module Monad
  module Converters
    class Markdown
      class RedcarpetParser

        module CommonMethods
          def add_code_tags(code, lang)
            code = code.sub(/<pre>/, "<pre><code class=\"#{lang} language-#{lang}\" data-lang=\"#{lang}\">")
            code = code.sub(/<\/pre>/,"</code></pre>")
          end
        end

        module WithPygments
          include CommonMethods
          def block_code(code, lang)
            require 'pygments'
            lang = lang && lang.split.first || "text"
            output = add_code_tags(
              Pygments.highlight(code, :lexer => lang, :options => { :encoding => 'utf-8' }),
              lang
            )
          end
        end

        module WithoutPygments
          require 'cgi'

          include CommonMethods

          def code_wrap(code)
            "<div class=\"highlight\"><pre>#{CGI::escapeHTML(code)}</pre></div>"
          end

          def block_code(code, lang)
            lang = lang && lang.split.first || "text"
            output = add_code_tags(code_wrap(code), lang)
          end
        end

        def initialize(config)
          require 'redcarpet'
          @config = config
          @redcarpet_extensions = {}
          @config['redcarpet']['extensions'].each { |e| @redcarpet_extensions[e.to_sym] = true }

          @renderer ||= if @config['pygments']
                          Class.new(Redcarpet::Render::HTML) do
                            include WithPygments
                          end
                        else
                          Class.new(Redcarpet::Render::HTML) do
                            include WithoutPygments
                          end
                        end
        rescue LoadError
          STDERR.puts 'You are missing a library required for Markdown. Please run:'
          STDERR.puts '  $ [sudo] gem install redcarpet'
          raise FatalException.new("Missing dependency: redcarpet")
        end

        def convert(content)
          @redcarpet_extensions[:fenced_code_blocks] = !@redcarpet_extensions[:no_fenced_code_blocks]
          @renderer.send :include, Redcarpet::Render::SmartyPants if @redcarpet_extensions[:smart]
          markdown = Redcarpet::Markdown.new(@renderer.new(@redcarpet_extensions), @redcarpet_extensions)
          markdown.render(content)
        end
      end
    end
  end
end