1 files changed, 109 insertions, 0 deletions
diff --git a/lib/kramdown/converter/commonmark.rb b/lib/kramdown/converter/commonmark.rb
new file mode 100644
index 00000000000..4abb34cc008
--- /dev/null
+++ b/lib/kramdown/converter/commonmark.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+module Kramdown
+  module Converter
+    # Overrides the base Kramdown converter to add any special
+    # behaviour for CommonMark.
+    #
+    # Currently we support an option `html_tables` that outputs
+    # an HTML table instead of a Markdown table.  This is to
+    # support possibly being given complex tables, such as from ADF.
+    #
+    # Note: this is only an initial implementation.  Currently don't
+    # strip out IALs or other specific kramdown syntax.
+    class Commonmark < ::Kramdown::Converter::Kramdown
+      # replaces the ^ used in kramdown.  This forces the current
+      # block to end, so that a different list or codeblock can be
+      # started. https://kramdown.gettalong.org/syntax.html#eob-marker
+      END_OF_BLOCK = '<!-- -->'
+
+      def convert(el, opts = { indent: 0 })
+        res = super
+
+        if [:ul, :dl, :ol, :codeblock].include?(el.type) && opts[:next] &&
+          ([el.type, :codeblock].include?(opts[:next].type) ||
+            (opts[:next].type == :blank && opts[:nnext] &&
+              [el.type, :codeblock].include?(opts[:nnext].type)))
+          # replace the end of block character
+          res.sub!(/\^\n\n\z/m, "#{END_OF_BLOCK}\n\n")
+        end
+
+        res
+      end
+
+      def convert_codeblock(el, _opts)
+        # Although tildes are supported in CommonMark, backticks are more common
+        "```#{el.options[:lang]}\n" +
+          el.value.split(/\n/).map {|l| l.empty? ? "" : "#{l}" }.join("\n") +
+          "\n```\n\n"
+      end
+
+      def convert_li(el, opts)
+        res = super
+
+        if el.children.first && el.children.first.type == :p && !el.children.first.options[:transparent]
+          if el.children.size == 1 && @stack.last.children.last == el &&
+            (@stack.last.children.any? {|c| c.children.first.type != :p } || @stack.last.children.size == 1)
+            # replace the end of block character
+            res.sub!(/\^\n\z/m, "#{END_OF_BLOCK}\n")
+          end
+        end
+
+        res
+      end
+
+      def convert_table(el, opts)
+        return super unless @options[:html_tables]
+
+        opts[:alignment] = el.options[:alignment]
+        result = inner(el, opts)
+
+        "<table>\n#{result}</table>\n\n"
+      end
+
+      def convert_thead(el, opts)
+        return super unless @options[:html_tables]
+
+        "<thead>\n#{inner(el, opts)}</thead>\n"
+      end
+
+      def convert_tbody(el, opts)
+        return super unless @options[:html_tables]
+
+        "<tbody>\n#{inner(el, opts)}</tbody>\n"
+      end
+
+      def convert_tfoot(el, opts)
+        return super unless @options[:html_tables]
+
+        "<tfoot>\n#{inner(el, opts)}</tfoot>\n"
+      end
+
+      def convert_tr(el, opts)
+        return super unless @options[:html_tables]
+
+        "<tr>\n#{el.children.map {|c| convert(c, opts) }.join}</tr>\n"
+      end
+
+      def convert_td(el, opts)
+        return super unless @options[:html_tables]
+
+        # We need to add two linefeeds in order for any inner text to
+        # be processed as markdown.  The HTML block must be "closed",
+        # as referenced in the CommonMark spec
+        # @see https://spec.commonmark.org/0.29/#html-blocks
+        "<td>\n\n#{inner(el, opts)}</td>\n"
+      end
+
+      def convert_th(el, opts)
+        return super unless @options[:html_tables]
+
+        # We need to add two linefeeds in order for any inner text to
+        # be processed as markdown.  The HTML block must be "closed",
+        # as referenced in the CommonMark spec
+        # @see https://spec.commonmark.org/0.29/#html-blocks
+        "<th>\n\n#{inner(el, opts)}</th>\n"
+      end
+    end
+  end
+end