doc/lib: Add DocTocHtmlRenderer class to render a toc to HTML

refs #4820

modules/doc/library/Doc/DocTocHtmlRenderer.php

@@ -0,0 +1,45 @@
+<?php
+// {{{ICINGA_LICENSE_HEADER}}}
+// {{{ICINGA_LICENSE_HEADER}}
+
+namespace Icinga\Module\Doc;
+
+use RecursiveIteratorIterator;
+
+class DocTocHtmlRenderer extends RecursiveIteratorIterator
+{
+    protected $html = array();
+
+    public function __construct(DocToc $toc)
+    {
+        parent::__construct($toc, RecursiveIteratorIterator::SELF_FIRST);
+    }
+
+    public function beginIteration()
+    {
+        $this->html[] = '<ul>';
+    }
+
+    public function endIteration()
+    {
+        $this->html[] = '</ul>';
+    }
+
+    public function beginChildren()
+    {
+        $this->html[] = '<ul>';
+    }
+
+    public function endChildren()
+    {
+        $this->html[] = '</ul>';
+    }
+
+    public function render($callback)
+    {
+        foreach ($this as $node) {
+            $this->html[] = $callback($node->getValue());
+        }
+        return implode("\n", $this->html);
+    }
+}