Maybe/app/models/time_series/value.rb

class TimeSeries::Value
  include Comparable

  attr_accessor :trend
  attr_reader :value, :date, :original

  def initialize(obj)
    @original = obj.fetch(:original, obj)

    if obj.is_a?(Hash)
      @date = obj[:date]
      @value = obj[:value]
    else
      @date = obj.date
      @value = obj.value
    end

    validate_input
  end

  def <=>(other)
    result = date <=> other.date
    result = value <=> other.value if result == 0
    result
  end

  private
    def validate_input
      raise ArgumentError, "Date is required" unless @date.is_a?(Date)
      raise ArgumentError, "Money or Numeric value is required" unless @value.is_a?(Money) || @value.is_a?(Numeric)
    end
end