class ActiveAdmin::PunditAdapter

def authorized?(action, subject = nil)
  policy = retrieve_policy(subject)
  action = format_action(action, subject)
  policy.respond_to?(action) && policy.public_send(action)
end

def default_policy(user, subject)
  default_policy_class.new(user, subject)
end

def default_policy_class
  ActiveAdmin.application.pundit_default_policy && ActiveAdmin.application.pundit_default_policy.constantize
end

def format_action(action, subject)
  # https://github.com/elabs/pundit/blob/master/lib/generators/pundit/install/templates/application_policy.rb
  case action
  when Auth::CREATE  then :create?
  when Auth::UPDATE  then :update?
  when Auth::READ    then subject.is_a?(Class) ? :index? : :show?
  when Auth::DESTROY then subject.is_a?(Class) ? :destroy_all? : :destroy?
  else "#{action}?"
  end
end

def namespace(object)
  if ActiveAdmin.application.pundit_policy_namespace
    [ActiveAdmin.application.pundit_policy_namespace.to_sym, object]
  else
    object
  end
end

def retrieve_policy(subject)
  case subject
  when nil   then Pundit.policy!(user, namespace(resource))
  when Class then Pundit.policy!(user, namespace(subject.new))
  else Pundit.policy!(user, namespace(subject))
  end
rescue Pundit::NotDefinedError => e
  if default_policy_class
    default_policy(user, subject)
  else
    raise e
  end
end

def scope_collection(collection, action = Auth::READ)
  # scoping is appliable only to read/index action
  # which means there is no way how to scope other actions
  Pundit.policy_scope!(user, namespace(collection))
rescue Pundit::NotDefinedError => e
  if default_policy_class && default_policy_class.const_defined?(:Scope)
    default_policy_class::Scope.new(user, collection).resolve
  else
    raise e
  end
end