Embed question verification references

api/QuestionsApi/Services/QuestionStore.cs

@@ -151,6 +151,32 @@ public class QuestionStore
         return systems.Where(s => !string.IsNullOrWhiteSpace(s)).OrderBy(s => s).ToList();
     }
 
+    public async Task<List<string>> GetMissingExternalIdsAsync(IEnumerable<string> externalIds)
+    {
+        var requested = externalIds.Distinct(StringComparer.Ordinal).ToList();
+        var existing = await _col.Find(Builders<Question>.Filter.In(q => q.ExternalId, requested))
+            .Project(q => q.ExternalId)
+            .ToListAsync();
+        return requested.Except(existing, StringComparer.Ordinal).OrderBy(id => id).ToList();
+    }
+
+    public async Task<int> UpdateReferencesByExternalIdAsync(IEnumerable<QuestionReferencesUpdate> updates)
+    {
+        var now = DateTime.UtcNow;
+        var writes = updates.Select(update =>
+            new UpdateOneModel<Question>(
+                Builders<Question>.Filter.Eq(question => question.ExternalId, update.ExternalId.Trim()),
+                Builders<Question>.Update
+                    .Set(question => question.References, NormalizeReferences(update.References))
+                    .Set(question => question.UpdatedUtc, now)))
+            .ToList();
+        if (writes.Count == 0)
+            return 0;
+
+        var result = await _col.BulkWriteAsync(writes, new BulkWriteOptions { IsOrdered = true });
+        return (int)result.MatchedCount;
+    }
+
     private static Question FromRequest(UpsertQuestionRequest req) => new()
     {
         ExternalId = req.ExternalId.Trim(),
@@ -169,6 +195,18 @@ public class QuestionStore
         Labs = req.Labs,
         Media = req.Media,
         Tags = req.Tags.Where(t => !string.IsNullOrWhiteSpace(t)).Select(t => t.Trim()).Distinct(StringComparer.OrdinalIgnoreCase).ToList(),
+        References = NormalizeReferences(req.References),
         IsPublished = req.IsPublished
     };
+
+    private static List<QuestionReference> NormalizeReferences(IEnumerable<QuestionReference>? references) =>
+        (references ?? []).Select(reference => new QuestionReference
+        {
+            Title = reference.Title.Trim(),
+            Publisher = reference.Publisher.Trim(),
+            Url = reference.Url.Trim(),
+            Supports = reference.Supports.Trim(),
+            AccessedOn = reference.AccessedOn.Trim(),
+            Reviewer = reference.Reviewer.Trim()
+        }).ToList();
 }