"""YAML config loader and validator."""

from __future__ import annotations

from pathlib import Path
from typing import Any

import yaml


REQUIRED = {"distro", "arch"}


def load(path: Path) -> dict[str, Any]:
    """Load and validate a YAML config file."""
    with open(path) as f:
        cfg = yaml.safe_load(f)

    if not isinstance(cfg, dict):
        raise ValueError(f"Config must be a YAML mapping, got {type(cfg).__name__}")

    missing = REQUIRED - cfg.keys()
    if missing:
        raise ValueError(f"Missing required fields: {', '.join(sorted(missing))}")

    # defaults
    cfg.setdefault("hostname", "euri")
    cfg.setdefault("users", [])
    cfg.setdefault("services", [])
    cfg.setdefault("packages", [])
    cfg.setdefault("init", "dinit")
    cfg.setdefault("bootloader", "grub")
    cfg.setdefault("iso", {})

    return cfg