VS Code Conditional Snippets

I am looking to have some snippets listed conditionally in the VS Code IntelliSense for a particular language. I am considering creating an extension, intercepting the list of CompletionItems, and removing any snippets that do not satisfy my conditions based on languageId and settings/configuration I will contribute with the extension. I am looking for the simplest solution to accomplish this, but if I need a Language Server then so be it. If I can dynamically load a snippets file for a particular languageId then that would be even better. I just need a starting point from someone more familiar with the API. I haven't even found how to retrieve CompletionList to start the intercept -- I searched the API doc but found nothing but its object definition.