Moved audit forward somewhat

audit_core/mock_file_backend.py

@@ -1,8 +1,8 @@
 """Development-only file backend for Audit Core.
 
-This backend intentionally writes local JSONL files under /tmp by default. It
-is useful for wiring integrations before the durable Audit Core archive exists,
-but it is not production audit custody.
+Writes hourly JSONL files under ``/tmp/audit-core`` by default. See
+``docs/audit-backend-contract.md`` for retention guarantees and the migration
+path to durable archive backends.
 """
 
 from __future__ import annotations
@@ -12,11 +12,15 @@ import os
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
-from audit_core.interface import AuditEvent
+from audit_core.interface import AuditEvent, EventValidationError, RetentionPolicy, validate_event
 
 
 class MockFileAuditBackend:
-    """Append audit events to hourly JSONL files and clean up old files."""
+    """Append audit events to hourly JSONL files and clean up old files.
+
+    Implements :class:`~audit_core.interface.AuditBackend` with
+    ``custody_class=development``. Not suitable for production audit custody.
+    """
 
     def __init__(
         self,
@@ -32,7 +36,23 @@ class MockFileAuditBackend:
         )
         self._now = now
 
+    @property
+    def retention_policy(self) -> RetentionPolicy:
+        days = self.retention_days if self.retention_days >= 0 else None
+        return RetentionPolicy(
+            custody_class="development",
+            retention_days=days,
+            immutable=False,
+            tamper_evidence=False,
+            durable=False,
+        )
+
     def emit(self, event: AuditEvent) -> str:
+        try:
+            validate_event(event)
+        except EventValidationError as exc:
+            raise ValueError(str(exc)) from exc
+
         self.base_dir.mkdir(parents=True, exist_ok=True)
         self.cleanup_old_files()
         path = self.current_path()