array_validator.rb

require 'active_model/validator'

# Runs [Array] type validations
class ArrayValidator < ActiveModel::EachValidator
  # Checks if the value is an [Array] type
  #
  # Will sort, remove duplicates and blanks as well.
  #
  # Will validate the subset if passed options are present under `subset_of`.
  #
  # @return [ActiveModel::Base]
  def validate_each(record, attribute, value)
    unless value.is_a?(Array)
      return record.errors.add(attribute, :invalid)
    end

    value.map! do |val|
      StripAttributes.strip(val, collapse_spaces: true, replace_newlines: true)
    end

    value.reject!(&:blank?)

    value.map(&:downcase!) if options[:downcase]

    value.uniq!
    value.sort!

    return if options[:subset_of].blank?

    subset_of = options[:subset_of]
    subset_of = subset_of.call if subset_of.respond_to?(:call)

    invalid = value.map(&:to_s) - subset_of.map(&:to_s)

    return if invalid.blank?

    record.errors.add(attribute, :invalid_array, value: invalid.join(','))
  end
end