sortable.rb

module Sortable
  def sortable(columns=nil)
    @@sortable ||= columns.with_indifferent_access
  end

  def order_condition(column='id', direction='desc')
    direction = %w[asc desc].include?(direction) ?  direction : 'desc'

    if sortable.keys.include?(column)
      column = sortable[column] 
    else
      column = column_names.include?(column) ? column : 'id'
    end

    "#{column} #{direction}"
  end
end