Patch Geokit to work with SQL Server

gistfile1.rb

module Geokit::ActsAsMappable::ClassMethods
  # Distance is selected as an aliased expression, and we want to be able to
  # use the alias in our order clause. SQL Server has no problem with that
  # normally, but when the adapter rewrites the query in order to support
  # pagination, it tries to use the alias. Unfortunately, the alias is invalid
  # in the rewritten query; we need to use the expression.
  #
  # https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/issues/198
  # 
  # This extension overrides the order method on the relation to inline
  # the expression when called with 'distance asc' or 'distance desc'.
  #
  # This patch may be rendered irrelevant if the SQL Server Adapter changes or
  # makes more robust its offset with order support. It will break if
  # geokit-rails3 stops storing the distance formula in an instance variable.
  def geo_scope_with_inlined_distance_expression_in_order(*args)
    arel = geo_scope_without_inlined_distance_expression_in_order(*args)
    if @distance_formula
      order_module = GeokitOrderByDistancePatch.
        order_by_distance_formula_module(@distance_formula)
      arel.extend(order_module)
    end
    arel
  end
  alias_method_chain :geo_scope, :inlined_distance_expression_in_order
end

module GeokitOrderByDistancePatch
  def self.order_by_distance_formula_module(distance_formula)
    Module.new do
      define_method(:order) do |order|
        if md = order.match(/^distance\s+(asc|desc)$/i)
          order = GeokitOrderByDistancePatch.
            order_by_distance_formula(distance_formula, md[1])
        end
        super(order)
      end
    end
  end

  def self.order_by_distance_formula(formula, direction)                                                                                                         
    distance = Arel::SqlLiteral.new(formula)
    arel_order_class =
      case direction
      when 'asc' then Arel::Nodes::Ascending
      when 'desc' then Arel::Nodes::Descending
      else
        raise ArgumentError("Invalid direction: #{direction}")
      end
    arel_order_class.new(distance)
  end
end