Jekyll Mention Filter

mentions_filter.rb

#
# To install, drop this file into your _plugins directory and add the "html-pipeline" gem to your Gemfile.
#
# To use, apply like any other liquid filter.  e.g. {{ content | replace_mentions | xml_escape }}
#

require "html/pipeline"

module Jekyll
  module MentionFilter
    def replace_mentions(content)
      return content unless content.include?("@")
      src = mention_base(@context.registers[:site].config)

      if content.include? BODY_START_TAG
        head, opener, tail  = content.partition(OPENING_BODY_TAG_REGEX)
        body_content, *rest = tail.partition("</body>")

        return unless body_content =~ filter_regex

        processed_markup = filter_with_mention(src).call(body_content)[:output].to_s

        return String.new(head) << opener << processed_markup << rest.join
      else
        return unless content =~ filter_regex

        return filter_with_mention(src).call(content)[:output].to_s
      end
    end

    private

    GITHUB_DOT_COM = "https://github.com"
    BODY_START_TAG = "<body"

    OPENING_BODY_TAG_REGEX = %r!<body(.*?)>\s*!.freeze

    InvalidJekyllMentionConfig = Class.new(Jekyll::Errors::FatalException)

    # Public: Create or fetch the filter for the given {{src}} base URL.
    #
    # src - the base URL (e.g. https://github.com)
    #
    # Returns an HTML::Pipeline instance for the given base URL.
    def filter_with_mention(src)
      filters[src] ||= HTML::Pipeline.new([
        HTML::Pipeline::MentionFilter,
      ], :base_url => src, :username_pattern => mention_username_pattern)
    end

    def mention_username_pattern
      @mention_username_pattern ||= %r![\w][\w-]*!
    end

    # Public: Filters hash where the key is the mention base URL.
    # Effectively a cache.
    def filters
      @filters ||= {}
    end

    # Public: Calculate the base URL to use for mentioning.
    # The custom base URL can be defined in the config as
    # jekyll-mentions.base_url or jekyll-mentions, and must
    # be a valid URL (i.e. it must include a protocol and valid domain)
    # It should _not_ have a trailing slash.
    #
    # config - the hash-like configuration of the document's site
    #
    # Returns a URL to use as the base URL for mentions.
    # Defaults to the https://github.com.
    def mention_base(config = {})
      mention_config = config["jekyll-mentions"]
      case mention_config
      when nil, NilClass
        default_mention_base
      when String
        mention_config.to_s
      when Hash
        mention_config.fetch("base_url", default_mention_base)
      else
        raise InvalidJekyllMentionConfig,
              "Your jekyll-mentions config has to either be a string or a hash. " \
              "It's a #{mention_config.class} right now."
      end
    end

    def filter_regex
      @filter_regex ||=
        begin
          Regexp.new(
            HTML::Pipeline::MentionFilter::MentionPatterns[mention_username_pattern]
          )
        rescue TypeError
          %r!@\w+!
        end
    end

    def default_mention_base
      if !ENV["SSL"].to_s.empty? && !ENV["GITHUB_HOSTNAME"].to_s.empty?
        scheme = ENV["SSL"] == "true" ? "https://" : "http://"
        "#{scheme}#{ENV["GITHUB_HOSTNAME"].chomp("/")}"
      else
        GITHUB_DOT_COM
      end
    end
  end
end

Liquid::Template.register_filter(Jekyll::MentionFilter)