from __future__ import annotations
from pathlib import Path
from typing import Any, Dict, List
import copy
import yaml


def _deep_update(base: Dict[str, Any], update: Dict[str, Any]) -> Dict[str, Any]:
    out = copy.deepcopy(base)
    for k, v in update.items():
        if isinstance(v, dict) and isinstance(out.get(k), dict):
            out[k] = _deep_update(out[k], v)
        else:
            out[k] = copy.deepcopy(v)
    return out


def load_yaml(path: str | Path) -> Dict[str, Any]:
    path = Path(path)
    with open(path, "r") as f:
        cfg = yaml.safe_load(f) or {}
    base_files = cfg.pop("_base_", [])
    if isinstance(base_files, str):
        base_files = [base_files]
    merged: Dict[str, Any] = {}
    for base in base_files:
        base_path = (path.parent / base).resolve()
        merged = _deep_update(merged, load_yaml(base_path))
    merged = _deep_update(merged, cfg)
    return merged


def save_yaml(cfg: Dict[str, Any], path: str | Path) -> None:
    path = Path(path)
    path.parent.mkdir(parents=True, exist_ok=True)
    with open(path, "w") as f:
        yaml.safe_dump(cfg, f, sort_keys=False)


def get(cfg: Dict[str, Any], key: str, default=None):
    cur = cfg
    for part in key.split("."):
        if not isinstance(cur, dict) or part not in cur:
            return default
        cur = cur[part]
    return cur


def set_by_path(cfg: Dict[str, Any], key: str, value: Any) -> None:
    cur = cfg
    parts = key.split(".")
    for p in parts[:-1]:
        cur = cur.setdefault(p, {})
    cur[parts[-1]] = value