Refactor compiler to separate impure and pure code about cryogen-core

[madstap]

I'm thinking that dealing with markups could be made better by:

• Removing the concept of a markup having a folder. #48
• Having the parser take a string instead of a reader.
• Moving the prefixing of local links to the compiler, as a pure function, one of the transformations done on a post.

[lacarmen]

Sounds like a good idea! The compiler namespace has become quite overgrown as new features were added and I think the three phases that you proposed is a nice, logical way to split all of that up. Perhaps this would a be a good time to take a look at #98 as well. Stasis sounds like a good library to use in Cryogen as well.

Is this something that you're interested in working on?

[madstap]

Yeah, I'm interested in working on this.

I could start by refactoring the way cryogen reads files as a relatively self-contained step. I'm thinking that there should be a function called read-markup-dirs that takes a collection of directories and a collection of markups and reads the posts/pages from all combinations thereof, encapsulating reading posts/pages. This would then make both #98 and #48 trivial to implement.

[lacarmen]

Yeah, I'm interested in working on this.

Awesome!

I could start by refactoring the way cryogen reads files as a relatively self-contained step.

That sounds like a good place to start. There's going to be a lot of code moving around for the full refactor so I definitely want this to be approached in an iterative fashion.