ajax_chain_select.module

<?php

/**
 * @file
 * Custom form field for chained select controls.
 */

/**
 * Implements hook_menu().
 */
function ajax_chain_select_menu() {
  $items = array();

  $items['ajax_chain_select/callback'] = array(
    'page callback' => 'ajax_chain_select_element_callback',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );

  return $items;
}

/**
 * Implements hook_element_info().
 */
function ajax_chain_select_element_info() {
  $elements['ajax_chain_select'] = array(
    "#input" => TRUE,
    "#process" => array('ajax_chain_select_element_process'),
  );
  return $elements;
}

/**
 * Process callback for ac_select.
 */
function ajax_chain_select_element_process($element, &$form_state, $form) {

  $element_name = $element['#name'];
  $config = !empty($element['#config']) ? $element['#config'] : array();
  $required_levels = !empty($element['#required_levels']) ? $element['#required_levels'] : 0;
  $data_callback = !empty($element['#data_callback']) ? $element['#data_callback'] : '';
  $settings = array(
    'show_throbber' => isset($element['#show_throbber']) ? $element['#show_throbber'] : TRUE,
    'progress_message' => isset($element['#progress_message']) ? $element['#progress_message'] : t('Please wait..'),
  );

  if (!function_exists($data_callback)) {
    return array('#markup' => 'Data callback not defined');
  }

  // Checking if the form has been sumbitted or not.
  $is_submitted = (!empty($form_state['input']));
  $submitted_values = $form_state['values'][$element_name];

  $chain_select_element = array(
    '#array_parents' => array(),
    '#tree' => FALSE,
    '#attached' => array(
      'js' => array(drupal_get_path('module', 'ajax_chain_select') . '/ajax_chain_select.js'),
    ),
  );

  $chain_select_element[$element_name] = array(
    '#element_name' => $element_name,
    '#type' => 'fieldset',
    '#tree' => TRUE,
    '#id' => !empty($element['#id']) ? $element['#id'] : drupal_html_id('edit-' . implode('-', $element['#parents'])),
    '#title' => !empty($element['#title']) ? $element['#title'] : '',
    '#title_display' => !empty($element['#title_display']) ? $element['#title_display'] : 'before',
    '#array_parents' => array(),
    '#element_validate' => array('ajax_chain_select_custom_validate'),
    '#states' => !empty($element['#states']) ? $element['#states'] : array(),
    '#config' => $config,
    '#data_callback' => $data_callback,
  );

  $chain_select_element[$element_name]['#attached']['js'][] = array(
    'type' => 'setting',
    'data' => array('ajax_chain_select' => array($chain_select_element[$element_name]['#id'] => $settings)),
  );

  $index = 0;
  $levels_count = count($config);
  $levels = array_keys($config);
  $previous_level = $levels[0];
  $previous_level_config = $config[$previous_level];

  foreach ($config as $level => $level_config) {
    $data = array();

    switch ($index) {
      case 0:
        $data = $data_callback($level);
        break;

      default:
        if ($is_submitted) {
          if (!empty($submitted_values[$previous_level])) {
            $data = $data_callback($level, $submitted_values[$previous_level]);
          }
        }
        else {
          if (!empty($previous_level_config['#default_value'])) {
            $data = $data_callback($level, $previous_level_config['#default_value']);
          }
        }
        break;
    }

    // Default value must be part of data of that level, if not, nullify it.
    if (!empty($level_config['#default_value']) && !in_array($level_config['#default_value'], array_keys($data))) {
      unset($level_config['#default_value']);
    }

    $chain_select_element[$element_name][$level] = array(
      '#type' => 'select',
      '#options' => $data,
      '#title' => !empty($level_config['#title']) ? $level_config['#title'] : '',
      '#empty_option' => !empty($level_config['#empty_option']) ? $level_config['#empty_option'] : t('- Select -'),
      '#required' => ($index < $required_levels) ? TRUE : FALSE,
      '#validated' => TRUE,
      '#default_value' => !empty($level_config['#default_value']) ? $level_config['#default_value'] : NULL,
      '#title_display' => !empty($level_config['#title_display']) ? $level_config['#title_display'] : 'before',
      '#disabled' => (empty($data)) ? TRUE : FALSE,
      '#attributes' => array('level' => $level),
    );

    if ($index != $levels_count - 1) {
      $chain_select_element[$element_name][$level]['#attributes']['class'] = array('ajax-chain-select-select');
    }

    $index++;
    $previous_level = $level;
    $previous_level_config = $level_config;
  }

  $chain_select_element[$element_name]['dc'] = array(
    '#type' => 'hidden',
    '#value' => base64_encode($element['#data_callback']),
    '#attributes' => ['class' => ['acs-dc']],
  );

  $chain_select_element[$element_name]['dch'] = array(
    '#type' => 'hidden',
    '#value' => ajax_chain_select_get_token($element['#data_callback']),
    '#attributes' => ['class' => ['acs-dch']],
  );

  return $chain_select_element;
}

/**
 * Custom function for ac_select element validate.
 */
function ajax_chain_select_custom_validate(&$element, &$form_state, $form) {
  // Clean up fields 'dc' and 'dch'.
  $element_name = $element['#element_name'];
  unset($form_state['values'][$element_name]['dc']);
  unset($form_state['values'][$element_name]['dch']);

  $data_callback = $element['#data_callback'];
  $config = $element['#config'];
  $values = $form_state['values'];

  $index = 0;
  $levels = array_keys($config);
  $previous_level = $levels[0];

  foreach ($config as $level => $level_config) {

    if ($index > 0) {
      $data = $data_callback($level, $values[$element_name][$previous_level]);

      if (!empty($data)) {

        if (empty($element[$level]['#options'])) {
          $element[$level]['#options'] = $data;
        }
        $element[$level]['#validated'] = FALSE;
        _form_validate($element[$level], $form_state);
      }
    }
    else {
      $element[$level]['#validated'] = FALSE;
      _form_validate($element[$level], $form_state);
    }

    $index++;
    $previous_level = $level;
  }
}

/**
 * Callback function for fetching data for next step of ac_select.
 */
function ajax_chain_select_element_callback($level = 1, $previous_level_key = 0, $dc = NULL, $dch = NULL) {
  $has_data = '0';
  $data_callback = '';
  $options = '';

  if (!empty($dc)) {
    $dc2 = base64_decode($dc);
    if (ajax_chain_select_valid_token($dch, $dc2) && function_exists($dc2)) {
      $data_callback = $dc2;
      $data = $data_callback($level, $previous_level_key);
    }
  }

  if (!empty($data)) {
    $has_data = '1';
    foreach ($data as $key => $value) {
      $options .= '<option value="' . $key . '">' . $value . '</option>';
    }
  }
  drupal_json_output(array('has_data' => $has_data, 'options' => $options));
}

/**
 * Generates a token based on $value, and the private key.
 *
 * Note: This is similar to drupal_get_token but without using session_id.
 *
 * @param string $value
 *   An additional value to base the token on.
 *
 * @return string
 *   A 43-character URL-safe token for validation.
 */
function ajax_chain_select_get_token($value = '') {
  return drupal_hmac_base64($value, drupal_get_private_key() . drupal_get_hash_salt());
}

/**
 * Validates a token based on $value and the private key.
 *
 * Note: This is similar to drupal_valid_token but without using session_id.
 *
 * @param string $token
 *   The token to be validated.
 * @param string $value
 *   An additional value to base the token on.
 *
 * @return bool
 *   True for a valid token, false for an invalid token.
 */
function ajax_chain_select_valid_token($token, $value = '') {
  return ($token === ajax_chain_select_get_token($value));
}