drafting

composer.json

@@ -19,7 +19,8 @@
   },
   "autoload": {
     "psr-4": {
-      "Oliva\\Utils\\Tree\\": "src/"
+      "Oliva\\Utils\\Tree\\": "src/",
+      "Dakujem\\Oliva\\": "lib/"
     }
   },
   "scripts": {

lib/DataNodeContract.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Dakujem\Oliva;
+
+/**
+ * DataNodeContract
+ *
+ * @author Andrej Rypak <xrypak@gmail.com>
+ */
+interface DataNodeContract
+{
+    /**
+     * @return mixed
+     */
+    public function data(); //:mixed;
+}

lib/TreeNodeContract.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Dakujem\Oliva;
+
+/**
+ * Base contract supporting tree traversals.
+ *
+ * @author Andrej Rypak <xrypak@gmail.com>
+ */
+interface TreeNodeContract
+{
+    public function parent(): ?TreeNodeContract;
+
+    public function children(): iterable;
+
+    /**
+     * Returns `true` if the node has no children.
+     */
+    public function isLeaf(): bool;
+
+    /**
+     * Get a specific child.
+     *
+     * @param string|int $index
+     * @return mixed
+     */
+    public function child(/*string|int*/ $index): ?TreeNodeContract;
+
+    /**
+     * @return string|int|null
+     */
+    public function childIndex(TreeNodeContract $node);//:mixed;
+}

lib/readme.md

@@ -20,3 +20,6 @@ refactor
 - traits into classes
 - ditch all PHP 5 constructs
 - fully typed
+
+add
+- address object/interface

tests/builder.SimpleBuilder.phpt

@@ -21,10 +21,24 @@ subroutine2();
 
 function subroutine1()
 {
-	$data = ['a' => 'a', 'b' => 'b', 'children' => [
-			['c' => 'c', 'children' => [['e' => 'e', 'f' => 'f',]]],
-			['d' => 'd', 'children' => [['g' => 'g', 'h' => 'h',]]],
-	]];
+    $data = [
+        'a' => 'a',
+        'b' => 'b',
+        'children' => [
+            [
+                'c' => 'c',
+                'children' => [
+                    ['e' => 'e', 'f' => 'f',],
+                ],
+            ],
+            [
+                'd' => 'd',
+                'children' => [
+                    ['g' => 'g', 'h' => 'h',],
+                ],
+            ],
+        ],
+    ];
 
 	$builder = new SimpleTreeBuilder('children');
 	$root = $builder->build($data);