module I18n::Backend::Cache

def _fetch(cache_key, &block)
  result = I18n.cache_store.read(cache_key)
  return result unless result.nil?
  result = catch(:exception, &block)
  I18n.cache_store.write(cache_key, result) unless result.is_a?(Proc)
  result
end

def cache_key(locale, key, options)
  # This assumes that only simple, native Ruby values are passed to I18n.translate.
  "i18n/#{I18n.cache_namespace}/#{locale}/#{digest_item(key)}/#{digest_item(options)}"
end

def digest_item(key)
  I18n.cache_key_digest ? I18n.cache_key_digest.hexdigest(key.to_s) : key.to_s.hash
end

def fetch(cache_key, &block)
  result = _fetch(cache_key, &block)
  throw(:exception, result) if result.is_a?(MissingTranslation)
  result = result.dup if result.frozen? rescue result
  result
end

def translate(locale, key, options = EMPTY_HASH)
  I18n.perform_caching? ? fetch(cache_key(locale, key, options)) { super } : super
end