SF-3604 Fix download of historic drafts

Author: pmachapman

src/SIL.XForge.Scripture/Services/MachineApiService.cs

@@ -1580,25 +1580,63 @@ CancellationToken cancellationToken
             cancellationToken
         );
 
-        // First, see if the document exists in the realtime service, if the chapter is not 0
+        // First, see if the document exists in the realtime service, if we are not retrieving a custom draft configuration
         IDocument<TextDocument>? textDocument = null;
-        if (chapterNum != 0 && draftUsfmConfig is null)
+        if (draftUsfmConfig is null)
         {
-            textDocument = await connection.FetchAsync<TextDocument>(id);
-            if (textDocument.IsLoaded)
+            // Retrieve the chapters for this book from the realtime server, if the chapter is zero
+            if (chapterNum == 0)
             {
-                // Retrieve the snapshot if it exists
-                Snapshot<TextDocument> snapshot = await connection.FetchSnapshotAsync<TextDocument>(
-                    id,
-                    latestTimestampForRevision
-                );
-                if (snapshot.Data is not null)
+                List<object> content = [];
+                foreach (Chapter chapter in project.Texts.SingleOrDefault(t => t.BookNum == bookNum)?.Chapters ?? [])
+                {
+                    id = TextDocument.GetDocId(sfProjectId, bookNum, chapter.Number, TextDocument.Draft);
+                    textDocument = await connection.FetchAsync<TextDocument>(id);
+                    if (textDocument.IsLoaded)
+                    {
+                        // Retrieve the snapshot if it exists
+                        Snapshot<TextDocument> snapshot = await connection.FetchSnapshotAsync<TextDocument>(
+                            id,
+                            latestTimestampForRevision
+                        );
+                        if (snapshot.Data?.Content is not null)
+                        {
+                            // Append the chapter to the book content
+                            content.AddRange(snapshot.Data.Content);
+                        }
+                    }
+                }
+
+                // Return the USJ of the entire book, if present
+                if (content.Count > 0)
                 {
-                    return snapshot.Data;
+                    return new Usj
+                    {
+                        Type = Usj.UsjType,
+                        Version = Usj.UsjVersion,
+                        Content = content,
+                    };
                 }
+            }
+            else
+            {
+                // Otherwise, retrieve the specific chapter from the realtime server
+                textDocument = await connection.FetchAsync<TextDocument>(id);
+                if (textDocument.IsLoaded)
+                {
+                    // Retrieve the snapshot if it exists
+                    Snapshot<TextDocument> snapshot = await connection.FetchSnapshotAsync<TextDocument>(
+                        id,
+                        latestTimestampForRevision
+                    );
+                    if (snapshot.Data is not null)
+                    {
+                        return snapshot.Data;
+                    }
 
-                // There is no draft at the timestamp
-                throw new DataNotFoundException("A draft cannot be retrieved at that timestamp");
+                    // There is no draft at the timestamp
+                    throw new DataNotFoundException("A draft cannot be retrieved at that timestamp");
+                }
             }
         }
 

test/SIL.XForge.Scripture.Tests/Services/MachineApiServiceTests.cs

@@ -2634,6 +2634,70 @@ await env
             );
     }
 
+    [Test]
+    public async Task GetPreTranslationUsjAsync_ChapterZeroLoadsMultipleChaptersFromMongo()
+    {
+        // Set up test environment
+        var env = new TestEnvironment();
+        Usj testUsjChapterTwo = new Usj
+        {
+            Type = Usj.UsjType,
+            Version = Usj.UsjVersion,
+            Content =
+            [
+                new UsjMarker
+                {
+                    Type = "chapter",
+                    Marker = "c",
+                    Number = "2",
+                },
+                new UsjMarker
+                {
+                    Type = "verse",
+                    Marker = "v",
+                    Number = "1",
+                },
+                "Verse 1",
+            ],
+        };
+        string id1 = TextDocument.GetDocId(Project01, 40, 1, TextDocument.Draft);
+        env.TextDocuments.Add(new TextDocument(id1, TestUsj));
+        string id2 = TextDocument.GetDocId(Project01, 40, 2, TextDocument.Draft);
+        env.TextDocuments.Add(new TextDocument(id2, testUsjChapterTwo));
+
+        // The chapters must be configured in the project document
+        await env.Projects.UpdateAsync(
+            Project01,
+            u =>
+                u.Add(
+                    p => p.Texts,
+                    new TextInfo { BookNum = 40, Chapters = [new Chapter { Number = 1 }, new Chapter { Number = 2 }] }
+                )
+        );
+
+        // SUT
+        IUsj actual = await env.Service.GetPreTranslationUsjAsync(
+            User01,
+            Project01,
+            40,
+            0,
+            false,
+            DateTime.UtcNow,
+            null,
+            CancellationToken.None
+        );
+
+        // The returned Usj will be chapter 1 and 2 combined in order
+        List<object> expectedContent = [.. TestUsj.Content, .. testUsjChapterTwo.Content];
+        Usj expected = new Usj
+        {
+            Type = Usj.UsjType,
+            Version = Usj.UsjVersion,
+            Content = expectedContent,
+        };
+        Assert.That(actual, Is.EqualTo(expected).UsingPropertiesComparer());
+    }
+
     [Test]
     public void GetPreTranslationUsjAsync_CorpusDoesNotSupportUsfm()
     {