slake-school-service/app/Models/CourseMedia.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;
use Illuminate\Support\Facades\URL;

class CourseMedia extends Model
{
    protected $table = 'course_media';

    protected $fillable = [
        'disk',
        'path',
        'url',
        'category',
        'original_name',
        'mime_type',
        'size_bytes',
    ];

    protected $casts = [
        'size_bytes' => 'integer',
    ];

    public function coursesAsCover(): HasMany
    {
        return $this->hasMany(Course::class, 'cover_media_id');
    }

    public function coursesAsPromo(): HasMany
    {
        return $this->hasMany(Course::class, 'promo_media_id');
    }

    /** public 磁盘下文件的浏览器绝对地址（与 APP_URL / ASSET_URL 一致，SPA 可从任意端口加载） */
    public static function publicAssetUrl(?string $pathRelativeToPublicDisk): ?string
    {
        if ($pathRelativeToPublicDisk === null || $pathRelativeToPublicDisk === '') {
            return null;
        }

        $trimmed = ltrim($pathRelativeToPublicDisk, '/');

        return URL::asset('storage/'.$trimmed);
    }

    /**
     * @return array<string, mixed>
     */
    public function toApiArray(): array
    {
        $resolvedUrl = self::publicAssetUrl($this->path);
        $legacy = $this->attributes['url'] ?? '';

        return [
            'id' => $this->id,
            'disk' => $this->disk,
            'path' => $this->path,
            'url' => $resolvedUrl ?? (string) $legacy,
            'category' => $this->category,
            'original_name' => $this->original_name,
            'mime_type' => $this->mime_type,
            'size_bytes' => $this->size_bytes,
            'created_at' => $this->created_at?->toIso8601String(),
        ];
    }
}