First attempt at making IChangeContext interface

src/SIL.Harmony.Core/IChangeContext.cs

@@ -0,0 +1,16 @@
+namespace SIL.Harmony.Core;
+
+public interface IChangeContext
+{
+    public CommitBase Commit { get; }
+    ValueTask<ObjectSnapshot?> GetSnapshot(Guid entityId);
+    public async ValueTask<T?> GetCurrent<T>(Guid entityId) where T : class
+    {
+        var snapshot = await GetSnapshot(entityId);
+        if (snapshot is null) return null;
+        return (T) snapshot.Entity.DbObject;
+    }
+
+    public async ValueTask<bool> IsObjectDeleted(Guid entityId) => (await GetSnapshot(entityId))?.EntityIsDeleted ?? true;
+    internal IObjectBase Adapt(object obj);
+}

src/SIL.Harmony.Core/IObjectBase.cs

@@ -0,0 +1,35 @@
+using System.Text.Json.Serialization;
+
+namespace SIL.Harmony.Core;
+
+[JsonPolymorphic]
+public interface IObjectBase
+{
+    Guid Id { get; }
+    DateTimeOffset? DeletedAt { get; set; }
+
+    /// <summary>
+    /// provides the references this object has to other objects, when those objects are deleted
+    /// <see cref="RemoveReference"/> will be called to remove the reference
+    /// </summary>
+    /// <returns></returns>
+    public Guid[] GetReferences();
+    /// <summary>
+    /// remove a reference to another object, in some cases this may cause this object to be deleted
+    /// </summary>
+    /// <param name="id">id of the deleted object</param>
+    /// <param name="commit">
+    /// commit where the reference was removed
+    /// should be used to set the deleted date for this object
+    /// </param>
+    public void RemoveReference(Guid id, CommitBase commit);
+
+    public IObjectBase Copy();
+    /// <summary>
+    /// the name of the object type, this is used to discriminate between different types of objects in the snapshots table
+    /// </summary>
+    /// <returns>a stable type name of this object, should not change over time</returns>
+    public string GetObjectTypeName();
+    [JsonIgnore]
+    public object DbObject { get; }
+}

src/SIL.Harmony.Core/ObjectSnapshot.cs

@@ -0,0 +1,53 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Text.Json.Serialization;
+
+namespace SIL.Harmony.Core;
+
+public class ObjectSnapshot
+{
+    public static ObjectSnapshot ForTesting(CommitBase commit)
+    {
+        return new ObjectSnapshot
+        {
+            Commit = commit,
+            Entity = null!,
+            Id = Guid.Empty,
+            References = [],
+            CommitId = commit.Id,
+            EntityId = Guid.Empty,
+            IsRoot = false,
+            TypeName = "Test",
+            EntityIsDeleted = false
+        };
+    }
+    //determines column name used in projected object tables, changing this will require a migration
+    public const string ShadowRefName = "SnapshotId";
+    [JsonConstructor]
+    protected ObjectSnapshot()
+    {
+    }
+
+    [SetsRequiredMembers]
+    public ObjectSnapshot(IObjectBase entity, CommitBase commit, bool isRoot) : this()
+    {
+        Id = Guid.NewGuid();
+        Entity = entity;
+        References = entity.GetReferences();
+        EntityId = entity.Id;
+        EntityIsDeleted = entity.DeletedAt.HasValue;
+        TypeName = entity.GetObjectTypeName();
+        CommitId = commit.Id;
+        Commit = commit;
+        IsRoot = isRoot;
+    }
+
+    public required Guid Id { get; init; }
+    public required string TypeName { get; init; }
+    public required IObjectBase Entity { get; init; }
+    public required Guid[] References { get; init; }
+    public required Guid EntityId { get; init; }
+    public required bool EntityIsDeleted { get; init; }
+    public required Guid CommitId { get; init; }
+    public required CommitBase Commit { get; init; }
+    public required bool IsRoot { get; init; }
+}

src/SIL.Harmony/Changes/ChangeContext.cs

@@ -1,9 +1,10 @@
+using SIL.Harmony.Core;
 using SIL.Harmony.Db;
 using SIL.Harmony.Entities;
 
 namespace SIL.Harmony.Changes;
 
-public class ChangeContext
+public class ChangeContext : IChangeContext
 {
     private readonly SnapshotWorker _worker;
     private readonly CrdtConfig _crdtConfig;
@@ -15,7 +16,7 @@
         Commit = commit;
     }
 
-    public Commit Commit { get; }
+    public Commit Commit { get; } // PROBLEM: Interface is CommitBase. How do I do this?
     public async ValueTask<ObjectSnapshot?> GetSnapshot(Guid entityId) => await _worker.GetSnapshot(entityId);
     public async ValueTask<T?> GetCurrent<T>(Guid entityId) where T : class
     {

src/SIL.Harmony/Db/ObjectSnapshot.cs

@@ -1,5 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
-using System.Text.Json.Serialization;
 using SIL.Harmony.Core;
 using SIL.Harmony.Entities;
 using SIL.Harmony.Helpers;
@@ -24,57 +22,8 @@ public SimpleSnapshot(ObjectSnapshot snapshot) : this(snapshot.Id,
         snapshot.CommitId,
         snapshot.IsRoot,
         snapshot.Commit.HybridDateTime,
-        snapshot.Commit.Hash,
+        snapshot.Commit.Hash, // PROBLEM: ObjectSnapshot.Commit is now a CommitBase which doesn't have a Hash property
         snapshot.EntityIsDeleted)
     {
     }
 }
-
-public class ObjectSnapshot
-{
-    public static ObjectSnapshot ForTesting(Commit commit)
-    {
-        return new ObjectSnapshot
-        {
-            Commit = commit,
-            Entity = null!,
-            Id = Guid.Empty,
-            References = [],
-            CommitId = commit.Id,
-            EntityId = Guid.Empty,
-            IsRoot = false,
-            TypeName = "Test",
-            EntityIsDeleted = false
-        };
-    }
-    //determines column name used in projected object tables, changing this will require a migration
-    public const string ShadowRefName = "SnapshotId";
-    [JsonConstructor]
-    protected ObjectSnapshot()
-    {
-    }
-
-    [SetsRequiredMembers]
-    public ObjectSnapshot(IObjectBase entity, Commit commit, bool isRoot) : this()
-    {
-        Id = Guid.NewGuid();
-        Entity = entity;
-        References = entity.GetReferences();
-        EntityId = entity.Id;
-        EntityIsDeleted = entity.DeletedAt.HasValue;
-        TypeName = entity.GetObjectTypeName();
-        CommitId = commit.Id;
-        Commit = commit;
-        IsRoot = isRoot;
-    }
-
-    public required Guid Id { get; init; }
-    public required string TypeName { get; init; }
-    public required IObjectBase Entity { get; init; }
-    public required Guid[] References { get; init; }
-    public required Guid EntityId { get; init; }
-    public required bool EntityIsDeleted { get; init; }
-    public required Guid CommitId { get; init; }
-    public required Commit Commit { get; init; }
-    public required bool IsRoot { get; init; }
-}

src/SIL.Harmony/Entities/IObjectBase.cs

@@ -1,39 +1,8 @@
 using System.Text.Json.Serialization;
+using SIL.Harmony.Core;
 
 namespace SIL.Harmony.Entities;
 
-[JsonPolymorphic]
-public interface IObjectBase
-{
-    Guid Id { get; }
-    DateTimeOffset? DeletedAt { get; set; }
-
-    /// <summary>
-    /// provides the references this object has to other objects, when those objects are deleted
-    /// <see cref="RemoveReference"/> will be called to remove the reference
-    /// </summary>
-    /// <returns></returns>
-    public Guid[] GetReferences();
-    /// <summary>
-    /// remove a reference to another object, in some cases this may cause this object to be deleted
-    /// </summary>
-    /// <param name="id">id of the deleted object</param>
-    /// <param name="commit">
-    /// commit where the reference was removed
-    /// should be used to set the deleted date for this object
-    /// </param>
-    public void RemoveReference(Guid id, Commit commit);
-
-    public IObjectBase Copy();
-    /// <summary>
-    /// the name of the object type, this is used to discriminate between different types of objects in the snapshots table
-    /// </summary>
-    /// <returns>a stable type name of this object, should not change over time</returns>
-    public string GetObjectTypeName();
-    [JsonIgnore]
-    public object DbObject { get; }
-}
-
 public interface IObjectBase<TThis> : IObjectBase, IPolyType where TThis : IPolyType
 {
     string IObjectBase.GetObjectTypeName() => TThis.TypeName;