module Middleman::CoreExtensions::Extensions::InstanceMethods

def activate(ext, options={}, &block)
  ext_module = if ext.is_a?(Module)
    ext
  else
    ::Middleman::Extensions.load(ext)
  end
  if ext_module.nil?
    logger.error "== Unknown Extension: #{ext}"
  else
    logger.debug "== Activating: #{ext}"
    if ext_module.instance_of? Module
      extensions[ext] = self.class.register(ext_module, options, &block)
    elsif ext_module.instance_of?(Class) && ext_module.ancestors.include?(::Middleman::Extension)
      if ext_module.supports_multiple_instances?
        extensions[ext] ||= {}
        key = "instance_#{extensions[ext].keys.length}"
        extensions[ext][key] = ext_module.new(self.class, options, &block)
      else
        if extensions[ext]
          logger.error "== #{ext} already activated."
        else
          extensions[ext] = ext_module.new(self.class, options, &block)
        end
      end
    end
  end
end