doc/lib: Add `DocTree' for representing a documentation as tree of sections

refs #4820

modules/doc/library/Doc/DocTree.php

@@ -0,0 +1,80 @@
+<?php
+// {{{ICINGA_LICENSE_HEADER}}}
+// {{{ICINGA_LICENSE_HEADER}}}
+
+namespace Icinga\Module\Doc;
+
+use LogicException;
+use Icinga\Data\Identifiable;
+use Icinga\Data\Tree\Node;
+
+/**
+ * Documentation tree
+ */
+class DocTree extends Node
+{
+    /**
+     * All nodes of the tree
+     *
+     * @var array
+     */
+    protected $nodes = array();
+
+    /**
+     * Append a root node to the tree
+     *
+     * @param Identifiable $root
+     */
+    public function addRoot(Identifiable $root)
+    {
+        $rootId = $root->getId();
+        if (isset($this->nodes[$rootId])) {
+            $rootId = uniqid($rootId);
+//            throw new LogicException(
+//                sprintf('Can\'t add root node: a root node with the id \'%s\' already exists', $rootId)
+//            );
+        }
+        $this->nodes[$rootId] = $this->appendChild($root);
+    }
+
+    /**
+     * Append a child node to a parent node
+     *
+     * @param   Identifiable $child
+     * @param   Identifiable $parent
+     *
+     * @throws  LogicException If the the tree does not contain the parent node
+     */
+    public function addChild(Identifiable $child, Identifiable $parent)
+    {
+        $childId = $child->getId();
+        $parentId = $parent->getId();
+        if (isset($this->nodes[$childId])) {
+            $childId = uniqid($childId);
+//            throw new LogicException(
+//                sprintf('Can\'t add child node: a child node with the id \'%s\' already exists', $childId)
+//            );
+        }
+        if (! isset($this->nodes[$parentId])) {
+            throw new LogicException(
+                sprintf('Can\'t add child node: there\'s no parent node having the id \'%s\'', $parentId)
+            );
+        }
+        $this->nodes[$childId] = $this->nodes[$parentId]->appendChild($child);
+    }
+
+    /**
+     * Get a node
+     *
+     * @param   mixed $id
+     *
+     * @return  Node|null
+     */
+    public function getNode($id)
+    {
+        if (! isset($this->nodes[$id])) {
+            return null;
+        }
+        return $this->nodes[$id];
+    }
+}