module Banzai
  module Filter
    class MarkdownFilter < HTML::Pipeline::TextFilter
      def initialize(text, context = nil, result = nil)
        super text, context, result
        @text = @text.delete "\r"
      end

      def call
        html = self.class.renderer.render(@text)
        html.rstrip!
        html
      end

      def self.renderer
        @renderer ||= begin
          renderer = Redcarpet::Render::HTML.new
          Redcarpet::Markdown.new(renderer, redcarpet_options)
        end
      end

      def self.redcarpet_options
        # https://github.com/vmg/redcarpet#and-its-like-really-simple-to-use
        @redcarpet_options ||= {
          fenced_code_blocks:  true,
          footnotes:           true,
          lax_spacing:         true,
          no_intra_emphasis:   true,
          space_after_headers: true,
          strikethrough:       true,
          superscript:         true,
          tables:              true
        }.freeze
      end

      private_class_method :redcarpet_options
    end
  end
end