Plugin for Tiny Tiny RSS
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README.md

#ff_FeedCleaner

ToC

Introduction

This is a plugin for Tiny Tiny RSS. It allows to modify the content of feeds before Tiny Tiny RSS parses them. Currently, the emphasis is on applying regular expressions to the feed data.

The Tiny Tiny RSS version must be 1.8 or later.

Installation

This should be done on the command line

$ cd /var/www/ttrss/plugins.local
$ git clone https://github.com/wltb/ff_feedcleaner

Alternatively, you can download the zip archive and unzip it into the plugins.local (or plugins) subdirectory of your Tiny Tiny RSS installation. Note that the directory containing init.php must be named ff_feedcleaner, otherwise Tiny Tiny RSS won't load the plugin, so you may have to rename it after the unzipping.

After that, the plugin must be enabled in the preferences of Tiny Tiny RSS.

Updating

This is easiest with a git installation, simply use a git pull. With a zip installation, the old directory must be overwritten with the a fresh download. In neither case any stored configurations will be overwritten since these are stored in the database.

Configuration

In the preferences, you'll find a new tab called FeedCleaner which contains two panes. The pane Preferences is opened by default, and contains a large text field which is used to enter/modify the configuration data, and a checkbox to turn extended logging on and off. The other pane Show Diff can be used to preview the results on the manipulation and is described further below.

Basically, the configuration data consists of an unnamed JSON array that contains some unnamed JSON objects. Use the Save button to store it.

An example configuration looks like this:

[
	{
		"URL_re": "#http://(prospector\\.freeforums\\.org|www\\.iswintercoming\\.com)/feed\\.php#",
		"type": "regex",
		"pattern": "/sid=[0-9a-f]{32}/",
		"replacement": ""
	},
	{
		"URL": "newsfeed.zeit.de",
		"type": "xpath_regex",
		"xpath": "//item/link",
		"pattern": "#$#",
		"replacement": "/komplettansicht"
	},
	{
		"URL": "rss.nytimes.com",
		"type": "xpath_regex",
		"xpath": "//item/atom:link/@href|//item/link",
		"pattern": "/$/",
		"replacement": "&pagewanted=all"
	},
	{
		"URL": "faz.net",
		"type": "link_regex",
		"pattern": "#$#",
		"replacement": "?printPagedArticle=true"
	}
]

Each object must contain a type and a URL or a URL_re key.

The type key specifies which kind of manipulation should be performed on the feed data. The implemented types are described below.

The URL and URL_re values are used to select the feeds on which the associated manipulation should be applied. To match, the URL value must be a substring of the feed URL. The URL_re value must be a regular expression in the pcre module style which is matched against the feed URL with the preg_match function.

If an object contains both a URL and a URL_re key, the URL_re key is ignored. Generally a URL_re key should only be used in specific cases. In the example above, the URL_re key is used so that the pattern can be applied to more then one domain.

It should be noted that the configuration is always UTF-8 encoded. This may cause problems if the regular expressions contain non-ASCII characters, and the feed encoding is not UTF-8. You may then want to convert the feed encoding beforehand with type uft-8.

Type regex

For this type, two additional keys must be specified: pattern and replacement. Their values are used to manipulate the feed data with the preg_replace function. The semantic of their values is explained on the linked page, in particular, pattern is a regular expression.

Type xpath_regex

This type is useful because it allows a more careful selection of the text that should be altered with a XPath expression. The XPath must be specified with the key xpath. The other keys that are needed are pattern and replacement. Their meaning is the same as in the regex type.

With this type, some subtleties have to be regarded.

  1. When the feed is loaded, all five predefined entities are converted to their real values. When saving, only &, <, > (and in attributes, also ") are converted back to &amp;, &lt;, &gt; (and &quot;), respectively.
  2. On all text nodes that are gathered with the XPath, the regular expression with pattern and replacement is directly applied. For all other node types, the regular expression is applied to all their children that are text nodes.

Namespaces

For feeds with default namespaces (e.g. Atom and RDF documents), querying with xpaths was possible, but a bit of a pain. In order to ease this, support for namespaces was added. The software tries to detect if the document has one of the following default namespaces

and if it does, registers it under the prefix DNS (Default Name Space). Xpath queries then simply have to be prefixed, e.g. to query for the feed entries in an Atom feed, the query string can be "//DNS:feed//DNS:entry".

If more namespaces are needed, or the automatic detection gets it wrong, you can register namespaces manually. To do so, simply put a namespaces entry in the configuration object:

{
	"URL" : ,
	"type" : "xpath_regex",
	
	"namespaces" : {"pre1": "uri1", "pre2": "uri2"}
}

The uri entries should be the namespace URIs, and the pre entries are the prefixes to be used in the path queries.

If the namespaces key is present, the automatic namespace detection is disabled.

Important: Since this plugin uses the DOMXPath object that is constructed by the FeedParser class of Tiny Tiny RSS, there are already some registered namespaces, and you should not override their prefixes. Check the definition of the FeedParser class for details.

Type link_regex

This type allows an easy manipulation of the links that Tiny Tiny RSS extracts for the feed items. The only keys needed beside the obligatory ones are pattern and replacement, which have the same meaning as in the regex case. But here, they are applied to the links only, and the results are stored so that Tiny Tiny RSS will choose them as the items links.

A warning: This type very much relies on information about Tiny Tiny RSS'es implementation details, and may break if they change. It is however highly unlikely that a change will make this type of manipulation impossible (or that there will be any change at all – the relevant code has been stable for nearly four years now), and I will try my best to quickly adapt to any change.

Examples

We explain what the entries in the given example configuration do.

In the entry with the URL_re key, for any feed whose URL contains http://www.iswintercoming.com/feed.php or http://prospector.freeforums.org/feed.php, expressions like sid=a7595fe6a719361152bb96f8a0bd48b5 (a sid= followed by 32 hexadecimal digits) are removed from the feed data.

The other three entries are useful in conjunction with af_feedmod. They amend the article links such that they point to a web page with the full article content, so that it can be fetched instead of just a segment. It is instructive to compare the first two objects with their regex cousins that were featured in an earlier version of this document.

[
	{
		"URL": "newsfeed.zeit.de",
		"type": "regex",
		"pattern": "#(<link>http://www\\.zeit\\.de/.+?)(</link>)#",
		"replacement": "$1/komplettansicht$2"
	},
	{
		"URL": "rss.nytimes.com",
		"type": "regex",
		"pattern": "#(<atom:link href=\"http://www.nytimes.com/[^\"]+?)(\")#",
		"replacement": "$1&amp;pagewanted=all$2"
	}
]

While these do (roughly) the same, the regular expressions for the xpath_regex objects are clearly more elegant, at the expense of finding a nice XPath, of course. In the NY Times objects, we also can see the different ways of inserting a "&amp;" into the feed. In the regex case, this has to be done literally, with the xpath_regex, there must be a "&" in the replacement value.

For the object modifying faz.net feeds, we see that the link_regex type works without the need for finding the right xpath, and so combines the best features of the other two types. Since this type also uses DOM functions, the same rules for insertion of entities as for the xpath_regex type apply.

Type utf-8

This type converts the feed data encoding to UTF-8.

Preview of modifications

The other pane titled Show Diff can be used to preview the changes made by this plugin. Simply enter the feed URL in the text box at the very top and click the button. A diff of the before and after will show up in the larger text box. Here is a screenshot for the faz.net modification:

Show Diff

The config used for the feed modification is not the one stored in the DB, but the one displayed under the Preferences pane. This is useful for trying out new modifications without interfering with the actual fetching, but the text must be valid JSON then.

This feature is still a little rough around the edges, e.g. there may be problems for feeds with encoding other then utf-8, or when the original feed can not be parsed, but the modified one can.

Some technical details: Currently, the unix diff CLI tool is used, so on machines without it, this will not work. The right hand side (marked with + in the screenshot) is the modified feed, and the left hand side the original one. The diff command used is defined in the class constant diff_cmd and can be changed for more context etc. The preview does not load any other plugins, so the actual feed parsed by Tiny Tiny RSS may have other modifications besides the one shown in the preview.

Extended Logging

Extended logging is enabled by setting the corresponding checkbox in the preferences tab. Regardless of this setting, errors are always logged. The log entries go into what you have defined in LOG_DESTINATION in Tiny Tiny RSSes config.php.

If you enable extended logging, the activity of the plugin will be reported in great detail. In particular, if you see no output at all, none of your objects in the configuration matched any of your subscribed feeds.