opensourcepos/app/Models/Tokens/Token_invoice_count.php

<?php

namespace App\Models\Tokens;

use App\Models\Sale;

/**
 * Token_invoice_count class
 *
 * @property Sale sale
 */
class Token_invoice_count extends Token
{
    public function __construct(string $value = '')
    {
        parent::__construct($value);
    }

    public function token_id(): string
    {
        return 'CO';
    }

    public function get_value(): int
    {
        $sale = model(Sale::class);

        return empty($value) ? $sale->get_invoice_count() : $value;
    }
}