src/pqc_audit_log_fs/segment.py
| 1 | """AuditSegment - a sealed batch of InferenceEvents with Merkle root + ML-DSA sig.""" |
| 2 | |
| 3 | from __future__ import annotations |
| 4 | |
| 5 | import json |
| 6 | from dataclasses import asdict, dataclass, field |
| 7 | from typing import Any |
| 8 | |
| 9 | from pqc_audit_log_fs.event import InferenceEvent |
| 10 | from pqc_audit_log_fs.merkle import compute_merkle_root |
| 11 | |
| 12 | |
| 13 | @dataclass |
| 14 | class SegmentHeader: |
| 15 | """Signed header for an AuditSegment.""" |
| 16 | |
| 17 | segment_id: str # e.g. "segment-00001" |
| 18 | segment_number: int # sequential |
| 19 | created_at: str |
| 20 | sealed_at: str = "" |
| 21 | event_count: int = 0 |
| 22 | merkle_root: str = "" # hex SHA3-256 |
| 23 | previous_segment_root: str = "" # chain link |
| 24 | log_id: str = "" # stable ID of the log this segment belongs to |
| 25 | |
| 26 | # Populated by LogAppender when sealed: |
| 27 | signer_did: str = "" |
| 28 | algorithm: str = "" |
| 29 | signature: str = "" |
| 30 | public_key: str = "" |
| 31 | |
| 32 | def canonical_bytes(self) -> bytes: |
| 33 | payload = { |
| 34 | "segment_id": self.segment_id, |
| 35 | "segment_number": self.segment_number, |
| 36 | "created_at": self.created_at, |
| 37 | "sealed_at": self.sealed_at, |
| 38 | "event_count": self.event_count, |
| 39 | "merkle_root": self.merkle_root, |
| 40 | "previous_segment_root": self.previous_segment_root, |
| 41 | "log_id": self.log_id, |
| 42 | } |
| 43 | return json.dumps( |
| 44 | payload, sort_keys=True, separators=(",", ":"), ensure_ascii=False |
| 45 | ).encode("utf-8") |
| 46 | |
| 47 | def to_dict(self) -> dict[str, Any]: |
| 48 | return asdict(self) |
| 49 | |
| 50 | @classmethod |
| 51 | def from_dict(cls, data: dict[str, Any]) -> SegmentHeader: |
| 52 | return cls(**data) |
| 53 | |
| 54 | def to_json(self) -> str: |
| 55 | return json.dumps(self.to_dict(), indent=2) |
| 56 | |
| 57 | |
| 58 | @dataclass |
| 59 | class AuditSegment: |
| 60 | """A sealed batch of events + signed header.""" |
| 61 | |
| 62 | header: SegmentHeader |
| 63 | events: list[InferenceEvent] = field(default_factory=list) |
| 64 | |
| 65 | def recompute_root(self) -> str: |
| 66 | leaves = [e.leaf_hash() for e in self.events] |
| 67 | self.header.merkle_root = compute_merkle_root(leaves) if leaves else "" |
| 68 | self.header.event_count = len(self.events) |
| 69 | return self.header.merkle_root |
| 70 | |