# This was used to allow ActiveRecord classes using Single Table Inheritance
# to be considered unique across types.  We had a users table with a type field,
# and noticed 'Administrator' had values that clashed with 'User'.
#

module ActiveRecord
  module Validations
    module ClassMethods
      
      def validates_uniqueness_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken], :scope_to_base => false }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        validates_each(attr_names,configuration) do |record, attr_name, value|
          condition_sql = "#{attr_name} #{attribute_condition(value)}"
          condition_params = [value]
          if scope = configuration[:scope]
            Array(scope).map do |scope_item|
              scope_value = record.send(scope_item)
              condition_sql << " AND #{scope_item} #{attribute_condition(scope_value)}"
              condition_params << scope_value
            end
          end
          unless record.new_record?
            condition_sql << " AND #{record.class.primary_key} <> ?"
            condition_params << record.send(:id)
          end
          
          find_with_class = (:scope_to_base) ? class_name_of_active_record_descendant(record.class).constantize : record.class
          if find_with_class.find(:first, :conditions => [condition_sql, *condition_params])
            record.errors.add(attr_name, configuration[:message])
          end
        end
      end
            
    end
  end
end