<?php

/**
 * Implements hook_theme().
 */
function field_object_theme() {
  return array(
    'field_object_label' => array(
      'variables' => array(
        'field' => array(),
        'instance' => array(),
      ),
    ),
  );
}

/**
 * Implements hook_field_info().
 */
function field_object_field_info() {
  return array(
    'field_object' => array(
      'label' => t('Field Reference'),
      'description' => t('Refers to a field instance.'),
      'settings' => array(),
      'instance_settings' => array(
        'function' => NULL,
      ),
      'default_widget' => 'options_select',
      'default_formatter' => 'field_object_label',
      'no_ui' => TRUE,
      'property_type' => 'text',
    ),
  );
}

/**
 * Implements hook_field_widget_info_alter().
 */
function field_object_field_widget_info_alter(array &$info) {
  $info['options_select']['field types'][] = 'field_config_reference';
}

/**
 * Implements hook_field_formatter_info().
 */
function field_object_field_formatter_info() {
  return array(
    'field_object_label' => array(
      'label' => t('Label'),
      'description' => t("The field instance's label."),
      'field types' => array('field_object'),
      'settings' => array(),
    ),
  );
}

/**
 * Implements hook_field_is_empty().
 */
function field_object_field_is_empty(array $item, array $field) {
  return empty($item['path']);
}

/**
 * Implements hook_field_formatter_view().
 */
function field_object_field_formatter_view($entity_type, $entity, array $field, array $instance, $language, array $items, array $display) {
  $element = array();

  foreach ($items as $delta => $item) {
    $label = array();

    foreach (_field_object_expand_path($item['path']) as $field) {
      $label[] = theme('field_object_label', $field);
    }

    $element[$delta]['#markup'] = implode(' » ', $label);
  }

  return $element;
}

/**
 * Implements hook_options_list().
 */
function field_object_options_list(array $field, array $instance, $entity_type, $entity) {
  return _field_object_build_hierarchy($field, $instance, $entity_type, $entity)->options();
}

/**
 * Renders a human-readable label for a field instance, including the entity
 * type and (if applicable) bundle that hosts it.
 */
function theme_field_object_label(array $variables) {
  $instance = $variables['instance'];

  $output = '';

  if ($instance['entity_type'] != 'field_collection_item') {
    $entity_type = entity_get_info($instance['entity_type']);
    $output = $entity_type['label'] . ' » ';

    if ($entity_type['entity keys']['bundle']) {
      $output .= $entity_type['bundles'][ $instance['bundle'] ]['label'] . ' » ';
    }
  }

  return $output . $instance['label'];
}

/**
 * Helper function. Builds a FieldHierarchy object for the widget builder.
 */
function _field_object_build_hierarchy(array $field, array $instance, $entity_type, $entity) {
  $hierarchy = new FieldHierarchy();

  // The instance should define a function which returns an array of FieldChain
  // objects to be added to the hierarchy.
  $function = $instance['settings']['function'];

  if ($function && is_callable($function)) {
    $arguments = func_get_args();
    $chains = (array) call_user_func_array($function, $arguments);

    array_walk($chains, array($hierarchy, 'addChain'));
  }

  return $hierarchy;
}

/**
 * Helper function. Expands a field reference's path value into an array
 * of field and instance definitions.
 */
function _field_object_expand_path($path) {
  $output = array();

  foreach (explode('::', $path) as $instance) {
    list ($entity_type, $bundle, $field) = explode(':', $instance);

    $output[] = array(
      'field' =>
        field_info_field($field),
      'instance' =>
        field_info_instance($entity_type, $field, $bundle),
    );
  }

  return $output;
}