discourse/app/serializers/post_stream_serializer_mixin.rb

require_dependency 'gap_serializer'
require_dependency 'post_serializer'
require_dependency 'timeline_lookup'

module PostStreamSerializerMixin

  def self.included(klass)
    klass.attributes :post_stream
    klass.attributes :timeline_lookup
  end

  def post_stream
    result = { posts: posts, stream: object.filtered_post_ids }
    result[:gaps] = GapSerializer.new(object.gaps, root: false) if object.gaps.present?
    result
  end

  def timeline_lookup
    TimelineLookup.build(object.filtered_post_stream)
  end

  def posts
    @posts ||= begin
      (object.posts || []).map do |post|
        post.topic = object.topic

        serializer = PostSerializer.new(post, scope: scope, root: false)
        serializer.add_raw = true if @options[:include_raw]
        serializer.topic_view = object

        serializer.as_json
      end
    end
  end

end