// 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 System;
using Microsoft.ML.Runtime;
 
namespace Microsoft.ML.Data;
 
/// <summary>
/// Convenient base class for <see cref="DataViewRow"/> implementors that wrap a single <see cref="DataViewRow"/>
/// as their input. The <see cref="DataViewRow.Position"/>, <see cref="DataViewRow.Batch"/>, and <see cref="DataViewRow.GetIdGetter"/>
/// are taken from this <see cref="Input"/>.
/// </summary>
[BestFriend]
internal abstract class WrappingRow : DataViewRow
{
    private bool _disposed;
 
    /// <summary>
    /// The wrapped input row.
    /// </summary>
    protected DataViewRow Input { get; }
 
    public sealed override long Batch => Input.Batch;
    public sealed override long Position => Input.Position;
    public override ValueGetter<DataViewRowId> GetIdGetter() => Input.GetIdGetter();
 
    [BestFriend]
    private protected WrappingRow(DataViewRow input)
    {
        Contracts.AssertValue(input);
        Input = input;
    }
 
    /// <summary>
    /// This override of the dispose method by default only calls <see cref="Input"/>'s
    /// <see cref="IDisposable.Dispose"/> method, but subclasses can enable additional functionality
    /// via the <see cref="DisposeCore(bool)"/> functionality.
    /// </summary>
    /// <param name="disposing"></param>
    protected sealed override void Dispose(bool disposing)
    {
        if (_disposed)
            return;
        // Since the input was created first, and this instance may depend on it, we should
        // dispose local resources first before potentially disposing the input row resources.
        DisposeCore(disposing);
        if (disposing)
            Input.Dispose();
        _disposed = true;
    }
 
    /// <summary>
    /// Called from <see cref="Dispose(bool)"/> with <see langword="true"/> in the case where
    /// that method has never been called before, and right after <see cref="Input"/> has been
    /// disposed. The default implementation does nothing.
    /// </summary>
    /// <param name="disposing">Whether this was called through the dispose path, as opposed
    /// to the finalizer path.</param>
    protected virtual void DisposeCore(bool disposing)
    {
    }
}