✨(backend) serve documents/{id}/formatted-content/ from yhub

The formatted-content endpoint was using the `document.content` to fetch
the ydoc from s3, we want to move from this usage to using yhub to
retrieve the content, so yhub is becoming our source of thruth.

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to
 - ✨(backend) call YHubService to seed initial document content
 - ✨(collaboration) add a get-ydoc endpoint on yhub
 - ✨(backend) duplicate a document through the collaboration server
+- ✨(backend) serve `documents/{id}/formatted-content/` from yhub
 
 ### Changed
 

src/backend/core/api/viewsets.py

@@ -2,7 +2,6 @@
 
 # pylint: disable=too-many-lines
 
-import base64
 import ipaddress
 import json
 import logging
@@ -2437,15 +2436,24 @@ class DocumentViewSet(
                 "Invalid format. Must be one of: json, markdown, html"
             )
 
-        # Get the base64 content from the document
+        # Get the content from the collaboration server, it is the source of
+        # truth for it
+        try:
+            update = YHubService(user=request.user).get_ydoc(document)
+        except YHubError as e:
+            logger.error("Error getting content for document %s: %s", pk, e)
+            return drf_response.Response(
+                {"error": "Failed to get document content"},
+                status=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            )
+
         content = None
-        base64_content = document.content
-        if base64_content is not None:
+        if update is not None:
             # Convert using the y-provider service
             try:
                 yprovider = Converter()
                 result = yprovider.convert(
-                    base64.b64decode(base64_content),
+                    update,
                     mime_types.YJS,
                     {
                         "markdown": mime_types.MARKDOWN,

src/backend/core/tests/documents/test_api_documents_formatted_content.py

@@ -11,10 +11,30 @@ from rest_framework import status
 from rest_framework.test import APIClient
 
 from core import factories
+from core.services.yhub_services import (
+    ServiceUnavailableError as YHubServiceUnavailableError,
+)
 
 pytestmark = pytest.mark.django_db
 
 
+@pytest.fixture(autouse=True, name="mock_yhub")
+def mock_yhub_fixture():
+    """
+    The content of a document is held by the collaboration server.
+
+    It stands for a server holding the very content the factories gave the
+    documents, which is what an editor connected to it would have saved.
+    """
+
+    def get_ydoc(document):
+        return base64.b64decode(document.content) if document.content else None
+
+    with patch("core.api.viewsets.YHubService") as mock_service:
+        mock_service.return_value.get_ydoc.side_effect = get_ydoc
+        yield mock_service
+
+
 @pytest.mark.parametrize(
     "reach, role",
     [
@@ -182,3 +202,46 @@ def test_api_documents_formatted_content_empty_document(mock_request):
     assert data["title"] == document.title
     assert data["content"] is None
     mock_request.assert_not_called()
+
+
+@patch("core.services.converter_services.YdocConverter.convert")
+def test_api_documents_formatted_content_from_collaboration_server(
+    mock_content, mock_yhub
+):
+    """The content converted is the one held by the collaboration server."""
+    document = factories.DocumentFactory(link_reach="public")
+    mock_content.return_value = {"some": "data"}
+    # what the collaboration server holds, edited since Django last saw it
+    mock_yhub.return_value.get_ydoc.side_effect = None
+    mock_yhub.return_value.get_ydoc.return_value = b"\x01\x02edited update"
+
+    response = APIClient().get(
+        f"/api/v1.0/documents/{document.id!s}/formatted-content/"
+    )
+
+    assert response.status_code == status.HTTP_200_OK
+    mock_yhub.return_value.get_ydoc.assert_called_once_with(document)
+    mock_content.assert_called_once_with(
+        b"\x01\x02edited update",
+        "application/vnd.yjs.doc",
+        "application/json",
+    )
+
+
+@patch("core.services.converter_services.YdocConverter.convert")
+def test_api_documents_formatted_content_collaboration_server_error(
+    mock_content, mock_yhub
+):
+    """A content the collaboration server cannot serve should answer a 500."""
+    document = factories.DocumentFactory(link_reach="public")
+    mock_yhub.return_value.get_ydoc.side_effect = YHubServiceUnavailableError(
+        "Failed to connect to the yhub service"
+    )
+
+    response = APIClient().get(
+        f"/api/v1.0/documents/{document.id!s}/formatted-content/"
+    )
+
+    assert response.status_code == status.HTTP_500_INTERNAL_SERVER_ERROR
+    assert response.json() == {"error": "Failed to get document content"}
+    mock_content.assert_not_called()