"""AsteroidNET configuration loader with env-var overrides."""
from __future__ import annotations
import hashlib, os, copy
from pathlib import Path
from typing import Any
import yaml

_DEFAULTS = Path(__file__).parent / "defaults.yaml"
_ENV_PREFIX = "ASTEROIDNET_"


def load_config(path: str | Path | None = None) -> dict:
    with open(_DEFAULTS) as f:
        cfg = yaml.safe_load(f)
    if path:
        with open(path) as f:
            user = yaml.safe_load(f) or {}
        cfg = _deep_merge(cfg, user)
    cfg = _apply_env(cfg)
    cfg["_hash"] = hashlib.sha256(
        yaml.dump(cfg, sort_keys=True).encode()
    ).hexdigest()[:12]
    return cfg


def _deep_merge(base: dict, override: dict) -> dict:
    out = copy.deepcopy(base)
    for k, v in override.items():
        if k in out and isinstance(out[k], dict) and isinstance(v, dict):
            out[k] = _deep_merge(out[k], v)
        else:
            out[k] = v
    return out


def _apply_env(cfg: dict, _prefix: str = _ENV_PREFIX) -> dict:
    """Override config from ASTEROIDNET_SECTION__KEY=value env vars."""
    out = copy.deepcopy(cfg)
    for key, val in os.environ.items():
        if not key.startswith(_prefix):
            continue
        parts = key[len(_prefix):].lower().split("__")
        node = out
        for part in parts[:-1]:
            node = node.setdefault(part, {})
        leaf = parts[-1]
        try:
            node[leaf] = yaml.safe_load(val)
        except Exception:
            node[leaf] = val
    return out