// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using Microsoft.ML.Runtime;
 
namespace Microsoft.ML.Data;
 
/// <summary>
/// Base class for a cursor has an input cursor, but still needs to do work on <see cref="DataViewRowCursor.MoveNext"/>.
/// </summary>
[BestFriend]
internal abstract class LinkedRootCursorBase : RootCursorBase
{
 
    /// <summary>Gets the input cursor.</summary>
    protected DataViewRowCursor Input { get; }
 
    /// <summary>
    /// Returns the root cursor of the input. It should be used to perform <see cref="DataViewRowCursor.MoveNext"/>
    /// operations, but with the distinction, as compared to <see cref="SynchronizedCursorBase"/>, that this is not
    /// a simple passthrough, but rather very implementation specific. For example, a common usage of this class is
    /// on filter cursor implementations, where how that input cursor is consumed is very implementation specific.
    /// That is why this is <see langword="protected"/>, not <see langword="private"/>.
    /// </summary>
    protected DataViewRowCursor Root { get; }
 
    private bool _disposed;
 
    protected LinkedRootCursorBase(IChannelProvider provider, DataViewRowCursor input)
        : base(provider)
    {
        Ch.AssertValue(input, nameof(input));
 
        Input = input;
        Root = Input is SynchronizedCursorBase snycInput ? snycInput.Root : input;
    }
 
    protected override void Dispose(bool disposing)
    {
        if (_disposed)
            return;
        if (disposing)
        {
            Input.Dispose();
            // The base class should set the state to done under these circumstances.
 
        }
        _disposed = true;
        base.Dispose(disposing);
    }
}