Subtotal Merge Tag (for Calculations)

<?php
/**
* Calculation Subtotal Merge Tag 
* http://gravitywiz.com/
*/
class GWCalcSubtotal { 
    
    public static $merge_tag = '{subtotal}'; 
    
    function __construct() {
        
        // front-end
        add_filter( 'gform_pre_render', array( $this, 'maybe_replace_subtotal_merge_tag' ) );
        add_filter( 'gform_pre_submission_filter', array( $this, 'maybe_replace_subtotal_merge_tag' ) );
        
        // back-end
        add_filter( 'gform_admin_pre_render', array( $this, 'add_merge_tags' ) );
        
    }
    
    /**
    * Look for {subtotal} merge tag in form fields 'calculationFormula' property. If found, replace with the
    * aggregated subtotal merge tag string.
    * 
    * @param mixed $form
    */
    function maybe_replace_subtotal_merge_tag( $form ) {
        
        foreach( $form['fields'] as &$field ) {
            
            if( !self::has_subtotal_merge_tag( $field ) )
                continue;
            
            $subtotal_merge_tags = self::get_subtotal_merge_tag_string( $form, $field );
            $field['calculationFormula'] = str_replace( self::$merge_tag, $subtotal_merge_tags, $field['calculationFormula'] );
            
        }
        
        return $form;
    }
    
    /**
    * Get all the pricing fields on the form, get their corresponding merge tags and aggregate them into a formula that
    * will yeild the form's subtotal.
    * 
    * @param mixed $form
    */
    static function get_subtotal_merge_tag_string( $form, $current_field ) {
        
        $pricing_fields = self::get_pricing_fields( $form );
        $product_tag_groups = array();
        
        foreach( $pricing_fields['products'] as $product ) {
            
            $product_field = rgar( $product, 'product' );
            $option_fields = rgar( $product, 'options' );
            $quantity_field = rgar( $product, 'quantity' );
            
            // do not include current field in subtotal
            if( $product_field['id'] == $current_field['id'] )
                continue;
            
            $product_tags = GFCommon::get_field_merge_tags( $product_field );
            $quantity_tag = 1;
            
            // if a single product type, only get the "price" merge tag
            if( in_array( GFFormsModel::get_input_type( $product_field ), array( 'singleproduct', 'calculation' ) ) ) {
                
                // single products provide quantity merge tag
                if( empty( $quantity_field ) )
                    $quantity_tag = $product_tags[2]['tag'];
                
                $product_tags = array( $product_tags[1] );
            }
            
            // if quantity field is provided for product, get merge tag
            if( !empty( $quantity_field ) ) {
                $quantity_tag = GFCommon::get_field_merge_tags( $quantity_field );
                $quantity_tag = $quantity_tag[0]['tag'];
            }
            
            $product_tags = wp_list_pluck( $product_tags, 'tag' );
            $option_tags = array();
            
            foreach( $option_fields as $option_field ) {
                
                $new_options_tags = GFCommon::get_field_merge_tags( $option_field );
                if( !is_array( $new_options_tags ) )
                    continue;
                
                if( GFFormsModel::get_input_type( $option_field ) == 'checkbox' ) {
                    array_shift( $new_options_tags );    
                } else {
                    $new_options_tags = array( array_shift( $new_options_tags ) );
                }
                
                $option_tags = array_merge( $option_tags, $new_options_tags );
            }
            
            $option_tags = wp_list_pluck( $option_tags, 'tag' );
            
            $product_tag_groups[] = '( ( ' . implode( ' + ', array_merge( $product_tags, $option_tags ) ) . ' ) * ' . $quantity_tag . ' )';
            
        }
        
        $shipping_tag = 0;
        if( rgar( $pricing_fields, 'shipping' ) ) {
            $shipping_tag = GFCommon::get_field_merge_tags( rgars( $pricing_fields, 'shipping/0' ) );
            $shipping_tag = $shipping_tag[0]['tag'];
        }
        
        $pricing_tag_string = '( ( ' . implode( ' + ', $product_tag_groups ) . ' ) + ' . $shipping_tag . ' )';
        
        return $pricing_tag_string;
    }
    
    /**
    * Get all pricing fields from a given form object grouped by product and shipping with options nested under their 
    * respective products.
    * 
    * @param mixed $form
    */
    static function get_pricing_fields( $form ) {
    
        $product_fields = array();
 
        foreach( $form["fields"] as $field ) {
        
            if( $field["type"] != 'product' )
                continue;
                
            $option_fields = GFCommon::get_product_fields_by_type($form, array("option"), $field['id'] );
            
            // can only have 1 quantity field
            $quantity_field = GFCommon::get_product_fields_by_type( $form, array("quantity"), $field['id'] );
            $quantity_field = rgar( $quantity_field, 0 );
            
            $product_fields[] = array(
                'product' => $field,
                'options' => $option_fields,
                'quantity' => $quantity_field
                );
            
        }
 
        $shipping_field = GFCommon::get_fields_by_type($form, array("shipping"));
 
        return array( "products" => $product_fields, "shipping" => $shipping_field );
    }
    
    function add_merge_tags( $form ) {
        
        $label = __('Subtotal', 'gravityforms');
        
        ?>
        
        <script type="text/javascript">
            
            // for the future (not yet supported for calc field)
            gform.addFilter("gform_merge_tags", "gwcs_add_merge_tags");
            function gwcs_add_merge_tags( mergeTags, elementId, hideAllFields, excludeFieldTypes, isPrepop, option ) {
                console.log( elementId );
                mergeTags["pricing"].tags.push({ tag: '<?php echo self::$merge_tag; ?>', label: '<?php echo $label; ?>' });
                return mergeTags;
            }
            
            // hacky, but only temporary
            jQuery(document).ready(function($){
                
                var calcMergeTagSelect = $('#field_calculation_formula_variable_select');
                calcMergeTagSelect.find('optgroup').eq(0).append( '<option value="<?php echo self::$merge_tag; ?>"><?php echo $label; ?></option>' );
                
            });
            
        </script>
        
        <?php
        //return the form object from the php hook    
        return $form;
    }
    
    static function has_subtotal_merge_tag( $field ) {
        
        // check if form is passed
        if( isset( $field['fields'] ) ) {
            
            $form = $field;
            foreach( $form['fields'] as $field ) {
                if( self::has_subtotal_merge_tag( $field ) )
                    return true;
            }
            
        } else {
            
            if( isset( $field['calculationFormula'] ) && strpos( $field['calculationFormula'], self::$merge_tag ) !== false )
                return true;
                
        }
        
        return false;
    }
    
}
 
new GWCalcSubtotal();