"""Registry: lazy-loads data adapter instances per env."""

from .base import DataAdapter


def get_adapter(env, name: str) -> DataAdapter:
    """Return a data adapter by short name. Cached per request via env.context."""
    cache = env.context.get('_fusion_data_adapter_cache')
    if cache is None:
        cache = {}
    if name not in cache:
        cls = _ADAPTERS.get(name)
        if cls is None:
            raise KeyError(f"Unknown data adapter: {name!r}. Known: {list(_ADAPTERS)}")
        cache[name] = cls(env)
    return cache[name]


# Populated as adapter classes are added (Tasks 9, 10, 11).
_ADAPTERS: dict[str, type[DataAdapter]] = {}


def register_adapter(name: str, cls: type[DataAdapter]) -> None:
    """Register an adapter class. Call from each adapter module at import time."""
    _ADAPTERS[name] = cls