Find a good graph library for Erlang

[oubiwann]

Goals:

• [x] Be able to perform basic graph theoretic operations: get neighbours, shortest path, reachability
• [x] Be able to generate visuals (probably only for debugging; maybe in-game? dunno ...)
• [x] Support file-based saves/exports
• [x] Support file-based loads/imports

It may be that we have to assemble from multiple bits ...

[oubiwann]

Possibilities:

• https://www.erlang.org/doc/man/digraph.html
• https://www.erlang.org/doc/man/digraph_utils.html
• https://github.com/jkrukoff/digraph_export
• https://github.com/jabarszcz/digraph_viz
• https://github.com/glejeune/erlang-graphviz
• https://github.com/fenollp/erlang-dot
• https://github.com/eproxus/grapherl
• https://github.com/erszcz/ecg

[oubiwann]

I think I'm leaning toward digraph. It will have to be in a gen_server, though, due to this:

Only the process that created the digraph is allowed to update it.

[oubiwann]

Over lunch, I have confirmed that the Erlang digraph library supports storing complex, nested data as the "label" on a graph, with the "vertex" of a new node being something as simple as an atom or a uuid string (list). I will update the ticket description with this decision.