<?php
/**
* This file is part of RSS-Bridge, a PHP project capable of generating RSS and
* Atom feeds for websites that don't have one.
*
* For the full license information, please view the UNLICENSE file distributed
* with this source code.
*
* @package Core
* @license http://unlicense.org/ UNLICENSE
* @link https://github.com/rss-bridge/rss-bridge
*/
/**
* An abstract class for bridges that need to transform existing RSS or Atom
* feeds.
*
* This class extends {@see BridgeAbstract} with functions to extract contents
* from existing RSS or Atom feeds. Bridges that need to transform existing feeds
* should inherit from this class instead of {@see BridgeAbstract}.
*
* Bridges that extend this class don't need to concern themselves with getting
* contents from existing feeds, but can focus on adding additional contents
* (i.e. by downloading additional data), filtering or just transforming a feed
* into another format.
*
* @link http://www.rssboard.org/rss-0-9-1 RSS 0.91 Specification
* @link http://web.resource.org/rss/1.0/spec RDF Site Summary (RSS) 1.0
* @link http://www.rssboard.org/rss-specification RSS 2.0 Specification
* @link https://tools.ietf.org/html/rfc4287 The Atom Syndication Format
*
* @todo The parsing functions should all be private. This class is complicated
* enough without having to consider children overriding functions.
*/
abstract class FeedExpander extends BridgeAbstract {
/** Indicates an RSS 1.0 feed */
const FEED_TYPE_RSS_1_0 = 'RSS_1_0';
/** Indicates an RSS 2.0 feed */
const FEED_TYPE_RSS_2_0 = 'RSS_2_0';
/** Indicates an Atom 1.0 feed */
const FEED_TYPE_ATOM_1_0 = 'ATOM_1_0';
/**
* Holds the title of the current feed
*
* @var string
*/
private $title;
/**
* Holds the URI of the feed
*
* @var string
*/
private $uri;
/**
* Holds the feed type during internal operations.
*
* @var string
*/
private $feedType;
/**
* Collects data from an existing feed.
*
* Children should call this function in {@see BridgeInterface::collectData()}
* to extract a feed.
*
* @param string $url URL to the feed.
* @param int $maxItems Maximum number of items to collect from the feed
* (`-1`: no limit).
* @return self
*/
public function collectExpandableDatas($url, $maxItems = -1){
if(empty($url)) {
returnServerError('There is no $url for this RSS expander');
}
Debug::log('Loading from ' . $url);
/* Notice we do not use cache here on purpose:
* we want a fresh view of the RSS stream each time
*/
$content = getContents($url)
or returnServerError('Could not request ' . $url);
$rssContent = simplexml_load_string(trim($content));
Debug::log('Detecting feed format/version');
switch(true) {
case isset($rssContent->item[0]):
Debug::log('Detected RSS 1.0 format');
$this->feedType = self::FEED_TYPE_RSS_1_0;
break;
case isset($rssContent->channel[0]):
Debug::log('Detected RSS 0.9x or 2.0 format');
$this->feedType = self::FEED_TYPE_RSS_2_0;
break;
case isset($rssContent->entry[0]):
Debug::log('Detected ATOM format');
$this->feedType = self::FEED_TYPE_ATOM_1_0;
break;
default:
Debug::log('Unknown feed format/version');
returnServerError('The feed format is unknown!');
break;
}
Debug::log('Calling function "collect_' . $this->feedType . '_data"');
$this->{'collect_' . $this->feedType . '_data'}($rssContent, $maxItems);
return $this;
}
/**
* Collect data from a RSS 1.0 compatible feed
*
* @link http://web.resource.org/rss/1.0/spec RDF Site Summary (RSS) 1.0
*
* @param string $rssContent The RSS content
* @param int $maxItems Maximum number of items to collect from the feed
* (`-1`: no limit).
* @return void
*
* @todo Instead of passing $maxItems to all functions, just add all items
* and remove excessive items later.
*/
protected function collect_RSS_1_0_data($rssContent, $maxItems){
$this->load_RSS_2_0_feed_data($rssContent->channel[0]);
foreach($rssContent->item as $item) {
Debug::log('parsing item ' . var_export($item, true));
$tmp_item = $this->parseItem($item);
if (!empty($tmp_item)) {
$this->items[] = $tmp_item;
}
if($maxItems !== -1 && count($this->items) >= $maxItems) break;
}
}
/**
* Collect data from a RSS 2.0 compatible feed
*
* @link http://www.rssboard.org/rss-specification RSS 2.0 Specification
*
* @param object $rssContent The RSS content
* @param int $maxItems Maximum number of items to collect from the feed
* (`-1`: no limit).
* @return void
*
* @todo Instead of passing $maxItems to all functions, just add all items
* and remove excessive items later.
*/
protected function collect_RSS_2_0_data($rssContent, $maxItems){
$rssContent = $rssContent->channel[0];
Debug::log('RSS content is ===========\n'
. var_export($rssContent, true)
. '===========');
$this->load_RSS_2_0_feed_data($rssContent);
foreach($rssContent->item as $item) {
Debug::log('parsing item ' . var_export($item, true));
$tmp_item = $this->parseItem($item);
if (!empty($tmp_item)) {
$this->items[] = $tmp_item;
}
if($maxItems !== -1 && count($this->items) >= $maxItems) break;
}
}
/**
* Collect data from a Atom 1.0 compatible feed
*
* @link https://tools.ietf.org/html/rfc4287 The Atom Syndication Format
*
* @param object $content The Atom content
* @param int $maxItems Maximum number of items to collect from the feed
* (`-1`: no limit).
* @return void
*
* @todo Instead of passing $maxItems to all functions, just add all items
* and remove excessive items later.
*/
protected function collect_ATOM_1_0_data($content, $maxItems){
$this->load_ATOM_feed_data($content);
foreach($content->entry as $item) {
Debug::log('parsing item ' . var_export($item, true));
$tmp_item = $this->parseItem($item);
if (!empty($tmp_item)) {
$this->items[] = $tmp_item;
}
if($maxItems !== -1 && count($this->items) >= $maxItems) break;
}
}
/**
* Convert RSS 2.0 time to timestamp
*
* @param object $item A feed item
* @return int The timestamp
*/
protected function RSS_2_0_time_to_timestamp($item){
return DateTime::createFromFormat('D, d M Y H:i:s e', $item->pubDate)->getTimestamp();
}
/**
* Load RSS 2.0 feed data into RSS-Bridge
*
* @param object $rssContent The RSS content
* @return void
*
* @todo set title, link, description, language, and so on
*/
protected function load_RSS_2_0_feed_data($rssContent){
$this->title = trim((string)$rssContent->title);
$this->uri = trim((string)$rssContent->link);
}
/**
* Load Atom feed data into RSS-Bridge
*
* @param object $content The Atom content
* @return void
*/
protected function load_ATOM_feed_data($content){
$this->title = (string)$content->title;
// Find best link (only one, or first of 'alternate')
if(!isset($content->link)) {
$this->uri = '';
} elseif (count($content->link) === 1) {
$this->uri = (string)$content->link[0]['href'];
} else {
$this->uri = '';
foreach($content->link as $link) {
if(strtolower($link['rel']) === 'alternate') {
$this->uri = (string)$link['href'];
break;
}
}
}
}
/**
* Parse the contents of a single Atom feed item into a RSS-Bridge item for
* further transformation.
*
* @param object $feedItem A single feed item
* @return object The RSS-Bridge item
*
* @todo To reduce confusion, the RSS-Bridge item should maybe have a class
* of its own?
*/
protected function parseATOMItem($feedItem){
// Some ATOM entries also contain RSS 2.0 fields
$item = $this->parseRSS_2_0_Item($feedItem);
if(isset($feedItem->id)) $item['uri'] = (string)$feedItem->id;
if(isset($feedItem->title)) $item['title'] = (string)$feedItem->title;
if(isset($feedItem->updated)) $item['timestamp'] = strtotime((string)$feedItem->updated);
if(isset($feedItem->author)) $item['author'] = (string)$feedItem->author->name;
if(isset($feedItem->content)) $item['content'] = (string)$feedItem->content;
//When "link" field is present, URL is more reliable than "id" field
if (count($feedItem->link) === 1) {
$this->uri = (string)$feedItem->link[0]['href'];
} else {
foreach($feedItem->link as $link) {
if(strtolower($link['rel']) === 'alternate') {
$item['uri'] = (string)$link['href'];
break;
}
}
}
return $item;
}
/**
* Parse the contents of a single RSS 0.91 feed item into a RSS-Bridge item
* for further transformation.
*
* @param object $feedItem A single feed item
* @return object The RSS-Bridge item
*
* @todo To reduce confusion, the RSS-Bridge item should maybe have a class
* of its own?
*/
protected function parseRSS_0_9_1_Item($feedItem){
$item = array();
if(isset($feedItem->link)) $item['uri'] = (string)$feedItem->link;
if(isset($feedItem->title)) $item['title'] = (string)$feedItem->title;
// rss 0.91 doesn't support timestamps
// rss 0.91 doesn't support authors
// rss 0.91 doesn't support enclosures
if(isset($feedItem->description)) $item['content'] = (string)$feedItem->description;
return $item;
}
/**
* Parse the contents of a single RSS 1.0 feed item into a RSS-Bridge item
* for further transformation.
*
* @param object $feedItem A single feed item
* @return object The RSS-Bridge item
*
* @todo To reduce confusion, the RSS-Bridge item should maybe have a class
* of its own?
*/
protected function parseRSS_1_0_Item($feedItem){
// 1.0 adds optional elements around the 0.91 standard
$item = $this->parseRSS_0_9_1_Item($feedItem);
$namespaces = $feedItem->getNamespaces(true);
if(isset($namespaces['dc'])) {
$dc = $feedItem->children($namespaces['dc']);
if(isset($dc->date)) $item['timestamp'] = strtotime((string)$dc->date);
if(isset($dc->creator)) $item['author'] = (string)$dc->creator;
}
return $item;
}
/**
* Parse the contents of a single RSS 2.0 feed item into a RSS-Bridge item
* for further transformation.
*
* @param object $feedItem A single feed item
* @return object The RSS-Bridge item
*
* @todo To reduce confusion, the RSS-Bridge item should maybe have a class
* of its own?
*/
protected function parseRSS_2_0_Item($feedItem){
// Primary data is compatible to 0.91 with some additional data
$item = $this->parseRSS_0_9_1_Item($feedItem);
$namespaces = $feedItem->getNamespaces(true);
if(isset($namespaces['dc'])) $dc = $feedItem->children($namespaces['dc']);
if(isset($namespaces['media'])) $media = $feedItem->children($namespaces['media']);
if(isset($feedItem->guid)) {
foreach($feedItem->guid->attributes() as $attribute => $value) {
if($attribute === 'isPermaLink'
&& ($value === 'true' || (
filter_var($feedItem->guid, FILTER_VALIDATE_URL)
&& !filter_var($item['uri'], FILTER_VALIDATE_URL)
)
)
) {
$item['uri'] = (string)$feedItem->guid;
break;
}
}
}
if(isset($feedItem->pubDate)) {
$item['timestamp'] = strtotime((string)$feedItem->pubDate);
} elseif(isset($dc->date)) {
$item['timestamp'] = strtotime((string)$dc->date);
}
if(isset($feedItem->author)) {
$item['author'] = (string)$feedItem->author;
} elseif (isset($feedItem->creator)) {
$item['author'] = (string)$feedItem->creator;
} elseif(isset($dc->creator)) {
$item['author'] = (string)$dc->creator;
} elseif(isset($media->credit)) {
$item['author'] = (string)$media->credit;
}
if(isset($feedItem->enclosure) && !empty($feedItem->enclosure['url'])) {
$item['enclosures'] = array((string)$feedItem->enclosure['url']);
}
return $item;
}
/**
* Parse the contents of a single feed item, depending on the current feed
* type, into a RSS-Bridge item.
*
* @param object $item The current feed item
* @return object A RSS-Bridge item, with (hopefully) the whole content
*/
protected function parseItem($item){
switch($this->feedType) {
case self::FEED_TYPE_RSS_1_0:
return $this->parseRSS_1_0_Item($item);
break;
case self::FEED_TYPE_RSS_2_0:
return $this->parseRSS_2_0_Item($item);
break;
case self::FEED_TYPE_ATOM_1_0:
return $this->parseATOMItem($item);
break;
default: returnClientError('Unknown version ' . $this->getInput('version') . '!');
}
}
/** {@inheritdoc} */
public function getURI(){
return !empty($this->uri) ? $this->uri : parent::getURI();
}
/** {@inheritdoc} */
public function getName(){
return !empty($this->title) ? $this->title : parent::getName();
}
/** {@inheritdoc} */
public function getIcon(){
return !empty($this->icon) ? $this->icon : parent::getIcon();
}
}