module TimeClock
  class Calendar
    class OverlappingShiftError < ArgumentError; end

    attr_reader :shifts

    def initialize
      @shifts = []
    end

    def add_shift(new_shift)
      starting_shift_count = @shifts.size
      @shifts.each_with_index do |shift, i|
        raise OverlappingShiftError if new_shift.overlaps?(shift)
        break @shifts.insert(i, new_shift) if shift.start_time > new_shift.end_time
      end
      @shifts << new_shift unless @shifts.size > starting_shift_count
      @shifts
    end

  end
end