How to make a file open in text-editor if no default application is selected?

I use files with various extensions, some of which are even prefixed, like "c3.filename", "s.filename", etc. On clicking a file, I want it to open in my default text editor (emacs) if no specific application is selected. As of now, I have to select open-with on right-click every time I want to open the file in the text editor. I could not a find a satisfactory answer for it in the questions/answers posted earlier for extensionless files and using automator.