Add Gzip filter to compress html pages

Contributes to https://gitlab.com/gitlab-org/gitlab-docs/-/issues/879

3 files changed, 22 insertions, 0 deletions

diff --git a/Rules b/Rules
index 77998113..ccc5bf7c 100644
--- a/Rules
+++ b/Rules
@@ -100,6 +100,11 @@ compile '/**/*.md' do
     else
       layout "/#{item[:layout]}.*"
     end
+
+    if Nanoc::Helpers::Generic.is_omnibus?
+      filter :gzip
+      write ext: 'html.gz'
+    end
   else
     layout '/redirect.*'
   end
diff --git a/lib/filters/gzip.rb b/lib/filters/gzip.rb
new file mode 100644
index 00000000..446c86b9
--- /dev/null
+++ b/lib/filters/gzip.rb
@@ -0,0 +1,13 @@
+class GzipFilter < Nanoc::Filter
+  identifier :gzip
+
+  def run(content, params = {})
+    output = StringIO.new
+
+    gzip = Zlib::GzipWriter.new(output, Zlib::BEST_COMPRESSION)
+    gzip.write(content)
+    gzip.close
+
+    output.string
+  end
+end
diff --git a/lib/helpers/generic.rb b/lib/helpers/generic.rb
index 2bc27ea8..5e5ea01b 100644
--- a/lib/helpers/generic.rb
+++ b/lib/helpers/generic.rb
@@ -8,5 +8,9 @@ module Nanoc::Helpers
     def is_production?
       ENV['NANOC_ENV'] == 'production'
     end
+
+    def is_omnibus?
+      ENV['NANOC_ENV'] == 'omnibus'
+    end
   end
 end