Expirable cache module for i18n gem

i18n_expirable_cache.rb

module I18n
  module Backend
    # Expirable cache module that stores unpluralized and uninterpolated translations
    module ExpirableCache
      include Cache

      protected
      def fetch(*args}, &block)
        locale, key, options = *args
        options ||= {}
        count, scope, default, separator = options.values_at(:count, :scope, :default, :separator)
        separator ||= I18n.default_separator
        values = options.reject { |name, value| Base::RESERVED_KEYS.include?(name) }

        key = I18n.normalize_keys(locale, key, scope, separator)[1..-1].join(separator)

        key = [key, pluralization_key(locale, count)].join(separator) if count
        cache_store_key = cache_key(locale.to_s, key.to_s)

        # TODO figure out how to prevent db access if value is nil
        if entry = I18n.cache_store.read(cache_store_key)
          entry = pluralize(locale, entry, count)    if count
          entry = interpolate(locale, entry, values) if values
          entry
        else
          entry = lookup(locale, key, nil, options)
          I18n.cache_store.write(cache_store_key, entry)

          # Call the original translate method and return the translation
          block[*args]
        end
      end

      # TODO use built-in pluralization to support other pluralization rules
      def pluralization_key(locale, count)
        key = :zero if (count == 0 && pluralization_keys(locale).include?(:zero))
        key ||= count == 1 ? :one : :other
      end

      def pluralization_keys(locale)
        @pluralization_keys ||= {}
        @pluralization_keys[locale] ||= I18n.t('i18n.plural.keys', :locale => locale)
      end
    end
  end
end