Update DeleteDataHint with internal enum state

Author: alex-kulakov

Orm/Xtensive.Orm/Modelling/Comparison/Hints/DeleteDataHint.cs

@@ -17,20 +17,46 @@ namespace Xtensive.Modelling.Comparison.Hints
   [Serializable]
   public class DeleteDataHint : DataHint
   {
+    [Flags]
+    internal enum DeleteDataHintInfo : byte
+    {
+      None = 0,
+      PostCopy = 1,
+      TableMovement = 2,
+      All = PostCopy | TableMovement
+    }
+
+    private readonly DeleteDataHintInfo info = DeleteDataHintInfo.None;
+
     /// <summary>
-    /// Gets or sets a value indicating whether deletion must be performed after completion of copy data hint processing.
+    /// Gets a value indicating whether deletion must be performed after completion of copy data hint processing.
     /// Normally this flag is used to remove records related to types moved to other hierarchies -
     /// these records are still necessary during upgrade to be copied, but must be removed on its
     /// completion.
     /// </summary>
-    public bool PostCopy { get; private set; }
+    public bool PostCopy => info.HasFlag(DeleteDataHintInfo.PostCopy);
+
+    /// <summary>
+    /// Gets a value indicating whether cause of data deletion is due to table have changed its owner type.
+    /// </summary>
+    public bool DueToTableOwnerChange => info.HasFlag(DeleteDataHintInfo.TableMovement);
+
+    /// <summary>
+    /// Gets a value indication whether deletion is unsafe. Deletion is considered insafe
+    /// if PostCopy or DueToTableOwnerChange equals <see langword="true"/>.
+    /// </summary>
+    public bool IsUnsafe => info != DeleteDataHintInfo.None;
+
 
     /// <summary>
-    /// Gets value indicating whether cause of data deletion was moving table to another hierarchy.
-    /// This flag is used to ideitify and prevent unsafe data clean-up even if database structure
-    /// remain identical but logically table serves completely different entity.
+    /// Internal infomations about this hint.
+    /// <para>
+    /// It is used in some cases to create new hint 
+    /// based on this one. It can be done by open
+    /// constructors but enum is better.
+    /// </para>
     /// </summary>
-    public bool TableChangedOwner { get; private set; }
+    internal DeleteDataHintInfo Info => info;
 
     /// <inheritdoc/>
     public override string ToString()
@@ -41,10 +67,9 @@ public override string ToString()
         string.Join(" and ",
           Identities.Select(pair => pair.ToString()).ToArray()),
         PostCopy ? " (after data copying)" : string.Empty,
-        TableChangedOwner ? " due to table owner changed" : string.Empty);
+        DueToTableOwnerChange ? " due to table changed owner type" : string.Empty);
     }
 
-
     // Constructors
 
     /// <summary>
@@ -64,7 +89,9 @@ public DeleteDataHint(string sourceTablePath,  IList<IdentityPair> identities)
     public DeleteDataHint(string sourceTablePath,  IList<IdentityPair> identities, bool postCopy)
       : base(sourceTablePath, identities)
     {
-      PostCopy = postCopy;
+      if (postCopy) {
+        info |= DeleteDataHintInfo.PostCopy;
+      }
     }
 
     /// <summary>
@@ -73,12 +100,29 @@ public DeleteDataHint(string sourceTablePath,  IList<IdentityPair> identities, b
     /// <param name="sourceTablePath">Source table path.</param>
     /// <param name="identities">Identities for data operation.</param>
     /// <param name="postCopy"><see cref="PostCopy"/> property value.</param>
-    /// <param name="tableChangedOwner"><see cref="TableChangedOwner"/> property value.</param>
-    public DeleteDataHint(string sourceTablePath, IList<IdentityPair> identities, bool postCopy, bool tableChangedOwner)
+    /// <param name="dueToOnwerChange"><see langword="true"/> if reason of deletion is the table <paramref name="sourceTablePath"/>
+    /// has changed assigned type.</param>
+    public DeleteDataHint(string sourceTablePath, IList<IdentityPair> identities, bool postCopy, bool dueToOnwerChange)
+      : this(sourceTablePath, identities)
+    {
+      if (postCopy) {
+        info |= DeleteDataHintInfo.PostCopy;
+      }
+      if (dueToOnwerChange) {
+        info |= DeleteDataHintInfo.TableMovement;
+      }
+    }
+
+    /// <summary>
+    /// Initializes new instance of this type.
+    /// </summary>
+    /// <param name="sourceTablePath"></param>
+    /// <param name="identities"></param>
+    /// <param name="deleteDataInfo"></param>
+    internal DeleteDataHint(string sourceTablePath, IList<IdentityPair> identities, DeleteDataHintInfo deleteDataInfo)
       : base(sourceTablePath, identities)
     {
-      PostCopy = postCopy;
-      TableChangedOwner = tableChangedOwner;
+      info = deleteDataInfo;
     }
   }
 }