class ProblemUpdaterCache
  def initialize(problem, notice=nil)
    @problem = problem
    @notice = notice
  end
  attr_reader :problem

  ##
  # Update cache information about child associate to this problem
  #
  # update the notices count, and some notice informations
  #
  # @return [ Problem ] the problem with this update
  #
  def update
    update_notices_count
    update_notices_cache
    problem
  end

  private

  def update_notices_count
    if @notice
      problem.inc(notices_count: 1)
    else
      problem.update_attribute(
        :notices_count, problem.notices.count
      )
    end
  end

  ##
  # Update problem statistique from some notice information
  #
  def update_notices_cache
    first_notice = notices.first
    last_notice = notices.last
    notice ||= @notice || first_notice

    attrs = {}
    attrs[:first_notice_at] = first_notice.created_at if first_notice
    attrs[:last_notice_at] = last_notice.created_at if last_notice
    attrs.merge!(
      :message     => notice.message,
      :where       => notice.where,
      :messages    => attribute_count(:message, messages),
      :hosts       => attribute_count(:host, hosts),
      :user_agents => attribute_count(:user_agent_string, user_agents)
    ) if notice
    problem.update_attributes!(attrs)
  end

  def notices
    @notices ||= @notice ? [@notice].sort(&:created_at) : problem.notices.order_by([:created_at, :asc])
  end

  def messages
    @notice ? problem.messages : {}
  end

  def hosts
    @notice ? problem.hosts : {}
  end

  def user_agents
    @notice ? problem.user_agents : {}
  end

  private

    def attribute_count(value, init)
      init.tap do |counts|
        notices.each do |notice|
          counts[attribute_index(notice.send(value))] ||= {
            'value' => notice.send(value),
            'count' => 0
          }
          counts[attribute_index(notice.send(value))]['count'] += 1
        end
      end
    end

    def attribute_index(value)
      @attributes_index ||= {}
      @attributes_index[value.to_s] ||= Digest::MD5.hexdigest(value.to_s)
    end
end