drp/canon.py

import json
import hashlib
from datetime import datetime, timezone
from typing import Any, Dict

DRP_EVENT_SPEC = "drp-event-v0"
DRP_BUNDLE_SPEC = "drp-bundle-v0"


def canon(obj: Any) -> bytes:
    """Canonical JSON encoding (stable for hashing/verifying across machines)."""
    return json.dumps(
        obj,
        ensure_ascii=False,
        sort_keys=True,
        separators=(",", ":"),
    ).encode("utf-8")


def sha256_hex(b: bytes) -> str:
    return hashlib.sha256(b).hexdigest()


def now_utc_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


def hash_event(event: Dict[str, Any]) -> str:
    """Hash event excluding its own 'hash' field (if present)."""
    e = dict(event)
    e.pop("hash", None)
    return sha256_hex(canon(e))