"""Classify a directory as a plan unit, a reusable module, or unknown."""
from __future__ import annotations

from enum import Enum
from pathlib import Path

import hcl2


class DirKind(str, Enum):
    PLAN_UNIT = "plan_unit"
    MODULE = "module"
    UNKNOWN = "unknown"


def _has_backend_block(tf_path: Path) -> bool:
    try:
        with tf_path.open() as fh:
            parsed = hcl2.load(fh)
    except Exception:
        return False
    for block in parsed.get("terraform", []):
        if isinstance(block, dict) and "backend" in block:
            return True
    return False


def classify_dir(repo_root: Path | str, rel_dir: str) -> DirKind:
    root = Path(repo_root)
    full = root / rel_dir
    if not full.is_dir():
        raise FileNotFoundError(full)

    if (full / "terragrunt.hcl").is_file():
        return DirKind.PLAN_UNIT

    tf_files = sorted(full.glob("*.tf")) + sorted(full.glob("*.tf.json"))
    if not tf_files:
        return DirKind.UNKNOWN

    for tf in tf_files:
        if tf.suffix == ".tf" and _has_backend_block(tf):
            return DirKind.PLAN_UNIT
    return DirKind.MODULE