module AbAdmin
  module CarrierWave
    class FileSizeValidator < ActiveModel::EachValidator
      MESSAGES  = { is: :wrong_size, minimum: :size_too_small, maximum: :size_too_big }.freeze
      CHECKS    = { is: :==, minimum: :>=, maximum: :<= }.freeze

      DEFAULT_TOKENIZER = lambda { |value| value.split(//) }
      RESERVED_OPTIONS  = [:minimum, :maximum, :within, :is, :tokenizer, :too_short, :too_long]

      def initialize(options)
        if range = (options.delete(:in) || options.delete(:within))
          raise ArgumentError, ':in and :within must be a Range' unless range.is_a?(Range)
          options[:minimum], options[:maximum] = range.begin, range.end
          options[:maximum] -= 1 if range.exclude_end?
        end

        super
      end

      def check_validity!
        keys = CHECKS.keys & options.keys

        if keys.empty?
          raise ArgumentError, 'Range unspecified. Specify the :within, :maximum, :minimum, or :is option.'
        end

        keys.each do |key|
          value = options[key]

          unless value.is_a?(Integer) && value >= 0
            raise ArgumentError, ":#{key} must be a nonnegative Integer"
          end
        end
      end

      def validate_each(record, attribute, value)
        raise(ArgumentError, 'A CarrierWave::Uploader::Base object was expected') unless value.kind_of? ::CarrierWave::Uploader::Base
        
        value = (options[:tokenizer] || DEFAULT_TOKENIZER).call(value) if value.kind_of?(String)

        CHECKS.each do |key, validity_check|
          next unless check_value = options[key]

          value ||= [] if key == :maximum

          value_size = value.size
          next if value_size.send(validity_check, check_value)

          errors_options = options.except(*RESERVED_OPTIONS)
          errors_options[:file_size] = help.number_to_human_size check_value

          default_message = options[MESSAGES[key]]
          errors_options[:message] ||= default_message if default_message

          record.errors.add(attribute, MESSAGES[key], errors_options)
        end
      end
      
      def help
        Helper.instance
      end

      class Helper
        include Singleton
        include ActionView::Helpers::NumberHelper
      end
    end
  end
end