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<?php
/**
 * Gravity Wiz // Gravity Forms // Set Number of List Field Rows by Field Value
 *
 * Add/remove list field rows automatically based on the value entered in the specified field. Removes the add/remove
 * that normally buttons next to List field rows.
 *
 * @version   1.3
 * @author    David Smith <david@gravitywiz.com>
 * @license   GPL-2.0+
 * @link      http://gravitywiz.com/2012/06/03/set-number-of-list-field-rows-by-field-value/
 */
class GWAutoListFieldRows {

	private static $_is_script_output;
	
	public function __construct( $args = array() ) {
 
		// set our default arguments, parse against the provided arguments, and store for use throughout the class
		$this->_args = wp_parse_args( $args, array(
			'form_id'       => false,
			'input_html_id' => false,
			'list_field_id' => false
		) );
 
		// do version check in the init to make sure if GF is going to be loaded, it is already loaded
		add_action( 'init', array( $this, 'init' ) );
 
	}
 
	public function init() {
 
		// make sure we're running the required minimum version of Gravity Forms
		if( ! property_exists( 'GFCommon', 'version' ) || ! version_compare( GFCommon::$version, '1.8', '>=' ) ) {
			return;
		}
 
		// time for hooks
		add_filter( 'gform_pre_render', array( $this, 'load_form_script' ), 10, 2 );
		add_filter( 'gform_register_init_scripts', array( $this, 'add_init_script' ), 10, 2 );
 
	}
 
	public function load_form_script( $form, $is_ajax_enabled ) {
 
		if( $this->is_applicable_form( $form ) && ! has_action( 'wp_footer', array( $this, 'output_script' ) ) ) {
			add_action( 'wp_footer', array( $this, 'output_script' ) );
			add_action( 'gform_preview_footer', array( $this, 'output_script' ) );
		}
 
		return $form;
	}
 
	public function output_script() {
		?>
 
		<script type="text/javascript">

            window.gwalfr;

            (function($){

                gwalfr = function( args ) {

                    this.formId      = args.formId,
                        this.listFieldId = args.listFieldId,
                        this.inputHtmlId = args.inputHtmlId;

                    this.init = function() {

                        var gwalfr = this,
                            triggerInput = $( this.inputHtmlId );

                        // update rows on page load
                        this.updateListItems( triggerInput, this.listFieldId, this.formId );

                        // update rows when field value changes
                        triggerInput.change(function(){
                            gwalfr.updateListItems( $(this), gwalfr.listFieldId, gwalfr.formId );
                        });

                    }

                    this.updateListItems = function( elem, listFieldId, formId ) {

                        var listField = $( '#field_' + formId + '_' + listFieldId ),
                            count = parseInt( elem.val() );
                        rowCount = listField.find( 'table.gfield_list tbody tr' ).length,
                            diff = count - rowCount;

                        if( diff > 0 ) {
                            for( var i = 0; i < diff; i++ ) {
                                listField.find( '.add_list_item:last' ).click();
                            }
                        } else {

                            // make sure we never delete all rows
                            if( rowCount + diff == 0 )
                                diff++;

                            for( var i = diff; i < 0; i++ ) {
                                listField.find( '.delete_list_item:last' ).click();
                            }

                        }
                    }

                    this.init();

                }

            })(jQuery);

		</script>
 
		<?php
	}
 
	public function add_init_script( $form ) {
 
		if( ! $this->is_applicable_form( $form ) ) {
			return;
		}
 
		$args = array(
			'formId'      => $this->_args['form_id'],
			'listFieldId' => $this->_args['list_field_id'],
			'inputHtmlId' => $this->_args['input_html_id']
		);

		$script = "new gwalfr(" . json_encode( $args ) . ");";
		$key = implode( '_', $args );

		GFFormDisplay::add_init_script( $form['id'], 'gwalfr_' . $key , GFFormDisplay::ON_PAGE_RENDER, $script );
	}
 
	public function is_applicable_form( $form ) {
 
		$form_id = isset( $form['id'] ) ? $form['id'] : $form;
 
		return empty( $this->_args['form_id'] ) || $form_id == $this->_args['form_id'];
	}
 
}

// EXAMPLE #1: Number field for the "input_html_id"
new GWAutoListFieldRows( array(
	'form_id' => 240,
	'list_field_id' => 3,
	'input_html_id' => '#input_240_4'
) );

// EXAMPLE #2: Single Product Field's Quantity input as the "input_html_id"
new GWAutoListFieldRows( array(
	'form_id' => 240,
	'list_field_id' => 6,
	'input_html_id' => '#ginput_quantity_240_5'
) );