Create drp/canon.py

drp/canon.py

@@ -0,0 +1,36 @@
+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 for stable hashing 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))