<?php

namespace App\Services;

use App\Http\Controllers\ExamPdfController;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Facades\URL;
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 {
        try {
            $html = $this->renderHtml($paperId, $includeAnswer, $useGradingView);
            if (!$html) {
                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()
            ]);
            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
    {
        // 使用无头 Chrome 渲染 HTML，保留前端样式并彻底解决大量空白页问题
        $tmpHtml = tempnam(sys_get_temp_dir(), 'exam_html_') . '.html';
        $tmpPdf = tempnam(sys_get_temp_dir(), 'exam_pdf_') . '.pdf';

        file_put_contents($tmpHtml, $this->ensureUtf8Html($html));

        $chromeBinary = env('PDF_CHROME_BINARY');
        if (!$chromeBinary) {
            // 默认优先 Mac，本地开发；不存在则尝试常见 Linux 路径
            $candidates = [
                '/Applications/Google Chrome.app/Contents/MacOS/Google Chrome',
                '/usr/bin/chromium-browser',
                '/usr/bin/chromium',
                '/usr/bin/google-chrome',
            ];
            foreach ($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 可执行文件');
            return null;
        }
        $process = new Process([
            $chromeBinary,
            '--headless',
            '--disable-gpu',
            '--no-sandbox',
            '--print-to-pdf=' . $tmpPdf,
            '--print-to-pdf-no-header',
            '--allow-file-access-from-files',
            'file://' . $tmpHtml,
        ]);
        $process->setTimeout(30);
        $process->run();

        if (!$process->isSuccessful() || !file_exists($tmpPdf)) {
            Log::error('ExamPdfExportService: Chrome 渲染失败', [
                'error' => $process->getErrorOutput(),
                'output' => $process->getOutput(),
            ]);
            @unlink($tmpHtml);
            @unlink($tmpPdf);
            return null;
        }

        $pdfBinary = file_get_contents($tmpPdf);
        @unlink($tmpHtml);
        @unlink($tmpPdf);

        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;
    }

}