RecursionSchemeSandbox
Stripping away all the Protobuf specific details, this project demonstrates the essence of the problem that I'm running into.
What this project tries to do:
In the spirit of Skeuomorph, we take an invariant Tree of strings, and read it as a TreeF that can work with Droste's recursion scheme library. We then try to Print the Tree.
Tree ==(Coalgebra: parse stuff)==> TreeF ==(Algebra: print stuff)==> String
Seems simple, however, there is a catch! Our original Tree has a boolean flag on its terminal nodes which indicates whether the Node's value can be repeated. Our TreeF schema has two types that one of these original Nodes can be transformed into: a StringNodeF() or a RepeatNode(_). We'd like our RepeatNodes to be printed as a List[String] to represent this.
To see what happens:
Run the Playground app, it will either Stack overflow or Print out an string of Eithers, with no repeated nodes represented. Switch the order of the case statement in the fromTree coalgebra to see the other behavior.
Constraints:
We can't, to my knowlege, change the structure of the original Tree, that would be controlled by Protobuf itself. But we have free reign in other parts.