# frozen_string_literal: true

module Ops
  # Campioni latenza GET /up (edge → rails) per calcolo p95.
  class UpLatencyTracker
    REDIS_KEY = "ops:up_latency_ms"
    MAX_SAMPLES = -> { ENV.fetch("OPS_UP_LATENCY_SAMPLES", "60").to_i }

    class << self
      def record(latency_ms)
        return unless redis

        redis.pipelined do |pipe|
          pipe.lpush(REDIS_KEY, latency_ms.to_i)
          pipe.ltrim(REDIS_KEY, 0, MAX_SAMPLES.call - 1)
        end
      end

      def samples
        return [] unless redis

        redis.lrange(REDIS_KEY, 0, -1).map(&:to_i)
      end

      def sample_count
        samples.size
      end

      def p95
        sorted = samples.sort
        return nil if sorted.empty?

        index = [(sorted.size * 0.95).ceil - 1, 0].max
        sorted[index]
      end

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