discourse/lib/email/styles.rb

# frozen_string_literal: true

#
# HTML emails don't support CSS, so we can use nokogiri to inline attributes based on
# matchers.
#
module Email
  class Styles
    MAX_IMAGE_DIMENSION = 400
    ONEBOX_IMAGE_BASE_STYLE =
      "max-height: 80%; max-width: 20%; height: auto; float: left; margin-right: 10px;"
    ONEBOX_IMAGE_THUMBNAIL_STYLE = "width: 60px;"
    ONEBOX_INLINE_AVATAR_STYLE = "width: 20px; height: 20px; float: none; vertical-align: middle;"

    @@plugin_callbacks = []

    attr_accessor :fragment

    delegate :css, to: :fragment

    def initialize(html, opts = nil)
      @html = html
      @opts = opts || {}
      @fragment = Nokogiri::HTML5.parse(@html)
      @custom_styles = nil
    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 custom_styles
      return @custom_styles unless @custom_styles.nil?

      css = EmailStyle.new.compiled_css
      @custom_styles = {}

      if !css.blank?
        # there is a minor race condition here, CssParser could be
        # loaded by ::CssParser::Parser not loaded
        require "css_parser" unless defined?(::CssParser::Parser)

        parser = ::CssParser::Parser.new(import: false)
        parser.load_string!(css)
        parser.each_selector do |selector, value|
          @custom_styles[selector] ||= +""
          @custom_styles[selector] << value
        end
      end

      @custom_styles
    end

    def format_basic
      uri = URI(Discourse.base_url)

      # Remove SVGs
      @fragment.css('svg, img[src$=".svg"]').remove

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

          if (img["class"] && img["class"]["emoji"]) || (img["src"] && img["src"][%r{/_?emoji/}])
            img["width"] = img["height"] = 20
          else
            # use dimensions of original iPhone screen for 'too big, let device rescale'
            if img["width"].to_i > (320) || img["height"].to_i > (480)
              img["width"] = img["height"] = "auto"
            end
          end

          if img["src"]
            # ensure all urls are absolute
            img["src"] = "#{Discourse.base_url}#{img["src"]}" if img["src"][%r{\A/[^/]}]
            # ensure no schemaless urls
            img["src"] = "#{uri.scheme}:#{img["src"]}" if img["src"][%r{\A//}]
          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 { |img| add_styles(img, "max-width: 100%;") if img["style"] !~ /max-width/ }

      # topic featured link
      @fragment
        .css("a.topic-featured-link")
        .each do |e|
          e[
            "style"
          ] = "color:#858585;padding:2px 8px;border:1px solid #e6e6e6;border-radius:2px;box-shadow:0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);"
        end

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

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

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

      style(
        "blockquote",
        "border-left: 5px solid #e9e9e9; background-color: #f8f8f8; margin-left: 0; padding: 12px;",
      )

      # Oneboxes
      style(
        "aside.onebox",
        "border: 5px solid #e9e9e9; padding: 12px 25px 12px 12px; margin-bottom: 10px;",
      )
      style("aside.onebox header img.site-icon", "width: 16px; height: 16px; margin-right: 3px;")
      style("aside.onebox header a[href]", "color: #222222; text-decoration: none;")
      style("aside.onebox .onebox-body", "clear: both")
      style("aside.onebox .onebox-body img:not(.onebox-avatar-inline)", ONEBOX_IMAGE_BASE_STYLE)
      style("aside.onebox .onebox-body img.thumbnail", ONEBOX_IMAGE_THUMBNAIL_STYLE)
      style(
        "aside.onebox .onebox-body h3, aside.onebox .onebox-body h4",
        "font-size: 1.17em; margin: 10px 0;",
      )
      style(".onebox-metadata", "color: #919191")
      style(".github-info", "margin-top: 10px;")
      style(".github-info .added", "color: #090;")
      style(".github-info .removed", "color: #e45735;")
      style(".github-info div", "display: inline; margin-right: 10px;")
      style(".github-icon-container", "float: left;")
      style(".github-icon-container *", "fill: #646464; width: 40px; height: 40px;")
      style(
        ".github-body-container",
        'font-family: Consolas, Menlo, Monaco, "Lucida Console", "Liberation Mono", "DejaVu Sans Mono", "Bitstream Vera Sans Mono", "Courier New", monospace; margin-top: 1em !important;',
      )
      style(".onebox-avatar-inline", ONEBOX_INLINE_AVATAR_STYLE)

      @fragment.css(".github-body-container .excerpt").remove

      @fragment.css("aside.quote blockquote > p").each { |p| p["style"] = "padding: 0;" }

      # Convert all `aside.quote` tags to `blockquote`s
      @fragment
        .css("aside.quote")
        .each do |n|
          original_node = n.dup
          original_node.search("div.quote-controls").remove
          blockquote =
            (
              if original_node.css("blockquote").inner_html.strip.start_with?("<p")
                original_node.css("blockquote").inner_html
              else
                "<p style='padding: 0;'>#{original_node.css("blockquote").inner_html}</p>"
              end
            )
          n.inner_html = original_node.css("div.title").inner_html + blockquote
          n.name = "blockquote"
        end

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

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

            src_uri =
              i["data-original-href"].present? ? URI(i["data-original-href"]) : 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(
              Nokogiri::HTML5.fragment(
                "<p><a href='#{src_uri}'>#{CGI.escapeHTML(display_src)}</a><p>",
              ),
            )
          rescue URI::Error
            # If the URL is weird, remove the iframe
            i.remove
          end
        end
    end

    def format_html
      correct_first_body_margin
      correct_footer_style
      correct_footer_style_highlight_first
      strip_hashtag_link_icons
      reset_tables

      html_lang = SiteSetting.default_locale.sub("_", "-")
      style("html", nil, :lang => html_lang, "xml:lang" => html_lang)
      style("body", "line-height: 1.4; text-align:#{Rtl.new(nil).enabled? ? "right" : "left"};")
      style("body", nil, dir: Rtl.new(nil).enabled? ? "rtl" : "ltr")

      style(
        ".with-dir",
        "text-align:#{Rtl.new(nil).enabled? ? "right" : "left"};",
        dir: Rtl.new(nil).enabled? ? "rtl" : "ltr",
      )

      style("blockquote > :first-child", "margin-top: 0;")
      style("blockquote > :last-child", "margin-bottom: 0;")
      style("blockquote > p", "padding: 0;")

      style(
        ".with-accent-colors",
        "background-color: #{SiteSetting.email_accent_bg_color}; color: #{SiteSetting.email_accent_fg_color};",
      )
      style("h4", "color: #222;")
      style("h3", "margin: 30px 0 10px;")
      style("hr", "background-color: #ddd; height: 1px; border: 1px;")
      style(
        "a",
        "text-decoration: none; font-weight: bold; color: #{SiteSetting.email_link_color};",
      )
      style("ul", "margin: 0 0 0 10px; padding: 0 0 0 20px;")
      style("li", "padding-bottom: 10px")
      style("div.summary-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: #f9f9f9; padding: 2px 5px;")
      style("pre code", "display: block; background-color: #f9f9f9; overflow: auto; padding: 5px;")
      style("pre.onebox code", "white-space: normal;")
      style("pre code li", "white-space: pre;")
      style(
        ".featured-topic a",
        "text-decoration: none; font-weight: bold; color: #{SiteSetting.email_link_color}; line-height:1.5em;",
      )
      style(
        ".summary-email",
        "-moz-box-sizing:border-box;-ms-text-size-adjust:100%;-webkit-box-sizing:border-box;-webkit-text-size-adjust:100%;box-sizing:border-box;color:#0a0a0a;font-family:Arial,sans-serif;font-size:14px;font-weight:400;line-height:1.3;margin:0;min-width:100%;padding:0;width:100%",
      )

      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;text-decoration:none;font-weight:bold",
      )
      style(".username-link", "color:#{SiteSetting.email_link_color};")
      style(".username-title", "color:#777;margin-left:5px;")
      style(
        ".user-title",
        "font-size:13px;font-family:'lucida grande',tahoma,verdana,arial,sans-serif;text-decoration:none;margin-left:5px;color: #999;",
      )
      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("div.body", "padding-top:5px;")
      style(".whisper div.body", "font-style: italic; color: #9c9c9c;")
      style(".lightbox-wrapper .meta", "display: none")
      style("div.undecorated-link-footer a", "font-weight: normal;")
      style(
        ".mso-accent-link",
        "mso-border-alt: 6px solid #{SiteSetting.email_accent_bg_color}; background-color: #{SiteSetting.email_accent_bg_color};",
      )
      style(
        ".reply-above-line",
        "font-size: 10px;font-family:'lucida grande',tahoma,verdana,arial,sans-serif;color: #b5b5b5;padding: 5px 0px 20px;border-top: 1px dotted #ddd;",
      )

      onebox_styles
      plugin_styles
      dark_mode_styles

      style(".post-excerpt img", "max-width: 50%; max-height: #{MAX_IMAGE_DIMENSION}px;")

      format_custom
    end

    def format_custom
      custom_styles.each { |selector, value| style(selector, value) }
    end

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

    def stripped_media
      @stripped_media ||=
        @fragment.css("[data-stripped-secure-media], [data-stripped-secure-upload]")
    end

    def stripped_upload_sha_map
      @stripped_upload_sha_map ||=
        begin
          upload_shas = {}
          stripped_media.each do |div|
            url = div["data-stripped-secure-media"] || div["data-stripped-secure-upload"]
            upload_shas[url] = Upload.sha1_from_long_url(url)
          end
          upload_shas
        end
    end

    def stripped_secure_image_uploads
      upload_shas = stripped_upload_sha_map
      Upload.select(:original_filename, :sha1).where(sha1: upload_shas.values)
    end

    def inline_secure_images(attachments, attachments_index)
      uploads = stripped_secure_image_uploads
      upload_shas = stripped_upload_sha_map
      stripped_media.each do |div|
        upload =
          uploads.find do |upl|
            upl.sha1 ==
              upload_shas[div["data-stripped-secure-media"] || div["data-stripped-secure-upload"]]
          end
        next if !upload

        if attachments[attachments_index[upload.sha1]]
          url = attachments[attachments_index[upload.sha1]].url

          onebox_type = div["data-onebox-type"]
          style =
            if onebox_type
              onebox_style =
                (
                  if onebox_type == "avatar-inline"
                    ONEBOX_INLINE_AVATAR_STYLE
                  else
                    ONEBOX_IMAGE_THUMBNAIL_STYLE
                  end
                )
              "#{onebox_style} #{ONEBOX_IMAGE_BASE_STYLE}"
            else
              calculate_width_and_height_style(div)
            end

          div.add_next_sibling(<<~HTML)
            <img src="#{url}" data-embedded-secure-image="true" style="#{style}" />
          HTML
          div.remove
        end
      end
    end

    def deduplicate_style(style)
      styles = {}

      style
        .split(";")
        .select(&:present?)
        .map { _1.split(":", 2).map(&:strip) }
        .each { |k, v| styles[k] = v if k.present? && v.present? }

      styles.map { |k, v| "#{k}:#{v}" }.join(";")
    end

    def deduplicate_styles
      @fragment
        .css("[style]")
        .each { |element| element["style"] = deduplicate_style element["style"] }
    end

    def to_html
      # needs to be before class + id strip because we need to style redacted
      # media and also not double-redact already redacted from lower levels
      replace_secure_uploads_urls if SiteSetting.secure_uploads?
      strip_classes_and_ids
      replace_relative_urls
      deduplicate_styles

      @fragment.to_html
    end

    def to_s
      @fragment.to_s
    end

    def strip_avatars_and_emojis
      @fragment
        .search("img")
        .each do |img|
          next unless img["src"]

          if img["src"][/_avatar/]
            img.parent["style"] = "vertical-align: top;" if img.parent&.name == "td"
            img.remove
          end

          if img["title"] && img["src"][%r{/_?emoji/}]
            img.add_previous_sibling(img["title"] || "emoji")
            img.remove
          end
        end
    end

    def strip_hashtag_link_icons
      @fragment
        .search(".hashtag-cooked")
        .each do |hashtag|
          hashtag.children.each(&:remove)
          hashtag.add_child(<<~HTML)
          <span>##{hashtag["data-slug"]}</span>
        HTML
        end
    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"]}" if URI(link["href"].to_s).host.blank?
          rescue URI::Error
            # leave it
          end
        end
    end

    private

    def dark_mode_styles
      # When we ship the email template and its styles we strip all css classes so to give our
      # dark mode styles we are including in the template a selector we add a data-attr of 'dm=value' to
      # the appropriate place
      style(
        ".digest-header, .digest-topic, .digest-topic-title-wrapper, .digest-topic-stats, .popular-post-excerpt",
        nil,
        dm: "header",
      )
      style(
        ".digest-content, .header-popular-posts, .spacer, .popular-post-spacer, .popular-post-meta, .digest-new-header, .digest-new-topic, .body",
        nil,
        dm: "body",
      )
      style(".with-accent-colors, .digest-content-header", nil, dm: "body_primary")
      style(".digest-topic-body", nil, dm: "topic-body")
      style(".summary-footer", nil, dm: "text-color")
      style("code, pre code, blockquote", nil, dm: "bg")
    end

    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"]
          element["href"] = "#{scheme}:#{href}" if href.start_with?("\/\/#{host}")
        end
    end

    def calculate_width_and_height_style(div)
      width = div["data-width"]
      height = div["data-height"]
      if width.present? && height.present? && height.to_i < MAX_IMAGE_DIMENSION &&
           width.to_i < MAX_IMAGE_DIMENSION
        "width: #{width}px; height: #{height}px;"
      else
        "max-width: 50%; max-height: #{MAX_IMAGE_DIMENSION}px;"
      end
    end

    def replace_secure_uploads_urls
      # strip again, this can be done at a lower level like in the user
      # notification template but that may not catch everything
      PrettyText.strip_secure_uploads(@fragment)

      style(
        "div.secure-upload-notice",
        "border: 5px solid #e9e9e9; padding: 5px; display: inline-block;",
      )
      style("div.secure-upload-notice a", "color: #{SiteSetting.email_link_color}")
    end

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

    def correct_footer_style
      @fragment
        .css(".footer")
        .each do |element|
          element["style"] = "color:#666;"
          element.css("a").each { |inner| inner["style"] = "color:#666;" }
        end
    end

    def correct_footer_style_highlight_first
      footernum = 0
      @fragment
        .css(".footer.highlight")
        .each do |element|
          linknum = 0
          element
            .css("a")
            .each do |inner|
              # we want the first footer link to be specially highlighted as IMPORTANT
              if footernum == (0) && linknum == (0)
                bg_color = SiteSetting.email_accent_bg_color
                inner[
                  "style"
                ] = "background-color: #{bg_color}; color: #{SiteSetting.email_accent_fg_color}; border-top: 4px solid #{bg_color}; border-right: 6px solid #{bg_color}; border-bottom: 4px solid #{bg_color}; border-left: 6px solid #{bg_color}; display: inline-block; font-weight: bold;"
              end
              # rubocop:disable Lint/NonLocalExitFromIterator
              return
            end
          return
          # rubocop:enable Lint/NonLocalExitFromIterator
        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 { |k, v| element[k] = v }
        end
    end
  end
end