As others have pointed out there are some features considered essential in this space that would be good additions to the code:

Stemming: (removing prefix/suffixes walked, walking, walker -> walk) The snowball library contains many language stemmers https://snowballstem.org

Stopping: removing many common words like the/and that almost every document will surely match anyway. Again, per language.

Relevance ranking: Generally some variant of TF/IDF like BM25. The book "Managing Gigabytes" is an excellent intro to the subject and information retrieval in general: https://people.eng.unimelb.edu.au/ammoffat/mg/

A Document/Term/Value model, this is how Lucence, Xapian, and other IR systems model the store. It's worth sticking with that same pattern.

Good luck!