[Emebed] Add Embed plugin and initial cleanup

plugins/Embed/EmbedHelper.php

@@ -0,0 +1,191 @@
+<?php
+
+// {{{ License
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+// }}}
+
+/**
+ * OembedPlugin implementation for GNU social
+ *
+ * @package   GNUsocial
+ *
+ * @author    Mikael Nordfeldth
+ * @author    hannes
+ * @author    Diogo Cordeiro <diogo@fc.up.pt>
+ * @author    Hugo Sales <hugo@hsal.es>
+ * @copyright 2019, 2021 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+
+namespace Plugin\Embed;
+
+use App\Core\Event;
+use App\Core\HTTPClient;
+use App\Core\Log;
+
+/**
+ * Utility class to wrap basic embed lookups.
+ *
+ * Denylisted hosts will use an alternate lookup method.
+ * Allowlisted hosts will use known embed API endpoints.
+ *
+ * Sites that provide discovery links will use them directly; a bug
+ * in use of discovery links with query strings is worked around.
+ *
+ * Others will fall back to oohembed (unless disabled).
+ * The API endpoint can be configured or disabled through config
+ * as 'oohembed'/'endpoint'.
+ *
+ * @copyright 2019, 2021 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+class EmbedHelper
+{
+    /**
+     * Perform or fake an oEmbed lookup for the given $url.
+     *
+     * Some known hosts are allowlisted with API endpoints where we
+     * know they exist but autodiscovery data isn't available.
+     *
+     * A few hosts are denylisted due to known problems with oohembed,
+     * in which case we'll look up the info another way and return
+     * equivalent data.
+     *
+     * Throws exceptions on failure.
+     *
+     * @param string $url
+     *
+     * @throws EmbedHelper_BadHtmlException
+     * @throws HTTP_Request2_Exception
+     *
+     * @return object
+     */
+    public static function getEmbed(string $url)
+    {
+        Log::info('Checking for remote URL metadata for ' . $url);
+
+        $metadata = new \stdClass();
+
+        if (Event::handle('GetRemoteUrlMetadata', [$url, &$metadata])) {
+            // If that event didn't return anything, try downloading the body and parse it
+
+            $response = HTTPClient::get($url);
+            $body     = $response->getBody();
+
+            // DOMDocument::loadHTML may throw warnings on unrecognized elements,
+            // and notices on unrecognized namespaces.
+            $old = error_reporting(error_reporting() & ~(E_WARNING | E_NOTICE));
+
+            // DOMDocument assumes ISO-8859-1 per HTML spec
+            // use UTF-8 if we find any evidence of that encoding
+            $utf8_evidence     = false;
+            $unicode_check_dom = new DOMDocument();
+            $ok                = $unicode_check_dom->loadHTML($body);
+            if (!$ok) {
+                throw new EmbedHelper_BadHtmlException();
+            }
+            $metaNodes = $unicode_check_dom->getElementsByTagName('meta');
+            foreach ($metaNodes as $metaNode) {
+                // case in-sensitive since Content-type and utf-8 can be written in many ways
+                if (stristr($metaNode->getAttribute('http-equiv'), 'content-type')
+                && stristr($metaNode->getAttribute('content'), 'utf-8')) {
+                    $utf8_evidence = true;
+                    break;
+                } elseif (stristr($metaNode->getAttribute('charset'), 'utf-8')) {
+                    $utf8_evidence = true;
+                    break;
+                }
+            }
+            unset($unicode_check_dom);
+
+            // The Content-Type HTTP response header overrides encoding metatags in DOM
+            if (stristr($response->getHeader('Content-Type'), 'utf-8')) {
+                $utf8_evidence = true;
+            }
+
+            // add utf-8 encoding prolog if we have reason to believe this is utf-8 content
+            // DOMDocument('1.0', 'UTF-8') does not work!
+            $utf8_tag = $utf8_evidence ? '<?xml encoding="utf-8" ?>' : '';
+
+            $dom = new DOMDocument();
+            $ok  = $dom->loadHTML($utf8_tag . $body);
+            unset($body);   // storing the DOM in memory is enough...
+            error_reporting($old);
+
+            if (!$ok) {
+                throw new EmbedHelper_BadHtmlException();
+            }
+
+            Event::handle('GetRemoteUrlMetadataFromDom', [$url, $dom, &$metadata]);
+        }
+
+        return self::normalize($metadata);
+    }
+
+    /**
+     * Normalize oEmbed format.
+     *
+     * @param stdClass $data
+     *
+     * @throws Exception
+     *
+     * @return object
+     */
+    public static function normalize(stdClass $data)
+    {
+        if (empty($data->type)) {
+            throw new Exception('Invalid oEmbed data: no type field.');
+        }
+        if ($data->type == 'image') {
+            // YFrog does this.
+            $data->type = 'photo';
+        }
+
+        if (isset($data->thumbnail_url)) {
+            if (!isset($data->thumbnail_width)) {
+                // !?!?!
+                $data->thumbnail_width  = Common::config('thumbnail', 'width');
+                $data->thumbnail_height = Common::config('thumbnail', 'height');
+            }
+        }
+
+        return $data;
+    }
+}
+
+class EmbedHelper_Exception extends \Exception
+{
+    public function __construct($message = '', $code = 0, $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+}
+
+class EmbedHelper_BadHtmlException extends EmbedHelper_Exception
+{
+    public function __construct($previous = null)
+    {
+        return parent::__construct('Bad HTML in discovery data.', 0, $previous);
+    }
+}
+
+class EmbedHelper_DiscoveryException extends EmbedHelper_Exception
+{
+    public function __construct($previous = null)
+    {
+        return parent::__construct('No oEmbed discovery data.', 0, $previous);
+    }
+}