App\Http\Controllers\InvoiceController::emailRecurringInvoice PHP Method

    private function emailRecurringInvoice(&$invoice)
    {
        if (!$invoice->shouldSendToday()) {
            if ($date = $invoice->getNextSendDate()) {
                $date = $invoice->account->formatDate($date);
                $date .= ' ' . DEFAULT_SEND_RECURRING_HOUR . ':00 am ' . $invoice->account->getTimezone();
                return trans('texts.recurring_too_soon', ['date' => $date]);
            } else {
                return trans('texts.no_longer_running');
            }
        }
        // switch from the recurring invoice to the generated invoice
        $invoice = $this->invoiceRepo->createRecurringInvoice($invoice);
        // in case auto-bill is enabled then a receipt has been sent
        if ($invoice->isPaid()) {
            return true;
        } else {
            return $this->mailer->sendInvoice($invoice);
        }
    }