<?php
namespace Swissup\Orderattachment\Model;

use Magento\Framework\App\Filesystem\DirectoryList;
use Magento\Store\Model\ScopeInterface;
use Swissup\Orderattachment\Model\Attachment;

class Upload
{
/**
* @var \Magento\Framework\App\Config\ScopeConfigInterface
*/
protected $scopeConfig;

/**
* @var \Magento\MediaStorage\Model\File\UploaderFactory
*/
protected $uploaderFactory;

/**
* @var \Magento\Framework\Filesystem
*/
protected $fileSystem;

/**
* @param \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig
* @param \Magento\MediaStorage\Model\File\UploaderFactory $uploaderFactory
* @param \Magento\Framework\Filesystem $fileSystem
*/
public function __construct(
\Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
\Magento\MediaStorage\Model\File\UploaderFactory $uploaderFactory,
\Magento\Framework\Filesystem $fileSystem
) {
$this->scopeConfig = $scopeConfig;
$this->uploaderFactory = $uploaderFactory;
$this->fileSystem = $fileSystem;
}

/**
* @param array $uploadData
* @return array
*/
public function uploadFileAndGetInfo($uploadData)
{
$allowedExtensions = $this->scopeConfig->getValue(
Attachment::XML_PATH_ATTACHMENT_FILE_EXT,
ScopeInterface::SCOPE_STORE
);
$varDirectoryPath = $this->fileSystem
->getDirectoryRead(DirectoryList::VAR_DIR)
->getAbsolutePath("orderattachment");

$result = $this->uploaderFactory
->create(['fileId' => $uploadData])
->setAllowedExtensions(explode(',', $allowedExtensions))
->setAllowRenameFiles(true)
->setFilesDispersion(true)
->save($varDirectoryPath);

return $result;
}
}