eventespresso / event-espresso-core

core/db_classes/EE_Registration.class.php

Indentation +2068 added lines, -2068 removed lines

@@ -17,2072 +17,2072 @@
 {
 
 
-    /**
-     * Used to reference when a registration has never been checked in.
-     *
-     * @deprecated use \EE_Checkin::status_checked_never instead
-     * @type int
-     */
-    const checkin_status_never = 2;
-
-    /**
-     * Used to reference when a registration has been checked in.
-     *
-     * @deprecated use \EE_Checkin::status_checked_in instead
-     * @type int
-     */
-    const checkin_status_in = 1;
-
-
-    /**
-     * Used to reference when a registration has been checked out.
-     *
-     * @deprecated use \EE_Checkin::status_checked_out instead
-     * @type int
-     */
-    const checkin_status_out = 0;
-
-
-    /**
-     * extra meta key for tracking reg status os trashed registrations
-     *
-     * @type string
-     */
-    const PRE_TRASH_REG_STATUS_KEY = 'pre_trash_registration_status';
-
-
-    /**
-     * extra meta key for tracking if registration has reserved ticket
-     *
-     * @type string
-     */
-    const HAS_RESERVED_TICKET_KEY = 'has_reserved_ticket';
-
-
-    /**
-     * @param array  $props_n_values          incoming values
-     * @param string $timezone                incoming timezone (if not set the timezone set for the website will be
-     *                                        used.)
-     * @param array  $date_formats            incoming date_formats in an array where the first value is the
-     *                                        date_format and the second value is the time format
-     * @return EE_Registration
-     * @throws EE_Error
-     */
-    public static function new_instance($props_n_values = array(), $timezone = null, $date_formats = array())
-    {
-        $has_object = parent::_check_for_object($props_n_values, __CLASS__, $timezone, $date_formats);
-        return $has_object ? $has_object : new self($props_n_values, false, $timezone, $date_formats);
-    }
-
-
-    /**
-     * @param array  $props_n_values  incoming values from the database
-     * @param string $timezone        incoming timezone as set by the model.  If not set the timezone for
-     *                                the website will be used.
-     * @return EE_Registration
-     */
-    public static function new_instance_from_db($props_n_values = array(), $timezone = null)
-    {
-        return new self($props_n_values, true, $timezone);
-    }
-
-
-    /**
-     *        Set Event ID
-     *
-     * @param        int $EVT_ID Event ID
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_event($EVT_ID = 0)
-    {
-        $this->set('EVT_ID', $EVT_ID);
-    }
-
-
-    /**
-     * Overrides parent set() method so that all calls to set( 'REG_code', $REG_code ) OR set( 'STS_ID', $STS_ID ) can
-     * be routed to internal methods
-     *
-     * @param string $field_name
-     * @param mixed  $field_value
-     * @param bool   $use_default
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws RuntimeException
-     */
-    public function set($field_name, $field_value, $use_default = false)
-    {
-        switch ($field_name) {
-            case 'REG_code':
-                if (! empty($field_value) && $this->reg_code() === null) {
-                    $this->set_reg_code($field_value, $use_default);
-                }
-                break;
-            case 'STS_ID':
-                $this->set_status($field_value, $use_default);
-                break;
-            default:
-                parent::set($field_name, $field_value, $use_default);
-        }
-    }
-
-
-    /**
-     * Set Status ID
-     * updates the registration status and ALSO...
-     * calls reserve_registration_space() if the reg status changes TO approved from any other reg status
-     * calls release_registration_space() if the reg status changes FROM approved to any other reg status
-     *
-     * @param string                $new_STS_ID
-     * @param boolean               $use_default
-     * @param ContextInterface|null $context
-     * @return bool
-     * @throws DomainException
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws RuntimeException
-     * @throws UnexpectedEntityException
-     */
-    public function set_status($new_STS_ID = null, $use_default = false, ContextInterface $context = null)
-    {
-        // get current REG_Status
-        $old_STS_ID = $this->status_ID();
-        // if status has changed
-        if ($old_STS_ID !== $new_STS_ID // and that status has actually changed
-            && ! empty($old_STS_ID) // and that old status is actually set
-            && ! empty($new_STS_ID) // as well as the new status
-            && $this->ID() // ensure registration is in the db
-        ) {
-            // update internal status first
-            parent::set('STS_ID', $new_STS_ID, $use_default);
-            // THEN handle other changes that occur when reg status changes
-            // TO approved
-            if ($new_STS_ID === EEM_Registration::status_id_approved) {
-                // reserve a space by incrementing ticket and datetime sold values
-                $this->reserveRegistrationSpace();
-                do_action('AHEE__EE_Registration__set_status__to_approved', $this, $old_STS_ID, $new_STS_ID, $context);
-                // OR FROM  approved
-            } elseif ($old_STS_ID === EEM_Registration::status_id_approved) {
-                // release a space by decrementing ticket and datetime sold values
-                $this->releaseRegistrationSpace();
-                do_action(
-                    'AHEE__EE_Registration__set_status__from_approved',
-                    $this,
-                    $old_STS_ID,
-                    $new_STS_ID,
-                    $context
-                );
-            }
-            // update status
-            parent::set('STS_ID', $new_STS_ID, $use_default);
-            $this->updateIfCanceledOrReinstated($new_STS_ID, $old_STS_ID, $context);
-            if ($this->statusChangeUpdatesTransaction($context)) {
-                $this->updateTransactionAfterStatusChange();
-            }
-            do_action('AHEE__EE_Registration__set_status__after_update', $this, $old_STS_ID, $new_STS_ID, $context);
-            return true;
-        }
-        // even though the old value matches the new value, it's still good to
-        // allow the parent set method to have a say
-        parent::set('STS_ID', $new_STS_ID, $use_default);
-        return true;
-    }
-
-
-    /**
-     * update REGs and TXN when cancelled or declined registrations involved
-     *
-     * @param string                $new_STS_ID
-     * @param string                $old_STS_ID
-     * @param ContextInterface|null $context
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws RuntimeException
-     */
-    private function updateIfCanceledOrReinstated($new_STS_ID, $old_STS_ID, ContextInterface $context = null)
-    {
-        // these reg statuses should not be considered in any calculations involving monies owing
-        $closed_reg_statuses = EEM_Registration::closed_reg_statuses();
-        // true if registration has been cancelled or declined
-        $this->updateIfCanceled(
-            $closed_reg_statuses,
-            $new_STS_ID,
-            $old_STS_ID,
-            $context
-        );
-        $this->updateIfReinstated(
-            $closed_reg_statuses,
-            $new_STS_ID,
-            $old_STS_ID,
-            $context
-        );
-    }
-
-
-    /**
-     * update REGs and TXN when cancelled or declined registrations involved
-     *
-     * @param array                 $closed_reg_statuses
-     * @param string                $new_STS_ID
-     * @param string                $old_STS_ID
-     * @param ContextInterface|null $context
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws RuntimeException
-     */
-    private function updateIfCanceled(
-        array $closed_reg_statuses,
-        $new_STS_ID,
-        $old_STS_ID,
-        ContextInterface $context = null
-    ) {
-        // true if registration has been cancelled or declined
-        if (in_array($new_STS_ID, $closed_reg_statuses, true)
-            && ! in_array($old_STS_ID, $closed_reg_statuses, true)
-        ) {
-            /** @type EE_Registration_Processor $registration_processor */
-            $registration_processor = EE_Registry::instance()->load_class('Registration_Processor');
-            /** @type EE_Transaction_Processor $transaction_processor */
-            $transaction_processor = EE_Registry::instance()->load_class('Transaction_Processor');
-            // cancelled or declined registration
-            $registration_processor->update_registration_after_being_canceled_or_declined(
-                $this,
-                $closed_reg_statuses
-            );
-            $transaction_processor->update_transaction_after_canceled_or_declined_registration(
-                $this,
-                $closed_reg_statuses,
-                false
-            );
-            do_action(
-                'AHEE__EE_Registration__set_status__canceled_or_declined',
-                $this,
-                $old_STS_ID,
-                $new_STS_ID,
-                $context
-            );
-            return;
-        }
-    }
-
-
-    /**
-     * update REGs and TXN when cancelled or declined registrations involved
-     *
-     * @param array                 $closed_reg_statuses
-     * @param string                $new_STS_ID
-     * @param string                $old_STS_ID
-     * @param ContextInterface|null $context
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    private function updateIfReinstated(
-        array $closed_reg_statuses,
-        $new_STS_ID,
-        $old_STS_ID,
-        ContextInterface $context = null
-    ) {
-        // true if reinstating cancelled or declined registration
-        if (in_array($old_STS_ID, $closed_reg_statuses, true)
-            && ! in_array($new_STS_ID, $closed_reg_statuses, true)
-        ) {
-            /** @type EE_Registration_Processor $registration_processor */
-            $registration_processor = EE_Registry::instance()->load_class('Registration_Processor');
-            /** @type EE_Transaction_Processor $transaction_processor */
-            $transaction_processor = EE_Registry::instance()->load_class('Transaction_Processor');
-            // reinstating cancelled or declined registration
-            $registration_processor->update_canceled_or_declined_registration_after_being_reinstated(
-                $this,
-                $closed_reg_statuses
-            );
-            $transaction_processor->update_transaction_after_reinstating_canceled_registration(
-                $this,
-                $closed_reg_statuses,
-                false
-            );
-            do_action(
-                'AHEE__EE_Registration__set_status__after_reinstated',
-                $this,
-                $old_STS_ID,
-                $new_STS_ID,
-                $context
-            );
-        }
-    }
-
-
-    /**
-     * @param ContextInterface|null $context
-     * @return bool
-     */
-    private function statusChangeUpdatesTransaction(ContextInterface $context = null)
-    {
-        $contexts_that_do_not_update_transaction = (array) apply_filters(
-            'AHEE__EE_Registration__statusChangeUpdatesTransaction__contexts_that_do_not_update_transaction',
-            array('spco_reg_step_attendee_information_process_registrations'),
-            $context,
-            $this
-        );
-        return ! (
-            $context instanceof ContextInterface
-            && in_array($context->slug(), $contexts_that_do_not_update_transaction, true)
-        );
-    }
-
-
-    /**
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws RuntimeException
-     */
-    private function updateTransactionAfterStatusChange()
-    {
-        /** @type EE_Transaction_Payments $transaction_payments */
-        $transaction_payments = EE_Registry::instance()->load_class('Transaction_Payments');
-        $transaction_payments->recalculate_transaction_total($this->transaction(), false);
-        $this->transaction()->update_status_based_on_total_paid(true);
-    }
-
-
-    /**
-     *        get Status ID
-     */
-    public function status_ID()
-    {
-        return $this->get('STS_ID');
-    }
-
-
-    /**
-     * Gets the ticket this registration is for
-     *
-     * @param boolean $include_archived whether to include archived tickets or not.
-     *
-     * @return EE_Ticket|EE_Base_Class
-     * @throws EE_Error
-     */
-    public function ticket($include_archived = true)
-    {
-        $query_params = array();
-        if ($include_archived) {
-            $query_params['default_where_conditions'] = 'none';
-        }
-        return $this->get_first_related('Ticket', $query_params);
-    }
-
-
-    /**
-     * Gets the event this registration is for
-     *
-     * @return EE_Event
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     */
-    public function event()
-    {
-        $event = $this->get_first_related('Event');
-        if (! $event instanceof \EE_Event) {
-            throw new EntityNotFoundException('Event ID', $this->event_ID());
-        }
-        return $event;
-    }
-
-
-    /**
-     * Gets the "author" of the registration.  Note that for the purposes of registrations, the author will correspond
-     * with the author of the event this registration is for.
-     *
-     * @since 4.5.0
-     * @return int
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     */
-    public function wp_user()
-    {
-        $event = $this->event();
-        if ($event instanceof EE_Event) {
-            return $event->wp_user();
-        }
-        return 0;
-    }
-
-
-    /**
-     * increments this registration's related ticket sold and corresponding datetime sold values
-     *
-     * @return void
-     * @throws DomainException
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws UnexpectedEntityException
-     */
-    private function reserveRegistrationSpace()
-    {
-        // reserved ticket and datetime counts will be decremented as sold counts are incremented
-        // so stop tracking that this reg has a ticket reserved
-        $this->release_reserved_ticket(false, "REG: {$this->ID()} (ln:" . __LINE__ . ')');
-        $ticket = $this->ticket();
-        $ticket->increaseSold();
-        // possibly set event status to sold out
-        $this->event()->perform_sold_out_status_check();
-    }
-
-
-    /**
-     * decrements (subtracts) this registration's related ticket sold and corresponding datetime sold values
-     *
-     * @return void
-     * @throws DomainException
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws UnexpectedEntityException
-     */
-    private function releaseRegistrationSpace()
-    {
-        $ticket = $this->ticket();
-        $ticket->decreaseSold();
-        // possibly change event status from sold out back to previous status
-        $this->event()->perform_sold_out_status_check();
-    }
-
-
-    /**
-     * tracks this registration's ticket reservation in extra meta
-     * and can increment related ticket reserved and corresponding datetime reserved values
-     *
-     * @param bool $update_ticket if true, will increment ticket and datetime reserved count
-     * @return void
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public function reserve_ticket($update_ticket = false, $source = 'unknown')
-    {
-        // only reserve ticket if space is not currently reserved
-        if ((bool) $this->get_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, true) !== true) {
-            $this->update_extra_meta('reserve_ticket', "{$this->ticket_ID()} from {$source}");
-            // IMPORTANT !!!
-            // although checking $update_ticket first would be more efficient,
-            // we NEED to ALWAYS call update_extra_meta(), which is why that is done first
-            if ($this->update_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, true)
-                && $update_ticket
-            ) {
-                $ticket = $this->ticket();
-                $ticket->increaseReserved(1, "REG: {$this->ID()} (ln:" . __LINE__ . ')');
-                $ticket->save();
-            }
-        }
-    }
-
-
-    /**
-     * stops tracking this registration's ticket reservation in extra meta
-     * decrements (subtracts) related ticket reserved and corresponding datetime reserved values
-     *
-     * @param bool $update_ticket if true, will decrement ticket and datetime reserved count
-     * @return void
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public function release_reserved_ticket($update_ticket = false, $source = 'unknown')
-    {
-        // only release ticket if space is currently reserved
-        if ((bool) $this->get_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, true) === true) {
-            $this->update_extra_meta('release_reserved_ticket', "{$this->ticket_ID()} from {$source}");
-            // IMPORTANT !!!
-            // although checking $update_ticket first would be more efficient,
-            // we NEED to ALWAYS call update_extra_meta(), which is why that is done first
-            if ($this->update_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, false)
-                && $update_ticket
-            ) {
-                $ticket = $this->ticket();
-                $ticket->decreaseReserved(1, true, "REG: {$this->ID()} (ln:" . __LINE__ . ')');
-            }
-        }
-    }
-
-
-    /**
-     * Set Attendee ID
-     *
-     * @param        int $ATT_ID Attendee ID
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_attendee_id($ATT_ID = 0)
-    {
-        $this->set('ATT_ID', $ATT_ID);
-    }
-
-
-    /**
-     *        Set Transaction ID
-     *
-     * @param        int $TXN_ID Transaction ID
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_transaction_id($TXN_ID = 0)
-    {
-        $this->set('TXN_ID', $TXN_ID);
-    }
-
-
-    /**
-     *        Set Session
-     *
-     * @param    string $REG_session PHP Session ID
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_session($REG_session = '')
-    {
-        $this->set('REG_session', $REG_session);
-    }
-
-
-    /**
-     *        Set Registration URL Link
-     *
-     * @param    string $REG_url_link Registration URL Link
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_reg_url_link($REG_url_link = '')
-    {
-        $this->set('REG_url_link', $REG_url_link);
-    }
-
-
-    /**
-     *        Set Attendee Counter
-     *
-     * @param        int $REG_count Primary Attendee
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_count($REG_count = 1)
-    {
-        $this->set('REG_count', $REG_count);
-    }
-
-
-    /**
-     *        Set Group Size
-     *
-     * @param        boolean $REG_group_size Group Registration
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_group_size($REG_group_size = false)
-    {
-        $this->set('REG_group_size', $REG_group_size);
-    }
-
-
-    /**
-     *    is_not_approved -  convenience method that returns TRUE if REG status ID ==
-     *    EEM_Registration::status_id_not_approved
-     *
-     * @return        boolean
-     */
-    public function is_not_approved()
-    {
-        return $this->status_ID() == EEM_Registration::status_id_not_approved ? true : false;
-    }
-
-
-    /**
-     *    is_pending_payment -  convenience method that returns TRUE if REG status ID ==
-     *    EEM_Registration::status_id_pending_payment
-     *
-     * @return        boolean
-     */
-    public function is_pending_payment()
-    {
-        return $this->status_ID() == EEM_Registration::status_id_pending_payment ? true : false;
-    }
-
-
-    /**
-     *    is_approved -  convenience method that returns TRUE if REG status ID == EEM_Registration::status_id_approved
-     *
-     * @return        boolean
-     */
-    public function is_approved()
-    {
-        return $this->status_ID() == EEM_Registration::status_id_approved ? true : false;
-    }
-
-
-    /**
-     *    is_cancelled -  convenience method that returns TRUE if REG status ID == EEM_Registration::status_id_cancelled
-     *
-     * @return        boolean
-     */
-    public function is_cancelled()
-    {
-        return $this->status_ID() == EEM_Registration::status_id_cancelled ? true : false;
-    }
-
-
-    /**
-     *    is_declined -  convenience method that returns TRUE if REG status ID == EEM_Registration::status_id_declined
-     *
-     * @return        boolean
-     */
-    public function is_declined()
-    {
-        return $this->status_ID() == EEM_Registration::status_id_declined ? true : false;
-    }
-
-
-    /**
-     *    is_incomplete -  convenience method that returns TRUE if REG status ID ==
-     *    EEM_Registration::status_id_incomplete
-     *
-     * @return        boolean
-     */
-    public function is_incomplete()
-    {
-        return $this->status_ID() == EEM_Registration::status_id_incomplete ? true : false;
-    }
-
-
-    /**
-     *        Set Registration Date
-     *
-     * @param        mixed ( int or string ) $REG_date Registration Date - Unix timestamp or string representation of
-     *                                                 Date
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_reg_date($REG_date = false)
-    {
-        $this->set('REG_date', $REG_date);
-    }
-
-
-    /**
-     *    Set final price owing for this registration after all ticket/price modifications
-     *
-     * @access    public
-     * @param    float $REG_final_price
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_final_price($REG_final_price = 0.00)
-    {
-        $this->set('REG_final_price', $REG_final_price);
-    }
-
-
-    /**
-     *    Set amount paid towards this registration's final price
-     *
-     * @access    public
-     * @param    float $REG_paid
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_paid($REG_paid = 0.00)
-    {
-        $this->set('REG_paid', $REG_paid);
-    }
-
-
-    /**
-     *        Attendee Is Going
-     *
-     * @param        boolean $REG_att_is_going Attendee Is Going
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_att_is_going($REG_att_is_going = false)
-    {
-        $this->set('REG_att_is_going', $REG_att_is_going);
-    }
-
-
-    /**
-     * Gets the related attendee
-     *
-     * @return EE_Attendee
-     * @throws EE_Error
-     */
-    public function attendee()
-    {
-        return $this->get_first_related('Attendee');
-    }
-
-
-    /**
-     *        get Event ID
-     */
-    public function event_ID()
-    {
-        return $this->get('EVT_ID');
-    }
-
-
-    /**
-     *        get Event ID
-     */
-    public function event_name()
-    {
-        $event = $this->event_obj();
-        if ($event) {
-            return $event->name();
-        } else {
-            return null;
-        }
-    }
-
-
-    /**
-     * Fetches the event this registration is for
-     *
-     * @return EE_Event
-     * @throws EE_Error
-     */
-    public function event_obj()
-    {
-        return $this->get_first_related('Event');
-    }
-
-
-    /**
-     *        get Attendee ID
-     */
-    public function attendee_ID()
-    {
-        return $this->get('ATT_ID');
-    }
-
-
-    /**
-     *        get PHP Session ID
-     */
-    public function session_ID()
-    {
-        return $this->get('REG_session');
-    }
-
-
-    /**
-     * Gets the string which represents the URL trigger for the receipt template in the message template system.
-     *
-     * @param string $messenger 'pdf' or 'html'.  Default 'html'.
-     * @return string
-     */
-    public function receipt_url($messenger = 'html')
-    {
-
-        /**
-         * The below will be deprecated one version after this.  We check first if there is a custom receipt template
-         * already in use on old system.  If there is then we just return the standard url for it.
-         *
-         * @since 4.5.0
-         */
-        $template_relative_path = 'modules/gateways/Invoice/lib/templates/receipt_body.template.php';
-        $has_custom = EEH_Template::locate_template(
-            $template_relative_path,
-            array(),
-            true,
-            true,
-            true
-        );
-
-        if ($has_custom) {
-            return add_query_arg(array('receipt' => 'true'), $this->invoice_url('launch'));
-        }
-        return apply_filters('FHEE__EE_Registration__receipt_url__receipt_url', '', $this, $messenger, 'receipt');
-    }
-
-
-    /**
-     * Gets the string which represents the URL trigger for the invoice template in the message template system.
-     *
-     * @param string $messenger 'pdf' or 'html'.  Default 'html'.
-     * @return string
-     * @throws EE_Error
-     */
-    public function invoice_url($messenger = 'html')
-    {
-        /**
-         * The below will be deprecated one version after this.  We check first if there is a custom invoice template
-         * already in use on old system.  If there is then we just return the standard url for it.
-         *
-         * @since 4.5.0
-         */
-        $template_relative_path = 'modules/gateways/Invoice/lib/templates/invoice_body.template.php';
-        $has_custom = EEH_Template::locate_template(
-            $template_relative_path,
-            array(),
-            true,
-            true,
-            true
-        );
-
-        if ($has_custom) {
-            if ($messenger == 'html') {
-                return $this->invoice_url('launch');
-            }
-            $route = $messenger == 'download' || $messenger == 'pdf' ? 'download_invoice' : 'launch_invoice';
-
-            $query_args = array('ee' => $route, 'id' => $this->reg_url_link());
-            if ($messenger == 'html') {
-                $query_args['html'] = true;
-            }
-            return add_query_arg($query_args, get_permalink(EE_Registry::instance()->CFG->core->thank_you_page_id));
-        }
-        return apply_filters('FHEE__EE_Registration__invoice_url__invoice_url', '', $this, $messenger, 'invoice');
-    }
-
-
-    /**
-     * get Registration URL Link
-     *
-     * @access public
-     * @return string
-     * @throws EE_Error
-     */
-    public function reg_url_link()
-    {
-        return (string) $this->get('REG_url_link');
-    }
-
-
-    /**
-     * Echoes out invoice_url()
-     *
-     * @param string $type 'download','launch', or 'html' (default is 'launch')
-     * @return void
-     * @throws EE_Error
-     */
-    public function e_invoice_url($type = 'launch')
-    {
-        echo $this->invoice_url($type);
-    }
-
-
-    /**
-     * Echoes out payment_overview_url
-     */
-    public function e_payment_overview_url()
-    {
-        echo $this->payment_overview_url();
-    }
-
-
-    /**
-     * Gets the URL for the checkout payment options reg step
-     * with this registration's REG_url_link added as a query parameter
-     *
-     * @param bool $clear_session Set to true when you want to clear the session on revisiting the
-     *                            payment overview url.
-     * @return string
-     * @throws InvalidInterfaceException
-     * @throws InvalidDataTypeException
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     */
-    public function payment_overview_url($clear_session = false)
-    {
-        return add_query_arg(
-            (array) apply_filters(
-                'FHEE__EE_Registration__payment_overview_url__query_args',
-                array(
-                    'e_reg_url_link' => $this->reg_url_link(),
-                    'step'           => 'payment_options',
-                    'revisit'        => true,
-                    'clear_session'  => (bool) $clear_session,
-                ),
-                $this
-            ),
-            EE_Registry::instance()->CFG->core->reg_page_url()
-        );
-    }
-
-
-    /**
-     * Gets the URL for the checkout attendee information reg step
-     * with this registration's REG_url_link added as a query parameter
-     *
-     * @return string
-     * @throws InvalidInterfaceException
-     * @throws InvalidDataTypeException
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     */
-    public function edit_attendee_information_url()
-    {
-        return add_query_arg(
-            (array) apply_filters(
-                'FHEE__EE_Registration__edit_attendee_information_url__query_args',
-                array(
-                    'e_reg_url_link' => $this->reg_url_link(),
-                    'step'           => 'attendee_information',
-                    'revisit'        => true,
-                ),
-                $this
-            ),
-            EE_Registry::instance()->CFG->core->reg_page_url()
-        );
-    }
-
-
-    /**
-     * Simply generates and returns the appropriate admin_url link to edit this registration
-     *
-     * @return string
-     * @throws EE_Error
-     */
-    public function get_admin_edit_url()
-    {
-        return EEH_URL::add_query_args_and_nonce(
-            array(
-                'page'    => 'espresso_registrations',
-                'action'  => 'view_registration',
-                '_REG_ID' => $this->ID(),
-            ),
-            admin_url('admin.php')
-        );
-    }
-
-
-    /**
-     *    is_primary_registrant?
-     */
-    public function is_primary_registrant()
-    {
-        return $this->get('REG_count') === 1 ? true : false;
-    }
-
-
-    /**
-     * This returns the primary registration object for this registration group (which may be this object).
-     *
-     * @return EE_Registration
-     * @throws EE_Error
-     */
-    public function get_primary_registration()
-    {
-        if ($this->is_primary_registrant()) {
-            return $this;
-        }
-
-        // k reg_count !== 1 so let's get the EE_Registration object matching this txn_id and reg_count == 1
-        /** @var EE_Registration $primary_registrant */
-        $primary_registrant = EEM_Registration::instance()->get_one(
-            array(
-                array(
-                    'TXN_ID'    => $this->transaction_ID(),
-                    'REG_count' => 1,
-                ),
-            )
-        );
-        return $primary_registrant;
-    }
-
-
-    /**
-     *        get  Attendee Number
-     *
-     * @access        public
-     */
-    public function count()
-    {
-        return $this->get('REG_count');
-    }
-
-
-    /**
-     *        get Group Size
-     */
-    public function group_size()
-    {
-        return $this->get('REG_group_size');
-    }
-
-
-    /**
-     *        get Registration Date
-     */
-    public function date()
-    {
-        return $this->get('REG_date');
-    }
-
-
-    /**
-     * gets a pretty date
-     *
-     * @param string $date_format
-     * @param string $time_format
-     * @return string
-     * @throws EE_Error
-     */
-    public function pretty_date($date_format = null, $time_format = null)
-    {
-        return $this->get_datetime('REG_date', $date_format, $time_format);
-    }
-
-
-    /**
-     * final_price
-     * the registration's share of the transaction total, so that the
-     * sum of all the transaction's REG_final_prices equal the transaction's total
-     *
-     * @return float
-     * @throws EE_Error
-     */
-    public function final_price()
-    {
-        return $this->get('REG_final_price');
-    }
-
-
-    /**
-     * pretty_final_price
-     *  final price as formatted string, with correct decimal places and currency symbol
-     *
-     * @return string
-     * @throws EE_Error
-     */
-    public function pretty_final_price()
-    {
-        return $this->get_pretty('REG_final_price');
-    }
-
-
-    /**
-     * get paid (yeah)
-     *
-     * @return float
-     * @throws EE_Error
-     */
-    public function paid()
-    {
-        return $this->get('REG_paid');
-    }
-
-
-    /**
-     * pretty_paid
-     *
-     * @return float
-     * @throws EE_Error
-     */
-    public function pretty_paid()
-    {
-        return $this->get_pretty('REG_paid');
-    }
-
-
-    /**
-     * owes_monies_and_can_pay
-     * whether or not this registration has monies owing and it's' status allows payment
-     *
-     * @param array $requires_payment
-     * @return bool
-     * @throws EE_Error
-     */
-    public function owes_monies_and_can_pay($requires_payment = array())
-    {
-        // these reg statuses require payment (if event is not free)
-        $requires_payment = ! empty($requires_payment)
-            ? $requires_payment
-            : EEM_Registration::reg_statuses_that_allow_payment();
-        if (in_array($this->status_ID(), $requires_payment) &&
-            $this->final_price() != 0 &&
-            $this->final_price() != $this->paid()
-        ) {
-            return true;
-        } else {
-            return false;
-        }
-    }
-
-
-    /**
-     * Prints out the return value of $this->pretty_status()
-     *
-     * @param bool $show_icons
-     * @return void
-     * @throws EE_Error
-     */
-    public function e_pretty_status($show_icons = false)
-    {
-        echo $this->pretty_status($show_icons);
-    }
-
-
-    /**
-     * Returns a nice version of the status for displaying to customers
-     *
-     * @param bool $show_icons
-     * @return string
-     * @throws EE_Error
-     */
-    public function pretty_status($show_icons = false)
-    {
-        $status = EEM_Status::instance()->localized_status(
-            array($this->status_ID() => esc_html__('unknown', 'event_espresso')),
-            false,
-            'sentence'
-        );
-        $icon = '';
-        switch ($this->status_ID()) {
-            case EEM_Registration::status_id_approved:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-star-filled ee-icon-size-16 green-text"></span>'
-                    : '';
-                break;
-            case EEM_Registration::status_id_pending_payment:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-star-half ee-icon-size-16 orange-text"></span>'
-                    : '';
-                break;
-            case EEM_Registration::status_id_not_approved:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-marker ee-icon-size-16 orange-text"></span>'
-                    : '';
-                break;
-            case EEM_Registration::status_id_cancelled:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-no ee-icon-size-16 lt-grey-text"></span>'
-                    : '';
-                break;
-            case EEM_Registration::status_id_incomplete:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-no ee-icon-size-16 lt-orange-text"></span>'
-                    : '';
-                break;
-            case EEM_Registration::status_id_declined:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-no ee-icon-size-16 red-text"></span>'
-                    : '';
-                break;
-            case EEM_Registration::status_id_wait_list:
-                $icon = $show_icons
-                    ? '<span class="dashicons dashicons-clipboard ee-icon-size-16 purple-text"></span>'
-                    : '';
-                break;
-        }
-        return $icon . $status[ $this->status_ID() ];
-    }
-
-
-    /**
-     *        get Attendee Is Going
-     */
-    public function att_is_going()
-    {
-        return $this->get('REG_att_is_going');
-    }
-
-
-    /**
-     * Gets related answers
-     *
-     * @param array $query_params @see https://github.com/eventespresso/event-espresso-core/tree/master/docs/G--Model-System/model-query-params.md
-     * @return EE_Answer[]
-     * @throws EE_Error
-     */
-    public function answers($query_params = null)
-    {
-        return $this->get_many_related('Answer', $query_params);
-    }
-
-
-    /**
-     * Gets the registration's answer value to the specified question
-     * (either the question's ID or a question object)
-     *
-     * @param EE_Question|int $question
-     * @param bool            $pretty_value
-     * @return array|string if pretty_value= true, the result will always be a string
-     * (because the answer might be an array of answer values, so passing pretty_value=true
-     * will convert it into some kind of string)
-     * @throws EE_Error
-     */
-    public function answer_value_to_question($question, $pretty_value = true)
-    {
-        $question_id = EEM_Question::instance()->ensure_is_ID($question);
-        return EEM_Answer::instance()->get_answer_value_to_question($this, $question_id, $pretty_value);
-    }
-
-
-    /**
-     * question_groups
-     * returns an array of EE_Question_Group objects for this registration
-     *
-     * @return EE_Question_Group[]
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public function question_groups()
-    {
-        return EEM_Event::instance()->get_question_groups_for_event($this->event_ID(), $this);
-    }
-
-
-    /**
-     * count_question_groups
-     * returns a count of the number of EE_Question_Group objects for this registration
-     *
-     * @return int
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public function count_question_groups()
-    {
-        return EEM_Event::instance()->count_related(
-            $this->event_ID(),
-            'Question_Group',
-            [
-                [
-                    'Event_Question_Group.'
-                    . EEM_Event_Question_Group::instance()->fieldNameForContext($this->is_primary_registrant()) => true,
-                ]
-            ]
-        );
-    }
-
-
-    /**
-     * Returns the registration date in the 'standard' string format
-     * (function may be improved in the future to allow for different formats and timezones)
-     *
-     * @return string
-     * @throws EE_Error
-     */
-    public function reg_date()
-    {
-        return $this->get_datetime('REG_date');
-    }
-
-
-    /**
-     * Gets the datetime-ticket for this registration (ie, it can be used to isolate
-     * the ticket this registration purchased, or the datetime they have registered
-     * to attend)
-     *
-     * @return EE_Datetime_Ticket
-     * @throws EE_Error
-     */
-    public function datetime_ticket()
-    {
-        return $this->get_first_related('Datetime_Ticket');
-    }
-
-
-    /**
-     * Sets the registration's datetime_ticket.
-     *
-     * @param EE_Datetime_Ticket $datetime_ticket
-     * @return EE_Datetime_Ticket
-     * @throws EE_Error
-     */
-    public function set_datetime_ticket($datetime_ticket)
-    {
-        return $this->_add_relation_to($datetime_ticket, 'Datetime_Ticket');
-    }
-
-    /**
-     * Gets deleted
-     *
-     * @return bool
-     * @throws EE_Error
-     */
-    public function deleted()
-    {
-        return $this->get('REG_deleted');
-    }
-
-    /**
-     * Sets deleted
-     *
-     * @param boolean $deleted
-     * @return bool
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_deleted($deleted)
-    {
-        if ($deleted) {
-            $this->delete();
-        } else {
-            $this->restore();
-        }
-    }
-
-
-    /**
-     * Get the status object of this object
-     *
-     * @return EE_Status
-     * @throws EE_Error
-     */
-    public function status_obj()
-    {
-        return $this->get_first_related('Status');
-    }
-
-
-    /**
-     * Returns the number of times this registration has checked into any of the datetimes
-     * its available for
-     *
-     * @return int
-     * @throws EE_Error
-     */
-    public function count_checkins()
-    {
-        return $this->get_model()->count_related($this, 'Checkin');
-    }
-
-
-    /**
-     * Returns the number of current Check-ins this registration is checked into for any of the datetimes the
-     * registration is for.  Note, this is ONLY checked in (does not include checkedout)
-     *
-     * @return int
-     * @throws EE_Error
-     */
-    public function count_checkins_not_checkedout()
-    {
-        return $this->get_model()->count_related($this, 'Checkin', array(array('CHK_in' => 1)));
-    }
-
-
-    /**
-     * The purpose of this method is simply to check whether this registration can checkin to the given datetime.
-     *
-     * @param int | EE_Datetime $DTT_OR_ID      The datetime the registration is being checked against
-     * @param bool              $check_approved This is used to indicate whether the caller wants can_checkin to also
-     *                                          consider registration status as well as datetime access.
-     * @return bool
-     * @throws EE_Error
-     */
-    public function can_checkin($DTT_OR_ID, $check_approved = true)
-    {
-        $DTT_ID = EEM_Datetime::instance()->ensure_is_ID($DTT_OR_ID);
-
-        // first check registration status
-        if (($check_approved && ! $this->is_approved()) || ! $DTT_ID) {
-            return false;
-        }
-        // is there a datetime ticket that matches this dtt_ID?
-        if (! (EEM_Datetime_Ticket::instance()->exists(
-            array(
-                array(
-                    'TKT_ID' => $this->get('TKT_ID'),
-                    'DTT_ID' => $DTT_ID,
-                ),
-            )
-        ))
-        ) {
-            return false;
-        }
-
-        // final check is against TKT_uses
-        return $this->verify_can_checkin_against_TKT_uses($DTT_ID);
-    }
-
-
-    /**
-     * This method verifies whether the user can checkin for the given datetime considering the max uses value set on
-     * the ticket. To do this,  a query is done to get the count of the datetime records already checked into.  If the
-     * datetime given does not have a check-in record and checking in for that datetime will exceed the allowed uses,
-     * then return false.  Otherwise return true.
-     *
-     * @param int | EE_Datetime $DTT_OR_ID The datetime the registration is being checked against
-     * @return bool true means can checkin.  false means cannot checkin.
-     * @throws EE_Error
-     */
-    public function verify_can_checkin_against_TKT_uses($DTT_OR_ID)
-    {
-        $DTT_ID = EEM_Datetime::instance()->ensure_is_ID($DTT_OR_ID);
-
-        if (! $DTT_ID) {
-            return false;
-        }
-
-        $max_uses = $this->ticket() instanceof EE_Ticket ? $this->ticket()->uses() : EE_INF;
-
-        // if max uses is not set or equals infinity then return true cause its not a factor for whether user can
-        // check-in or not.
-        if (! $max_uses || $max_uses === EE_INF) {
-            return true;
-        }
-
-        // does this datetime have a checkin record?  If so, then the dtt count has already been verified so we can just
-        // go ahead and toggle.
-        if (EEM_Checkin::instance()->exists(array(array('REG_ID' => $this->ID(), 'DTT_ID' => $DTT_ID)))) {
-            return true;
-        }
-
-        // made it here so the last check is whether the number of checkins per unique datetime on this registration
-        // disallows further check-ins.
-        $count_unique_dtt_checkins = EEM_Checkin::instance()->count(
-            array(
-                array(
-                    'REG_ID' => $this->ID(),
-                    'CHK_in' => true,
-                ),
-            ),
-            'DTT_ID',
-            true
-        );
-        // checkins have already reached their max number of uses
-        // so registrant can NOT checkin
-        if ($count_unique_dtt_checkins >= $max_uses) {
-            EE_Error::add_error(
-                esc_html__(
-                    'Check-in denied because number of datetime uses for the ticket has been reached or exceeded.',
-                    'event_espresso'
-                ),
-                __FILE__,
-                __FUNCTION__,
-                __LINE__
-            );
-            return false;
-        }
-        return true;
-    }
-
-
-    /**
-     * toggle Check-in status for this registration
-     * Check-ins are toggled in the following order:
-     * never checked in -> checked in
-     * checked in -> checked out
-     * checked out -> checked in
-     *
-     * @param  int $DTT_ID  include specific datetime to toggle Check-in for.
-     *                      If not included or null, then it is assumed latest datetime is being toggled.
-     * @param bool $verify  If true then can_checkin() is used to verify whether the person
-     *                      can be checked in or not.  Otherwise this forces change in checkin status.
-     * @return bool|int     the chk_in status toggled to OR false if nothing got changed.
-     * @throws EE_Error
-     */
-    public function toggle_checkin_status($DTT_ID = null, $verify = false)
-    {
-        if (empty($DTT_ID)) {
-            $datetime = $this->get_latest_related_datetime();
-            $DTT_ID = $datetime instanceof EE_Datetime ? $datetime->ID() : 0;
-            // verify the registration can checkin for the given DTT_ID
-        } elseif (! $this->can_checkin($DTT_ID, $verify)) {
-            EE_Error::add_error(
-                sprintf(
-                    esc_html__(
-                        'The given registration (ID:%1$d) can not be checked in to the given DTT_ID (%2$d), because the registration does not have access',
-                        'event_espresso'
-                    ),
-                    $this->ID(),
-                    $DTT_ID
-                ),
-                __FILE__,
-                __FUNCTION__,
-                __LINE__
-            );
-            return false;
-        }
-        $status_paths = array(
-            EE_Checkin::status_checked_never => EE_Checkin::status_checked_in,
-            EE_Checkin::status_checked_in    => EE_Checkin::status_checked_out,
-            EE_Checkin::status_checked_out   => EE_Checkin::status_checked_in,
-        );
-        // start by getting the current status so we know what status we'll be changing to.
-        $cur_status = $this->check_in_status_for_datetime($DTT_ID, null);
-        $status_to = $status_paths[ $cur_status ];
-        // database only records true for checked IN or false for checked OUT
-        // no record ( null ) means checked in NEVER, but we obviously don't save that
-        $new_status = $status_to === EE_Checkin::status_checked_in ? true : false;
-        // add relation - note Check-ins are always creating new rows
-        // because we are keeping track of Check-ins over time.
-        // Eventually we'll probably want to show a list table
-        // for the individual Check-ins so that they can be managed.
-        $checkin = EE_Checkin::new_instance(
-            array(
-                'REG_ID' => $this->ID(),
-                'DTT_ID' => $DTT_ID,
-                'CHK_in' => $new_status,
-            )
-        );
-        // if the record could not be saved then return false
-        if ($checkin->save() === 0) {
-            if (WP_DEBUG) {
-                global $wpdb;
-                $error = sprintf(
-                    esc_html__(
-                        'Registration check in update failed because of the following database error: %1$s%2$s',
-                        'event_espresso'
-                    ),
-                    '<br />',
-                    $wpdb->last_error
-                );
-            } else {
-                $error = esc_html__(
-                    'Registration check in update failed because of an unknown database error',
-                    'event_espresso'
-                );
-            }
-            EE_Error::add_error($error, __FILE__, __FUNCTION__, __LINE__);
-            return false;
-        }
-        // Fire a checked_in and checkout_out action.
-        $checked_status = $status_to === EE_Checkin::status_checked_in ? 'checked_in' : 'checked_out';
-        do_action('AHEE__EE_Registration__toggle_checkin_status__{$checked_status}', $this, $DTT_ID);
-        return $status_to;
-    }
-
-
-    /**
-     * Returns the latest datetime related to this registration (via the ticket attached to the registration).
-     * "Latest" is defined by the `DTT_EVT_start` column.
-     *
-     * @return EE_Datetime|null
-     * @throws EE_Error
-     */
-    public function get_latest_related_datetime()
-    {
-        return EEM_Datetime::instance()->get_one(
-            array(
-                array(
-                    'Ticket.Registration.REG_ID' => $this->ID(),
-                ),
-                'order_by' => array('DTT_EVT_start' => 'DESC'),
-            )
-        );
-    }
-
-
-    /**
-     * Returns the earliest datetime related to this registration (via the ticket attached to the registration).
-     * "Earliest" is defined by the `DTT_EVT_start` column.
-     *
-     * @throws EE_Error
-     */
-    public function get_earliest_related_datetime()
-    {
-        return EEM_Datetime::instance()->get_one(
-            array(
-                array(
-                    'Ticket.Registration.REG_ID' => $this->ID(),
-                ),
-                'order_by' => array('DTT_EVT_start' => 'ASC'),
-            )
-        );
-    }
-
-
-    /**
-     * This method simply returns the check-in status for this registration and the given datetime.
-     * If neither the datetime nor the checkin values are provided as arguments,
-     * then this will return the LATEST check-in status for the registration across all datetimes it belongs to.
-     *
-     * @param  int       $DTT_ID  The ID of the datetime we're checking against
-     *                            (if empty we'll get the primary datetime for
-     *                            this registration (via event) and use it's ID);
-     * @param EE_Checkin $checkin If present, we use the given checkin object rather than the dtt_id.
-     *
-     * @return int                Integer representing Check-in status.
-     * @throws EE_Error
-     */
-    public function check_in_status_for_datetime($DTT_ID = 0, $checkin = null)
-    {
-        $checkin_query_params = array(
-            'order_by' => array('CHK_timestamp' => 'DESC'),
-        );
-
-        if ($DTT_ID > 0) {
-            $checkin_query_params[0] = array('DTT_ID' => $DTT_ID);
-        }
-
-        // get checkin object (if exists)
-        $checkin = $checkin instanceof EE_Checkin
-            ? $checkin
-            : $this->get_first_related('Checkin', $checkin_query_params);
-        if ($checkin instanceof EE_Checkin) {
-            if ($checkin->get('CHK_in')) {
-                return EE_Checkin::status_checked_in; // checked in
-            }
-            return EE_Checkin::status_checked_out; // had checked in but is now checked out.
-        }
-        return EE_Checkin::status_checked_never; // never been checked in
-    }
-
-
-    /**
-     * This method returns a localized message for the toggled Check-in message.
-     *
-     * @param  int $DTT_ID include specific datetime to get the correct Check-in message.  If not included or null,
-     *                     then it is assumed Check-in for primary datetime was toggled.
-     * @param bool $error  This just flags that you want an error message returned. This is put in so that the error
-     *                     message can be customized with the attendee name.
-     * @return string internationalized message
-     * @throws EE_Error
-     */
-    public function get_checkin_msg($DTT_ID, $error = false)
-    {
-        // let's get the attendee first so we can include the name of the attendee
-        $attendee = $this->get_first_related('Attendee');
-        if ($attendee instanceof EE_Attendee) {
-            if ($error) {
-                return sprintf(__("%s's check-in status was not changed.", "event_espresso"), $attendee->full_name());
-            }
-            $cur_status = $this->check_in_status_for_datetime($DTT_ID);
-            // what is the status message going to be?
-            switch ($cur_status) {
-                case EE_Checkin::status_checked_never:
-                    return sprintf(
-                        __("%s has been removed from Check-in records", "event_espresso"),
-                        $attendee->full_name()
-                    );
-                    break;
-                case EE_Checkin::status_checked_in:
-                    return sprintf(__('%s has been checked in', 'event_espresso'), $attendee->full_name());
-                    break;
-                case EE_Checkin::status_checked_out:
-                    return sprintf(__('%s has been checked out', 'event_espresso'), $attendee->full_name());
-                    break;
-            }
-        }
-        return esc_html__("The check-in status could not be determined.", "event_espresso");
-    }
-
-
-    /**
-     * Returns the related EE_Transaction to this registration
-     *
-     * @return EE_Transaction
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     */
-    public function transaction()
-    {
-        $transaction = $this->get_first_related('Transaction');
-        if (! $transaction instanceof \EE_Transaction) {
-            throw new EntityNotFoundException('Transaction ID', $this->transaction_ID());
-        }
-        return $transaction;
-    }
-
-
-    /**
-     *        get Registration Code
-     */
-    public function reg_code()
-    {
-        return $this->get('REG_code');
-    }
-
-
-    /**
-     *        get Transaction ID
-     */
-    public function transaction_ID()
-    {
-        return $this->get('TXN_ID');
-    }
-
-
-    /**
-     * @return int
-     * @throws EE_Error
-     */
-    public function ticket_ID()
-    {
-        return $this->get('TKT_ID');
-    }
-
-
-    /**
-     *        Set Registration Code
-     *
-     * @access    public
-     * @param    string  $REG_code Registration Code
-     * @param    boolean $use_default
-     * @throws EE_Error
-     */
-    public function set_reg_code($REG_code, $use_default = false)
-    {
-        if (empty($REG_code)) {
-            EE_Error::add_error(
-                esc_html__('REG_code can not be empty.', 'event_espresso'),
-                __FILE__,
-                __FUNCTION__,
-                __LINE__
-            );
-            return;
-        }
-        if (! $this->reg_code()) {
-            parent::set('REG_code', $REG_code, $use_default);
-        } else {
-            EE_Error::doing_it_wrong(
-                __CLASS__ . '::' . __FUNCTION__,
-                esc_html__('Can not change a registration REG_code once it has been set.', 'event_espresso'),
-                '4.6.0'
-            );
-        }
-    }
-
-
-    /**
-     * Returns all other registrations in the same group as this registrant who have the same ticket option.
-     * Note, if you want to just get all registrations in the same transaction (group), use:
-     *    $registration->transaction()->registrations();
-     *
-     * @since 4.5.0
-     * @return EE_Registration[] or empty array if this isn't a group registration.
-     * @throws EE_Error
-     */
-    public function get_all_other_registrations_in_group()
-    {
-        if ($this->group_size() < 2) {
-            return array();
-        }
-
-        $query[0] = array(
-            'TXN_ID' => $this->transaction_ID(),
-            'REG_ID' => array('!=', $this->ID()),
-            'TKT_ID' => $this->ticket_ID(),
-        );
-        /** @var EE_Registration[] $registrations */
-        $registrations = $this->get_model()->get_all($query);
-        return $registrations;
-    }
-
-    /**
-     * Return the link to the admin details for the object.
-     *
-     * @return string
-     * @throws EE_Error
-     */
-    public function get_admin_details_link()
-    {
-        EE_Registry::instance()->load_helper('URL');
-        return EEH_URL::add_query_args_and_nonce(
-            array(
-                'page'    => 'espresso_registrations',
-                'action'  => 'view_registration',
-                '_REG_ID' => $this->ID(),
-            ),
-            admin_url('admin.php')
-        );
-    }
-
-    /**
-     * Returns the link to the editor for the object.  Sometimes this is the same as the details.
-     *
-     * @return string
-     * @throws EE_Error
-     */
-    public function get_admin_edit_link()
-    {
-        return $this->get_admin_details_link();
-    }
-
-    /**
-     * Returns the link to a settings page for the object.
-     *
-     * @return string
-     * @throws EE_Error
-     */
-    public function get_admin_settings_link()
-    {
-        return $this->get_admin_details_link();
-    }
-
-    /**
-     * Returns the link to the "overview" for the object (typically the "list table" view).
-     *
-     * @return string
-     */
-    public function get_admin_overview_link()
-    {
-        EE_Registry::instance()->load_helper('URL');
-        return EEH_URL::add_query_args_and_nonce(
-            array(
-                'page' => 'espresso_registrations',
-            ),
-            admin_url('admin.php')
-        );
-    }
-
-
-    /**
-     * @param array $query_params
-     *
-     * @return \EE_Registration[]
-     * @throws EE_Error
-     */
-    public function payments($query_params = array())
-    {
-        return $this->get_many_related('Payment', $query_params);
-    }
-
-
-    /**
-     * @param array $query_params
-     *
-     * @return \EE_Registration_Payment[]
-     * @throws EE_Error
-     */
-    public function registration_payments($query_params = array())
-    {
-        return $this->get_many_related('Registration_Payment', $query_params);
-    }
-
-
-    /**
-     * This grabs the payment method corresponding to the last payment made for the amount owing on the registration.
-     * Note: if there are no payments on the registration there will be no payment method returned.
-     *
-     * @return EE_Payment_Method|null
-     */
-    public function payment_method()
-    {
-        return EEM_Payment_Method::instance()->get_last_used_for_registration($this);
-    }
-
-
-    /**
-     * @return \EE_Line_Item
-     * @throws EntityNotFoundException
-     * @throws EE_Error
-     */
-    public function ticket_line_item()
-    {
-        $ticket = $this->ticket();
-        $transaction = $this->transaction();
-        $line_item = null;
-        $ticket_line_items = \EEH_Line_Item::get_line_items_by_object_type_and_IDs(
-            $transaction->total_line_item(),
-            'Ticket',
-            array($ticket->ID())
-        );
-        foreach ($ticket_line_items as $ticket_line_item) {
-            if ($ticket_line_item instanceof \EE_Line_Item
-                && $ticket_line_item->OBJ_type() === 'Ticket'
-                && $ticket_line_item->OBJ_ID() === $ticket->ID()
-            ) {
-                $line_item = $ticket_line_item;
-                break;
-            }
-        }
-        if (! ($line_item instanceof \EE_Line_Item && $line_item->OBJ_type() === 'Ticket')) {
-            throw new EntityNotFoundException('Line Item Ticket ID', $ticket->ID());
-        }
-        return $line_item;
-    }
-
-
-    /**
-     * Soft Deletes this model object.
-     *
-     * @return boolean | int
-     * @throws RuntimeException
-     * @throws EE_Error
-     */
-    public function delete()
-    {
-        if ($this->update_extra_meta(EE_Registration::PRE_TRASH_REG_STATUS_KEY, $this->status_ID()) === true) {
-            $this->set_status(EEM_Registration::status_id_cancelled);
-        }
-        return parent::delete();
-    }
-
-
-    /**
-     * Restores whatever the previous status was on a registration before it was trashed (if possible)
-     *
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function restore()
-    {
-        $previous_status = $this->get_extra_meta(
-            EE_Registration::PRE_TRASH_REG_STATUS_KEY,
-            true,
-            EEM_Registration::status_id_cancelled
-        );
-        if ($previous_status) {
-            $this->delete_extra_meta(EE_Registration::PRE_TRASH_REG_STATUS_KEY);
-            $this->set_status($previous_status);
-        }
-        return parent::restore();
-    }
-
-
-    /**
-     * possibly toggle Registration status based on comparison of REG_paid vs REG_final_price
-     *
-     * @param  boolean $trigger_set_status_logic EE_Registration::set_status() can trigger additional logic
-     *                                           depending on whether the reg status changes to or from "Approved"
-     * @return boolean whether the Registration status was updated
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function updateStatusBasedOnTotalPaid($trigger_set_status_logic = true)
-    {
-        $paid = $this->paid();
-        $price = $this->final_price();
-        switch (true) {
-            // overpaid or paid
-            case EEH_Money::compare_floats($paid, $price, '>'):
-            case EEH_Money::compare_floats($paid, $price):
-                $new_status = EEM_Registration::status_id_approved;
-                break;
-            //  underpaid
-            case EEH_Money::compare_floats($paid, $price, '<'):
-                $new_status = EEM_Registration::status_id_pending_payment;
-                break;
-            // uhhh Houston...
-            default:
-                throw new RuntimeException(
-                    esc_html__('The total paid calculation for this registration is inaccurate.', 'event_espresso')
-                );
-        }
-        if ($new_status !== $this->status_ID()) {
-            if ($trigger_set_status_logic) {
-                return $this->set_status($new_status);
-            }
-            parent::set('STS_ID', $new_status);
-            return true;
-        }
-        return false;
-    }
-
-
-    /*************************** DEPRECATED ***************************/
-
-
-    /**
-     * @deprecated
-     * @since     4.7.0
-     * @access    public
-     */
-    public function price_paid()
-    {
-        EE_Error::doing_it_wrong(
-            'EE_Registration::price_paid()',
-            esc_html__(
-                'This method is deprecated, please use EE_Registration::final_price() instead.',
-                'event_espresso'
-            ),
-            '4.7.0'
-        );
-        return $this->final_price();
-    }
-
-
-    /**
-     * @deprecated
-     * @since     4.7.0
-     * @access    public
-     * @param    float $REG_final_price
-     * @throws EE_Error
-     * @throws RuntimeException
-     */
-    public function set_price_paid($REG_final_price = 0.00)
-    {
-        EE_Error::doing_it_wrong(
-            'EE_Registration::set_price_paid()',
-            esc_html__(
-                'This method is deprecated, please use EE_Registration::set_final_price() instead.',
-                'event_espresso'
-            ),
-            '4.7.0'
-        );
-        $this->set_final_price($REG_final_price);
-    }
-
-
-    /**
-     * @deprecated
-     * @since 4.7.0
-     * @return string
-     * @throws EE_Error
-     */
-    public function pretty_price_paid()
-    {
-        EE_Error::doing_it_wrong(
-            'EE_Registration::pretty_price_paid()',
-            esc_html__(
-                'This method is deprecated, please use EE_Registration::pretty_final_price() instead.',
-                'event_espresso'
-            ),
-            '4.7.0'
-        );
-        return $this->pretty_final_price();
-    }
-
-
-    /**
-     * Gets the primary datetime related to this registration via the related Event to this registration
-     *
-     * @deprecated 4.9.17
-     * @return EE_Datetime
-     * @throws EE_Error
-     * @throws EntityNotFoundException
-     */
-    public function get_related_primary_datetime()
-    {
-        EE_Error::doing_it_wrong(
-            __METHOD__,
-            esc_html__(
-                'Use EE_Registration::get_latest_related_datetime() or EE_Registration::get_earliest_related_datetime()',
-                'event_espresso'
-            ),
-            '4.9.17',
-            '5.0.0'
-        );
-        return $this->event()->primary_datetime();
-    }
+	/**
+	 * Used to reference when a registration has never been checked in.
+	 *
+	 * @deprecated use \EE_Checkin::status_checked_never instead
+	 * @type int
+	 */
+	const checkin_status_never = 2;
+
+	/**
+	 * Used to reference when a registration has been checked in.
+	 *
+	 * @deprecated use \EE_Checkin::status_checked_in instead
+	 * @type int
+	 */
+	const checkin_status_in = 1;
+
+
+	/**
+	 * Used to reference when a registration has been checked out.
+	 *
+	 * @deprecated use \EE_Checkin::status_checked_out instead
+	 * @type int
+	 */
+	const checkin_status_out = 0;
+
+
+	/**
+	 * extra meta key for tracking reg status os trashed registrations
+	 *
+	 * @type string
+	 */
+	const PRE_TRASH_REG_STATUS_KEY = 'pre_trash_registration_status';
+
+
+	/**
+	 * extra meta key for tracking if registration has reserved ticket
+	 *
+	 * @type string
+	 */
+	const HAS_RESERVED_TICKET_KEY = 'has_reserved_ticket';
+
+
+	/**
+	 * @param array  $props_n_values          incoming values
+	 * @param string $timezone                incoming timezone (if not set the timezone set for the website will be
+	 *                                        used.)
+	 * @param array  $date_formats            incoming date_formats in an array where the first value is the
+	 *                                        date_format and the second value is the time format
+	 * @return EE_Registration
+	 * @throws EE_Error
+	 */
+	public static function new_instance($props_n_values = array(), $timezone = null, $date_formats = array())
+	{
+		$has_object = parent::_check_for_object($props_n_values, __CLASS__, $timezone, $date_formats);
+		return $has_object ? $has_object : new self($props_n_values, false, $timezone, $date_formats);
+	}
+
+
+	/**
+	 * @param array  $props_n_values  incoming values from the database
+	 * @param string $timezone        incoming timezone as set by the model.  If not set the timezone for
+	 *                                the website will be used.
+	 * @return EE_Registration
+	 */
+	public static function new_instance_from_db($props_n_values = array(), $timezone = null)
+	{
+		return new self($props_n_values, true, $timezone);
+	}
+
+
+	/**
+	 *        Set Event ID
+	 *
+	 * @param        int $EVT_ID Event ID
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_event($EVT_ID = 0)
+	{
+		$this->set('EVT_ID', $EVT_ID);
+	}
+
+
+	/**
+	 * Overrides parent set() method so that all calls to set( 'REG_code', $REG_code ) OR set( 'STS_ID', $STS_ID ) can
+	 * be routed to internal methods
+	 *
+	 * @param string $field_name
+	 * @param mixed  $field_value
+	 * @param bool   $use_default
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws RuntimeException
+	 */
+	public function set($field_name, $field_value, $use_default = false)
+	{
+		switch ($field_name) {
+			case 'REG_code':
+				if (! empty($field_value) && $this->reg_code() === null) {
+					$this->set_reg_code($field_value, $use_default);
+				}
+				break;
+			case 'STS_ID':
+				$this->set_status($field_value, $use_default);
+				break;
+			default:
+				parent::set($field_name, $field_value, $use_default);
+		}
+	}
+
+
+	/**
+	 * Set Status ID
+	 * updates the registration status and ALSO...
+	 * calls reserve_registration_space() if the reg status changes TO approved from any other reg status
+	 * calls release_registration_space() if the reg status changes FROM approved to any other reg status
+	 *
+	 * @param string                $new_STS_ID
+	 * @param boolean               $use_default
+	 * @param ContextInterface|null $context
+	 * @return bool
+	 * @throws DomainException
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws RuntimeException
+	 * @throws UnexpectedEntityException
+	 */
+	public function set_status($new_STS_ID = null, $use_default = false, ContextInterface $context = null)
+	{
+		// get current REG_Status
+		$old_STS_ID = $this->status_ID();
+		// if status has changed
+		if ($old_STS_ID !== $new_STS_ID // and that status has actually changed
+			&& ! empty($old_STS_ID) // and that old status is actually set
+			&& ! empty($new_STS_ID) // as well as the new status
+			&& $this->ID() // ensure registration is in the db
+		) {
+			// update internal status first
+			parent::set('STS_ID', $new_STS_ID, $use_default);
+			// THEN handle other changes that occur when reg status changes
+			// TO approved
+			if ($new_STS_ID === EEM_Registration::status_id_approved) {
+				// reserve a space by incrementing ticket and datetime sold values
+				$this->reserveRegistrationSpace();
+				do_action('AHEE__EE_Registration__set_status__to_approved', $this, $old_STS_ID, $new_STS_ID, $context);
+				// OR FROM  approved
+			} elseif ($old_STS_ID === EEM_Registration::status_id_approved) {
+				// release a space by decrementing ticket and datetime sold values
+				$this->releaseRegistrationSpace();
+				do_action(
+					'AHEE__EE_Registration__set_status__from_approved',
+					$this,
+					$old_STS_ID,
+					$new_STS_ID,
+					$context
+				);
+			}
+			// update status
+			parent::set('STS_ID', $new_STS_ID, $use_default);
+			$this->updateIfCanceledOrReinstated($new_STS_ID, $old_STS_ID, $context);
+			if ($this->statusChangeUpdatesTransaction($context)) {
+				$this->updateTransactionAfterStatusChange();
+			}
+			do_action('AHEE__EE_Registration__set_status__after_update', $this, $old_STS_ID, $new_STS_ID, $context);
+			return true;
+		}
+		// even though the old value matches the new value, it's still good to
+		// allow the parent set method to have a say
+		parent::set('STS_ID', $new_STS_ID, $use_default);
+		return true;
+	}
+
+
+	/**
+	 * update REGs and TXN when cancelled or declined registrations involved
+	 *
+	 * @param string                $new_STS_ID
+	 * @param string                $old_STS_ID
+	 * @param ContextInterface|null $context
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws RuntimeException
+	 */
+	private function updateIfCanceledOrReinstated($new_STS_ID, $old_STS_ID, ContextInterface $context = null)
+	{
+		// these reg statuses should not be considered in any calculations involving monies owing
+		$closed_reg_statuses = EEM_Registration::closed_reg_statuses();
+		// true if registration has been cancelled or declined
+		$this->updateIfCanceled(
+			$closed_reg_statuses,
+			$new_STS_ID,
+			$old_STS_ID,
+			$context
+		);
+		$this->updateIfReinstated(
+			$closed_reg_statuses,
+			$new_STS_ID,
+			$old_STS_ID,
+			$context
+		);
+	}
+
+
+	/**
+	 * update REGs and TXN when cancelled or declined registrations involved
+	 *
+	 * @param array                 $closed_reg_statuses
+	 * @param string                $new_STS_ID
+	 * @param string                $old_STS_ID
+	 * @param ContextInterface|null $context
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws RuntimeException
+	 */
+	private function updateIfCanceled(
+		array $closed_reg_statuses,
+		$new_STS_ID,
+		$old_STS_ID,
+		ContextInterface $context = null
+	) {
+		// true if registration has been cancelled or declined
+		if (in_array($new_STS_ID, $closed_reg_statuses, true)
+			&& ! in_array($old_STS_ID, $closed_reg_statuses, true)
+		) {
+			/** @type EE_Registration_Processor $registration_processor */
+			$registration_processor = EE_Registry::instance()->load_class('Registration_Processor');
+			/** @type EE_Transaction_Processor $transaction_processor */
+			$transaction_processor = EE_Registry::instance()->load_class('Transaction_Processor');
+			// cancelled or declined registration
+			$registration_processor->update_registration_after_being_canceled_or_declined(
+				$this,
+				$closed_reg_statuses
+			);
+			$transaction_processor->update_transaction_after_canceled_or_declined_registration(
+				$this,
+				$closed_reg_statuses,
+				false
+			);
+			do_action(
+				'AHEE__EE_Registration__set_status__canceled_or_declined',
+				$this,
+				$old_STS_ID,
+				$new_STS_ID,
+				$context
+			);
+			return;
+		}
+	}
+
+
+	/**
+	 * update REGs and TXN when cancelled or declined registrations involved
+	 *
+	 * @param array                 $closed_reg_statuses
+	 * @param string                $new_STS_ID
+	 * @param string                $old_STS_ID
+	 * @param ContextInterface|null $context
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	private function updateIfReinstated(
+		array $closed_reg_statuses,
+		$new_STS_ID,
+		$old_STS_ID,
+		ContextInterface $context = null
+	) {
+		// true if reinstating cancelled or declined registration
+		if (in_array($old_STS_ID, $closed_reg_statuses, true)
+			&& ! in_array($new_STS_ID, $closed_reg_statuses, true)
+		) {
+			/** @type EE_Registration_Processor $registration_processor */
+			$registration_processor = EE_Registry::instance()->load_class('Registration_Processor');
+			/** @type EE_Transaction_Processor $transaction_processor */
+			$transaction_processor = EE_Registry::instance()->load_class('Transaction_Processor');
+			// reinstating cancelled or declined registration
+			$registration_processor->update_canceled_or_declined_registration_after_being_reinstated(
+				$this,
+				$closed_reg_statuses
+			);
+			$transaction_processor->update_transaction_after_reinstating_canceled_registration(
+				$this,
+				$closed_reg_statuses,
+				false
+			);
+			do_action(
+				'AHEE__EE_Registration__set_status__after_reinstated',
+				$this,
+				$old_STS_ID,
+				$new_STS_ID,
+				$context
+			);
+		}
+	}
+
+
+	/**
+	 * @param ContextInterface|null $context
+	 * @return bool
+	 */
+	private function statusChangeUpdatesTransaction(ContextInterface $context = null)
+	{
+		$contexts_that_do_not_update_transaction = (array) apply_filters(
+			'AHEE__EE_Registration__statusChangeUpdatesTransaction__contexts_that_do_not_update_transaction',
+			array('spco_reg_step_attendee_information_process_registrations'),
+			$context,
+			$this
+		);
+		return ! (
+			$context instanceof ContextInterface
+			&& in_array($context->slug(), $contexts_that_do_not_update_transaction, true)
+		);
+	}
+
+
+	/**
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws RuntimeException
+	 */
+	private function updateTransactionAfterStatusChange()
+	{
+		/** @type EE_Transaction_Payments $transaction_payments */
+		$transaction_payments = EE_Registry::instance()->load_class('Transaction_Payments');
+		$transaction_payments->recalculate_transaction_total($this->transaction(), false);
+		$this->transaction()->update_status_based_on_total_paid(true);
+	}
+
+
+	/**
+	 *        get Status ID
+	 */
+	public function status_ID()
+	{
+		return $this->get('STS_ID');
+	}
+
+
+	/**
+	 * Gets the ticket this registration is for
+	 *
+	 * @param boolean $include_archived whether to include archived tickets or not.
+	 *
+	 * @return EE_Ticket|EE_Base_Class
+	 * @throws EE_Error
+	 */
+	public function ticket($include_archived = true)
+	{
+		$query_params = array();
+		if ($include_archived) {
+			$query_params['default_where_conditions'] = 'none';
+		}
+		return $this->get_first_related('Ticket', $query_params);
+	}
+
+
+	/**
+	 * Gets the event this registration is for
+	 *
+	 * @return EE_Event
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 */
+	public function event()
+	{
+		$event = $this->get_first_related('Event');
+		if (! $event instanceof \EE_Event) {
+			throw new EntityNotFoundException('Event ID', $this->event_ID());
+		}
+		return $event;
+	}
+
+
+	/**
+	 * Gets the "author" of the registration.  Note that for the purposes of registrations, the author will correspond
+	 * with the author of the event this registration is for.
+	 *
+	 * @since 4.5.0
+	 * @return int
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 */
+	public function wp_user()
+	{
+		$event = $this->event();
+		if ($event instanceof EE_Event) {
+			return $event->wp_user();
+		}
+		return 0;
+	}
+
+
+	/**
+	 * increments this registration's related ticket sold and corresponding datetime sold values
+	 *
+	 * @return void
+	 * @throws DomainException
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws UnexpectedEntityException
+	 */
+	private function reserveRegistrationSpace()
+	{
+		// reserved ticket and datetime counts will be decremented as sold counts are incremented
+		// so stop tracking that this reg has a ticket reserved
+		$this->release_reserved_ticket(false, "REG: {$this->ID()} (ln:" . __LINE__ . ')');
+		$ticket = $this->ticket();
+		$ticket->increaseSold();
+		// possibly set event status to sold out
+		$this->event()->perform_sold_out_status_check();
+	}
+
+
+	/**
+	 * decrements (subtracts) this registration's related ticket sold and corresponding datetime sold values
+	 *
+	 * @return void
+	 * @throws DomainException
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws UnexpectedEntityException
+	 */
+	private function releaseRegistrationSpace()
+	{
+		$ticket = $this->ticket();
+		$ticket->decreaseSold();
+		// possibly change event status from sold out back to previous status
+		$this->event()->perform_sold_out_status_check();
+	}
+
+
+	/**
+	 * tracks this registration's ticket reservation in extra meta
+	 * and can increment related ticket reserved and corresponding datetime reserved values
+	 *
+	 * @param bool $update_ticket if true, will increment ticket and datetime reserved count
+	 * @return void
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public function reserve_ticket($update_ticket = false, $source = 'unknown')
+	{
+		// only reserve ticket if space is not currently reserved
+		if ((bool) $this->get_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, true) !== true) {
+			$this->update_extra_meta('reserve_ticket', "{$this->ticket_ID()} from {$source}");
+			// IMPORTANT !!!
+			// although checking $update_ticket first would be more efficient,
+			// we NEED to ALWAYS call update_extra_meta(), which is why that is done first
+			if ($this->update_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, true)
+				&& $update_ticket
+			) {
+				$ticket = $this->ticket();
+				$ticket->increaseReserved(1, "REG: {$this->ID()} (ln:" . __LINE__ . ')');
+				$ticket->save();
+			}
+		}
+	}
+
+
+	/**
+	 * stops tracking this registration's ticket reservation in extra meta
+	 * decrements (subtracts) related ticket reserved and corresponding datetime reserved values
+	 *
+	 * @param bool $update_ticket if true, will decrement ticket and datetime reserved count
+	 * @return void
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public function release_reserved_ticket($update_ticket = false, $source = 'unknown')
+	{
+		// only release ticket if space is currently reserved
+		if ((bool) $this->get_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, true) === true) {
+			$this->update_extra_meta('release_reserved_ticket', "{$this->ticket_ID()} from {$source}");
+			// IMPORTANT !!!
+			// although checking $update_ticket first would be more efficient,
+			// we NEED to ALWAYS call update_extra_meta(), which is why that is done first
+			if ($this->update_extra_meta(EE_Registration::HAS_RESERVED_TICKET_KEY, false)
+				&& $update_ticket
+			) {
+				$ticket = $this->ticket();
+				$ticket->decreaseReserved(1, true, "REG: {$this->ID()} (ln:" . __LINE__ . ')');
+			}
+		}
+	}
+
+
+	/**
+	 * Set Attendee ID
+	 *
+	 * @param        int $ATT_ID Attendee ID
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_attendee_id($ATT_ID = 0)
+	{
+		$this->set('ATT_ID', $ATT_ID);
+	}
+
+
+	/**
+	 *        Set Transaction ID
+	 *
+	 * @param        int $TXN_ID Transaction ID
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_transaction_id($TXN_ID = 0)
+	{
+		$this->set('TXN_ID', $TXN_ID);
+	}
+
+
+	/**
+	 *        Set Session
+	 *
+	 * @param    string $REG_session PHP Session ID
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_session($REG_session = '')
+	{
+		$this->set('REG_session', $REG_session);
+	}
+
+
+	/**
+	 *        Set Registration URL Link
+	 *
+	 * @param    string $REG_url_link Registration URL Link
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_reg_url_link($REG_url_link = '')
+	{
+		$this->set('REG_url_link', $REG_url_link);
+	}
+
+
+	/**
+	 *        Set Attendee Counter
+	 *
+	 * @param        int $REG_count Primary Attendee
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_count($REG_count = 1)
+	{
+		$this->set('REG_count', $REG_count);
+	}
+
+
+	/**
+	 *        Set Group Size
+	 *
+	 * @param        boolean $REG_group_size Group Registration
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_group_size($REG_group_size = false)
+	{
+		$this->set('REG_group_size', $REG_group_size);
+	}
+
+
+	/**
+	 *    is_not_approved -  convenience method that returns TRUE if REG status ID ==
+	 *    EEM_Registration::status_id_not_approved
+	 *
+	 * @return        boolean
+	 */
+	public function is_not_approved()
+	{
+		return $this->status_ID() == EEM_Registration::status_id_not_approved ? true : false;
+	}
+
+
+	/**
+	 *    is_pending_payment -  convenience method that returns TRUE if REG status ID ==
+	 *    EEM_Registration::status_id_pending_payment
+	 *
+	 * @return        boolean
+	 */
+	public function is_pending_payment()
+	{
+		return $this->status_ID() == EEM_Registration::status_id_pending_payment ? true : false;
+	}
+
+
+	/**
+	 *    is_approved -  convenience method that returns TRUE if REG status ID == EEM_Registration::status_id_approved
+	 *
+	 * @return        boolean
+	 */
+	public function is_approved()
+	{
+		return $this->status_ID() == EEM_Registration::status_id_approved ? true : false;
+	}
+
+
+	/**
+	 *    is_cancelled -  convenience method that returns TRUE if REG status ID == EEM_Registration::status_id_cancelled
+	 *
+	 * @return        boolean
+	 */
+	public function is_cancelled()
+	{
+		return $this->status_ID() == EEM_Registration::status_id_cancelled ? true : false;
+	}
+
+
+	/**
+	 *    is_declined -  convenience method that returns TRUE if REG status ID == EEM_Registration::status_id_declined
+	 *
+	 * @return        boolean
+	 */
+	public function is_declined()
+	{
+		return $this->status_ID() == EEM_Registration::status_id_declined ? true : false;
+	}
+
+
+	/**
+	 *    is_incomplete -  convenience method that returns TRUE if REG status ID ==
+	 *    EEM_Registration::status_id_incomplete
+	 *
+	 * @return        boolean
+	 */
+	public function is_incomplete()
+	{
+		return $this->status_ID() == EEM_Registration::status_id_incomplete ? true : false;
+	}
+
+
+	/**
+	 *        Set Registration Date
+	 *
+	 * @param        mixed ( int or string ) $REG_date Registration Date - Unix timestamp or string representation of
+	 *                                                 Date
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_reg_date($REG_date = false)
+	{
+		$this->set('REG_date', $REG_date);
+	}
+
+
+	/**
+	 *    Set final price owing for this registration after all ticket/price modifications
+	 *
+	 * @access    public
+	 * @param    float $REG_final_price
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_final_price($REG_final_price = 0.00)
+	{
+		$this->set('REG_final_price', $REG_final_price);
+	}
+
+
+	/**
+	 *    Set amount paid towards this registration's final price
+	 *
+	 * @access    public
+	 * @param    float $REG_paid
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_paid($REG_paid = 0.00)
+	{
+		$this->set('REG_paid', $REG_paid);
+	}
+
+
+	/**
+	 *        Attendee Is Going
+	 *
+	 * @param        boolean $REG_att_is_going Attendee Is Going
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_att_is_going($REG_att_is_going = false)
+	{
+		$this->set('REG_att_is_going', $REG_att_is_going);
+	}
+
+
+	/**
+	 * Gets the related attendee
+	 *
+	 * @return EE_Attendee
+	 * @throws EE_Error
+	 */
+	public function attendee()
+	{
+		return $this->get_first_related('Attendee');
+	}
+
+
+	/**
+	 *        get Event ID
+	 */
+	public function event_ID()
+	{
+		return $this->get('EVT_ID');
+	}
+
+
+	/**
+	 *        get Event ID
+	 */
+	public function event_name()
+	{
+		$event = $this->event_obj();
+		if ($event) {
+			return $event->name();
+		} else {
+			return null;
+		}
+	}
+
+
+	/**
+	 * Fetches the event this registration is for
+	 *
+	 * @return EE_Event
+	 * @throws EE_Error
+	 */
+	public function event_obj()
+	{
+		return $this->get_first_related('Event');
+	}
+
+
+	/**
+	 *        get Attendee ID
+	 */
+	public function attendee_ID()
+	{
+		return $this->get('ATT_ID');
+	}
+
+
+	/**
+	 *        get PHP Session ID
+	 */
+	public function session_ID()
+	{
+		return $this->get('REG_session');
+	}
+
+
+	/**
+	 * Gets the string which represents the URL trigger for the receipt template in the message template system.
+	 *
+	 * @param string $messenger 'pdf' or 'html'.  Default 'html'.
+	 * @return string
+	 */
+	public function receipt_url($messenger = 'html')
+	{
+
+		/**
+		 * The below will be deprecated one version after this.  We check first if there is a custom receipt template
+		 * already in use on old system.  If there is then we just return the standard url for it.
+		 *
+		 * @since 4.5.0
+		 */
+		$template_relative_path = 'modules/gateways/Invoice/lib/templates/receipt_body.template.php';
+		$has_custom = EEH_Template::locate_template(
+			$template_relative_path,
+			array(),
+			true,
+			true,
+			true
+		);
+
+		if ($has_custom) {
+			return add_query_arg(array('receipt' => 'true'), $this->invoice_url('launch'));
+		}
+		return apply_filters('FHEE__EE_Registration__receipt_url__receipt_url', '', $this, $messenger, 'receipt');
+	}
+
+
+	/**
+	 * Gets the string which represents the URL trigger for the invoice template in the message template system.
+	 *
+	 * @param string $messenger 'pdf' or 'html'.  Default 'html'.
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function invoice_url($messenger = 'html')
+	{
+		/**
+		 * The below will be deprecated one version after this.  We check first if there is a custom invoice template
+		 * already in use on old system.  If there is then we just return the standard url for it.
+		 *
+		 * @since 4.5.0
+		 */
+		$template_relative_path = 'modules/gateways/Invoice/lib/templates/invoice_body.template.php';
+		$has_custom = EEH_Template::locate_template(
+			$template_relative_path,
+			array(),
+			true,
+			true,
+			true
+		);
+
+		if ($has_custom) {
+			if ($messenger == 'html') {
+				return $this->invoice_url('launch');
+			}
+			$route = $messenger == 'download' || $messenger == 'pdf' ? 'download_invoice' : 'launch_invoice';
+
+			$query_args = array('ee' => $route, 'id' => $this->reg_url_link());
+			if ($messenger == 'html') {
+				$query_args['html'] = true;
+			}
+			return add_query_arg($query_args, get_permalink(EE_Registry::instance()->CFG->core->thank_you_page_id));
+		}
+		return apply_filters('FHEE__EE_Registration__invoice_url__invoice_url', '', $this, $messenger, 'invoice');
+	}
+
+
+	/**
+	 * get Registration URL Link
+	 *
+	 * @access public
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function reg_url_link()
+	{
+		return (string) $this->get('REG_url_link');
+	}
+
+
+	/**
+	 * Echoes out invoice_url()
+	 *
+	 * @param string $type 'download','launch', or 'html' (default is 'launch')
+	 * @return void
+	 * @throws EE_Error
+	 */
+	public function e_invoice_url($type = 'launch')
+	{
+		echo $this->invoice_url($type);
+	}
+
+
+	/**
+	 * Echoes out payment_overview_url
+	 */
+	public function e_payment_overview_url()
+	{
+		echo $this->payment_overview_url();
+	}
+
+
+	/**
+	 * Gets the URL for the checkout payment options reg step
+	 * with this registration's REG_url_link added as a query parameter
+	 *
+	 * @param bool $clear_session Set to true when you want to clear the session on revisiting the
+	 *                            payment overview url.
+	 * @return string
+	 * @throws InvalidInterfaceException
+	 * @throws InvalidDataTypeException
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 */
+	public function payment_overview_url($clear_session = false)
+	{
+		return add_query_arg(
+			(array) apply_filters(
+				'FHEE__EE_Registration__payment_overview_url__query_args',
+				array(
+					'e_reg_url_link' => $this->reg_url_link(),
+					'step'           => 'payment_options',
+					'revisit'        => true,
+					'clear_session'  => (bool) $clear_session,
+				),
+				$this
+			),
+			EE_Registry::instance()->CFG->core->reg_page_url()
+		);
+	}
+
+
+	/**
+	 * Gets the URL for the checkout attendee information reg step
+	 * with this registration's REG_url_link added as a query parameter
+	 *
+	 * @return string
+	 * @throws InvalidInterfaceException
+	 * @throws InvalidDataTypeException
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 */
+	public function edit_attendee_information_url()
+	{
+		return add_query_arg(
+			(array) apply_filters(
+				'FHEE__EE_Registration__edit_attendee_information_url__query_args',
+				array(
+					'e_reg_url_link' => $this->reg_url_link(),
+					'step'           => 'attendee_information',
+					'revisit'        => true,
+				),
+				$this
+			),
+			EE_Registry::instance()->CFG->core->reg_page_url()
+		);
+	}
+
+
+	/**
+	 * Simply generates and returns the appropriate admin_url link to edit this registration
+	 *
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function get_admin_edit_url()
+	{
+		return EEH_URL::add_query_args_and_nonce(
+			array(
+				'page'    => 'espresso_registrations',
+				'action'  => 'view_registration',
+				'_REG_ID' => $this->ID(),
+			),
+			admin_url('admin.php')
+		);
+	}
+
+
+	/**
+	 *    is_primary_registrant?
+	 */
+	public function is_primary_registrant()
+	{
+		return $this->get('REG_count') === 1 ? true : false;
+	}
+
+
+	/**
+	 * This returns the primary registration object for this registration group (which may be this object).
+	 *
+	 * @return EE_Registration
+	 * @throws EE_Error
+	 */
+	public function get_primary_registration()
+	{
+		if ($this->is_primary_registrant()) {
+			return $this;
+		}
+
+		// k reg_count !== 1 so let's get the EE_Registration object matching this txn_id and reg_count == 1
+		/** @var EE_Registration $primary_registrant */
+		$primary_registrant = EEM_Registration::instance()->get_one(
+			array(
+				array(
+					'TXN_ID'    => $this->transaction_ID(),
+					'REG_count' => 1,
+				),
+			)
+		);
+		return $primary_registrant;
+	}
+
+
+	/**
+	 *        get  Attendee Number
+	 *
+	 * @access        public
+	 */
+	public function count()
+	{
+		return $this->get('REG_count');
+	}
+
+
+	/**
+	 *        get Group Size
+	 */
+	public function group_size()
+	{
+		return $this->get('REG_group_size');
+	}
+
+
+	/**
+	 *        get Registration Date
+	 */
+	public function date()
+	{
+		return $this->get('REG_date');
+	}
+
+
+	/**
+	 * gets a pretty date
+	 *
+	 * @param string $date_format
+	 * @param string $time_format
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function pretty_date($date_format = null, $time_format = null)
+	{
+		return $this->get_datetime('REG_date', $date_format, $time_format);
+	}
+
+
+	/**
+	 * final_price
+	 * the registration's share of the transaction total, so that the
+	 * sum of all the transaction's REG_final_prices equal the transaction's total
+	 *
+	 * @return float
+	 * @throws EE_Error
+	 */
+	public function final_price()
+	{
+		return $this->get('REG_final_price');
+	}
+
+
+	/**
+	 * pretty_final_price
+	 *  final price as formatted string, with correct decimal places and currency symbol
+	 *
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function pretty_final_price()
+	{
+		return $this->get_pretty('REG_final_price');
+	}
+
+
+	/**
+	 * get paid (yeah)
+	 *
+	 * @return float
+	 * @throws EE_Error
+	 */
+	public function paid()
+	{
+		return $this->get('REG_paid');
+	}
+
+
+	/**
+	 * pretty_paid
+	 *
+	 * @return float
+	 * @throws EE_Error
+	 */
+	public function pretty_paid()
+	{
+		return $this->get_pretty('REG_paid');
+	}
+
+
+	/**
+	 * owes_monies_and_can_pay
+	 * whether or not this registration has monies owing and it's' status allows payment
+	 *
+	 * @param array $requires_payment
+	 * @return bool
+	 * @throws EE_Error
+	 */
+	public function owes_monies_and_can_pay($requires_payment = array())
+	{
+		// these reg statuses require payment (if event is not free)
+		$requires_payment = ! empty($requires_payment)
+			? $requires_payment
+			: EEM_Registration::reg_statuses_that_allow_payment();
+		if (in_array($this->status_ID(), $requires_payment) &&
+			$this->final_price() != 0 &&
+			$this->final_price() != $this->paid()
+		) {
+			return true;
+		} else {
+			return false;
+		}
+	}
+
+
+	/**
+	 * Prints out the return value of $this->pretty_status()
+	 *
+	 * @param bool $show_icons
+	 * @return void
+	 * @throws EE_Error
+	 */
+	public function e_pretty_status($show_icons = false)
+	{
+		echo $this->pretty_status($show_icons);
+	}
+
+
+	/**
+	 * Returns a nice version of the status for displaying to customers
+	 *
+	 * @param bool $show_icons
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function pretty_status($show_icons = false)
+	{
+		$status = EEM_Status::instance()->localized_status(
+			array($this->status_ID() => esc_html__('unknown', 'event_espresso')),
+			false,
+			'sentence'
+		);
+		$icon = '';
+		switch ($this->status_ID()) {
+			case EEM_Registration::status_id_approved:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-star-filled ee-icon-size-16 green-text"></span>'
+					: '';
+				break;
+			case EEM_Registration::status_id_pending_payment:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-star-half ee-icon-size-16 orange-text"></span>'
+					: '';
+				break;
+			case EEM_Registration::status_id_not_approved:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-marker ee-icon-size-16 orange-text"></span>'
+					: '';
+				break;
+			case EEM_Registration::status_id_cancelled:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-no ee-icon-size-16 lt-grey-text"></span>'
+					: '';
+				break;
+			case EEM_Registration::status_id_incomplete:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-no ee-icon-size-16 lt-orange-text"></span>'
+					: '';
+				break;
+			case EEM_Registration::status_id_declined:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-no ee-icon-size-16 red-text"></span>'
+					: '';
+				break;
+			case EEM_Registration::status_id_wait_list:
+				$icon = $show_icons
+					? '<span class="dashicons dashicons-clipboard ee-icon-size-16 purple-text"></span>'
+					: '';
+				break;
+		}
+		return $icon . $status[ $this->status_ID() ];
+	}
+
+
+	/**
+	 *        get Attendee Is Going
+	 */
+	public function att_is_going()
+	{
+		return $this->get('REG_att_is_going');
+	}
+
+
+	/**
+	 * Gets related answers
+	 *
+	 * @param array $query_params @see https://github.com/eventespresso/event-espresso-core/tree/master/docs/G--Model-System/model-query-params.md
+	 * @return EE_Answer[]
+	 * @throws EE_Error
+	 */
+	public function answers($query_params = null)
+	{
+		return $this->get_many_related('Answer', $query_params);
+	}
+
+
+	/**
+	 * Gets the registration's answer value to the specified question
+	 * (either the question's ID or a question object)
+	 *
+	 * @param EE_Question|int $question
+	 * @param bool            $pretty_value
+	 * @return array|string if pretty_value= true, the result will always be a string
+	 * (because the answer might be an array of answer values, so passing pretty_value=true
+	 * will convert it into some kind of string)
+	 * @throws EE_Error
+	 */
+	public function answer_value_to_question($question, $pretty_value = true)
+	{
+		$question_id = EEM_Question::instance()->ensure_is_ID($question);
+		return EEM_Answer::instance()->get_answer_value_to_question($this, $question_id, $pretty_value);
+	}
+
+
+	/**
+	 * question_groups
+	 * returns an array of EE_Question_Group objects for this registration
+	 *
+	 * @return EE_Question_Group[]
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public function question_groups()
+	{
+		return EEM_Event::instance()->get_question_groups_for_event($this->event_ID(), $this);
+	}
+
+
+	/**
+	 * count_question_groups
+	 * returns a count of the number of EE_Question_Group objects for this registration
+	 *
+	 * @return int
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public function count_question_groups()
+	{
+		return EEM_Event::instance()->count_related(
+			$this->event_ID(),
+			'Question_Group',
+			[
+				[
+					'Event_Question_Group.'
+					. EEM_Event_Question_Group::instance()->fieldNameForContext($this->is_primary_registrant()) => true,
+				]
+			]
+		);
+	}
+
+
+	/**
+	 * Returns the registration date in the 'standard' string format
+	 * (function may be improved in the future to allow for different formats and timezones)
+	 *
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function reg_date()
+	{
+		return $this->get_datetime('REG_date');
+	}
+
+
+	/**
+	 * Gets the datetime-ticket for this registration (ie, it can be used to isolate
+	 * the ticket this registration purchased, or the datetime they have registered
+	 * to attend)
+	 *
+	 * @return EE_Datetime_Ticket
+	 * @throws EE_Error
+	 */
+	public function datetime_ticket()
+	{
+		return $this->get_first_related('Datetime_Ticket');
+	}
+
+
+	/**
+	 * Sets the registration's datetime_ticket.
+	 *
+	 * @param EE_Datetime_Ticket $datetime_ticket
+	 * @return EE_Datetime_Ticket
+	 * @throws EE_Error
+	 */
+	public function set_datetime_ticket($datetime_ticket)
+	{
+		return $this->_add_relation_to($datetime_ticket, 'Datetime_Ticket');
+	}
+
+	/**
+	 * Gets deleted
+	 *
+	 * @return bool
+	 * @throws EE_Error
+	 */
+	public function deleted()
+	{
+		return $this->get('REG_deleted');
+	}
+
+	/**
+	 * Sets deleted
+	 *
+	 * @param boolean $deleted
+	 * @return bool
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_deleted($deleted)
+	{
+		if ($deleted) {
+			$this->delete();
+		} else {
+			$this->restore();
+		}
+	}
+
+
+	/**
+	 * Get the status object of this object
+	 *
+	 * @return EE_Status
+	 * @throws EE_Error
+	 */
+	public function status_obj()
+	{
+		return $this->get_first_related('Status');
+	}
+
+
+	/**
+	 * Returns the number of times this registration has checked into any of the datetimes
+	 * its available for
+	 *
+	 * @return int
+	 * @throws EE_Error
+	 */
+	public function count_checkins()
+	{
+		return $this->get_model()->count_related($this, 'Checkin');
+	}
+
+
+	/**
+	 * Returns the number of current Check-ins this registration is checked into for any of the datetimes the
+	 * registration is for.  Note, this is ONLY checked in (does not include checkedout)
+	 *
+	 * @return int
+	 * @throws EE_Error
+	 */
+	public function count_checkins_not_checkedout()
+	{
+		return $this->get_model()->count_related($this, 'Checkin', array(array('CHK_in' => 1)));
+	}
+
+
+	/**
+	 * The purpose of this method is simply to check whether this registration can checkin to the given datetime.
+	 *
+	 * @param int | EE_Datetime $DTT_OR_ID      The datetime the registration is being checked against
+	 * @param bool              $check_approved This is used to indicate whether the caller wants can_checkin to also
+	 *                                          consider registration status as well as datetime access.
+	 * @return bool
+	 * @throws EE_Error
+	 */
+	public function can_checkin($DTT_OR_ID, $check_approved = true)
+	{
+		$DTT_ID = EEM_Datetime::instance()->ensure_is_ID($DTT_OR_ID);
+
+		// first check registration status
+		if (($check_approved && ! $this->is_approved()) || ! $DTT_ID) {
+			return false;
+		}
+		// is there a datetime ticket that matches this dtt_ID?
+		if (! (EEM_Datetime_Ticket::instance()->exists(
+			array(
+				array(
+					'TKT_ID' => $this->get('TKT_ID'),
+					'DTT_ID' => $DTT_ID,
+				),
+			)
+		))
+		) {
+			return false;
+		}
+
+		// final check is against TKT_uses
+		return $this->verify_can_checkin_against_TKT_uses($DTT_ID);
+	}
+
+
+	/**
+	 * This method verifies whether the user can checkin for the given datetime considering the max uses value set on
+	 * the ticket. To do this,  a query is done to get the count of the datetime records already checked into.  If the
+	 * datetime given does not have a check-in record and checking in for that datetime will exceed the allowed uses,
+	 * then return false.  Otherwise return true.
+	 *
+	 * @param int | EE_Datetime $DTT_OR_ID The datetime the registration is being checked against
+	 * @return bool true means can checkin.  false means cannot checkin.
+	 * @throws EE_Error
+	 */
+	public function verify_can_checkin_against_TKT_uses($DTT_OR_ID)
+	{
+		$DTT_ID = EEM_Datetime::instance()->ensure_is_ID($DTT_OR_ID);
+
+		if (! $DTT_ID) {
+			return false;
+		}
+
+		$max_uses = $this->ticket() instanceof EE_Ticket ? $this->ticket()->uses() : EE_INF;
+
+		// if max uses is not set or equals infinity then return true cause its not a factor for whether user can
+		// check-in or not.
+		if (! $max_uses || $max_uses === EE_INF) {
+			return true;
+		}
+
+		// does this datetime have a checkin record?  If so, then the dtt count has already been verified so we can just
+		// go ahead and toggle.
+		if (EEM_Checkin::instance()->exists(array(array('REG_ID' => $this->ID(), 'DTT_ID' => $DTT_ID)))) {
+			return true;
+		}
+
+		// made it here so the last check is whether the number of checkins per unique datetime on this registration
+		// disallows further check-ins.
+		$count_unique_dtt_checkins = EEM_Checkin::instance()->count(
+			array(
+				array(
+					'REG_ID' => $this->ID(),
+					'CHK_in' => true,
+				),
+			),
+			'DTT_ID',
+			true
+		);
+		// checkins have already reached their max number of uses
+		// so registrant can NOT checkin
+		if ($count_unique_dtt_checkins >= $max_uses) {
+			EE_Error::add_error(
+				esc_html__(
+					'Check-in denied because number of datetime uses for the ticket has been reached or exceeded.',
+					'event_espresso'
+				),
+				__FILE__,
+				__FUNCTION__,
+				__LINE__
+			);
+			return false;
+		}
+		return true;
+	}
+
+
+	/**
+	 * toggle Check-in status for this registration
+	 * Check-ins are toggled in the following order:
+	 * never checked in -> checked in
+	 * checked in -> checked out
+	 * checked out -> checked in
+	 *
+	 * @param  int $DTT_ID  include specific datetime to toggle Check-in for.
+	 *                      If not included or null, then it is assumed latest datetime is being toggled.
+	 * @param bool $verify  If true then can_checkin() is used to verify whether the person
+	 *                      can be checked in or not.  Otherwise this forces change in checkin status.
+	 * @return bool|int     the chk_in status toggled to OR false if nothing got changed.
+	 * @throws EE_Error
+	 */
+	public function toggle_checkin_status($DTT_ID = null, $verify = false)
+	{
+		if (empty($DTT_ID)) {
+			$datetime = $this->get_latest_related_datetime();
+			$DTT_ID = $datetime instanceof EE_Datetime ? $datetime->ID() : 0;
+			// verify the registration can checkin for the given DTT_ID
+		} elseif (! $this->can_checkin($DTT_ID, $verify)) {
+			EE_Error::add_error(
+				sprintf(
+					esc_html__(
+						'The given registration (ID:%1$d) can not be checked in to the given DTT_ID (%2$d), because the registration does not have access',
+						'event_espresso'
+					),
+					$this->ID(),
+					$DTT_ID
+				),
+				__FILE__,
+				__FUNCTION__,
+				__LINE__
+			);
+			return false;
+		}
+		$status_paths = array(
+			EE_Checkin::status_checked_never => EE_Checkin::status_checked_in,
+			EE_Checkin::status_checked_in    => EE_Checkin::status_checked_out,
+			EE_Checkin::status_checked_out   => EE_Checkin::status_checked_in,
+		);
+		// start by getting the current status so we know what status we'll be changing to.
+		$cur_status = $this->check_in_status_for_datetime($DTT_ID, null);
+		$status_to = $status_paths[ $cur_status ];
+		// database only records true for checked IN or false for checked OUT
+		// no record ( null ) means checked in NEVER, but we obviously don't save that
+		$new_status = $status_to === EE_Checkin::status_checked_in ? true : false;
+		// add relation - note Check-ins are always creating new rows
+		// because we are keeping track of Check-ins over time.
+		// Eventually we'll probably want to show a list table
+		// for the individual Check-ins so that they can be managed.
+		$checkin = EE_Checkin::new_instance(
+			array(
+				'REG_ID' => $this->ID(),
+				'DTT_ID' => $DTT_ID,
+				'CHK_in' => $new_status,
+			)
+		);
+		// if the record could not be saved then return false
+		if ($checkin->save() === 0) {
+			if (WP_DEBUG) {
+				global $wpdb;
+				$error = sprintf(
+					esc_html__(
+						'Registration check in update failed because of the following database error: %1$s%2$s',
+						'event_espresso'
+					),
+					'<br />',
+					$wpdb->last_error
+				);
+			} else {
+				$error = esc_html__(
+					'Registration check in update failed because of an unknown database error',
+					'event_espresso'
+				);
+			}
+			EE_Error::add_error($error, __FILE__, __FUNCTION__, __LINE__);
+			return false;
+		}
+		// Fire a checked_in and checkout_out action.
+		$checked_status = $status_to === EE_Checkin::status_checked_in ? 'checked_in' : 'checked_out';
+		do_action('AHEE__EE_Registration__toggle_checkin_status__{$checked_status}', $this, $DTT_ID);
+		return $status_to;
+	}
+
+
+	/**
+	 * Returns the latest datetime related to this registration (via the ticket attached to the registration).
+	 * "Latest" is defined by the `DTT_EVT_start` column.
+	 *
+	 * @return EE_Datetime|null
+	 * @throws EE_Error
+	 */
+	public function get_latest_related_datetime()
+	{
+		return EEM_Datetime::instance()->get_one(
+			array(
+				array(
+					'Ticket.Registration.REG_ID' => $this->ID(),
+				),
+				'order_by' => array('DTT_EVT_start' => 'DESC'),
+			)
+		);
+	}
+
+
+	/**
+	 * Returns the earliest datetime related to this registration (via the ticket attached to the registration).
+	 * "Earliest" is defined by the `DTT_EVT_start` column.
+	 *
+	 * @throws EE_Error
+	 */
+	public function get_earliest_related_datetime()
+	{
+		return EEM_Datetime::instance()->get_one(
+			array(
+				array(
+					'Ticket.Registration.REG_ID' => $this->ID(),
+				),
+				'order_by' => array('DTT_EVT_start' => 'ASC'),
+			)
+		);
+	}
+
+
+	/**
+	 * This method simply returns the check-in status for this registration and the given datetime.
+	 * If neither the datetime nor the checkin values are provided as arguments,
+	 * then this will return the LATEST check-in status for the registration across all datetimes it belongs to.
+	 *
+	 * @param  int       $DTT_ID  The ID of the datetime we're checking against
+	 *                            (if empty we'll get the primary datetime for
+	 *                            this registration (via event) and use it's ID);
+	 * @param EE_Checkin $checkin If present, we use the given checkin object rather than the dtt_id.
+	 *
+	 * @return int                Integer representing Check-in status.
+	 * @throws EE_Error
+	 */
+	public function check_in_status_for_datetime($DTT_ID = 0, $checkin = null)
+	{
+		$checkin_query_params = array(
+			'order_by' => array('CHK_timestamp' => 'DESC'),
+		);
+
+		if ($DTT_ID > 0) {
+			$checkin_query_params[0] = array('DTT_ID' => $DTT_ID);
+		}
+
+		// get checkin object (if exists)
+		$checkin = $checkin instanceof EE_Checkin
+			? $checkin
+			: $this->get_first_related('Checkin', $checkin_query_params);
+		if ($checkin instanceof EE_Checkin) {
+			if ($checkin->get('CHK_in')) {
+				return EE_Checkin::status_checked_in; // checked in
+			}
+			return EE_Checkin::status_checked_out; // had checked in but is now checked out.
+		}
+		return EE_Checkin::status_checked_never; // never been checked in
+	}
+
+
+	/**
+	 * This method returns a localized message for the toggled Check-in message.
+	 *
+	 * @param  int $DTT_ID include specific datetime to get the correct Check-in message.  If not included or null,
+	 *                     then it is assumed Check-in for primary datetime was toggled.
+	 * @param bool $error  This just flags that you want an error message returned. This is put in so that the error
+	 *                     message can be customized with the attendee name.
+	 * @return string internationalized message
+	 * @throws EE_Error
+	 */
+	public function get_checkin_msg($DTT_ID, $error = false)
+	{
+		// let's get the attendee first so we can include the name of the attendee
+		$attendee = $this->get_first_related('Attendee');
+		if ($attendee instanceof EE_Attendee) {
+			if ($error) {
+				return sprintf(__("%s's check-in status was not changed.", "event_espresso"), $attendee->full_name());
+			}
+			$cur_status = $this->check_in_status_for_datetime($DTT_ID);
+			// what is the status message going to be?
+			switch ($cur_status) {
+				case EE_Checkin::status_checked_never:
+					return sprintf(
+						__("%s has been removed from Check-in records", "event_espresso"),
+						$attendee->full_name()
+					);
+					break;
+				case EE_Checkin::status_checked_in:
+					return sprintf(__('%s has been checked in', 'event_espresso'), $attendee->full_name());
+					break;
+				case EE_Checkin::status_checked_out:
+					return sprintf(__('%s has been checked out', 'event_espresso'), $attendee->full_name());
+					break;
+			}
+		}
+		return esc_html__("The check-in status could not be determined.", "event_espresso");
+	}
+
+
+	/**
+	 * Returns the related EE_Transaction to this registration
+	 *
+	 * @return EE_Transaction
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 */
+	public function transaction()
+	{
+		$transaction = $this->get_first_related('Transaction');
+		if (! $transaction instanceof \EE_Transaction) {
+			throw new EntityNotFoundException('Transaction ID', $this->transaction_ID());
+		}
+		return $transaction;
+	}
+
+
+	/**
+	 *        get Registration Code
+	 */
+	public function reg_code()
+	{
+		return $this->get('REG_code');
+	}
+
+
+	/**
+	 *        get Transaction ID
+	 */
+	public function transaction_ID()
+	{
+		return $this->get('TXN_ID');
+	}
+
+
+	/**
+	 * @return int
+	 * @throws EE_Error
+	 */
+	public function ticket_ID()
+	{
+		return $this->get('TKT_ID');
+	}
+
+
+	/**
+	 *        Set Registration Code
+	 *
+	 * @access    public
+	 * @param    string  $REG_code Registration Code
+	 * @param    boolean $use_default
+	 * @throws EE_Error
+	 */
+	public function set_reg_code($REG_code, $use_default = false)
+	{
+		if (empty($REG_code)) {
+			EE_Error::add_error(
+				esc_html__('REG_code can not be empty.', 'event_espresso'),
+				__FILE__,
+				__FUNCTION__,
+				__LINE__
+			);
+			return;
+		}
+		if (! $this->reg_code()) {
+			parent::set('REG_code', $REG_code, $use_default);
+		} else {
+			EE_Error::doing_it_wrong(
+				__CLASS__ . '::' . __FUNCTION__,
+				esc_html__('Can not change a registration REG_code once it has been set.', 'event_espresso'),
+				'4.6.0'
+			);
+		}
+	}
+
+
+	/**
+	 * Returns all other registrations in the same group as this registrant who have the same ticket option.
+	 * Note, if you want to just get all registrations in the same transaction (group), use:
+	 *    $registration->transaction()->registrations();
+	 *
+	 * @since 4.5.0
+	 * @return EE_Registration[] or empty array if this isn't a group registration.
+	 * @throws EE_Error
+	 */
+	public function get_all_other_registrations_in_group()
+	{
+		if ($this->group_size() < 2) {
+			return array();
+		}
+
+		$query[0] = array(
+			'TXN_ID' => $this->transaction_ID(),
+			'REG_ID' => array('!=', $this->ID()),
+			'TKT_ID' => $this->ticket_ID(),
+		);
+		/** @var EE_Registration[] $registrations */
+		$registrations = $this->get_model()->get_all($query);
+		return $registrations;
+	}
+
+	/**
+	 * Return the link to the admin details for the object.
+	 *
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function get_admin_details_link()
+	{
+		EE_Registry::instance()->load_helper('URL');
+		return EEH_URL::add_query_args_and_nonce(
+			array(
+				'page'    => 'espresso_registrations',
+				'action'  => 'view_registration',
+				'_REG_ID' => $this->ID(),
+			),
+			admin_url('admin.php')
+		);
+	}
+
+	/**
+	 * Returns the link to the editor for the object.  Sometimes this is the same as the details.
+	 *
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function get_admin_edit_link()
+	{
+		return $this->get_admin_details_link();
+	}
+
+	/**
+	 * Returns the link to a settings page for the object.
+	 *
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function get_admin_settings_link()
+	{
+		return $this->get_admin_details_link();
+	}
+
+	/**
+	 * Returns the link to the "overview" for the object (typically the "list table" view).
+	 *
+	 * @return string
+	 */
+	public function get_admin_overview_link()
+	{
+		EE_Registry::instance()->load_helper('URL');
+		return EEH_URL::add_query_args_and_nonce(
+			array(
+				'page' => 'espresso_registrations',
+			),
+			admin_url('admin.php')
+		);
+	}
+
+
+	/**
+	 * @param array $query_params
+	 *
+	 * @return \EE_Registration[]
+	 * @throws EE_Error
+	 */
+	public function payments($query_params = array())
+	{
+		return $this->get_many_related('Payment', $query_params);
+	}
+
+
+	/**
+	 * @param array $query_params
+	 *
+	 * @return \EE_Registration_Payment[]
+	 * @throws EE_Error
+	 */
+	public function registration_payments($query_params = array())
+	{
+		return $this->get_many_related('Registration_Payment', $query_params);
+	}
+
+
+	/**
+	 * This grabs the payment method corresponding to the last payment made for the amount owing on the registration.
+	 * Note: if there are no payments on the registration there will be no payment method returned.
+	 *
+	 * @return EE_Payment_Method|null
+	 */
+	public function payment_method()
+	{
+		return EEM_Payment_Method::instance()->get_last_used_for_registration($this);
+	}
+
+
+	/**
+	 * @return \EE_Line_Item
+	 * @throws EntityNotFoundException
+	 * @throws EE_Error
+	 */
+	public function ticket_line_item()
+	{
+		$ticket = $this->ticket();
+		$transaction = $this->transaction();
+		$line_item = null;
+		$ticket_line_items = \EEH_Line_Item::get_line_items_by_object_type_and_IDs(
+			$transaction->total_line_item(),
+			'Ticket',
+			array($ticket->ID())
+		);
+		foreach ($ticket_line_items as $ticket_line_item) {
+			if ($ticket_line_item instanceof \EE_Line_Item
+				&& $ticket_line_item->OBJ_type() === 'Ticket'
+				&& $ticket_line_item->OBJ_ID() === $ticket->ID()
+			) {
+				$line_item = $ticket_line_item;
+				break;
+			}
+		}
+		if (! ($line_item instanceof \EE_Line_Item && $line_item->OBJ_type() === 'Ticket')) {
+			throw new EntityNotFoundException('Line Item Ticket ID', $ticket->ID());
+		}
+		return $line_item;
+	}
+
+
+	/**
+	 * Soft Deletes this model object.
+	 *
+	 * @return boolean | int
+	 * @throws RuntimeException
+	 * @throws EE_Error
+	 */
+	public function delete()
+	{
+		if ($this->update_extra_meta(EE_Registration::PRE_TRASH_REG_STATUS_KEY, $this->status_ID()) === true) {
+			$this->set_status(EEM_Registration::status_id_cancelled);
+		}
+		return parent::delete();
+	}
+
+
+	/**
+	 * Restores whatever the previous status was on a registration before it was trashed (if possible)
+	 *
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function restore()
+	{
+		$previous_status = $this->get_extra_meta(
+			EE_Registration::PRE_TRASH_REG_STATUS_KEY,
+			true,
+			EEM_Registration::status_id_cancelled
+		);
+		if ($previous_status) {
+			$this->delete_extra_meta(EE_Registration::PRE_TRASH_REG_STATUS_KEY);
+			$this->set_status($previous_status);
+		}
+		return parent::restore();
+	}
+
+
+	/**
+	 * possibly toggle Registration status based on comparison of REG_paid vs REG_final_price
+	 *
+	 * @param  boolean $trigger_set_status_logic EE_Registration::set_status() can trigger additional logic
+	 *                                           depending on whether the reg status changes to or from "Approved"
+	 * @return boolean whether the Registration status was updated
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function updateStatusBasedOnTotalPaid($trigger_set_status_logic = true)
+	{
+		$paid = $this->paid();
+		$price = $this->final_price();
+		switch (true) {
+			// overpaid or paid
+			case EEH_Money::compare_floats($paid, $price, '>'):
+			case EEH_Money::compare_floats($paid, $price):
+				$new_status = EEM_Registration::status_id_approved;
+				break;
+			//  underpaid
+			case EEH_Money::compare_floats($paid, $price, '<'):
+				$new_status = EEM_Registration::status_id_pending_payment;
+				break;
+			// uhhh Houston...
+			default:
+				throw new RuntimeException(
+					esc_html__('The total paid calculation for this registration is inaccurate.', 'event_espresso')
+				);
+		}
+		if ($new_status !== $this->status_ID()) {
+			if ($trigger_set_status_logic) {
+				return $this->set_status($new_status);
+			}
+			parent::set('STS_ID', $new_status);
+			return true;
+		}
+		return false;
+	}
+
+
+	/*************************** DEPRECATED ***************************/
+
+
+	/**
+	 * @deprecated
+	 * @since     4.7.0
+	 * @access    public
+	 */
+	public function price_paid()
+	{
+		EE_Error::doing_it_wrong(
+			'EE_Registration::price_paid()',
+			esc_html__(
+				'This method is deprecated, please use EE_Registration::final_price() instead.',
+				'event_espresso'
+			),
+			'4.7.0'
+		);
+		return $this->final_price();
+	}
+
+
+	/**
+	 * @deprecated
+	 * @since     4.7.0
+	 * @access    public
+	 * @param    float $REG_final_price
+	 * @throws EE_Error
+	 * @throws RuntimeException
+	 */
+	public function set_price_paid($REG_final_price = 0.00)
+	{
+		EE_Error::doing_it_wrong(
+			'EE_Registration::set_price_paid()',
+			esc_html__(
+				'This method is deprecated, please use EE_Registration::set_final_price() instead.',
+				'event_espresso'
+			),
+			'4.7.0'
+		);
+		$this->set_final_price($REG_final_price);
+	}
+
+
+	/**
+	 * @deprecated
+	 * @since 4.7.0
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public function pretty_price_paid()
+	{
+		EE_Error::doing_it_wrong(
+			'EE_Registration::pretty_price_paid()',
+			esc_html__(
+				'This method is deprecated, please use EE_Registration::pretty_final_price() instead.',
+				'event_espresso'
+			),
+			'4.7.0'
+		);
+		return $this->pretty_final_price();
+	}
+
+
+	/**
+	 * Gets the primary datetime related to this registration via the related Event to this registration
+	 *
+	 * @deprecated 4.9.17
+	 * @return EE_Datetime
+	 * @throws EE_Error
+	 * @throws EntityNotFoundException
+	 */
+	public function get_related_primary_datetime()
+	{
+		EE_Error::doing_it_wrong(
+			__METHOD__,
+			esc_html__(
+				'Use EE_Registration::get_latest_related_datetime() or EE_Registration::get_earliest_related_datetime()',
+				'event_espresso'
+			),
+			'4.9.17',
+			'5.0.0'
+		);
+		return $this->event()->primary_datetime();
+	}
 }