class Pagy::Calendar::Quarter

def assign_unit_vars
  super
  @initial = @starting.beginning_of_quarter
  @final   = @ending.next_quarter.beginning_of_quarter
  @last    = (months_in(@final) - months_in(@initial)) / 3
  @from    = starting_time_for(@page)
  @to      = @from.next_quarter
end

def label_for(page, opts = {})
  starting_time = starting_time_for(page.to_i)  # page could be a string
  opts[:format] = (opts[:format] || @vars[:format]).gsub('%q') { (starting_time.month / 3.0).ceil }
  localize(starting_time, opts)
end

def months_in(time)
  (time.year * 12) + time.month
end

def page_offset_at(time)
  (months_in(time.beginning_of_quarter) - months_in(@initial)) / 3
end

def starting_time_for(page)
  @initial.months_since(time_offset_for(page) * 3)
end