<?php

/**
 * PHP class for printing HTML form elements
 *
 * This class abstracts the functional elements of a form into units that 
 * are easily defined and edited within the context of a PHP script. This 
 * class is especially useful in cases where the content and elements of a 
 * form are only known at runtime, and facilitates a standardized approach 
 * to displaying forms. This first version of the class is focused on the 
 * form elements themselves; in future versions, methods for organizing 
 * elements and formatting forms will be included.
 *
 * Several non-standard form elements have been implemented, fusing an 
 * interrelated set of HTML tags and javascript into a functional unit that 
 * can be output with the same simplicity as any other form tag. This set 
 * of user-experience-centered form elements can be easily expanded by 
 * extending the class.
 *
 * This class was developed for use within the WordPress environment.
 *
 * USAGE
 * The class operates as a static factory, with each element called as a 
 * static method with the minimum necessary parameters as an associative 
 * array or get-request-like string in the WordPress style. The static 
 * method instantiates the element object, which itself remains protected. 
 * See the constructor method for details.
 *
 * Requires PHP Version 5.3 or greater
 * 
 * @category   
 * @package    WordPress
 * @author     Roland Barker <webdesign@xnau.com>
 * @copyright  2011, 2012, 2013, 2014, 2015 xnau webdesign
 * @license    GPL2
 * @version    1.13
 * @link       http://wordpress.org/extend/plugins/participants-database/
 *
 */
if ( !defined( 'ABSPATH' ) )
  die;
/*

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2, as
  published by the Free Software Foundation.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

abstract class xnau_FormElement {

  /**
   * defines the type of form element for the object
   *
   * @var string 
   */
  var $type;

  /**
   * holds the current value of the element
   *
   * @var string
   */
  var $value;

  /**
   * the name attribute of the form data field
   *
   * @var string
   */
  var $name;

  /**
   * for elements that have set options such as checkboxes and dropdowns, this 
   * array holds the name=>value pairs
   *
   * @var array
   */
  var $options;

  /**
   * holds any other html element attributes in name=>value pairs
   * 
   * @var array 
   */
  var $attributes = array();

  /**
   * @var array of class names
   */
  var $classes = array();

  /**
   * array holding the text lines of an element to be output
   *
   * @var array
   */
  var $output = array();

  /**
   * the size attribute of the input tag
   *
   * @var type 
   */
  var $size;

  /**
   * sets the height and width of the textarea element
   *
   * @var array
   */
  var $textarea_dims = array('rows' => 2, 'cols' => 40);

  /**
   * element group status
   * 
   * this pertains to elements which are part of a group of form elements sharing 
   * a common name, such as for multi-selects
   *
   * @var bool
   */
  public $group;

  /**
   * holds "inside wrapping tag" status
   * 
   * this is used in constructing complex elements that use wrapping tags such as 
   * optgroups
   * 
   * @var bool
   */
  var $inside = false;

  /**
   * @var string the linebreak character
   */
  const BR = PHP_EOL;

  /**
   * 
   * @var string the tab character
   */
  const TAB = "\t";

  /**
   * holds current indent level
   *
   * @var int
   */
  protected $indent;

  /**
   *
   * @var array holds the internationaliztion strings
   */
  protected $i18n;

  /**
   *
   * @var array of all available form element types
   */
  var $element_types;

  /**
   * a namespacing prefix for CSS classes and such
   */
  var $prefix = 'form-element';

  /**
   * 
   * @var string name of the instantiating module
   */
  var $module;
  
  /**
   * @var string  URL element link property
   */
  var $link;
  
  /**
   * @var int holds the record ID
   */
  public $record_id;

  /**
   * instantiates a xnau_FormElement object
   * 
   *
   * @param array $parameters carries the parameters to build a form element
   *                    type         string sets the type of element to print
   *                    value        string the current value of the element
   *                    name         string the name attribute of the element
   *                    options      mixed  an optional array of values for checkboxes, selects, etc. Can also
   *                                        be serialized array. A special element in this array has the key 
   *                                        "null_select" which if bool false prevents the selected null case of 
   *                                        dropdown elements from being added. If it has another value, the null 
   *                                        case (which has a blank label) will hold this value and be selected 
   *                                        if no value property is provided to the instance
   *                    attributes   array  an optional array of name=>value set of HTML attributes to include
   *                                        (can include a class attribute)
   *                    class        string a class name for the element; more than one class name must be
   *                                        space-separated string
   *                    indent       int    starting indent value
   *                    size         int    the size of the field (text type fields only)
   *                    container_id string CSS id for the element containter (if any)
   *
   * @return NULL
   */
  public function __construct( $parameters )
  {
    $this->_set_types();

    $defaults = array(
        'options' => NULL,
        'attributes' => array(),
        'class' => '',
        'indent' => 1,
        'size' => false,
        'container_id' => false,
        'group' => false,
        'value' => '',
        'link' => '',
        'record_id' => 0,
    );
    $params = wp_parse_args( $parameters, $defaults );

    $this->type = $params['type'];
    $this->form_element = $params['type'];
    $this->value = $params['value'];
    $this->name = $params['name'];
    $this->size = $params['size'];
    $this->container_id = $params['container_id'];
    $this->group = $params['group'];
    $this->module = isset( $params['module'] ) ? $params['module'] : '';
    $this->attributes = $params['attributes'];
    $this->link = $params['link'];
    $this->record_id = $params['record_id'];

    if ( NULL !== $params['options'] || !empty( $params['options'] ) ) {

      // this value is stored as a serialized array, but the class could be called with an array for this value
      $this->options = maybe_unserialize( $params['options'] );
    }

    $this->i18n = array(
        'other' => _x( 'other', 'indicates a write-in choice', 'participants-database' ),
        'linktext' => _x( 'Link Text', 'indicates the text to be clicked to go to another web page', 'participants-database' )
    );
    /*
     * classes can come in in the classes parameter or as part of the attributes array. 
     * We consolidate them into the classes property here.
     */
    $this->classes = empty( $params['class'] ) ? array() : explode( ' ', $params['class'] );
    if ( isset( $this->attributes['class'] ) ) {
      $this->classes = array_merge( $this->classes, explode( ' ', $this->attributes['class'] ) );
      unset( $this->attributes['class'] );
    }

    $this->indent = $params['indent'];

    // clear the output array
    $this->output = array();


    $this->build_element();
  }

  /**
   * give the child class a chance to insert it's modifications to the build method
   */
  abstract function build_element();

  /**
   * builds the form element by calling it's method
   * 
   * @return null
   */
  protected function call_element_method()
  {

    switch ( $this->type ) :

      case 'date':
        $this->_date_field();
        break;

      case 'timestamp':
        $this->_timestamp_field();
        break;

      case 'text-area':
      case 'textarea':
        $this->_text_field();
        break;

      case 'rich-text':
        $this->_rich_text_field();
        break;

      case 'checkbox':
        $this->_checkbox();
        break;

      case 'radio':
        $this->_radio();
        break;

      case 'dropdown':
        $this->_dropdown();
        break;

      case 'dropdown-other':
        $this->_dropdown_other();
        break;

      case 'multi-dropdown':
        $this->_dropdown_multi();
        break;

      case 'multi-checkbox':
        $this->_multi_checkbox();
        break;

      case 'text':
      case 'text-line':
        $this->_text_line();
        break;

      case 'password':
        $this->_password();
        break;

      case 'select-other':
        $this->_select_other();
        break;

      case 'multi-select-other':
        $this->_select_other_multi();
        break;

      case 'link':
        $this->_link_field();
        break;

      case 'drag-sort':
        $this->_drag_sort();
        break;

      case 'submit':
        $this->_submit_button();
        break;

      case 'selectbox':
        $this->_selectbox();
        break;

      case 'hidden':
        $this->_hidden();
        break;

      case 'image-upload':
        $this->_upload( 'image' );
        break;

      case 'file':
      case 'file-upload':
        $this->_upload( 'file' );
        break;

      case 'captcha':
        $this->_captcha();
        break;

      case 'numeric':
      case 'decimal':
      case 'currency':
        $this->_numeric();
        break;

      default:

    endswitch;
  }

  /**
   * builds the HTML string for display
   *
   * @static
   */
  static function _HTML( $parameters )
  {
    
  }

  /*   * ********************
   * PUBLIC METHODS
   */

  /**
   * prints a form element
   *
   * this func is calls the child class so any legacy implementations using the 
   * xnau_FormElement class alone can still work
   *
   * @param array $parameters (same as __construct() )
   * @static
   */
  public static function print_element( $parameters )
  {
    PDb_FormElement::print_element( $parameters );
  }

  /**
   * returns a form element
   *
   * @param array $parameters (same as __construct() )
   * @static
   */
  public static function get_element( $parameters )
  {
    PDb_FormElement::get_element( $parameters );
  }

  /**
   * outputs a set of hidden inputs
   *
   * @param array $fields name=>value pairs for each hidden input tag
   */
  public static function print_hidden_fields( $fields, $print = true )
  {

    PDb_FormElement::print_hidden_fields( $fields, $print );
  }

  /**
   * returns an element value formatted for display or storage
   * 
   * @param object $field a Field_Item object
   * @param bool   $html  if true, returns the value wrapped in HTML, false returns 
   *                      the formatted value alone
   * @return string the object's current value, formatted
   */
  public static function get_field_value_display( $field, $html = true )
  {
    switch ( $field->form_element ) :

      case 'image-upload' :

        $image = new PDb_Image( array(
            'filename' => $field->value,
            'link' => (isset( $field->link ) ? $field->link : ''),
            'mode' => 'both',
            'module' => $field->module,
        ) );

        if ( $html and ( !is_admin() or ( defined( 'DOING_AJAX' ) and DOING_AJAX)) ) {
          if ( isset( $field->module ) and in_array( $field->module, array('single', 'list') ) ) {
            $image->display_mode = 'image';
          } elseif ( isset( $field->module ) and $field->module == 'signup' ) {
            $image->display_mode = $image->image_defined ? 'both' : 'none';
            $image->link = false;
          } elseif ( isset( $field->module ) and $field->module == 'record' ) {
            $image->display_mode = 'filename';
          }
          $image->set_image_wrap();
          $return = $image->get_image_html();
        } elseif ( $image->file_exists ) {
          $return = $image->get_image_file();
        } else {
          $return = $field->value;
        }

        break;

      case 'file-upload' :

        if ( $html and ! empty( $field->value ) ) {

          if ( $field->module == 'signup' ) {
            $field->link = false;
            $return = $field->value;
          } else {
            $upload_dir = wp_upload_dir();
            $field->link = $upload_dir['url'] . $field->value;
            $return = self::make_link( $field );
          }
          break;
        } else {

          $return = $field->value;
          break;
        }

      case 'date' :
      case 'timestamp' :

        $return = '';
        if ( self::is_empty( $field->value ) === false ) {

          $date = strtotime( $field->value );

          $format = get_option( 'date_format', 'r' );
          $return = date_i18n( $format, $date );
        }
        break;

      case 'multi-checkbox' :
      case 'multi-select-other' :
      case 'multi-dropdown':

        $multivalues = maybe_unserialize( $field->value );
        if ( is_array( $multivalues ) and empty( $multivalues['other'] ) )
          unset( $multivalues['other'] );

        $return = implode( ', ', (array) $multivalues );
        break;

      case 'link' :

        /*
         * value is indexed array: array( $url, $linktext )
         */

        if ( !$linkdata = unserialize_array( $field->value ) ) {

          $return = '';
          break;
        }

        if ( empty( $linkdata[1] ) )
          $linkdata[1] = str_replace( 'http://', '', $linkdata[0] );

        if ( $html )
          $return = vsprintf( ( empty( $linkdata[0] ) ? '%1$s%2$s' : '<a href="%1$s">%2$s</a>' ), $linkdata );
        else
          $return = $linkdata[0];
        break;

      case 'text-line' :

        if ( $html ) {

          $return = self::make_link( $field );
          break;
        } else {

          $return = $field->value;
          break;
        }

      case 'text-area':
      case 'textarea':

        $return = $html ? sprintf( '<span class="' . self::class_attribute( 'textarea' ) . '">%s</span>', $field->value ) : $field->value;
        break;
      case 'rich-text':

        $return = $html ? '<span class="' . self::class_attribute( 'textarea richtext' ) . '">' . $field->value . '</span>' : $field->value;
        break;
      
      case 'decimal':
        
        $return = floatval( $field->value );
        break;
      
      default :

        $return = $field->value;

    endswitch;

    return $return;
  }

  /*   * *********************** 
   * ELEMENT CONSTRUCTORS
   */

  /**
   * builds a input text element
   */
  protected function _text_line()
  {

    if ( is_array( $this->value ) ) {
      $this->value = current( $this->value );
    }

    $this->add_options_to_attributes();

    $this->value = htmlspecialchars( $this->value, ENT_QUOTES, 'UTF-8', false );

    $this->_addline( $this->_input_tag() );
  }

  /**
   * builds a numeric input element
   */
  protected function _numeric()
  {

    if ( is_array( $this->value ) ) {
      $this->value = current( $this->value );
    }

    $this->add_options_to_attributes();

    $this->_addline( $this->_input_tag( 'number' ) );
  }

  /**
   * builds a date field
   */
  protected function _date_field()
  {

    $this->add_class( 'date_field' );

    if ( !empty( $this->value ) ) {
      $this->value = $this->format_date( $this->value, false );
    }

    $this->_addline( $this->_input_tag() );
  }

  /**
   * builds a timestamp field
   */
  protected function _timestamp_field()
  {

    $this->add_class( 'timestamp_field' );

    // test for a timestamp
    if ( is_int( $this->value ) or ( (string) (int) $this->value === $this->value) ) {
      $this->value = $this->format_date( $this->value, true );
    } elseif ( strlen( $this->value ) > 0 ) {
      $this->value = $this->format_date( strtotime( $this->value ), true );
    }

    if ( Participants_Db::apply_filters( 'edit_record_timestamps', false ) === false ) {
      $this->attributes['disabled'] = true;
    } else {
      unset( $this->attributes['readonly'] );
    }
    
    $this->_addline( $this->_input_tag() );
  }

  /**
   * builds a text-field (textarea) element
   */
  protected function _text_field()
  {

    $value = !empty( $this->value ) ? $this->value : '';

    $this->_addline( '<textarea name="' . $this->name . '" rows="' . $this->textarea_dims['rows'] . '" cols="' . $this->textarea_dims['cols'] . '" ' . $this->_attributes() . $this->_class() . ' >' . $value . '</textarea>', empty( $this->value ) ? 0 : -1  );
  }

  /**
   * builds a rich-text editor (textarea) element
   */
  protected function _rich_text_field()
  {
    $value = isset( $this->value ) ? $this->value : '';

    wp_editor(
            htmlspecialchars_decode( $value ), 
            Participants_Db::rich_text_editor_id( $this->name ), 
            array(
              'media_buttons' => false,
              'textarea_name' => $this->name,
            )
    );
  }

  /**
   * builds a password text element
   */
  protected function _password()
  {
    $this->value = '';

    $this->_addline( $this->_input_tag( 'password' ) );
  }

  /**
   * builds a checkbox element
   *
   * places a hidden field to supply the value when unchecked
   *
   * if there is no options array supplied, it is assumed to be a "select box",
   * which is a checkbox with no unchecked value, otherwise, there is a hidden
   * input added to supply a value to the field when the box is unchecked. The
   * first value of the array is the checked value, the second is the unchecked
   * value. If a key is provided, the key for the first options array element
   * will be the label for the checkbox. If no key is provided, no label will be
   * printed
   */
  protected function _checkbox()
  {

    // if no options are defined, then it's a selectbox
    if ( false === $this->options or ! is_array( $this->options ) ) {
      $this->_selectbox();
      return NULL;
    } else {
      $title = $this->is_assoc( $this->options ) ? key( $this->options ) : false;
      $checked_value = current( $this->options );
      $unchecked_value = next( $this->options );
      if ( $unchecked_value === false )
        $unchecked_value = '';
    }

    $id = $this->element_id();
    $this->attributes['id'] = $id . '-default';
    $this->_addline( $this->_input_tag( 'hidden', $unchecked_value ) );
    $this->attributes['id'] = $id;
    if ( false !== $title ) {
      $this->_addline( '<label for="' . $this->attributes['id'] . '">' );
    }
    $this->_addline( $this->_input_tag( 'checkbox', $checked_value, 'checked' ), 1 );

    if ( false !== $title ) {
      $this->_addline( Participants_Db::apply_filters( 'translate_string', $title ), 1 );
      $this->_addline( '</label>', -1 );
    }
  }

  /**
   * builds a radio button element
   */
  protected function _radio()
  {
    $this->_add_radio_series();
  }

  /**
   * builds a dropdown or dropdown-other element
   */
  protected function _dropdown( $other = false )
  {
    if ( isset( $this->attributes['other'] ) ) {
      $otherlabel = $this->attributes['other'];
      unset( $this->attributes['other'] );
    } else {
      $otherlabel = $this->i18n['other'];
    }

    // set the ID for the select element
    $id = $this->element_id();
    
    if ( !isset( $this->attributes['readonly'] ) ) {

      // make a unique prefix for the js function
      $js_prefix = $this->_prep_js_string( $this->name );

      // set the ID for the select element
      $id = $this->element_id();
      $this->attributes['id'] = (empty( $id ) ? $js_prefix . '_select' : $id);
      if ( isset( $this->attributes['multiple'] ) && $this->attributes['multiple'] === true ) {
        $this->group = true;
        $this->name = $this->name . '[]';
        $this->value = self::field_value_array( $this->value );
      }
      if ( $other ) {
        $this->_addline( '<div class="dropdown-other-control-group" >' );
        $this->add_class( 'otherselect' );
        //$this->_addline('<select id="' . $js_prefix . '_otherselect" onChange="' . $js_prefix . 'SelectOther()" name="' . $this->name . '" ' . $this->_attributes() . ' >');
      }
      
      $this->_addline( '<select name="' . $this->name . '" ' . $this->_attributes() . $this->_class() . ' >' );

      // restore the ID attribute
      $this->attributes['id'] = $id;

      $this->indent++;

      /*
       * include the "nothing selected" state
       */
      $this->_set_null_select();

      $this->_add_option_series( $other ? $otherlabel : false );

      $this->_addline( '</select>', -1 );

      if ( $other ) {
        
        // build the text input element
        $this->attributes['id'] .= '_other';
        $is_other = $this->_set_selected( $this->options, $this->value, 'selected', false ) !== '';
        
        $this->_addline( '<input type="text" name="' . $this->name . '" value="' . ( $is_other ? htmlspecialchars( $this->value, ENT_QUOTES, 'UTF-8', false ) : '' ) . '" ' . $this->_attributes( 'no validate' ) . $this->_class( 'otherfield' ) . ' >' );
        $this->_addline( '</div>' );
      }
    } else {
      
      // readonly display
      $this->attributes['id'] = $this->element_id() . '_readonly';
      $options = $this->_make_assoc( $this->options );
      
      $this->_addline( '<input type="text" name="' . $this->name . '" value="' . array_search($this->value, $options) . '" ' . $this->_attributes('no validate') . $this->_class( 'pdb-readonly' ) . ' >' );
    }
  }

  /**
   * builds a dropdown-other element
   *
   * @return string
   */
  protected function _dropdown_other()
  {

    $this->_dropdown( true );
  }

  /**
   * builds a dropdown-multiselect element
   *
   * @return string
   */
  protected function _dropdown_multi()
  {

    $this->attributes['multiple'] = true;
    $this->_dropdown();
  }

  /**
   * builds a multi-checkbox
   *
   * a set of checkboxes enclosed in a div tag
   */
  protected function _multi_checkbox()
  {

    $this->value = self::field_value_array( $this->value );

//    if (!isset($this->attributes['readonly'])) {

    $this->_addline( '<div class="multicheckbox"' . ( $this->container_id ? ' id="' . $this->container_id . '"' : '' ) . '>' );
    $this->indent++;

    $this->_add_checkbox_series();

    $this->_addline( '</div>', -1 );
//    } else {
//      $this->_readonly_multi();
//    }
  }

  /**
   * builds a select/other form element
   *
   * a set of checkboxes or radio buttons with an optional text input element activated by selecting "other"
   *
   * @param string $type can be either 'radio' or 'checkbox' (for a multi-select element)
   */
  protected function _select_other( $type = 'radio' )
  {

    if ( $type == 'radio' ) {
      $this->value = is_array( $this->value ) ? current( $this->value ) : $this->value;
    } else {
      $this->value = self::field_value_array( $this->value );
      if ( !isset( $this->value['other'] ) )
        $this->value['other'] = '';
    }

    /*
     * determine the label for the other field: start with the default value, then 
     * in the field definition, the finally the string if set in the template via 
     * the attributes array
     */
    $otherlabel = $this->i18n['other'];
    if ( $i = array_search( 'other', $this->options ) ) {
      $otherlabel = array_search( 'other', $this->options );
      unset( $this->options[$otherlabel] );
    }
    if ( isset( $this->attributes['other'] ) ) {
      $otherlabel = $this->attributes['other'];
      unset( $this->attributes['other'] );
    }

    // make a unique prefix for the function
    $js_prefix = $this->_prep_js_string( $this->name )/* .'_' */;

    // put it in a conatiner
    $this->_addline( '<div class="selectother ' . $type . '-other-control-group"' . ( $this->container_id ? ' id="' . $this->container_id . '"' : '' ) . ' >' );
    $this->indent++;

    $type == 'checkbox' ? $this->_add_checkbox_series( $otherlabel ) : $this->_add_radio_series( $otherlabel );

    $controltag = array_pop( $this->output ); // save the <span.othercontrol> close tag
    $closetag = array_pop( $this->output ); // save the <span.checkbox-group> close tag

    // add the text input element
    $value = $type == 'checkbox' ? $this->value['other'] : (!in_array( $this->value, $this->options ) ? $this->value : '' );
    $name = $type == 'checkbox' ? str_replace( '[]', '', $this->name ) . '[other]' : '';
    $id = $this->element_id();
    $this->attributes['id'] = $id . '_other';
    $this->_addline( '<input type="text" name="' . $name . '" value="' . htmlspecialchars( $value, ENT_QUOTES, 'UTF-8', false ) . '" ' . $this->_attributes('no validate') . $this->_class( 'otherfield' ) . ' />' );
    $this->attributes['id'] = $id;
    array_push( $this->output, $closetag, $controltag ); // replace the span close tags, enclosing the input element in it
    // close the container
    $this->_addline( '</div><!-- .' . $type . '-other-control-group -->', -1 ); //  control-group div
  }

  /**
   * builds a multi-select/other form element
   */
  protected function _select_other_multi()
  {
//    if (!isset($this->attributes['readonly'])) {
    $this->_select_other( 'checkbox' );
//    } else {
//      $this->_readonly_multi();
//    }
  }

  /**
   * builds a link form element
   *
   * stores an array: first element is the URL the optional second the link text
   */
  protected function _link_field()
  {
    // this element's value is stored as an array
    $this->group = true;

    $link_placeholder = isset( $this->attributes['url_placeholder'] ) ? $this->attributes['url_placeholder'] : '(URL)';
    $linktext_placeholder = isset( $this->attributes['placeholder'] ) ? $this->attributes['placeholder'] : $this->i18n['linktext'];
    
    // set the correct format for an empty value
    if ( $this->value === array() || is_null( $this->value ) || ( is_string( $this->value ) && strlen( $this->value ) === 0 ) ) {
      $this->value = array('');
    }
    
    $parts = maybe_unserialize( $this->value );
    
    if ( ! is_array( $parts ) ) {
      if ( filter_var( $parts, FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE ) ) {
        $this->value = $parts;
        $parts = array( $parts, $linktext_placeholder );
      } elseif ( filter_var( $this->link, FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE ) ) {
        $parts = array( $this->link, $parts );
      } else {
        $parts = array('', $this->value );
      }
    } elseif ( !empty( $this->link ) ) {
      $parts[0] = $this->link;
    }
    
    // if the value contains only a URL, the linktext and URL are made the same
    // if the value is not a URL, only the linked text is used
    
    if ( count( $parts ) < 2 ) {
      $parts[1] = ''; // when showing an edit form, leave the click text blank
      if ( !filter_var( $parts[0], FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE ) )
        $parts[0] = '';
    }
    
    list( $url, $title ) = $parts;

    $this->_addline( '<div class="link-element">' );

    $title = empty( $title ) ? '' : $title;

    $this->attributes['placeholder'] = $link_placeholder;

    $id = $this->element_id();
    $this->attributes['id'] = $id . '-url';
    $this->_addline( $this->_input_tag( 'url', $url, false ) );

    $this->attributes['placeholder'] = $linktext_placeholder;

    $this->attributes['id'] = $id . '-text';
    $this->_addline( $this->_input_tag( 'text', htmlspecialchars( $title, ENT_QUOTES, 'UTF-8', false ), false ) . '</div>' );
    $this->attributes['id'] = $id;
  }

  /**
   * produces the output for a read-only multi-select element
   * 
   */
  protected function _readonly_multi()
  {

    $display = array();
    $this->group = true;

    $this->_addline( '<div class="readonly-value-group">' );

    foreach ( self::field_value_array( $this->value ) as $value ) {

      if ( $value !== '' ) {

        $display[] = $value;
        $this->_addline( $this->_input_tag( 'hidden', $value ) );
      }
    }
    $this->_addline( '<span class="pdb-readonly">' . implode( ', ', $display ) . '</span></div>' );
  }

  /**
   * builds a drag-sort element
   *
   * requires js on page to function; this just supplies a suitable handle
   *
   */
  protected function _drag_sort()
  {

    $name = preg_replace( '#(\[.*\])#', '', $this->name );

    $this->_addline( '<a id="' . $name . '" class="dragger" href="#" ><span class="dashicons dashicons-sort"></span></a>' ); // &uarr;&darr;
  }

  /**
   * builds a submit button
   */
  protected function _submit_button()
  {

    $this->_addline( $this->_input_tag( 'submit' ) );
  }

  /**
   * builds a selector box
   * special checkbox with no unselected value
   */
  protected function _selectbox()
  {

    $this->_addline( $this->_input_tag( 'hidden', '' ) );

    $this->_addline( $this->_input_tag( 'checkbox', $this->value, false ) );
  }

  /**
   * build a hidden field
   */
  protected function _hidden()
  {
    $this->_addline( $this->_input_tag( 'hidden' ) );
  }

  /**
   * builds a file upload element
   * 
   * @param string $type the upload type: file or image
   */
  protected function _upload( $type )
  {

    $this->_addline( '<div class="' . $this->prefix . 'upload">' );
    // if a file is already defined, show it
    if ( !empty( $this->value ) ) {

      $this->_addline( self::get_field_value_display( $this ) );
    }

    // add the MAX_FILE_SIZE field
    // this is really just for guidance, not a valid safeguard; this must be checked on submission
    if ( isset( $this->options['max_file_size'] ) )
      $max_size = $this->options['max_file_size'];
    else
      $max_size = ( ini_get( 'post_max_size' ) / 2 ) * 1048576; // half it to give a cushion

    $this->_addline( $this->print_hidden_fields( array('MAX_FILE_SIZE' => $max_size, $this->name => $this->value), false ) );

    if ( !isset( $this->attributes['readonly'] ) ) {
      $this->_addline( $this->_input_tag( 'file' ) );

      // add the delete checkbox if there is a file defined
      if ( !empty( $this->value ) ) {
        $this->_addline( '<span class="file-delete" ><label><input type="checkbox" value="delete" name="' . $this->name . '-deletefile">' . __( 'delete', 'participants-database' ) . '</label></span>' );
      }
    }

    $this->_addline( '</div>' );
  }

  /**
   * builds a captcha element
   * 
   */
  protected function _captcha()
  {

    $this->_addline( $this->_input_tag( 'text' ) );
  }

  /*   * ********************** 
   * SUB-ELEMENTS
   */

  /**
   * builds an input tag
   *
   * @param string $type   the type of input tag to return, defaults to 'text'
   * @param string $value  the value of the tag; if not given, uses object value
   *                       property
   * @param string $select the selected attribute string for the element. If
   *                       given, performs a match test and sets the flag if met
   * @param bool   $group  if set, adds brackets to name for group elements
   * @return string
   *
   */
  protected function _input_tag( $type = 'text', $value = false, $select = false )
  {
    if ( $value === false ) {
      $value = $this->value;
    }
    
    $size = $this->size ? ' size="' . $this->size . '" ' : '';

    if ( $type === 'text' && isset( $this->attributes['type'] ) ) {
      $this->attributes = array_merge( array('type' => $type), (array) $this->attributes );
    } else {
      $this->attributes['type'] = $type;
    }

    if ( in_array( $type, array('checkbox', 'radio', 'multi-checkbox', 'select-other') ) && isset( $this->attributes['readonly'] ) ) {
      $this->attributes['disabled'] = 'disabled';
      unset( $this->attributes['readonly'] );
    }

    $value_att = in_array( $type, array('file', 'image') ) ? '' : 'value="' . esc_attr( $value ) . '"';
    
    $html = '<input name="' . esc_attr( $this->name . ( $this->group ? '[]' : '' ) ) . '"' . $size . ( false !== $select ? $this->_set_selected( $value, $this->value, $select ) : '' ) . ' ' . $this->_attributes($type) . $this->_class() . '  ' . $value_att . ' />';
    
    // unset the type attribute so it doesn't carry over to the next element
    unset( $this->attributes['type'] );
    return $html;
  }

  /**
   * builds a checkbox or radio input series
   *
   * @param string $type sets the type of input series, defaults to checkbox
   * @param string|bool if string, add an "other" option with this label
   */
  protected function _add_input_series( $type = 'checkbox', $otherlabel = false )
  {

    if ( empty( $this->options ) )
      return;

    // checkboxes are grouped, radios are not
    $this->group = $type === 'checkbox';
    
    // checkboxes are given a null select so an "unchecked" state is possible
    $null_select = (isset( $this->options[self::null_select_key()] )) ? $this->options[self::null_select_key()] : ($type == 'checkbox' ? true : false);

    if ( $null_select !== false && $null_select !== 'false' ) {
      $id = $this->element_id();
      $this->attributes['id'] = $id . '-default';
      $this->_addline( $this->_input_tag( 'hidden', (is_string( $null_select ) ? $null_select : '' ), false ), 1 );
      $this->attributes['id'] = $id;
    }
    unset( $this->options[self::null_select_key()] );

    $this->_addline( '<div class="' . $type . '-group" >' );

    $optgroup = false;

    foreach ( $this->_make_assoc( $this->options ) as $option_key => $option_value ) {

      if ( ($option_value === false or $option_value === 'false' or $option_value === 'optgroup') and ! empty( $option_key ) ) {
        if ( $optgroup ) {
          $this->_addline( '</fieldset>' );
        }
        $id = $this->element_id( $this->legal_name( $this->name . '-' . ($option_value === '' ? '_' : trim( strtolower( $option_key ) )) ) );
        $this->_addline( '<fieldset class="' . $type . '-subgroup ' . $this->name . '-subgroup" id="' . $id . '"><legend>' . $option_key . '</legend>' );
        $optgroup = true;
      } else {
        $id = $this->element_id();
        $this->attributes['id'] = $this->element_id( $this->legal_name( $this->prefix . $this->name . '-' . ( $option_value === '' ? '_' : trim( strtolower( $option_value ) ) ) ) );
        $this->_addline( '<label ' . $this->_class() . ' for="' . $this->attributes['id'] . '">' );
        $this->_addline( $this->_input_tag( $type, $option_value, 'checked' ), 1 );
        $this->_addline( $option_key . '</label>' );
        $this->attributes['id'] = $id;
      }
    }
    if ( $optgroup ) {
      $this->_addline( '</fieldset>' );
      $optgroup = false;
    }
    if ( $otherlabel ) {

      $value = $type == 'checkbox' ? (isset( $this->value['other'] ) ? $this->value['other'] : '') : $this->value;
      $this->_addline( '<div class="othercontrol">' );
      $id = $this->element_id();
      $this->attributes['id'] = $id . '_otherselect';
      $this->_addline( '<label ' . $this->_class() . ' for="' . $this->attributes['id'] . '">' );
      $this->_addline( sprintf( '<input type="%s" name="%s"  value="%s" %s %s />', $type, $type === 'radio' ? $this->name : 'pdb-otherselector', $otherlabel, $this->_set_selected( $this->options, $value, 'checked', $value === '' ), $this->_attributes() . $this->_class( 'otherselect' )
              ), 1 );
      $this->attributes['id'] = $id;
      //$this->_addline('<input type="' . $type . '" id="' . $this->name . '_otherselect" name="' . ($type == 'checkbox' ? 'temp' : $this->name) . '"  value="' . $otherlabel . '" ' . $this->_set_selected($this->options, ( $type == 'checkbox' ? $this->value['other'] : $this->value), 'checked', false) . ' ' . $this->_attributes() . ' />', 1);
      $this->_addline( $otherlabel . ':' );
      $this->_addline( '</label>', -1 );
      $this->_addline( '</div>', -1 );
    }

    $this->_addline( '</div>' );
  }

  /**
   * adds a series of radio buttons
   * 
   * @param string|bool if string, add an "other" option with this label
   */
  protected function _add_checkbox_series( $otherlabel = false )
  {

    $this->_add_input_series( 'checkbox', $otherlabel );
  }

  /**
   * adds a series of radio buttons
   * 
   * @param string|bool if string, add an "other" option with this label
   */
  protected function _add_radio_series( $otherlabel = false )
  {
    $this->_add_input_series( 'radio', $otherlabel );
  }

  /**
   * builds an option series
   * 
   * if an element in the options array has a value of bool false, it will open an 
   * optgroup using the key as the group 
   * 
   * @var string|bool label of the "other" option if any
   */
  protected function _add_option_series( $otherlabel = false )
  {
    if ( empty( $this->options ) )
      return;

    foreach ( $this->_make_assoc( $this->options ) as $title => $value ) {

      $title = Participants_Db::apply_filters( 'translate_string', $title );
      
      if ( $value == 'false' && $title === self::null_select_key() ) {
        continue 1;
      } elseif ( $value === 'optgroup' && strlen( $title ) > 0 ) {
        $this->_add_options_divider( $title );
      } elseif ( $value === 'other' ) {
        $otherlabel = $title;
      } elseif ( strlen( $value ) > 0 ) {
        $this->_addline( '<option value="' . esc_attr( $value ) . '" ' . $this->_set_selected( $value, $this->value, 'selected' ) . ' >' . strip_tags( $title ) . '</option>', -1 );
      }
    }
    // add the "other" option
    if ( $otherlabel !== false )
      $this->_addline( '<option ' . ( $this->value !== '' ? $this->_set_selected( $this->options, $this->value, 'selected', false ) : '' ) . ' value="other" >' . strip_tags( $otherlabel ) . '</option>' );

    if ( $this->inside ) {
      $this->_addline( '</optgroup>' );
      $this->inside = false;
    }
  }

  /*   * ****************  
   * OUTPUT FUNCTIONS
   */

  /**
   * builds an output string
   */
  protected function _output()
  {

    return implode( self::BR, (array) $this->output ) . self::BR;
  }

  /**
   * add a line to the output property
   *
   * places the proper number of tabs at the beginning of each line, then adds
   * the line to the output array
   *
   * @param string  $line          the line to be added
   * @param int     $tab_increment change to the current tab level ( +/- 1 ); false
   *                               for no indent
   */
  protected function _addline( $line, $tab_increment = 0 )
  {

    $indent = '';

    if ( false !== $tab_increment ) {

      if ( $tab_increment > 0 )
        $this->indent++;
      elseif ( $tab_increment < 0 )
        $this->indent--;
    }

    $this->output[] = $indent . $line;
  }

  /*   * ************************* 
   * UTILITY FUNCTIONS
   */
  
  /**
   * provides an array of values from a stored field value
   * 
   * @param string $value the raw value from the db
   * @return array array of values
   */
  public static function field_value_array( $value )
  {
    return PDb_Field_Item::field_value_array($value);
  }

  /**
   * outputs a link (HTML anchor tag) in specified format if enabled by "make_links"
   * option
   * 
   * this func validates the link as being either an email addres or URI, then
   * (if enabled) builds the HTML and returns it
   * 
   * @param object $field the field object
   * @param string $linktext the clickable text (optional)
   * @param string $template the format of the link (optional)
   * @param array  $get an array of name=>value pairs to include in the get string
   *
   * @return string HTML or HTML-escaped string (if it's not a link)
   */
  public static function make_link( $field, $template = false, $get = false )
  {


    // clean up the provided link string
    $URI = str_replace( 'mailto:', '', trim( strip_tags( $field->value ) ) );
    $linktext = empty( $field->value ) ? $field->default : $field->value;

    if ( isset( $field->link ) and ! empty( $field->link ) ) {
      // if the field is a single record link or other kind of defined link field
      $URI = $field->link;
    } elseif ( filter_var( $URI, FILTER_VALIDATE_URL ) ) {

      // convert the get array to a get string and add it to the URI
      if ( is_array( $get ) ) {

        $URI .= false !== strpos( $URI, '?' ) ? '&' : '?';

        $URI .= http_build_query( $get );
      }
    } elseif ( filter_var( $URI, FILTER_VALIDATE_EMAIL ) ) {

      // in admin, emails are plaintext
      if ( is_admin() )
        return esc_html( $field->value );
      $linktext = $URI;
      $URI = 'mailto:' . $URI;
    } else {
      return $field->value; // if it is neither URL nor email address nor defined link
    }

    // default template for links
    $linktemplate = $template === false ? '<a href="%1$s" >%2$s</a>' : $template;

    $linktext = empty( $linktext ) ? str_replace( array('http://', 'https://'), '', $URI ) : $linktext;

    //construct the link
    return sprintf( $linktemplate, $URI, esc_html( $linktext ) );
  }

  /**
   * adds a class name to the class property
   */
  public function add_class( $classname )
  {

    $this->classes[] = $classname;
  }

  /**
   * builds a string of attributes for inclusion in an HTML element
   *
   * @param array $attributes_array an attributes array to use; 
   *                                default: $this->attributes
   * @return string
   */
  protected function _attributes( $attributes_array = false )
  {

    $attributes_array = $attributes_array ? $attributes_array : $this->attributes;

    if ( empty( $attributes_array ) )
      return '';

    return self::html_attributes($attributes_array);
  }
  
  /**
   * builds an html attributes string
   * 
   * @param array $attributes the attributes array
   * @param array $allowed array of allowed attributes (optional)
   * 
   * @return string the HTML attribute string
   */
  public static function html_attributes( $attributes, $allowed = false )
  {
    $output = array();

    foreach ( (array) $attributes as $name => $value ) {
      
      if ( ( $allowed && in_array( $name, $allowed ) ) || !is_array( $allowed ) ) {

        if ( $value === false ) {
          continue;
        } elseif ( $value === true ) {
          $output[] = sprintf( '%1$s="%1$s"', esc_attr( $name ) );
        } elseif ( preg_match('/^\d+$/', $name) || $value === $name ) {
          $output[] = esc_attr( $value );
        } elseif ( self::is_translatable_att($name) ) {
          $output[] = sprintf( '%s="%s"', esc_attr( $name ), esc_attr( Participants_Db::apply_filters( 'translate_string', $value ) ) );
        } else {
          $output[] = sprintf( '%s="%s"', esc_attr( $name ), esc_attr( $value ) );
        }
      
      }
      
    }

    return implode( ' ', $output );
  }
  
  /**
   * provides a list of attributes that should be passed through the translation filter
   * 
   * @param string $name of the attribute
   * @return bool true if the attribute value should be passed through the translation filter
   */
  protected static function is_translatable_att( $name )
  {
    $translatable = Participants_Db::apply_filters('translatable_html_attributes', array(
        'placeholder',
        'title',
    ) );
    
    return in_array( $name, $translatable );
  }

  /**
   * merges the options array into the attributes
   * 
   * this is used on elements that need arbitrary attributes added
   */
  protected function add_options_to_attributes()
  {
    if ( is_array( $this->options ) ) {
      $this->attributes += $this->options;
    }
  }

  /**
   * builds a class attribute string
   * 
   * @param string $add_class any additional classes to add
   * 
   * @return string an html class attribute string
   */
  protected function _class( $add_class = false )
  {
    return self::class_attribute( $add_class, $this->classes );
  }

  /**
   * supplies a class attribute string
   * 
   * @param string $add_class any additional classes to add
   * 
   * @return string an html class attribute string
   */
  public static function class_attribute( $add_class, $classes = array() )
  {
    if ( $add_class ) {
      $classes[] = $add_class;
    }
    $class_string = implode( ' ', $classes );
    return empty( $class_string ) ? '' : ' class="' . esc_attr( $class_string ) . '"';
  }

  /**
   * returns a select state for a form field
   *
   * @param mixed  $element_value  the set values of the element that we compare against
   * @param string $selected_value      the selected value of the field
   * 
   * @param string $attribute      the keyword for the select state of the form element
   * @param bool   $state          inverts the logic of the array value match:
   *                               true = looking for a match;
   *                               false = looking for no match
   *
   * @return string selection state string for HTML element
   */
  protected function _set_selected( $element_value, $selected_value, $attribute = 'selected', $state = true )
  {
    if ( is_array( $selected_value ) ) {
      return $this->_set_multi_selected( $element_value, $selected_value, $attribute, $state );
    }

    $add_attribute = false;
    $selected_value = $this->_prep_comp_string( $selected_value );
    $element_value = $this->_prep_comp_array( $element_value );

    switch ( true ) {
      case ($element_value === true and $selected_value === true):
      case (is_array( $element_value ) and ( $state === in_array( $selected_value, $element_value ))):
      case ($element_value == $selected_value):
        $add_attribute = true;
        break;
      default:
    }

    return $add_attribute ? sprintf( ' %1$s="%1$s" ', $attribute ) : '';
  }

  /**
   * prepares a string for a comparison
   *
   * converts HTML entities to UTF-8 characters
   * 
   * if the argument is not a string, returns it unchanged
   * 
   * @param mixed $string
   * @return mixed converted string or unchanged input
   */
  protected function _prep_comp_string( $string )
  {

    return is_string( $string ) ? trim( html_entity_decode( $string, ENT_QUOTES, 'UTF-8' ) ) : $string;
  }

  /**
   * prepares an array for string comparison
   * 
   * @param array $array the array to prepare for comparison
   * @return array an indexed array of prepared strings
   */
  protected function _prep_comp_array( $array )
  {

    if ( !is_array( $array ) )
      return $this->_prep_comp_string( $array );

    $output = array();

    foreach ( $array as $item )
      $output[] = $this->_prep_comp_string( $item );

    return $output;
  }

  /**
   * sets up the "nothing selected" option element
   *      
   * include the null state if it is not overridden. This adds a blank option which 
   * will be selected if there is no value property set for the element. 
   * 
   * If $this->options['null_select'] has a string value, it will be used as the 
   * display value for the null option. 
   * If $this->options['null_select'] is blank, a blank unselected null option will 
   * be added. 
   * If $this->options['null_select'] is false no null state option will be added.
   * 
   * If the value is empty and no null select is defined, a blank null select option 
   * will be added so that the current state of the field can be represented.
   * 
   * TODO: if there is a defined default value, and the current vlaue of the field 
   * is not set, no null select should be added, the default value should be selected 
   * in the control
   * 
   * @return null
   */
  protected function _set_null_select()
  {
    /*
     * if the null_select option is a string, use it as the name of the null select 
     * option, unless it is the string 'false', then make it boolean false. If it is any 
     * other value or not set at all, make it boolean false
     */
    $null_select = true;
    $null_select_label = '';
    
    if ( isset( $this->options[self::null_select_key()] ) ) {
      
      if ( $this->options[self::null_select_key()] !== 'false' ) {
        $null_select = $this->options[self::null_select_key()];
        $null_select_label = strlen( $null_select ) > 0 ? Participants_Db::apply_filters('translate_string', $null_select ) : '&nbsp;';
      } else {
        $null_select = false;
      }
      // remove the null_select from the options array
      unset( $this->options[self::null_select_key()] );
    }

    if ( $null_select !== false ) {
      $selected = $this->value === '' ? $this->_set_selected( true, true, 'selected' ) : '';
      $this->_addline( '<option value="" ' . $selected . '  >' . esc_html( $null_select_label ) . '</option>' );
    }
  }
  
  /**
   * provides the null select key string
   * 
   * @return string
   */
  public static function null_select_key()
  {
    return 'null_select';//
  }

  /**
   * adds a divider element to an option series
   * 
   * @param string $title of the option divider
   * @return null
   */
  protected function _add_options_divider( $title )
  {
    $divider = '';
    if ( $this->inside ) {
      $divider = '</optgroup>' . self::BR;
      $this->inside = false;
    }
    $divider .= sprintf( '<optgroup label="%s">', esc_html( $title ) );
    $this->inside = true;
    $this->_addline( $divider );
  }

  /**
   * sets the select states for a multi-select element
   *
   * cycles through the available selects or checkboxes and sets the selected
   * attribute if there is a match to an element of the array of stored values
   * for the field
   *
   * @param string  $element_value   the value of one select of a multi-select
   * @param array   $selected_value_array the array of stored or inputted values
   * @param string  $attribute       the name of the "selected" attribute for the element
   * @param bool    $state           true to check for a match or false for a non-match
   * @return string                  the attribute string for the element
   */
  protected function _set_multi_selected( $element_value, $selected_value_array, $attribute = 'selected', $state = true )
  {

    $prepped_new_value_array = $this->_prep_comp_array( $selected_value_array );
    
    $prepped_string = $this->_prep_comp_string( $element_value );

    if ( $state === in_array( $prepped_string, $prepped_new_value_array ) )
      return sprintf( ' %1$s="%1$s" ', $attribute );
    else
      return '';
  }

  /**
   * tests the type of an array, returns true if associative
   * 
   * @param mixed $array
   * @return bool
   */
  public static function is_assoc( $array )
  {
    //$assoc = is_array( $array ) && count( array_filter( array_keys( $array ), function ($k) { return is_string($k); } ) ) === count( $array );
    $assoc = false;
    foreach ( $array as $k => $v ) {
      if ( is_string( $k ) && $k != $v ) {
        $assoc = true;
      }
    }
    return $assoc;
  }

  /**
   * makes a string OK to use in javascript as a variable or function name
   */
  protected function _prep_js_string( $string )
  {

    return str_replace( array('[', ']', '{', '}', '-', '.', '(', ')'), '', $string );
  }

  /**
   * makes an associative array out of an indexed array by copying the values into the keys
   *
   * given an associative array, it returns the array unaltered
   *
   * @param array the array to be processed
   * @return array an associative array
   */
  protected function _make_assoc( $array )
  {

    if ( $this->is_assoc( $array ) )
      return $array;

    return array_combine( array_values( $array ), $array );
  }

  /**
   * returns an internationalized date string from a UNIX timestamp
   * 
   * @param int $timestamp a UNIX timestamp
   * @param bool $time if true, adds the time of day to the format
   * @return string a formatted date or input string if invalid
   */
  public static function format_date( $timestamp, $time = false )
  {
    // if it's not a timestamp, we attempt to convert it to one
    if ( !preg_match( '#^[0-9-]+$#', $timestamp ) )
      $timestamp = strtotime( $timestamp );

    if ( preg_match( '#^[0-9-]+$#', $timestamp ) ) {
      $format = get_option( 'date_format' );

      if ( $time ) {
        $format .= ' ' . get_option( 'time_format' );
      }

      return date_i18n( $format, $timestamp );
    } else {
      // not a timestamp: return unchanged
      return $timestamp;
    }
  }

  /**
   * builds a legal CSS classname or ID
   * 
   * @param string $string
   * @return string the legalized name
   */
  public static function legal_name( $string )
  {
    // make sure it doens't start with a numeral
    if ( preg_match( '/^[0-9]/', $string ) )
      $string = '_' . $string;
    // eliminate any non-legal characters
    $string = preg_replace( '/[^_a-zA-Z0-9- ]/', '', $string );
    // replace spaces with a dash
    return strtolower( str_replace( array(' '), array('-'), $string ) );
  }

  /**
   * unambiguously test for all the flavors of emptiness
   * 
   * @var unknown $test the value to test
   * @return bool true if the value is the equivalent of empty, zero or undefined
   */
  public static function is_empty( $test )
  {
    // collapse an array
    if ( is_array( $test ) )
      $test = implode( '', $test );

    switch ( true ) {
      case $test === '0000-00-00 00:00:00':
      case strlen( trim( $test ) ) === 0:
      case $test === null:
        return true;
      case is_bool( $test ):
      case is_object( $test ):
      default:
        return false;
    }
  }

  /**
   * supplies an ID attribute
   * 
   * this is taken from the attributes property
   * 
   * @param string $baseid the base id
   * @return string the ID attribute or empty string
   */
  public function element_id( $baseid = false )
  {
    if ( ! $baseid ) {
      $baseid = isset( $this->attributes['id'] ) ? $this->attributes['id'] : '';
    }
    $id = ( ! empty( $baseid ) ? $baseid : $this->prefix . str_replace( '[]', '', $this->name ) );
    
    // attach the instance index if it is not present
    if ( preg_match( '/-' . Participants_Db::$instance_index . '$/', $id ) == 0 ) {
      $id = $id . '-' . Participants_Db::$instance_index;
    }
    return $id;
  }

  /**
   * tells if the named column is a numeric datatype
   * 
   * @oaram string  $column name of the column to check
   * @return bool true if the column is a numeric type
   */
  public static function is_numeric_datatype( $column )
  {
    global $wpdb;
    $sql = 'SHOW FIELDS FROM '. Participants_Db::$participants_table . ' WHERE Field = "%s"';
    $result = $wpdb->get_row( $wpdb->prepare( $sql, $column ) );
    $type = isset( $result->Type ) ? strtoupper( $result->Type ) : '';
    
    return preg_match('/(INT|DECIMAL|FLOAT|NUMERIC|DOUBLE)/', $type) === 1;
  }

  /**
   * returns a MYSQL datatype appropriate to the form element type
   * 
   * @param string $element name of the form element
   * @return string the name of the MySQL datatype
   */
  public static function get_datatype( $form_element )
  {
    switch ( $form_element ) {

      case 'timestamp':
        $datatype = 'timestamp';
        break;

      case 'date':
        $datatype = 'bigint';
        break;

      case 'numeric':
        $datatype = 'bigint';
        break;

      case 'decimal':
        $datatype = 'decimal(14,4)';
        break;

      case 'currency':
        $datatype = 'decimal(10,2)';
        break;

      case 'text-line':
        $datatype = 'tinytext';
        break;

      case 'checkbox':
      case 'radio':
      case 'multi-select':
      case 'multi-checkbox':
      case 'text-area':
      case 'rich-text':
      case 'dropdown':
      default :
        $datatype = 'text';
    }

    return $datatype;
  }

  /**
   * sets the array of available form element types
   * 
   * merges in an array in the config file, this allowing new types to be registered, 
   * also a language translation of type titles is possible by overwriting an existing 
   * entry
   */
  protected function _set_types()
  {
    $this->element_types = self::get_types();
  }

  /*
   * static function for assembling the types array
   */

  public static function get_types()
  {
    $types = array(
        'text-line' => 'Text-line',
        'text-area' => 'Text Area',
        'rich-text' => 'Rich Text',
        'checkbox' => 'Checkbox',
        'radio' => 'Radio Buttons',
        'dropdown' => 'Dropdown List',
        'date' => 'Date Field',
        'dropdown-other' => 'Dropdown/Other',
        'multi-checkbox' => 'Multiselect Checkbox',
        'multi-dropdown' => 'Multiselect Dropdown',
        'select-other' => 'Radio Buttons/Other',
        'multi-select-other' => 'Multiselect/Other',
        'link' => 'Link Field',
        'image-upload' => 'Image Upload Field',
        'file-upload' => 'File Upload Field',
        'hidden' => 'Hidden Field',
        'password' => 'Password Field',
        'captcha' => 'CAPTCHA',
        'timestamp' => 'Timestamp',
    );
    /*
     * this gives access to the list of form element types for alteration before
     * it is set
     */
    return $types;
  }

}
