012-kaopeilian/backend/app/services/exam_service.py

"""
考试服务层
"""
import json
import random
from datetime import datetime, timedelta
from typing import List, Optional, Dict, Any
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func, and_, or_, desc
from app.models.exam import Exam, Question, ExamResult
from app.models.exam_mistake import ExamMistake
from app.models.course import Course, KnowledgePoint
from app.core.exceptions import BusinessException, ErrorCode
from app.utils.score_distributor import ScoreDistributor


class ExamService:
    """考试服务类"""

    @staticmethod
    async def start_exam(
        db: AsyncSession, user_id: int, course_id: int, question_count: int = 10
    ) -> Exam:
        """
        开始考试

        Args:
            db: 数据库会话
            user_id: 用户ID
            course_id: 课程ID
            question_count: 题目数量

        Returns:
            Exam: 考试实例
        """
        # 检查课程是否存在
        course = await db.get(Course, course_id)
        if not course:
            raise BusinessException(error_code=ErrorCode.NOT_FOUND, message="课程不存在")

        # 获取该课程的所有可用题目
        stmt = select(Question).where(
            and_(Question.course_id == course_id, Question.is_active == True)
        )
        result = await db.execute(stmt)
        all_questions = result.scalars().all()

        if not all_questions:
            raise BusinessException(
                error_code=ErrorCode.VALIDATION_ERROR, message="该课程暂无题目"
            )

        # 随机选择题目
        selected_questions = random.sample(
            all_questions, min(question_count, len(all_questions))
        )

        # 使用智能分数分配器，确保总分为整数且分配合理
        total_score = 100.0  # 固定总分为100分
        actual_question_count = len(selected_questions)
        
        # 创建分数分配器
        distributor = ScoreDistributor(total_score, actual_question_count)
        distributed_scores = distributor.distribute(mode="integer")

        # 构建题目数据，使用分配后的分数
        questions_data = []
        for i, q in enumerate(selected_questions):
            question_data = {
                "id": str(q.id),
                "type": q.question_type,
                "title": q.title,
                "content": q.content,
                "options": q.options,
                "score": distributed_scores[i],  # 使用智能分配的分数
            }
            questions_data.append(question_data)

        # 计算及格分数（向上取整，确保公平）
        pass_score = ScoreDistributor.calculate_pass_score(total_score, 0.6)

        # 创建考试记录
        exam = Exam(
            user_id=user_id,
            course_id=course_id,
            exam_name=f"{course.name} - 随机测试",
            question_count=actual_question_count,
            total_score=total_score,
            pass_score=pass_score,
            duration_minutes=60,
            status="started",
            questions={"questions": questions_data},
        )

        db.add(exam)
        await db.commit()
        await db.refresh(exam)

        return exam

    @staticmethod
    async def submit_exam(
        db: AsyncSession, user_id: int, exam_id: int, answers: List[Dict[str, str]]
    ) -> Dict[str, Any]:
        """
        提交考试答案

        Args:
            db: 数据库会话
            user_id: 用户ID
            exam_id: 考试ID
            answers: 答案列表

        Returns:
            Dict: 考试结果
        """
        # 获取考试记录
        stmt = select(Exam).where(and_(Exam.id == exam_id, Exam.user_id == user_id))
        result = await db.execute(stmt)
        exam = result.scalar_one_or_none()

        if not exam:
            raise BusinessException(error_code=ErrorCode.NOT_FOUND, message="考试记录不存在")

        if exam.status != "started":
            raise BusinessException(
                error_code=ErrorCode.VALIDATION_ERROR, message="考试已结束或已提交"
            )

        # 检查考试是否超时
        if datetime.now() > exam.start_time + timedelta(
            minutes=exam.duration_minutes
        ):
            exam.status = "timeout"
            await db.commit()
            raise BusinessException(
                error_code=ErrorCode.VALIDATION_ERROR, message="考试已超时"
            )

        # 处理答案
        answers_dict = {ans["question_id"]: ans["answer"] for ans in answers}
        total_score = 0.0
        correct_count = 0

        # 批量获取题目
        question_ids = [int(ans["question_id"]) for ans in answers]
        stmt = select(Question).where(Question.id.in_(question_ids))
        result = await db.execute(stmt)
        questions_map = {str(q.id): q for q in result.scalars().all()}

        # 创建答题结果记录
        for question_data in exam.questions["questions"]:
            question_id = question_data["id"]
            question = questions_map.get(question_id)
            
            # 使用考试创建时分配的分数（智能分配后的整数分数）
            allocated_score = question_data.get("score", 10.0)

            if not question:
                continue

            user_answer = answers_dict.get(question_id, "")
            is_correct = user_answer == question.correct_answer

            if is_correct:
                total_score += allocated_score  # 使用分配的分数
                correct_count += 1

            # 创建答题结果记录
            exam_result = ExamResult(
                exam_id=exam_id,
                question_id=int(question_id),
                user_answer=user_answer,
                is_correct=is_correct,
                score=allocated_score if is_correct else 0.0,  # 使用分配的分数
            )
            db.add(exam_result)

            # 更新题目使用统计
            question.usage_count += 1
            if is_correct:
                question.correct_count += 1

        # 更新考试记录
        exam.end_time = datetime.now()
        exam.score = total_score
        exam.is_passed = total_score >= exam.pass_score
        exam.status = "submitted"
        exam.answers = {"answers": answers}

        await db.commit()

        return {
            "exam_id": exam_id,
            "total_score": total_score,
            "pass_score": exam.pass_score,
            "is_passed": exam.is_passed,
            "correct_count": correct_count,
            "total_count": exam.question_count,
            "accuracy": correct_count / exam.question_count
            if exam.question_count > 0
            else 0,
        }

    @staticmethod
    async def get_exam_detail(
        db: AsyncSession, user_id: int, exam_id: int
    ) -> Dict[str, Any]:
        """
        获取考试详情

        Args:
            db: 数据库会话
            user_id: 用户ID
            exam_id: 考试ID

        Returns:
            Dict: 考试详情
        """
        # 获取考试记录
        stmt = select(Exam).where(and_(Exam.id == exam_id, Exam.user_id == user_id))
        result = await db.execute(stmt)
        exam = result.scalar_one_or_none()

        if not exam:
            raise BusinessException(error_code=ErrorCode.NOT_FOUND, message="考试记录不存在")

        # 构建返回数据
        exam_data = {
            "id": exam.id,
            "course_id": exam.course_id,
            "exam_name": exam.exam_name,
            "question_count": exam.question_count,
            "total_score": exam.total_score,
            "pass_score": exam.pass_score,
            "start_time": exam.start_time.isoformat() if exam.start_time else None,
            "end_time": exam.end_time.isoformat() if exam.end_time else None,
            "duration_minutes": exam.duration_minutes,
            "status": exam.status,
            "score": exam.score,
            "is_passed": exam.is_passed,
            "questions": exam.questions,
        }

        # 如果考试已提交，获取答题详情
        if exam.status == "submitted" and exam.answers:
            stmt = select(ExamResult).where(ExamResult.exam_id == exam_id)
            result = await db.execute(stmt)
            results = result.scalars().all()

            results_data = []
            for r in results:
                results_data.append(
                    {
                        "question_id": r.question_id,
                        "user_answer": r.user_answer,
                        "is_correct": r.is_correct,
                        "score": r.score,
                    }
                )

            exam_data["results"] = results_data
            exam_data["answers"] = exam.answers

        return exam_data

    @staticmethod
    async def get_exam_records(
        db: AsyncSession,
        user_id: int,
        page: int = 1,
        size: int = 10,
        course_id: Optional[int] = None,
    ) -> Dict[str, Any]:
        """
        获取考试记录列表（包含统计数据）

        Args:
            db: 数据库会话
            user_id: 用户ID
            page: 页码
            size: 每页数量
            course_id: 课程ID（可选）

        Returns:
            Dict: 考试记录列表（包含统计信息）
        """
        # 构建查询条件
        conditions = [Exam.user_id == user_id]
        if course_id:
            conditions.append(Exam.course_id == course_id)

        # 查询总数
        count_stmt = select(func.count(Exam.id)).where(and_(*conditions))
        total = await db.scalar(count_stmt)

        # 查询考试数据（JOIN courses表获取课程名称）
        offset = (page - 1) * size
        stmt = (
            select(Exam, Course.name.label("course_name"))
            .join(Course, Exam.course_id == Course.id)
            .where(and_(*conditions))
            .order_by(Exam.created_at.desc())
            .offset(offset)
            .limit(size)
        )
        result = await db.execute(stmt)
        rows = result.all()

        # 构建返回数据
        items = []
        for exam, course_name in rows:
            # 1. 计算用时
            duration_seconds = None
            if exam.start_time and exam.end_time:
                duration_seconds = int((exam.end_time - exam.start_time).total_seconds())
            
            # 2. 统计错题数
            mistakes_stmt = select(func.count(ExamMistake.id)).where(
                ExamMistake.exam_id == exam.id
            )
            wrong_count = await db.scalar(mistakes_stmt) or 0
            
            # 3. 计算正确数和正确率
            correct_count = exam.question_count - wrong_count if exam.question_count else 0
            accuracy = None
            if exam.question_count and exam.question_count > 0:
                accuracy = round((correct_count / exam.question_count) * 100, 1)
            
            # 4. 分题型统计
            question_type_stats = []
            if exam.questions:
                try:
                    # 解析questions JSON，统计每种题型的总数
                    questions_data = json.loads(exam.questions) if isinstance(exam.questions, str) else exam.questions
                    type_totals = {}
                    type_scores = {}  # 存储每种题型的总分
                    
                    for q in questions_data:
                        q_type = q.get("type", "unknown")
                        q_score = q.get("score", 0)
                        type_totals[q_type] = type_totals.get(q_type, 0) + 1
                        type_scores[q_type] = type_scores.get(q_type, 0) + q_score
                    
                    # 查询错题按题型统计
                    mistakes_by_type_stmt = (
                        select(ExamMistake.question_type, func.count(ExamMistake.id))
                        .where(ExamMistake.exam_id == exam.id)
                        .group_by(ExamMistake.question_type)
                    )
                    mistakes_by_type_result = await db.execute(mistakes_by_type_stmt)
                    mistakes_by_type = dict(mistakes_by_type_result.all())
                    
                    # 题型名称映射
                    type_name_map = {
                        "single": "单选题",
                        "multiple": "多选题",
                        "judge": "判断题",
                        "blank": "填空题",
                        "essay": "问答题"
                    }
                    
                    # 组装分题型统计
                    for q_type, total in type_totals.items():
                        wrong = mistakes_by_type.get(q_type, 0)
                        correct = total - wrong
                        type_accuracy = round((correct / total) * 100, 1) if total > 0 else 0
                        
                        question_type_stats.append({
                            "type": type_name_map.get(q_type, q_type),
                            "type_code": q_type,
                            "total": total,
                            "correct": correct,
                            "wrong": wrong,
                            "accuracy": type_accuracy,
                            "total_score": type_scores.get(q_type, 0)
                        })
                except (json.JSONDecodeError, TypeError, KeyError) as e:
                    # 如果JSON解析失败，返回空统计
                    question_type_stats = []
            
            items.append(
                {
                    "id": exam.id,
                    "course_id": exam.course_id,
                    "course_name": course_name,
                    "exam_name": exam.exam_name,
                    "question_count": exam.question_count,
                    "total_score": exam.total_score,
                    "score": exam.score,
                    "is_passed": exam.is_passed,
                    "status": exam.status,
                    "start_time": exam.start_time.isoformat() if exam.start_time else None,
                    "end_time": exam.end_time.isoformat() if exam.end_time else None,
                    "created_at": exam.created_at.isoformat(),
                    # 统计字段
                    "accuracy": accuracy,
                    "correct_count": correct_count,
                    "wrong_count": wrong_count,
                    "duration_seconds": duration_seconds,
                    "question_type_stats": question_type_stats,
                }
            )

        return {
            "items": items,
            "total": total,
            "page": page,
            "size": size,
            "pages": (total + size - 1) // size,
        }

    @staticmethod
    async def get_exam_statistics(
        db: AsyncSession, user_id: int, course_id: Optional[int] = None
    ) -> Dict[str, Any]:
        """
        获取考试统计信息

        Args:
            db: 数据库会话
            user_id: 用户ID
            course_id: 课程ID（可选）

        Returns:
            Dict: 统计信息
        """
        # 构建查询条件
        conditions = [Exam.user_id == user_id, Exam.status == "submitted"]
        if course_id:
            conditions.append(Exam.course_id == course_id)

        # 查询统计数据
        stmt = select(
            func.count(Exam.id).label("total_exams"),
            func.count(func.nullif(Exam.is_passed, False)).label("passed_exams"),
            func.avg(Exam.score).label("avg_score"),
            func.max(Exam.score).label("max_score"),
            func.min(Exam.score).label("min_score"),
        ).where(and_(*conditions))

        result = await db.execute(stmt)
        stats = result.one()

        return {
            "total_exams": stats.total_exams or 0,
            "passed_exams": stats.passed_exams or 0,
            "pass_rate": (stats.passed_exams / stats.total_exams * 100)
            if stats.total_exams > 0
            else 0,
            "avg_score": float(stats.avg_score or 0),
            "max_score": float(stats.max_score or 0),
            "min_score": float(stats.min_score or 0),
        }