<?php

namespace App\Services;

use App\Models\Document;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Str;
use Paperdoc\Contracts\DocumentInterface;
use Paperdoc\Document\Image;
use Paperdoc\Support\DocumentManager;

/**
 * 文档转换服务
 * 使用 paperdoc-lib 将文档（DOCX/PPTX/XLSX/PDF）转换为 Markdown
 */
class DocumentConversionService
{
    protected int $previewLength;

    public function __construct()
    {
        $this->previewLength = config('documents.markdown.preview_length', 500);
    }

    /**
     * 将文档转换为 Markdown
     *
     * @return array{markdown: string, media_files: array<string, string>}
     */
    public function convertToMarkdown(Document $document): array
    {
        $this->ensureConversionDependenciesAvailable();

        $documentPath = Storage::disk('local')->path($document->file_path);

        if (!file_exists($documentPath)) {
            throw new \Exception("文档文件不存在: {$documentPath}");
        }

        $doc = DocumentManager::open($documentPath, ['ocr' => false]);
        $markdown = DocumentManager::renderAs($doc, 'md');

        if (empty(trim($markdown))) {
            throw new \Exception('文档转换后内容为空，可能是扫描件或不支持的内容格式');
        }

        return [
            'markdown' => $markdown,
            'media_files' => $this->extractMarkdownMediaFiles($doc),
        ];
    }

    /**
     * 确保文档转换依赖已经安装
     */
    protected function ensureConversionDependenciesAvailable(): void
    {
        if (!class_exists(DocumentManager::class)) {
            throw new \RuntimeException(
                '文档转换依赖未安装：paperdoc-dev/paperdoc-lib。请执行 composer install 后重试。'
            );
        }
    }

    /**
     * 将 Markdown 内容保存到存储
     *
     * @param array<string, string> $mediaFiles
     */
    public function saveMarkdownToFile(Document $document, string $markdown, array $mediaFiles = []): string
    {
        $path = $this->generateMarkdownPath($document);

        $saved = Storage::disk('markdown')->put($path, $markdown);
        if (!$saved) {
            throw new \Exception('无法保存 Markdown 文件');
        }

        $this->storeMarkdownMediaFiles(dirname($path), $mediaFiles);

        return $path;
    }

    /**
     * 为已存在的 Markdown 文档补齐缺失的图片资源
     */
    public function ensureMarkdownMediaAssets(Document $document): void
    {
        $this->ensureConversionDependenciesAvailable();

        if (empty($document->markdown_path)) {
            return;
        }

        $markdown = $document->getMarkdownContent();
        if (empty($markdown)) {
            return;
        }

        if (!preg_match_all('/!\[[^\]]*]\(((?:\.\/)?media\/[^)]+)\)/', $markdown, $matches)) {
            return;
        }

        $documentDir = dirname($document->markdown_path);
        $missingRefs = [];

        foreach ($matches[1] as $ref) {
            $relativePath = $this->normalizeMarkdownMediaPath($ref);

            if ($relativePath === null) {
                continue;
            }

            if (!Storage::disk('markdown')->exists($documentDir . '/' . $relativePath)) {
                $missingRefs[] = $relativePath;
            }
        }

        if ($missingRefs === []) {
            return;
        }

        $documentPath = Storage::disk('local')->path($document->file_path);
        if (!file_exists($documentPath)) {
            throw new \Exception("文档文件不存在: {$documentPath}");
        }

        $doc = DocumentManager::open($documentPath, ['ocr' => false]);
        $mediaFiles = array_intersect_key(
            $this->extractMarkdownMediaFiles($doc),
            array_flip($missingRefs)
        );

        $this->storeMarkdownMediaFiles($documentDir, $mediaFiles);
    }

    /**
     * 生成 Markdown 文件路径
     */
    protected function generateMarkdownPath(Document $document): string
    {
        $organizeByDate = config('documents.storage.organize_by_date', true);
        $uuid = Str::uuid()->toString();

        if ($organizeByDate) {
            $date = $document->created_at ?? now();
            $directory = $date->format('Y/m/d') . '/' . $uuid;
        } else {
            $directory = $uuid;
        }

        return "{$directory}/{$uuid}.md";
    }

    /**
     * 获取 Markdown 内容的预览（前 N 个字符）
     */
    public function getMarkdownPreview(string $markdown, ?int $length = null): string
    {
        $length = $length ?? $this->previewLength;
        $cleaned = preg_replace('/\s+/', ' ', $markdown);
        $cleaned = trim($cleaned);

        if (mb_strlen($cleaned) <= $length) {
            return $cleaned;
        }

        return mb_substr($cleaned, 0, $length) . '...';
    }

    /**
     * 更新文档的 Markdown 信息
     */
    public function updateDocumentMarkdown(Document $document, string $markdownPath): void
    {
        $markdown = Storage::disk('markdown')->get($markdownPath);

        if ($markdown === false) {
            Log::warning('无法读取 Markdown 文件以生成预览', [
                'document_id' => $document->id,
                'markdown_path' => $markdownPath,
            ]);
        } else {
            $this->getMarkdownPreview($markdown);
        }

        Document::withoutSyncingToSearch(function () use ($document, $markdownPath): void {
            $document->update([
                'markdown_path' => $markdownPath,
                'conversion_status' => 'completed',
                'conversion_error' => null,
            ]);
        });
    }

    /**
     * 处理转换失败
     */
    public function handleConversionFailure(Document $document, \Exception $exception): void
    {
        Log::error('文档转换失败', [
            'document_id' => $document->id,
            'document_title' => $document->title,
            'file_name' => $document->file_name,
            'error' => $exception->getMessage(),
            'trace' => $exception->getTraceAsString(),
        ]);

        Document::withoutSyncingToSearch(function () use ($document, $exception): void {
            $document->update([
                'conversion_status' => 'failed',
                'conversion_error' => $exception->getMessage(),
            ]);
        });
    }

    /**
     * 将转换任务加入队列
     */
    public function queueConversion(Document $document): void
    {
        Document::withoutSyncingToSearch(function () use ($document): void {
            $document->update([
                'conversion_status' => 'processing',
                'conversion_error' => null,
            ]);
        });

        $queue = config('documents.conversion.queue', 'documents');
        \App\Jobs\ConvertDocumentToMarkdown::dispatch($document)->onQueue($queue);
    }

    /**
     * @return array<string, string>
     */
    protected function extractMarkdownMediaFiles(DocumentInterface $document): array
    {
        $mediaFiles = [];
        $fallbackIndex = 1;

        foreach ($document->getSections() as $section) {
            foreach ($section->getElements() as $element) {
                if (!$element instanceof Image || !$element->hasData()) {
                    continue;
                }

                $relativePath = $this->normalizeMarkdownMediaPath($element->getSrc());

                if ($relativePath === null) {
                    $relativePath = sprintf(
                        'media/image-%d.%s',
                        $fallbackIndex++,
                        $this->guessImageExtension($element)
                    );
                }

                $mediaFiles[$relativePath] = $element->getData();
            }
        }

        return $mediaFiles;
    }

    /**
     * @param array<string, string> $mediaFiles
     */
    protected function storeMarkdownMediaFiles(string $documentDir, array $mediaFiles): void
    {
        foreach ($mediaFiles as $relativePath => $contents) {
            $targetPath = $documentDir . '/' . ltrim($relativePath, '/');
            $targetDirectory = dirname($targetPath);

            if ($targetDirectory !== '.' && !Storage::disk('markdown')->exists($targetDirectory)) {
                Storage::disk('markdown')->makeDirectory($targetDirectory);
            }

            Storage::disk('markdown')->put($targetPath, $contents);
        }
    }

    protected function normalizeMarkdownMediaPath(string $path): ?string
    {
        $path = trim($path);
        if ($path === '') {
            return null;
        }

        if (str_contains($path, '://') || str_starts_with($path, 'data:')) {
            return null;
        }

        $path = preg_replace('/^\.?\//', '', $path) ?? $path;
        $path = str_replace('\\', '/', $path);
        $path = ltrim($path, '/');

        if ($path === '' || !str_starts_with($path, 'media/')) {
            return null;
        }

        $segments = array_values(array_filter(
            explode('/', $path),
            fn (string $segment): bool => $segment !== '' && $segment !== '.'
        ));

        if ($segments === []) {
            return null;
        }

        foreach ($segments as $segment) {
            if ($segment === '..') {
                return null;
            }
        }

        return implode('/', $segments);
    }

    protected function guessImageExtension(Image $image): string
    {
        return match ($image->getMimeType()) {
            'image/jpeg' => 'jpg',
            'image/png' => 'png',
            'image/gif' => 'gif',
            'image/webp' => 'webp',
            'image/bmp' => 'bmp',
            'image/tiff' => 'tiff',
            'image/svg+xml' => 'svg',
            default => pathinfo($image->getSrc(), PATHINFO_EXTENSION) ?: 'bin',
        };
    }
}