As far as I know, no one has fully implemented full-text search directly over Anna's Archive. Technically it’s feasible with tools like Meilisearch, Elasticsearch, or Lucene, but the main challenges are:
Converting all documents (PDFs, EPUBs, etc.) to clean plaintext.
Indexing at scale efficiently.
Managing potential legal issues.
Z-Library does something similar, but it’s smaller in scope and doesn't integrate AA’s full catalog.