user.rb

ActiveAdmin.register User do
  controller do
    def update_resource(object, attributes)
      update_method = attributes.first[:password].present? ? :update_attributes : :update_without_password
      object.send(update_method, *attributes)
    end

    def scoped_collection
      User.
        joins('LEFT OUTER JOIN states ON states.user_id = users.id').
        select(%{
          users.*,
          count(distinct states.channel_id) as channels,
          count(distinct states.streamer_id) as streamers
        }).
        group('users.id')
    end
  end

  permit_params :email, :password, :password_confirmation, :confirm, role_ids: []

  index do
    selectable_column
    id_column

    column :email
    column :current_sign_in_at
    column :sign_in_count
    column :created_at

    column 'Roles' do |u|
      u.roles.map(&:name).join(', ')
    end

    column :channels
    column :streamers

    actions
  end

  filter :email
  filter :current_sign_in_at
  filter :sign_in_count
  filter :created_at

  show do
    attributes_table do
      row :id
      row :email
      row 'Roles' do |u|
        u.roles.map(&:name).join(', ')
      end

      row 'Watching' do |u|
        u.watching.presence && u.watching.map {|c| link_to c.name, admin_channel_path(c.id)}.join(', ').html_safe
      end

      row 'Streamers' do |u|
        u.streamers.presence && u.streamers.map {|s| link_to s.name, admin_streamer_path(s.id)}.join(', ').html_safe
      end

      row :sign_in_count
      row :current_sign_in_at
      row :last_sign_in_at
      row :confirmed_at
      row :confirmation_sent_at
      row :failed_attempts
      row :locked_at
      row :created_at
      row :updated_at
    end

    active_admin_comments
  end

  form do |f|
    f.inputs "Admin Details" do
      f.input :email
      f.input :password
      f.input :password_confirmation

      f.input :roles, as: :check_boxes, collection: Role.all

      unless f.object.confirmed?
        f.input :confirm, as: :boolean
      end
    end
    f.actions
  end

end