// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Xml.Linq;
using Microsoft.AspNetCore.Shared;
using Microsoft.Extensions.Logging;

namespace Microsoft.AspNetCore.DataProtection.XmlEncryption;

/// <summary>
/// An <see cref="IXmlEncryptor"/> that encrypts XML elements with a null encryptor.
/// </summary>
public sealed class NullXmlEncryptor : IXmlEncryptor
{
    private readonly ILogger _logger;

    /// <summary>
    /// Creates a new instance of <see cref="NullXmlEncryptor"/>.
    /// </summary>
    public NullXmlEncryptor()
        : this(services: null)
    {
    }

    /// <summary>
    /// Creates a new instance of <see cref="NullXmlEncryptor"/>.
    /// </summary>
    /// <param name="services">An optional <see cref="IServiceProvider"/> to provide ancillary services.</param>
    public NullXmlEncryptor(IServiceProvider? services)
    {
        _logger = services.GetLogger<NullXmlEncryptor>();
    }

    /// <summary>
    /// Encrypts the specified <see cref="XElement"/> with a null encryptor, i.e.,
    /// by returning the original value of <paramref name="plaintextElement"/> unencrypted.
    /// </summary>
    /// <param name="plaintextElement">The plaintext to echo back.</param>
    /// <returns>
    /// An <see cref="EncryptedXmlInfo"/> that contains the null-encrypted value of
    /// <paramref name="plaintextElement"/> along with information about how to
    /// decrypt it.
    /// </returns>
    public EncryptedXmlInfo Encrypt(XElement plaintextElement)
    {
        ArgumentNullThrowHelper.ThrowIfNull(plaintextElement);

        _logger.EncryptingUsingNullEncryptor();

        // <unencryptedKey>
        //   <!-- This key is not encrypted. -->
        //   <plaintextElement />
        // </unencryptedKey>

        var newElement = new XElement("unencryptedKey",
            new XComment(" This key is not encrypted. "),
            new XElement(plaintextElement) /* copy ctor */);

        return new EncryptedXmlInfo(newElement, typeof(NullXmlDecryptor));
    }
}