"""Small filesystem helpers shared by backend services."""

import filecmp
import hashlib
import json
from pathlib import Path


def file_sha256(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as stream:
        for chunk in iter(lambda: stream.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def files_match(file_a: Path, file_b: Path) -> bool:
    try:
        return file_a.is_file() and file_b.is_file() and filecmp.cmp(file_a, file_b, shallow=False)
    except OSError:
        return False


def read_json(path: Path) -> dict:
    try:
        with path.open("r", encoding="utf-8") as stream:
            payload = json.load(stream)
        return payload if isinstance(payload, dict) else {}
    except (OSError, ValueError, TypeError):
        return {}


def write_json(path: Path, payload: dict) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    with path.open("w", encoding="utf-8") as stream:
        json.dump(payload, stream, indent=2)