How do I download a generated csv in magento 2.4.5 - csv

Question

My files so far are:
system.xml
<field id="generate_csv" translate="label" type="button" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Generate Categories CSV</label>
<frontend_model>Vendor\Module\Block\Adminhtml\System\Config\Button</frontend_model>
</field>
button.php
<?php
namespace [Vendor]\[Module]\Block\Adminhtml\System\Config;
use Magento\Config\Block\System\Config\Form\Field;
use Magento\Backend\Block\Template\Context;
use Magento\Framework\Data\Form\Element\AbstractElement;
class Button extends Field
{
protected $_template = 'Vendor_Module::system/config/button.phtml';
public function __construct(
Context $context,
array $data = []
){
parent::__construct($context, $data);
}
public function render(AbstractElement $element)
{
$element->unsScope()->unsCanUseWebsiteValue()->unsCanUseDefaultValue();
return parent::render($element);
}
protected function _getElementHtml(AbstractElement $element)
{
return $this->_toHtml();
}
public function getAjaxUrl()
{
return $this->getUrl('[router]/Export/CategoryExport');
}
public function getButtonHtml()
{
$button = $this->getLayout()->createBlock(
'Magento\Backend\Block\Widget\Button'
)->setData(
[
'id' => 'generate_csv',
'label' => __('Generate CSV')
]
);
return $button->toHtml();
}
}
button.phtml
<script>
require([
'jquery',
'prototype'
], function ($) {
$('#generate_csv').click(function () {
var params = {};
new Ajax.Request('<?php echo $block->getAjaxUrl() ?>', {
parameters: params,
loaderArea: false,
asynchronous: true,
onCreate: function () {
$('#custom_button_response_message').text('');
},
onSuccess: function (transport) {
var resultText = '';
if (transport.status > 200) {
resultText = transport.statusText;
} else {
var response = JSON.parse(transport.responseText);
resultText = response.message
}
$('#generate_csv_response_message').text(resultText);
}
});
});
});
</script>
<?php echo $block->getButtonHtml(); ?>
<p>
<span id="generate_csv_response_message"></span>
</p>
controller
<?php
namespace [Vendor]\[Module]\Controller\Adminhtml\Export;
use Magento\Framework\App\Action\Action;
use Magento\Framework\App\Action\Context;
use Magento\Framework\Controller\Result\Json;
use Magento\Framework\Controller\Result\JsonFactory;
use Magento\Framework\Filesystem;
use Magento\Framework\App\Filesystem\DirectoryList;
use Magento\Catalog\Model\ResourceModel\Category\CollectionFactory;
use Magento\Catalog\Model\CategoryFactory;
class CategoryExport extends Action
{
protected $resultJsonFactory;
/**
* #param Context $context
* #param JsonFactory $resultJsonFactory
*/
public function __construct(
Context $context,
JsonFactory $resultJsonFactory,
Filesystem $filesystem,
DirectoryList $directoryList,
CollectionFactory $categoryCollectionFactory,
CategoryFactory $categoryFactory
){
$this->resultJsonFactory = $resultJsonFactory;
$this->filesystem = $filesystem;
$this->directory = $filesystem->getDirectoryWrite(DirectoryList::VAR_DIR);
$this->categoryCollectionFactory = $categoryCollectionFactory;
$this->categoryFactory = $categoryFactory;
parent::__construct($context);
}
/**
* #return Json
*/
public function execute()
{
$message = 'Success';
$data[] = [
'id' => __('Entity ID'),
'name' => __('Name'),
'level' => __('Level')
];
$categoryCollection = $this->categoryCollectionFactory->create();
$categoryCollection->addAttributeToSelect('*');
$filepath = 'export/customerlist.csv';
$this->directory->create('export');
$stream = $this->directory->openFile($filepath, 'w+');
$stream->lock();
$header = ['Id', 'Name', 'Level'];
$stream->writeCsv($header);
//$categoryArray = array();
foreach ($categoryCollection as $category) {
$data = [];
$data[] = $category->getId();
$data[] = $category->getName();
$data[] = $category->getLevel();
$stream->writeCsv($data);
}
/** #var Json $result */
$result = $this->resultJsonFactory->create();
return $result->setData(['message' => $message]);
}
}
This creates a csv file in var/export directory but I cannot download it
Can anyone help explain how to modify the code so that it will automatically create and down the csv.
I have tried following various examples on the web but none of them have worked.
Please help me out