"""列头 facet 上下文：剥离当前列自身过滤键（Excel 语义）。"""
from __future__ import annotations

import re
from typing import Dict, Iterable, MutableMapping, Optional, Set


def _camel_to_snake(name: str) -> str:
    s1 = re.sub("(.)([A-Z][a-z]+)", r"\1_\2", name)
    return re.sub("([a-z0-9])([A-Z])", r"\1_\2", s1).lower()


def keys_for_facet_field(
    field: str, *, extra_keys: Optional[Iterable[str]] = None
) -> Set[str]:
    f = (field or "").strip()
    snake = _camel_to_snake(f) if f else ""
    keys = {f, f"{f}In", snake, f"{snake}_in"}
    if extra_keys:
        keys.update(k for k in extra_keys if k)
    return {k for k in keys if k}


def strip_simple_facet_self_params(
    params: MutableMapping[str, object],
    field: str,
    *,
    extra_keys: Optional[Iterable[str]] = None,
) -> Dict[str, object]:
    """去掉当前 facet 列对应过滤键与元数据，返回新 dict。"""
    out = {k: v for k, v in params.items() if v not in (None, "")}
    for key in keys_for_facet_field(field, extra_keys=extra_keys):
        out.pop(key, None)
    for meta in ("field", "keyword", "limit"):
        out.pop(meta, None)
    return out