module CP
	# Chipmunk Object
	# Makes it easier to manage complex objects that reference many primitive Chipmunk objects such as bodies shapes and constraints.
	# New composite objects simply need to include CP::Object and call #init_chipmunk_object(*objects) with the
	# composite and primitive Chipmunk objects that make up itself.
	module Object
		# Returns the list of primitive Chipmunk objects (bodies, shapes and constraints)
		# that this composite object references directly and indirectly.
		def chipmunk_objects
			if @chipmunk_objects
				return @chipmunk_objects
			else
				raise "This CP::Object (#{self.class}) did not call #init_chipmunk_object."
			end
		end
		
		private
		# Should be called during initialization of a CP::Object to set what primitive
		# and composite Chipmunk objects this object references.
		def init_chipmunk_object(*objs)
			bad_objs = objs.reject{|obj| obj.is_a?(CP::Object)}
			raise(ArgumentError, "The following objects: #{bad_objs.inspect} are not CP::Objects") unless bad_objs.empty?

			@chipmunk_objects = objs.inject([]){|sum, obj| sum + obj.chipmunk_objects}.uniq
		end
	end
	
	class Body
		include CP::Object

		def chipmunk_objects
			[self]
		end
		
		def add_to_space(space)
			space.add_body(self)
		end
		
		def remove_from_space(space)
			space.remove_body(self)
		end
	end
	
	module Shape
		include CP::Object
		
		def chipmunk_objects
			[self]
		end
		
		def add_to_space(space)
			space.add_shape(self)
		end
		
		def remove_from_space(space)
			space.remove_shape(self)
		end
	end
		
	module Constraint
		include CP::Object
		
		def chipmunk_objects
			[self]
		end
		
		def add_to_space(space)
			space.add_constraint(self)
		end
		
		def remove_from_space(space)
			space.remove_constraint(self)
		end
	end
	
	class Space
		def add_object(obj)
			obj.chipmunk_objects.each{|elt| elt.add_to_space(self)}
		end
		
		def add_objects(*objs)
			objs.each{|obj| add_object(obj)}
		end
		
		def remove_object(obj)
			obj.chipmunk_objects.each{|elt| elt.remove_from_space(self)}
		end
		
		def remove_objects(*objs)
			objs.each{|obj| remove_object(obj)}
		end
	end
end

require 'chipmunk'

# Create derived static objects that know to add themselves as static.
module CP
	class StaticBody < Body
		def initialize
			super(Float::INFINITY, Float::INFINITY)
		end
		
		def chipmunk_objects
			# return [] instead of [self] so the static body will not be added.
			[]
		end
	end
	
	module StaticShape
		include Shape
		
		class Circle < Shape::Circle
			include StaticShape
		end
		
		class Segment < Shape::Segment
			include StaticShape
		end
		
		class Poly < Shape::Poly
			include StaticShape
		end

		def add_to_space(space)
			space.add_static_shape(self)
		end
		
		def remove_from_space(space)
			space.remove_static_shape(self)
		end
	end
end