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<?php
/**
 * WARNING! THIS SNIPPET MAY BE OUTDATED.
 * The latest version of this snippet can be found in the Gravity Wiz Snippet Library:
 * https://github.com/gravitywiz/snippet-library/blob/master/gravity-forms/gw-calculated-shipping.php
 */
/**
 * Gravity Wiz // Gravity Forms // Calculated Shipping
 *
 * A simple method for using a calculated product field as a shipping field. This provides the ability to use
 * calculations when determining a shipping price.
 *
 * @version   1.1
 * @author    David Smith <david@gravitywiz.com>
 * @license   GPL-2.0+
 * @link      http://gravitywiz.com/...
 * @copyright 2016 Gravity Wiz
 */
class GWCalculatedShipping {
    
    private $_orig_field = null;
    
    function __construct( $args ) {
        
        $this->_args = wp_parse_args( $args, array( 
            'form_id' => false,
            'field_id' => false
        ) );
        
        add_filter( 'gform_pre_validation', array( $this, 'add_shipping_field' ), 9 );
        add_filter( 'gform_pre_render', array( $this, 'restore_original_field' ), 11 );
        
    }
    
    function add_shipping_field( $form ) {
        
        if( $this->_args['form_id'] != $form['id'] ) {
	        return $form;
        }

        // get our calc shipping field and convert it to default shipping field
	    // REMINDER: PHP objects are always passed by reference
	    $field = GFFormsModel::get_field( $form, $this->_args['field_id'] );

	    // create a copy of the original field so that it can be restored if there is a validation error
	    $this->_orig_field = GF_Fields::create( $field );

	    $field->type = 'shipping';
	    $field->inputType = 'singleshipping';
	    $field->inputs = null;

	    $field = GF_Fields::create( $field );

        // map calc value as shipping value
        $_POST[ "input_{$field->id}" ] = rgpost( "input_{$field->id}_2" );

	    foreach( $form['fields'] as &$_field ) {
		    if( $_field->id == $field->id ) {
			    $_field = $field;
		    }
	    }

        return $form;
    }
    
    function field( $args = array() ) {
        return wp_parse_args( $args, array(
            'id' => false,
            'formId' => false,
            'pageNumber' => 1,
            'adminLabel' => '',
            'adminOnly' => '',
            'allowsPrepopulate' => 1,
            'defaultValue' => '',
            'description' => '',
            'content' => '',
            'cssClass' => '',
            'errorMessage' => '',
            'inputName' => '',
            'isRequired' => '',
            'label' => 'Shipping',
            'noDuplicates' => '',
            'size' => 'medium',
            'type' => 'shipping',
            'displayCaption' => '',
            'displayDescription' => '',
            'displayTitle' => '',
            'inputType' => 'singleshipping',
            'inputs' => '',
            'basePrice' => '$0.00'
        ) );
    }
    
    function restore_original_field( $form ) {
        
        if( $this->_args['form_id'] != $form['id'] || empty( $this->_orig_field ) ) {
	        return $form;
        }

        foreach( $form['fields'] as &$field ) {
            if( $field['id'] == $this->_orig_field['id'] ) {
	            $field = GF_Fields::create( $this->_orig_field );
                break;
            }
        }
        
        return $form;
    }
    
}

# Configuration

new GWCalculatedShipping( array(
    'form_id' => 1378,
    'field_id' => 1
) );