# File lib/omniauth/builder.rb, line 47
    def provider(klass, *args, &block)
      if klass.is_a?(Class)
        middleware = klass
      else
        begin
          middleware = OmniAuth::Strategies.const_get(OmniAuth::Utils.camelize(klass.to_s).to_s)
        rescue NameError
          raise(LoadError.new("Could not find matching strategy for #{klass.inspect}. You may need to install an additional gem (such as omniauth-#{klass})."))
        end
      end

      args.last.is_a?(Hash) ? args.push(options.merge(args.pop)) : args.push(options)
      use middleware, *args, &block
    end