require 'facet/macro'

module Og

# Attach list/ordering methods to the enchanted class.

module Orderable

	def self.append_dynamic_features(base, options)
		o = { 
			:position => 'position', 
			:type => Fixnum, 
		}
		o.update(options) if options

		if o[:scope].is_a?(Symbol) && o[:scope].to_s !~ /_oid$/		
			o[:scope] = "#{o[:scope]}_oid".intern 
		end

		position = o[:position]
		scope = o[:scope]

		if scope
			if scope.is_a?(Symbol)
				scope = %{(#{scope} ? "#{scope} = \#{@#{scope}}" : "#{scope} IS NULL")}
			end
		
			cond = 'condition => ' + scope
			cond_and = ':condition => ' + scope + ' + " AND " +'
		else
			cond = ':condition => nil'
			cond_and = ':condition => '
		end		

		code = %{		
			property :#{position}, #{o[:type]}

			pre "add_to_bottom", :on => :og_insert	
			pre "decrement_position_of_lower_items", :on => :og_delete
			
			def move_higher
				if higher = higher_item
					#{base}.transaction do
						higher.increment_position
						decrement_position
					end
				end
			end

			def move_lower
				if lower = lower_item
					#{base}.transaction do
						lower.decrement_position
						increment_position
					end
				end
			end

			def move_to_top
				#{base}.transaction do
					increment_position_of_higher_items
					set_top_position
				end
			end

			def move_to_bottom
				#{base}.transaction do
					decrement_position_of_lower_items
					set_bottom_position
				end											
			end

			def move_to
			end

			def add_to_top
				increment_position_of_all_items
			end

			def add_to_bottom
				@#{position} = bottom_position + 1
			end

			def add_to
			end

			def higher_item
				#{base}.one(#{cond_and}"#{position}=\#\{@#{position} - 1\}")
			end
			alias_method :previous_item, :higher_item

			def lower_item
				#{base}.one(#{cond_and}"#{position}=\#\{@#{position} + 1\}")
			end
			alias_method :next_item, :lower_item

			def top_item
			end
			alias_method :first_item, :top_item

			def bottom_item
				#{base}.one(#{cond}, :order => "#{position} DESC", :limit => 1)
			end
			alias_method :last_item, :last_item

			def top?
				@#{position} == 1
			end
			alias_method :first?, :top?

			def bottom?
				@#{position} == bottom_position
			end
			alias_method :last?, :bottom?

			def increment_position
				@#{position} += 1
				update(:#{position})
			end
		
			def decrement_position
				@#{position} -= 1
				update(:#{position})
			end

			def bottom_position
				item = bottom_item
				item ? item.#{position} : 0
			end

			def set_top_position
				@#{position} = 1
				update(:#{position})
			end

			def set_bottom_position
				@#{position} = bottom_position + 1
				update(:#{position})
			end

			def increment_position_of_higher_items
				#{base}.update_property("#{position}=(#{position} + 1)", #{cond_and}"#{position} < \#\{@#{position}\}")
			end

			def increment_position_of_all_items
				#{base}.update_property("#{position}=(#{position} + 1)", #{cond})
			end
			
			def decrement_position_of_lower_items
				#{base}.update_property("#{position}=(#{position} - 1)", #{cond_and}"#{position} > \#\{@#{position}\}")
			end
		}		
		
		base.module_eval(code)
	end
	
end

end 

# * George Moschovitis <gm@navel.gr>