Add placeholders to broadcast messages

This adds a post processing pipeline which gets triggered for
broadcast messages. The post process pipeline is required to
replace the placeholder with the curren_user's values like name
or email address.

app/helpers/broadcast_messages_helper.rb

@@ -47,7 +47,15 @@ module BroadcastMessagesHelper
   end
 
   def render_broadcast_message(broadcast_message)
-    Banzai.render_field(broadcast_message, :message).html_safe
+    if Feature.enabled?(:broadcast_message_placeholders)
+      Banzai.render_and_post_process(broadcast_message.message, {
+        current_user: current_user,
+        skip_project_check: true,
+        broadcast_message_placeholders: true
+      }).html_safe
+    else
+      Banzai.render_field(broadcast_message, :message).html_safe
+    end
   end
 
   def broadcast_type_options

lib/banzai/filter/broadcast_message_placeholders_filter.rb

+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # Replaces placeholders for broadcast messages with data from the current
+    # user or the instance.
+    class BroadcastMessagePlaceholdersFilter < HTML::Pipeline::Filter
+      def call
+        return doc unless context[:broadcast_message_placeholders]
+
+        doc.traverse { |node| replace_placeholders(node) }
+      end
+
+      private
+
+      def replace_placeholders(node)
+        if node.text? && !node.content.empty?
+          node.content = replace_content(node.content)
+        elsif href = link_href(node)
+          href.value = replace_content(href.value, url_safe_encoding: true)
+        end
+
+        node
+      end
+
+      def link_href(node)
+        node.element? &&
+          node.name == 'a' &&
+          node.attribute_nodes.find { |a| a.name == "href" }
+      end
+
+      def replace_content(content, url_safe_encoding: false)
+        placeholders.each do |placeholder, method|
+          regex = Regexp.new("{{#{placeholder}}}|#{CGI.escape("{{#{placeholder}}}")}")
+          value = url_safe_encoding ? CGI.escape(method.call.to_s) : method.call.to_s
+          content.gsub!(regex, value)
+        end
+
+        content
+      end
+
+      def placeholders
+        {
+          "email" => -> { current_user.try(:email) },
+          "name" => -> { current_user.try(:name) },
+          "user_id" => -> { current_user.try(:id) },
+          "username" => -> { current_user.try(:username) },
+          "instance_id" => -> { Gitlab::CurrentSettings.try(:uuid) }
+        }
+      end
+
+      def current_user
+        context[:current_user]
+      end
+    end
+  end
+end

lib/banzai/pipeline/post_process_pipeline.rb

@@ -8,7 +8,8 @@ module Banzai
       def self.filters
         @filters ||= FilterArray[
           *internal_link_filters,
-          Filter::AbsoluteLinkFilter
+          Filter::AbsoluteLinkFilter,
+          Filter::BroadcastMessagePlaceholdersFilter
         ]
       end
 

spec/features/broadcast_messages_spec.rb

@@ -57,4 +57,15 @@ describe 'Broadcast Messages' do
 
     it_behaves_like 'a dismissable Broadcast Messages'
   end
+
+  it 'renders broadcast message with placeholders' do
+    create(:broadcast_message, broadcast_type: 'notification', message: 'Hi {{name}}')
+
+    user = create(:user)
+    sign_in(user)
+
+    visit root_path
+
+    expect(page).to have_content "Hi #{user.name}"
+  end
 end

spec/helpers/broadcast_messages_helper_spec.rb

@@ -27,10 +27,11 @@ describe BroadcastMessagesHelper do
   end
 
   describe 'broadcast_message' do
+    let_it_be(:user) { create(:user) }
     let(:current_broadcast_message) { BroadcastMessage.new(message: 'Current Message') }
 
     before do
-      allow(helper).to receive(:current_user).and_return(create(:user))
+      allow(helper).to receive(:current_user).and_return(user)
     end
 
     it 'returns nil when no current message' do

spec/lib/banzai/filter/broadcast_message_placeholders_filter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Banzai::Filter::BroadcastMessagePlaceholdersFilter do
+  include FilterSpecHelper
+
+  subject { filter(text, current_user: user, broadcast_message_placeholders: true).to_html }
+
+  describe 'when current user is set' do
+    let_it_be(:user) { create(:user, email: "helloworld@example.com", name: "GitLab Tanunki :)") }
+
+    context 'replaces placeholder in text' do
+      let(:text) { 'Email: {{email}}' }
+
+      it { expect(subject).to eq("Email: #{user.email}") }
+    end
+
+    context 'replaces placeholder when they are in a link' do
+      let(:text) { '<a href="http://example.com?email={{email}}"">link</a>' }
+
+      it { expect(subject).to eq("<a href=\"http://example.com?email=helloworld%40example.com\">link</a>") }
+    end
+
+    context 'replaces placeholder when they are in an escaped link' do
+      let(:text) { '<a href="http://example.com?name=%7B%7Bname%7D%7D">link</a>' }
+
+      it { expect(subject).to eq("<a href=\"http://example.com?name=GitLab+Tanunki+%3A%29\">link</a>") }
+    end
+
+    context 'works with empty text' do
+      let(:text) {" "}
+
+      it { expect(subject).to eq(" ") }
+    end
+
+    context 'replaces multiple placeholders in a given text' do
+      let(:text) { "{{email}} {{name}}" }
+
+      it { expect(subject).to eq("#{user.email} #{user.name}") }
+    end
+
+    context 'available placeholders' do
+      context 'replaces the email of the user' do
+        let(:text) { "{{email}}"}
+
+        it { expect(subject).to eq(user.email) }
+      end
+
+      context 'replaces the name of the user' do
+        let(:text) { "{{name}}"}
+
+        it { expect(subject).to eq(user.name) }
+      end
+
+      context 'replaces the ID of the user' do
+        let(:text) { "{{user_id}}" }
+
+        it { expect(subject).to eq(user.id.to_s) }
+      end
+
+      context 'replaces the username of the user' do
+        let(:text) { "{{username}}" }
+
+        it { expect(subject).to eq(user.username) }
+      end
+
+      context 'replaces the instance_id' do
+        before do
+          stub_application_setting(uuid: '123')
+        end
+
+        let(:text) { "{{instance_id}}" }
+
+        it { expect(subject).to eq(Gitlab::CurrentSettings.uuid) }
+      end
+    end
+  end
+
+  describe 'when there is no current user set' do
+    let(:user) { nil }
+
+    context 'replaces placeholder with empty string' do
+      let(:text) { "Email: {{email}}" }
+
+      it { expect(subject).to eq("Email: ") }
+    end
+  end
+end