add NodeTraverser

lib/PHPParser/NodeTraverser.php

@@ -0,0 +1,82 @@
+<?php
+
+class PHPParser_NodeTraverser
+{
+    const ON_ENTER = 1;
+    const ON_LEAVE = 2;
+
+    protected $enterVisitors;
+    protected $leaveVisitors;
+
+    /**
+     * Constructs a node traverser.
+     */
+    public function __construct() {
+        $this->enterVisitors = $this->leaveVisitors = array();
+    }
+
+    /**
+     * Adds a node visitor.
+     *
+     * The callback gets the node passed as only argument and may return a replacement for the node
+     * or return null/nothing, in which case the node is left untouched.
+     *
+     * The mode specifies when the node should be visited:
+     *  * using self::ON_ENTER the node is visited before traversing its sub nodes
+     *  * using self::ON_LEAVE the node is visited after traversing its sub nodes
+     *  * using self::ON_ENTER | self::ON_LEAVE the node is visited both before and after traversing
+     *    its subnodes
+     * The default is to visit the node ON_ENTER.
+     *
+     * Visitors are called in the order they were registered in.
+     *
+     * @param callback $visitor Visitor callback
+     * @param int      $mode    Visitor mode (bitmap using self::ON_ENTER and self::ON_LEAVE)
+     */
+    public function addVisitor($visitor, $mode = self::ON_ENTER) {
+        if (!is_callable($visitor)) {
+            throw new InvalidArgumentException('Visitor not callable');
+        }
+
+        if ($mode & self::ON_ENTER) {
+            $this->enterVisitors[] = $visitor;
+        }
+
+        if ($mode & self::ON_LEAVE) {
+            $this->leaveVisitors[] = $visitor;
+        }
+    }
+
+    /**
+     * Traverses a node or an array using the registered visitors.
+     *
+     * @param  PHPParser_NodeAbstract|array $node Node or array
+     *
+     * @return mixed Node after all visitors were applied.
+     */
+    public function traverse($node) {
+        if ($node instanceof PHPParser_NodeAbstract) {
+            foreach ($this->enterVisitors as $visitor) {
+                if (null !== $return = call_user_func($visitor, $node)) {
+                    $node = $return;
+                }
+            }
+        }
+
+        if (is_array($node) || $node instanceof Traversable) {
+            foreach ($node as &$subNode) {
+                $subNode = $this->traverse($subNode);
+            }
+        }
+
+        if ($node instanceof PHPParser_NodeAbstract) {
+            foreach ($this->leaveVisitors as $visitor) {
+                if (null !== $return = call_user_func($visitor, $node)) {
+                    $node = $return;
+                }
+            }
+        }
+
+        return $node;
+    }
+}