eventespresso / event-espresso-core

core/helpers/EEH_Line_Item.helper.php

Spacing +36 added lines, -36 removed lines

@@ -138,7 +138,7 @@ 
      */
     public static function add_ticket_purchase(EE_Line_Item $total_line_item, EE_Ticket $ticket, $qty = 1)
     {
-        if (! $total_line_item instanceof EE_Line_Item || ! $total_line_item->is_total()) {
+        if ( ! $total_line_item instanceof EE_Line_Item || ! $total_line_item->is_total()) {
             throw new EE_Error(
                 sprintf(
                     esc_html__(
@@ -153,7 +153,7 @@ 
         // either increment the qty for an existing ticket
         $line_item = self::increment_ticket_qty_if_already_in_cart($total_line_item, $ticket, $qty);
         // or add a new one
-        if (! $line_item instanceof EE_Line_Item) {
+        if ( ! $line_item instanceof EE_Line_Item) {
             $line_item = self::create_ticket_line_item($total_line_item, $ticket, $qty);
         }
         $total_line_item->recalculate_total_including_taxes();
@@ -214,7 +214,7 @@ 
      */
     public static function increment_quantity(EE_Line_Item $line_item, $qty = 1)
     {
-        if (! $line_item->is_percent()) {
+        if ( ! $line_item->is_percent()) {
             $qty += $line_item->quantity();
             $line_item->set_quantity($qty);
             $line_item->set_total($line_item->unit_price() * $qty);
@@ -243,7 +243,7 @@ 
      */
     public static function decrement_quantity(EE_Line_Item $line_item, $qty = 1)
     {
-        if (! $line_item->is_percent()) {
+        if ( ! $line_item->is_percent()) {
             $qty = $line_item->quantity() - $qty;
             $qty = max($qty, 0);
             $line_item->set_quantity($qty);
@@ -272,7 +272,7 @@ 
      */
     public static function update_quantity(EE_Line_Item $line_item, $new_quantity)
     {
-        if (! $line_item->is_percent()) {
+        if ( ! $line_item->is_percent()) {
             $line_item->set_quantity($new_quantity);
             $line_item->set_total($line_item->unit_price() * $new_quantity);
             $line_item->save();
@@ -312,7 +312,7 @@ 
         // add $ticket to cart
         $line_item = EE_Line_Item::new_instance(array(
             'LIN_name'       => $ticket->name(),
-            'LIN_desc'       => $ticket->description() !== '' ? $ticket->description() . ' ' . $event : $event,
+            'LIN_desc'       => $ticket->description() !== '' ? $ticket->description().' '.$event : $event,
             'LIN_unit_price' => $ticket->price(),
             'LIN_quantity'   => $qty,
             'LIN_is_taxable' => $ticket->taxable(),
@@ -462,7 +462,7 @@ 
                         'event_espresso'
                     ),
                     $ticket_line_item->name(),
-                    current_time(get_option('date_format') . ' ' . get_option('time_format'))
+                    current_time(get_option('date_format').' '.get_option('time_format'))
                 ),
                 'LIN_unit_price' => 0, // $ticket_line_item->unit_price()
                 'LIN_quantity'   => $qty,
@@ -524,7 +524,7 @@ 
         );
         $cancellation_line_item = reset($cancellation_line_item);
         // verify that this ticket was indeed previously cancelled
-        if (! $cancellation_line_item instanceof EE_Line_Item) {
+        if ( ! $cancellation_line_item instanceof EE_Line_Item) {
             return false;
         }
         if ($cancellation_line_item->quantity() > $qty) {
@@ -729,7 +729,7 @@ 
             'LIN_code'  => 'taxes',
             'LIN_name'  => esc_html__('Taxes', 'event_espresso'),
             'LIN_type'  => EEM_Line_Item::type_tax_sub_total,
-            'LIN_order' => 1000,// this should always come last
+            'LIN_order' => 1000, // this should always come last
         ));
         $tax_line_item = apply_filters(
             'FHEE__EEH_Line_Item__create_taxes_subtotal__tax_line_item',
@@ -785,7 +785,7 @@ 
      */
     public static function get_event_code($event)
     {
-        return 'event-' . ($event instanceof EE_Event ? $event->ID() : '0');
+        return 'event-'.($event instanceof EE_Event ? $event->ID() : '0');
     }
 
 
@@ -834,7 +834,7 @@ 
     public static function get_event_line_item_for_ticket(EE_Line_Item $grand_total, EE_Ticket $ticket)
     {
         $first_datetime = $ticket->first_datetime();
-        if (! $first_datetime instanceof EE_Datetime) {
+        if ( ! $first_datetime instanceof EE_Datetime) {
             throw new EE_Error(
                 sprintf(
                     __('The supplied ticket (ID %d) has no datetimes', 'event_espresso'),
@@ -843,7 +843,7 @@ 
             );
         }
         $event = $first_datetime->event();
-        if (! $event instanceof EE_Event) {
+        if ( ! $event instanceof EE_Event) {
             throw new EE_Error(
                 sprintf(
                     esc_html__(
@@ -855,7 +855,7 @@ 
             );
         }
         $events_sub_total = EEH_Line_Item::get_event_line_item($grand_total, $event);
-        if (! $events_sub_total instanceof EE_Line_Item) {
+        if ( ! $events_sub_total instanceof EE_Line_Item) {
             throw new EE_Error(
                 sprintf(
                     esc_html__(
@@ -891,7 +891,7 @@ 
         $found = false;
         foreach (EEH_Line_Item::get_event_subtotals($grand_total) as $event_line_item) {
             // default event subtotal, we should only ever find this the first time this method is called
-            if (! $event_line_item->OBJ_ID()) {
+            if ( ! $event_line_item->OBJ_ID()) {
                 // let's use this! but first... set the event details
                 EEH_Line_Item::set_event_subtotal_details($event_line_item, $event);
                 $found = true;
@@ -903,7 +903,7 @@ 
                 break;
             }
         }
-        if (! $found) {
+        if ( ! $found) {
             // there is no event sub-total yet, so add it
             $pre_tax_subtotal = EEH_Line_Item::get_pre_tax_subtotal($grand_total);
             // create a new "event" subtotal below that
@@ -1020,7 +1020,7 @@ 
     public static function ensure_taxes_applied($total_line_item)
     {
         $taxes_subtotal = self::get_taxes_subtotal($total_line_item);
-        if (! $taxes_subtotal->children()) {
+        if ( ! $taxes_subtotal->children()) {
             self::apply_taxes($total_line_item);
         }
         return $taxes_subtotal->total();
@@ -1087,7 +1087,7 @@ 
         do_action('AHEE_log', __FILE__, __FUNCTION__, '');
 
         // check if only a single line_item_id was passed
-        if (! empty($line_item_codes) && ! is_array($line_item_codes)) {
+        if ( ! empty($line_item_codes) && ! is_array($line_item_codes)) {
             // place single line_item_id in an array to appear as multiple line_item_ids
             $line_item_codes = array($line_item_codes);
         }
@@ -1194,7 +1194,7 @@ 
         if ($code_substring_for_whitelist !== null) {
             $whitelisted = strpos($line_item->code(), $code_substring_for_whitelist) !== false;
         }
-        if (! $whitelisted && $line_item->is_line_item()) {
+        if ( ! $whitelisted && $line_item->is_line_item()) {
             $line_item->set_is_taxable($taxable);
         }
         foreach ($line_item->children() as $child_line_item) {
@@ -1556,7 +1556,7 @@ 
     public static function visualize(EE_Line_Item $line_item, $indentation = 0)
     {
         echo defined('EE_TESTS_DIR') ? "\n" : '<br />';
-        if (! $indentation) {
+        if ( ! $indentation) {
             echo defined('EE_TESTS_DIR') ? "\n" : '<br />';
         }
         for ($i = 0; $i < $indentation; $i++) {
@@ -1567,12 +1567,12 @@ 
             if ($line_item->is_percent()) {
                 $breakdown = "{$line_item->percent()}%";
             } else {
-                $breakdown = '$' . "{$line_item->unit_price()} x {$line_item->quantity()}";
+                $breakdown = '$'."{$line_item->unit_price()} x {$line_item->quantity()}";
             }
         }
         echo $line_item->name();
         echo " [ ID:{$line_item->ID()} | qty:{$line_item->quantity()} ] {$line_item->type()} : ";
-        echo '$' . (string) $line_item->total();
+        echo '$'.(string) $line_item->total();
         if ($breakdown) {
             echo " ( {$breakdown} )";
         }
@@ -1660,8 +1660,8 @@ 
                         if ($line_item_id === 'taxable') {
                             continue;
                         }
-                        $taxable_total = $running_totals['taxable'][ $line_item_id ];
-                        $running_totals[ $line_item_id ] += ($taxable_total * $tax_percent_decimal);
+                        $taxable_total = $running_totals['taxable'][$line_item_id];
+                        $running_totals[$line_item_id] += ($taxable_total * $tax_percent_decimal);
                     }
                     break;
 
@@ -1669,7 +1669,7 @@ 
                     // ticket line items or ????
                     if ($child_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET) {
                         // kk it's a ticket
-                        if (isset($running_totals[ $child_line_item->ID() ])) {
+                        if (isset($running_totals[$child_line_item->ID()])) {
                             // huh? that shouldn't happen.
                             $running_totals['total'] += $child_line_item->total();
                         } else {
@@ -1680,18 +1680,18 @@ 
                                 $taxable_amount = 0;
                             }
                             // are we only calculating totals for some tickets?
-                            if (isset($billable_ticket_quantities[ $child_line_item->OBJ_ID() ])) {
-                                $quantity = $billable_ticket_quantities[ $child_line_item->OBJ_ID() ];
-                                $running_totals[ $child_line_item->ID() ] = $quantity
+                            if (isset($billable_ticket_quantities[$child_line_item->OBJ_ID()])) {
+                                $quantity = $billable_ticket_quantities[$child_line_item->OBJ_ID()];
+                                $running_totals[$child_line_item->ID()] = $quantity
                                     ? $child_line_item->unit_price()
                                     : 0;
-                                $running_totals['taxable'][ $child_line_item->ID() ] = $quantity
+                                $running_totals['taxable'][$child_line_item->ID()] = $quantity
                                     ? $taxable_amount
                                     : 0;
                             } else {
                                 $quantity = $child_line_item->quantity();
-                                $running_totals[ $child_line_item->ID() ] = $child_line_item->unit_price();
-                                $running_totals['taxable'][ $child_line_item->ID() ] = $taxable_amount;
+                                $running_totals[$child_line_item->ID()] = $child_line_item->unit_price();
+                                $running_totals['taxable'][$child_line_item->ID()] = $taxable_amount;
                             }
                             $running_totals['taxable']['total'] += $taxable_amount * $quantity;
                             $running_totals['total'] += $child_line_item->unit_price() * $quantity;
@@ -1711,12 +1711,12 @@ 
                             }
                             // update the running totals
                             // yes this actually even works for the running grand total!
-                            $running_totals[ $line_item_id ] =
+                            $running_totals[$line_item_id] =
                                 $line_items_percent_of_running_total * $this_running_total;
 
                             if ($child_line_item->is_taxable()) {
-                                $running_totals['taxable'][ $line_item_id ] =
-                                    $line_items_percent_of_running_total * $running_totals['taxable'][ $line_item_id ];
+                                $running_totals['taxable'][$line_item_id] =
+                                    $line_items_percent_of_running_total * $running_totals['taxable'][$line_item_id];
                             }
                         }
                     }
@@ -1749,8 +1749,8 @@ 
             );
         }
         // ok now find this new registration's final price
-        if (isset($final_prices_per_ticket_line_item[$total_line_item->ID() ][ $ticket_line_item->ID() ])) {
-            return $final_prices_per_ticket_line_item[$total_line_item ][ $ticket_line_item->ID() ];
+        if (isset($final_prices_per_ticket_line_item[$total_line_item->ID()][$ticket_line_item->ID()])) {
+            return $final_prices_per_ticket_line_item[$total_line_item][$ticket_line_item->ID()];
         }
         $message = sprintf(
             esc_html__(
@@ -1760,7 +1760,7 @@ 
             $ticket_line_item->ID()
         );
         if (WP_DEBUG) {
-            $message .= '<br>' . print_r($final_prices_per_ticket_line_item, true);
+            $message .= '<br>'.print_r($final_prices_per_ticket_line_item, true);
             throw new OutOfRangeException($message);
         }
         EE_Log::instance()->log(__CLASS__, __FUNCTION__, $message);

Indentation +2041 added lines, -2041 removed lines

@@ -21,2045 +21,2045 @@
 class EEH_Line_Item
 {
 
-    /**
-     * Adds a simple item (unrelated to any other model object) to the provided PARENT line item.
-     * Does NOT automatically re-calculate the line item totals or update the related transaction.
-     * You should call recalculate_total_including_taxes() on the grant total line item after this
-     * to update the subtotals, and EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
-     * to keep the registration final prices in-sync with the transaction's total.
-     *
-     * @param EE_Line_Item $parent_line_item
-     * @param string       $name
-     * @param float        $unit_price
-     * @param string       $description
-     * @param int          $quantity
-     * @param boolean      $taxable
-     * @param boolean      $code if set to a value, ensures there is only one line item with that code
-     * @return boolean success
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function add_unrelated_item(
-        EE_Line_Item $parent_line_item,
-        $name,
-        $unit_price,
-        $description = '',
-        $quantity = 1,
-        $taxable = false,
-        $code = null
-    ) {
-        $items_subtotal = self::get_pre_tax_subtotal($parent_line_item);
-        $line_item = EE_Line_Item::new_instance(array(
-            'LIN_name'       => $name,
-            'LIN_desc'       => $description,
-            'LIN_unit_price' => $unit_price,
-            'LIN_quantity'   => $quantity,
-            'LIN_percent'    => null,
-            'LIN_is_taxable' => $taxable,
-            'LIN_order'      => $items_subtotal instanceof EE_Line_Item ? count($items_subtotal->children()) : 0,
-            'LIN_total'      => (float) $unit_price * (int) $quantity,
-            'LIN_type'       => EEM_Line_Item::type_line_item,
-            'LIN_code'       => $code,
-        ));
-        $line_item = apply_filters(
-            'FHEE__EEH_Line_Item__add_unrelated_item__line_item',
-            $line_item,
-            $parent_line_item
-        );
-        return self::add_item($parent_line_item, $line_item);
-    }
-
-
-    /**
-     * Adds a simple item ( unrelated to any other model object) to the total line item,
-     * in the correct spot in the line item tree. Automatically
-     * re-calculates the line item totals and updates the related transaction. But
-     * DOES NOT automatically upgrade the transaction's registrations' final prices (which
-     * should probably change because of this).
-     * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
-     * after using this, to keep the registration final prices in-sync with the transaction's total.
-     *
-     * @param EE_Line_Item $parent_line_item
-     * @param string       $name
-     * @param float        $percentage_amount
-     * @param string       $description
-     * @param boolean      $taxable
-     * @return boolean success
-     * @throws EE_Error
-     */
-    public static function add_percentage_based_item(
-        EE_Line_Item $parent_line_item,
-        $name,
-        $percentage_amount,
-        $description = '',
-        $taxable = false
-    ) {
-        $line_item = EE_Line_Item::new_instance(array(
-            'LIN_name'       => $name,
-            'LIN_desc'       => $description,
-            'LIN_unit_price' => 0,
-            'LIN_percent'    => $percentage_amount,
-            'LIN_quantity'   => 1,
-            'LIN_is_taxable' => $taxable,
-            'LIN_total'      => (float) ($percentage_amount * ($parent_line_item->total() / 100)),
-            'LIN_type'       => EEM_Line_Item::type_line_item,
-            'LIN_parent'     => $parent_line_item->ID(),
-        ));
-        $line_item = apply_filters(
-            'FHEE__EEH_Line_Item__add_percentage_based_item__line_item',
-            $line_item
-        );
-        return $parent_line_item->add_child_line_item($line_item, false);
-    }
-
-
-    /**
-     * Returns the new line item created by adding a purchase of the ticket
-     * ensures that ticket line item is saved, and that cart total has been recalculated.
-     * If this ticket has already been purchased, just increments its count.
-     * Automatically re-calculates the line item totals and updates the related transaction. But
-     * DOES NOT automatically upgrade the transaction's registrations' final prices (which
-     * should probably change because of this).
-     * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
-     * after using this, to keep the registration final prices in-sync with the transaction's total.
-     *
-     * @param EE_Line_Item $total_line_item grand total line item of type EEM_Line_Item::type_total
-     * @param EE_Ticket    $ticket
-     * @param int          $qty
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function add_ticket_purchase(EE_Line_Item $total_line_item, EE_Ticket $ticket, $qty = 1)
-    {
-        if (! $total_line_item instanceof EE_Line_Item || ! $total_line_item->is_total()) {
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'A valid line item total is required in order to add tickets. A line item of type "%s" was passed.',
-                        'event_espresso'
-                    ),
-                    $ticket->ID(),
-                    $total_line_item->ID()
-                )
-            );
-        }
-        // either increment the qty for an existing ticket
-        $line_item = self::increment_ticket_qty_if_already_in_cart($total_line_item, $ticket, $qty);
-        // or add a new one
-        if (! $line_item instanceof EE_Line_Item) {
-            $line_item = self::create_ticket_line_item($total_line_item, $ticket, $qty);
-        }
-        $total_line_item->recalculate_total_including_taxes();
-        return $line_item;
-    }
-
-
-    /**
-     * Returns the new line item created by adding a purchase of the ticket
-     *
-     * @param EE_Line_Item $total_line_item
-     * @param EE_Ticket    $ticket
-     * @param int          $qty
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function increment_ticket_qty_if_already_in_cart(
-        EE_Line_Item $total_line_item,
-        EE_Ticket $ticket,
-        $qty = 1
-    ) {
-        $line_item = null;
-        if ($total_line_item instanceof EE_Line_Item && $total_line_item->is_total()) {
-            $ticket_line_items = EEH_Line_Item::get_ticket_line_items($total_line_item);
-            foreach ((array) $ticket_line_items as $ticket_line_item) {
-                if ($ticket_line_item instanceof EE_Line_Item
-                    && (int) $ticket_line_item->OBJ_ID() === (int) $ticket->ID()
-                ) {
-                    $line_item = $ticket_line_item;
-                    break;
-                }
-            }
-        }
-        if ($line_item instanceof EE_Line_Item) {
-            EEH_Line_Item::increment_quantity($line_item, $qty);
-            return $line_item;
-        }
-        return null;
-    }
-
-
-    /**
-     * Increments the line item and all its children's quantity by $qty (but percent line items are unaffected).
-     * Does NOT save or recalculate other line items totals
-     *
-     * @param EE_Line_Item $line_item
-     * @param int          $qty
-     * @return void
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function increment_quantity(EE_Line_Item $line_item, $qty = 1)
-    {
-        if (! $line_item->is_percent()) {
-            $qty += $line_item->quantity();
-            $line_item->set_quantity($qty);
-            $line_item->set_total($line_item->unit_price() * $qty);
-            $line_item->save();
-        }
-        foreach ($line_item->children() as $child) {
-            if ($child->is_sub_line_item()) {
-                EEH_Line_Item::update_quantity($child, $qty);
-            }
-        }
-    }
-
-
-    /**
-     * Decrements the line item and all its children's quantity by $qty (but percent line items are unaffected).
-     * Does NOT save or recalculate other line items totals
-     *
-     * @param EE_Line_Item $line_item
-     * @param int          $qty
-     * @return void
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function decrement_quantity(EE_Line_Item $line_item, $qty = 1)
-    {
-        if (! $line_item->is_percent()) {
-            $qty = $line_item->quantity() - $qty;
-            $qty = max($qty, 0);
-            $line_item->set_quantity($qty);
-            $line_item->set_total($line_item->unit_price() * $qty);
-            $line_item->save();
-        }
-        foreach ($line_item->children() as $child) {
-            if ($child->is_sub_line_item()) {
-                EEH_Line_Item::update_quantity($child, $qty);
-            }
-        }
-    }
-
-
-    /**
-     * Updates the line item and its children's quantities to the specified number.
-     * Does NOT save them or recalculate totals.
-     *
-     * @param EE_Line_Item $line_item
-     * @param int          $new_quantity
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function update_quantity(EE_Line_Item $line_item, $new_quantity)
-    {
-        if (! $line_item->is_percent()) {
-            $line_item->set_quantity($new_quantity);
-            $line_item->set_total($line_item->unit_price() * $new_quantity);
-            $line_item->save();
-        }
-        foreach ($line_item->children() as $child) {
-            if ($child->is_sub_line_item()) {
-                EEH_Line_Item::update_quantity($child, $new_quantity);
-            }
-        }
-    }
-
-
-    /**
-     * Returns the new line item created by adding a purchase of the ticket
-     *
-     * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
-     * @param EE_Ticket    $ticket
-     * @param int          $qty
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_ticket_line_item(EE_Line_Item $total_line_item, EE_Ticket $ticket, $qty = 1)
-    {
-        $datetimes = $ticket->datetimes();
-        $first_datetime = reset($datetimes);
-        $first_datetime_name = esc_html__('Event', 'event_espresso');
-        if ($first_datetime instanceof EE_Datetime && $first_datetime->event() instanceof EE_Event) {
-            $first_datetime_name = $first_datetime->event()->name();
-        }
-        $event = sprintf(_x('(For %1$s)', '(For Event Name)', 'event_espresso'), $first_datetime_name);
-        // get event subtotal line
-        $events_sub_total = self::get_event_line_item_for_ticket($total_line_item, $ticket);
-        // add $ticket to cart
-        $line_item = EE_Line_Item::new_instance(array(
-            'LIN_name'       => $ticket->name(),
-            'LIN_desc'       => $ticket->description() !== '' ? $ticket->description() . ' ' . $event : $event,
-            'LIN_unit_price' => $ticket->price(),
-            'LIN_quantity'   => $qty,
-            'LIN_is_taxable' => $ticket->taxable(),
-            'LIN_order'      => count($events_sub_total->children()),
-            'LIN_total'      => $ticket->price() * $qty,
-            'LIN_type'       => EEM_Line_Item::type_line_item,
-            'OBJ_ID'         => $ticket->ID(),
-            'OBJ_type'       => EEM_Line_Item::OBJ_TYPE_TICKET,
-        ));
-        $line_item = apply_filters(
-            'FHEE__EEH_Line_Item__create_ticket_line_item__line_item',
-            $line_item
-        );
-        $events_sub_total->add_child_line_item($line_item);
-        // now add the sub-line items
-        $running_total_for_ticket = 0;
-        foreach ($ticket->prices(array('order_by' => array('PRC_order' => 'ASC'))) as $price) {
-            $sign = $price->is_discount() ? -1 : 1;
-            $price_total = $price->is_percent()
-                ? $running_total_for_ticket * $price->amount() / 100
-                : $price->amount() * $qty;
-            $sub_line_item = EE_Line_Item::new_instance(array(
-                'LIN_name'       => $price->name(),
-                'LIN_desc'       => $price->desc(),
-                'LIN_quantity'   => $price->is_percent() ? null : $qty,
-                'LIN_is_taxable' => false,
-                'LIN_order'      => $price->order(),
-                'LIN_total'      => $sign * $price_total,
-                'LIN_type'       => EEM_Line_Item::type_sub_line_item,
-                'OBJ_ID'         => $price->ID(),
-                'OBJ_type'       => EEM_Line_Item::OBJ_TYPE_PRICE,
-            ));
-            $sub_line_item = apply_filters(
-                'FHEE__EEH_Line_Item__create_ticket_line_item__sub_line_item',
-                $sub_line_item
-            );
-            if ($price->is_percent()) {
-                $sub_line_item->set_percent($sign * $price->amount());
-            } else {
-                $sub_line_item->set_unit_price($sign * $price->amount());
-            }
-            $running_total_for_ticket += $price_total;
-            $line_item->add_child_line_item($sub_line_item);
-        }
-        return $line_item;
-    }
-
-
-    /**
-     * Adds the specified item under the pre-tax-sub-total line item. Automatically
-     * re-calculates the line item totals and updates the related transaction. But
-     * DOES NOT automatically upgrade the transaction's registrations' final prices (which
-     * should probably change because of this).
-     * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
-     * after using this, to keep the registration final prices in-sync with the transaction's total.
-     *
-     * @param EE_Line_Item $total_line_item
-     * @param EE_Line_Item $item to be added
-     * @return boolean
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function add_item(EE_Line_Item $total_line_item, EE_Line_Item $item)
-    {
-        $pre_tax_subtotal = self::get_pre_tax_subtotal($total_line_item);
-        if ($pre_tax_subtotal instanceof EE_Line_Item) {
-            $success = $pre_tax_subtotal->add_child_line_item($item);
-        } else {
-            return false;
-        }
-        $total_line_item->recalculate_total_including_taxes();
-        return $success;
-    }
-
-
-    /**
-     * cancels an existing ticket line item,
-     * by decrementing it's quantity by 1 and adding a new "type_cancellation" sub-line-item.
-     * ALL totals and subtotals will NEED TO BE UPDATED after performing this action
-     *
-     * @param EE_Line_Item $ticket_line_item
-     * @param int          $qty
-     * @return bool success
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function cancel_ticket_line_item(EE_Line_Item $ticket_line_item, $qty = 1)
-    {
-        // validate incoming line_item
-        if ($ticket_line_item->OBJ_type() !== EEM_Line_Item::OBJ_TYPE_TICKET) {
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'The supplied line item must have an Object Type of "Ticket", not %1$s.',
-                        'event_espresso'
-                    ),
-                    $ticket_line_item->type()
-                )
-            );
-        }
-        if ($ticket_line_item->quantity() < $qty) {
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'Can not cancel %1$d ticket(s) because the supplied line item has a quantity of %2$d.',
-                        'event_espresso'
-                    ),
-                    $qty,
-                    $ticket_line_item->quantity()
-                )
-            );
-        }
-        // decrement ticket quantity; don't rely on auto-fixing when recalculating totals to do this
-        $ticket_line_item->set_quantity($ticket_line_item->quantity() - $qty);
-        foreach ($ticket_line_item->children() as $child_line_item) {
-            if ($child_line_item->is_sub_line_item()
-                && ! $child_line_item->is_percent()
-                && ! $child_line_item->is_cancellation()
-            ) {
-                $child_line_item->set_quantity($child_line_item->quantity() - $qty);
-            }
-        }
-        // get cancellation sub line item
-        $cancellation_line_item = EEH_Line_Item::get_descendants_of_type(
-            $ticket_line_item,
-            EEM_Line_Item::type_cancellation
-        );
-        $cancellation_line_item = reset($cancellation_line_item);
-        // verify that this ticket was indeed previously cancelled
-        if ($cancellation_line_item instanceof EE_Line_Item) {
-            // increment cancelled quantity
-            $cancellation_line_item->set_quantity($cancellation_line_item->quantity() + $qty);
-        } else {
-            // create cancellation sub line item
-            $cancellation_line_item = EE_Line_Item::new_instance(array(
-                'LIN_name'       => esc_html__('Cancellation', 'event_espresso'),
-                'LIN_desc'       => sprintf(
-                    esc_html_x(
-                        'Cancelled %1$s : %2$s',
-                        'Cancelled Ticket Name : 2015-01-01 11:11',
-                        'event_espresso'
-                    ),
-                    $ticket_line_item->name(),
-                    current_time(get_option('date_format') . ' ' . get_option('time_format'))
-                ),
-                'LIN_unit_price' => 0, // $ticket_line_item->unit_price()
-                'LIN_quantity'   => $qty,
-                'LIN_is_taxable' => $ticket_line_item->is_taxable(),
-                'LIN_order'      => count($ticket_line_item->children()),
-                'LIN_total'      => 0, // $ticket_line_item->unit_price()
-                'LIN_type'       => EEM_Line_Item::type_cancellation,
-            ));
-            $ticket_line_item->add_child_line_item($cancellation_line_item);
-        }
-        if ($ticket_line_item->save_this_and_descendants() > 0) {
-            // decrement parent line item quantity
-            $event_line_item = $ticket_line_item->parent();
-            if ($event_line_item instanceof EE_Line_Item
-                && $event_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_EVENT
-            ) {
-                $event_line_item->set_quantity($event_line_item->quantity() - $qty);
-                $event_line_item->save();
-            }
-            EEH_Line_Item::get_grand_total_and_recalculate_everything($ticket_line_item);
-            return true;
-        }
-        return false;
-    }
-
-
-    /**
-     * reinstates (un-cancels?) a previously canceled ticket line item,
-     * by incrementing it's quantity by 1, and decrementing it's "type_cancellation" sub-line-item.
-     * ALL totals and subtotals will NEED TO BE UPDATED after performing this action
-     *
-     * @param EE_Line_Item $ticket_line_item
-     * @param int          $qty
-     * @return bool success
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function reinstate_canceled_ticket_line_item(EE_Line_Item $ticket_line_item, $qty = 1)
-    {
-        // validate incoming line_item
-        if ($ticket_line_item->OBJ_type() !== EEM_Line_Item::OBJ_TYPE_TICKET) {
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'The supplied line item must have an Object Type of "Ticket", not %1$s.',
-                        'event_espresso'
-                    ),
-                    $ticket_line_item->type()
-                )
-            );
-        }
-        // get cancellation sub line item
-        $cancellation_line_item = EEH_Line_Item::get_descendants_of_type(
-            $ticket_line_item,
-            EEM_Line_Item::type_cancellation
-        );
-        $cancellation_line_item = reset($cancellation_line_item);
-        // verify that this ticket was indeed previously cancelled
-        if (! $cancellation_line_item instanceof EE_Line_Item) {
-            return false;
-        }
-        if ($cancellation_line_item->quantity() > $qty) {
-            // decrement cancelled quantity
-            $cancellation_line_item->set_quantity($cancellation_line_item->quantity() - $qty);
-        } elseif ($cancellation_line_item->quantity() === $qty) {
-            // decrement cancelled quantity in case anyone still has the object kicking around
-            $cancellation_line_item->set_quantity($cancellation_line_item->quantity() - $qty);
-            // delete because quantity will end up as 0
-            $cancellation_line_item->delete();
-            // and attempt to destroy the object,
-            // even though PHP won't actually destroy it until it needs the memory
-            unset($cancellation_line_item);
-        } else {
-            // what ?!?! negative quantity ?!?!
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'Can not reinstate %1$d cancelled ticket(s) because the cancelled ticket quantity is only %2$d.',
-                        'event_espresso'
-                    ),
-                    $qty,
-                    $cancellation_line_item->quantity()
-                )
-            );
-        }
-        // increment ticket quantity
-        $ticket_line_item->set_quantity($ticket_line_item->quantity() + $qty);
-        if ($ticket_line_item->save_this_and_descendants() > 0) {
-            // increment parent line item quantity
-            $event_line_item = $ticket_line_item->parent();
-            if ($event_line_item instanceof EE_Line_Item
-                && $event_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_EVENT
-            ) {
-                $event_line_item->set_quantity($event_line_item->quantity() + $qty);
-            }
-            EEH_Line_Item::get_grand_total_and_recalculate_everything($ticket_line_item);
-            return true;
-        }
-        return false;
-    }
-
-
-    /**
-     * calls EEH_Line_Item::find_transaction_grand_total_for_line_item()
-     * then EE_Line_Item::recalculate_total_including_taxes() on the result
-     *
-     * @param EE_Line_Item $line_item
-     * @return float
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_grand_total_and_recalculate_everything(EE_Line_Item $line_item)
-    {
-        $grand_total_line_item = EEH_Line_Item::find_transaction_grand_total_for_line_item($line_item);
-        return $grand_total_line_item->recalculate_total_including_taxes();
-    }
-
-
-    /**
-     * Gets the line item which contains the subtotal of all the items
-     *
-     * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_pre_tax_subtotal(EE_Line_Item $total_line_item)
-    {
-        $pre_tax_subtotal = $total_line_item->get_child_line_item('pre-tax-subtotal');
-        return $pre_tax_subtotal instanceof EE_Line_Item
-            ? $pre_tax_subtotal
-            : self::create_pre_tax_subtotal($total_line_item);
-    }
-
-
-    /**
-     * Gets the line item for the taxes subtotal
-     *
-     * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_taxes_subtotal(EE_Line_Item $total_line_item)
-    {
-        $taxes = $total_line_item->get_child_line_item('taxes');
-        return $taxes ? $taxes : self::create_taxes_subtotal($total_line_item);
-    }
-
-
-    /**
-     * sets the TXN ID on an EE_Line_Item if passed a valid EE_Transaction object
-     *
-     * @param EE_Line_Item   $line_item
-     * @param EE_Transaction $transaction
-     * @return void
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function set_TXN_ID(EE_Line_Item $line_item, $transaction = null)
-    {
-        if ($transaction) {
-            /** @type EEM_Transaction $EEM_Transaction */
-            $EEM_Transaction = EE_Registry::instance()->load_model('Transaction');
-            $TXN_ID = $EEM_Transaction->ensure_is_ID($transaction);
-            $line_item->set_TXN_ID($TXN_ID);
-        }
-    }
-
-
-    /**
-     * Creates a new default total line item for the transaction,
-     * and its tickets subtotal and taxes subtotal line items (and adds the
-     * existing taxes as children of the taxes subtotal line item)
-     *
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item of type total
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_total_line_item($transaction = null)
-    {
-        $total_line_item = EE_Line_Item::new_instance(array(
-            'LIN_code' => 'total',
-            'LIN_name' => esc_html__('Grand Total', 'event_espresso'),
-            'LIN_type' => EEM_Line_Item::type_total,
-            'OBJ_type' => EEM_Line_Item::OBJ_TYPE_TRANSACTION,
-        ));
-        $total_line_item = apply_filters(
-            'FHEE__EEH_Line_Item__create_total_line_item__total_line_item',
-            $total_line_item
-        );
-        self::set_TXN_ID($total_line_item, $transaction);
-        self::create_pre_tax_subtotal($total_line_item, $transaction);
-        self::create_taxes_subtotal($total_line_item, $transaction);
-        return $total_line_item;
-    }
-
-
-    /**
-     * Creates a default items subtotal line item
-     *
-     * @param EE_Line_Item   $total_line_item
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    protected static function create_pre_tax_subtotal(EE_Line_Item $total_line_item, $transaction = null)
-    {
-        $pre_tax_line_item = EE_Line_Item::new_instance(array(
-            'LIN_code' => 'pre-tax-subtotal',
-            'LIN_name' => esc_html__('Pre-Tax Subtotal', 'event_espresso'),
-            'LIN_type' => EEM_Line_Item::type_sub_total,
-        ));
-        $pre_tax_line_item = apply_filters(
-            'FHEE__EEH_Line_Item__create_pre_tax_subtotal__pre_tax_line_item',
-            $pre_tax_line_item
-        );
-        self::set_TXN_ID($pre_tax_line_item, $transaction);
-        $total_line_item->add_child_line_item($pre_tax_line_item);
-        self::create_event_subtotal($pre_tax_line_item, $transaction);
-        return $pre_tax_line_item;
-    }
-
-
-    /**
-     * Creates a line item for the taxes subtotal and finds all the tax prices
-     * and applies taxes to it
-     *
-     * @param EE_Line_Item   $total_line_item of type EEM_Line_Item::type_total
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    protected static function create_taxes_subtotal(EE_Line_Item $total_line_item, $transaction = null)
-    {
-        $tax_line_item = EE_Line_Item::new_instance(array(
-            'LIN_code'  => 'taxes',
-            'LIN_name'  => esc_html__('Taxes', 'event_espresso'),
-            'LIN_type'  => EEM_Line_Item::type_tax_sub_total,
-            'LIN_order' => 1000,// this should always come last
-        ));
-        $tax_line_item = apply_filters(
-            'FHEE__EEH_Line_Item__create_taxes_subtotal__tax_line_item',
-            $tax_line_item
-        );
-        self::set_TXN_ID($tax_line_item, $transaction);
-        $total_line_item->add_child_line_item($tax_line_item);
-        // and lastly, add the actual taxes
-        self::apply_taxes($total_line_item);
-        return $tax_line_item;
-    }
-
-
-    /**
-     * Creates a default items subtotal line item
-     *
-     * @param EE_Line_Item   $pre_tax_line_item
-     * @param EE_Transaction $transaction
-     * @param EE_Event       $event
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_event_subtotal(EE_Line_Item $pre_tax_line_item, $transaction = null, $event = null)
-    {
-        $event_line_item = EE_Line_Item::new_instance(array(
-            'LIN_code' => self::get_event_code($event),
-            'LIN_name' => self::get_event_name($event),
-            'LIN_desc' => self::get_event_desc($event),
-            'LIN_type' => EEM_Line_Item::type_sub_total,
-            'OBJ_type' => EEM_Line_Item::OBJ_TYPE_EVENT,
-            'OBJ_ID'   => $event instanceof EE_Event ? $event->ID() : 0,
-        ));
-        $event_line_item = apply_filters(
-            'FHEE__EEH_Line_Item__create_event_subtotal__event_line_item',
-            $event_line_item
-        );
-        self::set_TXN_ID($event_line_item, $transaction);
-        $pre_tax_line_item->add_child_line_item($event_line_item);
-        return $event_line_item;
-    }
-
-
-    /**
-     * Gets what the event ticket's code SHOULD be
-     *
-     * @param EE_Event $event
-     * @return string
-     * @throws EE_Error
-     */
-    public static function get_event_code($event)
-    {
-        return 'event-' . ($event instanceof EE_Event ? $event->ID() : '0');
-    }
-
-
-    /**
-     * Gets the event name
-     *
-     * @param EE_Event $event
-     * @return string
-     * @throws EE_Error
-     */
-    public static function get_event_name($event)
-    {
-        return $event instanceof EE_Event
-            ? mb_substr($event->name(), 0, 245)
-            : esc_html__('Event', 'event_espresso');
-    }
-
-
-    /**
-     * Gets the event excerpt
-     *
-     * @param EE_Event $event
-     * @return string
-     * @throws EE_Error
-     */
-    public static function get_event_desc($event)
-    {
-        return $event instanceof EE_Event ? $event->short_description() : '';
-    }
-
-
-    /**
-     * Given the grand total line item and a ticket, finds the event sub-total
-     * line item the ticket's purchase should be added onto
-     *
-     * @access public
-     * @param EE_Line_Item $grand_total the grand total line item
-     * @param EE_Ticket    $ticket
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_event_line_item_for_ticket(EE_Line_Item $grand_total, EE_Ticket $ticket)
-    {
-        $first_datetime = $ticket->first_datetime();
-        if (! $first_datetime instanceof EE_Datetime) {
-            throw new EE_Error(
-                sprintf(
-                    __('The supplied ticket (ID %d) has no datetimes', 'event_espresso'),
-                    $ticket->ID()
-                )
-            );
-        }
-        $event = $first_datetime->event();
-        if (! $event instanceof EE_Event) {
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'The supplied ticket (ID %d) has no event data associated with it.',
-                        'event_espresso'
-                    ),
-                    $ticket->ID()
-                )
-            );
-        }
-        $events_sub_total = EEH_Line_Item::get_event_line_item($grand_total, $event);
-        if (! $events_sub_total instanceof EE_Line_Item) {
-            throw new EE_Error(
-                sprintf(
-                    esc_html__(
-                        'There is no events sub-total for ticket %s on total line item %d',
-                        'event_espresso'
-                    ),
-                    $ticket->ID(),
-                    $grand_total->ID()
-                )
-            );
-        }
-        return $events_sub_total;
-    }
-
-
-    /**
-     * Gets the event line item
-     *
-     * @param EE_Line_Item $grand_total
-     * @param EE_Event     $event
-     * @return EE_Line_Item for the event subtotal which is a child of $grand_total
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_event_line_item(EE_Line_Item $grand_total, $event)
-    {
-        /** @type EE_Event $event */
-        $event = EEM_Event::instance()->ensure_is_obj($event, true);
-        $event_line_item = null;
-        $found = false;
-        foreach (EEH_Line_Item::get_event_subtotals($grand_total) as $event_line_item) {
-            // default event subtotal, we should only ever find this the first time this method is called
-            if (! $event_line_item->OBJ_ID()) {
-                // let's use this! but first... set the event details
-                EEH_Line_Item::set_event_subtotal_details($event_line_item, $event);
-                $found = true;
-                break;
-            }
-            if ($event_line_item->OBJ_ID() === $event->ID()) {
-                // found existing line item for this event in the cart, so break out of loop and use this one
-                $found = true;
-                break;
-            }
-        }
-        if (! $found) {
-            // there is no event sub-total yet, so add it
-            $pre_tax_subtotal = EEH_Line_Item::get_pre_tax_subtotal($grand_total);
-            // create a new "event" subtotal below that
-            $event_line_item = EEH_Line_Item::create_event_subtotal($pre_tax_subtotal, null, $event);
-            // and set the event details
-            EEH_Line_Item::set_event_subtotal_details($event_line_item, $event);
-        }
-        return $event_line_item;
-    }
-
-
-    /**
-     * Creates a default items subtotal line item
-     *
-     * @param EE_Line_Item   $event_line_item
-     * @param EE_Event       $event
-     * @param EE_Transaction $transaction
-     * @return void
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function set_event_subtotal_details(
-        EE_Line_Item $event_line_item,
-        EE_Event $event,
-        $transaction = null
-    ) {
-        if ($event instanceof EE_Event) {
-            $event_line_item->set_code(self::get_event_code($event));
-            $event_line_item->set_name(self::get_event_name($event));
-            $event_line_item->set_desc(self::get_event_desc($event));
-            $event_line_item->set_OBJ_ID($event->ID());
-        }
-        self::set_TXN_ID($event_line_item, $transaction);
-    }
-
-
-    /**
-     * Finds what taxes should apply, adds them as tax line items under the taxes sub-total,
-     * and recalculates the taxes sub-total and the grand total. Resets the taxes, so
-     * any old taxes are removed
-     *
-     * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
-     * @param bool         $update_txn_status
-     * @return bool
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     * @throws RuntimeException
-     */
-    public static function apply_taxes(EE_Line_Item $total_line_item, $update_txn_status = false)
-    {
-        /** @type EEM_Price $EEM_Price */
-        $EEM_Price = EE_Registry::instance()->load_model('Price');
-        // get array of taxes via Price Model
-        $ordered_taxes = $EEM_Price->get_all_prices_that_are_taxes();
-        ksort($ordered_taxes);
-        $taxes_line_item = self::get_taxes_subtotal($total_line_item);
-        // just to be safe, remove its old tax line items
-        $deleted = $taxes_line_item->delete_children_line_items();
-        $updates = false;
-        // loop thru taxes
-        foreach ($ordered_taxes as $order => $taxes) {
-            foreach ($taxes as $tax) {
-                if ($tax instanceof EE_Price) {
-                    $tax_line_item = EE_Line_Item::new_instance(
-                        array(
-                            'LIN_name'       => $tax->name(),
-                            'LIN_desc'       => $tax->desc(),
-                            'LIN_percent'    => $tax->amount(),
-                            'LIN_is_taxable' => false,
-                            'LIN_order'      => $order,
-                            'LIN_total'      => 0,
-                            'LIN_type'       => EEM_Line_Item::type_tax,
-                            'OBJ_type'       => EEM_Line_Item::OBJ_TYPE_PRICE,
-                            'OBJ_ID'         => $tax->ID(),
-                        )
-                    );
-                    $tax_line_item = apply_filters(
-                        'FHEE__EEH_Line_Item__apply_taxes__tax_line_item',
-                        $tax_line_item
-                    );
-                    $updates = $taxes_line_item->add_child_line_item($tax_line_item) ?
-                        true :
-                        $updates;
-                }
-            }
-        }
-        // only recalculate totals if something changed
-        if ($deleted || $updates) {
-            $total_line_item->recalculate_total_including_taxes($update_txn_status);
-            return true;
-        }
-        return false;
-    }
-
-
-    /**
-     * Ensures that taxes have been applied to the order, if not applies them.
-     * Returns the total amount of tax
-     *
-     * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
-     * @return float
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function ensure_taxes_applied($total_line_item)
-    {
-        $taxes_subtotal = self::get_taxes_subtotal($total_line_item);
-        if (! $taxes_subtotal->children()) {
-            self::apply_taxes($total_line_item);
-        }
-        return $taxes_subtotal->total();
-    }
-
-
-    /**
-     * Deletes ALL children of the passed line item
-     *
-     * @param EE_Line_Item $parent_line_item
-     * @return bool
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function delete_all_child_items(EE_Line_Item $parent_line_item)
-    {
-        $deleted = 0;
-        foreach ($parent_line_item->children() as $child_line_item) {
-            if ($child_line_item instanceof EE_Line_Item) {
-                $deleted += EEH_Line_Item::delete_all_child_items($child_line_item);
-                if ($child_line_item->ID()) {
-                    $child_line_item->delete();
-                    unset($child_line_item);
-                } else {
-                    $parent_line_item->delete_child_line_item($child_line_item->code());
-                }
-                $deleted++;
-            }
-        }
-        return $deleted;
-    }
-
-
-    /**
-     * Deletes the line items as indicated by the line item code(s) provided,
-     * regardless of where they're found in the line item tree. Automatically
-     * re-calculates the line item totals and updates the related transaction. But
-     * DOES NOT automatically upgrade the transaction's registrations' final prices (which
-     * should probably change because of this).
-     * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
-     * after using this, to keep the registration final prices in-sync with the transaction's total.
-     *
-     * @param EE_Line_Item      $total_line_item of type EEM_Line_Item::type_total
-     * @param array|bool|string $line_item_codes
-     * @return int number of items successfully removed
-     * @throws EE_Error
-     */
-    public static function delete_items(EE_Line_Item $total_line_item, $line_item_codes = false)
-    {
-
-        if ($total_line_item->type() !== EEM_Line_Item::type_total) {
-            EE_Error::doing_it_wrong(
-                'EEH_Line_Item::delete_items',
-                esc_html__(
-                    'This static method should only be called with a TOTAL line item, otherwise we won\'t recalculate the totals correctly',
-                    'event_espresso'
-                ),
-                '4.6.18'
-            );
-        }
-        do_action('AHEE_log', __FILE__, __FUNCTION__, '');
-
-        // check if only a single line_item_id was passed
-        if (! empty($line_item_codes) && ! is_array($line_item_codes)) {
-            // place single line_item_id in an array to appear as multiple line_item_ids
-            $line_item_codes = array($line_item_codes);
-        }
-        $removals = 0;
-        // cycle thru line_item_ids
-        foreach ($line_item_codes as $line_item_id) {
-            $removals += $total_line_item->delete_child_line_item($line_item_id);
-        }
-
-        if ($removals > 0) {
-            $total_line_item->recalculate_taxes_and_tax_total();
-            return $removals;
-        } else {
-            return false;
-        }
-    }
-
-
-    /**
-     * Overwrites the previous tax by clearing out the old taxes, and creates a new
-     * tax and updates the total line item accordingly
-     *
-     * @param EE_Line_Item $total_line_item
-     * @param float        $amount
-     * @param string       $name
-     * @param string       $description
-     * @param string       $code
-     * @param boolean      $add_to_existing_line_item
-     *                          if true, and a duplicate line item with the same code is found,
-     *                          $amount will be added onto it; otherwise will simply set the taxes to match $amount
-     * @return EE_Line_Item the new tax line item created
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function set_total_tax_to(
-        EE_Line_Item $total_line_item,
-        $amount,
-        $name = null,
-        $description = null,
-        $code = null,
-        $add_to_existing_line_item = false
-    ) {
-        $tax_subtotal = self::get_taxes_subtotal($total_line_item);
-        $taxable_total = $total_line_item->taxable_total();
-
-        if ($add_to_existing_line_item) {
-            $new_tax = $tax_subtotal->get_child_line_item($code);
-            EEM_Line_Item::instance()->delete(
-                array(array('LIN_code' => array('!=', $code), 'LIN_parent' => $tax_subtotal->ID()))
-            );
-        } else {
-            $new_tax = null;
-            $tax_subtotal->delete_children_line_items();
-        }
-        if ($new_tax) {
-            $new_tax->set_total($new_tax->total() + $amount);
-            $new_tax->set_percent($taxable_total ? $new_tax->total() / $taxable_total * 100 : 0);
-        } else {
-            // no existing tax item. Create it
-            $new_tax = EE_Line_Item::new_instance(array(
-                'TXN_ID'      => $total_line_item->TXN_ID(),
-                'LIN_name'    => $name ? $name : esc_html__('Tax', 'event_espresso'),
-                'LIN_desc'    => $description ? $description : '',
-                'LIN_percent' => $taxable_total ? ($amount / $taxable_total * 100) : 0,
-                'LIN_total'   => $amount,
-                'LIN_parent'  => $tax_subtotal->ID(),
-                'LIN_type'    => EEM_Line_Item::type_tax,
-                'LIN_code'    => $code,
-            ));
-        }
-
-        $new_tax = apply_filters(
-            'FHEE__EEH_Line_Item__set_total_tax_to__new_tax_subtotal',
-            $new_tax,
-            $total_line_item
-        );
-        $new_tax->save();
-        $tax_subtotal->set_total($new_tax->total());
-        $tax_subtotal->save();
-        $total_line_item->recalculate_total_including_taxes();
-        return $new_tax;
-    }
-
-
-    /**
-     * Makes all the line items which are children of $line_item taxable (or not).
-     * Does NOT save the line items
-     *
-     * @param EE_Line_Item $line_item
-     * @param boolean      $taxable
-     * @param string       $code_substring_for_whitelist if this string is part of the line item's code
-     *                                                   it will be whitelisted (ie, except from becoming taxable)
-     * @throws EE_Error
-     */
-    public static function set_line_items_taxable(
-        EE_Line_Item $line_item,
-        $taxable = true,
-        $code_substring_for_whitelist = null
-    ) {
-        $whitelisted = false;
-        if ($code_substring_for_whitelist !== null) {
-            $whitelisted = strpos($line_item->code(), $code_substring_for_whitelist) !== false;
-        }
-        if (! $whitelisted && $line_item->is_line_item()) {
-            $line_item->set_is_taxable($taxable);
-        }
-        foreach ($line_item->children() as $child_line_item) {
-            EEH_Line_Item::set_line_items_taxable(
-                $child_line_item,
-                $taxable,
-                $code_substring_for_whitelist
-            );
-        }
-    }
-
-
-    /**
-     * Gets all descendants that are event subtotals
-     *
-     * @uses  EEH_Line_Item::get_subtotals_of_object_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_event_subtotals(EE_Line_Item $parent_line_item)
-    {
-        return self::get_subtotals_of_object_type($parent_line_item, EEM_Line_Item::OBJ_TYPE_EVENT);
-    }
-
-
-    /**
-     * Gets all descendants subtotals that match the supplied object type
-     *
-     * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $obj_type
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_subtotals_of_object_type(EE_Line_Item $parent_line_item, $obj_type = '')
-    {
-        return self::_get_descendants_by_type_and_object_type(
-            $parent_line_item,
-            EEM_Line_Item::type_sub_total,
-            $obj_type
-        );
-    }
-
-
-    /**
-     * Gets all descendants that are tickets
-     *
-     * @uses  EEH_Line_Item::get_line_items_of_object_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_ticket_line_items(EE_Line_Item $parent_line_item)
-    {
-        return self::get_line_items_of_object_type(
-            $parent_line_item,
-            EEM_Line_Item::OBJ_TYPE_TICKET
-        );
-    }
-
-
-    /**
-     * Gets all descendants subtotals that match the supplied object type
-     *
-     * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $obj_type
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_line_items_of_object_type(EE_Line_Item $parent_line_item, $obj_type = '')
-    {
-        return self::_get_descendants_by_type_and_object_type(
-            $parent_line_item,
-            EEM_Line_Item::type_line_item,
-            $obj_type
-        );
-    }
-
-
-    /**
-     * Gets all the descendants (ie, children or children of children etc) that are of the type 'tax'
-     *
-     * @uses  EEH_Line_Item::get_descendants_of_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_tax_descendants(EE_Line_Item $parent_line_item)
-    {
-        return EEH_Line_Item::get_descendants_of_type(
-            $parent_line_item,
-            EEM_Line_Item::type_tax
-        );
-    }
-
-
-    /**
-     * Gets all the real items purchased which are children of this item
-     *
-     * @uses  EEH_Line_Item::get_descendants_of_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_line_item_descendants(EE_Line_Item $parent_line_item)
-    {
-        return EEH_Line_Item::get_descendants_of_type(
-            $parent_line_item,
-            EEM_Line_Item::type_line_item
-        );
-    }
-
-
-    /**
-     * Gets all descendants of supplied line item that match the supplied line item type
-     *
-     * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $line_item_type   one of the EEM_Line_Item constants
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_descendants_of_type(EE_Line_Item $parent_line_item, $line_item_type)
-    {
-        return self::_get_descendants_by_type_and_object_type(
-            $parent_line_item,
-            $line_item_type,
-            null
-        );
-    }
-
-
-    /**
-     * Gets all descendants of supplied line item that match the supplied line item type and possibly the object type
-     * as well
-     *
-     * @param EE_Line_Item  $parent_line_item - the line item to find descendants of
-     * @param string        $line_item_type   one of the EEM_Line_Item constants
-     * @param string | NULL $obj_type         object model class name (minus prefix) or NULL to ignore object type when
-     *                                        searching
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    protected static function _get_descendants_by_type_and_object_type(
-        EE_Line_Item $parent_line_item,
-        $line_item_type,
-        $obj_type = null
-    ) {
-        $objects = array();
-        foreach ($parent_line_item->children() as $child_line_item) {
-            if ($child_line_item instanceof EE_Line_Item) {
-                if ($child_line_item->type() === $line_item_type
-                    && (
-                        $child_line_item->OBJ_type() === $obj_type || $obj_type === null
-                    )
-                ) {
-                    $objects[] = $child_line_item;
-                } else {
-                    // go-through-all-its children looking for more matches
-                    $objects = array_merge(
-                        $objects,
-                        self::_get_descendants_by_type_and_object_type(
-                            $child_line_item,
-                            $line_item_type,
-                            $obj_type
-                        )
-                    );
-                }
-            }
-        }
-        return $objects;
-    }
-
-
-    /**
-     * Gets all descendants subtotals that match the supplied object type
-     *
-     * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $OBJ_type         object type (like Event)
-     * @param array        $OBJ_IDs          array of OBJ_IDs
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    public static function get_line_items_by_object_type_and_IDs(
-        EE_Line_Item $parent_line_item,
-        $OBJ_type = '',
-        $OBJ_IDs = array()
-    ) {
-        return self::_get_descendants_by_object_type_and_object_ID(
-            $parent_line_item,
-            $OBJ_type,
-            $OBJ_IDs
-        );
-    }
-
-
-    /**
-     * Gets all descendants of supplied line item that match the supplied line item type and possibly the object type
-     * as well
-     *
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $OBJ_type         object type (like Event)
-     * @param array        $OBJ_IDs          array of OBJ_IDs
-     * @return EE_Line_Item[]
-     * @throws EE_Error
-     */
-    protected static function _get_descendants_by_object_type_and_object_ID(
-        EE_Line_Item $parent_line_item,
-        $OBJ_type,
-        $OBJ_IDs
-    ) {
-        $objects = array();
-        foreach ($parent_line_item->children() as $child_line_item) {
-            if ($child_line_item instanceof EE_Line_Item) {
-                if ($child_line_item->OBJ_type() === $OBJ_type
-                    && is_array($OBJ_IDs)
-                    && in_array($child_line_item->OBJ_ID(), $OBJ_IDs)
-                ) {
-                    $objects[] = $child_line_item;
-                } else {
-                    // go-through-all-its children looking for more matches
-                    $objects = array_merge(
-                        $objects,
-                        self::_get_descendants_by_object_type_and_object_ID(
-                            $child_line_item,
-                            $OBJ_type,
-                            $OBJ_IDs
-                        )
-                    );
-                }
-            }
-        }
-        return $objects;
-    }
-
-
-    /**
-     * Uses a breadth-first-search in order to find the nearest descendant of
-     * the specified type and returns it, else NULL
-     *
-     * @uses  EEH_Line_Item::_get_nearest_descendant()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $type             like one of the EEM_Line_Item::type_*
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_nearest_descendant_of_type(EE_Line_Item $parent_line_item, $type)
-    {
-        return self::_get_nearest_descendant($parent_line_item, 'LIN_type', $type);
-    }
-
-
-    /**
-     * Uses a breadth-first-search in order to find the nearest descendant
-     * having the specified LIN_code and returns it, else NULL
-     *
-     * @uses  EEH_Line_Item::_get_nearest_descendant()
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $code             any value used for LIN_code
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_nearest_descendant_having_code(EE_Line_Item $parent_line_item, $code)
-    {
-        return self::_get_nearest_descendant($parent_line_item, 'LIN_code', $code);
-    }
-
-
-    /**
-     * Uses a breadth-first-search in order to find the nearest descendant
-     * having the specified LIN_code and returns it, else NULL
-     *
-     * @param EE_Line_Item $parent_line_item - the line item to find descendants of
-     * @param string       $search_field     name of EE_Line_Item property
-     * @param string       $value            any value stored in $search_field
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    protected static function _get_nearest_descendant(EE_Line_Item $parent_line_item, $search_field, $value)
-    {
-        foreach ($parent_line_item->children() as $child) {
-            if ($child->get($search_field) == $value) {
-                return $child;
-            }
-        }
-        foreach ($parent_line_item->children() as $child) {
-            $descendant_found = self::_get_nearest_descendant(
-                $child,
-                $search_field,
-                $value
-            );
-            if ($descendant_found) {
-                return $descendant_found;
-            }
-        }
-        return null;
-    }
-
-
-    /**
-     * if passed line item has a TXN ID, uses that to jump directly to the grand total line item for the transaction,
-     * else recursively walks up the line item tree until a parent of type total is found,
-     *
-     * @param EE_Line_Item $line_item
-     * @return EE_Line_Item
-     * @throws EE_Error
-     */
-    public static function find_transaction_grand_total_for_line_item(EE_Line_Item $line_item)
-    {
-        if ($line_item->TXN_ID()) {
-            $total_line_item = $line_item->transaction()->total_line_item(false);
-            if ($total_line_item instanceof EE_Line_Item) {
-                return $total_line_item;
-            }
-        } else {
-            $line_item_parent = $line_item->parent();
-            if ($line_item_parent instanceof EE_Line_Item) {
-                if ($line_item_parent->is_total()) {
-                    return $line_item_parent;
-                }
-                return EEH_Line_Item::find_transaction_grand_total_for_line_item($line_item_parent);
-            }
-        }
-        throw new EE_Error(
-            sprintf(
-                esc_html__(
-                    'A valid grand total for line item %1$d was not found.',
-                    'event_espresso'
-                ),
-                $line_item->ID()
-            )
-        );
-    }
-
-
-    /**
-     * Prints out a representation of the line item tree
-     *
-     * @param EE_Line_Item $line_item
-     * @param int          $indentation
-     * @return void
-     * @throws EE_Error
-     */
-    public static function visualize(EE_Line_Item $line_item, $indentation = 0)
-    {
-        echo defined('EE_TESTS_DIR') ? "\n" : '<br />';
-        if (! $indentation) {
-            echo defined('EE_TESTS_DIR') ? "\n" : '<br />';
-        }
-        for ($i = 0; $i < $indentation; $i++) {
-            echo '. ';
-        }
-        $breakdown = '';
-        if ($line_item->is_line_item()) {
-            if ($line_item->is_percent()) {
-                $breakdown = "{$line_item->percent()}%";
-            } else {
-                $breakdown = '$' . "{$line_item->unit_price()} x {$line_item->quantity()}";
-            }
-        }
-        echo $line_item->name();
-        echo " [ ID:{$line_item->ID()} | qty:{$line_item->quantity()} ] {$line_item->type()} : ";
-        echo '$' . (string) $line_item->total();
-        if ($breakdown) {
-            echo " ( {$breakdown} )";
-        }
-        if ($line_item->is_taxable()) {
-            echo '  * taxable';
-        }
-        if ($line_item->children()) {
-            foreach ($line_item->children() as $child) {
-                self::visualize($child, $indentation + 1);
-            }
-        }
-    }
-
-
-    /**
-     * Calculates the registration's final price, taking into account that they
-     * need to not only help pay for their OWN ticket, but also any transaction-wide surcharges and taxes,
-     * and receive a portion of any transaction-wide discounts.
-     * eg1, if I buy a $1 ticket and brent buys a $9 ticket, and we receive a $5 discount
-     * then I'll get 1/10 of that $5 discount, which is $0.50, and brent will get
-     * 9/10ths of that $5 discount, which is $4.50. So my final price should be $0.50
-     * and brent's final price should be $5.50.
-     * In order to do this, we basically need to traverse the line item tree calculating
-     * the running totals (just as if we were recalculating the total), but when we identify
-     * regular line items, we need to keep track of their share of the grand total.
-     * Also, we need to keep track of the TAXABLE total for each ticket purchase, so
-     * we can know how to apply taxes to it. (Note: "taxable total" does not equal the "pretax total"
-     * when there are non-taxable items; otherwise they would be the same)
-     *
-     * @param EE_Line_Item $line_item
-     * @param array        $billable_ticket_quantities  array of EE_Ticket IDs and their corresponding quantity that
-     *                                                  can be included in price calculations at this moment
-     * @return array        keys are line items for tickets IDs and values are their share of the running total,
-     *                                                  plus the key 'total', and 'taxable' which also has keys of all
-     *                                                  the ticket IDs.
-     *                                                  Eg array(
-     *                                                      12 => 4.3
-     *                                                      23 => 8.0
-     *                                                      'total' => 16.6,
-     *                                                      'taxable' => array(
-     *                                                          12 => 10,
-     *                                                          23 => 4
-     *                                                      ).
-     *                                                  So to find which registrations have which final price, we need
-     *                                                  to find which line item is theirs, which can be done with
-     *                                                  `EEM_Line_Item::instance()->get_line_item_for_registration(
-     *                                                  $registration );`
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function calculate_reg_final_prices_per_line_item(
-        EE_Line_Item $line_item,
-        $billable_ticket_quantities = array()
-    ) {
-        $running_totals = [
-            'total'   => 0,
-            'taxable' => ['total' => 0]
-        ];
-        foreach ($line_item->children() as $child_line_item) {
-            switch ($child_line_item->type()) {
-                case EEM_Line_Item::type_sub_total:
-                    $running_totals_from_subtotal = EEH_Line_Item::calculate_reg_final_prices_per_line_item(
-                        $child_line_item,
-                        $billable_ticket_quantities
-                    );
-                    // combine arrays but preserve numeric keys
-                    $running_totals = array_replace_recursive($running_totals_from_subtotal, $running_totals);
-                    $running_totals['total'] += $running_totals_from_subtotal['total'];
-                    $running_totals['taxable']['total'] += $running_totals_from_subtotal['taxable']['total'];
-                    break;
-
-                case EEM_Line_Item::type_tax_sub_total:
-                    // find how much the taxes percentage is
-                    if ($child_line_item->percent() !== 0) {
-                        $tax_percent_decimal = $child_line_item->percent() / 100;
-                    } else {
-                        $tax_percent_decimal = EE_Taxes::get_total_taxes_percentage() / 100;
-                    }
-                    // and apply to all the taxable totals, and add to the pretax totals
-                    foreach ($running_totals as $line_item_id => $this_running_total) {
-                        // "total" and "taxable" array key is an exception
-                        if ($line_item_id === 'taxable') {
-                            continue;
-                        }
-                        $taxable_total = $running_totals['taxable'][ $line_item_id ];
-                        $running_totals[ $line_item_id ] += ($taxable_total * $tax_percent_decimal);
-                    }
-                    break;
-
-                case EEM_Line_Item::type_line_item:
-                    // ticket line items or ????
-                    if ($child_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET) {
-                        // kk it's a ticket
-                        if (isset($running_totals[ $child_line_item->ID() ])) {
-                            // huh? that shouldn't happen.
-                            $running_totals['total'] += $child_line_item->total();
-                        } else {
-                            // its not in our running totals yet. great.
-                            if ($child_line_item->is_taxable()) {
-                                $taxable_amount = $child_line_item->unit_price();
-                            } else {
-                                $taxable_amount = 0;
-                            }
-                            // are we only calculating totals for some tickets?
-                            if (isset($billable_ticket_quantities[ $child_line_item->OBJ_ID() ])) {
-                                $quantity = $billable_ticket_quantities[ $child_line_item->OBJ_ID() ];
-                                $running_totals[ $child_line_item->ID() ] = $quantity
-                                    ? $child_line_item->unit_price()
-                                    : 0;
-                                $running_totals['taxable'][ $child_line_item->ID() ] = $quantity
-                                    ? $taxable_amount
-                                    : 0;
-                            } else {
-                                $quantity = $child_line_item->quantity();
-                                $running_totals[ $child_line_item->ID() ] = $child_line_item->unit_price();
-                                $running_totals['taxable'][ $child_line_item->ID() ] = $taxable_amount;
-                            }
-                            $running_totals['taxable']['total'] += $taxable_amount * $quantity;
-                            $running_totals['total'] += $child_line_item->unit_price() * $quantity;
-                        }
-                    } else {
-                        // it's some other type of item added to the cart
-                        // it should affect the running totals
-                        // basically we want to convert it into a PERCENT modifier. Because
-                        // more clearly affect all registration's final price equally
-                        $line_items_percent_of_running_total = $running_totals['total'] > 0
-                            ? ($child_line_item->total() / $running_totals['total']) + 1
-                            : 1;
-                        foreach ($running_totals as $line_item_id => $this_running_total) {
-                            // the "taxable" array key is an exception
-                            if ($line_item_id === 'taxable') {
-                                continue;
-                            }
-                            // update the running totals
-                            // yes this actually even works for the running grand total!
-                            $running_totals[ $line_item_id ] =
-                                $line_items_percent_of_running_total * $this_running_total;
-
-                            if ($child_line_item->is_taxable()) {
-                                $running_totals['taxable'][ $line_item_id ] =
-                                    $line_items_percent_of_running_total * $running_totals['taxable'][ $line_item_id ];
-                            }
-                        }
-                    }
-                    break;
-            }
-        }
-        return $running_totals;
-    }
-
-
-    /**
-     * @param EE_Line_Item $total_line_item
-     * @param EE_Line_Item $ticket_line_item
-     * @return float | null
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws OutOfRangeException
-     * @throws ReflectionException
-     */
-    public static function calculate_final_price_for_ticket_line_item(
-        EE_Line_Item $total_line_item,
-        EE_Line_Item $ticket_line_item
-    ) {
-        static $final_prices_per_ticket_line_item = array();
-        if (empty($final_prices_per_ticket_line_item) || empty($final_prices_per_ticket_line_item[$total_line_item->ID()])) {
-            $final_prices_per_ticket_line_item[$total_line_item->ID()] = EEH_Line_Item::calculate_reg_final_prices_per_line_item(
-                $total_line_item
-            );
-        }
-        // ok now find this new registration's final price
-        if (isset($final_prices_per_ticket_line_item[$total_line_item->ID() ][ $ticket_line_item->ID() ])) {
-            return $final_prices_per_ticket_line_item[$total_line_item ][ $ticket_line_item->ID() ];
-        }
-        $message = sprintf(
-            esc_html__(
-                'The final price for the ticket line item (ID:%1$d) could not be calculated.',
-                'event_espresso'
-            ),
-            $ticket_line_item->ID()
-        );
-        if (WP_DEBUG) {
-            $message .= '<br>' . print_r($final_prices_per_ticket_line_item, true);
-            throw new OutOfRangeException($message);
-        }
-        EE_Log::instance()->log(__CLASS__, __FUNCTION__, $message);
-        return null;
-    }
-
-
-    /**
-     * Creates a duplicate of the line item tree, except only includes billable items
-     * and the portion of line items attributed to billable things
-     *
-     * @param EE_Line_Item      $line_item
-     * @param EE_Registration[] $registrations
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function billable_line_item_tree(EE_Line_Item $line_item, $registrations)
-    {
-        $copy_li = EEH_Line_Item::billable_line_item($line_item, $registrations);
-        foreach ($line_item->children() as $child_li) {
-            $copy_li->add_child_line_item(
-                EEH_Line_Item::billable_line_item_tree($child_li, $registrations)
-            );
-        }
-        // if this is the grand total line item, make sure the totals all add up
-        // (we could have duplicated this logic AS we copied the line items, but
-        // it seems DRYer this way)
-        if ($copy_li->type() === EEM_Line_Item::type_total) {
-            $copy_li->recalculate_total_including_taxes();
-        }
-        return $copy_li;
-    }
-
-
-    /**
-     * Creates a new, unsaved line item from $line_item that factors in the
-     * number of billable registrations on $registrations.
-     *
-     * @param EE_Line_Item      $line_item
-     * @param EE_Registration[] $registrations
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function billable_line_item(EE_Line_Item $line_item, $registrations)
-    {
-        $new_li_fields = $line_item->model_field_array();
-        if ($line_item->type() === EEM_Line_Item::type_line_item &&
-            $line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
-        ) {
-            $count = 0;
-            foreach ($registrations as $registration) {
-                if ($line_item->OBJ_ID() === $registration->ticket_ID() &&
-                    in_array(
-                        $registration->status_ID(),
-                        EEM_Registration::reg_statuses_that_allow_payment(),
-                        true
-                    )
-                ) {
-                    $count++;
-                }
-            }
-            $new_li_fields['LIN_quantity'] = $count;
-        }
-        // don't set the total. We'll leave that up to the code that calculates it
-        unset($new_li_fields['LIN_ID'], $new_li_fields['LIN_parent'], $new_li_fields['LIN_total']);
-        return EE_Line_Item::new_instance($new_li_fields);
-    }
-
-
-    /**
-     * Returns a modified line item tree where all the subtotals which have a total of 0
-     * are removed, and line items with a quantity of 0
-     *
-     * @param EE_Line_Item $line_item |null
-     * @return EE_Line_Item|null
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function non_empty_line_items(EE_Line_Item $line_item)
-    {
-        $copied_li = EEH_Line_Item::non_empty_line_item($line_item);
-        if ($copied_li === null) {
-            return null;
-        }
-        // if this is an event subtotal, we want to only include it if it
-        // has a non-zero total and at least one ticket line item child
-        $ticket_children = 0;
-        foreach ($line_item->children() as $child_li) {
-            $child_li_copy = EEH_Line_Item::non_empty_line_items($child_li);
-            if ($child_li_copy !== null) {
-                $copied_li->add_child_line_item($child_li_copy);
-                if ($child_li_copy->type() === EEM_Line_Item::type_line_item &&
-                    $child_li_copy->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
-                ) {
-                    $ticket_children++;
-                }
-            }
-        }
-        // if this is an event subtotal with NO ticket children
-        // we basically want to ignore it
-        if ($ticket_children === 0
-            && $line_item->type() === EEM_Line_Item::type_sub_total
-            && $line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_EVENT
-            && $line_item->total() === 0
-        ) {
-            return null;
-        }
-        return $copied_li;
-    }
-
-
-    /**
-     * Creates a new, unsaved line item, but if it's a ticket line item
-     * with a total of 0, or a subtotal of 0, returns null instead
-     *
-     * @param EE_Line_Item $line_item
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function non_empty_line_item(EE_Line_Item $line_item)
-    {
-        if ($line_item->type() === EEM_Line_Item::type_line_item
-            && $line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
-            && $line_item->quantity() === 0
-        ) {
-            return null;
-        }
-        $new_li_fields = $line_item->model_field_array();
-        // don't set the total. We'll leave that up to the code that calculates it
-        unset($new_li_fields['LIN_ID'], $new_li_fields['LIN_parent']);
-        return EE_Line_Item::new_instance($new_li_fields);
-    }
-
-
-    /**
-     * Cycles through all of the ticket line items for the supplied total line item
-     * and ensures that the line item's "is_taxable" field matches that of its corresponding ticket
-     *
-     * @param EE_Line_Item $total_line_item
-     * @since 4.9.79.p
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function resetIsTaxableForTickets(EE_Line_Item $total_line_item)
-    {
-        $ticket_line_items = self::get_ticket_line_items($total_line_item);
-        foreach ($ticket_line_items as $ticket_line_item) {
-            if ($ticket_line_item instanceof EE_Line_Item
-                && $ticket_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
-            ) {
-                $ticket = $ticket_line_item->ticket();
-                if ($ticket instanceof EE_Ticket && $ticket->taxable() !== $ticket_line_item->is_taxable()) {
-                    $ticket_line_item->set_is_taxable($ticket->taxable());
-                    $ticket_line_item->save();
-                }
-            }
-        }
-    }
-
-
-
-    /**************************************** @DEPRECATED METHODS *************************************** */
-    /**
-     * @deprecated
-     * @param EE_Line_Item $total_line_item
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function get_items_subtotal(EE_Line_Item $total_line_item)
-    {
-        EE_Error::doing_it_wrong(
-            'EEH_Line_Item::get_items_subtotal()',
-            sprintf(
-                esc_html__('Method replaced with %1$s', 'event_espresso'),
-                'EEH_Line_Item::get_pre_tax_subtotal()'
-            ),
-            '4.6.0'
-        );
-        return self::get_pre_tax_subtotal($total_line_item);
-    }
-
-
-    /**
-     * @deprecated
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_default_total_line_item($transaction = null)
-    {
-        EE_Error::doing_it_wrong(
-            'EEH_Line_Item::create_default_total_line_item()',
-            sprintf(
-                esc_html__('Method replaced with %1$s', 'event_espresso'),
-                'EEH_Line_Item::create_total_line_item()'
-            ),
-            '4.6.0'
-        );
-        return self::create_total_line_item($transaction);
-    }
-
-
-    /**
-     * @deprecated
-     * @param EE_Line_Item   $total_line_item
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_default_tickets_subtotal(EE_Line_Item $total_line_item, $transaction = null)
-    {
-        EE_Error::doing_it_wrong(
-            'EEH_Line_Item::create_default_tickets_subtotal()',
-            sprintf(
-                esc_html__('Method replaced with %1$s', 'event_espresso'),
-                'EEH_Line_Item::create_pre_tax_subtotal()'
-            ),
-            '4.6.0'
-        );
-        return self::create_pre_tax_subtotal($total_line_item, $transaction);
-    }
-
-
-    /**
-     * @deprecated
-     * @param EE_Line_Item   $total_line_item
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_default_taxes_subtotal(EE_Line_Item $total_line_item, $transaction = null)
-    {
-        EE_Error::doing_it_wrong(
-            'EEH_Line_Item::create_default_taxes_subtotal()',
-            sprintf(
-                esc_html__('Method replaced with %1$s', 'event_espresso'),
-                'EEH_Line_Item::create_taxes_subtotal()'
-            ),
-            '4.6.0'
-        );
-        return self::create_taxes_subtotal($total_line_item, $transaction);
-    }
-
-
-    /**
-     * @deprecated
-     * @param EE_Line_Item   $total_line_item
-     * @param EE_Transaction $transaction
-     * @return EE_Line_Item
-     * @throws EE_Error
-     * @throws InvalidArgumentException
-     * @throws InvalidDataTypeException
-     * @throws InvalidInterfaceException
-     * @throws ReflectionException
-     */
-    public static function create_default_event_subtotal(EE_Line_Item $total_line_item, $transaction = null)
-    {
-        EE_Error::doing_it_wrong(
-            'EEH_Line_Item::create_default_event_subtotal()',
-            sprintf(
-                esc_html__('Method replaced with %1$s', 'event_espresso'),
-                'EEH_Line_Item::create_event_subtotal()'
-            ),
-            '4.6.0'
-        );
-        return self::create_event_subtotal($total_line_item, $transaction);
-    }
+	/**
+	 * Adds a simple item (unrelated to any other model object) to the provided PARENT line item.
+	 * Does NOT automatically re-calculate the line item totals or update the related transaction.
+	 * You should call recalculate_total_including_taxes() on the grant total line item after this
+	 * to update the subtotals, and EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
+	 * to keep the registration final prices in-sync with the transaction's total.
+	 *
+	 * @param EE_Line_Item $parent_line_item
+	 * @param string       $name
+	 * @param float        $unit_price
+	 * @param string       $description
+	 * @param int          $quantity
+	 * @param boolean      $taxable
+	 * @param boolean      $code if set to a value, ensures there is only one line item with that code
+	 * @return boolean success
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function add_unrelated_item(
+		EE_Line_Item $parent_line_item,
+		$name,
+		$unit_price,
+		$description = '',
+		$quantity = 1,
+		$taxable = false,
+		$code = null
+	) {
+		$items_subtotal = self::get_pre_tax_subtotal($parent_line_item);
+		$line_item = EE_Line_Item::new_instance(array(
+			'LIN_name'       => $name,
+			'LIN_desc'       => $description,
+			'LIN_unit_price' => $unit_price,
+			'LIN_quantity'   => $quantity,
+			'LIN_percent'    => null,
+			'LIN_is_taxable' => $taxable,
+			'LIN_order'      => $items_subtotal instanceof EE_Line_Item ? count($items_subtotal->children()) : 0,
+			'LIN_total'      => (float) $unit_price * (int) $quantity,
+			'LIN_type'       => EEM_Line_Item::type_line_item,
+			'LIN_code'       => $code,
+		));
+		$line_item = apply_filters(
+			'FHEE__EEH_Line_Item__add_unrelated_item__line_item',
+			$line_item,
+			$parent_line_item
+		);
+		return self::add_item($parent_line_item, $line_item);
+	}
+
+
+	/**
+	 * Adds a simple item ( unrelated to any other model object) to the total line item,
+	 * in the correct spot in the line item tree. Automatically
+	 * re-calculates the line item totals and updates the related transaction. But
+	 * DOES NOT automatically upgrade the transaction's registrations' final prices (which
+	 * should probably change because of this).
+	 * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
+	 * after using this, to keep the registration final prices in-sync with the transaction's total.
+	 *
+	 * @param EE_Line_Item $parent_line_item
+	 * @param string       $name
+	 * @param float        $percentage_amount
+	 * @param string       $description
+	 * @param boolean      $taxable
+	 * @return boolean success
+	 * @throws EE_Error
+	 */
+	public static function add_percentage_based_item(
+		EE_Line_Item $parent_line_item,
+		$name,
+		$percentage_amount,
+		$description = '',
+		$taxable = false
+	) {
+		$line_item = EE_Line_Item::new_instance(array(
+			'LIN_name'       => $name,
+			'LIN_desc'       => $description,
+			'LIN_unit_price' => 0,
+			'LIN_percent'    => $percentage_amount,
+			'LIN_quantity'   => 1,
+			'LIN_is_taxable' => $taxable,
+			'LIN_total'      => (float) ($percentage_amount * ($parent_line_item->total() / 100)),
+			'LIN_type'       => EEM_Line_Item::type_line_item,
+			'LIN_parent'     => $parent_line_item->ID(),
+		));
+		$line_item = apply_filters(
+			'FHEE__EEH_Line_Item__add_percentage_based_item__line_item',
+			$line_item
+		);
+		return $parent_line_item->add_child_line_item($line_item, false);
+	}
+
+
+	/**
+	 * Returns the new line item created by adding a purchase of the ticket
+	 * ensures that ticket line item is saved, and that cart total has been recalculated.
+	 * If this ticket has already been purchased, just increments its count.
+	 * Automatically re-calculates the line item totals and updates the related transaction. But
+	 * DOES NOT automatically upgrade the transaction's registrations' final prices (which
+	 * should probably change because of this).
+	 * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
+	 * after using this, to keep the registration final prices in-sync with the transaction's total.
+	 *
+	 * @param EE_Line_Item $total_line_item grand total line item of type EEM_Line_Item::type_total
+	 * @param EE_Ticket    $ticket
+	 * @param int          $qty
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function add_ticket_purchase(EE_Line_Item $total_line_item, EE_Ticket $ticket, $qty = 1)
+	{
+		if (! $total_line_item instanceof EE_Line_Item || ! $total_line_item->is_total()) {
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'A valid line item total is required in order to add tickets. A line item of type "%s" was passed.',
+						'event_espresso'
+					),
+					$ticket->ID(),
+					$total_line_item->ID()
+				)
+			);
+		}
+		// either increment the qty for an existing ticket
+		$line_item = self::increment_ticket_qty_if_already_in_cart($total_line_item, $ticket, $qty);
+		// or add a new one
+		if (! $line_item instanceof EE_Line_Item) {
+			$line_item = self::create_ticket_line_item($total_line_item, $ticket, $qty);
+		}
+		$total_line_item->recalculate_total_including_taxes();
+		return $line_item;
+	}
+
+
+	/**
+	 * Returns the new line item created by adding a purchase of the ticket
+	 *
+	 * @param EE_Line_Item $total_line_item
+	 * @param EE_Ticket    $ticket
+	 * @param int          $qty
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function increment_ticket_qty_if_already_in_cart(
+		EE_Line_Item $total_line_item,
+		EE_Ticket $ticket,
+		$qty = 1
+	) {
+		$line_item = null;
+		if ($total_line_item instanceof EE_Line_Item && $total_line_item->is_total()) {
+			$ticket_line_items = EEH_Line_Item::get_ticket_line_items($total_line_item);
+			foreach ((array) $ticket_line_items as $ticket_line_item) {
+				if ($ticket_line_item instanceof EE_Line_Item
+					&& (int) $ticket_line_item->OBJ_ID() === (int) $ticket->ID()
+				) {
+					$line_item = $ticket_line_item;
+					break;
+				}
+			}
+		}
+		if ($line_item instanceof EE_Line_Item) {
+			EEH_Line_Item::increment_quantity($line_item, $qty);
+			return $line_item;
+		}
+		return null;
+	}
+
+
+	/**
+	 * Increments the line item and all its children's quantity by $qty (but percent line items are unaffected).
+	 * Does NOT save or recalculate other line items totals
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @param int          $qty
+	 * @return void
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function increment_quantity(EE_Line_Item $line_item, $qty = 1)
+	{
+		if (! $line_item->is_percent()) {
+			$qty += $line_item->quantity();
+			$line_item->set_quantity($qty);
+			$line_item->set_total($line_item->unit_price() * $qty);
+			$line_item->save();
+		}
+		foreach ($line_item->children() as $child) {
+			if ($child->is_sub_line_item()) {
+				EEH_Line_Item::update_quantity($child, $qty);
+			}
+		}
+	}
+
+
+	/**
+	 * Decrements the line item and all its children's quantity by $qty (but percent line items are unaffected).
+	 * Does NOT save or recalculate other line items totals
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @param int          $qty
+	 * @return void
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function decrement_quantity(EE_Line_Item $line_item, $qty = 1)
+	{
+		if (! $line_item->is_percent()) {
+			$qty = $line_item->quantity() - $qty;
+			$qty = max($qty, 0);
+			$line_item->set_quantity($qty);
+			$line_item->set_total($line_item->unit_price() * $qty);
+			$line_item->save();
+		}
+		foreach ($line_item->children() as $child) {
+			if ($child->is_sub_line_item()) {
+				EEH_Line_Item::update_quantity($child, $qty);
+			}
+		}
+	}
+
+
+	/**
+	 * Updates the line item and its children's quantities to the specified number.
+	 * Does NOT save them or recalculate totals.
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @param int          $new_quantity
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function update_quantity(EE_Line_Item $line_item, $new_quantity)
+	{
+		if (! $line_item->is_percent()) {
+			$line_item->set_quantity($new_quantity);
+			$line_item->set_total($line_item->unit_price() * $new_quantity);
+			$line_item->save();
+		}
+		foreach ($line_item->children() as $child) {
+			if ($child->is_sub_line_item()) {
+				EEH_Line_Item::update_quantity($child, $new_quantity);
+			}
+		}
+	}
+
+
+	/**
+	 * Returns the new line item created by adding a purchase of the ticket
+	 *
+	 * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
+	 * @param EE_Ticket    $ticket
+	 * @param int          $qty
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_ticket_line_item(EE_Line_Item $total_line_item, EE_Ticket $ticket, $qty = 1)
+	{
+		$datetimes = $ticket->datetimes();
+		$first_datetime = reset($datetimes);
+		$first_datetime_name = esc_html__('Event', 'event_espresso');
+		if ($first_datetime instanceof EE_Datetime && $first_datetime->event() instanceof EE_Event) {
+			$first_datetime_name = $first_datetime->event()->name();
+		}
+		$event = sprintf(_x('(For %1$s)', '(For Event Name)', 'event_espresso'), $first_datetime_name);
+		// get event subtotal line
+		$events_sub_total = self::get_event_line_item_for_ticket($total_line_item, $ticket);
+		// add $ticket to cart
+		$line_item = EE_Line_Item::new_instance(array(
+			'LIN_name'       => $ticket->name(),
+			'LIN_desc'       => $ticket->description() !== '' ? $ticket->description() . ' ' . $event : $event,
+			'LIN_unit_price' => $ticket->price(),
+			'LIN_quantity'   => $qty,
+			'LIN_is_taxable' => $ticket->taxable(),
+			'LIN_order'      => count($events_sub_total->children()),
+			'LIN_total'      => $ticket->price() * $qty,
+			'LIN_type'       => EEM_Line_Item::type_line_item,
+			'OBJ_ID'         => $ticket->ID(),
+			'OBJ_type'       => EEM_Line_Item::OBJ_TYPE_TICKET,
+		));
+		$line_item = apply_filters(
+			'FHEE__EEH_Line_Item__create_ticket_line_item__line_item',
+			$line_item
+		);
+		$events_sub_total->add_child_line_item($line_item);
+		// now add the sub-line items
+		$running_total_for_ticket = 0;
+		foreach ($ticket->prices(array('order_by' => array('PRC_order' => 'ASC'))) as $price) {
+			$sign = $price->is_discount() ? -1 : 1;
+			$price_total = $price->is_percent()
+				? $running_total_for_ticket * $price->amount() / 100
+				: $price->amount() * $qty;
+			$sub_line_item = EE_Line_Item::new_instance(array(
+				'LIN_name'       => $price->name(),
+				'LIN_desc'       => $price->desc(),
+				'LIN_quantity'   => $price->is_percent() ? null : $qty,
+				'LIN_is_taxable' => false,
+				'LIN_order'      => $price->order(),
+				'LIN_total'      => $sign * $price_total,
+				'LIN_type'       => EEM_Line_Item::type_sub_line_item,
+				'OBJ_ID'         => $price->ID(),
+				'OBJ_type'       => EEM_Line_Item::OBJ_TYPE_PRICE,
+			));
+			$sub_line_item = apply_filters(
+				'FHEE__EEH_Line_Item__create_ticket_line_item__sub_line_item',
+				$sub_line_item
+			);
+			if ($price->is_percent()) {
+				$sub_line_item->set_percent($sign * $price->amount());
+			} else {
+				$sub_line_item->set_unit_price($sign * $price->amount());
+			}
+			$running_total_for_ticket += $price_total;
+			$line_item->add_child_line_item($sub_line_item);
+		}
+		return $line_item;
+	}
+
+
+	/**
+	 * Adds the specified item under the pre-tax-sub-total line item. Automatically
+	 * re-calculates the line item totals and updates the related transaction. But
+	 * DOES NOT automatically upgrade the transaction's registrations' final prices (which
+	 * should probably change because of this).
+	 * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
+	 * after using this, to keep the registration final prices in-sync with the transaction's total.
+	 *
+	 * @param EE_Line_Item $total_line_item
+	 * @param EE_Line_Item $item to be added
+	 * @return boolean
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function add_item(EE_Line_Item $total_line_item, EE_Line_Item $item)
+	{
+		$pre_tax_subtotal = self::get_pre_tax_subtotal($total_line_item);
+		if ($pre_tax_subtotal instanceof EE_Line_Item) {
+			$success = $pre_tax_subtotal->add_child_line_item($item);
+		} else {
+			return false;
+		}
+		$total_line_item->recalculate_total_including_taxes();
+		return $success;
+	}
+
+
+	/**
+	 * cancels an existing ticket line item,
+	 * by decrementing it's quantity by 1 and adding a new "type_cancellation" sub-line-item.
+	 * ALL totals and subtotals will NEED TO BE UPDATED after performing this action
+	 *
+	 * @param EE_Line_Item $ticket_line_item
+	 * @param int          $qty
+	 * @return bool success
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function cancel_ticket_line_item(EE_Line_Item $ticket_line_item, $qty = 1)
+	{
+		// validate incoming line_item
+		if ($ticket_line_item->OBJ_type() !== EEM_Line_Item::OBJ_TYPE_TICKET) {
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'The supplied line item must have an Object Type of "Ticket", not %1$s.',
+						'event_espresso'
+					),
+					$ticket_line_item->type()
+				)
+			);
+		}
+		if ($ticket_line_item->quantity() < $qty) {
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'Can not cancel %1$d ticket(s) because the supplied line item has a quantity of %2$d.',
+						'event_espresso'
+					),
+					$qty,
+					$ticket_line_item->quantity()
+				)
+			);
+		}
+		// decrement ticket quantity; don't rely on auto-fixing when recalculating totals to do this
+		$ticket_line_item->set_quantity($ticket_line_item->quantity() - $qty);
+		foreach ($ticket_line_item->children() as $child_line_item) {
+			if ($child_line_item->is_sub_line_item()
+				&& ! $child_line_item->is_percent()
+				&& ! $child_line_item->is_cancellation()
+			) {
+				$child_line_item->set_quantity($child_line_item->quantity() - $qty);
+			}
+		}
+		// get cancellation sub line item
+		$cancellation_line_item = EEH_Line_Item::get_descendants_of_type(
+			$ticket_line_item,
+			EEM_Line_Item::type_cancellation
+		);
+		$cancellation_line_item = reset($cancellation_line_item);
+		// verify that this ticket was indeed previously cancelled
+		if ($cancellation_line_item instanceof EE_Line_Item) {
+			// increment cancelled quantity
+			$cancellation_line_item->set_quantity($cancellation_line_item->quantity() + $qty);
+		} else {
+			// create cancellation sub line item
+			$cancellation_line_item = EE_Line_Item::new_instance(array(
+				'LIN_name'       => esc_html__('Cancellation', 'event_espresso'),
+				'LIN_desc'       => sprintf(
+					esc_html_x(
+						'Cancelled %1$s : %2$s',
+						'Cancelled Ticket Name : 2015-01-01 11:11',
+						'event_espresso'
+					),
+					$ticket_line_item->name(),
+					current_time(get_option('date_format') . ' ' . get_option('time_format'))
+				),
+				'LIN_unit_price' => 0, // $ticket_line_item->unit_price()
+				'LIN_quantity'   => $qty,
+				'LIN_is_taxable' => $ticket_line_item->is_taxable(),
+				'LIN_order'      => count($ticket_line_item->children()),
+				'LIN_total'      => 0, // $ticket_line_item->unit_price()
+				'LIN_type'       => EEM_Line_Item::type_cancellation,
+			));
+			$ticket_line_item->add_child_line_item($cancellation_line_item);
+		}
+		if ($ticket_line_item->save_this_and_descendants() > 0) {
+			// decrement parent line item quantity
+			$event_line_item = $ticket_line_item->parent();
+			if ($event_line_item instanceof EE_Line_Item
+				&& $event_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_EVENT
+			) {
+				$event_line_item->set_quantity($event_line_item->quantity() - $qty);
+				$event_line_item->save();
+			}
+			EEH_Line_Item::get_grand_total_and_recalculate_everything($ticket_line_item);
+			return true;
+		}
+		return false;
+	}
+
+
+	/**
+	 * reinstates (un-cancels?) a previously canceled ticket line item,
+	 * by incrementing it's quantity by 1, and decrementing it's "type_cancellation" sub-line-item.
+	 * ALL totals and subtotals will NEED TO BE UPDATED after performing this action
+	 *
+	 * @param EE_Line_Item $ticket_line_item
+	 * @param int          $qty
+	 * @return bool success
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function reinstate_canceled_ticket_line_item(EE_Line_Item $ticket_line_item, $qty = 1)
+	{
+		// validate incoming line_item
+		if ($ticket_line_item->OBJ_type() !== EEM_Line_Item::OBJ_TYPE_TICKET) {
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'The supplied line item must have an Object Type of "Ticket", not %1$s.',
+						'event_espresso'
+					),
+					$ticket_line_item->type()
+				)
+			);
+		}
+		// get cancellation sub line item
+		$cancellation_line_item = EEH_Line_Item::get_descendants_of_type(
+			$ticket_line_item,
+			EEM_Line_Item::type_cancellation
+		);
+		$cancellation_line_item = reset($cancellation_line_item);
+		// verify that this ticket was indeed previously cancelled
+		if (! $cancellation_line_item instanceof EE_Line_Item) {
+			return false;
+		}
+		if ($cancellation_line_item->quantity() > $qty) {
+			// decrement cancelled quantity
+			$cancellation_line_item->set_quantity($cancellation_line_item->quantity() - $qty);
+		} elseif ($cancellation_line_item->quantity() === $qty) {
+			// decrement cancelled quantity in case anyone still has the object kicking around
+			$cancellation_line_item->set_quantity($cancellation_line_item->quantity() - $qty);
+			// delete because quantity will end up as 0
+			$cancellation_line_item->delete();
+			// and attempt to destroy the object,
+			// even though PHP won't actually destroy it until it needs the memory
+			unset($cancellation_line_item);
+		} else {
+			// what ?!?! negative quantity ?!?!
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'Can not reinstate %1$d cancelled ticket(s) because the cancelled ticket quantity is only %2$d.',
+						'event_espresso'
+					),
+					$qty,
+					$cancellation_line_item->quantity()
+				)
+			);
+		}
+		// increment ticket quantity
+		$ticket_line_item->set_quantity($ticket_line_item->quantity() + $qty);
+		if ($ticket_line_item->save_this_and_descendants() > 0) {
+			// increment parent line item quantity
+			$event_line_item = $ticket_line_item->parent();
+			if ($event_line_item instanceof EE_Line_Item
+				&& $event_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_EVENT
+			) {
+				$event_line_item->set_quantity($event_line_item->quantity() + $qty);
+			}
+			EEH_Line_Item::get_grand_total_and_recalculate_everything($ticket_line_item);
+			return true;
+		}
+		return false;
+	}
+
+
+	/**
+	 * calls EEH_Line_Item::find_transaction_grand_total_for_line_item()
+	 * then EE_Line_Item::recalculate_total_including_taxes() on the result
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @return float
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_grand_total_and_recalculate_everything(EE_Line_Item $line_item)
+	{
+		$grand_total_line_item = EEH_Line_Item::find_transaction_grand_total_for_line_item($line_item);
+		return $grand_total_line_item->recalculate_total_including_taxes();
+	}
+
+
+	/**
+	 * Gets the line item which contains the subtotal of all the items
+	 *
+	 * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_pre_tax_subtotal(EE_Line_Item $total_line_item)
+	{
+		$pre_tax_subtotal = $total_line_item->get_child_line_item('pre-tax-subtotal');
+		return $pre_tax_subtotal instanceof EE_Line_Item
+			? $pre_tax_subtotal
+			: self::create_pre_tax_subtotal($total_line_item);
+	}
+
+
+	/**
+	 * Gets the line item for the taxes subtotal
+	 *
+	 * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_taxes_subtotal(EE_Line_Item $total_line_item)
+	{
+		$taxes = $total_line_item->get_child_line_item('taxes');
+		return $taxes ? $taxes : self::create_taxes_subtotal($total_line_item);
+	}
+
+
+	/**
+	 * sets the TXN ID on an EE_Line_Item if passed a valid EE_Transaction object
+	 *
+	 * @param EE_Line_Item   $line_item
+	 * @param EE_Transaction $transaction
+	 * @return void
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function set_TXN_ID(EE_Line_Item $line_item, $transaction = null)
+	{
+		if ($transaction) {
+			/** @type EEM_Transaction $EEM_Transaction */
+			$EEM_Transaction = EE_Registry::instance()->load_model('Transaction');
+			$TXN_ID = $EEM_Transaction->ensure_is_ID($transaction);
+			$line_item->set_TXN_ID($TXN_ID);
+		}
+	}
+
+
+	/**
+	 * Creates a new default total line item for the transaction,
+	 * and its tickets subtotal and taxes subtotal line items (and adds the
+	 * existing taxes as children of the taxes subtotal line item)
+	 *
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item of type total
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_total_line_item($transaction = null)
+	{
+		$total_line_item = EE_Line_Item::new_instance(array(
+			'LIN_code' => 'total',
+			'LIN_name' => esc_html__('Grand Total', 'event_espresso'),
+			'LIN_type' => EEM_Line_Item::type_total,
+			'OBJ_type' => EEM_Line_Item::OBJ_TYPE_TRANSACTION,
+		));
+		$total_line_item = apply_filters(
+			'FHEE__EEH_Line_Item__create_total_line_item__total_line_item',
+			$total_line_item
+		);
+		self::set_TXN_ID($total_line_item, $transaction);
+		self::create_pre_tax_subtotal($total_line_item, $transaction);
+		self::create_taxes_subtotal($total_line_item, $transaction);
+		return $total_line_item;
+	}
+
+
+	/**
+	 * Creates a default items subtotal line item
+	 *
+	 * @param EE_Line_Item   $total_line_item
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	protected static function create_pre_tax_subtotal(EE_Line_Item $total_line_item, $transaction = null)
+	{
+		$pre_tax_line_item = EE_Line_Item::new_instance(array(
+			'LIN_code' => 'pre-tax-subtotal',
+			'LIN_name' => esc_html__('Pre-Tax Subtotal', 'event_espresso'),
+			'LIN_type' => EEM_Line_Item::type_sub_total,
+		));
+		$pre_tax_line_item = apply_filters(
+			'FHEE__EEH_Line_Item__create_pre_tax_subtotal__pre_tax_line_item',
+			$pre_tax_line_item
+		);
+		self::set_TXN_ID($pre_tax_line_item, $transaction);
+		$total_line_item->add_child_line_item($pre_tax_line_item);
+		self::create_event_subtotal($pre_tax_line_item, $transaction);
+		return $pre_tax_line_item;
+	}
+
+
+	/**
+	 * Creates a line item for the taxes subtotal and finds all the tax prices
+	 * and applies taxes to it
+	 *
+	 * @param EE_Line_Item   $total_line_item of type EEM_Line_Item::type_total
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	protected static function create_taxes_subtotal(EE_Line_Item $total_line_item, $transaction = null)
+	{
+		$tax_line_item = EE_Line_Item::new_instance(array(
+			'LIN_code'  => 'taxes',
+			'LIN_name'  => esc_html__('Taxes', 'event_espresso'),
+			'LIN_type'  => EEM_Line_Item::type_tax_sub_total,
+			'LIN_order' => 1000,// this should always come last
+		));
+		$tax_line_item = apply_filters(
+			'FHEE__EEH_Line_Item__create_taxes_subtotal__tax_line_item',
+			$tax_line_item
+		);
+		self::set_TXN_ID($tax_line_item, $transaction);
+		$total_line_item->add_child_line_item($tax_line_item);
+		// and lastly, add the actual taxes
+		self::apply_taxes($total_line_item);
+		return $tax_line_item;
+	}
+
+
+	/**
+	 * Creates a default items subtotal line item
+	 *
+	 * @param EE_Line_Item   $pre_tax_line_item
+	 * @param EE_Transaction $transaction
+	 * @param EE_Event       $event
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_event_subtotal(EE_Line_Item $pre_tax_line_item, $transaction = null, $event = null)
+	{
+		$event_line_item = EE_Line_Item::new_instance(array(
+			'LIN_code' => self::get_event_code($event),
+			'LIN_name' => self::get_event_name($event),
+			'LIN_desc' => self::get_event_desc($event),
+			'LIN_type' => EEM_Line_Item::type_sub_total,
+			'OBJ_type' => EEM_Line_Item::OBJ_TYPE_EVENT,
+			'OBJ_ID'   => $event instanceof EE_Event ? $event->ID() : 0,
+		));
+		$event_line_item = apply_filters(
+			'FHEE__EEH_Line_Item__create_event_subtotal__event_line_item',
+			$event_line_item
+		);
+		self::set_TXN_ID($event_line_item, $transaction);
+		$pre_tax_line_item->add_child_line_item($event_line_item);
+		return $event_line_item;
+	}
+
+
+	/**
+	 * Gets what the event ticket's code SHOULD be
+	 *
+	 * @param EE_Event $event
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public static function get_event_code($event)
+	{
+		return 'event-' . ($event instanceof EE_Event ? $event->ID() : '0');
+	}
+
+
+	/**
+	 * Gets the event name
+	 *
+	 * @param EE_Event $event
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public static function get_event_name($event)
+	{
+		return $event instanceof EE_Event
+			? mb_substr($event->name(), 0, 245)
+			: esc_html__('Event', 'event_espresso');
+	}
+
+
+	/**
+	 * Gets the event excerpt
+	 *
+	 * @param EE_Event $event
+	 * @return string
+	 * @throws EE_Error
+	 */
+	public static function get_event_desc($event)
+	{
+		return $event instanceof EE_Event ? $event->short_description() : '';
+	}
+
+
+	/**
+	 * Given the grand total line item and a ticket, finds the event sub-total
+	 * line item the ticket's purchase should be added onto
+	 *
+	 * @access public
+	 * @param EE_Line_Item $grand_total the grand total line item
+	 * @param EE_Ticket    $ticket
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_event_line_item_for_ticket(EE_Line_Item $grand_total, EE_Ticket $ticket)
+	{
+		$first_datetime = $ticket->first_datetime();
+		if (! $first_datetime instanceof EE_Datetime) {
+			throw new EE_Error(
+				sprintf(
+					__('The supplied ticket (ID %d) has no datetimes', 'event_espresso'),
+					$ticket->ID()
+				)
+			);
+		}
+		$event = $first_datetime->event();
+		if (! $event instanceof EE_Event) {
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'The supplied ticket (ID %d) has no event data associated with it.',
+						'event_espresso'
+					),
+					$ticket->ID()
+				)
+			);
+		}
+		$events_sub_total = EEH_Line_Item::get_event_line_item($grand_total, $event);
+		if (! $events_sub_total instanceof EE_Line_Item) {
+			throw new EE_Error(
+				sprintf(
+					esc_html__(
+						'There is no events sub-total for ticket %s on total line item %d',
+						'event_espresso'
+					),
+					$ticket->ID(),
+					$grand_total->ID()
+				)
+			);
+		}
+		return $events_sub_total;
+	}
+
+
+	/**
+	 * Gets the event line item
+	 *
+	 * @param EE_Line_Item $grand_total
+	 * @param EE_Event     $event
+	 * @return EE_Line_Item for the event subtotal which is a child of $grand_total
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_event_line_item(EE_Line_Item $grand_total, $event)
+	{
+		/** @type EE_Event $event */
+		$event = EEM_Event::instance()->ensure_is_obj($event, true);
+		$event_line_item = null;
+		$found = false;
+		foreach (EEH_Line_Item::get_event_subtotals($grand_total) as $event_line_item) {
+			// default event subtotal, we should only ever find this the first time this method is called
+			if (! $event_line_item->OBJ_ID()) {
+				// let's use this! but first... set the event details
+				EEH_Line_Item::set_event_subtotal_details($event_line_item, $event);
+				$found = true;
+				break;
+			}
+			if ($event_line_item->OBJ_ID() === $event->ID()) {
+				// found existing line item for this event in the cart, so break out of loop and use this one
+				$found = true;
+				break;
+			}
+		}
+		if (! $found) {
+			// there is no event sub-total yet, so add it
+			$pre_tax_subtotal = EEH_Line_Item::get_pre_tax_subtotal($grand_total);
+			// create a new "event" subtotal below that
+			$event_line_item = EEH_Line_Item::create_event_subtotal($pre_tax_subtotal, null, $event);
+			// and set the event details
+			EEH_Line_Item::set_event_subtotal_details($event_line_item, $event);
+		}
+		return $event_line_item;
+	}
+
+
+	/**
+	 * Creates a default items subtotal line item
+	 *
+	 * @param EE_Line_Item   $event_line_item
+	 * @param EE_Event       $event
+	 * @param EE_Transaction $transaction
+	 * @return void
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function set_event_subtotal_details(
+		EE_Line_Item $event_line_item,
+		EE_Event $event,
+		$transaction = null
+	) {
+		if ($event instanceof EE_Event) {
+			$event_line_item->set_code(self::get_event_code($event));
+			$event_line_item->set_name(self::get_event_name($event));
+			$event_line_item->set_desc(self::get_event_desc($event));
+			$event_line_item->set_OBJ_ID($event->ID());
+		}
+		self::set_TXN_ID($event_line_item, $transaction);
+	}
+
+
+	/**
+	 * Finds what taxes should apply, adds them as tax line items under the taxes sub-total,
+	 * and recalculates the taxes sub-total and the grand total. Resets the taxes, so
+	 * any old taxes are removed
+	 *
+	 * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
+	 * @param bool         $update_txn_status
+	 * @return bool
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 * @throws RuntimeException
+	 */
+	public static function apply_taxes(EE_Line_Item $total_line_item, $update_txn_status = false)
+	{
+		/** @type EEM_Price $EEM_Price */
+		$EEM_Price = EE_Registry::instance()->load_model('Price');
+		// get array of taxes via Price Model
+		$ordered_taxes = $EEM_Price->get_all_prices_that_are_taxes();
+		ksort($ordered_taxes);
+		$taxes_line_item = self::get_taxes_subtotal($total_line_item);
+		// just to be safe, remove its old tax line items
+		$deleted = $taxes_line_item->delete_children_line_items();
+		$updates = false;
+		// loop thru taxes
+		foreach ($ordered_taxes as $order => $taxes) {
+			foreach ($taxes as $tax) {
+				if ($tax instanceof EE_Price) {
+					$tax_line_item = EE_Line_Item::new_instance(
+						array(
+							'LIN_name'       => $tax->name(),
+							'LIN_desc'       => $tax->desc(),
+							'LIN_percent'    => $tax->amount(),
+							'LIN_is_taxable' => false,
+							'LIN_order'      => $order,
+							'LIN_total'      => 0,
+							'LIN_type'       => EEM_Line_Item::type_tax,
+							'OBJ_type'       => EEM_Line_Item::OBJ_TYPE_PRICE,
+							'OBJ_ID'         => $tax->ID(),
+						)
+					);
+					$tax_line_item = apply_filters(
+						'FHEE__EEH_Line_Item__apply_taxes__tax_line_item',
+						$tax_line_item
+					);
+					$updates = $taxes_line_item->add_child_line_item($tax_line_item) ?
+						true :
+						$updates;
+				}
+			}
+		}
+		// only recalculate totals if something changed
+		if ($deleted || $updates) {
+			$total_line_item->recalculate_total_including_taxes($update_txn_status);
+			return true;
+		}
+		return false;
+	}
+
+
+	/**
+	 * Ensures that taxes have been applied to the order, if not applies them.
+	 * Returns the total amount of tax
+	 *
+	 * @param EE_Line_Item $total_line_item of type EEM_Line_Item::type_total
+	 * @return float
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function ensure_taxes_applied($total_line_item)
+	{
+		$taxes_subtotal = self::get_taxes_subtotal($total_line_item);
+		if (! $taxes_subtotal->children()) {
+			self::apply_taxes($total_line_item);
+		}
+		return $taxes_subtotal->total();
+	}
+
+
+	/**
+	 * Deletes ALL children of the passed line item
+	 *
+	 * @param EE_Line_Item $parent_line_item
+	 * @return bool
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function delete_all_child_items(EE_Line_Item $parent_line_item)
+	{
+		$deleted = 0;
+		foreach ($parent_line_item->children() as $child_line_item) {
+			if ($child_line_item instanceof EE_Line_Item) {
+				$deleted += EEH_Line_Item::delete_all_child_items($child_line_item);
+				if ($child_line_item->ID()) {
+					$child_line_item->delete();
+					unset($child_line_item);
+				} else {
+					$parent_line_item->delete_child_line_item($child_line_item->code());
+				}
+				$deleted++;
+			}
+		}
+		return $deleted;
+	}
+
+
+	/**
+	 * Deletes the line items as indicated by the line item code(s) provided,
+	 * regardless of where they're found in the line item tree. Automatically
+	 * re-calculates the line item totals and updates the related transaction. But
+	 * DOES NOT automatically upgrade the transaction's registrations' final prices (which
+	 * should probably change because of this).
+	 * You should call EE_Registration_Processor::calculate_reg_final_prices_per_line_item()
+	 * after using this, to keep the registration final prices in-sync with the transaction's total.
+	 *
+	 * @param EE_Line_Item      $total_line_item of type EEM_Line_Item::type_total
+	 * @param array|bool|string $line_item_codes
+	 * @return int number of items successfully removed
+	 * @throws EE_Error
+	 */
+	public static function delete_items(EE_Line_Item $total_line_item, $line_item_codes = false)
+	{
+
+		if ($total_line_item->type() !== EEM_Line_Item::type_total) {
+			EE_Error::doing_it_wrong(
+				'EEH_Line_Item::delete_items',
+				esc_html__(
+					'This static method should only be called with a TOTAL line item, otherwise we won\'t recalculate the totals correctly',
+					'event_espresso'
+				),
+				'4.6.18'
+			);
+		}
+		do_action('AHEE_log', __FILE__, __FUNCTION__, '');
+
+		// check if only a single line_item_id was passed
+		if (! empty($line_item_codes) && ! is_array($line_item_codes)) {
+			// place single line_item_id in an array to appear as multiple line_item_ids
+			$line_item_codes = array($line_item_codes);
+		}
+		$removals = 0;
+		// cycle thru line_item_ids
+		foreach ($line_item_codes as $line_item_id) {
+			$removals += $total_line_item->delete_child_line_item($line_item_id);
+		}
+
+		if ($removals > 0) {
+			$total_line_item->recalculate_taxes_and_tax_total();
+			return $removals;
+		} else {
+			return false;
+		}
+	}
+
+
+	/**
+	 * Overwrites the previous tax by clearing out the old taxes, and creates a new
+	 * tax and updates the total line item accordingly
+	 *
+	 * @param EE_Line_Item $total_line_item
+	 * @param float        $amount
+	 * @param string       $name
+	 * @param string       $description
+	 * @param string       $code
+	 * @param boolean      $add_to_existing_line_item
+	 *                          if true, and a duplicate line item with the same code is found,
+	 *                          $amount will be added onto it; otherwise will simply set the taxes to match $amount
+	 * @return EE_Line_Item the new tax line item created
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function set_total_tax_to(
+		EE_Line_Item $total_line_item,
+		$amount,
+		$name = null,
+		$description = null,
+		$code = null,
+		$add_to_existing_line_item = false
+	) {
+		$tax_subtotal = self::get_taxes_subtotal($total_line_item);
+		$taxable_total = $total_line_item->taxable_total();
+
+		if ($add_to_existing_line_item) {
+			$new_tax = $tax_subtotal->get_child_line_item($code);
+			EEM_Line_Item::instance()->delete(
+				array(array('LIN_code' => array('!=', $code), 'LIN_parent' => $tax_subtotal->ID()))
+			);
+		} else {
+			$new_tax = null;
+			$tax_subtotal->delete_children_line_items();
+		}
+		if ($new_tax) {
+			$new_tax->set_total($new_tax->total() + $amount);
+			$new_tax->set_percent($taxable_total ? $new_tax->total() / $taxable_total * 100 : 0);
+		} else {
+			// no existing tax item. Create it
+			$new_tax = EE_Line_Item::new_instance(array(
+				'TXN_ID'      => $total_line_item->TXN_ID(),
+				'LIN_name'    => $name ? $name : esc_html__('Tax', 'event_espresso'),
+				'LIN_desc'    => $description ? $description : '',
+				'LIN_percent' => $taxable_total ? ($amount / $taxable_total * 100) : 0,
+				'LIN_total'   => $amount,
+				'LIN_parent'  => $tax_subtotal->ID(),
+				'LIN_type'    => EEM_Line_Item::type_tax,
+				'LIN_code'    => $code,
+			));
+		}
+
+		$new_tax = apply_filters(
+			'FHEE__EEH_Line_Item__set_total_tax_to__new_tax_subtotal',
+			$new_tax,
+			$total_line_item
+		);
+		$new_tax->save();
+		$tax_subtotal->set_total($new_tax->total());
+		$tax_subtotal->save();
+		$total_line_item->recalculate_total_including_taxes();
+		return $new_tax;
+	}
+
+
+	/**
+	 * Makes all the line items which are children of $line_item taxable (or not).
+	 * Does NOT save the line items
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @param boolean      $taxable
+	 * @param string       $code_substring_for_whitelist if this string is part of the line item's code
+	 *                                                   it will be whitelisted (ie, except from becoming taxable)
+	 * @throws EE_Error
+	 */
+	public static function set_line_items_taxable(
+		EE_Line_Item $line_item,
+		$taxable = true,
+		$code_substring_for_whitelist = null
+	) {
+		$whitelisted = false;
+		if ($code_substring_for_whitelist !== null) {
+			$whitelisted = strpos($line_item->code(), $code_substring_for_whitelist) !== false;
+		}
+		if (! $whitelisted && $line_item->is_line_item()) {
+			$line_item->set_is_taxable($taxable);
+		}
+		foreach ($line_item->children() as $child_line_item) {
+			EEH_Line_Item::set_line_items_taxable(
+				$child_line_item,
+				$taxable,
+				$code_substring_for_whitelist
+			);
+		}
+	}
+
+
+	/**
+	 * Gets all descendants that are event subtotals
+	 *
+	 * @uses  EEH_Line_Item::get_subtotals_of_object_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_event_subtotals(EE_Line_Item $parent_line_item)
+	{
+		return self::get_subtotals_of_object_type($parent_line_item, EEM_Line_Item::OBJ_TYPE_EVENT);
+	}
+
+
+	/**
+	 * Gets all descendants subtotals that match the supplied object type
+	 *
+	 * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $obj_type
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_subtotals_of_object_type(EE_Line_Item $parent_line_item, $obj_type = '')
+	{
+		return self::_get_descendants_by_type_and_object_type(
+			$parent_line_item,
+			EEM_Line_Item::type_sub_total,
+			$obj_type
+		);
+	}
+
+
+	/**
+	 * Gets all descendants that are tickets
+	 *
+	 * @uses  EEH_Line_Item::get_line_items_of_object_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_ticket_line_items(EE_Line_Item $parent_line_item)
+	{
+		return self::get_line_items_of_object_type(
+			$parent_line_item,
+			EEM_Line_Item::OBJ_TYPE_TICKET
+		);
+	}
+
+
+	/**
+	 * Gets all descendants subtotals that match the supplied object type
+	 *
+	 * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $obj_type
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_line_items_of_object_type(EE_Line_Item $parent_line_item, $obj_type = '')
+	{
+		return self::_get_descendants_by_type_and_object_type(
+			$parent_line_item,
+			EEM_Line_Item::type_line_item,
+			$obj_type
+		);
+	}
+
+
+	/**
+	 * Gets all the descendants (ie, children or children of children etc) that are of the type 'tax'
+	 *
+	 * @uses  EEH_Line_Item::get_descendants_of_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_tax_descendants(EE_Line_Item $parent_line_item)
+	{
+		return EEH_Line_Item::get_descendants_of_type(
+			$parent_line_item,
+			EEM_Line_Item::type_tax
+		);
+	}
+
+
+	/**
+	 * Gets all the real items purchased which are children of this item
+	 *
+	 * @uses  EEH_Line_Item::get_descendants_of_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_line_item_descendants(EE_Line_Item $parent_line_item)
+	{
+		return EEH_Line_Item::get_descendants_of_type(
+			$parent_line_item,
+			EEM_Line_Item::type_line_item
+		);
+	}
+
+
+	/**
+	 * Gets all descendants of supplied line item that match the supplied line item type
+	 *
+	 * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $line_item_type   one of the EEM_Line_Item constants
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_descendants_of_type(EE_Line_Item $parent_line_item, $line_item_type)
+	{
+		return self::_get_descendants_by_type_and_object_type(
+			$parent_line_item,
+			$line_item_type,
+			null
+		);
+	}
+
+
+	/**
+	 * Gets all descendants of supplied line item that match the supplied line item type and possibly the object type
+	 * as well
+	 *
+	 * @param EE_Line_Item  $parent_line_item - the line item to find descendants of
+	 * @param string        $line_item_type   one of the EEM_Line_Item constants
+	 * @param string | NULL $obj_type         object model class name (minus prefix) or NULL to ignore object type when
+	 *                                        searching
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	protected static function _get_descendants_by_type_and_object_type(
+		EE_Line_Item $parent_line_item,
+		$line_item_type,
+		$obj_type = null
+	) {
+		$objects = array();
+		foreach ($parent_line_item->children() as $child_line_item) {
+			if ($child_line_item instanceof EE_Line_Item) {
+				if ($child_line_item->type() === $line_item_type
+					&& (
+						$child_line_item->OBJ_type() === $obj_type || $obj_type === null
+					)
+				) {
+					$objects[] = $child_line_item;
+				} else {
+					// go-through-all-its children looking for more matches
+					$objects = array_merge(
+						$objects,
+						self::_get_descendants_by_type_and_object_type(
+							$child_line_item,
+							$line_item_type,
+							$obj_type
+						)
+					);
+				}
+			}
+		}
+		return $objects;
+	}
+
+
+	/**
+	 * Gets all descendants subtotals that match the supplied object type
+	 *
+	 * @uses  EEH_Line_Item::_get_descendants_by_type_and_object_type()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $OBJ_type         object type (like Event)
+	 * @param array        $OBJ_IDs          array of OBJ_IDs
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	public static function get_line_items_by_object_type_and_IDs(
+		EE_Line_Item $parent_line_item,
+		$OBJ_type = '',
+		$OBJ_IDs = array()
+	) {
+		return self::_get_descendants_by_object_type_and_object_ID(
+			$parent_line_item,
+			$OBJ_type,
+			$OBJ_IDs
+		);
+	}
+
+
+	/**
+	 * Gets all descendants of supplied line item that match the supplied line item type and possibly the object type
+	 * as well
+	 *
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $OBJ_type         object type (like Event)
+	 * @param array        $OBJ_IDs          array of OBJ_IDs
+	 * @return EE_Line_Item[]
+	 * @throws EE_Error
+	 */
+	protected static function _get_descendants_by_object_type_and_object_ID(
+		EE_Line_Item $parent_line_item,
+		$OBJ_type,
+		$OBJ_IDs
+	) {
+		$objects = array();
+		foreach ($parent_line_item->children() as $child_line_item) {
+			if ($child_line_item instanceof EE_Line_Item) {
+				if ($child_line_item->OBJ_type() === $OBJ_type
+					&& is_array($OBJ_IDs)
+					&& in_array($child_line_item->OBJ_ID(), $OBJ_IDs)
+				) {
+					$objects[] = $child_line_item;
+				} else {
+					// go-through-all-its children looking for more matches
+					$objects = array_merge(
+						$objects,
+						self::_get_descendants_by_object_type_and_object_ID(
+							$child_line_item,
+							$OBJ_type,
+							$OBJ_IDs
+						)
+					);
+				}
+			}
+		}
+		return $objects;
+	}
+
+
+	/**
+	 * Uses a breadth-first-search in order to find the nearest descendant of
+	 * the specified type and returns it, else NULL
+	 *
+	 * @uses  EEH_Line_Item::_get_nearest_descendant()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $type             like one of the EEM_Line_Item::type_*
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_nearest_descendant_of_type(EE_Line_Item $parent_line_item, $type)
+	{
+		return self::_get_nearest_descendant($parent_line_item, 'LIN_type', $type);
+	}
+
+
+	/**
+	 * Uses a breadth-first-search in order to find the nearest descendant
+	 * having the specified LIN_code and returns it, else NULL
+	 *
+	 * @uses  EEH_Line_Item::_get_nearest_descendant()
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $code             any value used for LIN_code
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_nearest_descendant_having_code(EE_Line_Item $parent_line_item, $code)
+	{
+		return self::_get_nearest_descendant($parent_line_item, 'LIN_code', $code);
+	}
+
+
+	/**
+	 * Uses a breadth-first-search in order to find the nearest descendant
+	 * having the specified LIN_code and returns it, else NULL
+	 *
+	 * @param EE_Line_Item $parent_line_item - the line item to find descendants of
+	 * @param string       $search_field     name of EE_Line_Item property
+	 * @param string       $value            any value stored in $search_field
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	protected static function _get_nearest_descendant(EE_Line_Item $parent_line_item, $search_field, $value)
+	{
+		foreach ($parent_line_item->children() as $child) {
+			if ($child->get($search_field) == $value) {
+				return $child;
+			}
+		}
+		foreach ($parent_line_item->children() as $child) {
+			$descendant_found = self::_get_nearest_descendant(
+				$child,
+				$search_field,
+				$value
+			);
+			if ($descendant_found) {
+				return $descendant_found;
+			}
+		}
+		return null;
+	}
+
+
+	/**
+	 * if passed line item has a TXN ID, uses that to jump directly to the grand total line item for the transaction,
+	 * else recursively walks up the line item tree until a parent of type total is found,
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 */
+	public static function find_transaction_grand_total_for_line_item(EE_Line_Item $line_item)
+	{
+		if ($line_item->TXN_ID()) {
+			$total_line_item = $line_item->transaction()->total_line_item(false);
+			if ($total_line_item instanceof EE_Line_Item) {
+				return $total_line_item;
+			}
+		} else {
+			$line_item_parent = $line_item->parent();
+			if ($line_item_parent instanceof EE_Line_Item) {
+				if ($line_item_parent->is_total()) {
+					return $line_item_parent;
+				}
+				return EEH_Line_Item::find_transaction_grand_total_for_line_item($line_item_parent);
+			}
+		}
+		throw new EE_Error(
+			sprintf(
+				esc_html__(
+					'A valid grand total for line item %1$d was not found.',
+					'event_espresso'
+				),
+				$line_item->ID()
+			)
+		);
+	}
+
+
+	/**
+	 * Prints out a representation of the line item tree
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @param int          $indentation
+	 * @return void
+	 * @throws EE_Error
+	 */
+	public static function visualize(EE_Line_Item $line_item, $indentation = 0)
+	{
+		echo defined('EE_TESTS_DIR') ? "\n" : '<br />';
+		if (! $indentation) {
+			echo defined('EE_TESTS_DIR') ? "\n" : '<br />';
+		}
+		for ($i = 0; $i < $indentation; $i++) {
+			echo '. ';
+		}
+		$breakdown = '';
+		if ($line_item->is_line_item()) {
+			if ($line_item->is_percent()) {
+				$breakdown = "{$line_item->percent()}%";
+			} else {
+				$breakdown = '$' . "{$line_item->unit_price()} x {$line_item->quantity()}";
+			}
+		}
+		echo $line_item->name();
+		echo " [ ID:{$line_item->ID()} | qty:{$line_item->quantity()} ] {$line_item->type()} : ";
+		echo '$' . (string) $line_item->total();
+		if ($breakdown) {
+			echo " ( {$breakdown} )";
+		}
+		if ($line_item->is_taxable()) {
+			echo '  * taxable';
+		}
+		if ($line_item->children()) {
+			foreach ($line_item->children() as $child) {
+				self::visualize($child, $indentation + 1);
+			}
+		}
+	}
+
+
+	/**
+	 * Calculates the registration's final price, taking into account that they
+	 * need to not only help pay for their OWN ticket, but also any transaction-wide surcharges and taxes,
+	 * and receive a portion of any transaction-wide discounts.
+	 * eg1, if I buy a $1 ticket and brent buys a $9 ticket, and we receive a $5 discount
+	 * then I'll get 1/10 of that $5 discount, which is $0.50, and brent will get
+	 * 9/10ths of that $5 discount, which is $4.50. So my final price should be $0.50
+	 * and brent's final price should be $5.50.
+	 * In order to do this, we basically need to traverse the line item tree calculating
+	 * the running totals (just as if we were recalculating the total), but when we identify
+	 * regular line items, we need to keep track of their share of the grand total.
+	 * Also, we need to keep track of the TAXABLE total for each ticket purchase, so
+	 * we can know how to apply taxes to it. (Note: "taxable total" does not equal the "pretax total"
+	 * when there are non-taxable items; otherwise they would be the same)
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @param array        $billable_ticket_quantities  array of EE_Ticket IDs and their corresponding quantity that
+	 *                                                  can be included in price calculations at this moment
+	 * @return array        keys are line items for tickets IDs and values are their share of the running total,
+	 *                                                  plus the key 'total', and 'taxable' which also has keys of all
+	 *                                                  the ticket IDs.
+	 *                                                  Eg array(
+	 *                                                      12 => 4.3
+	 *                                                      23 => 8.0
+	 *                                                      'total' => 16.6,
+	 *                                                      'taxable' => array(
+	 *                                                          12 => 10,
+	 *                                                          23 => 4
+	 *                                                      ).
+	 *                                                  So to find which registrations have which final price, we need
+	 *                                                  to find which line item is theirs, which can be done with
+	 *                                                  `EEM_Line_Item::instance()->get_line_item_for_registration(
+	 *                                                  $registration );`
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function calculate_reg_final_prices_per_line_item(
+		EE_Line_Item $line_item,
+		$billable_ticket_quantities = array()
+	) {
+		$running_totals = [
+			'total'   => 0,
+			'taxable' => ['total' => 0]
+		];
+		foreach ($line_item->children() as $child_line_item) {
+			switch ($child_line_item->type()) {
+				case EEM_Line_Item::type_sub_total:
+					$running_totals_from_subtotal = EEH_Line_Item::calculate_reg_final_prices_per_line_item(
+						$child_line_item,
+						$billable_ticket_quantities
+					);
+					// combine arrays but preserve numeric keys
+					$running_totals = array_replace_recursive($running_totals_from_subtotal, $running_totals);
+					$running_totals['total'] += $running_totals_from_subtotal['total'];
+					$running_totals['taxable']['total'] += $running_totals_from_subtotal['taxable']['total'];
+					break;
+
+				case EEM_Line_Item::type_tax_sub_total:
+					// find how much the taxes percentage is
+					if ($child_line_item->percent() !== 0) {
+						$tax_percent_decimal = $child_line_item->percent() / 100;
+					} else {
+						$tax_percent_decimal = EE_Taxes::get_total_taxes_percentage() / 100;
+					}
+					// and apply to all the taxable totals, and add to the pretax totals
+					foreach ($running_totals as $line_item_id => $this_running_total) {
+						// "total" and "taxable" array key is an exception
+						if ($line_item_id === 'taxable') {
+							continue;
+						}
+						$taxable_total = $running_totals['taxable'][ $line_item_id ];
+						$running_totals[ $line_item_id ] += ($taxable_total * $tax_percent_decimal);
+					}
+					break;
+
+				case EEM_Line_Item::type_line_item:
+					// ticket line items or ????
+					if ($child_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET) {
+						// kk it's a ticket
+						if (isset($running_totals[ $child_line_item->ID() ])) {
+							// huh? that shouldn't happen.
+							$running_totals['total'] += $child_line_item->total();
+						} else {
+							// its not in our running totals yet. great.
+							if ($child_line_item->is_taxable()) {
+								$taxable_amount = $child_line_item->unit_price();
+							} else {
+								$taxable_amount = 0;
+							}
+							// are we only calculating totals for some tickets?
+							if (isset($billable_ticket_quantities[ $child_line_item->OBJ_ID() ])) {
+								$quantity = $billable_ticket_quantities[ $child_line_item->OBJ_ID() ];
+								$running_totals[ $child_line_item->ID() ] = $quantity
+									? $child_line_item->unit_price()
+									: 0;
+								$running_totals['taxable'][ $child_line_item->ID() ] = $quantity
+									? $taxable_amount
+									: 0;
+							} else {
+								$quantity = $child_line_item->quantity();
+								$running_totals[ $child_line_item->ID() ] = $child_line_item->unit_price();
+								$running_totals['taxable'][ $child_line_item->ID() ] = $taxable_amount;
+							}
+							$running_totals['taxable']['total'] += $taxable_amount * $quantity;
+							$running_totals['total'] += $child_line_item->unit_price() * $quantity;
+						}
+					} else {
+						// it's some other type of item added to the cart
+						// it should affect the running totals
+						// basically we want to convert it into a PERCENT modifier. Because
+						// more clearly affect all registration's final price equally
+						$line_items_percent_of_running_total = $running_totals['total'] > 0
+							? ($child_line_item->total() / $running_totals['total']) + 1
+							: 1;
+						foreach ($running_totals as $line_item_id => $this_running_total) {
+							// the "taxable" array key is an exception
+							if ($line_item_id === 'taxable') {
+								continue;
+							}
+							// update the running totals
+							// yes this actually even works for the running grand total!
+							$running_totals[ $line_item_id ] =
+								$line_items_percent_of_running_total * $this_running_total;
+
+							if ($child_line_item->is_taxable()) {
+								$running_totals['taxable'][ $line_item_id ] =
+									$line_items_percent_of_running_total * $running_totals['taxable'][ $line_item_id ];
+							}
+						}
+					}
+					break;
+			}
+		}
+		return $running_totals;
+	}
+
+
+	/**
+	 * @param EE_Line_Item $total_line_item
+	 * @param EE_Line_Item $ticket_line_item
+	 * @return float | null
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws OutOfRangeException
+	 * @throws ReflectionException
+	 */
+	public static function calculate_final_price_for_ticket_line_item(
+		EE_Line_Item $total_line_item,
+		EE_Line_Item $ticket_line_item
+	) {
+		static $final_prices_per_ticket_line_item = array();
+		if (empty($final_prices_per_ticket_line_item) || empty($final_prices_per_ticket_line_item[$total_line_item->ID()])) {
+			$final_prices_per_ticket_line_item[$total_line_item->ID()] = EEH_Line_Item::calculate_reg_final_prices_per_line_item(
+				$total_line_item
+			);
+		}
+		// ok now find this new registration's final price
+		if (isset($final_prices_per_ticket_line_item[$total_line_item->ID() ][ $ticket_line_item->ID() ])) {
+			return $final_prices_per_ticket_line_item[$total_line_item ][ $ticket_line_item->ID() ];
+		}
+		$message = sprintf(
+			esc_html__(
+				'The final price for the ticket line item (ID:%1$d) could not be calculated.',
+				'event_espresso'
+			),
+			$ticket_line_item->ID()
+		);
+		if (WP_DEBUG) {
+			$message .= '<br>' . print_r($final_prices_per_ticket_line_item, true);
+			throw new OutOfRangeException($message);
+		}
+		EE_Log::instance()->log(__CLASS__, __FUNCTION__, $message);
+		return null;
+	}
+
+
+	/**
+	 * Creates a duplicate of the line item tree, except only includes billable items
+	 * and the portion of line items attributed to billable things
+	 *
+	 * @param EE_Line_Item      $line_item
+	 * @param EE_Registration[] $registrations
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function billable_line_item_tree(EE_Line_Item $line_item, $registrations)
+	{
+		$copy_li = EEH_Line_Item::billable_line_item($line_item, $registrations);
+		foreach ($line_item->children() as $child_li) {
+			$copy_li->add_child_line_item(
+				EEH_Line_Item::billable_line_item_tree($child_li, $registrations)
+			);
+		}
+		// if this is the grand total line item, make sure the totals all add up
+		// (we could have duplicated this logic AS we copied the line items, but
+		// it seems DRYer this way)
+		if ($copy_li->type() === EEM_Line_Item::type_total) {
+			$copy_li->recalculate_total_including_taxes();
+		}
+		return $copy_li;
+	}
+
+
+	/**
+	 * Creates a new, unsaved line item from $line_item that factors in the
+	 * number of billable registrations on $registrations.
+	 *
+	 * @param EE_Line_Item      $line_item
+	 * @param EE_Registration[] $registrations
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function billable_line_item(EE_Line_Item $line_item, $registrations)
+	{
+		$new_li_fields = $line_item->model_field_array();
+		if ($line_item->type() === EEM_Line_Item::type_line_item &&
+			$line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
+		) {
+			$count = 0;
+			foreach ($registrations as $registration) {
+				if ($line_item->OBJ_ID() === $registration->ticket_ID() &&
+					in_array(
+						$registration->status_ID(),
+						EEM_Registration::reg_statuses_that_allow_payment(),
+						true
+					)
+				) {
+					$count++;
+				}
+			}
+			$new_li_fields['LIN_quantity'] = $count;
+		}
+		// don't set the total. We'll leave that up to the code that calculates it
+		unset($new_li_fields['LIN_ID'], $new_li_fields['LIN_parent'], $new_li_fields['LIN_total']);
+		return EE_Line_Item::new_instance($new_li_fields);
+	}
+
+
+	/**
+	 * Returns a modified line item tree where all the subtotals which have a total of 0
+	 * are removed, and line items with a quantity of 0
+	 *
+	 * @param EE_Line_Item $line_item |null
+	 * @return EE_Line_Item|null
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function non_empty_line_items(EE_Line_Item $line_item)
+	{
+		$copied_li = EEH_Line_Item::non_empty_line_item($line_item);
+		if ($copied_li === null) {
+			return null;
+		}
+		// if this is an event subtotal, we want to only include it if it
+		// has a non-zero total and at least one ticket line item child
+		$ticket_children = 0;
+		foreach ($line_item->children() as $child_li) {
+			$child_li_copy = EEH_Line_Item::non_empty_line_items($child_li);
+			if ($child_li_copy !== null) {
+				$copied_li->add_child_line_item($child_li_copy);
+				if ($child_li_copy->type() === EEM_Line_Item::type_line_item &&
+					$child_li_copy->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
+				) {
+					$ticket_children++;
+				}
+			}
+		}
+		// if this is an event subtotal with NO ticket children
+		// we basically want to ignore it
+		if ($ticket_children === 0
+			&& $line_item->type() === EEM_Line_Item::type_sub_total
+			&& $line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_EVENT
+			&& $line_item->total() === 0
+		) {
+			return null;
+		}
+		return $copied_li;
+	}
+
+
+	/**
+	 * Creates a new, unsaved line item, but if it's a ticket line item
+	 * with a total of 0, or a subtotal of 0, returns null instead
+	 *
+	 * @param EE_Line_Item $line_item
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function non_empty_line_item(EE_Line_Item $line_item)
+	{
+		if ($line_item->type() === EEM_Line_Item::type_line_item
+			&& $line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
+			&& $line_item->quantity() === 0
+		) {
+			return null;
+		}
+		$new_li_fields = $line_item->model_field_array();
+		// don't set the total. We'll leave that up to the code that calculates it
+		unset($new_li_fields['LIN_ID'], $new_li_fields['LIN_parent']);
+		return EE_Line_Item::new_instance($new_li_fields);
+	}
+
+
+	/**
+	 * Cycles through all of the ticket line items for the supplied total line item
+	 * and ensures that the line item's "is_taxable" field matches that of its corresponding ticket
+	 *
+	 * @param EE_Line_Item $total_line_item
+	 * @since 4.9.79.p
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function resetIsTaxableForTickets(EE_Line_Item $total_line_item)
+	{
+		$ticket_line_items = self::get_ticket_line_items($total_line_item);
+		foreach ($ticket_line_items as $ticket_line_item) {
+			if ($ticket_line_item instanceof EE_Line_Item
+				&& $ticket_line_item->OBJ_type() === EEM_Line_Item::OBJ_TYPE_TICKET
+			) {
+				$ticket = $ticket_line_item->ticket();
+				if ($ticket instanceof EE_Ticket && $ticket->taxable() !== $ticket_line_item->is_taxable()) {
+					$ticket_line_item->set_is_taxable($ticket->taxable());
+					$ticket_line_item->save();
+				}
+			}
+		}
+	}
+
+
+
+	/**************************************** @DEPRECATED METHODS *************************************** */
+	/**
+	 * @deprecated
+	 * @param EE_Line_Item $total_line_item
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function get_items_subtotal(EE_Line_Item $total_line_item)
+	{
+		EE_Error::doing_it_wrong(
+			'EEH_Line_Item::get_items_subtotal()',
+			sprintf(
+				esc_html__('Method replaced with %1$s', 'event_espresso'),
+				'EEH_Line_Item::get_pre_tax_subtotal()'
+			),
+			'4.6.0'
+		);
+		return self::get_pre_tax_subtotal($total_line_item);
+	}
+
+
+	/**
+	 * @deprecated
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_default_total_line_item($transaction = null)
+	{
+		EE_Error::doing_it_wrong(
+			'EEH_Line_Item::create_default_total_line_item()',
+			sprintf(
+				esc_html__('Method replaced with %1$s', 'event_espresso'),
+				'EEH_Line_Item::create_total_line_item()'
+			),
+			'4.6.0'
+		);
+		return self::create_total_line_item($transaction);
+	}
+
+
+	/**
+	 * @deprecated
+	 * @param EE_Line_Item   $total_line_item
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_default_tickets_subtotal(EE_Line_Item $total_line_item, $transaction = null)
+	{
+		EE_Error::doing_it_wrong(
+			'EEH_Line_Item::create_default_tickets_subtotal()',
+			sprintf(
+				esc_html__('Method replaced with %1$s', 'event_espresso'),
+				'EEH_Line_Item::create_pre_tax_subtotal()'
+			),
+			'4.6.0'
+		);
+		return self::create_pre_tax_subtotal($total_line_item, $transaction);
+	}
+
+
+	/**
+	 * @deprecated
+	 * @param EE_Line_Item   $total_line_item
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_default_taxes_subtotal(EE_Line_Item $total_line_item, $transaction = null)
+	{
+		EE_Error::doing_it_wrong(
+			'EEH_Line_Item::create_default_taxes_subtotal()',
+			sprintf(
+				esc_html__('Method replaced with %1$s', 'event_espresso'),
+				'EEH_Line_Item::create_taxes_subtotal()'
+			),
+			'4.6.0'
+		);
+		return self::create_taxes_subtotal($total_line_item, $transaction);
+	}
+
+
+	/**
+	 * @deprecated
+	 * @param EE_Line_Item   $total_line_item
+	 * @param EE_Transaction $transaction
+	 * @return EE_Line_Item
+	 * @throws EE_Error
+	 * @throws InvalidArgumentException
+	 * @throws InvalidDataTypeException
+	 * @throws InvalidInterfaceException
+	 * @throws ReflectionException
+	 */
+	public static function create_default_event_subtotal(EE_Line_Item $total_line_item, $transaction = null)
+	{
+		EE_Error::doing_it_wrong(
+			'EEH_Line_Item::create_default_event_subtotal()',
+			sprintf(
+				esc_html__('Method replaced with %1$s', 'event_espresso'),
+				'EEH_Line_Item::create_event_subtotal()'
+			),
+			'4.6.0'
+		);
+		return self::create_event_subtotal($total_line_item, $transaction);
+	}
 }