three_paycheck_calculator.rb

require 'date'

class ThreePaycheckCalculator

	attr_reader :first_payday, :pay_interval, :number_of_paydays, :pay_days

	def initialize(first_payday, pay_interval: 14, number_of_paydays: 100)
		@first_payday = first_payday
		@pay_interval = pay_interval
		@number_of_paydays = number_of_paydays
		calculate
		self
	end

	def calculate
		@pay_days ||= (0..100).map{ |i| first_payday + (i * pay_interval) }
	end

	def three_payday_months
		if @three_payday_months
			@three_payday_months
		else
			pay_months = pay_days.map{ |pd| [pd.year, pd.month] }
			@three_payday_months = pay_months.select{ |m| pay_months.count(m) > 2 }.map{ |pm| Date.new(*pm) }.uniq
		end
	end

	def report
		to_s
	end

	def to_s
		three_payday_months.map{ |pm|
			"#{pm.strftime("%b %Y")}\n\t #{pay_days.select{ |pd| pd.year == pm.year && pd.month == pm.month }.join("\n\t")}"
		}.join("\n")
	end		

end