<?php

namespace App\Services\Course;

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

class RemoteCourseAssetImporter
{
    /**
     * 从远程 URL 下载图片到 public 盘并写入 course_media。
     *
     * @param  string|null  $referer  可选 Referer，部分 CDN 防盗链需要
     */
    public function importFromUrl(string $url, string $subdir, ?string $referer = null): CourseMedia
    {
        $url = trim($url);
        if ($url === '' || ! preg_match('#^https?://#i', $url)) {
            throw new RuntimeException('图片地址无效');
        }

        if (! in_array($subdir, ['covers', 'promos'], true)) {
            throw new RuntimeException('不支持的资源类型');
        }

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

        try {
            $response = Http::timeout(30)
                ->withHeaders($headers)
                ->get($url);
        } catch (\Throwable $e) {
            throw new RuntimeException('图片下载失败：'.$e->getMessage());
        }

        if (! $response->successful()) {
            throw new RuntimeException('图片下载失败，HTTP '.$response->status());
        }

        $body = $response->body();
        if ($body === '') {
            throw new RuntimeException('图片内容为空');
        }

        $contentType = $response->header('Content-Type');
        if ($contentType && ! str_contains(strtolower($contentType), 'image')) {
            throw new RuntimeException('远程资源不是图片');
        }

        $ext = $this->guessExtension($url, $contentType);
        $filename = basename(parse_url($url, PHP_URL_PATH) ?: '') ?: 'import';
        $filename = preg_replace('/[^a-zA-Z0-9._-]/', '_', $filename) ?: 'import';
        $filename = Str::limit($filename, 64, '');
        if (! preg_match('/\.(png|jpe?g|gif|webp)$/i', $filename)) {
            $filename .= '.'.$ext;
        }

        $path = 'courses/'.$subdir.'/'.date('Ym').'/'.Str::random(16).'_'.$filename;

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

        $publicUrl = CourseMedia::publicAssetUrl($path) ?? '';

        return CourseMedia::query()->create([
            'disk' => 'public',
            'path' => $path,
            'url' => $publicUrl,
            'category' => $subdir,
            'original_name' => $filename,
            'mime_type' => $this->guessMimeType($ext, $contentType),
            'size_bytes' => strlen($body),
        ]);
    }

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

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

        return 'jpg';
    }

    protected function guessMimeType(string $ext, ?string $contentType): ?string
    {
        if ($contentType && str_contains(strtolower($contentType), 'image')) {
            return strtok($contentType, ';') ?: null;
        }

        return match ($ext) {
            'png' => 'image/png',
            'jpg', 'jpeg' => 'image/jpeg',
            'gif' => 'image/gif',
            'webp' => 'image/webp',
            default => null,
        };
    }
}