"""Method registry for the MacroLens unified API.

Concrete method classes register themselves via the :func:`register`
decorator. The orchestrator (``experiments/run_all.py``) and the public
API (``macrolens.list_methods``, ``macrolens.methods``) read from
:data:`ALL_METHODS`.

Usage:

    from .base import Method, _JoblibSaveMixin
    from ._registry import register
    from ._config import LightGBMConfig

    @register(name="lightgbm", family="classical",
              tasks={"T1","T2","T3","T4","T5","T6","T7"},
              config_class=LightGBMConfig)
    class LightGBMRegressor(_JoblibSaveMixin, Method):
        ...

This avoids the historical pattern of hand-maintaining a `__init__.py`
re-export list that drifted from the actual class set.
"""

from __future__ import annotations

from typing import TYPE_CHECKING, Iterable

if TYPE_CHECKING:
    from .base import Method
    from ._config import MethodConfig


# Single source of truth: name -> concrete Method class
ALL_METHODS: dict[str, type["Method"]] = {}


def register(
    *,
    name: str,
    family: str,
    tasks: Iterable[str],
    config_class: type["MethodConfig"],
):
    """Decorator that registers a concrete Method subclass.

    Sets the four class-level attributes (``name``, ``family``, ``tasks``,
    plus a ``_config_class`` private hook used by ``default_config``) and
    inserts the class into :data:`ALL_METHODS`.
    """
    tasks_frozen = frozenset(tasks)

    def _decorator(cls):
        cls.name = name
        cls.family = family
        cls.tasks = tasks_frozen
        cls._config_class = config_class

        if not hasattr(cls, "default_config") or cls.default_config is _undefined_default_config:
            @classmethod
            def default_config(cls_inner):
                return cls_inner._config_class()
            cls.default_config = default_config  # type: ignore[assignment]

        if name in ALL_METHODS:
            raise ValueError(f"method '{name}' already registered")
        ALL_METHODS[name] = cls
        return cls

    return _decorator


def _undefined_default_config(cls):  # pragma: no cover -- placeholder sentinel
    raise NotImplementedError


def list_methods(*, family: str | None = None, task: str | None = None) -> list[str]:
    """Return registered method names, optionally filtered by family or task."""
    out = []
    for n, cls in sorted(ALL_METHODS.items()):
        if family is not None and cls.family != family:
            continue
        if task is not None and task not in cls.tasks:
            continue
        out.append(n)
    return out


def get(name: str) -> type["Method"]:
    """Lookup a registered method class by name."""
    if name not in ALL_METHODS:
        raise KeyError(
            f"method '{name}' not registered; "
            f"available: {sorted(ALL_METHODS)}"
        )
    return ALL_METHODS[name]