discourse/lib/email/styles.rb

#
# HTML emails don't support CSS, so we can use nokogiri to inline attributes based on
# matchers.
#
module Email
  class Styles
    @@plugin_callbacks = []

    attr_accessor :fragment

    delegate :css, to: :fragment

    def initialize(html, opts=nil)
      @html = html
      @opts = opts || {}
      @fragment = Nokogiri::HTML.fragment(@html)
    end

    def self.register_plugin_style(&block)
      @@plugin_callbacks.push(block)
    end

    def add_styles(node, new_styles)
      existing = node['style']
      if existing.present?
        # merge styles
        node['style'] = "#{new_styles}; #{existing}"
      else
        node['style'] = new_styles
      end
    end

    def format_basic
      uri = URI(Discourse.base_url)

      # images
      @fragment.css('img').each do |img|
        next if img['class'] == 'site-logo'

        if img['class'] == "emoji" || img['src'] =~ /(plugins|images)\/emoji/
          img['width'] = 20
          img['height'] = 20
        else
          # use dimensions of original iPhone screen for 'too big, let device rescale'
          if img['width'].to_i > 320 or img['height'].to_i > 480
            img['width'] = 'auto'
            img['height'] = 'auto'
          end
        end

        # ensure all urls are absolute
        if img['src'] =~ /^\/[^\/]/
          img['src'] = "#{Discourse.base_url}#{img['src']}"
        end

        # ensure no schemaless urls
        if img['src'] && img['src'].starts_with?("//")
          img['src'] = "#{uri.scheme}:#{img['src']}"
        end
      end

      # add max-width to big images
      big_images = @fragment.css('img[width="auto"][height="auto"]') -
                   @fragment.css('aside.onebox img') -
                   @fragment.css('img.site-logo, img.emoji')
      big_images.each do |img|
        add_styles(img, 'max-width: 100%;') if img['style'] !~ /max-width/
      end

      # attachments
      @fragment.css('a.attachment').each do |a|
        # ensure all urls are absolute
        if a['href'] =~ /^\/[^\/]/
          a['href'] = "#{Discourse.base_url}#{a['href']}"
        end

        # ensure no schemaless urls
        if a['href'] && a['href'].starts_with?("//")
          a['href'] = "#{uri.scheme}:#{a['href']}"
        end
      end
    end

    def format_notification
      style('.previous-discussion', 'font-size: 17px; color: #444; margin-bottom:10px;')
      style('.notification-date', "text-align:right;color:#999999;padding-right:5px;font-family:'lucida grande',tahoma,verdana,arial,sans-serif;font-size:11px")
      style('.username', "font-size:13px;font-family:'lucida grande',tahoma,verdana,arial,sans-serif;color:#3b5998;text-decoration:none;font-weight:bold")
      style('.user-title', "font-size:13px;font-family:'lucida grande',tahoma,verdana,arial,sans-serif;text-decoration:none;margin-left:7px;color: #999;")
      style('.user-name', "font-size:13px;font-family:'lucida grande',tahoma,verdana,arial,sans-serif;text-decoration:none;margin-left:7px;color: #3b5998;font-weight:normal;")
      style('.post-wrapper', "margin-bottom:25px;")
      style('.user-avatar', 'vertical-align:top;width:55px;')
      style('.user-avatar img', nil, width: '45', height: '45')
      style('hr', 'background-color: #ddd; height: 1px; border: 1px;')
      style('.rtl', 'direction: rtl;')
      style('td.body', 'padding-top:5px;', colspan: "2")
      style('.whisper td.body', 'font-style: italic; color: #9c9c9c;')
      style('.lightbox-wrapper .meta', 'display: none')
      correct_first_body_margin
      correct_footer_style
      reset_tables
      onebox_styles
      plugin_styles
    end

    def onebox_styles
      # Links to other topics
      style('aside.quote', 'border-left: 5px solid #e9e9e9; background-color: #f8f8f8; padding: 12px 25px 2px 12px; margin-bottom: 10px;')
      style('aside.quote blockquote', 'border: 0px; padding: 0; margin: 7px 0; background-color: clear;')
      style('aside.quote blockquote > p', 'padding: 0;')
      style('aside.quote div.info-line', 'color: #666; margin: 10px 0')
      style('aside.quote .avatar', 'margin-right: 5px; width:20px; height:20px')

      style('blockquote', 'border-left: 5px solid #e9e9e9; background-color: #f8f8f8; margin: 0;')
      style('blockquote > p', 'padding: 1em;')

      # Oneboxes
      style('aside.onebox', "padding: 12px 25px 2px 12px; border-left: 5px solid #bebebe; background: #eee; margin-bottom: 10px;")
      style('aside.onebox img', "max-height: 80%; max-width: 25%; height: auto; float: left; margin-right: 10px; margin-bottom: 10px")
      style('aside.onebox h3', "border-bottom: 0")
      style('aside.onebox .source', "margin-bottom: 8px")
      style('aside.onebox .source a[href]', "color: #333; font-weight: normal")
      style('aside.clearfix', "clear: both")

      # Finally, convert all `aside` tags to `div`s
      @fragment.css('aside, article, header').each do |n|
        n.name = "div"
      end

      # iframes can't go in emails, so replace them with clickable links
      @fragment.css('iframe').each do |i|
        begin
          # sometimes, iframes are blacklisted...
          if i["src"].blank?
            i.remove
            next
          end

          src_uri = URI(i['src'])
          # If an iframe is protocol relative, use SSL when displaying it
          display_src = "#{src_uri.scheme || 'https'}://#{src_uri.host}#{src_uri.path}#{src_uri.query.nil? ? '' : '?' + src_uri.query}#{src_uri.fragment.nil? ? '' : '#' + src_uri.fragment}"
          i.replace "<p><a href='#{src_uri.to_s}'>#{CGI.escapeHTML(display_src)}</a><p>"
        rescue URI::InvalidURIError
          # If the URL is weird, remove the iframe
          i.remove
        end
      end
    end

    def format_html
      style('h4', 'color: #222;')
      style('h3', 'margin: 15px 0 20px 0;')
      style('hr', 'background-color: #ddd; height: 1px; border: 1px;')
      style('a', 'text-decoration: none; font-weight: bold; color: #006699;')
      style('ul', 'margin: 0 0 0 10px; padding: 0 0 0 20px;')
      style('li', 'padding-bottom: 10px')
      style('div.digest-post', 'margin-left: 15px; margin-top: -5px; max-width: 694px;')
      style('div.digest-post h1', 'font-size: 20px;')
      style('div.footer', 'color:#666; font-size:95%; text-align:center; padding-top:15px;')
      style('span.post-count', 'margin: 0 5px; color: #777;')
      style('pre', 'word-wrap: break-word; max-width: 694px;')
      style('code', 'background-color: #f1f1ff; padding: 2px 5px;')
      style('pre code', 'display: block; background-color: #f1f1ff; padding: 5px;')
      style('.featured-topic a', 'text-decoration: none; font-weight: bold; color: #006699; line-height:1.5em;')

      onebox_styles
      plugin_styles
    end

    # this method is reserved for styles specific to plugin
    def plugin_styles
      @@plugin_callbacks.each { |block| block.call(@fragment, @opts) }
    end

    def to_html
      strip_classes_and_ids
      replace_relative_urls
      @fragment.to_html.tap do |result|
        result.gsub!(/\[email-indent\]/, "<div style='margin-left: 15px'>")
        result.gsub!(/\[\/email-indent\]/, "</div>")
      end
    end

    def strip_avatars_and_emojis
      @fragment.search('img').each do |img|
        if img['src'] =~ /_avatar/
          img.parent['style'] = "vertical-align: top;" if img.parent.name == 'td'
          img.remove
        end

        if img['title'] && (img['src'] =~ /images\/emoji/ || img['src'] =~ /uploads\/default\/_emoji/)
          img.add_previous_sibling(img['title'] || "emoji")
          img.remove
        end
      end

      @fragment.to_s
    end

    def make_all_links_absolute
      site_uri = URI(Discourse.base_url)
      @fragment.css("a").each do |link|
        begin
          link["href"] = "#{site_uri}#{link['href']}" unless URI(link["href"].to_s).host.present?
        rescue URI::InvalidURIError, URI::InvalidComponentError
          # leave it
        end
      end
    end

    private

    def replace_relative_urls
      forum_uri = URI(Discourse.base_url)
      host = forum_uri.host
      scheme = forum_uri.scheme

      @fragment.css('[href]').each do |element|
        href = element['href']
        if href =~ /^\/\/#{host}/
          element['href'] = "#{scheme}:#{href}"
        end
      end
    end

    def correct_first_body_margin
      @fragment.css('.body p').each do |element|
        element['style'] = "margin-top:0; border: 0;"
      end
    end

    def correct_footer_style
      footernum = 0
      @fragment.css('.footer').each do |element|
        element['style'] = "color:#666;"
        linknum = 0
        element.css('a').each do |inner|
          # we want the first footer link to be specially highlighted as IMPORTANT
          if footernum == 0 and linknum == 0
            inner['style'] = "background-color: #006699; color:#ffffff; border-top: 4px solid #006699; border-right: 6px solid #006699; border-bottom: 4px solid #006699; border-left: 6px solid #006699; display: inline-block;"
          else
            inner['style'] = "color:#666;"
          end
          linknum += 1
        end
        footernum += 1
      end
    end

    def strip_classes_and_ids
      @fragment.css('*').each do |element|
        element.delete('class')
        element.delete('id')
      end
    end

    def reset_tables
      style('table', nil, cellspacing: '0', cellpadding: '0', border: '0')
    end

    def style(selector, style, attribs = {})
      @fragment.css(selector).each do |element|
        add_styles(element, style) if style
        attribs.each do |k,v|
          element[k] = v
        end
      end
    end
  end
end