Print a human-readable string for the interval between two times

prose_time_span.rb

require "time"

class ProseTimeSpan
  def initialize(time1, time2 = Time.now)
    @begin, @end = [time1, time2].map { Time.parse(it.to_s) }.sort
  end

  def to_i
    @end - @begin
  end

  def to_h
    Time.at(to_i).utc.then do
      {
        years: it.year - 1970,
        months: it.month - 1,
        days: it.day - 1,
        hours: it.hour,
        minutes: it.min,
        seconds: it.sec
      }
    end
  end

  def to_s
    to_h.filter_map do |units, qty|
      unless qty == 0
        unit = units.to_s
        unit.delete_suffix!("s") if qty == 1

        "#{qty} #{unit}"
      end
    end.join(", ")
  end

  include Comparable

  def <=>(other)
    to_i <=> other.to_i
  end
end