// Add to your register_routes() function
    register_rest_route( 'hemjey-pos/v1', '/onboard-student', [
        'methods'             => 'POST',
        'callback'            => [ $this, 'onboard_student' ],
        'permission_callback' => [ $this, 'verify_pos_permissions' ],
    ] );

    /**
     * Fast Onboarding: Creates a WP user with Phone Number as Username
     */
    public function onboard_student( WP_REST_Request $request ) {
        $params =$request->get_json_params();
        $phone  = sanitize_text_field($params['phone'] );
        $name   = sanitize_text_field($params['name'] );
        $email  = sanitize_email($params['email'] );
        $ref    = sanitize_text_field($params['referrer_phone'] );

        if ( username_exists( $phone ) ) {
            return new WP_Error( 'exists', 'Student with this phone number already exists.', ['status' => 400] );
        }

        $user_id = wp_insert_user([
            'user_login'   => $phone,
            'user_pass'    => wp_generate_password( 12, false ),
            'user_email'   => $email,
            'display_name' => $name,
            'role'         => 'customer'
        ]);

        if ( is_wp_error( $user_id ) ) return$user_id;

        update_user_meta( $user_id, 'billing_phone',$phone );
        update_user_meta( $user_id, '_hemjey_wallet_balance', 0 );

        // Link referral if provided
        if ( ! empty( $ref ) ) {
            $referrer = get_users(['meta_key' => 'billing_phone', 'meta_value' =>$ref, 'number' => 1]);
            if ( ! empty( $referrer ) ) {
                update_user_meta( $user_id, '_referred_by_id',$referrer[0]->ID );
            }
        }

        return rest_ensure_response([
            'status'  => 'success',
            'user_id' => $user_id,
            'message' => 'Student onboarded successfully.'
        ]);
    }

    /**
     * Updated Core Transaction Logic (Call this inside your process_transaction method)
     * Handles the 3% cashback and 10% / 2% referral commissions automatically.
     */
    private function process_loyalty_and_commissions( $order, $customer_id,$wallet_deducted ) {
        $order_total =$order->get_total();
        
        // 1. Give 3% Cashback to the Buyer
        $cashback =$order_total * 0.03;
        $this->process_wallet_credits( $customer_id,$wallet_deducted, $cashback,$order->get_id() );
        $order->add_order_note( "Added ₦{$cashback} (3% cashback) to wallet." );

        // 2. Handle Referral Commissions
        $referrer_id = get_user_meta($customer_id, '_referred_by_id', true );
        if ( $referrer_id ) {
            // Check if this is the student's FIRST order
            $previous_orders = wc_get_orders([
                'customer_id' => $customer_id,
                'status'      => 'completed',
                'exclude'     => [ $order->get_id() ]
            ]);

            if ( empty( $previous_orders ) ) {
                // First order: 10% commission
                $commission =$order_total * 0.10;
                $note = "10% First-time referral commission";
            } else {
                // Subsequent orders: 2% commission
                $commission =$order_total * 0.02;
                $note = "2% Recurring referral commission";
            }

            $this->process_wallet_credits( $referrer_id, 0,$commission, $order->get_id() );$order->add_order_note( "Referrer (ID: {$referrer_id}) earned ₦{$commission} - {$note}." );
        }

        return $cashback; // Return earned amount to display on POS
    }

    /**
     * Send Custom Email Receipt with Attendant Name and Balances
     */
    private function send_student_receipt( $order, $customer_id,$attendant_name, $wallet_deducted,$cashback_earned ) {
        $user = get_userdata($customer_id );
        $new_balance = get_user_meta($customer_id, '_hemjey_wallet_balance', true );
        
        $to =$user->user_email;
        $subject = "Your Receipt - Hemjey Tech Campus Cafe";
        $message = "Hello {$user->display_name},\n\n";
        $message .= "Thank you for visiting Hemjey Tech Cafe today. You were attended to by: {$attendant_name}.\n\n";
        $message .= "Transaction Total: ₦" . $order->get_total() . "\n";
        
        if ( $wallet_deducted > 0 ) {$message .= "Paid via Wallet: ₦{$wallet_deducted}\n";
        }
        
        $message .= "Cashback Earned (3%): ₦{$cashback_earned}\n";
        $message .= "Current Wallet Balance: ₦{$new_balance}\n\n";
        $message .= "Note: Your wallet balance can be used at any Hemjey Tech branch on campus!\n";
        
        wp_mail( $to, $subject,$message );
    }