Well, what I'm looking for is a diagram that explains how resources works. It's hard to "debug" the code to see which page is called and what does every page do.
I assume you wish to develop a resource type rather than a new module. Perhaps you could check the existing resource types (text page, web page etc.) in order to discover how resource types work.
As you've found, resource types are not yet documented. Perhaps you would consider making a start?