--- /dev/null
+<?php
+
+/*
+ * This file is part of Psy Shell.
+ *
+ * (c) 2012-2018 Justin Hileman
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Psy\CodeCleaner;
+
+use PhpParser\Node;
+use PhpParser\Node\Name;
+use PhpParser\Node\Name\FullyQualified as FullyQualifiedName;
+use PhpParser\Node\Stmt\GroupUse;
+use PhpParser\Node\Stmt\Namespace_;
+use PhpParser\Node\Stmt\Use_;
+use PhpParser\NodeTraverser;
+
+/**
+ * Provide implicit use statements for subsequent execution.
+ *
+ * The use statement pass remembers the last use statement line encountered:
+ *
+ * use Foo\Bar as Baz;
+ *
+ * ... which it then applies implicitly to all future evaluated code, until the
+ * current namespace is replaced by another namespace.
+ */
+class UseStatementPass extends CodeCleanerPass
+{
+ private $aliases = [];
+ private $lastAliases = [];
+ private $lastNamespace = null;
+
+ /**
+ * Re-load the last set of use statements on re-entering a namespace.
+ *
+ * This isn't how namespaces normally work, but because PsySH has to spin
+ * up a new namespace for every line of code, we do this to make things
+ * work like you'd expect.
+ *
+ * @param Node $node
+ */
+ public function enterNode(Node $node)
+ {
+ if ($node instanceof Namespace_) {
+ // If this is the same namespace as last namespace, let's do ourselves
+ // a favor and reload all the aliases...
+ if (strtolower($node->name) === strtolower($this->lastNamespace)) {
+ $this->aliases = $this->lastAliases;
+ }
+ }
+ }
+
+ /**
+ * If this statement is a namespace, forget all the aliases we had.
+ *
+ * If it's a use statement, remember the alias for later. Otherwise, apply
+ * remembered aliases to the code.
+ *
+ * @param Node $node
+ */
+ public function leaveNode(Node $node)
+ {
+ if ($node instanceof Use_) {
+ // Store a reference to every "use" statement, because we'll need
+ // them in a bit.
+ foreach ($node->uses as $use) {
+ $alias = $use->alias ?: end($use->name->parts);
+ $this->aliases[strtolower($alias)] = $use->name;
+ }
+
+ return NodeTraverser::REMOVE_NODE;
+ } elseif ($node instanceof GroupUse) {
+ // Expand every "use" statement in the group into a full, standalone
+ // "use" and store 'em with the others.
+ foreach ($node->uses as $use) {
+ $alias = $use->alias ?: end($use->name->parts);
+ $this->aliases[strtolower($alias)] = Name::concat($node->prefix, $use->name, [
+ 'startLine' => $node->prefix->getAttribute('startLine'),
+ 'endLine' => $use->name->getAttribute('endLine'),
+ ]);
+ }
+
+ return NodeTraverser::REMOVE_NODE;
+ } elseif ($node instanceof Namespace_) {
+ // Start fresh, since we're done with this namespace.
+ $this->lastNamespace = $node->name;
+ $this->lastAliases = $this->aliases;
+ $this->aliases = [];
+ } else {
+ foreach ($node as $name => $subNode) {
+ if ($subNode instanceof Name) {
+ // Implicitly thunk all aliases.
+ if ($replacement = $this->findAlias($subNode)) {
+ $node->$name = $replacement;
+ }
+ }
+ }
+
+ return $node;
+ }
+ }
+
+ /**
+ * Find class/namespace aliases.
+ *
+ * @param Name $name
+ *
+ * @return FullyQualifiedName|null
+ */
+ private function findAlias(Name $name)
+ {
+ $that = strtolower($name);
+ foreach ($this->aliases as $alias => $prefix) {
+ if ($that === $alias) {
+ return new FullyQualifiedName($prefix->toString());
+ } elseif (substr($that, 0, strlen($alias) + 1) === $alias . '\\') {
+ return new FullyQualifiedName($prefix->toString() . substr($name, strlen($alias)));
+ }
+ }
+ }
+}