AnCao/internal/handlers/exam_handler.go

package handlers

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

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

// CreateExamRequest 创建试卷请求
type CreateExamRequest struct {
	Title string `json:"title" binding:"required"`
}

// CreateExam 创建试卷
func CreateExam(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	var req CreateExamRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的请求数据: " + err.Error()})
		return
	}

	db := database.GetDB()

	// 查询用户信息，获取用户类型
	var user models.User
	if err := db.Where("id = ?", userID).First(&user).Error; err != nil {
		log.Printf("查询用户失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询用户信息失败"})
		return
	}

	// 使用固定的题型配置（总分100分）
	questionTypes := []models.QuestionTypeConfig{
		{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）
	}

	// 按题型配置随机抽取题目
	var allQuestionIDs []int64
	totalScore := 0.0

	for _, qtConfig := range questionTypes {
		var questions []models.PracticeQuestion
		query := db.Where("type = ?", qtConfig.Type)

		if err := query.Find(&questions).Error; err != nil {
			log.Printf("查询题目失败: %v", err)
			c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询题目失败"})
			return
		}

		// 检查题目数量是否足够
		if len(questions) < qtConfig.Count {
			c.JSON(http.StatusBadRequest, gin.H{
				"success": false,
				"message": fmt.Sprintf("题型 %s 题目数量不足，需要 %d 道，实际 %d 道", qtConfig.Type, qtConfig.Count, len(questions)),
			})
			return
		}

		// 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[:qtConfig.Count]

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

		// 计算总分
		totalScore += float64(qtConfig.Count) * qtConfig.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]
	}

	// 序列化题目ID
	questionIDsJSON, err := json.Marshal(allQuestionIDs)
	if err != nil {
		log.Printf("序列化题目ID失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "生成试卷失败"})
		return
	}

	// 创建试卷
	exam := models.Exam{
		UserID:      uint(userID.(int64)),
		Title:       req.Title,
		TotalScore:  int(totalScore), // 总分100分
		Duration:    60,              // 固定60分钟
		PassScore:   80,              // 固定80分及格
		QuestionIDs: questionIDsJSON,
		Status:      "active",
	}

	if err := db.Create(&exam).Error; err != nil {
		log.Printf("创建试卷失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "创建试卷失败"})
		return
	}

	// 返回试卷信息
	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data": gin.H{
			"id":             exam.ID,
			"title":          exam.Title,
			"total_score":    exam.TotalScore,
			"duration":       exam.Duration,
			"pass_score":     exam.PassScore,
			"question_count": len(allQuestionIDs),
			"created_at":     exam.CreatedAt,
		},
	})
}

// GetExamList 获取试卷列表
func GetExamList(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	db := database.GetDB()

	// 获取用户可访问的试卷（拥有的 + 被分享的）
	exams, err := models.GetAccessibleExams(userID.(int64), db)
	if err != nil {
		log.Printf("查询试卷列表失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询试卷列表失败"})
		return
	}

	// 为每个试卷添加统计信息
	type ExamWithStats struct {
		models.Exam
		QuestionCount      int     `json:"question_count"`
		AttemptCount       int     `json:"attempt_count"`                   // 考试次数（当前用户）
		BestScore          float64 `json:"best_score"`                      // 最高分（当前用户）
		HasInProgressExam  bool    `json:"has_in_progress_exam"`            // 是否有进行中的考试
		InProgressRecordID uint    `json:"in_progress_record_id,omitempty"` // 进行中的考试记录ID
		ParticipantCount   int     `json:"participant_count"`               // 共享试卷的参与人数（所有用户）
		IsShared           bool    `json:"is_shared"`                       // 是否为分享的试卷
		SharedBy           *struct {
			ID       int64  `json:"id"`
			Username string `json:"username"`
			Nickname string `json:"nickname"`
		} `json:"shared_by,omitempty"`
	}

	result := make([]ExamWithStats, 0, len(exams))
	for _, exam := range exams {
		var questionIDs []uint
		if err := json.Unmarshal(exam.QuestionIDs, &questionIDs); err != nil {
			continue
		}

		stats := ExamWithStats{
			Exam:          exam,
			QuestionCount: len(questionIDs),
		}

		// 检查是否为分享试卷
		if exam.UserID != uint(userID.(int64)) {
			stats.IsShared = true
			// 查询分享人信息
			var share models.ExamShare
			if err := db.Where("exam_id = ? AND shared_to_id = ?", exam.ID, userID.(int64)).
				Preload("SharedBy").First(&share).Error; err == nil && share.SharedBy != nil {
				stats.SharedBy = &struct {
					ID       int64  `json:"id"`
					Username string `json:"username"`
					Nickname string `json:"nickname"`
				}{
					ID:       share.SharedBy.ID,
					Username: share.SharedBy.Username,
					Nickname: share.SharedBy.Nickname,
				}
			}
		}

		// 当前用户的统计
		var count int64
		db.Model(&models.ExamRecord{}).Where("exam_id = ? AND user_id = ?", exam.ID, userID).Count(&count)
		stats.AttemptCount = int(count)

		var record models.ExamRecord
		if err := db.Where("exam_id = ? AND user_id = ?", exam.ID, userID).
			Order("score DESC").
			First(&record).Error; err == nil {
			stats.BestScore = record.Score
		}

		var inProgressRecord models.ExamRecord
		if err := db.Where("exam_id = ? AND user_id = ? AND status = ?", exam.ID, userID, "in_progress").
			Order("created_at DESC").
			First(&inProgressRecord).Error; err == nil {
			stats.HasInProgressExam = true
			stats.InProgressRecordID = inProgressRecord.ID
		}

		// 参与人数统计（简化：直接统计该试卷的不同用户）
		var participantCount int64
		db.Model(&models.ExamRecord{}).
			Where("exam_id = ? AND status = ?", exam.ID, "graded").
			Distinct("user_id").
			Count(&participantCount)
		stats.ParticipantCount = int(participantCount)

		result = append(result, stats)
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data":    result,
	})
}

// GetExamDetail 获取试卷详情
func GetExamDetail(c *gin.Context) {
	_, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	examIDStr := c.Param("id")
	examID, err := strconv.ParseUint(examIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的试卷ID"})
		return
	}

	// 检查是否需要显示答案
	showAnswer := c.Query("show_answer") == "true"

	db := database.GetDB()

	// 查询试卷
	var exam models.Exam
	if err := db.Where("id = ?", examID).First(&exam).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在"})
		return
	}

	// 解析题目ID列表
	var questionIDs []int64
	if err := json.Unmarshal(exam.QuestionIDs, &questionIDs); err != nil {
		log.Printf("解析题目ID失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "解析试卷数据失败"})
		return
	}

	// 查询题目详情
	var questions []models.PracticeQuestion
	if err := db.Where("id IN ?", questionIDs).Find(&questions).Error; err != nil {
		log.Printf("查询题目失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询题目失败"})
		return
	}

	// 按原始顺序排序题目并转换为DTO
	questionMap := make(map[int64]models.PracticeQuestion)
	for _, q := range questions {
		questionMap[q.ID] = q
	}

	// 检查是否包含论述题，如果没有则添加两种论述题
	hasOrdinaryEssay := false
	hasManagementEssay := false
	for _, q := range questions {
		if q.Type == "ordinary-essay" {
			hasOrdinaryEssay = true
		}
		if q.Type == "management-essay" {
			hasManagementEssay = true
		}
	}

	// 如果缺少论述题，则补充
	var additionalQuestions []models.PracticeQuestion
	if !hasOrdinaryEssay {
		var ordinaryEssay models.PracticeQuestion
		if err := db.Where("type = ?", "ordinary-essay").First(&ordinaryEssay).Error; err == nil {
			additionalQuestions = append(additionalQuestions, ordinaryEssay)
		}
	}
	if !hasManagementEssay {
		var managementEssay models.PracticeQuestion
		if err := db.Where("type = ?", "management-essay").First(&managementEssay).Error; err == nil {
			additionalQuestions = append(additionalQuestions, managementEssay)
		}
	}

	// 将补充的题目添加到题目映射中
	for _, q := range additionalQuestions {
		questionMap[q.ID] = q
	}

	orderedDTOs := make([]models.PracticeQuestionDTO, 0, len(questionIDs))
	for _, id := range questionIDs {
		if q, ok := questionMap[id]; ok {
			dto := convertToDTO(q)
			// 根据showAnswer参数决定是否显示答案
			if !showAnswer {
				dto.Answer = nil // 不显示答案
			}
			orderedDTOs = append(orderedDTOs, dto)
		}
	}

	// 添加补充的论述题到结果中
	for _, q := range additionalQuestions {
		dto := convertToDTO(q)
		if !showAnswer {
			dto.Answer = nil // 不显示答案
		}
		orderedDTOs = append(orderedDTOs, dto)
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data": gin.H{
			"exam":      exam,
			"questions": orderedDTOs,
		},
	})
}

// StartExam 开始考试（创建考试记录）
func StartExam(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	examIDStr := c.Param("id")
	examID, err := strconv.ParseUint(examIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的试卷ID"})
		return
	}

	db := database.GetDB()

	// 查询试卷
	var exam models.Exam
	if err := db.Where("id = ?", examID).First(&exam).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在"})
		return
	}

	// 创建考试记录
	now := time.Now()
	record := models.ExamRecord{
		ExamID:     uint(examID),
		UserID:     uint(userID.(int64)),
		StartTime:  &now,
		TotalScore: exam.TotalScore,
		Status:     "in_progress",
	}

	if err := db.Create(&record).Error; err != nil {
		log.Printf("创建考试记录失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "开始考试失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data": gin.H{
			"record_id":  record.ID,
			"start_time": record.StartTime,
			"duration":   exam.Duration,
		},
	})
}

// SubmitExam 提交试卷答案
func SubmitExam(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	recordIDStr := c.Param("record_id")
	recordID, err := strconv.ParseUint(recordIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的考试记录ID"})
		return
	}

	// 解析请求体
	var req struct {
		Answers map[string]interface{} `json:"answers"` // question_id -> answer (可选)
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的请求数据"})
		return
	}

	db := database.GetDB()

	// 查询考试记录
	var record models.ExamRecord
	if err := db.Where("id = ? AND user_id = ?", recordID, userID).First(&record).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "考试记录不存在"})
		return
	}

	// 检查是否已提交
	if record.Status == "submitted" || record.Status == "graded" {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "考试已提交"})
		return
	}

	// 查询试卷
	var exam models.Exam
	if err := db.Where("id = ?", record.ExamID).First(&exam).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在"})
		return
	}

	// 更新考试记录状态为已提交
	now := time.Now()
	record.Status = "submitted"
	record.SubmitTime = &now

	// 计算用时（秒）
	if record.StartTime != nil {
		duration := now.Sub(*record.StartTime)
		record.TimeSpent = int(duration.Seconds())

		// 确保用时不为负数（容错处理）
		if record.TimeSpent < 0 {
			log.Printf("警告: 计算出负的用时，开始时间=%v, 结束时间=%v", *record.StartTime, now)
			record.TimeSpent = 0
		}
	}

	if err := db.Save(&record).Error; err != nil {
		log.Printf("保存考试记录失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "提交考试失败"})
		return
	}

	// 立即返回成功响应
	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"message": "提交成功，正在阅卷中...",
		"data": gin.H{
			"record_id":   record.ID,
			"status":      "submitted",
			"time_spent":  record.TimeSpent,
			"total_score": exam.TotalScore,
		},
	})

	// 异步执行阅卷（从 exam_user_answers 表读取答案）
	go gradeExam(uint(recordID), exam.ID, uint(userID.(int64)))
}

// GetExamRecord 获取考试记录详情
func GetExamRecord(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	recordIDStr := c.Param("record_id")
	recordID, err := strconv.ParseUint(recordIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的考试记录ID"})
		return
	}

	db := database.GetDB()

	// 查询考试记录（不限制用户，因为可能是查看共享试卷的其他用户记录）
	var record models.ExamRecord
	if err := db.Where("id = ?", recordID).
		Preload("Exam").
		First(&record).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "考试记录不存在"})
		return
	}

	// 检查权限：只有以下情况可以查看
	// 1. 记录属于当前用户
	// 2. 当前用户有权限访问该试卷
	if record.UserID != uint(userID.(int64)) {
		// 不是自己的记录，检查是否有权限访问该试卷
		var exam models.Exam
		if err := db.Where("id = ?", record.ExamID).First(&exam).Error; err != nil {
			c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在"})
			return
		}

		if !exam.IsAccessibleBy(userID.(int64), db) {
			c.JSON(http.StatusForbidden, gin.H{"success": false, "message": "无权限查看此考试记录"})
			return
		}
	}

	// 从 exam_user_answers 表读取所有答案
	var userAnswers []models.ExamUserAnswer
	if err := db.Where("exam_record_id = ?", recordID).Find(&userAnswers).Error; err != nil {
		log.Printf("查询用户答案失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询答案失败"})
		return
	}

	// 查询所有题目以获取正确答案
	var questionIDs []uint
	if err := json.Unmarshal(record.Exam.QuestionIDs, &questionIDs); err != nil {
		log.Printf("解析题目ID失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "解析题目失败"})
		return
	}

	var questions []models.PracticeQuestion
	if err := db.Where("id IN ?", questionIDs).Find(&questions).Error; err != nil {
		log.Printf("查询题目失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询题目失败"})
		return
	}

	// 构建题目映射
	questionMap := make(map[int64]models.PracticeQuestion)
	for _, q := range questions {
		questionMap[q.ID] = q
	}

	// 构建 ExamAnswer 列表
	examAnswers := make([]models.ExamAnswer, 0, len(userAnswers))
	for _, ua := range userAnswers {
		// 解析用户答案
		var userAnswer interface{}
		if err := json.Unmarshal(ua.Answer, &userAnswer); err != nil {
			log.Printf("解析用户答案失败: %v", err)
			continue
		}

		// 获取题目并解析正确答案
		question, ok := questionMap[ua.QuestionID]
		if !ok {
			continue
		}

		var correctAnswerRaw interface{}
		switch question.Type {
		case "fill-in-blank", "multiple-selection", "multiple-choice":
			// 数组类型：需要 JSON 解析（单选题也是数组格式A）
			var arr []string
			if err := json.Unmarshal([]byte(question.AnswerData), &arr); err != nil {
				// 尝试解析为单个字符串（兼容旧数据格式）
				var singleStr string
				if err2 := json.Unmarshal([]byte(question.AnswerData), &singleStr); err2 == nil {
					// 成功解析为字符串，单选题直接使用，其他类型转为数组
					if question.Type == "multiple-choice" {
						correctAnswerRaw = singleStr
					} else {
						correctAnswerRaw = []string{singleStr}

					}
				} else {
					correctAnswerRaw = "解析失败"
				}
			} else {
				// 单选题只取第一个元素
				if question.Type == "multiple-choice" && len(arr) > 0 {
					correctAnswerRaw = arr[0]
				} else {
					correctAnswerRaw = arr
				}
			}
		default:
			// 字符串类型：直接使用 AnswerData（true-false, short-answer, essay）
			correctAnswerRaw = question.AnswerData
		}

		// 构建答案对象
		examAnswer := models.ExamAnswer{
			QuestionID:    ua.QuestionID,
			Answer:        userAnswer,
			CorrectAnswer: correctAnswerRaw,
			IsCorrect:     ua.IsCorrect != nil && *ua.IsCorrect,
			Score:         ua.Score,
		}

		// 添加 AI 评分信息
		if len(ua.AIGradingData) > 0 {
			var aiGrading models.AIGrading
			if err := json.Unmarshal(ua.AIGradingData, &aiGrading); err == nil {
				examAnswer.AIGrading = &aiGrading
			}
		}

		examAnswers = append(examAnswers, examAnswer)
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data": gin.H{
			"record":  record,
			"answers": examAnswers,
		},
	})
}

// GetExamRecordList 获取考试记录列表
func GetExamRecordList(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	examIDStr := c.Query("exam_id")
	db := database.GetDB()

	// 如果指定了试卷ID
	if examIDStr != "" {
		examID, err := strconv.ParseUint(examIDStr, 10, 32)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的试卷ID"})
			return
		}

		// 查询试卷并检查权限
		var exam models.Exam
		if err := db.Where("id = ?", examID).First(&exam).Error; err != nil {
			c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在"})
			return
		}

		// 检查用户是否有权限访问该试卷
		if !exam.IsAccessibleBy(userID.(int64), db) {
			c.JSON(http.StatusForbidden, gin.H{"success": false, "message": "无权限访问"})
			return
		}

		// 查询该试卷的所有已完成考试记录（包含用户信息）
		var records []models.ExamRecord
		if err := db.Where("exam_id = ? AND status = ?", examID, "graded").
			Preload("Exam").
			Preload("User", func(db *gorm.DB) *gorm.DB {
				return db.Select("id", "username", "nickname", "avatar")
			}).
			Order("score DESC, created_at DESC").
			Find(&records).Error; err != nil {
			log.Printf("查询考试记录失败: %v", err)
			c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询考试记录失败"})
			return
		}

		c.JSON(http.StatusOK, gin.H{
			"success": true,
			"data":    records,
		})
		return
	}

	// 没有指定试卷ID，返回当前用户的所有记录
	var records []models.ExamRecord
	if err := db.Where("user_id = ?", userID).
		Preload("Exam").
		Order("created_at DESC").
		Find(&records).Error; err != nil {
		log.Printf("查询考试记录失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询考试记录失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data":    records,
	})
}

// DeleteExam 删除试卷
func DeleteExam(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	examIDStr := c.Param("id")
	examID, err := strconv.ParseUint(examIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的试卷ID"})
		return
	}

	db := database.GetDB()

	// 查询试卷
	var exam models.Exam
	if err := db.Where("id = ? AND user_id = ?", examID, userID).First(&exam).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在"})
		return
	}

	// 软删除
	if err := db.Delete(&exam).Error; err != nil {
		log.Printf("删除试卷失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "删除试卷失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"message": "删除成功",
	})
}

// SaveExamProgressRequest 保存考试进度请求
type SaveExamProgressRequest struct {
	QuestionID int64       `json:"question_id"` // 题目ID
	Answer     interface{} `json:"answer"`      // 答案数据
}

// SaveExamProgress 保存单题答案
func SaveExamProgress(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	recordIDStr := c.Param("record_id")
	recordID, err := strconv.ParseInt(recordIDStr, 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的考试记录ID"})
		return
	}

	var req SaveExamProgressRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的请求数据"})
		return
	}

	db := database.GetDB()

	// 查询考试记录
	var record models.ExamRecord
	if err := db.Where("id = ? AND user_id = ?", recordID, userID).First(&record).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "考试记录不存在"})
		return
	}

	// 检查考试状态
	if record.Status != "in_progress" {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "考试已结束，无法保存答案"})
		return
	}

	// 序列化答案数据
	answerJSON, err := json.Marshal(req.Answer)
	if err != nil {
		log.Printf("序列化答案失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "保存失败"})
		return
	}

	now := time.Now()

	// 查找是否已存在该题的答案
	var userAnswer models.ExamUserAnswer
	result := db.Where("exam_record_id = ? AND question_id = ?", recordID, req.QuestionID).First(&userAnswer)

	if result.Error == gorm.ErrRecordNotFound {
		// 不存在，创建新记录
		userAnswer = models.ExamUserAnswer{
			ExamRecordID:   recordID,
			QuestionID:     req.QuestionID,
			UserID:         userID.(int64),
			Answer:         answerJSON,
			AnsweredAt:     &now,
			LastModifiedAt: now,
		}
		if err := db.Create(&userAnswer).Error; err != nil {
			log.Printf("创建答案记录失败: %v", err)
			c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "保存答案失败"})
			return
		}
	} else if result.Error != nil {
		log.Printf("查询答案记录失败: %v", result.Error)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询答案失败"})
		return
	} else {
		// 已存在，更新答案
		updates := map[string]interface{}{
			"answer":           answerJSON,
			"last_modified_at": now,
		}
		if err := db.Model(&userAnswer).Updates(updates).Error; err != nil {
			log.Printf("更新答案记录失败: %v", err)
			c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "更新答案失败"})
			return
		}
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"message": "保存成功",
	})
}

// GetExamUserAnswers 获取用户在考试中的所有答案
func GetExamUserAnswers(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	recordIDStr := c.Param("record_id")
	recordID, err := strconv.ParseUint(recordIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的考试记录ID"})
		return
	}

	db := database.GetDB()

	// 查询考试记录，确保用户有权限
	var record models.ExamRecord
	if err := db.Where("id = ? AND user_id = ?", recordID, userID).First(&record).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "考试记录不存在"})
		return
	}

	// 查询所有已保存的答案
	var userAnswers []models.ExamUserAnswer
	if err := db.Where("exam_record_id = ?", recordID).Find(&userAnswers).Error; err != nil {
		log.Printf("查询用户答案失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询答案失败"})
		return
	}

	// 转换为前端需要的格式: { question_id: answer }
	answers := make(map[string]interface{})
	for _, ua := range userAnswers {
		var answer interface{}
		if err := json.Unmarshal(ua.Answer, &answer); err != nil {
			log.Printf("解析答案失败: %v", err)
			continue
		}
		// 使用 q_<question_id> 格式作为key，与前端表单字段名保持一致
		fieldName := fmt.Sprintf("q_%d", ua.QuestionID)
		answers[fieldName] = answer
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data":    answers,
	})
}

// GetShareableUsers 获取可分享的用户列表（排除当前用户）
func GetShareableUsers(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	db := database.GetDB()

	// 查询所有用户（排除当前用户）
	var users []models.User
	if err := db.Where("id != ?", userID).Select("id", "username", "nickname", "avatar").Find(&users).Error; err != nil {
		log.Printf("查询用户列表失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "查询用户列表失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"data":    users,
	})
}

// ShareExamRequest 分享试卷请求
type ShareExamRequest struct {
	UserIDs []uint `json:"user_ids" binding:"required,min=1"` // 分享给哪些用户
}

// ShareExam 分享试卷
func ShareExam(c *gin.Context) {
	userID, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "未登录"})
		return
	}

	examIDStr := c.Param("id")
	examID, err := strconv.ParseUint(examIDStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的试卷ID"})
		return
	}

	var req ShareExamRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "无效的请求数据: " + err.Error()})
		return
	}

	db := database.GetDB()

	// 查询原始试卷，确认用户有权限分享
	var exam models.Exam
	if err := db.Where("id = ? AND user_id = ?", examID, userID).First(&exam).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"success": false, "message": "试卷不存在或无权限"})
		return
	}

	// 开始事务
	tx := db.Begin()
	defer func() {
		if r := recover(); r != nil {
			tx.Rollback()
		}
	}()

	sharedByID := userID.(int64)
	sharedCount := 0
	now := time.Now()

	// 为每个用户创建分享记录
	for _, targetUserID := range req.UserIDs {
		// 检查是否已分享
		var existingShare models.ExamShare
		err := tx.Where("exam_id = ? AND shared_to_id = ?", uint(examID), int64(targetUserID)).
			First(&existingShare).Error

		if err == nil {
			continue // 已存在，跳过
		} else if err != gorm.ErrRecordNotFound {
			tx.Rollback()
			log.Printf("检查分享记录失败: %v", err)
			c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "分享失败"})
			return
		}

		// 创建分享记录
		share := models.ExamShare{
			ExamID:     uint(examID),
			SharedByID: sharedByID,
			SharedToID: int64(targetUserID),
			SharedAt:   now,
		}

		if err := tx.Create(&share).Error; err != nil {
			tx.Rollback()
			log.Printf("创建分享记录失败: %v", err)
			c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "分享失败"})
			return
		}
		sharedCount++
	}

	// 提交事务
	if err := tx.Commit().Error; err != nil {
		log.Printf("提交事务失败: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "分享失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"message": fmt.Sprintf("成功分享给 %d 个用户", sharedCount),
		"data": gin.H{
			"shared_count": sharedCount,
		},
	})
}