpdateKnowledgeTreeNode 更新知识树节点
func (s *KnowledgeTreeService) UpdateKnowledgeTreeNode(req *UpdateKnowledgeTreeNodeRequest) error {
	// 先获取现有节点
	existingNode, err := s.knowledgeTreeDAO.GetByID(req.ID)
	if err != nil {
		return fmt.Errorf("知识树节点不存在: %v", err)
	}

	// 更新字段
	existingNode.Title = req.Title
	existingNode.ParentID = req.ParentID
	existingNode.UpdatedAt = question.GetCurrentTimestamp()

	if err := s.knowledgeTreeDAO.Update(existingNode); err != nil {
		return fmt.Errorf("更新知识树节点失败: %v", err)
	}

	return nil
}

// DeleteKnowledgeTreeNode 删除知识树节点
func (s *KnowledgeTreeService) DeleteKnowledgeTreeNode(id string) error {
	// 先获取节点，获取类型
	existingNode, err := s.knowledgeTreeDAO.GetByID(id)
	if err != nil {
		return fmt.Errorf("知识树节点不存在: %v", err)
	}

	// 检查是否有子节点
	children, err := s.knowledgeTreeDAO.GetByParentID(id, existingNode.Type)
	if err != nil {
		return fmt.Errorf("查询子节点失败: %v", err)
	}

	if len(children) > 0 {
		return fmt.Errorf("该节点存在子节点，无法删除")
	}

	if err := s.knowledgeTreeDAO.Delete(id); err != nil {
		return fmt.Errorf("删除知识树节点失败: %v", err)
	}

	return nil
}

// CreateKnowledgeTreeNodeRequest 创建知识树节点请求
type CreateKnowledgeTreeNodeRequest struct {
	Type     question.KnowledgeTreeType `json:"type" binding:"required"`  // 知识树类型：objective（客观题）或 subjective（主观题）
	Title    string                     `json:"title" binding:"required"` // 节点标题
	ParentID string                     `json:"parent_id"`                // 父节点ID，根节点为空字符串
}

// UpdateKnowledgeTreeNodeRequest 更新知识树节点请求
type UpdateKnowledgeTreeNodeRequest struct {
	ID       string `json:"id" binding:"required"`    // 节点ID
	Title    string `json:"title" binding:"required"` // 节点标题
	ParentID string `json:"parent_id"`                // 父节点ID
}