Part-DB.Part-DB-server/src/Services/Attachments/PartPreviewGenerator.php

<?php
/**
 *
 * part-db version 0.1
 * Copyright (C) 2005 Christoph Lechner
 * http://www.cl-projects.de/
 *
 * part-db version 0.2+
 * Copyright (C) 2009 K. Jacobs and others (see authors.php)
 * http://code.google.com/p/part-db/
 *
 * Part-DB Version 0.4+
 * Copyright (C) 2016 - 2019 Jan Böhmer
 * https://github.com/jbtronics
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 *
 */

namespace App\Services\Attachments;


use App\Entity\Attachments\Attachment;
use App\Entity\Parts\Part;
use App\Services\AttachmentHelper;

/**
 * @package App\Services\Attachments
 */
class PartPreviewGenerator
{
    protected $attachmentHelper;

    public function __construct(AttachmentHelper $attachmentHelper)
    {
        $this->attachmentHelper = $attachmentHelper;
    }

    /**
     * Determines what attachment should be used for previewing a part (especially in part table).
     * The returned attachment is guaranteed to be existing and be a picture.
     * @param Part $part The part for which the attachment should be determined
     * @return Attachment|null
     */
    public function previewAttachment(Part $part) : ?Attachment
    {
        //First of all we check if the master attachment of the part is set (and a picture)
        $attachment = $part->getMasterPictureAttachment();
        if ($this->isAttachmentValidPicture($attachment)) {
            return $attachment;
        }

        //Otherwise check if the part has a footprint with a valid masterattachment
        if ($part->getFootprint() !== null) {
            $attachment = $part->getFootprint()->getMasterPictureAttachment();
            if ($this->isAttachmentValidPicture($attachment)) {
                return $attachment;
            }
        }

        //If nothing is available return null
        return null;
    }

    /**
     * Checks if a attachment is exising and a valid picture.
     * @param Attachment|null $attachment The attachment that should be checked.
     * @return bool True if the attachment is valid.
     */
    protected function isAttachmentValidPicture(?Attachment $attachment) : bool
    {
        return $attachment !== null
            && $attachment->isPicture()
            && $this->attachmentHelper->isFileExisting($attachment);
    }
}