import json
import logging
import os
from pathlib import Path
from typing import Any, Optional

logger = logging.getLogger(__name__)

_DEFAULTS: dict[str, Any] = {
    "log_level": "INFO",
    "debug": False,
    "max_retries": 3,
    "request_timeout": 30,
    "page_size": 20,
    "db_path": "data.db",
    "secret_key": "",
}


class Config:
    def __init__(self, path: Optional[str] = None) -> None:
        self._data: dict[str, Any] = dict(_DEFAULTS)
        if path and Path(path).exists():
            self._load(path)
        self._from_env()

    def _load(self, path: str) -> None:
        try:
            with open(path) as f:
                self._data.update(json.load(f))
        except (json.JSONDecodeError, OSError) as exc:
            logger.warning("Config load failed (%s): %s", path, exc)

    def _from_env(self) -> None:
        pairs = [
            ("APP_DEBUG",     "debug",     lambda v: v.lower() == "true"),
            ("APP_LOG_LEVEL", "log_level", str),
            ("APP_DB_PATH",   "db_path",   str),
            ("APP_SECRET_KEY","secret_key",str),
        ]
        for env, key, cast in pairs:
            raw = os.environ.get(env)
            if raw is not None:
                try:
                    self._data[key] = cast(raw)
                except (ValueError, TypeError):
                    pass

    def get(self, key: str, default: Any = None) -> Any:
        return self._data.get(key, default)

    def __getattr__(self, key: str) -> Any:
        if key.startswith("_"):
            raise AttributeError(key)
        try:
            return self._data[key]
        except KeyError:
            raise AttributeError(key)


_cfg: Optional[Config] = None

def get_config() -> Config:
    global _cfg
    if _cfg is None:
        _cfg = Config(os.environ.get("APP_CONFIG"))
    return _cfg