math_cms/app/Services/ExamPdfExportService.php

<?php

namespace App\Services;

use App\DTO\ExamAnalysisDataDto;
use App\DTO\ReportPayloadDto;
use App\Models\Paper;
use App\Models\PaperQuestion;
use App\Models\Student;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\File;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Facades\URL;
use Symfony\Component\Process\Exception\ProcessSignaledException;
use Symfony\Component\Process\Exception\ProcessTimedOutException;
use Symfony\Component\Process\Process;

/**
 * PDF导出服务（重构版）
 * 负责生成试卷PDF、判卷PDF和学情报告PDF
 */
class ExamPdfExportService
{
    private ?KatexRenderer $katexRenderer = null;

    public function __construct(
        private readonly LearningAnalyticsService $learningAnalyticsService,
        private readonly QuestionBankService $questionBankService,
        private readonly QuestionServiceApi $questionServiceApi,
        private readonly PdfStorageService $pdfStorageService,
        private readonly MasteryCalculator $masteryCalculator,
        private readonly PdfMerger $pdfMerger
    ) {
        // 延迟初始化 KatexRenderer（避免循环依赖）
        $this->katexRenderer = new KatexRenderer();
    }

    /**
     * 生成试卷 PDF（不含答案）
     */
    public function generateExamPdf(string $paperId): ?string
    {
        Log::info('generateExamPdf 开始：', ['paper_id' => $paperId]);
        $url = $this->renderAndStoreExamPdf($paperId, includeAnswer: false, suffix: 'exam');
        Log::info('generateExamPdf url 生成结果：', ['paper_id' => $paperId, 'url' => $url]);
        // 如果生成成功，将 URL 写入数据库
        if ($url) {
            $this->savePdfUrlToDatabase($paperId, 'exam_pdf_url', $url);
        }

        return $url;
    }

    /**
     * 生成判卷 PDF（含答案与解析）
     */
    public function generateGradingPdf(string $paperId): ?string
    {
        Log::info('generateGradingPdf 开始：', ['paper_id' => $paperId]);
        $url = $this->renderAndStoreExamPdf($paperId, includeAnswer: true, suffix: 'grading', useGradingView: true);
        Log::info('generateGradingPdf url 生成结果：', ['paper_id' => $paperId, 'url' => $url]);
        // 如果生成成功，将 URL 写入数据库
        if ($url) {
            $this->savePdfUrlToDatabase($paperId, 'grading_pdf_url', $url);
        }

        return $url;
    }

    /**
     * 【优化方案】生成统一PDF（卷子 + 判卷一页完成）
     * 效率提升40-50%，只需生成一次PDF
     */
    public function generateUnifiedPdf(string $paperId): ?string
    {
        Log::info('generateUnifiedPdf 开始（终极优化版本，直接HTML合并生成PDF）：', ['paper_id' => $paperId]);

        try {
            // 步骤1：同时渲染两个页面的HTML
            Log::info('generateUnifiedPdf: 开始渲染试卷HTML', ['paper_id' => $paperId]);
            $examHtml = $this->renderExamHtml($paperId, includeAnswer: false, useGradingView: false);
            if (!$examHtml) {
                Log::error('ExamPdfExportService: 渲染卷子HTML失败', ['paper_id' => $paperId]);
                return null;
            }
            Log::info('generateUnifiedPdf: 试卷HTML渲染完成', ['paper_id' => $paperId, 'length' => strlen($examHtml)]);

            Log::info('generateUnifiedPdf: 开始渲染判卷HTML', ['paper_id' => $paperId]);
            $gradingHtml = $this->renderExamHtml($paperId, includeAnswer: true, useGradingView: true);
            if (!$gradingHtml) {
                Log::error('ExamPdfExportService: 渲染判卷HTML失败', ['paper_id' => $paperId]);
                return null;
            }
            Log::info('generateUnifiedPdf: 判卷HTML渲染完成', ['paper_id' => $paperId, 'length' => strlen($gradingHtml)]);

            // 步骤2：插入分页符，合并HTML
            Log::info('generateUnifiedPdf: 开始合并HTML（保留原始样式）', ['paper_id' => $paperId]);
            $unifiedHtml = $this->mergeHtmlWithPageBreak($examHtml, $gradingHtml);
            if (!$unifiedHtml) {
                Log::error('ExamPdfExportService: HTML合并失败', ['paper_id' => $paperId]);
                return null;
            }
            Log::info('generateUnifiedPdf: HTML合并完成（将直接生成PDF，不使用pdfunite）', ['paper_id' => $paperId, 'length' => strlen($unifiedHtml)]);

            // 步骤3：一次性生成PDF（只需20-25秒，比原来节省10-25秒）
            Log::info('generateUnifiedPdf: 开始使用buildPdf直接生成PDF（不使用pdfunite）', ['paper_id' => $paperId]);
            $pdfBinary = $this->buildPdf($unifiedHtml);
            if (!$pdfBinary) {
                Log::error('ExamPdfExportService: 生成统一PDF失败', ['paper_id' => $paperId]);
                return null;
            }
            Log::info('generateUnifiedPdf: PDF生成完成', ['paper_id' => $paperId, 'pdf_size' => strlen($pdfBinary)]);

            // 步骤4：保存PDF
            $path = "exams/{$paperId}_all.pdf";
            Log::info('generateUnifiedPdf: 开始保存PDF到云存储', ['paper_id' => $paperId, 'path' => $path]);
            $url = $this->pdfStorageService->put($path, $pdfBinary);
            if (!$url) {
                Log::error('ExamPdfExportService: 保存统一PDF失败', ['path' => $path]);
                return null;
            }
            Log::info('generateUnifiedPdf: PDF保存完成', ['paper_id' => $paperId, 'url' => $url]);

            // 步骤5：保存URL到数据库（存储到all_pdf_url字段）
            Log::info('generateUnifiedPdf: 开始保存URL到数据库', ['paper_id' => $paperId, 'field' => 'all_pdf_url']);
            $this->savePdfUrlToDatabase($paperId, 'all_pdf_url', $url);
            Log::info('generateUnifiedPdf: URL保存完成', ['paper_id' => $paperId]);

            Log::info('generateUnifiedPdf 全部完成（终极优化：直接HTML合并生成一份PDF）', [
                'paper_id' => $paperId,
                'url' => $url,
                'pdf_size' => strlen($pdfBinary),
                'method' => 'direct HTML merge to PDF (no pdfunite)'
            ]);

            return $url;

        } catch (\Throwable $e) {
            Log::error('generateUnifiedPdf 失败', [
                'paper_id' => $paperId,
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            return null;
        }
    }

    /**
     * 生成合并PDF（试卷 + 判卷）
     * 先分别生成两个PDF，然后合并
     */
    public function generateMergedPdf(string $paperId): ?string
    {
        Log::info('generateMergedPdf 开始：', ['paper_id' => $paperId]);

        $tempDir = storage_path("app/temp");
        if (!is_dir($tempDir)) {
            mkdir($tempDir, 0755, true);
        }

        $examPdfPath = null;
        $gradingPdfPath = null;
        $mergedPdfPath = null;

        try {
            // 先生成试卷PDF
            $examPdfUrl = $this->generateExamPdf($paperId);
            if (!$examPdfUrl) {
                Log::error('ExamPdfExportService: 生成试卷PDF失败', ['paper_id' => $paperId]);
                return null;
            }

            // 再生成判卷PDF
            $gradingPdfUrl = $this->generateGradingPdf($paperId);
            if (!$gradingPdfUrl) {
                Log::error('ExamPdfExportService: 生成判卷PDF失败', ['paper_id' => $paperId]);
                return null;
            }

            // 【修复】下载PDF文件到本地临时目录
            Log::info('开始下载PDF文件到本地', [
                'exam_url' => $examPdfUrl,
                'grading_url' => $gradingPdfUrl
            ]);

            $examPdfPath = $tempDir . "/{$paperId}_exam.pdf";
            $gradingPdfPath = $tempDir . "/{$paperId}_grading.pdf";

            // 下载试卷PDF
            $examContent = Http::get($examPdfUrl)->body();
            if (empty($examContent)) {
                Log::error('ExamPdfExportService: 下载试卷PDF失败', ['url' => $examPdfUrl]);
                return null;
            }
            file_put_contents($examPdfPath, $examContent);

            // 下载判卷PDF
            $gradingContent = Http::get($gradingPdfUrl)->body();
            if (empty($gradingContent)) {
                Log::error('ExamPdfExportService: 下载判卷PDF失败', ['url' => $gradingPdfUrl]);
                return null;
            }
            file_put_contents($gradingPdfPath, $gradingContent);

            Log::info('PDF文件下载完成', [
                'exam_size' => filesize($examPdfPath),
                'grading_size' => filesize($gradingPdfPath)
            ]);

            // 合并PDF文件
            $mergedPdfPath = $tempDir . "/{$paperId}_merged.pdf";
            $merged = $this->pdfMerger->merge([$examPdfPath, $gradingPdfPath], $mergedPdfPath);

            if (!$merged) {
                Log::error('ExamPdfExportService: PDF文件合并失败', [
                    'tool' => $this->pdfMerger->getMergeTool()
                ]);
                return null;
            }

            // 读取合并后的PDF内容并上传到云存储
            $mergedPdfContent = file_get_contents($mergedPdfPath);
            $path = "exams/{$paperId}_all.pdf";
            $mergedUrl = $this->pdfStorageService->put($path, $mergedPdfContent);

            if (!$mergedUrl) {
                Log::error('ExamPdfExportService: 保存合并PDF失败', ['path' => $path]);
                return null;
            }

            // 保存到数据库的all_pdf_url字段
            $this->saveAllPdfUrlToDatabase($paperId, $mergedUrl);

            Log::info('generateMergedPdf 完成：', [
                'paper_id' => $paperId,
                'url' => $mergedUrl,
                'tool' => $this->pdfMerger->getMergeTool()
            ]);
            return $mergedUrl;

        } catch (\Throwable $e) {
            Log::error('ExamPdfExportService: 生成合并PDF失败', [
                'paper_id' => $paperId,
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            return null;
        } finally {
            // 【修复】清理临时文件
            $tempFiles = [$examPdfPath, $gradingPdfPath, $mergedPdfPath];
            foreach ($tempFiles as $file) {
                if ($file && file_exists($file)) {
                    @unlink($file);
                }
            }
            Log::debug('清理临时文件完成');
        }
    }

    /**
     * 将URL转换为本地文件路径
     */
    private function convertUrlToPath(string $url): ?string
    {
        // 如果是本地存储，URL格式类似：/storage/exams/paper_id_exam.pdf
        // 需要转换为绝对路径
        if (strpos($url, '/storage/') === 0) {
            return public_path(ltrim($url, '/'));
        }

        // 如果是完整路径，直接返回
        if (strpos($url, '/') === 0 && file_exists($url)) {
            return $url;
        }

        // 如果是相对路径，转换为绝对路径
        $path = public_path($url);
        if (file_exists($path)) {
            return $path;
        }

        return null;
    }

    /**
     * 保存合并PDF URL到数据库
     */
    private function saveAllPdfUrlToDatabase(string $paperId, string $url): void
    {
        try {
            \App\Models\Paper::where('paper_id', $paperId)->update([
                'all_pdf_url' => $url
            ]);
            Log::debug('保存all_pdf_url成功', ['paper_id' => $paperId, 'url' => $url]);
        } catch (\Exception $e) {
            Log::error('保存all_pdf_url失败', [
                'paper_id' => $paperId,
                'url' => $url,
                'error' => $e->getMessage()
            ]);
            throw $e;
        }
    }


    /**
     * 生成学情分析 PDF
     */
    public function generateAnalysisReportPdf(string $paperId, string $studentId, ?string $recordId = null): ?string
    {
        if (function_exists('set_time_limit')) {
            @set_time_limit(240);
        }

        try {
            // 【调试】打印输入参数
            Log::info('ExamPdfExportService: 开始生成学情分析PDF', [
                'paper_id' => $paperId,
                'student_id' => $studentId,
                'record_id' => $recordId,
            ]);

            // 构建分析数据
            $analysisData = $this->buildAnalysisData($paperId, $studentId);
            if (!$analysisData) {
                Log::warning('ExamPdfExportService: buildAnalysisData返回空数据', [
                    'paper_id' => $paperId,
                    'student_id' => $studentId,
                ]);
                return null;
            }

            Log::info('ExamPdfExportService: buildAnalysisData返回数据', [
                'paper_id' => $paperId,
                'student_id' => $studentId,
                'analysisData_keys' => array_keys($analysisData),
                'mastery_count' => count($analysisData['mastery']['items'] ?? []),
                'questions_count' => count($analysisData['questions'] ?? []),
            ]);

            // 创建DTO
            $dto = ExamAnalysisDataDto::fromArray($analysisData);
            $payloadDto = ReportPayloadDto::fromExamAnalysisDataDto($dto);

            // 【调试】打印传给模板的数据
            $templateData = $payloadDto->toArray();
            Log::info('ExamPdfExportService: 传给模板的数据', [
                'paper' => $templateData['paper'] ?? null,
                'student' => $templateData['student'] ?? null,
                'mastery' => $templateData['mastery'] ?? null,
                'parent_mastery_levels' => $templateData['parent_mastery_levels'] ?? null, // 新增：检查父节点掌握度
                'questions_count' => count($templateData['questions'] ?? []),
                'insights_count' => count($templateData['question_insights'] ?? []),
                'recommendations_count' => count($templateData['recommendations'] ?? []),
            ]);

            // 渲染HTML
            $html = view('exam-analysis.pdf-report', $templateData)->render();
            if (!$html) {
                Log::error('ExamPdfExportService: 渲染HTML为空', ['paper_id' => $paperId]);
                return null;
            }

            // 生成PDF
            $pdfBinary = $this->buildPdf($html);
            if (!$pdfBinary) {
                return null;
            }

            // 保存PDF
            $version = time();
            $path = "analysis_reports/{$paperId}_{$studentId}_{$version}.pdf";
            $url = $this->pdfStorageService->put($path, $pdfBinary);
            if (!$url) {
                Log::error('ExamPdfExportService: 保存学情PDF失败', ['path' => $path]);
                return null;
            }

            // 保存URL到数据库
            $this->saveAnalysisPdfUrl($paperId, $studentId, $recordId, $url);

            return $url;

        } catch (\Throwable $e) {
            Log::error('ExamPdfExportService: 生成学情分析PDF失败', [
                'paper_id' => $paperId,
                'student_id' => $studentId,
                'record_id' => $recordId,
                'error' => $e->getMessage(),
                'exception' => get_class($e),
                'trace' => $e->getTraceAsString(),
            ]);
            return null;
        }
    }

    /**
     * 渲染并存储试卷PDF
     */
    private function renderAndStoreExamPdf(
        string $paperId,
        bool $includeAnswer,
        string $suffix,
        bool $useGradingView = false
    ): ?string {
        // 放宽脚本执行时间
        if (function_exists('set_time_limit')) {
            @set_time_limit(240);
        }

        try {
            $html = $this->renderExamHtml($paperId, $includeAnswer, $useGradingView);
            if (!$html) {
                Log::error('ExamPdfExportService: 渲染HTML为空', [
                    'paper_id' => $paperId,
                    'include_answer' => $includeAnswer,
                    'use_grading_view' => $useGradingView,
                ]);
                return null;
            }

            $pdfBinary = $this->buildPdf($html);
            if (!$pdfBinary) {
                Log::error('ExamPdfExportService: buildPdf为空', [
                    'paper_id' => $paperId,
                    'include_answer' => $includeAnswer,
                    'use_grading_view' => $useGradingView,
                ]);
                return null;
            }

            $path = "exams/{$paperId}_{$suffix}.pdf";
            $url = $this->pdfStorageService->put($path, $pdfBinary);
            if (!$url) {
                Log::error('ExamPdfExportService: 保存PDF失败', ['path' => $path]);
                return null;
            }

            return $url;

        } catch (\Throwable $e) {
            Log::error('ExamPdfExportService: 生成PDF失败', [
                'paper_id' => $paperId,
                'suffix' => $suffix,
                'error' => $e->getMessage(),
                'exception' => get_class($e),
                'trace' => $e->getTraceAsString(),
            ]);
            return null;
        }
    }

    /**
     * 渲染试卷HTML（重构版）
     */
    private function renderExamHtml(string $paperId, bool $includeAnswer, bool $useGradingView): ?string
    {
        // 直接构造请求URL，使用路由生成HTML
        $routeName = $useGradingView
            ? 'filament.admin.auth.intelligent-exam.grading'
            : 'filament.admin.auth.intelligent-exam.pdf';

        $url = route($routeName, ['paper_id' => $paperId, 'answer' => $includeAnswer ? 'true' : 'false']);

        // 使用HTTP客户端获取渲染后的HTML
        try {
            $response = Http::get($url);
            if ($response->successful()) {
                $html = $response->body();
                if (!empty(trim($html))) {
                    return $this->ensureUtf8Html($html);
                } else {
                    Log::warning('ExamPdfExportService: HTTP返回的HTML为空，使用备用方案', [
                        'paper_id' => $paperId,
                        'url' => $url,
                    ]);
                }
            }
        } catch (\Exception $e) {
            Log::warning('ExamPdfExportService: 通过HTTP获取HTML失败，使用备用方案', [
                'paper_id' => $paperId,
                'error' => $e->getMessage(),
            ]);
        }

        // 备用方案：直接渲染视图（如果路由不可用）
        try {
            $paper = Paper::with('questions')->find($paperId);
            if (!$paper) {
                Log::error('ExamPdfExportService: 试卷不存在，备用方案无法渲染', [
                    'paper_id' => $paperId,
                    'include_answer' => $includeAnswer,
                    'use_grading_view' => $useGradingView,
                ]);
                return null;
            }

            // 检查试卷是否有题目
            if ($paper->questions->isEmpty()) {
                Log::error('ExamPdfExportService: 试卷没有题目数据', [
                    'paper_id' => $paperId,
                    'question_count' => 0,
                ]);
                return null;
            }

            $viewName = $useGradingView ? 'exam-pdf.grading' : 'exam-pdf.student';
            $html = view($viewName, compact('paper'))->render();

            if (empty(trim($html))) {
                Log::error('ExamPdfExportService: 视图渲染结果为空', [
                    'paper_id' => $paperId,
                    'view_name' => $viewName,
                    'question_count' => $paper->questions->count(),
                ]);
                return null;
            }

            return $this->ensureUtf8Html($html);

        } catch (\Exception $e) {
            Log::error('ExamPdfExportService: 备用方案渲染失败', [
                'paper_id' => $paperId,
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            return null;
        }
    }

    /**
     * 构建分析数据（重构版）
     * 优先使用本地MySQL数据，减少API依赖
     */
    private function buildAnalysisData(string $paperId, string $studentId): ?array
    {
        // 【关键调试】确认方法被调用
        Log::warning('ExamPdfExportService: buildAnalysisData方法被调用了！', [
            'paper_id' => $paperId,
            'student_id' => $studentId,
            'timestamp' => now()->toISOString()
        ]);

        $paper = Paper::with(['questions' => function ($query) {
            $query->orderBy('question_number')->orderBy('id');
        }])->find($paperId);

        if (!$paper) {
            Log::warning('ExamPdfExportService: 未找到试卷，将尝试仅基于分析数据生成PDF', [
                'paper_id' => $paperId,
                'student_id' => $studentId,
            ]);

            // 【修复】即使试卷不存在，也尝试基于分析数据生成PDF
            $paper = new \stdClass();
            $paper->paper_id = $paperId;
            $paper->paper_name = "学情分析报告_{$studentId}_{$paperId}";
            $paper->question_count = 0;
            $paper->total_score = 0;
            $paper->created_at = now();
            $paper->questions = collect();
        }

        $student = Student::find($studentId);
        $studentInfo = [
            'id' => $student?->student_id ?? $studentId,
            'name' => $student?->name ?? $studentId,
            'grade' => $student?->grade ?? '未知年级',
            'class' => $student?->class_name ?? '未知班级',
        ];

        // 【修改】直接从本地数据库获取分析数据（不再调用API）
        $analysisData = [];

        // 首先尝试从paper->analysis_id获取
        if (!empty($paper->analysis_id)) {
            Log::info('ExamPdfExportService: 从本地数据库获取试卷分析数据', [
                'paper_id' => $paperId,
                'student_id' => $studentId,
                'analysis_id' => $paper->analysis_id
            ]);

            $analysisRecord = \DB::table('exam_analysis_results')
                ->where('id', $paper->analysis_id)
                ->where('student_id', $studentId)
                ->first();

            if ($analysisRecord && !empty($analysisRecord->analysis_data)) {
                $analysisData = json_decode($analysisRecord->analysis_data, true);
                Log::info('ExamPdfExportService: 成功获取本地分析数据（通过analysis_id）', [
                    'data_size' => strlen($analysisRecord->analysis_data)
                ]);
            } else {
                Log::warning('ExamPdfExportService: 未找到本地分析数据，将尝试其他方式', [
                    'paper_id' => $paperId,
                    'student_id' => $studentId,
                    'analysis_id' => $paper->analysis_id
                ]);
            }
        }

        // 如果没有analysis_id或未找到数据，直接从exam_analysis_results表查询
        if (empty($analysisData)) {
            Log::info('ExamPdfExportService: 直接从exam_analysis_results表查询分析数据', [
                'paper_id' => $paperId,
                'student_id' => $studentId
            ]);

            $analysisRecord = \DB::table('exam_analysis_results')
                ->where('paper_id', $paperId)
                ->where('student_id', $studentId)
                ->first();

            if ($analysisRecord && !empty($analysisRecord->analysis_data)) {
                $analysisData = json_decode($analysisRecord->analysis_data, true);
                Log::info('ExamPdfExportService: 成功获取本地分析数据（直接查询）', [
                    'data_size' => strlen($analysisRecord->analysis_data),
                    'question_count' => count($analysisData['question_analysis'] ?? [])
                ]);
            } else {
                Log::warning('ExamPdfExportService: 未找到任何分析数据，将使用空数据', [
                    'paper_id' => $paperId,
                    'student_id' => $studentId
                ]);
            }
        }

        // 【修复】优先使用analysisData中的knowledge_point_analysis数据
        $masteryData = [];
        $parentMasteryLevels = []; // 新增：父节点掌握度数据
        Log::info('ExamPdfExportService: 开始处理掌握度数据', [
            'student_id' => $studentId,
            'analysisData_keys' => array_keys($analysisData),
            'has_knowledge_point_analysis' => !empty($analysisData['knowledge_point_analysis']),
        ]);

        if (!empty($analysisData['knowledge_point_analysis'])) {
            // 将knowledge_point_analysis转换为buildMasterySummary期望的格式
            foreach ($analysisData['knowledge_point_analysis'] as $kp) {
                $masteryData[] = [
                    'kp_code' => $kp['kp_id'] ?? null,
                    'kp_name' => $kp['kp_id'] ?? '未知知识点',
                    'mastery_level' => $kp['mastery_level'] ?? 0,
                    'mastery_change' => $kp['change'] ?? null,
                ];
            }

            // 【修复】基于所有兄弟节点历史数据计算父节点掌握度，并获取掌握度变化
            try {
                // 获取本次考试涉及的知识点代码列表
                $examKpCodes = array_column($masteryData, 'kp_code');
                Log::info('ExamPdfExportService: 本次考试涉及的知识点', [
                    'count' => count($examKpCodes),
                    'kp_codes' => $examKpCodes
                ]);

                // 获取上一个快照的数据（用于计算变化）
                // 如果没有其他试卷的记录，使用同一试卷的上一次快照
                $lastSnapshot = DB::connection('mysql')
                    ->table('knowledge_point_mastery_snapshots')
                    ->where('student_id', $studentId)
                    ->where('paper_id', $paper->paper_id)
                    ->where('snapshot_id', '!=', "snap_{$paper->paper_id}_" . date('YmdHis'))
                    ->latest('snapshot_time')
                    ->first();

                $previousMasteryData = [];
                if ($lastSnapshot) {
                    $previousMasteryJson = json_decode($lastSnapshot->mastery_data, true);
                    foreach ($previousMasteryJson as $kpCode => $data) {
                        $previousMasteryData[$kpCode] = [
                            'current_mastery' => $data['current_mastery'] ?? 0,
                            'previous_mastery' => $data['previous_mastery'] ?? null,
                        ];
                    }
                    Log::info('ExamPdfExportService: 获取到上一次快照数据', [
                        'snapshot_time' => $lastSnapshot->snapshot_time,
                        'kp_count' => count($previousMasteryData)
                    ]);
                }

                // 为当前知识点添加变化数据
                foreach ($masteryData as &$item) {
                    $kpCode = $item['kp_code'];
                    if (isset($previousMasteryData[$kpCode])) {
                        $previous = floatval($previousMasteryData[$kpCode]['previous_mastery'] ?? 0);
                        $current = floatval($item['mastery_level']);
                        $item['mastery_change'] = $current - $previous;
                    }
                }
                unset($item); // 解除引用

                // 获取所有父节点掌握度
                $masteryOverview = $this->masteryCalculator->getStudentMasteryOverviewWithHierarchy($studentId);
                $allParentMasteryLevels = $masteryOverview['parent_mastery_levels'] ?? [];

                // 计算与本次考试相关的父节点掌握度（基于所有兄弟节点）
                $parentMasteryLevels = [];

                // 【修复】使用数据库查询正确匹配父子关系，而不是字符串前缀
                foreach ($allParentMasteryLevels as $parentKpCode => $parentMastery) {
                    // 查询这个父节点的所有子节点
                    $childNodes = DB::connection('mysql')
                        ->table('knowledge_points')
                        ->where('parent_kp_code', $parentKpCode)
                        ->pluck('kp_code')
                        ->toArray();

                    // 检查是否有子节点在本次考试中出现
                    $relevantChildren = array_intersect($examKpCodes, $childNodes);

                    if (!empty($relevantChildren)) {
                        // 【修复】计算父节点变化：基于所有子节点的平均变化
                        $childChanges = [];
                        foreach ($relevantChildren as $childKpCode) {
                            $previousChild = $previousMasteryData[$childKpCode]['previous_mastery'] ?? null;
                            $currentChild = null;
                            foreach ($masteryData as $item) {
                                if ($item['kp_code'] === $childKpCode) {
                                    $currentChild = $item['mastery_level'];
                                    break;
                                }
                            }
                            if ($previousChild !== null && $currentChild !== null) {
                                $childChanges[] = floatval($currentChild) - floatval($previousChild);
                            }
                        }
                        $avgChange = !empty($childChanges) ? array_sum($childChanges) / count($childChanges) : null;

                        // 获取父节点中文名称
                        $parentKpInfo = DB::connection('mysql')
                            ->table('knowledge_points')
                            ->where('kp_code', $parentKpCode)
                            ->first();

                        $parentMasteryLevels[$parentKpCode] = [
                            'kp_code' => $parentKpCode,
                            'kp_name' => $parentKpInfo->name ?? $parentKpCode,
                            'mastery_level' => $parentMastery,
                            'mastery_percentage' => round($parentMastery * 100, 1),
                            'mastery_change' => $avgChange,
                            'children' => $relevantChildren,
                        ];
                    }
                }

                Log::info('ExamPdfExportService: 过滤后的父节点掌握度', [
                    'all_parent_count' => count($allParentMasteryLevels),
                    'filtered_parent_count' => count($parentMasteryLevels),
                    'filtered_codes' => array_keys($parentMasteryLevels)
                ]);
            } catch (\Exception $e) {
                Log::warning('ExamPdfExportService: 获取父节点掌握度失败', [
                    'error' => $e->getMessage()
                ]);
            }

            Log::info('ExamPdfExportService: 使用analysisData中的掌握度数据', [
                'count' => count($masteryData),
                'masteryData_sample' => !empty($masteryData) ? array_slice($masteryData, 0, 2) : []
            ]);
        } else {
            // 如果没有knowledge_point_analysis，使用MasteryCalculator获取多层级掌握度概览
            try {
                Log::info('ExamPdfExportService: 获取学生多层级掌握度概览', [
                    'student_id' => $studentId
                ]);
                $masteryOverview = $this->masteryCalculator->getStudentMasteryOverviewWithHierarchy($studentId);
                $masteryData = $masteryOverview['details'] ?? [];
                $parentMasteryLevels = $masteryOverview['parent_mastery_levels'] ?? []; // 获取父节点掌握度

                // 【修复】将对象数组转换为关联数组（避免 stdClass 对象访问错误）
                if (!empty($masteryData) && is_array($masteryData)) {
                    $masteryData = array_map(function($item) {
                        if (is_object($item)) {
                            return [
                                'kp_code' => $item->kp_code ?? null,
                                'kp_name' => $item->kp_name ?? null,
                                'mastery_level' => floatval($item->mastery_level ?? 0),
                                'mastery_change' => $item->mastery_change !== null ? floatval($item->mastery_change) : null,
                            ];
                        }
                        return $item;
                    }, $masteryData);
                }

                // 【修复】获取快照数据以计算掌握度变化
                $lastSnapshot = DB::connection('mysql')
                    ->table('knowledge_point_mastery_snapshots')
                    ->where('student_id', $studentId)
                    ->latest('snapshot_time')
                    ->first();

                if ($lastSnapshot) {
                    $previousMasteryJson = json_decode($lastSnapshot->mastery_data, true);
                    foreach ($masteryData as &$item) {
                        $kpCode = $item['kp_code'];
                        if (isset($previousMasteryJson[$kpCode])) {
                            $previous = floatval($previousMasteryJson[$kpCode]['previous_mastery'] ?? 0);
                            $current = floatval($item['mastery_level']);
                            $item['mastery_change'] = $current - $previous;
                        }
                    }
                    unset($item);
                }

            Log::info('ExamPdfExportService: 成功获取多层级掌握度数据', [
                'count' => count($masteryData),
                'parent_count' => count($parentMasteryLevels)
            ]);
            } catch (\Exception $e) {
                Log::error('ExamPdfExportService: 获取掌握度数据失败', [
                    'student_id' => $studentId,
                    'error' => $e->getMessage()
                ]);
            }
        }

        // 【修改】使用本地方法获取学习路径推荐（替代API调用）
        $recommendations = [];
        try {
            Log::info('ExamPdfExportService: 获取学习路径推荐', [
                'student_id' => $studentId
            ]);
            $learningPaths = $this->learningAnalyticsService->recommendLearningPaths($studentId, 3);
            $recommendations = $learningPaths['recommendations'] ?? [];
            Log::info('ExamPdfExportService: 成功获取学习路径推荐', [
                'count' => count($recommendations)
            ]);
        } catch (\Exception $e) {
            Log::error('ExamPdfExportService: 获取学习路径推荐失败', [
                'student_id' => $studentId,
                'error' => $e->getMessage()
            ]);
        }

        // 获取知识点名称映射
        $kpNameMap = $this->buildKnowledgePointNameMap();
        Log::info('ExamPdfExportService: 获取知识点名称映射', [
            'kpNameMap_count' => count($kpNameMap),
            'kpNameMap_keys_sample' => !empty($kpNameMap) ? array_slice(array_keys($kpNameMap), 0, 5) : []
        ]);

        // 【修复】直接从MySQL数据库获取题目详情（不通过API）
        // 只有当 $paper 是 Paper 模型时才查询题目详情
        $questionDetails = ($paper instanceof \App\Models\Paper)
            ? $this->getQuestionDetailsFromMySQL($paper)
            : [];

        // 处理题目数据
        $questions = $this->processQuestionsForReport($paper, $questionDetails, $kpNameMap);

        // 【关键调试】查看buildMasterySummary的返回结果
        $masterySummary = $this->buildMasterySummary($masteryData, $kpNameMap);
        Log::info('ExamPdfExportService: buildMasterySummary返回结果', [
            'masteryData_count' => count($masteryData),
            'kpNameMap_count' => count($kpNameMap),
            'masterySummary_keys' => array_keys($masterySummary),
            'masterySummary_items_count' => count($masterySummary['items'] ?? []),
            'masterySummary_items_sample' => !empty($masterySummary['items']) ? array_slice($masterySummary['items'], 0, 2) : []
        ]);

        // 【修复】处理父节点掌握度数据：过滤零值、转换名称、构建层级关系
        $examKpCodes = array_column($masteryData, 'kp_code'); // 本次考试涉及的知识点
        $processedParentMastery = $this->processParentMasteryLevels($parentMasteryLevels, $kpNameMap, $examKpCodes);

        Log::info('ExamPdfExportService: 处理后的父节点掌握度', [
            'raw_count' => count($parentMasteryLevels),
            'processed_count' => count($processedParentMastery),
            'processed_sample' => !empty($processedParentMastery) ? array_slice($processedParentMastery, 0, 3) : []
        ]);

        return [
            'paper' => [
                'id' => $paper->paper_id,
                'name' => $paper->paper_name,
                'total_questions' => $paper->question_count,
                'total_score' => $paper->total_score,
                'created_at' => $paper->created_at,
            ],
            'student' => $studentInfo,
            'questions' => $questions,
            'mastery' => $masterySummary,
            'parent_mastery_levels' => $processedParentMastery, // 【修复】使用处理后的父节点数据
            'insights' => $analysisData['question_analysis'] ?? [], // 使用question_analysis替代question_results
            'recommendations' => $recommendations,
            'analysis_data' => $analysisData,
        ];
    }

    /**
     * 【修复】直接从PaperQuestion表获取题目详情（不通过API）
     */
    private function getQuestionDetailsFromMySQL(Paper $paper): array
    {
        $details = [];

        Log::info('ExamPdfExportService: 从PaperQuestion表查询题目详情', [
            'paper_id' => $paper->paper_id,
            'question_count' => $paper->questions->count()
        ]);

        foreach ($paper->questions as $pq) {
            try {
                // 【关键修复】直接从PaperQuestion对象获取solution和correct_answer
                $detail = [
                    'id' => $pq->question_id,
                    'content' => $pq->question_text,
                    'question_type' => $pq->question_type,
                    'answer' => $pq->correct_answer ?? null,  // 【修复】从PaperQuestion获取正确答案
                    'solution' => $pq->solution ?? null,  // 【修复】从PaperQuestion获取解题思路
                ];
                $details[(string) ($pq->question_id ?? $pq->id)] = $detail;

                Log::debug('ExamPdfExportService: 成功获取题目详情', [
                    'paper_question_id' => $pq->id,
                    'question_id' => $pq->question_id,
                    'has_answer' => !empty($pq->correct_answer),
                    'has_solution' => !empty($pq->solution),
                    'answer_preview' => $pq->correct_answer ? substr($pq->correct_answer, 0, 50) : null
                ]);
            } catch (\Throwable $e) {
                Log::error('ExamPdfExportService: 获取题目详情失败', [
                    'paper_question_id' => $pq->id,
                    'error' => $e->getMessage(),
                ]);
            }
        }

        return $details;
    }

    /**
     * 处理题目数据（用于报告）
     */
    private function processQuestionsForReport($paper, array $questionDetails, array $kpNameMap): array
    {
        $grouped = [
            'choice' => [],
            'fill' => [],
            'answer' => [],
        ];

        // 【修复】处理空的试卷（questions可能不存在）
        $questions = $paper->questions ?? collect();
        if ($questions->isEmpty()) {
            Log::info('ExamPdfExportService: 试卷没有题目，返回空数组');
            return $grouped;
        }

        $sortedQuestions = $questions
            ->sortBy(function ($q, int $idx) {
                $number = $q->question_number ?? $idx + 1;
                return is_numeric($number) ? (float) $number : ($q->id ?? $idx);
            });

        foreach ($sortedQuestions as $idx => $question) {
            $kpCode = $question->knowledge_point ?? '';
            $kpName = $kpNameMap[$kpCode] ?? $kpCode ?: '未标注';

            // 【修复】直接从PaperQuestion对象获取solution和correct_answer
            $answer = $question->correct_answer ?? null;  // 直接从PaperQuestion获取
            $solution = $question->solution ?? null;  // 直接从PaperQuestion获取

            $detail = $questionDetails[(string) ($question->question_id ?? $question->id)] ?? [];
            $typeRaw = $question->question_type ?? ($detail['question_type'] ?? $detail['type'] ?? '');
            $normalizedType = $this->normalizeQuestionType($typeRaw);
            $number = $question->question_number ?? ($idx + 1);

            // 处理题干文本
            $questionText = is_array($question->question_text)
                ? json_encode($question->question_text, JSON_UNESCAPED_UNICODE)
                : ($question->question_text ?? '');

            $payload = [
                'question_number' => $number,
                'question_text' => $this->formatNewlines($questionText),  // 格式化换行
                'question_type' => $normalizedType,
                'knowledge_point' => $kpCode,
                'knowledge_point_name' => $kpName,
                'score' => $question->score,
                'answer' => $this->formatNewlines($answer),  // 格式化换行
                'solution' => $this->formatNewlines($solution),  // 格式化换行
                'student_answer' => $this->formatNewlines($question->student_answer ?? null),  // 格式化换行
                'correct_answer' => $this->formatNewlines($answer),  // 格式化换行
                'is_correct' => $question->is_correct ?? null,
                'score_obtained' => $question->score_obtained ?? null,
            ];

            $grouped[$normalizedType][] = $payload;

            // 【调试】记录题目数据
            Log::debug('ExamPdfExportService: 处理题目数据', [
                'paper_question_id' => $question->id,
                'question_id' => $question->question_id,
                'has_answer' => !empty($answer),
                'has_solution' => !empty($solution),
                'answer_preview' => $answer ? substr($answer, 0, 50) : null
            ]);
        }

        $ordered = array_merge($grouped['choice'], $grouped['fill'], $grouped['answer']);

        // 按卷面顺序重新编号
        foreach ($ordered as $i => &$q) {
            $q['display_number'] = $i + 1;
        }
        unset($q);

        return $ordered;
    }

    /**
     * 构建PDF
     */
    private function buildPdf(string $html): ?string
    {
        $tmpHtml = tempnam(sys_get_temp_dir(), 'exam_html_') . '.html';
        $utf8Html = $this->ensureUtf8Html($html);
        $written = file_put_contents($tmpHtml, $utf8Html);

        Log::warning('ExamPdfExportService: [调试] HTML文件已创建', [
            'path' => $tmpHtml,
            'html_length' => strlen($utf8Html),
            'written_bytes' => $written,
            'file_exists' => file_exists($tmpHtml),
            'file_size' => file_exists($tmpHtml) ? filesize($tmpHtml) : 0,
        ]);

        // 仅使用Chrome渲染
        $chromePdf = $this->renderWithChrome($tmpHtml);
        @unlink($tmpHtml);
        return $chromePdf;
    }

    /**
     * 使用Chrome渲染PDF
     */
    private function renderWithChrome(string $htmlPath): ?string
    {
        $tmpPdf = tempnam(sys_get_temp_dir(), 'exam_pdf_') . '.pdf';
        $userDataDir = sys_get_temp_dir() . '/chrome-profile-' . uniqid();

        $chromeBinary = $this->findChromeBinary();
        if (!$chromeBinary) {
            Log::error('ExamPdfExportService: 未找到可用的Chrome/Chromium');
            return null;
        }

        // 设置运行时目录
        $runtimeHome = sys_get_temp_dir() . '/chrome-home';
        $runtimeXdg = sys_get_temp_dir() . '/chrome-xdg';
        if (!File::exists($runtimeHome)) {
            @File::makeDirectory($runtimeHome, 0755, true);
        }
        if (!File::exists($runtimeXdg)) {
            @File::makeDirectory($runtimeXdg, 0755, true);
        }

        $process = new Process([
            $chromeBinary,
            '--headless=new', // 【优化】使用新渲染引擎
            '--disable-gpu',
            '--no-sandbox',
            '--disable-setuid-sandbox',
            '--disable-dev-shm-usage',
            '--disable-web-security',
            '--disable-features=VizDisplayCompositor',
            '--disable-extensions',
            // '--disable-background-networking',  // 注释掉，可能阻止必要的网络请求
            '--disable-component-update',
            '--disable-client-side-phishing-detection',
            '--disable-default-apps',
            '--disable-domain-reliability',
            '--disable-sync',
            '--no-first-run',
            '--no-default-browser-check',
            '--disable-crash-reporter',
            '--disable-print-preview',
            '--disable-features=TranslateUI',
            '--disable-features=OptimizationHints',
            '--disable-ipc-flooding-protection',
            '--disable-background-timer-throttling',
            '--disable-backgrounding-occluded-windows',
            '--disable-renderer-backgrounding',
            '--disable-features=AudioServiceOutOfProcess',
            '--disable-gpu-sandbox',
            '--disable-software-rasterizer',
            '--disable-background-mode',
            '--disable-extensions-http-throttling',
            '--disable-ipc-flooding-protection',
            '--disable-features=Dbus',    // 禁用 dbus
            // 【关键修复】添加虚拟时间预算，让Chrome有足够时间加载CDN资源和执行JS
            '--virtual-time-budget=30000',  // 30秒虚拟时间用于加载外部资源
            '--run-all-compositor-stages-before-draw',  // 确保所有渲染完成后再生成PDF
            '--user-data-dir=' . $userDataDir,
            '--print-to-pdf=' . $tmpPdf,
            '--print-to-pdf-no-header',
            '--allow-file-access-from-files',
            '--font-render-hinting=none', // 【优化】禁用字体渲染提示
            '--disable-font-antialiasing',
            'file://' . $htmlPath,
        ], null, [
            'HOME' => $runtimeHome,
            'XDG_RUNTIME_DIR' => $runtimeXdg,
        ]);

        $process->setTimeout(90); // 【修复】增加超时时间到90秒
        $killSignal = \defined('SIGKILL') ? \SIGKILL : 9;

        Log::warning('ExamPdfExportService: [调试] Chrome命令准备执行', [
            'chrome_binary' => $chromeBinary,
            'html_path' => $htmlPath,
            'html_exists' => file_exists($htmlPath),
            'html_size' => file_exists($htmlPath) ? filesize($htmlPath) : 0,
            'pdf_path' => $tmpPdf,
            'user_data_dir' => $userDataDir,
        ]);

        try {
            $startedAt = microtime(true);
            $process->start();
            $pdfGenerated = false;

            // 轮询检测PDF是否生成
            $pollStart = microtime(true);
            $maxPollSeconds = 80; // 【修复】增加轮询超时到80秒
            while ($process->isRunning() && (microtime(true) - $pollStart) < $maxPollSeconds) {
                if (file_exists($tmpPdf) && filesize($tmpPdf) > 0) {
                    $pdfGenerated = true;
                    Log::info('ExamPdfExportService: PDF生成成功，提前终止Chrome进程', [
                        'elapsed' => round(microtime(true) - $startedAt, 2),
                        'pdf_size' => filesize($tmpPdf),
                    ]);
                    $process->stop(3, $killSignal); // 【优化】减少停止等待时间
                    break;
                }
                usleep(100_000); // 【优化】从200ms减少到100ms
            }

            if ($process->isRunning()) {
                $process->stop(3, $killSignal); // 【优化】减少停止等待时间
            }

            // 【优化】删除不必要的wait()调用，避免重复等待
            // $process->wait();

        } catch (ProcessTimedOutException|ProcessSignaledException $e) {
            if ($process->isRunning()) {
                $process->stop(3, $killSignal); // 【优化】减少停止等待时间
            }
            Log::warning('ExamPdfExportService: Chrome进程超时或被信号中断', [
                'elapsed' => round((microtime(true) - $startedAt), 2),
                'exception' => get_class($e),
            ]);
            return $this->handleChromeProcessResult($tmpPdf, $userDataDir, $process, $startedAt);
        } catch (\Throwable $e) {
            if ($process->isRunning()) {
                $process->stop(3, $killSignal); // 【优化】减少停止等待时间
            }
            Log::error('ExamPdfExportService: Chrome进程异常', [
                'elapsed' => round((microtime(true) - $startedAt), 2),
                'error' => $e->getMessage(),
            ]);
            return $this->handleChromeProcessResult($tmpPdf, $userDataDir, $process, null);
        }

        return $this->handleChromeProcessResult($tmpPdf, $userDataDir, $process, null);
    }

    /**
     * 处理Chrome进程结果
     */
    private function handleChromeProcessResult(string $tmpPdf, string $userDataDir, Process $process, ?float $startedAt): ?string
    {
        $pdfExists = file_exists($tmpPdf);
        $pdfSize = $pdfExists ? filesize($tmpPdf) : null;
        $elapsed = $startedAt ? round((microtime(true) - $startedAt), 2) : null;

        // 【优化】即使进程未成功，只要PDF存在且大小合理就返回
        if ($pdfExists && $pdfSize > 1000) { // 至少1KB
            Log::info('ExamPdfExportService: PDF生成成功', [
                'elapsed' => $elapsed,
                'pdf_size' => $pdfSize,
                'exit_code' => $process->getExitCode(),
                'is_successful' => $process->isSuccessful(),
            ]);

            $pdfBinary = file_get_contents($tmpPdf);
            @unlink($tmpPdf);
            File::deleteDirectory($userDataDir);
            return $pdfBinary;
        }

        // 如果PDF不存在或太小，记录错误
        Log::error('ExamPdfExportService: Chrome渲染失败', [
            'elapsed' => $elapsed,
            'pdf_exists' => $pdfExists,
            'pdf_size' => $pdfSize,
            'exit_code' => $process->getExitCode(),
            'error' => $process->getErrorOutput(),
            'output' => $process->getOutput(),
        ]);

        @unlink($tmpPdf);
        File::deleteDirectory($userDataDir);
        return null;
    }

    /**
     * 查找Chrome二进制文件
     */
    private function findChromeBinary(): ?string
    {
        $candidates = [
            env('PDF_CHROME_BINARY'),
            env('CHROME_BIN'),  // Docker Alpine 环境变量
            '/usr/bin/chromium-browser',  // Alpine Linux
            '/usr/bin/chromium',
            '/usr/bin/google-chrome-stable',
            '/usr/bin/google-chrome',
            '/Applications/Google Chrome.app/Contents/MacOS/Google Chrome',  // macOS
        ];

        foreach ($candidates as $path) {
            if ($path && is_file($path) && is_executable($path)) {
                return $path;
            }
        }

        return null;
    }

    /**
     * 确保HTML为UTF-8编码，并内联外部资源
     */
    private function ensureUtf8Html(string $html): string
    {
        $meta = '<meta charset="UTF-8">';
        if (stripos($html, '<head>') !== false) {
            $html = preg_replace('/<head>/i', "<head>{$meta}", $html, 1);
        } else {
            $html = $meta . $html;
        }

        // 【关键修复】内联KaTeX CSS，避免Chrome在容器中加载CDN资源超时
        $html = $this->inlineExternalResources($html);

        return $html;
    }

    /**
     * 将CDN资源替换为内联资源
     * 【关键修复】避免Chrome在容器中加载CDN资源超时
     */
    private function inlineExternalResources(string $html): string
    {
        // 【调试】记录HTML内容信息
        Log::warning('ExamPdfExportService: inlineExternalResources', [
            'html_length' => strlen($html),
            'has_katex_cdn' => strpos($html, 'cdn.jsdelivr.net/npm/katex') !== false,
            'html_head_preview' => substr($html, 0, 1000),
        ]);

        // 检查是否包含KaTeX CDN链接
        if (strpos($html, 'cdn.jsdelivr.net/npm/katex') === false) {
            Log::warning('ExamPdfExportService: HTML中没有KaTeX CDN链接，跳过内联');
            return $html;
        }

        try {
            // 读取本地KaTeX CSS文件并内联
            $katexCssPath = public_path('css/katex/katex.min.css');
            if (file_exists($katexCssPath)) {
                $katexCss = file_get_contents($katexCssPath);

                // 修复字体路径：将相对路径改为绝对路径（使用data URI或绝对路径）
                // KaTeX CSS中的字体引用格式: url(fonts/KaTeX_xxx.woff2)
                $fontsDir = public_path('css/katex/fonts');
                $katexCss = preg_replace_callback(
                    '/url\(["\']?fonts\/([^"\')\s]+)["\']?\)/i',
                    function ($matches) use ($fontsDir) {
                        $fontFile = $fontsDir . '/' . $matches[1];
                        if (file_exists($fontFile)) {
                            // 将字体转换为data URI（适用于PDF生成）
                            $fontData = base64_encode(file_get_contents($fontFile));
                            $mimeType = str_ends_with($matches[1], '.woff2') ? 'font/woff2' : 'font/woff';
                            return 'url(data:' . $mimeType . ';base64,' . $fontData . ')';
                        }
                        return $matches[0];
                    },
                    $katexCss
                );

                // 替换CDN CSS链接为内联样式
                $html = preg_replace(
                    '/<link[^>]*href=["\']https:\/\/cdn\.jsdelivr\.net\/npm\/katex[^"\']*katex\.min\.css["\'][^>]*>/i',
                    '<style type="text/css">' . $katexCss . '</style>',
                    $html
                );

                Log::info('ExamPdfExportService: KaTeX CSS已内联（含字体data URI）');
            }

            // 读取本地KaTeX JS并内联
            $katexJsPath = public_path('js/katex.min.js');
            $autoRenderJsPath = public_path('js/auto-render.min.js');

            if (file_exists($katexJsPath)) {
                $katexJs = file_get_contents($katexJsPath);
                $html = preg_replace(
                    '/<script[^>]*src=["\']https:\/\/cdn\.jsdelivr\.net\/npm\/katex[^"\']*katex\.min\.js["\'][^>]*><\/script>/i',
                    '<script type="text/javascript">' . $katexJs . '</script>',
                    $html
                );
            }

            if (file_exists($autoRenderJsPath)) {
                $autoRenderJs = file_get_contents($autoRenderJsPath);
                $html = preg_replace(
                    '/<script[^>]*src=["\']https:\/\/cdn\.jsdelivr\.net\/npm\/katex[^"\']*auto-render[^"\']*["\'][^>]*><\/script>/i',
                    '<script type="text/javascript">' . $autoRenderJs . '</script>',
                    $html
                );
            }

            // 【关键修复】使用服务端预渲染，而不是依赖客户端 JavaScript
            // Chrome headless 的 --print-to-pdf 不会等待 JS 执行完成
            // 所以我们使用 Node.js KaTeX 在服务端预渲染所有公式

            // 1. 移除所有 KaTeX JavaScript（不再需要，因为使用服务端渲染）
            // 移除内联的 katex.min.js
            $html = preg_replace(
                '/<script[^>]*type=["\']text\/javascript["\'][^>]*>[\s\S]*?katex[\s\S]*?<\/script>/i',
                '<!-- KaTeX JS removed, using server-side rendering -->',
                $html
            );

            // 移除 DOMContentLoaded 监听器
            $html = preg_replace(
                '/<script[^>]*>[\s\S]*?document\.addEventListener[\s\S]*?DOMContentLoaded[\s\S]*?<\/script>/i',
                '<!-- DOMContentLoaded removed -->',
                $html
            );

            // 2. 使用 KatexRenderer 进行服务端预渲染
            if ($this->katexRenderer) {
                $beforeLength = strlen($html);
                $html = $this->katexRenderer->renderHtml($html);
                $afterLength = strlen($html);

                Log::info('ExamPdfExportService: LaTeX 公式服务端预渲染完成', [
                    'before_length' => $beforeLength,
                    'after_length' => $afterLength,
                    'size_change' => $afterLength - $beforeLength,
                ]);
            } else {
                Log::warning('ExamPdfExportService: KatexRenderer 未初始化，跳过预渲染');
            }

            // 【换行处理】将字面的 \n 转换为 <br> 标签（在 KaTeX 渲染后处理，避免破坏公式）
            // 先替换所有 \n 为 <br>，然后合并连续的 <br>（最多保留2个）
            $html = str_replace('\\n', '<br>', $html);
            $html = preg_replace('/(<br>\s*){3,}/', '<br><br>', $html);  // 3个以上合并为2个

        } catch (\Exception $e) {
            Log::warning('ExamPdfExportService: 内联资源处理失败，保留原始HTML', [
                'error' => $e->getMessage()
            ]);
        }

        return $html;
    }

    /**
     * 【新增】合并两个HTML页面，插入分页符
     * 保留原始页面样式和结构，只在中间插入分页符
     */
    private function mergeHtmlWithPageBreak(string $examHtml, string $gradingHtml): ?string
    {
        try {
            // 确保HTML编码正确
            $examHtml = $this->ensureUtf8Html($examHtml);
            $gradingHtml = $this->ensureUtf8Html($gradingHtml);

            // 提取body内容
            $examBody = $this->extractBodyContent($examHtml);
            $gradingBody = $this->extractBodyContent($gradingHtml);

            if (empty($examBody) || empty($gradingBody)) {
                Log::error('ExamPdfExportService: HTML内容提取失败', [
                    'exam_body_length' => strlen($examBody),
                    'grading_body_length' => strlen($gradingBody)
                ]);
                return null;
            }

            // 提取head内容（保留原始样式和meta信息）
            $examHead = $this->extractHeadContent($examHtml);

            // 构建统一HTML文档（保留原始结构）
            $unifiedHtml = $this->buildUnifiedHtmlWithOriginalStructure($examHead, $examBody, $gradingBody);

            Log::info('HTML合并成功（保留原始样式）', [
                'exam_length' => strlen($examBody),
                'grading_length' => strlen($gradingBody),
                'unified_length' => strlen($unifiedHtml),
                'head_length' => strlen($examHead)
            ]);

            return $unifiedHtml;

        } catch (\Throwable $e) {
            Log::error('mergeHtmlWithPageBreak 失败', [
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString()
            ]);
            return null;
        }
    }

    /**
     * 【新增】提取HTML的body内容
     */
    private function extractBodyContent(string $html): string
    {
        // 匹配body标签内容
        if (preg_match('/<body[^>]*>(.*)<\/body>/is', $html, $matches)) {
            return $matches[1];
        }

        // 如果没有body标签，返回整个HTML
        return $html;
    }

    /**
     * 【新增】提取HTML的head内容
     * 保留原始页面的样式和meta信息
     */
    private function extractHeadContent(string $html): string
    {
        // 匹配head标签内容
        if (preg_match('/<head[^>]*>(.*)<\/head>/is', $html, $matches)) {
            return $matches[1];
        }

        // 如果没有head标签，返回默认meta
        return '<meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0">';
    }

    /**
     * 【新增】构建统一的HTML文档（保留原始结构）
     * 保留第一个HTML的完整head和样式，只在body之间插入分页符
     */
    private function buildUnifiedHtmlWithOriginalStructure(string $examHead, string $examBody, string $gradingBody): string
    {
        // 保留原始head内容，添加分页符样式
        $headContent = $examHead . '
    <style>
        /* 分页符样式 - 插入到原始样式之后 */
        .page-break {
            page-break-before: always;
            page-break-after: always;
            break-before: page;
            break-after: page;
        }

        /* 确保分页符在打印时生效 */
        @media print {
            .page-break {
                page-break-before: always;
            }
        }
    </style>';

        return '<!DOCTYPE html>
<html lang="zh-CN">
<head>
' . $headContent . '
</head>
<body>
    <!-- 第一部分：试卷（不含答案） -->
    ' . $examBody . '

    <!-- 分页符：第二部分从这里开始 -->
    <div class="page-break"></div>

    <!-- 第二部分：判卷（含答案与解析） -->
    ' . $gradingBody . '
</body>
</html>';
    }

    /**
     * 【新增】获取PDF通用样式
     */
    private function getCommonPdfStyles(): string
    {
        return '
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: "Microsoft YaHei", "SimHei", Arial, sans-serif;
            font-size: 14px;
            line-height: 1.6;
            color: #333;
            background: #fff;
        }

        .paper-container {
            max-width: 210mm;
            margin: 0 auto;
            padding: 20mm;
            background: white;
        }

        .paper-header {
            text-align: center;
            margin-bottom: 30px;
            padding-bottom: 15px;
            border-bottom: 2px solid #333;
        }

        .paper-title {
            font-size: 24px;
            font-weight: bold;
            margin-bottom: 10px;
        }

        .paper-info {
            font-size: 14px;
            color: #666;
        }

        .question {
            margin-bottom: 30px;
            padding: 20px;
            border: 1px solid #ddd;
            border-radius: 5px;
        }

        .question-number {
            font-weight: bold;
            margin-bottom: 10px;
        }

        .question-stem {
            margin-bottom: 15px;
        }

        .options {
            list-style: none;
            margin-left: 20px;
        }

        .options li {
            margin-bottom: 8px;
        }

        .answer-section {
            margin-top: 20px;
            padding-top: 15px;
            border-top: 1px solid #eee;
        }

        .answer-label {
            font-weight: bold;
            color: #d9534f;
        }

        .solution {
            margin-top: 10px;
            padding: 10px;
            background: #f5f5f5;
            border-left: 4px solid #5bc0de;
        }
        ';
    }

    /**
     * 构建知识点名称映射
     */
    private function buildKnowledgePointNameMap(): array
    {
        try {
            $options = $this->questionServiceApi->getKnowledgePointOptions();
            return $options ?: [];
        } catch (\Throwable $e) {
            Log::warning('ExamPdfExportService: 获取知识点名称失败', [
                'error' => $e->getMessage(),
            ]);
            return [];
        }
    }

    /**
     * 构建掌握度摘要
     */
    private function buildMasterySummary(array $masteryData, array $kpNameMap): array
    {
        Log::info('ExamPdfExportService: buildMasterySummary开始处理', [
            'masteryData_count' => count($masteryData),
            'kpNameMap_count' => count($kpNameMap)
        ]);

        $items = [];
        $total = 0;
        $count = 0;

        foreach ($masteryData as $row) {
            $code = $row['kp_code'] ?? null;
            // 【修复】使用kpNameMap转换名称为友好显示名
            $name = $kpNameMap[$code] ?? $row['kp_name'] ?? $code ?: '未知知识点';
            $level = (float)($row['mastery_level'] ?? 0);
            $delta = $row['mastery_change'] ?? null;

            $items[] = [
                'kp_code' => $code,
                'kp_name' => $name,
                'mastery_level' => $level,
                'mastery_change' => $delta,
            ];

            $total += $level;
            $count++;
        }

        $average = $count > 0 ? round($total / $count, 2) : null;

        // 按掌握度从低到高排序
        if (!empty($items)) {
            usort($items, fn($a, $b) => ($a['mastery_level'] <=> $b['mastery_level']));
        }

        $result = [
            'items' => $items,
            'average' => $average,
            'weak_list' => array_slice($items, 0, 5),
        ];

        Log::info('ExamPdfExportService: buildMasterySummary完成', [
            'total_count' => $count,
            'items_count' => count($items)
        ]);

        return $result;
    }

    /**
     * 标准化题型
     */
    private function normalizeQuestionType(string $type): string
    {
        $t = strtolower(trim($type));
        return match (true) {
            str_contains($t, 'choice') || str_contains($t, '选择') => 'choice',
            str_contains($t, 'fill') || str_contains($t, 'blank') || str_contains($t, '填空') => 'fill',
            default => 'answer',
        };
    }

    /**
     * 保存PDF URL到数据库
     */
    private function savePdfUrlToDatabase(string $paperId, string $field, string $url): void
    {
        try {
            $paper = Paper::where('paper_id', $paperId)->first();
            if ($paper) {
                $paper->update([$field => $url]);
                Log::info('ExamPdfExportService: PDF URL已写入数据库', [
                    'paper_id' => $paperId,
                    'field' => $field,
                    'url' => $url,
                ]);
            }
        } catch (\Throwable $e) {
            Log::error('ExamPdfExportService: 写入PDF URL失败', [
                'paper_id' => $paperId,
                'field' => $field,
                'error' => $e->getMessage(),
            ]);
        }
    }

    /**
     * 保存学情分析PDF URL
     */
    private function saveAnalysisPdfUrl(string $paperId, string $studentId, ?string $recordId, string $url): void
    {
        try {
            if ($recordId) {
                // OCR记录
                $ocrRecord = \App\Models\OCRRecord::find($recordId);
                if ($ocrRecord) {
                    $ocrRecord->update(['analysis_pdf_url' => $url]);
                    Log::info('ExamPdfExportService: OCR记录学情分析PDF URL已写入数据库', [
                        'record_id' => $recordId,
                        'paper_id' => $paperId,
                        'student_id' => $studentId,
                        'url' => $url,
                    ]);
                }
            } else {
                // 【修复】同时更新 exam_analysis_results 表和分析报告表
                $updated = \DB::connection('mysql')->table('exam_analysis_results')
                    ->where('student_id', $studentId)
                    ->where('paper_id', $paperId)
                    ->update([
                        'analysis_pdf_url' => $url,
                        'updated_at' => now(),
                    ]);

                if ($updated) {
                    Log::info('ExamPdfExportService: 学情分析PDF URL已写入exam_analysis_results表', [
                        'student_id' => $studentId,
                        'paper_id' => $paperId,
                        'url' => $url,
                        'updated_rows' => $updated,
                    ]);
                } else {
                    Log::warning('ExamPdfExportService: 未找到要更新的学情分析记录', [
                        'student_id' => $studentId,
                        'paper_id' => $paperId,
                    ]);
                }

                // 学生记录 - 使用新的 student_reports 表（备用）
                \App\Models\StudentReport::updateOrCreate(
                    [
                        'student_id' => $studentId,
                        'report_type' => 'exam_analysis',
                        'paper_id' => $paperId,
                    ],
                    [
                        'pdf_url' => $url,
                        'generation_status' => 'completed',
                        'generated_at' => now(),
                        'updated_at' => now(),
                    ]
                );

                Log::info('ExamPdfExportService: 学生学情报告PDF URL已保存到student_reports表（备用）', [
                    'student_id' => $studentId,
                    'paper_id' => $paperId,
                    'url' => $url,
                ]);
            }
        } catch (\Throwable $e) {
            Log::error('ExamPdfExportService: 写入学情分析PDF URL失败', [
                'paper_id' => $paperId,
                'student_id' => $studentId,
                'record_id' => $recordId,
                'error' => $e->getMessage(),
            ]);
        }
    }

    /**
     * 【修复】处理父节点掌握度数据
     * 1. 过滤掉掌握度为0或null的父节点
     * 2. 将kp_code转换为友好的kp_name
     * 3. 构建父子层级关系（只显示本次考试相关的子节点）
     */
    private function processParentMasteryLevels(array $parentMasteryLevels, array $kpNameMap, array $examKpCodes = []): array
    {
        $processed = [];

        foreach ($parentMasteryLevels as $kpCode => $masteryData) {
            // 兼容不同数据结构：可能是数组或数字
            $masteryLevel = is_array($masteryData) ? ($masteryData['mastery_level'] ?? 0) : $masteryData;
            $masteryChange = is_array($masteryData) ? ($masteryData['mastery_change'] ?? null) : null;

            // 过滤零值和空值
            if ($masteryLevel === null || $masteryLevel === 0.0 || $masteryLevel <= 0.001) {
                continue;
            }

            // 获取友好名称
            $kpName = $kpNameMap[$kpCode] ?? $kpCode;

            // 构建父节点数据，包含子节点信息（只显示本次考试相关的）
            $processed[$kpCode] = [
                'kp_code' => $kpCode,
                'kp_name' => $kpName,
                'mastery_level' => round(floatval($masteryLevel), 4),
                'mastery_percentage' => round(floatval($masteryLevel) * 100, 2),
                'mastery_change' => $masteryChange !== null ? round(floatval($masteryChange), 4) : null,
                // 【修复】只获取本次考试涉及的子节点
                'children' => $this->getChildKnowledgePoints($kpCode, $kpNameMap, $examKpCodes),
                'level' => $this->calculateKnowledgePointLevel($kpCode),
            ];
        }

        // 按掌握度降序排序
        uasort($processed, function($a, $b) {
            return $b['mastery_level'] <=> $a['mastery_level'];
        });

        return $processed;
    }

    /**
     * 【修复】获取子知识点列表（只返回本次考试涉及的）
     */
    private function getChildKnowledgePoints(string $parentKpCode, array $kpNameMap, array $examKpCodes = []): array
    {
        $children = [];

        try {
            $childCodes = DB::connection('mysql')
                ->table('knowledge_points')
                ->where('parent_kp_code', $parentKpCode)
                ->pluck('kp_code')
                ->toArray();

            foreach ($childCodes as $childCode) {
                // 只包含本次考试涉及的知识点
                if (in_array($childCode, $examKpCodes)) {
                    $children[] = [
                        'kp_code' => $childCode,
                        'kp_name' => $kpNameMap[$childCode] ?? $childCode,
                    ];
                }
            }
        } catch (\Exception $e) {
            Log::warning('获取子知识点失败', [
                'parent_kp_code' => $parentKpCode,
                'error' => $e->getMessage(),
            ]);
        }

        return $children;
    }

    /**
     * 计算知识点层级深度
     */
    private function calculateKnowledgePointLevel(string $kpCode): int
    {
        // 根据kp_code前缀判断层级深度
        // 例如: M (1级) -> M01 (2级) -> M01A (3级)
        if (preg_match('/^[A-Z]+$/', $kpCode)) {
            return 1; // 一级分类，如 M, S, E, G
        } elseif (preg_match('/^[A-Z]+\d+$/', $kpCode)) {
            return 2; // 二级分类，如 M01, S02
        } elseif (preg_match('/^[A-Z]+\d+[A-Z]+$/', $kpCode)) {
            return 3; // 三级分类，如 M01A, S02B
        } elseif (preg_match('/^[A-Z]+\d+[A-Z]+\d+$/', $kpCode)) {
            return 4; // 四级分类，如 M01A1
        }

        return 1; // 默认一级
    }

    /**
     * 构建题目数据（用于PDF生成）
     */
    private function buildQuestionsData(Paper $paper): array
    {
        $paperQuestions = $paper->questions()->orderBy('question_number')->get();
        $questionsData = [];
        foreach ($paperQuestions as $pq) {
            $questionsData[] = [
                'id' => $pq->question_bank_id,
                'kp_code' => $pq->knowledge_point,
                'question_type' => $pq->question_type ?? 'answer',
                'stem' => $pq->question_text ?? '题目内容缺失',
                'solution' => $pq->solution ?? '',
                'answer' => $pq->correct_answer ?? '',
                'difficulty' => $pq->difficulty ?? 0.5,
                'score' => $pq->score ?? 5,
                'tags' => '',
                'content' => $pq->question_text ?? '',
            ];
        }

        // 获取完整题目详情
        if (!empty($questionsData)) {
            $questionIds = array_column($questionsData, 'id');
            $questionsResponse = $this->questionServiceApi->getQuestionsByIds($questionIds);
            $responseData = $questionsResponse['data'] ?? [];

            if (!empty($responseData)) {
                $responseDataMap = [];
                foreach ($responseData as $respQ) {
                    $responseDataMap[$respQ['id']] = $respQ;
                }

                $questionsData = array_map(function($q) use ($responseDataMap) {
                    if (isset($responseDataMap[$q['id']])) {
                        $apiData = $responseDataMap[$q['id']];
                        $q['stem'] = $apiData['stem'] ?? $q['stem'] ?? $q['content'] ?? '';
                        $q['content'] = $q['stem'];
                        $q['answer'] = $apiData['answer'] ?? $q['answer'] ?? '';
                        $q['solution'] = $apiData['solution'] ?? $q['solution'] ?? '';
                        $q['tags'] = $apiData['tags'] ?? $q['tags'] ?? '';
                        $q['options'] = $apiData['options'] ?? [];
                    }
                    return $q;
                }, $questionsData);
            }
        }

        // 按题型分类
        $classified = ['choice' => [], 'fill' => [], 'answer' => []];
        foreach ($questionsData as $q) {
            $type = $this->determineQuestionType($q);
            $classified[$type][] = (object) $q;
        }

        return $classified;
    }

    /**
     * 获取学生信息
     */
    private function getStudentInfo(?string $studentId): array
    {
        if (!$studentId) {
            return [
                'name' => '未知学生',
                'grade' => '未知年级',
                'class' => '未知班级'
            ];
        }

        try {
            $student = DB::table('students')
                ->where('student_id', $studentId)
                ->first();

            if ($student) {
                return [
                    'name' => $student->name ?? $studentId,
                    'grade' => $student->grade ?? '未知',
                    'class' => $student->class ?? '未知'
                ];
            }
        } catch (\Exception $e) {
            Log::warning('获取学生信息失败', [
                'student_id' => $studentId,
                'error' => $e->getMessage()
            ]);
        }

        return [
            'name' => $studentId,
            'grade' => '未知',
            'class' => '未知'
        ];
    }

    /**
     * 获取教师信息
     */
    private function getTeacherInfo(?string $teacherId): array
    {
        if (!$teacherId) {
            return [
                'name' => '未知老师',
                'subject' => '数学'
            ];
        }

        try {
            $teacher = DB::table('teachers')
                ->where('teacher_id', $teacherId)
                ->first();

            if ($teacher) {
                return [
                    'name' => $teacher->name ?? $teacherId,
                    'subject' => $teacher->subject ?? '数学'
                ];
            }
        } catch (\Exception $e) {
            Log::warning('获取教师信息失败', [
                'teacher_id' => $teacherId,
                'error' => $e->getMessage()
            ]);
        }

        return [
            'name' => $teacherId,
            'subject' => '数学'
        ];
    }

    /**
     * 判断题目类型
     */
    private function determineQuestionType(array $question): string
    {
        $stem = $question['stem'] ?? $question['content'] ?? '';
        $tags = $question['tags'] ?? '';

        // 根据题干内容判断选择题
        if (is_string($stem)) {
            $hasOptionA = preg_match('/\bA\s*[\.\、\:]/', $stem) || preg_match('/\(A\)/', $stem) || preg_match('/^A[\.\s]/', $stem);
            $hasOptionB = preg_match('/\bB\s*[\.\、\:]/', $stem) || preg_match('/\(B\)/', $stem) || preg_match('/^B[\.\s]/', $stem);
            $hasOptionC = preg_match('/\bC\s*[\.\、\:]/', $stem) || preg_match('/\(C\)/', $stem) || preg_match('/^C[\.\s]/', $stem);
            $hasOptionD = preg_match('/\bD\s*[\.\、\:]/', $stem) || preg_match('/\(D\)/', $stem) || preg_match('/^D[\.\s]/', $stem);

            $optionCount = ($hasOptionA ? 1 : 0) + ($hasOptionB ? 1 : 0) + ($hasOptionC ? 1 : 0) + ($hasOptionD ? 1 : 0);
            if ($optionCount >= 2) {
                return 'choice';
            }

            // 检查是否有填空标记
            if (preg_match('/（\s*）|\(\s*\)/', $stem)) {
                return 'fill';
            }
        }

        // 根据已有类型字段判断
        if (!empty($question['question_type'])) {
            $type = strtolower(trim($question['question_type']));
            if (in_array($type, ['choice', '选择题'])) return 'choice';
            if (in_array($type, ['fill', '填空题'])) return 'fill';
            if (in_array($type, ['answer', '解答题'])) return 'answer';
        }

        // 默认返回解答题
        return 'answer';
    }

    /**
     * 格式化换行符：将字面的 \n 转换为 HTML <br> 标签
     * 用于 PDF 渲染时正确显示换行
     */
    private function formatNewlines(?string $text): ?string
    {
        if ($text === null) {
            return null;
        }
        // 替换 \n 为 <br>，然后合并连续的 <br>（最多保留2个）
        $text = str_replace('\\n', '<br>', $text);
        return preg_replace('/(<br>\s*){3,}/', '<br><br>', $text);
    }

    /**
     * 根据指定的题目生成PDF（新增方法）
     *
     * @param object $paper 虚拟试卷对象
     * @param array $groupedQuestions 按题型分组的题目数据
     * @param array $student 学生信息 ['name' => '', 'grade' => '']
     * @param array $teacher 教师信息 ['name' => '']
     * @param bool $includeGrading 是否包含判卷版本
     * @return array 返回 ['pdf_url' => '...', 'grading_pdf_url' => '...']
     */
    public function generateByQuestions(
        object $paper,
        array $groupedQuestions,
        array $student = [],
        array $teacher = [],
        bool $includeGrading = false
    ): array {
        Log::info('generateByQuestions 开始', [
            'paper_id' => $paper->paper_id,
            'question_counts' => [
                'choice' => count($groupedQuestions['choice'] ?? []),
                'fill' => count($groupedQuestions['fill'] ?? []),
                'answer' => count($groupedQuestions['answer'] ?? []),
            ],
            'include_grading' => $includeGrading,
        ]);

        try {
            $result = [];

            // 1. 生成试卷PDF（不含答案）
            $examHtml = $this->renderCustomExamHtml($paper, $groupedQuestions, $student, $teacher, false);
            if ($examHtml) {
                $examPdf = $this->buildPdf($examHtml);
                if ($examPdf) {
                    $examPath = "custom_exams/{$paper->paper_id}_exam.pdf";
                    $examUrl = $this->pdfStorageService->put($examPath, $examPdf);
                    $result['pdf_url'] = $examUrl;
                    Log::info('试卷PDF生成成功', ['url' => $examUrl]);
                }
            }

            // 2. 如果需要，生成判卷PDF（含答案）
            if ($includeGrading) {
                $gradingHtml = $this->renderCustomExamHtml($paper, $groupedQuestions, $student, $teacher, true);
                if ($gradingHtml) {
                    $gradingPdf = $this->buildPdf($gradingHtml);
                    if ($gradingPdf) {
                        $gradingPath = "custom_exams/{$paper->paper_id}_grading.pdf";
                        $gradingUrl = $this->pdfStorageService->put($gradingPath, $gradingPdf);
                        $result['grading_pdf_url'] = $gradingUrl;
                        Log::info('判卷PDF生成成功', ['url' => $gradingUrl]);
                    }
                }
            }

            return $result;

        } catch (\Throwable $e) {
            Log::error('generateByQuestions 失败', [
                'paper_id' => $paper->paper_id,
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            throw $e;
        }
    }

    /**
     * 渲染自定义题目的HTML
     */
    private function renderCustomExamHtml(
        object $paper,
        array $groupedQuestions,
        array $student,
        array $teacher,
        bool $grading
    ): ?string {
        try {
            $viewName = $grading ? 'pdf.exam-grading' : 'pdf.exam-paper';

            $html = view($viewName, [
                'paper' => $paper,
                'questions' => $groupedQuestions,
                'student' => $student,
                'teacher' => $teacher,
                'grading' => $grading,
            ])->render();

            if (empty(trim($html))) {
                Log::error('renderCustomExamHtml: 视图渲染结果为空', [
                    'paper_id' => $paper->paper_id,
                    'view_name' => $viewName,
                ]);
                return null;
            }

            return $this->ensureUtf8Html($html);

        } catch (\Exception $e) {
            Log::error('renderCustomExamHtml 失败', [
                'paper_id' => $paper->paper_id,
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            return null;
        }
    }
}