#region Apache License 2.0
/*
Nuclex .NET Framework
Copyright (C) 2002-2024 Markus Ewald / Nuclex Development Labs

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#endregion // Apache License 2.0

using System;

namespace Nuclex.Support.Collections {

  /// <summary>Base class for objects that can be parented to an owner</summary>
  /// <typeparam name="TParent">Type of the parent object</typeparam>
  public class Parentable<TParent> {

    /// <summary>The parent object that owns this instance</summary>
    protected TParent Parent {
      get { return this.parent; }
    }

    /// <summary>Invoked whenever the instance's owner changes</summary>
    /// <remarks>
    ///   When items are parented for the first time, the oldParent argument will
    ///   be null. Also, if the element is removed from the collection, the
    ///   current parent will be null.
    /// </remarks>
    /// <param name="oldParent">Previous owner of the instance</param>
    protected virtual void OnParentChanged(TParent oldParent) { }

    /// <summary>Assigns a new parent to this instance</summary>
    internal void SetParent(TParent parent) {
      TParent oldParent = this.parent;
      this.parent = parent;

      OnParentChanged(oldParent);
    }

    /// <summary>Current parent of this object</summary>
    private TParent parent;

  }

} // namespace Nuclex.Support.Collections