Changed frontmatter filtering to support YAML, JSON, TOML, and arbitrary languages

3 files changed, 35 insertions, 28 deletions

diff --git a/lib/banzai/filter/front_matter_filter.rb b/lib/banzai/filter/front_matter_filter.rb
new file mode 100644
index 00000000000..a27d18facd1
--- /dev/null
+++ b/lib/banzai/filter/front_matter_filter.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    class FrontMatterFilter < HTML::Pipeline::Filter
+      DELIM_LANG = {
+        '---' => 'yaml',
+        '+++' => 'toml',
+        ';;;' => 'json'
+      }.freeze
+
+      DELIM = Regexp.union(DELIM_LANG.keys)
+
+      PATTERN = %r{
+        \A(?:[^\r\n]*coding:[^\r\n]*)?         # optional encoding line
+        \s*
+        ^(?<delim>#{DELIM})[ \t]*(?<lang>\S*)  # opening front matter marker (optional language specifier)
+        \s*
+        ^(?<front_matter>.*?)                  # front matter (not greedy)
+        \s*
+        ^\k<delim>                             # closing front matter marker
+        \s*
+      }mx
+
+      def call
+        html.sub(PATTERN) do |_match|
+          lang = $~[:lang].presence || DELIM_LANG[$~[:delim]]
+
+          ["```#{lang}", $~[:front_matter], "```", "\n"].join("\n")
+        end
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/yaml_front_matter_filter.rb b/lib/banzai/filter/yaml_front_matter_filter.rb
deleted file mode 100644
index 295964dd75d..00000000000
--- a/lib/banzai/filter/yaml_front_matter_filter.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-# frozen_string_literal: true
-
-module Banzai
-  module Filter
-    class YamlFrontMatterFilter < HTML::Pipeline::Filter
-      DELIM = '---'.freeze
-
-      # Hat-tip to Middleman: https://git.io/v2e0z
-      PATTERN = %r{
-        \A(?:[^\r\n]*coding:[^\r\n]*\r?\n)?
-        (?<start>#{DELIM})[ ]*\r?\n
-        (?<frontmatter>.*?)[ ]*\r?\n?
-        ^(?<stop>#{DELIM})[ ]*\r?\n?
-        \r?\n?
-        (?<content>.*)
-      }mx.freeze
-
-      def call
-        match = PATTERN.match(html)
-
-        return html unless match
-
-        "```yaml\n#{match['frontmatter']}\n```\n\n#{match['content']}"
-      end
-    end
-  end
-end
diff --git a/lib/banzai/pipeline/pre_process_pipeline.rb b/lib/banzai/pipeline/pre_process_pipeline.rb
index c937f783180..4c2b4ca1665 100644
--- a/lib/banzai/pipeline/pre_process_pipeline.rb
+++ b/lib/banzai/pipeline/pre_process_pipeline.rb
@@ -5,7 +5,7 @@ module Banzai
     class PreProcessPipeline < BasePipeline
       def self.filters
         FilterArray[
-          Filter::YamlFrontMatterFilter,
+          Filter::FrontMatterFilter,
           Filter::BlockquoteFenceFilter,
         ]
       end