module Admin
  class MetricsStore
    HISTORY_KEY = "admin:metrics:history"
    NET_RX_KEY = "admin:metrics:net_rx"
    NET_TX_KEY = "admin:metrics:net_tx"
    HISTORY_LIMIT = 90

    class << self
      def redis
        @redis ||= Redis.new(url: ENV.fetch("REDIS_URL", "redis://localhost:6379/0"))
      rescue Redis::CannotConnectError
        nil
      end

      def push_sample(sample)
        return unless redis

        redis.lpush(HISTORY_KEY, sample.to_json)
        redis.ltrim(HISTORY_KEY, 0, HISTORY_LIMIT - 1)
      end

      def history
        return [] unless redis

        redis.lrange(HISTORY_KEY, 0, HISTORY_LIMIT - 1).map { |row| JSON.parse(row) }.reverse
      end

      def net_totals
        return { rx: nil, tx: nil } unless redis

        { rx: redis.get(NET_RX_KEY)&.to_i, tx: redis.get(NET_TX_KEY)&.to_i }
      end

      def save_net_totals(rx:, tx:)
        return unless redis

        redis.set(NET_RX_KEY, rx)
        redis.set(NET_TX_KEY, tx)
      end
    end
  end
end