"""极简注册表：按名字注册 / 构建模型、数据集等组件。"""

from __future__ import annotations

import inspect
from collections.abc import Callable, Iterator
from typing import Any, TypeVar

T = TypeVar("T")


class Registry:
    def __init__(self, name: str) -> None:
        self.name = name
        self._entries: dict[str, Callable[..., Any]] = {}

    def register(self, name: str | None = None) -> Callable[[T], T]:
        """装饰器；`name` 缺省时使用被装饰对象的 __name__。"""

        def wrapper(obj: T) -> T:
            key = name or getattr(obj, "__name__", None)
            if key is None:
                raise ValueError(f"无法推断注册名: {obj!r}")
            if key in self._entries:
                raise KeyError(f"{self.name} 中已存在同名条目: {key}")
            self._entries[key] = obj  # type: ignore[assignment]
            return obj

        return wrapper

    def get(self, name: str) -> Callable[..., Any]:
        if name not in self._entries:
            raise KeyError(f"{self.name} 中找不到 '{name}'，可用: {sorted(self._entries)}")
        return self._entries[name]

    def build(self, cfg: dict, **kwargs: Any) -> Any:
        """按 `{"name": ..., 其余作为构造参数}` 构建对象。"""
        cfg = dict(cfg)
        name = cfg.pop("name", None)
        if name is None:
            raise KeyError(f"构建 {self.name} 需要 'name' 字段: {cfg}")
        target = self.get(name)
        params = {**cfg, **kwargs}
        self._check_params(name, target, params)
        return target(**params)

    @staticmethod
    def _check_params(name: str, target: Callable[..., Any], params: dict) -> None:
        """提前挡下不认识的字段，给出比裸 TypeError 更可操作的提示。

        最常见的触发方式：用 `--set xxx.name=其他骨架` 只改了名字，
        yaml 里原骨架的专有字段（如 tiny_conv 的 widths/depths）仍然留在配置里。
        """
        signature = inspect.signature(target)
        if any(p.kind is p.VAR_KEYWORD for p in signature.parameters.values()):
            return
        unknown = sorted(set(params) - set(signature.parameters))
        if not unknown:
            return
        accepted = sorted(p for p in signature.parameters if p != "self")
        raise TypeError(
            f"构建 '{name}' 时收到它不接受的字段 {unknown}。它接受的是 {accepted}。"
            "如果你是用 --set 改了 name，注意 yaml 里原来那个组件的专有字段仍会保留——"
            "换组件请直接编辑配置文件、整块替换。"
        )

    def __contains__(self, name: object) -> bool:
        return name in self._entries

    def __iter__(self) -> Iterator[str]:
        return iter(self._entries)

    def __len__(self) -> int:
        return len(self._entries)