FEATURE: add the first 3 participants in a private message

app/assets/javascripts/discourse/controllers/user_topics_list_controller.js

@@ -8,6 +8,7 @@
 **/
 Discourse.UserTopicsListController = Discourse.ObjectController.extend({
   hideCategory: false,
+  showParticipants: false,
 
   actions: {
     loadMore: function() {

app/assets/javascripts/discourse/models/topic_list.js

@@ -163,6 +163,11 @@ Discourse.TopicList.reopenClass({
       t.posters.forEach(function(p) {
         p.user = users[p.user_id];
       });
+      if (t.participants) {
+        t.participants.forEach(function(p) {
+          p.user = users[p.user_id];
+        });
+      }
       return Discourse.Topic.create(t);
     });
   },

app/assets/javascripts/discourse/routes/user_topic_list_routes.js

@@ -8,7 +8,8 @@ Discourse.UserTopicListRoute = Discourse.Route.extend({
     this.controllerFor('user_activity').set('userActionType', this.get('userActionType'));
     this.controllerFor('user_topics_list').setProperties({
       model: model,
-      hideCategory: false
+      hideCategory: false,
+      showParticipants: false
     });
   }
 });
@@ -23,7 +24,10 @@ function createPMRoute(viewName, path) {
 
     setupController: function() {
       this._super.apply(this, arguments);
-      this.controllerFor('user_topics_list').set('hideCategory', true);
+      this.controllerFor('user_topics_list').setProperties({
+        hideCategory: true,
+        showParticipants: true
+      });
       this.controllerFor('user').setProperties({
         pmView: viewName,
         indexStream: false

app/assets/javascripts/discourse/templates/components/basic-topic-list.js.handlebars

@@ -3,26 +3,18 @@
     <table id="topic-list">
       <thead>
         <tr>
-          {{#sortable-heading sortBy="default"}}
-            {{i18n topic.title}}
-          {{/sortable-heading}}
+          <th>{{i18n topic.title}}</th>
           {{#unless controller.hideCategory}}
-          {{#sortable-heading sortBy="category"}}
-              {{i18n category_title}}
-            {{/sortable-heading}}
+            <th>{{i18n category_title}}</th>
           {{/unless}}
-          {{#sortable-heading sortBy="posts" number=true}}
-            {{i18n posts}}
-          {{/sortable-heading}}
-          {{#sortable-heading sortBy="likes" number=true}}
-            {{i18n likes}}
-          {{/sortable-heading}}
-          {{#sortable-heading sortBy="views" number=true}}
-            {{i18n views}}
-          {{/sortable-heading}}
-          {{#sortable-heading sortBy="activity" number=true colspan="2"}}
-            {{i18n activity}}
-          {{/sortable-heading}}
+          <th>{{i18n posts}}</th>
+          {{#if controller.showParticipants}}
+            <th>{{i18n users}}</th>
+          {{else}}
+            <th>{{i18n likes}}</th>
+          {{/if}}
+          <th>{{i18n views}}</th>
+          <th>{{i18n activity}}</th>
         </tr>
       </thead>
 
@@ -44,20 +36,33 @@
             </td>
 
             {{#unless controller.hideCategory}}
-            <td class="category">
-              {{categoryLink topic.category showParent=true}}
-            </td>
+              <td class="category">
+                {{categoryLink topic.category showParent=true}}
+              </td>
             {{/unless}}
 
-            <td class='num posts'><a href="{{unbound topic.lastUnreadUrl}}" class='badge-posts'>{{number topic.posts_count numberKey="posts_long"}}</a></td>
-
-            <td class='num likes'>
-              {{#if topic.like_count}}
-                <a href='{{unbound topic.url}}{{#if topic.has_summary}}?filter=summary{{/if}}'>{{unbound topic.like_count}} <i class='fa fa-heart'></i></a>
-              {{/if}}
+            <td class='num posts'>
+              <a href="{{unbound topic.lastUnreadUrl}}" class='badge-posts'>{{number topic.posts_count numberKey="posts_long"}}</a>
+            </td>
+
+            {{#if controller.showParticipants}}
+              <td class='participants'>
+                {{#each topic.participants}}
+                  <a href="{{user.path}}" class="{{extras}}">{{avatar this usernamePath="user.username" imageSize="small"}}</a>
+                {{/each}}
+              </td>
+            {{else}}
+              <td class='num likes'>
+                {{#if topic.like_count}}
+                  <a href='{{unbound topic.url}}{{#if topic.has_summary}}?filter=summary{{/if}}'>{{unbound topic.like_count}} <i class='fa fa-heart'></i></a>
+                {{/if}}
+              </td>
+            {{/if}}
+
+            <td {{bind-attr class=":num :views topic.viewsHeat"}}>
+              {{number topic.views numberKey="views_long"}}
             </td>
 
-            <td {{bind-attr class=":num :views topic.viewsHeat"}}>{{number topic.views numberKey="views_long"}}</td>
             {{#if topic.bumped}}
               <td class='num activity'>
                 <a href="{{unbound topic.url}}" class='{{coldAgeClass created_at}}' title='{{i18n first_post}}: {{{rawDate topic.created_at}}}' >{{unboundAge topic.created_at}}</a>
@@ -78,9 +83,11 @@
     </table>
   {{else}}
     <div class='alert alert-info'>
-    {{i18n choose_topic.none_found}}
+      {{i18n choose_topic.none_found}}
     </div>
   {{/if}}
 {{else}}
-  <div class='spinner'>{{i18n loading}}</div>
+  <div class='spinner'>
+    {{i18n loading}}
+  </div>
 {{/if}}

app/assets/javascripts/discourse/templates/list/user_topics_list.js.handlebars

@@ -1 +1 @@
-{{basic-topic-list topicList=model hideCategory=hideCategory}}
+{{basic-topic-list topicList=model hideCategory=hideCategory showParticipants=showParticipants}}

app/assets/javascripts/discourse/templates/mobile/components/basic-topic-list.js.handlebars

@@ -29,9 +29,6 @@
             {{/if}}
             </div>
             <div class="topic-item-stats clearfix">
-              <div class='category'>
-                {{categoryLink category showParent=true}}
-              </div>
               <div class="pull-right">
                 <div class='num posts'>
                   <a href="{{lastUnreadUrl}}">{{number posts_count numberKey="posts_long"}}</a>
@@ -53,6 +50,18 @@
                   </div>
                 {{/if}}
               </div>
+              {{#unless controller.hideCategory}}
+                <div class='category'>
+                  {{categoryLink category showParent=true}}
+                </div>
+              {{/unless}}
+              {{#if controller.showParticipants}}
+                <div class='participants'>
+                  {{#each topic.participants}}
+                    <a href="{{user.path}}" class="{{extras}}">{{avatar this usernamePath="user.username" imageSize="small"}}</a>
+                  {{/each}}
+                </div>
+              {{/if}}
               <div class="clearfix"></div>
             </div>
           </td>

app/assets/stylesheets/desktop/topic-list.scss

@@ -183,6 +183,11 @@
   }
   .posters {
     min-width: 150px;
+  }
+  .participants {
+    min-width: 85px;
+  }
+  .posters, .participants {
     > a {
       float: left;
       margin-right: 4px;

app/models/topic.rb

@@ -22,6 +22,8 @@ class Topic < ActiveRecord::Base
   def_delegator :notifier, :muted!, :notify_muted!
   def_delegator :notifier, :toggle_mute, :toggle_mute
 
+  attr_accessor :allowed_user_ids
+
   def self.max_sort_order
     2**31 - 1
   end
@@ -103,6 +105,7 @@ class Topic < ActiveRecord::Base
   # When we want to temporarily attach some data to a forum topic (usually before serialization)
   attr_accessor :user_data
   attr_accessor :posters  # TODO: can replace with posters_summary once we remove old list code
+  attr_accessor :participants
   attr_accessor :topic_list
   attr_accessor :meta_data
   attr_accessor :include_last_poster
@@ -594,11 +597,14 @@ class Topic < ActiveRecord::Base
     end
   end
 
-
   def posters_summary(options = {})
     @posters_summary ||= TopicPostersSummary.new(self, options).summary
   end
 
+  def participants_summary(options = {})
+    @participants_summary ||= TopicParticipantsSummary.new(self, options).summary
+  end
+
   # Enable/disable the star on the topic
   def toggle_star(user, starred)
     Topic.transaction do

app/models/topic_list.rb

@@ -20,6 +20,11 @@ class TopicList
   def topics
     return @topics if @topics.present?
 
+    # copy side-loaded data (allowed users) before dumping it with the .to_a
+    @topics_input.each do |t|
+      t.allowed_user_ids = t.allowed_users.map { |u| u.id }.to_a
+    end
+
     @topics = @topics_input.to_a
 
     # Attach some data for serialization to each topic
@@ -28,7 +33,7 @@ class TopicList
     # Create a lookup for all the user ids we need
     user_ids = []
     @topics.each do |ft|
-      user_ids << ft.user_id << ft.last_post_user_id << ft.featured_user_ids
+      user_ids << ft.user_id << ft.last_post_user_id << ft.featured_user_ids << ft.allowed_user_ids
     end
 
     avatar_lookup = AvatarLookup.new(user_ids)
@@ -36,10 +41,11 @@ class TopicList
     @topics.each do |ft|
       ft.user_data = @topic_lookup[ft.id] if @topic_lookup.present?
       ft.posters = ft.posters_summary(avatar_lookup: avatar_lookup)
+      ft.participants = ft.participants_summary(avatar_lookup: avatar_lookup, user: @current_user)
       ft.topic_list = self
     end
 
-    return @topics
+    @topics
   end
 
   def topic_ids

app/models/topic_participants_summary.rb

@@ -0,0 +1,37 @@
+class TopicParticipantsSummary
+  attr_reader :topic, :options
+
+  def initialize(topic, options = {})
+    @topic = topic
+    @options = options
+    @user = options[:user]
+  end
+
+  def summary
+    top_participants.compact.map(&method(:new_topic_poster_for))
+  end
+
+  def new_topic_poster_for(user)
+    TopicPoster.new.tap do |topic_poster|
+      topic_poster.user = user
+      topic_poster.extras = 'latest' if is_latest_poster?(user)
+    end
+  end
+
+  def is_latest_poster?(user)
+    topic.last_post_user_id == user.id
+  end
+
+  def top_participants
+    user_ids.map { |id| avatar_lookup[id] }.compact.uniq.take(3)
+  end
+
+  def user_ids
+    return [] unless @user
+    [topic.user_id] + topic.allowed_user_ids - [@user.id]
+  end
+
+  def avatar_lookup
+    @avatar_lookup ||= options[:avatar_lookup] || AvatarLookup.new(user_ids)
+  end
+end

app/models/topic_posters_summary.rb

@@ -49,7 +49,7 @@ class TopicPostersSummary
       :frequent_poster,
       :frequent_poster,
       :frequent_poster
-    ].map { |description| I18n.t(description) })
+      ].map { |description| I18n.t(description) })
   end
 
   def last_poster_is_topic_creator?

app/serializers/topic_list_item_serializer.rb

@@ -9,10 +9,12 @@ class TopicListItemSerializer < ListableTopicSerializer
              :category_id
 
   has_many :posters, serializer: TopicPosterSerializer, embed: :objects
+  has_many :participants, serializer: TopicPosterSerializer, embed: :objects
 
   def starred
     object.user_data.starred?
   end
+
   alias :include_starred? :has_user_data
 
   def posters
@@ -23,4 +25,12 @@ class TopicListItemSerializer < ListableTopicSerializer
     object.posters.find { |poster| poster.user.id == object.last_post_user_id }.try(:user).try(:username)
   end
 
+  def participants
+    object.participants_summary || []
+  end
+
+  def include_participants?
+    object.private_message?
+  end
+
 end

lib/avatar_lookup.rb

@@ -13,11 +13,11 @@ class AvatarLookup
 
   def self.lookup_columns
     @lookup_columns ||= [:id,
-                            :email,
-                            :username,
-                            :use_uploaded_avatar,
-                            :uploaded_avatar_template,
-                            :uploaded_avatar_id]
+                         :email,
+                         :username,
+                         :use_uploaded_avatar,
+                         :uploaded_avatar_template,
+                         :uploaded_avatar_id]
   end
 
   def users
@@ -27,12 +27,9 @@ class AvatarLookup
   def user_lookup_hash
     # adding tap here is a personal taste thing
     hash = {}
-    User
-      .where(:id => @user_ids)
-      .select(AvatarLookup.lookup_columns)
-      .each{|user|
-        hash[user.id] = user
-      }
+    User.where(:id => @user_ids)
+        .select(AvatarLookup.lookup_columns)
+        .each{ |user| hash[user.id] = user }
     hash
   end
 end

lib/topic_query.rb

@@ -159,7 +159,8 @@ class TopicQuery
       options.reverse_merge!(per_page: SiteSetting.topics_per_page)
 
       # Start with a list of all topics
-      result = Topic.where("topics.id IN (SELECT topic_id FROM topic_allowed_users WHERE user_id = #{user.id.to_i})")
+      result = Topic.includes(:allowed_users)
+                    .where("topics.id IN (SELECT topic_id FROM topic_allowed_users WHERE user_id = #{user.id.to_i})")
                     .joins("LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = #{user.id.to_i})")
                     .order(TopicQuerySQL.order_nocategory_basic_bumped)
                     .private_messages

spec/models/topic_participants_summary_spec.rb

@@ -0,0 +1,26 @@
+require 'spec_helper'
+
+describe TopicParticipantsSummary do
+  describe '#summary' do
+    let(:summary) { described_class.new(topic, user: topic_creator).summary }
+
+    let(:topic) do
+      Fabricate(:topic,
+        user: topic_creator,
+        archetype: Archetype::private_message
+      )
+    end
+
+    let(:topic_creator) { Fabricate(:user) }
+    let(:user1) { Fabricate(:user) }
+    let(:user2) { Fabricate(:user) }
+    let(:user3) { Fabricate(:user) }
+    let(:user4) { Fabricate(:user) }
+
+    it "must never contains the user and at most 3 participants" do
+      topic.allowed_user_ids = [user1.id, user2.id, user3.id, user4.id]
+      expect(summary.map(&:user)).to eq([user1, user2, user3])
+    end
+
+  end
+end