Allow getting objects of type via IChangeContext (#41)

* allow changes to get all entities of a given type to use for constraint checks

Author: hahn-kev

src/SIL.Harmony.Core/IChangeContext.cs

@@ -14,4 +14,5 @@ public interface IChangeContext
     public async ValueTask<bool> IsObjectDeleted(Guid entityId) => (await GetSnapshot(entityId))?.EntityIsDeleted ?? true;
     internal IObjectBase Adapt(object obj);
     IAsyncEnumerable<object> GetObjectsReferencing(Guid entityId, bool includeDeleted = false);
+    IAsyncEnumerable<T> GetObjectsOfType<T>(string jsonTypeName, bool includeDeleted = false) where T : class;
 }

src/SIL.Harmony.Sample/Changes/SetTagChange.cs

@@ -8,19 +8,26 @@ public class SetTagChange(Guid entityId, string text) : Change<Tag>(entityId), I
 {
     public string Text { get; } = text;
 
-    public override ValueTask<Tag> NewEntity(Commit commit, IChangeContext context)
+    public override async ValueTask<Tag> NewEntity(Commit commit, IChangeContext context)
     {
-        return new(new Tag()
+        var tagExists = await context.GetObjectsOfType<Tag>(nameof(Tag)).AnyAsync(t => t.Text == Text);
+        return new Tag()
         {
             Id = EntityId,
-            Text = Text
-        });
+            Text = Text,
+            DeletedAt = tagExists ?  commit.DateTime : null
+        };
     }
 
 
-    public override ValueTask ApplyChange(Tag entity, IChangeContext context)
+    public override async ValueTask ApplyChange(Tag entity, IChangeContext context)
     {
+        if (entity.Text == Text) return;
+        var tagExists = await context.GetObjectsOfType<Tag>(nameof(Tag)).AnyAsync(t => t.Id != EntityId && t.Text == Text);
+        if (tagExists)
+        {
+            entity.DeletedAt = context.Commit.DateTime;
+        }
         entity.Text = Text;
-        return ValueTask.CompletedTask;
     }
 }

src/SIL.Harmony.Tests/DataModelReferenceTests.cs

@@ -150,4 +150,26 @@ await AddCommitsViaSync([
         def.Should().NotBeNull();
         def.DeletedAt.Should().NotBeNull();
     }
+
+    [Fact]
+    public async Task CanCreate2TagsWithTheSameNameOutOfOrder()
+    {
+        var tagText = "tag1";
+        var commitA = await WriteNextChange(SetTag(Guid.NewGuid(), tagText));
+        //represents someone syncing in a tag with the same name
+        await WriteChangeBefore(commitA, SetTag(Guid.NewGuid(), tagText));
+        DataModel.QueryLatest<Tag>().Where(t => t.Text == tagText).Should().ContainSingle();
+    }
+
+    [Fact]
+    public async Task CanUpdateTagWithTheSameNameOutOfOrder()
+    {
+        var tagText = "tag1";
+        var renameTagId = Guid.NewGuid();
+        await WriteNextChange(SetTag(renameTagId, "tag2"));
+        var commitA = await WriteNextChange(SetTag(Guid.NewGuid(), tagText));
+        //represents someone syncing in a tag with the same name
+        await WriteNextChange(SetTag(renameTagId, tagText));
+        DataModel.QueryLatest<Tag>().Where(t => t.Text == tagText).Should().ContainSingle();
+    }
 }

src/SIL.Harmony/Changes/ChangeContext.cs

@@ -25,5 +25,13 @@ public IAsyncEnumerable<object> GetObjectsReferencing(Guid entityId, bool includ
     {
         return _worker.GetSnapshotsReferencing(entityId, includeDeleted).Select(s => s.Entity.DbObject);
     }
+
+    public IAsyncEnumerable<T> GetObjectsOfType<T>(string jsonTypeName, bool includeDeleted = false) where T : class
+    {
+        return _worker.GetSnapshotsWhere(s => (includeDeleted || !s.EntityIsDeleted) && s.TypeName == jsonTypeName)
+            .Select(s => s.Entity.DbObject)
+            .OfType<T>();
+    }
+
     IObjectBase IChangeContext.Adapt(object obj) => _crdtConfig.ObjectTypeListBuilder.Adapt(obj);
 }