Selling Code Auto-generator

Observer that auto-generates sale transaction codes ('SELL0001' format), sets default date, associates user, and links to cash drawer.

<?php

namespace App\Observers;

use App\Models\Tenants\CashDrawer;
use App\Models\Tenants\Selling;
use App\Models\Tenants\Setting;
use Illuminate\Contracts\Validation\DataAwareRule;
use Illuminate\Support\Str;

class SellingObserver extends AbstractObserver implements DataAwareRule
{
    protected $data = [];

    public function setData($data)
    {
        $this->data = $data;

        return $this;
    }

    public function creating(Selling $selling)
    {
        if (! $selling->date) {
            $selling->date = now()->format('Y-m-d H:i:s');
        }
        $sellings = Selling::all();
        $lastCount = $sellings->count();
        /* TODO: fixing the iteration code <10-08-22, sheenazien8> */
        $selling->code = 'SELL'.Str::of($lastCount + 1)->padLeft(4, 0)->value();
     

... (truncated -- full source via MCP)