FIX: Make discobot certificate faster/non blocking (#11344)

This moves the way we add the user avatar and site logo
to the discobot certificates from embeded base64 png to
just using the files urls in the href to the image tag.

This will make generation faster and the certificate
smaller overall, but it can't be used in a  `img` tag
anymore, since SVGs in `img` tags don't load the external images

In order to work around that we will move the certificate
in posts to an iframe, which works fine without any user
visible changes. For this to be possible the plugin automatically
adds the site current domain to the list of allowed iframe origins.

plugins/discourse-narrative-bot/lib/discourse_narrative_bot/base.rb

@@ -137,7 +137,7 @@ module DiscourseNarrativeBot
       src = Discourse.base_url + DiscourseNarrativeBot::Engine.routes.url_helpers.certificate_path(options)
       alt = CGI.escapeHTML(I18n.t("#{self.class::I18N_KEY}.certificate.alt"))
 
-      "<img class='discobot-certificate' src='#{src}' width='650' height='464' alt='#{alt}'>"
+      "<iframe class='discobot-certificate' src='#{src}' width='650' height='464' alt='#{alt}'>"
     end
 
     protected

plugins/discourse-narrative-bot/lib/discourse_narrative_bot/certificate_generator.rb

@@ -2,9 +2,9 @@
 
 module DiscourseNarrativeBot
   class CertificateGenerator
-    def initialize(user, date, avatar_data)
+    def initialize(user, date, avatar_url)
       @user = user
-      @avatar_data = avatar_data
+      @avatar_url = avatar_url
 
       date =
         begin
@@ -23,14 +23,14 @@ module DiscourseNarrativeBot
 
     def new_user_track
       svg_default_width = 538.583
-      logo_container = logo_group(55, svg_default_width, 350)
+      logo_container = logo_group(55, svg_default_width, 280)
 
       ApplicationController.render(inline: read_template('new_user'), assigns: assign_options(svg_default_width, logo_container))
     end
 
     def advanced_user_track
       svg_default_width = 722.8
-      logo_container = logo_group(40, svg_default_width, 280)
+      logo_container = logo_group(40, svg_default_width, 350)
 
       ApplicationController.render(inline: read_template('advanced_user'), assigns: assign_options(svg_default_width, logo_container))
     end
@@ -46,7 +46,7 @@ module DiscourseNarrativeBot
         width: width,
         discobot_user: @discobot_user,
         date: @date,
-        avatar_url: base64_image_data(@avatar_data),
+        avatar_url: @avatar_url,
         logo_group: logo_group,
         name: name
       }
@@ -59,48 +59,16 @@ module DiscourseNarrativeBot
     def logo_group(size, width, height)
       return unless SiteSetting.site_logo_small_url.present?
 
-      begin
-        uri = URI(SiteSetting.site_logo_small_url)
+      uri = URI(SiteSetting.site_logo_small_url)
 
-        logo_uri =
-          if uri.host.blank? || uri.scheme.blank?
-            URI("#{Discourse.base_url}/#{uri.path}")
-          else
-            uri
-          end
+      logo_uri =
+        if uri.host.blank? || uri.scheme.blank?
+          URI("#{Discourse.base_url}/#{uri.path}")
+        else
+          uri
+        end
 
-        <<~URL
-          <g transform="translate(#{width / 2 - (size / 2)} #{height})">
-            <image height="#{size}px" width="#{size}px" #{base64_image_link(logo_uri)}/>
-          </g>
-          URL
-      rescue URI::InvalidURIError
-        ''
-      end
-    end
-
-    def base64_image_data(data)
-      return "" if data.blank?
-      "xlink:href=\"data:image/png;base64,#{Base64.strict_encode64(data)}\""
-    end
-
-    def base64_image_link(url)
-      if image = fetch_image(url)
-        base64_image_data(image)
-      else
-        ""
-      end
-    end
-
-    def fetch_image(url)
-      FileHelper.download(
-        url.to_s,
-        max_file_size: SiteSetting.max_image_size_kb.kilobytes,
-        tmp_file_name: 'narrative-bot-logo',
-        follow_redirect: true
-      )&.read
-    rescue OpenURI::HTTPError
-      # Ignore if fetching image returns a non 200 response
+      { size: size, width: width, height: height, logo_uri: logo_uri }
     end
   end
 end

plugins/discourse-narrative-bot/lib/discourse_narrative_bot/templates/new_user.svg.erb

@@ -452,12 +452,14 @@
       <clipPath id="clipCircle">
         <circle r="15" cx="15" cy="15"/>
       </clipPath>
-      <image clip-path="url(#clipCircle)" height="30px" width="30px" <%= sanitize(@avatar_url) %>/>
+      <image clip-path="url(#clipCircle)" height="30px" width="30px" href="<%= @avatar_url %>"/>
     </g>
     <text x="<%= @width / 2 %>" y="240.94" text-anchor="middle" font-size="24" fill="#020403" font-family="Tangerine, Tangerine">
       <%= @name %>
     </text>
-    <%== @logo_group %>
+    <g transform="translate(<%= @logo_group[:width] / 2 - (@logo_group[:size] / 2) %> <%= @logo_group[:height] %>)">
+      <image height="<%= @logo_group[:size] %>px" width="<%= @logo_group[:size] %>px" href="<%= @logo_group[:logo_uri] %>"/>
+    </g>
   </g>
   <g id="Layer_1-2" data-name="Layer 1">
     <path d="M339.328 47.187c-.034 1.193 3.25 2.2 6.51 3.383 5.5 1.994 13.1 3.73 17.68 3.112 5.05-.55 4.982-2.217 4.054-4.8-.1-4.647.258-9.493.156-14.142l-27.128-.458c.5 4.698-1.778 8.207-1.272 12.905z" transform="translate(-.108)" fill-rule="evenodd" fill="url(#GradientFill_24)"/>

plugins/discourse-narrative-bot/plugin.rb

@@ -50,6 +50,11 @@ after_initialize do
   # Disable welcome message because that is what the bot is supposed to replace.
   SiteSetting.send_welcome_message = false if SiteSetting.send_welcome_message
 
+  certificate_path = "#{Discourse.base_url}/discobot/certificate.svg"
+  if SiteSetting.discourse_narrative_bot_enabled && !SiteSetting.allowed_iframes.include?(certificate_path)
+    SiteSetting.allowed_iframes = SiteSetting.allowed_iframes.split('|').append("#{Discourse.base_url}/discobot/certificate.svg").join('|')
+  end
+
   require_dependency 'plugin_store'
 
   module ::DiscourseNarrativeBot
@@ -94,8 +99,7 @@ after_initialize do
         raise Discourse::NotFound if user.blank?
 
         hijack do
-          avatar_data = fetch_avatar(user)
-          generator = CertificateGenerator.new(user, params[:date], avatar_data)
+          generator = CertificateGenerator.new(user, params[:date], avatar_url(user))
 
           svg = params[:type] == 'advanced' ? generator.advanced_user_track : generator.new_user_track
 
@@ -107,16 +111,8 @@ after_initialize do
 
       private
 
-      def fetch_avatar(user)
-        avatar_url = UrlHelper.absolute(Discourse.base_path + user.avatar_template.gsub('{size}', '250'))
-        FileHelper.download(
-          avatar_url.to_s,
-          max_file_size: SiteSetting.max_image_size_kb.kilobytes,
-          tmp_file_name: 'narrative-bot-avatar',
-          follow_redirect: true
-        )&.read
-      rescue OpenURI::HTTPError
-        # Ignore if fetching image returns a non 200 response
+      def avatar_url(user)
+        UrlHelper.absolute(Discourse.base_path + user.avatar_template.gsub('{size}', '250'))
       end
     end
   end

plugins/discourse-narrative-bot/spec/requests/discobot_certificate_spec.rb

@@ -36,7 +36,9 @@ describe "Discobot Certificate" do
         get '/discobot/certificate.svg', params: params
 
         expect(response.status).to eq(200)
-        expect(response.body).to include('<image height="55px" width="55px" />')
+        expect(response.body).to include('<svg')
+        expect(response.body).to include(user.avatar_template.gsub('{size}', '250'))
+        expect(response.body).to include(SiteSetting.site_logo_small_url)
       end
 
       describe 'when params are missing' do