"""Variant registry. `load("p1_surgical")` returns that folder's TeacherVariant
instance; `available()` lists the folders. No variant name is hardcoded anywhere —
a folder with a utils.py exporting `VARIANT` is automatically discoverable."""
import importlib.util
import importlib  # noqa: F401  (original re-exported both)
import os
import sys

from agents.variants.base import TeacherVariant  # noqa: F401  (re-exported for convenience)

_DIR = os.path.dirname(__file__)


def available():
    """Variant folder names (any subdir with a utils.py)."""
    return sorted(
        d for d in os.listdir(_DIR)
        if os.path.exists(os.path.join(_DIR, d, "utils.py"))
    )


def load(name):
    """Import agents/variants/<name>/utils.py and return its VARIANT() instance."""
    path = os.path.join(_DIR, name, "utils.py")
    if not os.path.exists(path):
        raise ValueError(f"unknown variant {name}; available: {available()}")
    spec = importlib.util.spec_from_file_location(f"agents.variants.{name}.utils", path)
    mod = importlib.util.module_from_spec(spec)
    sys.modules[spec.name] = mod
    spec.loader.exec_module(mod)
    return mod.VARIANT()