"""Helpers for stable packet identity across capture and telemetry events."""

from __future__ import annotations

import hashlib
from typing import Any, Dict


IDENTITY_FIELDS = (
    "src_mac",
    "dst_mac",
    "eth_type_raw",
    "vlan_id",
    "src_ip",
    "dst_ip",
    "protocol_raw",
    "src_port",
    "dst_port",
    "length",
    "ip_id",
    "icmp_type",
    "icmp_code",
    "arp_op",
    "tcp_seq",
    "tcp_ack",
    "tcp_flags",
)


def build_packet_uid(fields: Dict[str, Any]) -> str:
    """Build a deterministic packet identifier from selected L2-L4 fields."""
    normalized = []
    for field in IDENTITY_FIELDS:
        value = fields.get(field)
        if isinstance(value, bytes):
            value = value.hex()
        normalized.append("" if value is None else str(value))
    digest = hashlib.sha1("|".join(normalized).encode("utf-8")).hexdigest()
    return digest


def minimal_identity_dict(fields: Dict[str, Any]) -> Dict[str, Any]:
    """Return only the identity-relevant subset of packet fields."""
    return {field: fields.get(field) for field in IDENTITY_FIELDS}