ruby 连続した日付をカウントする

Posted 2021-05-16

require 'active_support'
require 'active_support/core_ext'

current = Date.current.tomorrow
posted_days = [
  current.advance(days: 1),
  current.advance(days: 2),
  current.advance(days: 3),
  # - this day, not posted -
  current.advance(days: 5),
  current.advance(days: 6),
  current.advance(days: 7),
  current.advance(days: 8),
  # - this day, not posted -
  # - this day, not posted -
  current.advance(days:10),
  current.advance(days:11),
  current.advance(days:12),
  current.advance(days:13),
  current.advance(days:14),
  current.advance(days:15),
  # - this day, not posted -
  current.advance(days:17)
]

class StreakDays
  def initialize(posted_days)
    @posted_days = posted_days
    @count_stock = [0]
    calc_continuation_days
  end

  def longest_streak
    @count_stock.max
  end

  private

  def calc_continuation_days
    count_stock = [0]
    current = @posted_days.first
    @posted_days.each do |posted_day|
      if days_streak?(current, posted_day)
        count_stock[-1] += 1
      else
        count_stock << 1
      end
      current = posted_day
    end
    @count_stock = count_stock
  end

  def days_streak?(a, b)
    date_distance(a, b) == 1
  end

  def date_distance(current, next_day)
    (current - next_day).to_i.abs
  end
end

s = StreakDays.new(posted_days)
p s.longest_streak # => 6