class Rad::TextUtils::CustomMarkdown < Rad::TextUtils::Processor
  def process markdown, env
    markdown = github_flavoured_markdown markdown
    markdown = image_box markdown
    text = custom_markdown markdown
    
    call_next text, env
  end
  
  protected
    def custom_markdown markdown
      # BlueCloth doesn't apply inside of HTML tags, so we temporarilly replacing it
      markdown = markdown.gsub('<', 'HTML_BEGIN').gsub('>', 'HTML_END')

      markdown = markdown.gsub(" \n", "<br/>\n")

      text = BlueCloth.new(markdown).to_html

      text = text.gsub(/\A<.+?>/){"#{$&} "}.gsub(/<\/.+?>\Z/){" #{$&}"}

      text = text.gsub('HTML_BEGIN', '<').gsub('HTML_END', '>')

      text.gsub(/[\n]+/, "\n")
    end
  
    def github_flavoured_markdown markdown
      # Extract pre blocks
      extractions = {}
      markdown.gsub!(%r{<pre>.*?</pre>}m) do |match|
        md5 = Digest::MD5.hexdigest(match)
        extractions[md5] = match
        "{gfm-extraction-#{md5}}"
      end

      # prevent foo_bar_baz from ending up with an italic word in the middle
      markdown.gsub!(/(^(?! {4}|\t)\w+_\w+_\w[\w_]*)/) do |x|
        x.gsub('_', '\_') if x.split('').sort.to_s[0..1] == '__'
      end

      # in very clear cases, let newlines become <br /> tags
      markdown.gsub!(/^[\w\<\!][^\n]*\n+/) do |x|
        if x =~ /\>[\n\r]*/
          x
        else
          x =~ /\n{2}/ ? x : (x.strip!; x << " \n")
        end
      end

      # Insert pre block extractions
      markdown.gsub!(/\{gfm-extraction-([0-9a-f]{32})\}/) do
        "\n\n" + extractions[$1]
      end

      markdown
    end
    
    # !![img] => [![img_thumb]][img]
    def image_box markdown
      img_urls = {}
      markdown = markdown.gsub(/!!\[(.+?)\]/) do
        img_key = $1 || ''
        if url = markdown.scan(/\[#{img_key}\]:\s*([^\s]+)$/).first.try(:first)
          unless url =~ /\.[^\.]+\.[^\.]+$/ # image.png
            thumb_img_key = "#{img_key}_thumb"

            # building url with thumb (foo.png => foo.thumb.png)
            img_urls[thumb_img_key] = url.sub(/\.([^\.]+)$/){".thumb.#{$1}"}

            "[![][#{thumb_img_key}]][#{img_key}]"
          else # image.(icon|thumb|...).png
            img_key_full = "#{img_key}_full"

            # building url with thumb (foo.png => foo.thumb.png)
            img_urls[img_key_full] = url.sub(/\.([^\.]+)\.([^\.]+)$/){".#{$2}"}

            "[![][#{img_key}]][#{img_key_full}]"
          end
        else
          $& || ''
        end
      end

      unless img_urls.blank?
        markdown << "\n"
        markdown << img_urls.to_a.collect{|k, v| "[#{k}]: #{v}"}.join("\n")
      end

      markdown
    end
end