Add helpers for versioning by version_index

src/documents/versioning.py

@@ -5,12 +5,34 @@ from enum import StrEnum
 from typing import TYPE_CHECKING
 from typing import Any
 
+from django.db.models import F
+from django.db.models import QuerySet
+
 from documents.models import Document
 
 if TYPE_CHECKING:
     from rest_framework.request import Request
 
 
+def versions_newest_first(documents: QuerySet[Document]) -> QuerySet[Document]:
+    """
+    Sorts versions so the newest one comes first using version_index and not on id,
+    because an existing document can be merged in as a version
+    """
+    return documents.order_by(F("version_index").desc(nulls_last=True), "-id")
+
+
+def sort_versions_newest_first(documents: list[Document]) -> list[Document]:
+    """
+    Same sorting as versions_newest_first()
+    """
+    return sorted(
+        documents,
+        key=lambda doc: (doc.version_index or 0, doc.id),
+        reverse=True,
+    )
+
+
 class VersionResolutionError(StrEnum):
     INVALID = "invalid"
     NOT_FOUND = "not_found"
@@ -51,7 +73,7 @@ def get_latest_version_for_root(
     include_deleted: bool = False,
 ) -> Document:
     manager = _document_manager(include_deleted=include_deleted)
-    latest = manager.filter(root_document=root_doc).order_by("-id").first()
+    latest = versions_newest_first(manager.filter(root_document=root_doc)).first()
     return latest or root_doc