feat(how-tos): add kong_plugins meta tag

Extract the plugins used in the how-to and add a meta tag with them so
that we can filter them in Algolia

Author: fabianrbz

app/_plugins/blocks/entity_examples.rb

@@ -16,12 +16,17 @@ def render(context) # rubocop:disable Metrics/MethodLength
       config = config.merge('formats' => @page['tools']) unless config['formats']
 
       unless config['formats']
-        raise ArgumentError, "Missing key `tools` in metadata, or `formats` in entity_examples block on page #{@page['path']}"
+        raise ArgumentError,
+              "Missing key `tools` in metadata, or `formats` in entity_examples block on page #{@page['path']}"
       end
       unless config['formats'] == ['deck']
         raise ArgumentError, "entity_examples only supports deck, on page #{@page['path']}"
       end
 
+      @page['kong_plugins'] ||= []
+      kong_plugins = plugins(config)
+      @page['kong_plugins'].concat(kong_plugins) if kong_plugins.any?
+
       entity_examples_drop = Drops::EntityExamples.new(config:)
 
       template = File.read(entity_examples_drop.template)
@@ -32,12 +37,18 @@ def render(context) # rubocop:disable Metrics/MethodLength
       end
     rescue Psych::SyntaxError => e
       message = <<~STRING
-      On `#{@page['path']}`, the following {% entity_examples %} block contains a malformed yaml:
-      #{contents.strip.split("\n").each_with_index.map { |l, i| "#{i}: #{l}" }.join("\n")}
-      #{e.message}
+        On `#{@page['path']}`, the following {% entity_examples %} block contains a malformed yaml:
+        #{contents.strip.split("\n").each_with_index.map { |l, i| "#{i}: #{l}" }.join("\n")}
+        #{e.message}
       STRING
       raise ArgumentError.new(message)
     end
+
+    def plugins(config)
+      return [] unless config.dig('entities', 'plugins')
+
+      config['entities']['plugins'].map { |plugin| plugin['name'] }.compact
+    end
   end
 end
 

app/_plugins/hooks/post_process_html.rb

@@ -98,6 +98,48 @@ def process # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
   end
 end
 
+class KongPluginsMetaInjector
+  def initialize(page_or_doc)
+    @page_or_doc = page_or_doc
+  end
+
+  def process
+    return unless should_inject?
+
+    inject_meta_tag(build_meta_tag)
+  end
+
+  private
+
+  def should_inject?
+    kong_plugins&.any?
+  end
+
+  def kong_plugins
+    @kong_plugins ||= @page_or_doc.data.fetch('kong_plugins', []).uniq
+  end
+
+  def build_meta_tag
+    %(<meta name="algolia:kong_plugins" content="#{kong_plugins.join(', ')}">)
+  end
+
+  def inject_meta_tag(meta_tag)
+    doc = Nokogiri::HTML(@page_or_doc.output)
+    head = doc.at_css('head')
+
+    last_meta = head.css('meta').last
+
+    if last_meta
+      last_meta.add_next_sibling("\n  #{meta_tag}")
+    else
+      head.prepend_child("#{meta_tag}\n  ")
+    end
+
+    @page_or_doc.output = doc.to_html
+  end
+end
+
 Jekyll::Hooks.register [:documents, :pages], :post_render do |page_or_doc|
   AddLinksToHeadings.new(page_or_doc).process
+  KongPluginsMetaInjector.new(page_or_doc).process
 end