How to build state machine workflow through SharePoint designer

Declarative workflow doesn't support state machine workflow, actually, there is even no "loop" statements. So is it possible to build a state machine workflow through SharePoint designer? My answer is: Yes! (Well......with the help from InfoPath or Web Page or other workflow)

Many people did it with a secondary list (attached with a secondary workflow). It works but is quite complex. My solution is different.

Let's say we need a state machine workflow as below:

Previous State	Event	New State
(empty)	eventInitWorkflow	Submitted
Draft	Submitted	Submitted
Submitted	InvoiceOwner Submitted	InvoiceOwnerSubmitted
InvoiceOwnerSubmitted	InvoiceOwner Approved	InvoiceOwnerApproved
InvoiceOwnerApproved	CostCentre Approved	CostCentreApproved

What we need to do is simple: store the "Previous State" and the "New State" in current list or form library, so we can figure out which event is fired.  These "States" is changed by InfoPath form or Web form or other workflow attached with Tasks list.

This workflow needs to be triggered when the list data (or form data) is changed (or submitted), and it doesn't need to wait to collect any further user input.   Below is an example.

It's not as intuitive as visual studio workflow diagram, but, it can be built without coding!