<?php

namespace App\Services;

use App\Http\Controllers\ExamPdfController;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\File;
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;

class ExamPdfExportService
{
    private ExamPdfController $controller;

    public function __construct(ExamPdfController $controller)
    {
        $this->controller = $controller;
    }

    /**
        生成试卷 PDF（不含答案）
     */
    public function generateExamPdf(string $paperId): ?string
    {
        return $this->renderAndStore($paperId, includeAnswer: false, suffix: 'exam');
    }

    /**
        生成判卷 PDF（含答案与解析）
     */
    public function generateGradingPdf(string $paperId): ?string
    {
        return $this->renderAndStore($paperId, includeAnswer: true, suffix: 'grading', useGradingView: true);
    }

    private function renderAndStore(
        string $paperId,
        bool $includeAnswer,
        string $suffix,
        bool $useGradingView = false
    ): ?string {
        // 放宽脚本执行时间，避免长耗时渲染被 PHP 全局超时打断
        if (function_exists('set_time_limit')) {
            @set_time_limit(240);
        }

        try {
            $html = $this->renderHtml($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) {
                return null;
            }

            $path = "exams/{$paperId}_{$suffix}.pdf";
            Storage::disk('public')->put($path, $pdfBinary);

            return URL::to(Storage::url($path));
        } 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;
        }
    }

    private function renderHtml(string $paperId, bool $includeAnswer, bool $useGradingView): ?string
    {
        // 复用已有控制器的渲染逻辑，保证版式一致
        $request = Request::create(
            '/admin/intelligent-exam/' . ($useGradingView ? 'grading' : 'pdf') . '/' . $paperId,
            'GET',
            ['answer' => $includeAnswer ? 'true' : 'false']
        );

        $view = $useGradingView
            ? $this->controller->showGrading($request, $paperId)
            : $this->controller->show($request, $paperId);

        if (is_object($view) && method_exists($view, 'render')) {
            return $this->ensureUtf8Html($view->render());
        }

        return null;
    }

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

        // 仅使用 Chrome 渲染，去掉 wkhtmltopdf 兜底以暴露真实问题
        $chromePdf = $this->renderWithChrome($tmpHtml);
        @unlink($tmpHtml);
        return $chromePdf;
    }

    private function renderWithChrome(string $htmlPath): ?string
    {
        $tmpPdf = tempnam(sys_get_temp_dir(), 'exam_pdf_') . '.pdf';
        // 固定用户目录，减少 Chrome 首次初始化开销；允许多进程并发时可按需加锁
        $userDataDir = sys_get_temp_dir() . '/chrome-pdf-profile';

        $chromeBinary = env('PDF_CHROME_BINARY');
        if (!$chromeBinary) {
            $candidates = [
                '/Applications/Google Chrome.app/Contents/MacOS/Google Chrome',
                '/usr/bin/google-chrome-stable',
                '/usr/bin/google-chrome',
                '/usr/bin/chromium-browser',
                '/usr/bin/chromium',
            ];
            foreach ($candidates as $path) {
                if (is_file($path) && is_executable($path)) {
                    $chromeBinary = $path;
                    break;
                }
            }
        }

        if (!$chromeBinary) {
            Log::error('ExamPdfExportService: 未找到可用的 Chrome/Chromium，已停止导出', [
                'html_path' => $htmlPath,
                'path_env' => env('PATH'),
                'candidates_checked' => $candidates ?? [],
            ]);
            return null;
        }

        $process = new Process([
            $chromeBinary,
            '--headless',
            '--disable-gpu',
            '--no-sandbox',
            '--disable-setuid-sandbox',
            '--disable-dev-shm-usage',
            '--no-zygote',
            '--disable-features=VizDisplayCompositor',
            '--disable-software-rasterizer',
            '--disable-extensions',
            '--disable-background-networking',
            '--disable-component-update',
            '--disable-client-side-phishing-detection',
            '--disable-default-apps',
            '--disable-domain-reliability',
            '--disable-sync',
            '--safebrowsing-disable-auto-update',
            '--no-first-run',
            '--no-default-browser-check',
            '--disable-crash-reporter',
            '--disable-print-preview',
            '--user-data-dir=' . $userDataDir,
            '--print-to-pdf=' . $tmpPdf,
            '--print-to-pdf-no-header',
            '--allow-file-access-from-files',
            'file://' . $htmlPath,
        ]);
        $process->setTimeout(60);

        try {
            $startedAt = microtime(true);
            Log::info('ExamPdfExportService: Chrome 渲染启动', [
                'cmd' => $process->getCommandLine(),
                'html_path' => $htmlPath,
                'tmp_pdf' => $tmpPdf,
                'user_data_dir' => $userDataDir,
                'html_exists' => file_exists($htmlPath),
                'html_size' => file_exists($htmlPath) ? filesize($htmlPath) : null,
                'cwd' => $process->getWorkingDirectory(),
            ]);
            $process->start();
            $pdfGenerated = false;

            // 轮询检测 PDF 是否生成，尽快返回，避免等待 Chrome 完整退出
            $pollStart = microtime(true);
            $maxPollSeconds = 45;
            while ($process->isRunning() && (microtime(true) - $pollStart) < $maxPollSeconds) {
                if (file_exists($tmpPdf) && filesize($tmpPdf) > 0) {
                    $pdfGenerated = true;
                    Log::info('ExamPdfExportService: 发现 PDF 已生成，提前结束 Chrome', [
                        'duration_sec' => round(microtime(true) - $startedAt, 3),
                        'tmp_pdf_size' => filesize($tmpPdf),
                    ]);
                    $process->stop(5, SIGKILL);
                    break;
                }
                usleep(200_000); // 200ms
            }

            // 如果仍在运行且超过轮询窗口，则强制结束
            if ($process->isRunning()) {
                Log::warning('ExamPdfExportService: Chrome 轮询超时，强制结束', [
                    'duration_sec' => round(microtime(true) - $startedAt, 3),
                ]);
                $process->stop(5, SIGKILL);
            }

            $process->wait();
            Log::info('ExamPdfExportService: Chrome 渲染完成', [
                'duration_sec' => round(microtime(true) - $startedAt, 3),
                'exit_code' => $process->getExitCode(),
                'tmp_pdf_exists' => file_exists($tmpPdf),
                'tmp_pdf_size' => file_exists($tmpPdf) ? filesize($tmpPdf) : null,
                'stderr' => $process->getErrorOutput(),
                'stdout' => $process->getOutput(),
                'pdf_generated_during_poll' => $pdfGenerated,
            ]);
        } catch (ProcessTimedOutException|ProcessSignaledException $e) {
            Log::error('ExamPdfExportService: Chrome 进程异常', [
                'cmd' => $process->getCommandLine(),
                'signal' => method_exists($process, 'getTermSignal') ? $process->getTermSignal() : null,
                'error' => $process->getErrorOutput(),
                'output' => $process->getOutput(),
                'exit_code' => $process->getExitCode(),
                'exception' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            if ($process->isRunning()) {
                $process->stop(5, SIGKILL);
            }
            $pdfExists = file_exists($tmpPdf);
            $pdfSize = $pdfExists ? filesize($tmpPdf) : null;
            if ($pdfExists && $pdfSize > 0) {
                Log::warning('ExamPdfExportService: Chrome 异常但产生了 PDF，尝试继续返回', [
                    'tmp_pdf_exists' => $pdfExists,
                    'tmp_pdf_size' => $pdfSize,
                    'duration_sec' => isset($startedAt) ? round(microtime(true) - $startedAt, 3) : null,
                ]);
                $pdfBinary = file_get_contents($tmpPdf);
                @unlink($tmpPdf);
                File::deleteDirectory($userDataDir);
                return $pdfBinary ?: null;
            }
            @unlink($tmpPdf);
            File::deleteDirectory($userDataDir);
            return null;
        } catch (\Throwable $e) {
            Log::error('ExamPdfExportService: Chrome 调用异常', [
                'cmd' => $process->getCommandLine(),
                'error' => $e->getMessage(),
                'exit_code' => $process->getExitCode(),
                'stderr' => $process->getErrorOutput(),
                'stdout' => $process->getOutput(),
                'trace' => $e->getTraceAsString(),
            ]);
            if ($process->isRunning()) {
                $process->stop(5, SIGKILL);
            }
            $pdfExists = file_exists($tmpPdf);
            $pdfSize = $pdfExists ? filesize($tmpPdf) : null;
            if ($pdfExists && $pdfSize > 0) {
                Log::warning('ExamPdfExportService: Chrome 调用异常但产生了 PDF，尝试继续返回', [
                    'tmp_pdf_exists' => $pdfExists,
                    'tmp_pdf_size' => $pdfSize,
                    'duration_sec' => isset($startedAt) ? round(microtime(true) - $startedAt, 3) : null,
                ]);
                $pdfBinary = file_get_contents($tmpPdf);
                @unlink($tmpPdf);
                File::deleteDirectory($userDataDir);
                return $pdfBinary ?: null;
            }
            @unlink($tmpPdf);
            File::deleteDirectory($userDataDir);
            return null;
        }

        $pdfExists = file_exists($tmpPdf);
        $pdfSize = $pdfExists ? filesize($tmpPdf) : null;

        if (!$process->isSuccessful()) {
            if ($pdfExists && $pdfSize > 0) {
                Log::warning('ExamPdfExportService: Chrome 进程异常但生成了 PDF，继续使用', [
                    'cmd' => implode(' ', (array) $process->getCommandLine()),
                    'exit_code' => $process->getExitCode(),
                    'error' => $process->getErrorOutput(),
                    'output' => $process->getOutput(),
                    'tmp_pdf_exists' => $pdfExists,
                    'tmp_pdf_size' => $pdfSize,
                    'html_path' => $htmlPath,
                    'user_data_dir' => $userDataDir,
                ]);
            } else {
                Log::error('ExamPdfExportService: Chrome 渲染失败', [
                    'cmd' => implode(' ', (array) $process->getCommandLine()),
                    'exit_code' => $process->getExitCode(),
                    'error' => $process->getErrorOutput(),
                    'output' => $process->getOutput(),
                    'tmp_pdf_exists' => $pdfExists,
                    'tmp_pdf_size' => $pdfSize,
                    'html_path' => $htmlPath,
                    'user_data_dir' => $userDataDir,
                ]);
                @unlink($tmpPdf);
                File::deleteDirectory($userDataDir);
                return null;
            }
        }

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

    private function ensureUtf8Html(string $html): string
    {
        $meta = '<meta charset="UTF-8">';
        if (stripos($html, '<head>') !== false) {
            return preg_replace('/<head>/i', "<head>{$meta}", $html, 1);
        }
        return $meta . $html;
    }

}