AnCao/internal/services/daily_exam_service.go

package services

import (
	"ankao/internal/database"
	"ankao/internal/models"
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"time"

	"gorm.io/gorm"
)

type DailyExamService struct {
	db *gorm.DB
}

func NewDailyExamService() *DailyExamService {
	return &DailyExamService{
		db: database.GetDB(),
	}
}

// GenerateDailyExam 生成每日一练试卷
func (s *DailyExamService) GenerateDailyExam() error {
	// 1. 获取分布式锁（使用日期作为锁ID）
	today := time.Now().Format("20060102")
	lockID := hashString(today) // 使用日期哈希作为锁ID

	var locked bool
	if err := s.db.Raw("SELECT pg_try_advisory_lock(?)", lockID).Scan(&locked).Error; err != nil {
		return fmt.Errorf("获取锁失败: %w", err)
	}

	if !locked {
		log.Println("其他实例正在生成每日一练，跳过")
		return nil
	}
	defer s.db.Exec("SELECT pg_advisory_unlock(?)", lockID)

	// 2. 检查今天是否已生成
	todayStart := time.Now().Truncate(24 * time.Hour)
	todayEnd := todayStart.Add(24 * time.Hour)

	var count int64
	s.db.Model(&models.Exam{}).
		Where("is_system = ? AND created_at >= ? AND created_at < ?",
			true, todayStart, todayEnd).
		Count(&count)

	if count > 0 {
		log.Println("今日每日一练已生成，跳过")
		return nil
	}

	// 3. 生成试卷标题
	now := time.Now()
	title := fmt.Sprintf("%d年%02d月%02d日的每日一练",
		now.Year(), now.Month(), now.Day())

	// 4. 随机选择题目（使用与创建试卷相同的逻辑）
	questionIDs, totalScore, err := s.selectQuestions()
	if err != nil {
		return fmt.Errorf("选择题目失败: %w", err)
	}

	questionIDsJSON, _ := json.Marshal(questionIDs)

	// 5. 创建试卷（使用第一个用户作为创建者，但标记为系统试卷）
	// 获取第一个用户ID
	var firstUser models.User
	if err := s.db.Order("id ASC").First(&firstUser).Error; err != nil {
		return fmt.Errorf("查询用户失败: %w", err)
	}

	exam := models.Exam{
		UserID:      uint(firstUser.ID), // 使用第一个用户作为创建者
		Title:       title,
		TotalScore:  int(totalScore),
		Duration:    60,
		PassScore:   80,
		QuestionIDs: questionIDsJSON,
		Status:      "active",
		IsSystem:    true, // 标记为系统试卷
	}

	if err := s.db.Create(&exam).Error; err != nil {
		return fmt.Errorf("创建试卷失败: %w", err)
	}

	log.Printf("成功创建每日一练试卷: ID=%d, Title=%s", exam.ID, exam.Title)

	// 6. 分享给所有用户
	if err := s.shareToAllUsers(exam.ID, uint(firstUser.ID)); err != nil {
		log.Printf("分享试卷失败: %v", err)
		// 不返回错误，因为试卷已创建成功
	}

	return nil
}

// selectQuestions 选择题目（复用现有逻辑）
func (s *DailyExamService) selectQuestions() ([]int64, float64, error) {
	questionTypes := []struct {
		Type  string
		Count int
		Score float64
	}{
		{Type: "fill-in-blank", Count: 20, Score: 2.0},      // 40分
		{Type: "true-false", Count: 10, Score: 1.0},         // 10分
		{Type: "multiple-choice", Count: 10, Score: 1.0},    // 10分
		{Type: "multiple-selection", Count: 10, Score: 2.0}, // 20分
		{Type: "short-answer", Count: 1, Score: 10.0},       // 10分
		{Type: "ordinary-essay", Count: 1, Score: 10.0},     // 10分（普通涉密人员论述题）
		{Type: "management-essay", Count: 1, Score: 10.0},   // 10分（保密管理人员论述题）
	}

	var allQuestionIDs []int64
	var totalScore float64

	for _, qt := range questionTypes {
		var questions []models.PracticeQuestion
		if err := s.db.Where("type = ?", qt.Type).Find(&questions).Error; err != nil {
			return nil, 0, err
		}

		// 检查题目数量是否足够
		if len(questions) < qt.Count {
			return nil, 0, fmt.Errorf("题型 %s 题目数量不足，需要 %d 道，实际 %d 道",
				qt.Type, qt.Count, len(questions))
		}

		// 随机抽取 (Fisher-Yates 洗牌算法)
		rand.Seed(time.Now().UnixNano())
		for i := len(questions) - 1; i > 0; i-- {
			j := rand.Intn(i + 1)
			questions[i], questions[j] = questions[j], questions[i]
		}
		selectedQuestions := questions[:qt.Count]

		for _, q := range selectedQuestions {
			allQuestionIDs = append(allQuestionIDs, q.ID)
		}

		totalScore += float64(qt.Count) * qt.Score
	}

	// 随机打乱题目ID顺序
	rand.Seed(time.Now().UnixNano())
	for i := len(allQuestionIDs) - 1; i > 0; i-- {
		j := rand.Intn(i + 1)
		allQuestionIDs[i], allQuestionIDs[j] = allQuestionIDs[j], allQuestionIDs[i]
	}

	return allQuestionIDs, totalScore, nil
}

// shareToAllUsers 分享给所有用户
func (s *DailyExamService) shareToAllUsers(examID uint, sharedByID uint) error {
	// 查询所有用户（排除创建者）
	var users []models.User
	if err := s.db.Where("id != ?", sharedByID).Find(&users).Error; err != nil {
		return err
	}

	// 批量创建分享记录
	now := time.Now()
	shares := make([]models.ExamShare, 0, len(users))
	for _, user := range users {
		shares = append(shares, models.ExamShare{
			ExamID:     examID,
			SharedByID: int64(sharedByID),
			SharedToID: int64(user.ID),
			SharedAt:   now,
		})
	}

	if len(shares) > 0 {
		// 批量插入
		if err := s.db.Create(&shares).Error; err != nil {
			return err
		}
		log.Printf("成功分享给 %d 个用户", len(shares))
	}

	return nil
}

// hashString 计算字符串哈希值（用于生成锁ID）
func hashString(s string) int64 {
	var hash int64
	for _, c := range s {
		hash = hash*31 + int64(c)
	}
	// 确保返回正数
	if hash < 0 {
		hash = -hash
	}
	return hash
}