Refactor and tests.

app/models/abilities/administrator.rb

@@ -33,7 +33,7 @@ module Abilities
       can :unmark_featured, Debate
 
       can :comment_as_administrator, [Debate, Comment, Proposal, Poll::Question, Budget::Investment,
-                                      Legislation::Question, Legislation::Annotation]
+                                      Legislation::Question, Legislation::Annotation, Topic]
 
       can [:search, :create, :index, :destroy], ::Administrator
       can [:search, :create, :index, :destroy], ::Moderator

app/models/abilities/moderator.rb

@@ -6,7 +6,7 @@ module Abilities
       merge Abilities::Moderation.new(user)
 
       can :comment_as_moderator, [Debate, Comment, Proposal, Budget::Investment, Poll::Question,
-                                  Legislation::Question, Legislation::Annotation]
+                                  Legislation::Question, Legislation::Annotation, Topic]
     end
   end
 end

app/models/community.rb

@@ -3,4 +3,7 @@ class Community < ActiveRecord::Base
   has_one :investment
   has_many :topics
 
+  def participants
+    User.community_participants(self)
+  end
 end

app/models/topic.rb

@@ -1,4 +1,6 @@
 class Topic < ActiveRecord::Base
+  include Flaggable
+
   acts_as_paranoid column: :hidden_at
   include ActsAsParanoidAliases
 
@@ -7,15 +9,12 @@ class Topic < ActiveRecord::Base
 
   has_many :comments, as: :commentable
 
-  after_create :associate_comment
+  validates :title, presence: true
+  validates :description, presence: true
+  validates :author, presence: true
 
   scope :sort_by_newest, -> { order(created_at: :desc) }
   scope :sort_by_oldest, -> { order(created_at: :asc) }
   scope :sort_by_most_commented,   -> { reorder(comments_count: :desc) }
 
-  private
-
-  def associate_comment
-    Comment.create(commentable: self, user: self.author, body: self.description_as_comment)
-  end
 end

app/models/user.rb

@@ -315,7 +315,13 @@ class User < ActiveRecord::Base
 
   def self.community_participants(community)
     topics_ids = community.topics.pluck(:id)
-    User.joins(:comments).where("comments.commentable_id IN (?) and comments.commentable_type = 'Topic'", topics_ids)
+    users_who_commented = User.joins(:comments).where("comments.commentable_id IN (?) and comments.commentable_type = 'Topic'", topics_ids).uniq
+
+    author_ids = community.topics.pluck(:author_id)
+    users_who_authors = User.where("users.id IN (?)", author_ids)
+
+    users_participants = users_who_commented + users_who_authors
+    users_participants.uniq
   end
 
   private