splasher.rb

require "test_helper"

class Splasher
  attr_reader :total, :range, :per, :mod, :unit, :unit_total, :start_at

  def initialize(total:, range:, unit: :hour, per: :hour, start_at: DateTime.now)
    @total = total
    @range = range
    @unit = unit
    @per = per
    @start_at = start_at
    @mod = total % range_steps
    @unit_total = (total / range_steps).floor
  end

  def sequence
    seq = {}
    1.upto(range_steps) do |n|
      seq_total = (n <= mod) ? unit_total + 1 : unit_total
      seq[start_at.send(:-, (n - 1).send(per))] = seq_total
    end
    seq
  end

  private
  def seconds_timerange 
    @seconds_timerange ||= start_at.to_time.utc - range.send(unit).ago
  end

  def range_steps
    @range_steps ||= (seconds_timerange / 1.send(per)).round
  end
end

class DistributeTimeRangeTest < ActiveSupport::TestCase
  setup do
    travel_to Time.zone.local(2021, 11, 17, 12, 0, 0)
  end

  teardown do
    travel_back
  end 

  test "distribute over last 24 hours" do
    sequence = Splasher.new(total: 100, range: 24, per: :hour).sequence
    assert_equal expected_total_100_per_hour, sequence
  end

  test "distrbute over last 3 days, per hour" do
    sequence = Splasher.new(total: 100, range: 3, unit: :day, per: :hour).sequence
    assert_equal expected_total_100_last_3_days_per_hour, sequence
  end

  def expected_total_100_per_hour
    d = DateTime.now
    e = {}
    e[d] = 5
    e[d-1.hour] = 5
    e[d-2.hours] = 5
    e[d-3.hours] = 5
    e[d-4.hours] = 4
    e[d-5.hours] = 4
    e[d-6.hours] = 4
    e[d-7.hours] = 4
    e[d-8.hours] = 4
    e[d-9.hours] = 4
    e[d-10.hours] = 4
    e[d-11.hours] = 4
    e[d-12.hours] = 4
    e[d-13.hours] = 4
    e[d-14.hours] = 4
    e[d-15.hours] = 4
    e[d-16.hours] = 4
    e[d-17.hours] = 4
    e[d-18.hours] = 4
    e[d-19.hours] = 4
    e[d-20.hours] = 4
    e[d-21.hours] = 4
    e[d-22.hours] = 4
    e[d-23.hours] = 4
    e
  end

  def expected_total_100_last_3_days_per_hour
    d = DateTime.now
    e = {}
    e[d] = 2
    e[d-1.hour] = 2
    e[d-2.hours] = 2
    e[d-3.hours] = 2
    e[d-4.hours] = 2
    e[d-5.hours] = 2
    e[d-6.hours] = 2
    e[d-7.hours] = 2
    e[d-8.hours] = 2
    e[d-9.hours] = 2
    e[d-10.hours] = 2
    e[d-11.hours] = 2
    e[d-12.hours] = 2
    e[d-13.hours] = 2
    e[d-14.hours] = 2
    e[d-15.hours] = 2
    e[d-16.hours] = 2
    e[d-17.hours] = 2
    e[d-18.hours] = 2
    e[d-19.hours] = 2
    e[d-20.hours] = 2
    e[d-21.hours] = 2
    e[d-22.hours] = 2
    e[d-23.hours] = 2
    e[d-24.hours] = 2
    e[d-25.hours] = 2
    e[d-26.hours] = 2
    e[d-27.hours] = 2
    e[d-28.hours] = 1
    e[d-29.hours] = 1
    e[d-30.hours] = 1
    e[d-31.hours] = 1
    e[d-32.hours] = 1
    e[d-33.hours] = 1
    e[d-34.hours] = 1
    e[d-35.hours] = 1
    e[d-36.hours] = 1
    e[d-37.hours] = 1
    e[d-38.hours] = 1
    e[d-39.hours] = 1
    e[d-40.hours] = 1
    e[d-41.hours] = 1
    e[d-42.hours] = 1
    e[d-43.hours] = 1
    e[d-44.hours] = 1
    e[d-45.hours] = 1
    e[d-46.hours] = 1
    e[d-47.hours] = 1
    e[d-48.hours] = 1
    e[d-49.hours] = 1
    e[d-50.hours] = 1
    e[d-51.hours] = 1
    e[d-52.hours] = 1
    e[d-53.hours] = 1
    e[d-54.hours] = 1
    e[d-55.hours] = 1
    e[d-56.hours] = 1
    e[d-57.hours] = 1
    e[d-58.hours] = 1
    e[d-59.hours] = 1
    e[d-60.hours] = 1
    e[d-61.hours] = 1
    e[d-62.hours] = 1
    e[d-63.hours] = 1
    e[d-64.hours] = 1
    e[d-65.hours] = 1
    e[d-66.hours] = 1
    e[d-67.hours] = 1
    e[d-68.hours] = 1
    e[d-69.hours] = 1
    e[d-70.hours] = 1
    e[d-71.hours] = 1
    e
  end
end