comment.rb

class Comment < ActiveRecord::Base
  include Attachable, AdminPanel,
    Subscribable, Activitable

  belongs_to :commentable, polymorphic: true
  belongs_to :creator, class_name: User

  validates :content, presence: true
  validates :commentable, presence: true
  validates :creator, presence: true

  def project_id
    commentable.project_id
  end

  private

  concerning :CommentSearch do
    included do
      include Tire::Model::Search
      include Tire::Model::Callbacks

      mapping do
        indexes :content
        indexes :project_id, type: :integer
        indexes :created_at
      end

      def self.search(term, project_ids)
        tire.search(load: true) do
          query { string term }
          filter :terms, project_id: project_ids
          sort { by :created_at, :desc }
        end
      end
    end

    def to_indexed_json
      to_json(methods: [:project_id])
    end
  end
end

comment_creator.rb

class CommentCreator
  attr_accessor :comment

  def initialize(project, creator, params, attachments = [])
    @comment = CommentBuilder.new(project, creator, params, attachments).build
  end

  def create
    if comment.save
      CommentNotification.new(comment).run
      true
    else
      false
    end
  end

  private

  class CommentBuilder
    include Subscribers

    COMMETABLE = ['Topic', 'Task']

    def initialize(project, creator, params, attachments)
      @subscribers_ids = params.delete(:subscribers) || []
      @creator = creator
      @project = project
      @attachments = attachments
      @params = params
    end

    def build
      comment = new_comment
      comment.creator = creator
      comment.subscribers = extract_subscribers
      comment.attachments = attachments
      comment
    end

    private

    attr_reader :project, :creator,
      :attachments, :params, :subscribers_ids

    def new_comment
      Comment.new(params.merge!(commentable: commentable))
    end

    def commentable
      if project.respond_to?(commentable_type)
        project.send(commentable_type).
          find_by_id(commentable_id)
      end
    end

    def commentable_id
      params[:commentable_id]
    end

    def commentable_type
      type = params[:commentable_type]
      COMMETABLE.include?(type) ? type.downcase.pluralize : ''
    end
  end
end

comments_controller.rb

class CommentsController < BaseController
  include AttachmentsConcern, Comments

  def create
    if comment_creator.create
      @comment = comment_creator.comment
    else
      render 'shared/error.coffee'
    end
  end

  def update
    authorize_access(@comment)
    @comment.attachments = build_attachments_from_tokens
    if @comment.update_attributes(comment_params)
      ActivityNotifier.new(@comment, current_user,
                               @comment.commentable.project,
                               I18n.t('activity.comment_update', subject: @comment.commentable.subject)).run
      flash[:notice] = 'Comment updated.'
    end
  end

  private

  def comment_params
    params.require(:comment).permit(*allowed_params)
  end

  def attachments_tokens
    params[:attachments]
  end
end

message.rb

class Message < ActiveRecord::Base

 include Commentable, Attachable, Subscribable,
    AdminPanel, Activitable

  belongs_to :project
  belongs_to :creator, class_name: User

  validates :subject, presence: true
  validates :creator, presence: true
  validates :project, presence: true
  validates :type, presence: true

  private

  concerning :MessageSearch do
    included do
      include Tire::Model::Search
      include Tire::Model::Callbacks

      mapping do
        indexes :subject
        indexes :body
        indexes :project_id, type: :integer
        indexes :created_at
      end

      def self.search(term, project_ids)
        tire.search(load: true) do
          query { string term }
          filter :terms, project_id: project_ids
          sort { by :created_at, :desc }
        end
      end
    end
  end
end

message_comment_spec.rb

require 'spec_helper'

feature 'message with comment' do
  include AccountHelpers, AttachmentHelpers

  before do
    sign_in
    expect_to_have_project
  end

  scenario 'can post comment with file attachment', :js do
    message = create(:message, project: @project)

    visit account_project_message_path(@account, @project, message)
    expect(message.comments.count).to eq(0)
    expect(page).to have_content(message.subject)
    expect(page).to have_content(message.body)
    expect(page).to have_selector("#comment_content")

    fill_in_t 'simple_form.labels.comment.content', with: 'awesome'
    upload_files
    click_button('Create Comment')

    comment = Comment.last
    expect(message.comments.count).to eq(1)
    expect(comment.attachments.count).to eq(1)
    expect(page).to have_content(comment.content)
  end

  scenario 'able to comment on message without attachment' do
    message = create(:message, project: @project)
    comment = create(:comment, commentable: message)

    visit account_project_message_path(@account, @project, message)

    expect(page).to have_content(comment.content)
    expect(message.comments.count).to eq(1)

    fill_in_t 'simple_form.labels.comment.content', with: 'new comment'
    click_button('Create Comment')


    message.reload
    comment = Comment.last
    expect(message.comments.count).to eq(2)
    expect(page).to have_content('new comment')

    activity = Activity.first
    expect(Activity.count).to eq(1)
    expect(activity.activitable).to eq(comment)
    expect(activity.meta).to eq("commented on #{message.subject}")
    expect(activity.url).to eq("#{account_project_message_url(@account, @project, message)}#comment-#{comment.id}")
  end

  scenario 'not able to comment on message' do
    message = create(:message, project: @project)
    visit account_project_message_path(@account, @project, message)

    fill_in_t 'simple_form.labels.comment.content', with: ''
    click_button('Create Comment')

    expect(message.comments.count).to eq(0)
  end

  scenario 'not able to comment if commentable is wrong', :js do
    message = create(:message, project: @project)
    visit account_project_message_path(@account, @project, message)
    fill_in_t 'simple_form.labels.comment.content', with: 'new comment'
    find("#comment_commentable_type", :visible => false).set 'Test'
    click_button('Create Comment')

    expect(message.comments.count).to eq(0)
  end

  scenario 'not able to comment if commentable id is wrong', :js do
    message = create(:message, project: @project)
    visit account_project_message_path(@account, @project, message)
    fill_in_t 'simple_form.labels.comment.content', with: 'new comment'
    find("#comment_commentable_id", :visible => false).set '110'
    click_button('Create Comment')

    expect(message.comments.count).to eq(0)
  end
end