config.py

from __future__ import annotations

import json
from pathlib import Path
from typing import Any


DEFAULT_CONFIG_PATH = "config.json"


class ConfigError(Exception):
    pass


def load_config(path: str | Path) -> dict[str, Any]:
    config_path = Path(path)
    if not config_path.exists():
        raise ConfigError(f"Config file not found: {config_path}")

    try:
        data = json.loads(config_path.read_text(encoding="utf-8"))
    except json.JSONDecodeError as exc:
        raise ConfigError(f"Invalid JSON in config file: {config_path}") from exc

    required_keys = [
        "watch_dir",
        "processed_dir",
        "archive_dir",
        "error_dir",
        "log_dir",
        "rules",
    ]
    missing = [key for key in required_keys if key not in data]
    if missing:
        raise ConfigError(f"Missing required config keys: {', '.join(missing)}")

    if not isinstance(data.get("rules"), list):
        raise ConfigError("Config key 'rules' must be a list")

    return data