metatags

Caddy wikijs_metatags handler module

This Caddy module automatically inserts og:description and og:image meta tags to WikiJS pages, hence the name wikijs_metatags.

It only performs replacements if the tags are empty, and uses the default image if none can be found in page. If there are images on the page, the first one is used in the og:image meta tag. For description, only default one is used.

Note: This handler cannot perform replacements on compressed content. If your response comes from a proxied backend that supports compression, you will either have to decompress it in a response handler chain before this handler runs, or disable from the backend. One easy way to ask the backend to not compress the response is to set the Accept-Encoding header to identity, for example: header_up Accept-Encoding identity (in your Caddyfile, in the reverse_proxy block).

Module name: http.handlers.wikijs_metatags

Usage

Since this is a very niche plugin, I haven't bothered submitting it to the Caddy plugin registry. You can, however, use it directly in your docker compose file by referring to the image ghcr.io/sintan1729/caddy-wikijs-metatags:latest or :0 for sticking to the current version. The versioned releases are locked at the state when a version is released. The latest tag is built monthly, and whenever a new version of caddy is released.

JSON examples

Substring substitution:

{
  "handler": "wikijs_metatags",
  "default_description": "Foo",
  "default_image_path": "/Bar.jpg",
  "insert_topic": false,
  "topic_regex": "\/([^\/]+)\/[^\/]+$"
}

Caddyfile

This module has Caddyfile support. It registers the wikijs_metatags directive, by default to be after the standard encode directive. Make sure to change it with the order global option in case that is not suitable for your needs.

Syntax:

wikijs_metatags [<matcher>] {
	default_description <description>
	default_image_path <path>
	[insert_topic]
	[topic_regex <regex>]
}

• Here, default_description is a string, which will become the description if the page has none.
• The default_image_path can relative to the host, in which case hostname will be added automatically. It can also be a complete URL. In both cases, it must link to a .jpg, .png, .gif, or .webp image.
• If insert_topic is present, an attempt will be made to insert a topic after the description.
• If insert_topic is present, topic_regex will be used to extract the topic. It must match the URL being processed. The first capturing group will be used to get the topic. The above json example shows the regex that I use. My wiki page links look like https://<hostname>/<language>/<topic>/<pagename>, and the regex captures <topic> from it. Remember that the https:// prefix is not part of the matched URL string.

Limitation

Compressed responses (e.g. from an upstream proxy which gzipped the response body) will not be decoded before attempting to replace. To work around this, you may send the Accept-Encoding: identity request header to the upstream to tell it not to compress the response. For example:

      reverse_proxy localhost:8080 {
          header_up Accept-Encoding identity
      }

Acknowledgement

Much of the code has shamelessly been borrowed from https://github.com/caddyserver/replace-response.