Proses Kirim Invoice

private function process_invoice_simple($invoice_id)
    {
        try {
            // 1. CEK INVOICE DI DATABASE
            $invoice = $this->db->get_where('v_invoice', ['invoice_id' => $invoice_id])->row();
            if (!$invoice) {
                return ['success' => false, 'message' => 'Invoice tidak ditemukan'];
            }
            // Jika sudah ada invoice_jurnal_id, skip
            if (!empty($invoice->invoice_jurnal_id)) {
                return [
                    'success' => true,
                    'message' => 'Invoice sudah sync sebelumnya',
                    'skip' => true
                ];
            }

            // 2. CEK/SYNC CUSTOMER
            $customer_result = $this->sync_customer_simple($invoice);
            if (!$customer_result['success']) {
                return $customer_result;
            }

            $customer_jurnal_id = $customer_result['jurnal_id'];

            if (!empty($invoice->invoice_jurnal_id)) {
                // Cek apakah masih ada di Mekari
                $exists = $this->check_invoice_exists_in_mekari($invoice->invoice_jurnal_id);
                if ($exists) {
                    return ['success' => true, 'message' => 'Invoice sudah ada di Mekari', 'skip' => true];
                } else {
                    // Jurnal ID tidak valid di Mekari, reset
                    $this->db->where('invoice_id', $invoice->invoice_id)->update('sid_invoice', ['invoice_jurnal_id' => null]);
                }
            }

            // 4. KIRIM INVOICE KE MEKARI dan SET PAID
            return $this->send_invoice_simple($invoice, $customer_jurnal_id);

        } catch (Exception $e) {
            return ['success' => false, 'message' => 'Error: ' . $e->getMessage()];
        }
    }