Use wire protocol version constants for feature detection

This removes some copypasta from existing Database and Collection code.

Author: jmikola

src/Collection.php

@@ -309,10 +309,7 @@ public function createIndexes(array $indexes)
         $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
         $server = $this->manager->selectServer($readPreference);
 
-        $serverInfo = $server->getInfo();
-        $maxWireVersion = isset($serverInfo['maxWireVersion']) ? $serverInfo['maxWireVersion'] : 0;
-
-        return ($maxWireVersion >= 2)
+        return (FeatureDetection::isSupported($server, FeatureDetection::API_CREATEINDEXES_CMD))
             ? $this->createIndexesCommand($server, $indexes)
             : $this->createIndexesLegacy($server, $indexes);
     }
@@ -1019,10 +1016,7 @@ public function listIndexes()
         $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
         $server = $this->manager->selectServer($readPreference);
 
-        $serverInfo = $server->getInfo();
-        $maxWireVersion = isset($serverInfo['maxWireVersion']) ? $serverInfo['maxWireVersion'] : 0;
-
-        return ($maxWireVersion >= 3)
+        return (FeatureDetection::isSupported($server, FeatureDetection::API_LISTINDEXES_CMD))
             ? $this->listIndexesCommand($server)
             : $this->listIndexesLegacy($server);
     }

src/Database.php

@@ -101,10 +101,7 @@ public function listCollections(array $options = array())
         $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
         $server = $this->manager->selectServer($readPreference);
 
-        $serverInfo = $server->getInfo();
-        $maxWireVersion = isset($serverInfo['maxWireVersion']) ? $serverInfo['maxWireVersion'] : 0;
-
-        return ($maxWireVersion >= 3)
+        return (FeatureDetection::isSupported($server, FeatureDetection::API_LISTCOLLECTIONS_CMD))
             ? $this->listCollectionsCommand($server, $options)
             : $this->listCollectionsLegacy($server, $options);
     }

src/FeatureDetection.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace MongoDB;
+
+use MongoDB\Driver\Server;
+
+/**
+ * Utility class for detecting features based on wire protocol versions.
+ *
+ * @internal
+ */
+class FeatureDetection
+{
+    const API_LISTCOLLECTIONS_CMD = 3;
+    const API_LISTINDEXES_CMD = 3;
+    const API_CREATEINDEXES_CMD = 2;
+
+    /**
+     * Return whether the server supports a particular feature.
+     *
+     * @param Server  $server  Server to check
+     * @param integer $feature Feature constant (i.e. wire protocol version)
+     * @return boolean
+     */
+    static public function isSupported(Server $server, $feature)
+    {
+        $info = $server->getInfo();
+        $maxWireVersion = isset($info['maxWireVersion']) ? (integer) $info['maxWireVersion'] : 0;
+        $minWireVersion = isset($info['minWireVersion']) ? (integer) $info['minWireVersion'] : 0;
+
+        return ($minWireVersion <= $feature && $maxWireVersion >= $feature);
+    }
+}