Expose field data to entity api

Problem/Motivation

Content saved in the Youtube field type is currently not available for use in modules that rely on the Entity API for unified access to entity properties and fields. For example:

1. Rules
2. Search API

Proposed resolution

Follow the Entity API Handbook documentation for developers wishing to provide information about custom entity properties (including fields). This involves implementing hook_entity_property_info() to describe the getters, setters, permissions and schema that is used for the Youtube field type attached to various entity types.

Luckily the Entity API already provides some generic callbacks that can be used for accessing fields, so initial integration would be simple to accomplish and allow access through a generic getter callback very quickly and easily. With a generic getter callback, integration would be opened-up to:

Rules

The Rules module allows site administrators to define conditionally executed actions based on occurring events. Entity API integration for the Youtube module would allow Youtube field data to be used in Rules based event actions.

Search API

The Search API module provides a framework for easily creating searches on any entity known to Drupal, using any kind of search engine. By adding Entity API integration into the Youtube module, any entity fields that use the Youtube field type would then be able to be indexed by any search engine using the Search API.

Entity Metadata Wrapper

The most well-known and popular part of the Entity API is its entity metadata wrapper, which greatly simplifies the developer experience when accessing entity field data. By exposing the Youtube field type through Entity API you will be greatly simplifying its use for developers.

Example using Drupal 7.x core Field API:

$node = node_load($node_id);
$field_name = 'field_youtube_video';
$field_items = field_get_items('node', $node, $field_name);
$values = array();
if (is_array($field_items)) {
  foreach ($field_items as $delta => $item) {
    $values["{$field_name}_{$delta}"] = field_view_value('node', $node, $field_name, $item);
  }
}

Example using Entity API:

$node = node_load($node_id);
$field_name = 'field_youtube_video';
$node_metadata = entity_metadata_wrapper('node', $node);
$values = $node_metadata->{$field_name}->value();

Original report by andyg5000

Expose field property metadata to the entity api so that this module can be used by others that depend the metadata (ie: Rules, Search API).

Patch attached.