Add a new check for Solr core availability.

This is intended to be used with the silverstripe/fulltextsearch
module.

code/checks/SolrIndexCheck.php

@@ -0,0 +1,44 @@
+<?php
+/**
+ * Check the availability of all Solr indexes of given class.
+ * If there are no indexes of given class found, the returned status will still be "OK".
+ *
+ * @param $indexClass Limit the index checks to the specified class and all its subclasses.
+ */
+class SolrIndexCheck implements EnvironmentCheck {
+
+	protected $indexClass;
+	
+	function __construct($indexClass = null) {
+		$this->indexClass = $indexClass;
+	}
+	
+	function check() {
+		$brokenCores = array();
+
+		if (!class_exists('Solr')) {
+			return array(
+				EnvironmentCheck::ERROR,
+				'Class `Solr` not found. Is the fulltextsearch module installed?'
+			);
+		}
+
+		$service = Solr::service();
+		foreach (Solr::get_indexes($this->indexClass) as $index) {
+			$core = $index->getIndexName();
+			if (!$service->coreIsActive($core)) {
+				$brokenCores[] = $core;
+			}
+		}
+
+		if (!empty($brokenCores)) {
+			return array(
+				EnvironmentCheck::ERROR,
+				'The following indexes are unavailable: ' . implode($brokenCores, ', ')
+			);
+		}
+
+		return array(EnvironmentCheck::OK, 'Expected indexes are available.');
+	}
+
+}