gistfile1.txt

  def calculate_response_time
    res = Message.connection.execute("
      SELECT DATE(q2.created_at AT TIME ZONE '-08:00'), q2.response_time, q2.id, q2.customer_id FROM
        (SELECT q1.*, (LEAD(created_at) OVER (PARTITION BY customer_id ORDER BY created_at) - q1.created_at) AS response_time FROM
          (SELECT m.*, LEAD(direction) OVER (PARTITION BY customer_id ORDER BY created_at) AS next_direction FROM messages m
            WHERE company_id = #{self.id} AND via_api = false AND mass_message_id IS NULL) AS q1
        WHERE q1.direction <> q1.next_direction AND q1.next_direction IS NOT NULL) AS q2
      WHERE q2.direction = 'received' ORDER BY created_at
    ")
  end