visitor_stats.rb

class VisitorStats
  def initialize
    @redis = Redis.new
  end

  # every time there's a hit, increment a counter for the
  # day and week, and add the session id to a set of unique
  # vistitors for the day/week
  def hit(session_id)
    today = Date.today
    @redis.incr("hit_count:day:" + day_key(today))
    @redis.sadd("visitors:day:" + day_key(today), session_id)
    @redis.incr("hits_count:week:" + week_key(today))
    @redis.sadd("visitors:week:" + week_key(today), session_id)
  end

  def week_hits(date)
    @redis.get("hit_count:week:" + week_key(date))
  end

  def day_hits(date)
    @redis.get("hit_count:day:" + day_key(date))
  end

  def day_visitors(date)
    @redis.get("visitor_count:day:" + day_key(date)) || @redis.scard("visitors:day:" + day_key(date))
  end

  def week_visitors(date)
    @redis.get("visitor_count:week:" + week_key(date)) || @redis.scard("visitors:week:" + week_key(date))
  end

  # after the day is over, archive the visitor count and delete the set of session ids
  def archive_day(date)
    @redis.set("visitor_count:day:" + day_key(date), @redis.scard("visitors:day:" + day_key(date)))
    @redis.del("visitors:day:" + day_key(date))
  end

  # after the week is over, archive the visitor count and delete the set of session ids
  def archive_week(date)
    @redis.set("visitor_count:week:" + week_key(date), @redis.scard("visitors:week:" + week_key(date)))
    @redis.del("visitors:week:" + week_key(date))
  end

  private

  def day_key(date)
    date.strftime('%Y-%m-%d')
  end

  def week_key(date)
    date.strftime('%Y-%W')
  end
end