duplicati/Duplicati/UnitTest/RandomErrorBackend.cs

// Copyright (C) 2025, The Duplicati Team
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using Duplicati.Library.Interface;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Duplicati.UnitTest
{
    public class RandomErrorBackend : IBackend, IStreamingBackend
    {
        static RandomErrorBackend() { WrappedBackend = "file"; }

        private static readonly Random random = new Random(42);

        public static string WrappedBackend { get; set; }

        private IStreamingBackend m_backend;
        public RandomErrorBackend()
        {
        }

        // ReSharper disable once UnusedMember.Global
        public RandomErrorBackend(string url, Dictionary<string, string> options)
        {
            var u = new Library.Utility.Uri(url).SetScheme(WrappedBackend).ToString();
            m_backend = (IStreamingBackend)Library.DynamicLoader.BackendLoader.GetBackend(u, options);
        }

        private void ThrowErrorRandom()
        {
            if (random.NextDouble() > 0.90)
                throw new Exception("Random upload failure");
        }
        #region IStreamingBackend implementation
        public async Task PutAsync(string remotename, Stream stream, CancellationToken cancelToken)
        {
            var uploadError = random.NextDouble() > 0.9;

            using (var f = new Library.Utility.ProgressReportingStream(stream, x => { if (uploadError && stream.Position > stream.Length / 2) throw new Exception("Random upload failure"); }))
                await m_backend.PutAsync(remotename, f, cancelToken).ConfigureAwait(false);
            ThrowErrorRandom();
        }
        public async Task GetAsync(string remotename, Stream stream, CancellationToken cancelToken)
        {
            ThrowErrorRandom();
            await m_backend.GetAsync(remotename, stream, cancelToken).ConfigureAwait(false);
            ThrowErrorRandom();
        }
        #endregion

        #region IBackend implementation
        public IAsyncEnumerable<IFileEntry> ListAsync(CancellationToken cancellationToken)
        {
            return m_backend.ListAsync(cancellationToken);
        }
        public async Task PutAsync(string remotename, string filename, CancellationToken cancelToken)
        {
            ThrowErrorRandom();
            await m_backend.PutAsync(remotename, filename, cancelToken).ConfigureAwait(false);
            ThrowErrorRandom();
        }
        public async Task GetAsync(string remotename, string filename, CancellationToken cancelToken)
        {
            ThrowErrorRandom();
            await m_backend.GetAsync(remotename, filename, cancelToken).ConfigureAwait(false);
            ThrowErrorRandom();
        }
        public async Task DeleteAsync(string remotename, CancellationToken cancelToken)
        {
            ThrowErrorRandom();
            await m_backend.DeleteAsync(remotename, cancelToken).ConfigureAwait(false);
            ThrowErrorRandom();
        }
        public Task TestAsync(CancellationToken cancelToken)
        {
            return m_backend.TestAsync(cancelToken);
        }
        public Task CreateFolderAsync(CancellationToken cancelToken)
        {
            return m_backend.CreateFolderAsync(cancelToken);
        }

        public Task<string[]> GetDNSNamesAsync(CancellationToken cancelToken) => m_backend.GetDNSNamesAsync(cancelToken);

        public string DisplayName
        {
            get
            {
                return "Random Error Backend";
            }
        }
        public string ProtocolKey
        {
            get
            {
                return "randomerror";
            }
        }
        public IList<ICommandLineArgument> SupportedCommands
        {
            get
            {
                if (m_backend == null)
                    try { return Duplicati.Library.DynamicLoader.BackendLoader.GetSupportedCommands(WrappedBackend + "://").ToList(); }
                    catch { }

                return m_backend.SupportedCommands;
            }
        }
        public string Description
        {
            get
            {
                return "A testing backend that randomly fails";
            }
        }
        #endregion
        #region IDisposable implementation
        public void Dispose()
        {
            if (m_backend != null)
                try { m_backend.Dispose(); }
                finally { m_backend = null; }
        }
        #endregion
    }
}