Add a new Modifier and its tests.

Author: drupol

spec/drupol/phptree/Modifier/ReverseSpec.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace spec\drupol\phptree\Modifier;
+
+use drupol\phptree\Modifier\Reverse;
+use drupol\phptree\Node\ValueNode;
+use PhpSpec\ObjectBehavior;
+
+class ReverseSpec extends ObjectBehavior
+{
+    public function it_is_initializable()
+    {
+        $this->shouldHaveType(Reverse::class);
+    }
+
+    public function it_can_reverse_a_tree()
+    {
+        $tree1 = new ValueNode('root');
+
+        $nodes = [];
+        foreach (\range('A', 'E') as $value) {
+            $nodes[] = new ValueNode($value);
+        }
+        $tree1->add(...$nodes);
+
+        $tree2 = new ValueNode('root');
+        $tree2->add(...\array_reverse($nodes));
+
+        $this
+            ->modify($tree1)
+            ->count()
+            ->shouldReturn(5);
+
+        // @todo write better test here and test all children and recursively.
+        $this
+            ->modify($tree1)
+            ->children()->current()->getValue()
+            ->shouldReturn('E');
+    }
+}

src/Modifier/Reverse.php

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+<?php
+
+declare(strict_types = 1);
+
+namespace drupol\phptree\Modifier;
+
+use drupol\phptree\Node\NodeInterface;
+
+/**
+ * Class Reverse
+ */
+class Reverse implements ModifierInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function modify(NodeInterface $tree): NodeInterface
+    {
+        $children = new \ArrayObject();
+        
+        foreach ($tree->children() as $child) {
+            $children->append($this->modify($child));
+        }
+
+        $newTree = $tree->withChildren();
+
+        for ($i = $children->count()-1; $i >= 0; $i--) {
+            $newTree->add($children[$i]);
+        }
+
+        return $newTree;
+    }
+}