Validating snapshot ops for SF revisions

This change harnesses DeltaUsxMapper.ProcessDelta and DeltaUsxMapper.Schemas to determine the validity of a set of ops. Tests forthcoming

Theoretically, we now don't need to prevent users from restoring invalid versions, since that wasn't actually the problem. I'm either way on keeping that.

Author: josephmyers

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

@@ -593,6 +593,23 @@ public XDocument ToUsx(XDocument oldUsxDoc, IEnumerable<ChapterDelta> chapterDel
         }
     }
 
+    /// <summary>
+    /// Checks if the provided Delta object can be converted to a valid USX document.
+    /// </summary>
+    /// <param name="delta">The Delta object to validate.</param>
+    /// <param name="version">The USX version number to set on the root element. Defaults to 1.0.</param>
+    public static bool IsDeltaValid(Delta delta, double version = 1)
+    {
+        var xNodes = ProcessDelta(delta);
+        var usxRootElement = new XElement("usx", xNodes);
+        usxRootElement.SetAttributeValue("version", string.Format("{0:0.0}", version));
+        var usx = new XDocument(usxRootElement);
+        var isValid = true;
+        usx.Validate(Schemas, (_, _) => isValid = false);
+
+        return isValid;
+    }
+
     /// <summary>
     /// Make USX from a Delta's ops.
     /// </summary>

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

@@ -1957,11 +1957,6 @@ DateTime timestamp
         // Ensure that the timestamp is UTC
         timestamp = DateTime.SpecifyKind(timestamp, DateTimeKind.Utc);
 
-        // Load the Paratext project
-        string ptProjectId = projectDoc.Data.ParatextId;
-        using ScrText scrText = GetScrText(userSecret, ptProjectId);
-        VerseRef verseRef = new VerseRef($"{book} {chapter}:0");
-
         TextSnapshot ret;
         string id = TextData.GetTextDocId(sfProjectId, book, chapter);
         Snapshot<TextData> snapshot = await connection.FetchSnapshotAsync<TextData>(id, timestamp);
@@ -1971,9 +1966,14 @@ DateTime timestamp
             // We do not have a snapshot, so retrieve the data from Paratext
             // Note: The following code is not testable due to ParatextData limitations
 
+            // Load the Paratext project
+            string ptProjectId = projectDoc.Data.ParatextId;
+            using ScrText latestScrText = GetScrText(userSecret, ptProjectId);
+            VerseRef verseRef = new VerseRef($"{book} {chapter}:0");
+
             // Retrieve the first revision before or at the timestamp
-            VersionedText versionedText = VersioningManager.Get(scrText);
-            HgRevisionCollection revisionCollection = HgRevisionCollection.Get(scrText);
+            VersionedText versionedText = VersioningManager.Get(latestScrText);
+            HgRevisionCollection revisionCollection = HgRevisionCollection.Get(latestScrText);
             DateTimeOffset timeStampOffset = new DateTimeOffset(timestamp, TimeSpan.Zero);
             HgRevision? revision = revisionCollection
                 .FilterRevisions(r => r.CommitTimeStamp <= timeStampOffset)
@@ -1989,7 +1989,7 @@ DateTime timestamp
             // Retrieve the USFM for the chapter, and convert to USX, then to deltas
             IGetText version = versionedText.GetVersion(revision.Id);
             string usfm = version.GetText(verseRef, true, false);
-            ChapterDelta chapterDelta = GetDeltaFromUsfm(scrText, verseRef.BookNum, usfm);
+            ChapterDelta chapterDelta = GetDeltaFromUsfm(latestScrText, verseRef.BookNum, usfm);
             ret = new TextSnapshot
             {
                 Id = id,
@@ -2001,14 +2001,13 @@ DateTime timestamp
         else
         {
             // We have the snapshot, but we need to determine if it's valid
-            var usfm = scrText.GetText(verseRef.BookNum);
-            ChapterDelta chapterDelta = GetDeltaFromUsfm(scrText, verseRef.BookNum, usfm);
+            var isValid = DeltaUsxMapper.IsDeltaValid(new Delta(snapshot.Data.Ops), snapshot.Version);
             ret = new TextSnapshot
             {
                 Id = snapshot.Id,
                 Version = snapshot.Version,
                 Data = snapshot.Data,
-                IsValid = chapterDelta.IsValid,
+                IsValid = isValid,
             };
         }
 

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

@@ -3944,6 +3944,52 @@ Blessed is the man...
     [Test]
     public async Task RoundTrip_Asv() => await RoundTripTestHelper("eng-asv_usfm-partial", "eng-asv");
 
+    [Test]
+    public void IsDeltaValid_Valid_ReturnsTrue()
+    {
+        var delta = Delta.New().InsertChapter("1").InsertPara("p").InsertText("text", "verse_1_1");
+
+        bool result = DeltaUsxMapper.IsDeltaValid(delta);
+
+        Assert.IsTrue(result);
+    }
+
+    [Test]
+    public void IsDeltaValid_InvalidPara_ReturnsFalse()
+    {
+        var delta = Delta
+            .New()
+            .InsertText("Book title", "imt_1")
+            .InsertPara("imt")
+            .InsertChapter("1")
+            .InsertBlank("bad_1")
+            .InsertVerse("1")
+            .InsertText("New verse text.", "verse_1_1")
+            .InsertPara("bad", true);
+
+        bool result = DeltaUsxMapper.IsDeltaValid(delta);
+
+        Assert.IsFalse(result);
+    }
+
+    [Test]
+    public void IsDeltaValid_InvalidVerse_ReturnsFalse()
+    {
+        var delta = Delta
+            .New()
+            .InsertChapter("1")
+            .InsertBlank("p_1")
+            .InsertVerse("1", "bad", true)
+            .InsertBlank("verse_1_1")
+            .InsertVerse("2")
+            .InsertBlank("verse_1_2")
+            .InsertPara("p");
+
+        bool result = DeltaUsxMapper.IsDeltaValid(delta);
+
+        Assert.IsFalse(result);
+    }
+
     private async Task RoundTripTestHelper(string projectZipFilename, string projectShortName)
     {
         string zipFilePath = Path.Join(GetPathToTestProject(), "SampleData", $"{projectZipFilename}.zip");

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

@@ -5932,15 +5932,13 @@ public async Task GetSnapshotAsync_FetchesSnapshotFromRealtimeServer()
         ScrText scrText = env.GetScrText(associatedPtUser, ptProjectId);
 
         env.MockScrTextCollection.FindById(Arg.Any<string>(), Arg.Any<string>()).Returns(_ => scrText);
-        env.MockDeltaUsxMapper.ToChapterDeltas(Arg.Any<XDocument>())
-            .Returns([new ChapterDelta(chapter, 1, false, textData)]);
 
         // SUT
         var actual = await env.Service.GetSnapshotAsync(userSecret, project.Id, book, chapter, DateTime.UtcNow);
         Assert.AreEqual(textData.Ops.First(), actual.Data.Ops.First());
         Assert.AreEqual(textData.Id, actual.Id);
         Assert.AreEqual(0, actual.Version);
-        Assert.AreEqual(false, actual.IsValid);
+        Assert.AreEqual(true, actual.IsValid); //snapshot in test repo is valid USFM
     }
 
     [Test]