Combining multiple custom languages

Hello,

the following has given me a bit of a headache. Basically, I'm trying to combine multiple custom languages. Let's call them custom language A, B and C.

The Goal

Custom Language A

May contain B and C.

Example

prototype {
  test1 = ${FRAGMENT_OF_CUSTOM_LANUGAGE_C}
  test2 = afx`
    FRAGMENT_OF_CUSTOM_LANUGAGE_B
  `
}

Custom Language B

Similar to JSX, based on HTML. May contain C.

Example

<div>{FRAGMENT_OF_CUSTOM_LANGUAGE_C}</div>

Custom Language C

Simple expression language. Has completion and other features, so reusability is desired.

Current Situation

B is not implemented as a custom language, yet. It is just injected HTML. This works for now.

C is extracted from A as a custom language with it's own lexer/parser. Doesn't work yet.

Possible Solutions

1. Using MultiplePsiFilesPerDocumentFileViewProvider

This would be the ideal solution, if my understanding is right. Should I use AbstractTemplateLanguageFileViewProvider for language A?

The parser for language A needs to return a token for the content of language B and C.

The parser for language B needs to return a token for the surrounding content, which is not part of the language and a token for the content of language C.

The parser for language C needs to return a token for the surrounding content, which is not part of the language.

Did I get this right?

2. Using language injection

I feel like this is not an ideal solution. Doesn't have the same degree of integration and might affect performance (?)

I understand that this is a rather complex question, so any feedback is very much appreciated.

What would be your approach to this? Am I on the right track?

The current state of things can be found here: https://github.com/cvette/intellij-neos/pull/37/files