"""Delta signing utilities for BeVault."""
from __future__ import annotations

import hashlib
import hmac
import json

from .core import HedgeDelta


def sign_delta(delta: HedgeDelta, key: bytes) -> str:
    """Sign a HedgeDelta deterministically using HMAC-SHA256."""

    payload = json.dumps(delta.to_signable_dict(), sort_keys=True, separators=(",", ":"))
    return hmac.new(key, payload.encode("utf-8"), hashlib.sha256).hexdigest()


def verify_delta(delta: HedgeDelta, key: bytes, signature: str) -> bool:
    """Verify a delta signature in a deterministic way."""

    return hmac.compare_digest(sign_delta(delta, key), signature)


__all__ = ["sign_delta", "verify_delta"]