<?php

namespace App\Services\Crawl;

use App\Models\CourseMedia;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Str;

/**
 * 将正文中的外链图片下载到本地 public 盘，避免 CDN 防盗链导致无法显示。
 */
class NewsHtmlImageLocalizer
{
    public function localize(?string $html, ?string $pageUrl = null): ?string
    {
        if ($html === null || trim($html) === '') {
            return $html;
        }

        $html = NewsContentHtml::normalize($html, $pageUrl);

        return preg_replace_callback(
            '/<img\b([^>]*)>/iu',
            function (array $m) use ($pageUrl): string {
                $attrs = $m[1];
                if (! preg_match('/\ssrc=(["\'])([^"\']+)\1/i', $attrs, $srcMatch)) {
                    return '<img'.$attrs.'>';
                }

                $src = NewsContentHtml::resolveAssetUrl($srcMatch[2], $pageUrl);
                $local = $this->downloadToPublic($src, $pageUrl);
                if ($local === null) {
                    $attrs = preg_replace(
                        '/\ssrc=(["\'])[^"\']*\1/i',
                        ' src="'.$src.'"',
                        $attrs
                    ) ?? $attrs;

                    return '<img'.$attrs.'>';
                }

                $attrs = preg_replace(
                    '/\ssrc=(["\'])[^"\']*\1/i',
                    ' src="'.$local.'"',
                    $attrs
                ) ?? $attrs;

                return '<img'.$attrs.'>';
            },
            $html
        ) ?? $html;
    }

    protected function downloadToPublic(string $url, ?string $pageUrl = null): ?string
    {
        $url = NewsContentHtml::resolveAssetUrl(trim($url), $pageUrl);
        if ($url === '' || ! preg_match('#^https?://#i', $url)) {
            return null;
        }

        if (Str::contains($url, ['/storage/', '127.0.0.1', 'localhost'])) {
            return null;
        }

        $headers = [
            'User-Agent' => 'Mozilla/5.0 (compatible; SlakeCrawler/1.0)',
            'Accept' => 'image/*,*/*',
        ];
        if ($pageUrl && preg_match('#^https?://#i', $pageUrl)) {
            $headers['Referer'] = $pageUrl;
        }

        try {
            $response = Http::timeout(25)
                ->withHeaders($headers)
                ->get($url);
        } catch (\Throwable) {
            return null;
        }

        if (! $response->successful()) {
            return null;
        }

        $body = $response->body();
        if ($body === '') {
            return null;
        }

        $ext = $this->guessExtension($url, $response->header('Content-Type'));
        $name = 'news/content/'.date('Ym').'/'.Str::random(16).'.'.$ext;

        Storage::disk('public')->put($name, $body);

        return CourseMedia::publicAssetUrl($name);
    }

    protected function guessExtension(string $url, ?string $contentType): string
    {
        if ($contentType) {
            if (str_contains($contentType, 'png')) {
                return 'png';
            }
            if (str_contains($contentType, 'jpeg') || str_contains($contentType, 'jpg')) {
                return 'jpg';
            }
            if (str_contains($contentType, 'gif')) {
                return 'gif';
            }
            if (str_contains($contentType, 'webp')) {
                return 'webp';
            }
        }

        if (preg_match('#\.(png|jpe?g|gif|webp)(\?|$)#i', $url, $m)) {
            return strtolower($m[1] === 'jpeg' ? 'jpg' : $m[1]);
        }

        return 'jpg';
    }
}