"""Select the active SearchBackend from config (SPEC §8.1, env SEARCH_BACKEND)."""

from __future__ import annotations

from app.config import get_settings
from app.search.base import SearchBackend
from app.search.pg import PgSearchBackend

_backend: SearchBackend | None = None


def get_search_backend() -> SearchBackend:
    """Return the process-wide SearchBackend (``pg`` in M0-M1, ``meili`` in M2)."""
    global _backend
    if _backend is None:
        which = get_settings().search_backend
        if which == "meili":
            # TODO(spec): Meilisearch backend lands in M2.
            raise NotImplementedError("meili backend is implemented in M2")
        _backend = PgSearchBackend()
    return _backend