Provide basic scaffolding for the Query and QueryType interfaces

src/QueryInterface.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\facetapi\QueryInterface.
+ */
+
+namespace Drupal\facetapi;
+
+use Drupal\Core\Config\Entity\ConfigEntityInterface;
+
+/**
+ * In D7 this interface did not exist.
+ * We are creating this interface so functions can be moved here from the adapter interface.
+ */
+interface QueryInterface extends ConfigEntityInterface {
+
+}
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src/QueryTypeInterface.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\facetapi\QueryTypeInterface.
+ */
+
+namespace Drupal\facetapi;
+
+use Drupal\Core\Config\Entity\ConfigEntityInterface;
+
+/**
+ * This interface was called FacetapiQueryTypeInterface but the name would then no longer be consistent
+ * with the current best practises.
+ *
+ * In D7 this was the interface implemented by all query type plugins.
+ *
+ * Facet API does not perform any facet calculations on it's own. The query type
+ * plugin system provides Facet API with a consistent way to tell backends what
+ * type of query to execute in order to return the appropriate data required
+ * for the faceted navigation display.
+ *
+ * Query type plugins are implemented by the backends and perform the
+ * alterations of their internal search engine query mechanisms to execute the
+ * filters and retrieve facet data. For example, modules that integrate with
+ * Apache Solr will set the necessary params for faceting, whereas modules that
+ * extend the core Search module will add SQL joins, filter clauses, and COUNT
+ * queries in order to implement faceting.
+ *
+ * Although the actual method of querying the search engine is vastly different
+ * per backend, Facet API operates under the assumption that the types of
+ * queries are the same. For example, a "term" query is assumed to be a straight
+ * filter, whereas a "range" query is assumed to be a search between two values.
+ * Although the common query types such as "term" and "date" should be available
+ * to all backends, it is expected that some backends will have additional query
+ * types based on capability. For example, backends integrating with the Apache
+ * Solr engine might have a "geospatial" query type that modules integrating
+ * with the core Search won't have.
+ *
+ * All functions and comments in this class have currently been copy/pasted verbatim
+ * and then tweaked to provide a skeleton that describes what the D7 version used to handle.
+ */
+interface QueryTypeInterface extends ConfigEntityInterface {
+  /**
+   * Returns the query type associated with the plugin.
+   *
+   * Query types must be standard across all backends. For example, the common
+   * "term" query type must execute the same type of query for backends that
+   * integrate with Apache Solr, the core Search module, or any other search
+   * engine that implementing modules connect to.
+   *
+   * It is recommended that the strings returned by this method contain only
+   * lowercase letters with optional underscores.
+   *
+   * @return string
+   *   The query type.
+   */
+  static public function getType();
+
+  /**
+   * Alters the backend's native query object to execute the facet query.
+   *
+   * As an example, modules that integrate with Apache Solr will set the
+   * necessary params for faceting, whereas modules that extend the core Search
+   * module will add SQL joins, filter clauses, and COUNT queries in order to
+   * implement faceting.
+   *
+   * @param mixed $query
+   *   The backend's native query object.
+   */
+  public function execute($query);
+
+  /**
+   * Gets data from the server and adds values to the facet's render array.
+   *
+   * At a minimum this method should add the index values returned by the
+   * search server as keys containing associative arrays with the "#count" key.
+   * The end result will be an array structured like the one below:
+   *
+   * <code>
+   * $build = array(
+   *   'index-value-1' => array('#count' => 3),
+   *   'index-value-2' => array('#count' => 19),
+   *   'index-value-3' => array('#count' => 82),
+   *   ...
+   * );
+   * </code>
+   *
+   * See the return of the FacetapiFacetProcessor::initializeBuild() for all
+   * possible values that could be populated. Query type plugins such as "date"
+   * types will populte the #item_children, #item_parents, and #active keys in
+   * addition to #count.
+   *
+   * @return array
+   *   The initialized render array. For all possible values of the structure of
+   *   the array, see the FacetapiFacetProcessor::initializeBuild() docblock.
+   *   Usually only the #count key is used.
+   *
+   * @see FacetapiFacetProcessor::initializeBuild()
+   */
+  public function build();
+} 
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