[core] Use an immutable approach to overriding core functionality

Require the user of the library to create the 'Factories' object
before initializing the engine, and ensure 'Factories' is immutable.

If someone wants to enable/disable something core, like proxy support,
then it's far easier to do that safely/reliably if they also instantiate
a new ClientEngine object.

These are things which should not change for the lifetime of a torrent,
unlike the more mutable EngineSettings or ClientSettings.

src/DotNetCoreSample/DotNetCoreSample.csproj

@@ -8,6 +8,7 @@
   <ItemGroup>
     <ProjectReference Include="..\MonoTorrent.BEncoding\MonoTorrent.BEncoding.csproj" />
     <ProjectReference Include="..\MonoTorrent.Client\MonoTorrent.Client.csproj" />
+    <ProjectReference Include="..\MonoTorrent.Factories\MonoTorrent.Factories.csproj" />
     <ProjectReference Include="..\MonoTorrent.PieceWriter\MonoTorrent.PieceWriter.csproj" />
     <ProjectReference Include="..\MonoTorrent\MonoTorrent.csproj" />
   </ItemGroup>

src/MonoTorrent.Client/MonoTorrent.Client.Connections/HttpPeerConnection.cs

@@ -68,6 +68,8 @@ public HttpRequestData (RequestMessage request)
 
         public bool Disposed { get; set; }
 
+        Factories.HttpRequestCreator RequestCreator { get; }
+
         IHttpRequest Requester { get; set; }
 
         public TimeSpan ConnectionTimeout {
@@ -103,9 +105,10 @@ public TimeSpan ConnectionTimeout {
 
         #region Constructors
 
-        public HttpPeerConnection (ITorrentData torrentData, Uri uri)
+        public HttpPeerConnection (ITorrentData torrentData, Factories.HttpRequestCreator requestCreator, Uri uri)
         {
             ConnectionTimeout = TimeSpan.FromSeconds (10);
+            RequestCreator = requestCreator;
             TorrentData = torrentData ?? throw new ArgumentNullException (nameof (torrentData));
             Uri = uri;
         }
@@ -212,7 +215,7 @@ public async ReusableTask<int> ReceiveAsync (ByteBuffer buffer, int offset, int
                 var rr = WebRequests.Dequeue ();
 
                 Requester?.Dispose ();
-                Requester = HttpRequestFactory.Create ();
+                Requester = RequestCreator ();
                 Requester.ConnectionTimeout = ConnectionTimeout;
                 DataStream = await Requester.GetStreamAsync (rr.fileUri, rr.startOffset, rr.count);
                 DataStreamCount = rr.count;

src/MonoTorrent.Client/MonoTorrent.Client/ClientEngine.cs

@@ -32,6 +32,7 @@
 using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -202,6 +203,8 @@ public async Task SaveStateAsync (string pathToStateFile)
 
         public bool Disposed { get; private set; }
 
+        internal Factories Factories { get; }
+
         internal IPeerConnectionListener Listener { get; set; }
 
         internal ILocalPeerDiscovery LocalPeerDiscovery { get; private set; }
@@ -252,8 +255,15 @@ public ClientEngine ()
         }
 
         public ClientEngine (EngineSettings settings)
+            : this (settings, Factories.Default)
+        {
+
+        }
+
+        public ClientEngine (EngineSettings settings, Factories factories)
         {
             settings = settings ?? throw new ArgumentNullException (nameof (settings));
+            Factories = factories ?? throw new ArgumentNullException (nameof (factories));
 
             // This is just a sanity check to make sure the ReusableTasks.dll assembly is
             // loadable.
@@ -267,9 +277,9 @@ public ClientEngine (EngineSettings settings)
             publicTorrents = new List<TorrentManager> ();
             Torrents = new ReadOnlyCollection<TorrentManager> (publicTorrents);
 
-            DiskManager = new DiskManager (Settings);
+            DiskManager = new DiskManager (Settings, Factories);
 
-            ConnectionManager = new ConnectionManager (PeerId, Settings, DiskManager);
+            ConnectionManager = new ConnectionManager (PeerId, Settings, Factories, DiskManager);
             listenManager = new ListenManager (this);
             PortForwarder = new MonoNatPortForwarder ();
 
@@ -290,15 +300,15 @@ public ClientEngine (EngineSettings settings)
                 uploadLimiter
             };
 
-            Listener = PeerListenerFactory.CreateTcp (settings.ListenPort) ?? new NullPeerListener ();
+            Listener = (settings.ListenPort == -1 ? null : Factories.CreatePeerConnectionListener (new IPEndPoint (IPAddress.Any, settings.ListenPort))) ?? new NullPeerListener ();
             listenManager.SetListener (Listener);
 
-            DhtListener = DhtListenerFactory.CreateUdp (settings.DhtPort) ?? new NullDhtListener ();
+            DhtListener = (settings.DhtPort == -1 ? null : Factories.CreateDhtListener (new IPEndPoint (IPAddress.Any, settings.DhtPort))) ?? new NullDhtListener ();
             DhtEngine = settings.DhtPort == -1 ? new NullDhtEngine () : DhtEngineFactory.Create (DhtListener);
             DhtEngine.StateChanged += DhtEngineStateChanged;
             DhtEngine.PeersFound += DhtEnginePeersFound;
 
-            RegisterLocalPeerDiscovery (settings.AllowLocalPeerDiscovery && settings.ListenPort > 0 ? LocalPeerDiscoveryFactory.Create (settings.ListenPort) : null);
+            RegisterLocalPeerDiscovery (settings.AllowLocalPeerDiscovery && settings.ListenPort >= 0 ? Factories.CreateLocalPeerDiscovery (settings.ListenPort) : null);
         }
 
         #endregion
@@ -400,7 +410,7 @@ public async Task<TorrentManager> AddStreamingAsync (Torrent torrent, string sav
 
         async Task<TorrentManager> MakeStreamingAsync (TorrentManager manager)
         {
-            await manager.ChangePickerAsync (PieceRequesterFactory.CreateStreamingPieceRequester (manager));
+            await manager.ChangePickerAsync (Factories.CreateStreamingPieceRequester (manager));
             return manager;
         }
 
@@ -879,7 +889,7 @@ async Task UpdateSettingsAsync (EngineSettings oldSettings, EngineSettings newSe
                 else if (oldSettings.DhtPort > 0)
                     await PortForwarder.UnregisterMappingAsync (new Mapping (Protocol.Udp, oldSettings.DhtPort), CancellationToken.None);
 
-                DhtListener = DhtListenerFactory.CreateUdp (newSettings.DhtPort) ?? new NullDhtListener ();
+                DhtListener = (newSettings.DhtPort == -1 ? null : Factories.CreateDhtListener (new IPEndPoint (IPAddress.Any, newSettings.DhtPort))) ?? new NullDhtListener ();
                 if (oldSettings.DhtPort == -1)
                     await RegisterDht (DhtEngineFactory.Create (DhtListener));
                 else if (newSettings.DhtPort == -1)
@@ -903,7 +913,7 @@ async Task UpdateSettingsAsync (EngineSettings oldSettings, EngineSettings newSe
                     await PortForwarder.UnregisterMappingAsync (new Mapping (Protocol.Tcp, oldSettings.ListenPort), CancellationToken.None);
 
                 Listener.Stop ();
-                Listener = PeerListenerFactory.CreateTcp (newSettings.ListenPort) ?? new NullPeerListener ();
+                Listener = (newSettings.ListenPort == -1 ? null : Factories.CreatePeerConnectionListener (new IPEndPoint (IPAddress.Any, newSettings.ListenPort))) ?? new NullPeerListener ();
                 listenManager.SetListener (Listener);
 
                 if (IsRunning) {
@@ -923,7 +933,7 @@ async Task UpdateSettingsAsync (EngineSettings oldSettings, EngineSettings newSe
 
             if ((oldSettings.AllowLocalPeerDiscovery != newSettings.AllowLocalPeerDiscovery) ||
                 (oldSettings.ListenPort != newSettings.ListenPort)) {
-                RegisterLocalPeerDiscovery (newSettings.AllowLocalPeerDiscovery && localPort > 0 ? LocalPeerDiscoveryFactory.Create (localPort) : null);
+                RegisterLocalPeerDiscovery (!newSettings.AllowLocalPeerDiscovery || localPort <= 0 ? null : Factories.CreateLocalPeerDiscovery(localPort));
             }
         }
 

src/MonoTorrent.Client/MonoTorrent.Client/FactoriesExtensions.cs

@@ -0,0 +1,20 @@
+using System;
+
+using MonoTorrent.Client.Connections;
+
+namespace MonoTorrent.Client
+{
+    static class FactoriesExtensions
+    {
+        public static IPeerConnection CreatePeerConnection(this Factories factories, Uri uri)
+        {
+            try {
+                if (factories.PeerConnectionCreators.TryGetValue (uri.Scheme, out var creator))
+                    return creator (uri);
+            } catch {
+
+            }
+            return null;
+        }
+    }
+}

src/MonoTorrent.Client/MonoTorrent.Client/Managers/ConnectionManager.cs

@@ -72,6 +72,8 @@ public AsyncConnectState (TorrentManager manager, IPeerConnection connection, Va
 
         internal DiskManager DiskManager { get; }
 
+        Factories Factories { get; }
+
         internal BEncodedString LocalPeerId { get; }
 
         /// <summary>
@@ -97,14 +99,14 @@ public AsyncConnectState (TorrentManager manager, IPeerConnection connection, Va
         List<AsyncConnectState> PendingConnects { get; }
 
         internal EngineSettings Settings { get; set; }
-
         internal List<TorrentManager> Torrents { get; set; }
 
-        internal ConnectionManager (BEncodedString localPeerId, EngineSettings settings, DiskManager diskManager)
+        internal ConnectionManager (BEncodedString localPeerId, EngineSettings settings, Factories factories, DiskManager diskManager)
         {
             DiskManager = diskManager ?? throw new ArgumentNullException (nameof (diskManager));
             LocalPeerId = localPeerId ?? throw new ArgumentNullException (nameof (localPeerId));
             Settings = settings ?? throw new ArgumentNullException (nameof (settings));
+            Factories = factories ?? throw new ArgumentNullException (nameof (factories));
 
             PendingConnects = new List<AsyncConnectState> ();
             Torrents = new List<TorrentManager> ();
@@ -123,7 +125,7 @@ internal void Remove (TorrentManager manager)
         async void ConnectToPeer (TorrentManager manager, Peer peer)
         {
             // Connect to the peer.
-            var connection = PeerConnectionFactory.Create (peer.ConnectionUri);
+            var connection = Factories.CreatePeerConnection (peer.ConnectionUri);
             if (connection == null || peer.AllowedEncryption.Count == 0)
                 return;
 

src/MonoTorrent.Client/MonoTorrent.Client/Managers/DiskManager.cs

@@ -174,7 +174,7 @@ public BufferedIO (ITorrentData manager, BlockInfo request, byte[] buffer, bool
         /// </summary>
         IBlockCache Cache { get; }
 
-        internal DiskManager (EngineSettings settings, IPieceWriter writer = null)
+        internal DiskManager (EngineSettings settings, Factories factories, IPieceWriter writer = null)
         {
             ReadLimiter = new RateLimiter ();
             ReadQueue = new Queue<BufferedIO> ();
@@ -186,8 +186,8 @@ internal DiskManager (EngineSettings settings, IPieceWriter writer = null)
 
             Settings = settings ?? throw new ArgumentNullException (nameof (settings));
 
-            writer ??= PieceWriterFactory.Create (settings.MaximumOpenFiles);
-            Cache = BlockCacheFactory.Create (writer, settings.DiskCacheBytes, BufferPool);
+            writer ??= factories.CreatePieceWriter (settings.MaximumOpenFiles);
+            Cache = factories.CreateBlockCache (writer, settings.DiskCacheBytes, BufferPool);
             Cache.ReadThroughCache += (o, e) => WriterReadMonitor.AddDelta (e.RequestLength);
             Cache.WrittenThroughCache += (o, e) => WriterWriteMonitor.AddDelta (e.RequestLength);
         }

src/MonoTorrent.Client/MonoTorrent.Client/Managers/PieceManager.cs

@@ -64,7 +64,7 @@ internal PieceManager (TorrentManager manager)
         {
             Manager = manager;
             PendingHashCheckPieces = new MutableBitField (1);
-            Requester = PieceRequesterFactory.CreateStandardPieceRequester (manager);
+            Requester = manager.Engine.Factories.CreatePieceRequester (manager);
         }
 
         internal bool PieceDataReceived (PeerId id, PieceMessage message, out bool pieceComplete, out IList<IPeer> peersInvolved)

src/MonoTorrent.Client/MonoTorrent.Client/Modes/Mode.cs

@@ -599,7 +599,7 @@ void DownloadLogic (int counter)
 
                     var peer = new Peer (peerId, uri);
 
-                    var connection = new HttpPeerConnection (Manager, uri);
+                    var connection = new HttpPeerConnection (Manager, Manager.Engine.Factories.CreateHttpRequest, uri);
                     // Unsupported connection type.
                     if (connection == null)
                         continue;

src/MonoTorrent.Client/MonoTorrent.Client/Settings/EngineSettingsBuilder.cs

@@ -346,4 +346,4 @@ static int CheckZeroOrPositive (int value)
             return value;
         }
     }
-}
+}

src/MonoTorrent.Client/MonoTorrent.Dht/DhtEngine.cs

@@ -82,15 +82,6 @@ public class DhtEngine : IDisposable, IDhtEngine
 
         #region Constructors
 
-        /// <summary>
-        /// Creates a new DhtEngine which listens for connections on the given endpoint
-        /// </summary>
-        /// <param name="listenerEndpoint">The IPAddresss/port which the engine should listen on</param>
-        public DhtEngine (IPEndPoint listenerEndpoint)
-            : this (DhtListenerFactory.CreateUdp (listenerEndpoint))
-        {
-        }
-
         public DhtEngine (IDhtListener listener)
         {
             if (listener == null)

src/MonoTorrent.Client/MonoTorrent/TorrentCreator.cs

@@ -131,11 +131,14 @@ public static int RecommendedPieceSize (IEnumerable<FileMapping> files)
 
         internal TimeSpan CreationTime { get; set; }
 
-        public TorrentCreator ()
+        Factories.PieceWriterCreator PieceWriterCreator { get; }
+
+        public TorrentCreator (Factories.PieceWriterCreator pieceWriterCreator)
         {
             GetrightHttpSeeds = new List<string> ();
             CanEditSecureMetadata = true;
             CreatedBy = $"MonoTorrent {VersionInfo.Version}";
+            PieceWriterCreator = pieceWriterCreator;
         }
 
         public BEncodedDictionary Create (ITorrentFileSource fileSource)
@@ -302,7 +305,7 @@ async Task<byte[]> CalcPiecesHash (int startPiece, long totalBytesToRead, Synchr
             var filledBuffers = new AsyncProducerConsumerQueue<(byte[], int, InputFile)> (emptyBuffers.Capacity + 1);
 
             // This is the IPieceWriter which we'll use to get our filestream. Each thread gets it's own writer.
-            using IPieceWriter writer = CreateReader ();
+            using IPieceWriter writer = PieceWriterCreator (3);
 
             // Read from the disk in 256kB chunks, instead of 16kB, as a performance optimisation.
             // As the capacity is set to 4, this means we'll have 1 megabyte of buffers to handle.
@@ -480,11 +483,6 @@ void CreateMultiFileTorrent (BEncodedDictionary dictionary, List<InputFile> mapp
             info.Add ("files", new BEncodedList (files));
         }
 
-        protected virtual IPieceWriter CreateReader ()
-        {
-            return PieceWriterFactory.Create (10);
-        }
-
         void CreateSingleFileTorrent (BEncodedDictionary dictionary, IList<InputFile> mappings)
         {
             var infoDict = (BEncodedDictionary) dictionary["info"];