robworley/hstore_translate

module HstoreTranslate
  module Translates
    SUFFIX = "_translations"

    def translates(*attrs)
      include InstanceMethods

      class_attribute :translated_attrs
      alias_attribute :translated_attribute_names, :translated_attrs # Improve compatibility with the gem globalize
      self.translated_attrs = attrs

      attrs.each do |attr_name|
        serialize "#{attr_name}#{SUFFIX}", ActiveRecord::Coders::Hstore unless HstoreTranslate::native_hstore?

        define_method attr_name do
          read_hstore_translation(attr_name)
        end

        define_method "#{attr_name}=" do |value|
          write_hstore_translation(attr_name, value)
        end

        define_singleton_method "with_#{attr_name}_translation" do |value, locale = I18n.locale|
          quoted_translation_store = connection.quote_column_name("#{attr_name}#{SUFFIX}")
          where("#{quoted_translation_store} @> hstore(:locale, :value)", locale: locale, value: value)
        end
      end

      alias_method_chain :respond_to?, :translates
      alias_method_chain :method_missing, :translates
    end

    # Improve compatibility with the gem globalize
    def translates?
      included_modules.include?(InstanceMethods)
    end

    module InstanceMethods
      def disable_fallback(&block)
        toggle_fallback(enabled = false, &block)
      end

      def enable_fallback(&block)
        toggle_fallback(enabled = true, &block)
      end

      protected

      def hstore_translate_fallback_locales(locale)
        return if @enabled_fallback == false || !I18n.respond_to?(:fallbacks)
        I18n.fallbacks[locale]
      end

      def read_hstore_translation(attr_name, locale = I18n.locale)
        translations = send("#{attr_name}#{SUFFIX}") || {}
        translation  = translations[locale.to_s]

        if fallback_locales = hstore_translate_fallback_locales(locale)
          fallback_locales.each do |fallback_locale|
            t = translations[fallback_locale.to_s]
            if t && !t.empty? # differs from blank?
              translation = t
              break
            end
          end
        end

        translation
      end

      def write_hstore_translation(attr_name, value, locale = I18n.locale)
        translation_store = "#{attr_name}#{SUFFIX}"
        translations = send(translation_store) || {}
        send("#{translation_store}_will_change!") unless translations[locale.to_s] == value
        translations[locale.to_s] = value
        send("#{translation_store}=", translations)
        value
      end

      def respond_to_with_translates?(symbol, include_all = false)
        return true if parse_translated_attribute_accessor(symbol)
        respond_to_without_translates?(symbol, include_all)
      end

      def method_missing_with_translates(method_name, *args)
        translated_attr_name, locale, assigning = parse_translated_attribute_accessor(method_name)

        return method_missing_without_translates(method_name, *args) unless translated_attr_name

        if assigning
          write_hstore_translation(translated_attr_name, args.first, locale)
        else
          read_hstore_translation(translated_attr_name, locale)
        end
      end

      # Internal: Parse a translated convenience accessor name.
      #
      # method_name - The accessor name.
      #
      # Examples
      #
      #   parse_translated_attribute_accessor("title_en=")
      #   # => [:title, :en, true]
      #
      #   parse_translated_attribute_accessor("title_fr")
      #   # => [:title, :fr, false]
      #
      # Returns the attribute name Symbol, locale Symbol, and a Boolean
      # indicating whether or not the caller is attempting to assign a value.
      def parse_translated_attribute_accessor(method_name)
        return unless method_name =~ /\A([a-z_]+)_([a-z]{2})(=?)\z/

        translated_attr_name = $1.to_sym
        return unless translated_attrs.include?(translated_attr_name)

        locale    = $2.to_sym
        assigning = $3.present?

        [translated_attr_name, locale, assigning]
      end

      def toggle_fallback(enabled, &block)
        if block_given?
          old_value = @enabled_fallback
          begin
            @enabled_fallback = enabled
            yield
          ensure
            @enabled_fallback = old_value
          end
        else
          @enabled_fallback = enabled
        end
      end
    end
  end
end