Initiator.php

<?php
 
namespace Bitrix\MessageService\Providers\Base;
 
abstract class Initiator implements \Bitrix\MessageService\Providers\Initiator
{
    public function getDefaultFrom(): ?string
    {
        $fromList = $this->getFromList();
        $from = isset($fromList[0]) ? $fromList[0]['id'] : null;
        //Try to find alphanumeric from
        foreach ($fromList as $item)
        {
            if (!preg_match('#^[0-9]+$#', $item['id']))
            {
                $from = $item['id'];
                break;
            }
        }
        return $from;
    }
 
    public function getFirstFromList()
    {
        $fromList = $this->getFromList();
        if (!is_array($fromList))
        {
            return null;
        }
 
        foreach ($fromList as $item)
        {
            if (isset($item['id']) && $item['id'])
            {
                return $item['id'];
            }
        }
 
        return null;
    }
 
    public function isCorrectFrom($from): bool
    {
        $fromList = $this->getFromList();
        foreach ($fromList as $item)
        {
            if ($from === $item['id'])
            {
                return true;
            }
        }
        return false;
    }
}