--- /dev/null
+<?php
+
+/*
+ * This file is part of Psy Shell.
+ *
+ * (c) 2012-2017 Justin Hileman
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Psy\VersionUpdater;
+
+use Psy\Shell;
+
+class GitHubChecker implements Checker
+{
+ const URL = 'https://api.github.com/repos/bobthecow/psysh/releases/latest';
+
+ private $latest;
+
+ /**
+ * @return bool
+ */
+ public function isLatest()
+ {
+ return version_compare(Shell::VERSION, $this->getLatest(), '>=');
+ }
+
+ /**
+ * @return string
+ */
+ public function getLatest()
+ {
+ if (!isset($this->latest)) {
+ $this->setLatest($this->getVersionFromTag());
+ }
+
+ return $this->latest;
+ }
+
+ /**
+ * @param string $version
+ */
+ public function setLatest($version)
+ {
+ $this->latest = $version;
+ }
+
+ /**
+ * @return string|null
+ */
+ private function getVersionFromTag()
+ {
+ $contents = $this->fetchLatestRelease();
+ if (!$contents || !isset($contents->tag_name)) {
+ throw new \InvalidArgumentException('Unable to check for updates');
+ }
+ $this->setLatest($contents->tag_name);
+
+ return $this->getLatest();
+ }
+
+ /**
+ * Set to public to make testing easier.
+ *
+ * @return mixed
+ */
+ public function fetchLatestRelease()
+ {
+ $context = stream_context_create(array('http' => array('user_agent' => 'PsySH/' . Shell::VERSION)));
+
+ return json_decode(@file_get_contents(self::URL, false, $context));
+ }
+}