#!/usr/bin/env ruby
 
require "active_model"
require "active_support/core_ext"

# Checks the date is after|before|not after|not before another date.
#
#     validates :next_birthday, date: { after: Time.now, not_after: 1.year.from_now }
#
# Use the <tt>:allow_nil</tt> key to skip validation in case the attribute value isn't set.
#
#     validates :next_birthday, date: { after: Time.now, allow_nil: true }
#
class DateValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    return if value.nil? && options[:allow_nil]
    value = value.try(:to_date)
    { after: :>, before: :<, not_after: :<=, not_before: :>= }.each do |key, check|
      if target = options[key].try(:to_date)
        record.errors.add attribute, :"#{ key }_date" unless value.try check, target
      end
    end
  end
end