make sim use proper OOP

sim/port.lua

@@ -36,7 +36,7 @@ end
 function Port.setstate(port, state)
 	if state ~= port.state then
 		port.state = state
-		Simulation.queuegroup(port.sim, port.group)
+		Simulation.queuegroup(Port.getsim(port), port.group)
 	end
 end
 
@@ -44,46 +44,50 @@ function Port.setinputstate(port, state)
 	if state ~= port.state then
 		port.state = state
 		if port.causeupdate then
-			Simulation.queuegate(port.sim, port.gate)
+			Simulation.queuegate(Port.getsim(port), port.gate)
 		end
 	end
 end
 
-function Port.getconnectionposition(self)
-	local offset = PortDirections[self.direction]
-	return {self.position[1]+offset[1], self.position[2]+offset[2], self.position[3]+offset[3]}
+function Port.getconnectionposition(port)
+	local offset = PortDirections[port.direction]
+	return {port.position[1]+offset[1], port.position[2]+offset[2], port.position[3]+offset[3]}
 end
 
-function Port.isrising(self)
-	if self.group == nil then
+function Port.isrising(port)
+	if port.group == nil then
 		return false
 	end
-	return self.group.state and (self.group.updatetick == self.sim.currenttick)
+	return port.group.state and (port.group.updatetick == Port.getsim(port).currenttick)
 end
 
-function Port.isfalling(self)
-	if self.group == nil then
+function Port.isfalling(port)
+	if port.group == nil then
 		return false
 	end
-	return self.group.state == false and (self.group.updatetick == self.sim.currenttick)
+	return port.group.state == false and (port.updatetick == Port.getsim(port).currenttick)
 end
 
-function Port.setgate(self, gate)
-	self.gate = gate
+function Port.setgate(port, gate)
+	port.gate = gate
 end
 
-function Port.setgroup(self, group)
-	self.group = group
+function Port.setgroup(port, group)
+	port.group = group
 end
 
-function Port.getgroup(self)
-	return self.group
+function Port.getgroup(port)
+	return port.group
 end
 
-function Port.gettype(self)
-	return self.type
+function Port.gettype(port)
+	return port.type
 end
 
-function Port.getstate(self)
-	return self.state
+function Port.getstate(port)
+	return port.state
+end
+
+function Port.getsim(port)
+	return port.sim
 end