HttpServerUtility.cs

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

using System.Collections.Specialized;
using System.ComponentModel;
using System.IO;
using System.Web.Hosting;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.SystemWebAdapters;
using Microsoft.AspNetCore.SystemWebAdapters.Features;
using Microsoft.AspNetCore.WebUtilities;
using Microsoft.Extensions.DependencyInjection;

namespace System.Web;

[Diagnostics.CodeAnalysis.SuppressMessage("Performance", "CA1822:Mark members as static", Justification = Constants.ApiFromAspNet)]
public class HttpServerUtility
{
    private readonly HttpContextCore _context;

    internal HttpServerUtility(HttpContextCore context)
    {
        _context = context;
    }

    public string MachineName => Environment.MachineName;

    public string MapPath(string? path)
        => _context.RequestServices.GetRequiredService<IMapPathUtility>().MapPath(_context.Request.Path, path);

    public Exception? GetLastError() => _context.AsSystemWeb().Error;

    public void ClearError() => _context.AsSystemWeb().ClearError();

    /// <summary>
    /// This method is similar to <see cref="WebEncoders.Base64UrlDecode(string)"/> but handles the trailing character that <see cref="UrlTokenEncode(byte[])"/>
    /// appends to the string.
    /// </summary>
    /// <param name="input">Value to decode</param>
    /// <returns>Decoded value.</returns>
    /// <exception cref="ArgumentNullException"></exception>
    public static byte[]? UrlTokenDecode(string input)
    {
        ArgumentNullException.ThrowIfNull(input);

        if (input.Length == 0)
        {
            return Array.Empty<byte>();
        }

        // The number of padding chars is expected to be the final character of the string
        if (!IsDigit(input[^1]))
        {
            return null;
        }

        return WebEncoders.Base64UrlDecode(input, 0, input.Length - 1);

        static bool IsDigit(char c) => (uint)(c - '0') <= (uint)('9' - '0');
    }


    /// <summary>
    /// This method is similar to <see cref="WebEncoders.Base64UrlEncode(byte[])"/> but the resulting string includes an extra character
    /// that is the count of how many padding characters where removed from the Base64 encoded value.
    /// </summary>
    /// <param name="input">Value to encode</param>
    /// <returns>URL encoded value.</returns>
    /// <exception cref="ArgumentNullException"></exception>
    [Diagnostics.CodeAnalysis.SuppressMessage("Design", "CA1055:URI-like return values should not be strings", Justification = Constants.ApiFromAspNet)]
    public static string UrlTokenEncode(byte[] input)
    {
        ArgumentNullException.ThrowIfNull(input);

        if (input.Length == 0)
        {
            return string.Empty;
        }

        var encoded = WebEncoders.Base64UrlEncode(input);
        var padding = (encoded.Length % 4) switch
        {
            0 => 0,
            2 => 2,
            3 => 1,
            _ => throw new FormatException("Invalid input"),
        };

        return $"{encoded}{padding}";
    }

    [Obsolete(Constants.Execute.Message, DiagnosticId = Constants.Execute.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void Execute(string path) => Execute(path, null, preserveForm: true);

    [Obsolete(Constants.Execute.Message, DiagnosticId = Constants.Execute.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void Execute(string path, TextWriter writer) => Execute(path, writer, preserveForm: true);

    [Obsolete(Constants.Execute.Message, DiagnosticId = Constants.Execute.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void Execute(string path, bool preserveForm) => Execute(path, null, preserveForm);

    [Obsolete(Constants.Execute.Message, DiagnosticId = Constants.Execute.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void Execute(string path, TextWriter? writer, bool preserveForm) => _context.Features.GetRequiredFeature<ITransferRequestFeature>().Execute(path, writer, preserveForm);

    [Obsolete(Constants.Transfer.Message, DiagnosticId = Constants.Transfer.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void Transfer(string path) => Transfer(path, preserveForm: true);

    [Obsolete(Constants.Transfer.Message, DiagnosticId = Constants.Transfer.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void Transfer(string path, bool preserveForm)
    {
        _context.Features.GetRequiredFeature<ITransferRequestFeature>().Transfer(path, preserveForm);
        _context.Response.AsSystemWeb().End();
    }

    [Obsolete(Constants.TransferRequest.Message, DiagnosticId = Constants.TransferRequest.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void TransferRequest(string path)
        => TransferRequest(path, false, null, null, preserveUser: true);

    [Obsolete(Constants.TransferRequest.Message, DiagnosticId = Constants.TransferRequest.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void TransferRequest(string path, bool preserveForm)
        => TransferRequest(path, preserveForm, null, null, preserveUser: true);

    [Obsolete(Constants.TransferRequest.Message, DiagnosticId = Constants.TransferRequest.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void TransferRequest(string path, bool preserveForm, string? method, NameValueCollection? headers)
        => TransferRequest(path, preserveForm, method, headers, preserveUser: true);

    [Obsolete(Constants.TransferRequest.Message, DiagnosticId = Constants.TransferRequest.DiagnosticId)]
    [EditorBrowsable(EditorBrowsableState.Never)]
    public void TransferRequest(string path, bool preserveForm, string? method, NameValueCollection? headers, bool preserveUser)
        => _context.Features.GetRequiredFeature<ITransferRequestFeature>().TransferRequest(path, preserveForm, method, headers, preserveUser);
}