Add GraphViz renderer.

spec/drupol/phptree/tests/TestGraphVizSpec.php

@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace spec\drupol\phptree\tests;
+
+use drupol\phptree\Node\ValueNode;
+use drupol\phptree\tests\TestGraphViz;
+use drupol\phptree\Visitor\BreadthFirstVisitor;
+use PhpSpec\ObjectBehavior;
+
+class TestGraphVizSpec extends ObjectBehavior
+{
+    public function it_is_initializable()
+    {
+        $visitor = new BreadthFirstVisitor();
+
+        $this->beConstructedWith($visitor);
+
+        $this->shouldHaveType(TestGraphViz::class);
+    }
+
+    public function it_can_create_a_graph()
+    {
+        $this->beConstructedWith(new BreadthFirstVisitor());
+
+        $tree = new ValueNode('root', 2);
+
+        $nodes = [];
+        foreach (\range('A', 'F') as $letter) {
+            $nodes[] = new ValueNode($letter, 2);
+        }
+
+        $tree->add(...$nodes);
+
+        $result = <<< EOF
+digraph G {
+  "root" -> "A"
+  "root" -> "B"
+  "A" -> "C"
+  "A" -> "D"
+  "B" -> "E"
+  "B" -> "F"
+}
+EOF;
+
+        $this
+            ->render($tree)
+            ->shouldReturn($result . PHP_EOL);
+    }
+}

spec/src/TestGraphViz.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace drupol\phptree\tests;
+
+use drupol\phptree\Node\NodeInterface;
+use drupol\phptree\Render\GraphViz;
+
+/**
+ * Class TestGraphViz
+ */
+class TestGraphViz extends GraphViz
+{
+    /**
+     * {@inheritdoc}
+     */
+    protected function hash(NodeInterface $node)
+    {
+        return $node->getValue();
+    }
+}

src/Render/GraphViz.php

@@ -0,0 +1,88 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace drupol\phptree\Render;
+
+use drupol\phptree\Node\NodeInterface;
+use drupol\phptree\Visitor\VisitorInterface;
+use Fhaculty\Graph\Graph;
+
+/**
+ * Class GraphViz
+ */
+class GraphViz implements RendererInterface
+{
+    /**
+     * @var \drupol\phptree\Visitor\VisitorInterface
+     */
+    private $visitor;
+
+    /**
+     * @var \Fhaculty\Graph\Graph
+     */
+    private $graph;
+
+    /**
+     * @var array
+     */
+    private $nodes;
+
+    /**
+     * @var \Graphp\GraphViz\GraphViz
+     */
+    private $graphviz;
+
+    /**
+     * GraphViz constructor.
+     *
+     * @param \drupol\phptree\Visitor\VisitorInterface $visitor
+     */
+    public function __construct(VisitorInterface $visitor)
+    {
+        $this->visitor = $visitor;
+        $this->graph = new Graph();
+        $this->graphviz = new \Graphp\GraphViz\GraphViz();
+        $this->nodes = [];
+    }
+
+    /**
+     * @param \drupol\phptree\Node\NodeInterface $node
+     *
+     * @return string
+     */
+    public function render(NodeInterface $node): string
+    {
+        foreach ($this->visitor->traverse($node) as $child) {
+            $hash_parent = $this->hash($child);
+
+            if (!isset($this->nodes[$hash_parent])) {
+                $this->nodes[$hash_parent] = $this->graph->createVertex($hash_parent);
+            }
+
+            if (null === $parent = $child->getParent()) {
+                continue;
+            }
+
+            $hash = $this->hash($parent);
+
+            if (!isset($this->nodes[$hash])) {
+                $this->nodes[$hash] = $this->graph->createVertex($hash);
+            }
+
+            $this->nodes[$hash]->createEdgeTo($this->nodes[$hash_parent]);
+        }
+
+        return $this->graphviz->createScript($this->graph);
+    }
+
+    /**
+     * @param \drupol\phptree\Node\NodeInterface $node
+     *
+     * @return int
+     */
+    protected function hash(NodeInterface $node)
+    {
+        return (int) \spl_object_hash($node);
+    }
+}

src/Render/RendererInterface.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace drupol\phptree\Render;
+
+use drupol\phptree\Node\NodeInterface;
+
+/**
+ * Interface RendererInterface
+ */
+interface RendererInterface
+{
+    /**
+     * @param \drupol\phptree\Node\NodeInterface $node
+     */
+    public function render(NodeInterface $node);
+}