Added a bit more implementation for the Default TransferProvider.

src/NzbDrone.Core/Download/DownloadClientPath.cs

@@ -0,0 +1,8 @@
+namespace NzbDrone.Core.Download
+{
+    public class DownloadClientPath
+    {
+        public int DownloadClientId { get; set; }
+        public string Path { get; set; }
+    }
+}

src/NzbDrone.Core/NzbDrone.Core.csproj

@@ -503,6 +503,7 @@
     <Compile Include="Download\Clients\uTorrent\UTorrentTorrentStatus.cs" />
     <Compile Include="Download\Clients\Vuze\Vuze.cs" />
     <Compile Include="Download\CompletedDownloadService.cs" />
+    <Compile Include="Download\DownloadClientPath.cs" />
     <Compile Include="Download\DownloadClientStatus.cs" />
     <Compile Include="Download\DownloadEventHub.cs" />
     <Compile Include="Download\DownloadClientStatusRepository.cs" />
@@ -947,7 +948,10 @@
     <Compile Include="Qualities\QualitySource.cs" />
     <Compile Include="Qualities\Revision.cs" />
     <Compile Include="TransferProviders\Providers\DefaultTransfer.cs" />
+    <Compile Include="TransferProviders\Providers\DirectVirtualDiskProvider.cs" />
     <Compile Include="TransferProviders\Providers\Dummy.cs" />
+    <Compile Include="TransferProviders\Providers\EmptyVirtualDiskProvider.cs" />
+    <Compile Include="TransferProviders\Providers\MountVirtualDiskProvider.cs" />
     <Compile Include="TransferProviders\TransferProviderDefinition.cs" />
     <Compile Include="TransferProviders\TransferProviderRepository.cs" />
     <Compile Include="TransferProviders\Providers\CustomTransfer.cs" />

src/NzbDrone.Core/TransferProviders/ITransferProvider.cs

@@ -7,14 +7,10 @@ namespace NzbDrone.Core.TransferProviders
 {
     public interface ITransferProvider : IProvider
     {
-        // TODO: Perhaps change 'string' to 'DownloadClientPath' struct/class so we're more typesafe.
-
         // Whether the TransferProvider is ready to be accessed. (Useful for external transfers that may not have finished yet)
-        bool IsAvailable(string downloadClientPath);
-        bool IsAvailable(DownloadClientItem item);
+        bool IsAvailable(DownloadClientPath item);
 
-        // Returns a wrapper for the specific download. Optionally we might want to supply a 'tempDir' that's close to the series path, in case the TransferProvider needs an intermediate location.
-        IVirtualDiskProvider GetFileSystemWrapper(string downloadClientPath);
-        IVirtualDiskProvider GetFileSystemWrapper(DownloadClientItem item);
+        // Returns a wrapper for the specific download. Optionally we might want to supply a 'tempPath' that's close to the series path, in case the TransferProvider needs an intermediate location.
+        IVirtualDiskProvider GetFileSystemWrapper(DownloadClientPath item, string tempPath = null);
     }
 }

src/NzbDrone.Core/TransferProviders/IVirtualDiskProvider.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text;
 using NzbDrone.Common.Disk;
@@ -16,6 +17,9 @@ namespace NzbDrone.Core.TransferProviders
         // Returns recursive list of all files in the 'volume'/'filesystem'/'dataset' (whatever we want to call it).
         string[] GetFiles();
 
+        // Opens a readable stream.
+        Stream OpenFile(string vfsFilePath);
+
         // Copies file from the virtual filesystem to the actual one.
         TransferTask CopyFile(string vfsSourcePath, string destinationPath);
 

src/NzbDrone.Core/TransferProviders/Providers/DefaultTransfer.cs

@@ -1,7 +1,12 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using FluentValidation.Results;
+using NLog;
+using NzbDrone.Common.Disk;
+using NzbDrone.Common.EnsureThat;
+using NzbDrone.Core.Download;
 using NzbDrone.Core.ThingiProvider;
 
 namespace NzbDrone.Core.TransferProviders.Providers
@@ -9,6 +14,19 @@ namespace NzbDrone.Core.TransferProviders.Providers
     // Represents a local filesystem transfer.
     class DefaultTransfer : TransferProviderBase<NullConfig>
     {
+        private readonly Logger _logger;
+        private readonly IDiskProvider _diskProvider;
+        private readonly IDiskTransferService _transferService;
+
+        public override string Name => "Default";
+
+        public DefaultTransfer(IDiskTransferService transferService, IDiskProvider diskProvider, Logger logger)
+        {
+            _logger = logger;
+            _diskProvider = diskProvider;
+            _transferService = transferService;
+        }
+
         public override IEnumerable<ProviderDefinition> DefaultDefinitions
         {
             get
@@ -23,19 +41,39 @@ namespace NzbDrone.Core.TransferProviders.Providers
                 };
             }
         }
-        public override string Link
+
+        public override ValidationResult Test()
         {
-            get { throw new NotImplementedException(); }
+            throw new NotImplementedException();
         }
 
-        public override string Name
+        public override bool IsAvailable(DownloadClientPath item)
         {
-            get { throw new NotImplementedException(); }
+            if (item == null) return false;
+
+            var path = ResolvePath(item);
+
+            return _diskProvider.FolderExists(path) || _diskProvider.FileExists(path);
         }
 
-        public override ValidationResult Test()
+        // TODO: Give DirectVirtualDiskProvider the tempPath.
+        public override IVirtualDiskProvider GetFileSystemWrapper(DownloadClientPath item, string tempPath = null)
         {
-            throw new NotImplementedException();
+            var path = ResolvePath(item);
+
+            if (_diskProvider.FolderExists(path) || _diskProvider.FileExists(path))
+            {
+                // Expose a virtual filesystem with only that directory/file in it.
+                // This allows the caller to delete the directory if desired, but not it's siblings.
+                return new DirectVirtualDiskProvider(_diskProvider, _transferService, Path.GetDirectoryName(path), path);
+            }
+
+            return new EmptyVirtualDiskProvider();
+        }
+
+        protected string ResolvePath(DownloadClientPath path)
+        {
+            return path.Path;
         }
     }
 }

src/NzbDrone.Core/TransferProviders/Providers/DirectVirtualDiskProvider.cs

@@ -0,0 +1,103 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using NzbDrone.Common.Disk;
+using NzbDrone.Common.Extensions;
+using NzbDrone.Common.Timeline;
+using NzbDrone.Common.TPL;
+
+namespace NzbDrone.Core.TransferProviders.Providers
+{
+    public class DirectVirtualDiskProvider : IVirtualDiskProvider
+    {
+        private readonly IDiskProvider _diskProvider;
+        private readonly IDiskTransferService _transferService;
+        private readonly string _rootFolder;
+        private readonly List<string> _items;
+
+        public bool SupportStreaming => true;
+
+        public DirectVirtualDiskProvider(IDiskProvider diskProvider, IDiskTransferService transferService, string rootFolder, params string[] items)
+        {
+            _diskProvider = diskProvider;
+            _transferService = transferService;
+            _rootFolder = rootFolder;
+            _items = items.ToList();
+        }
+
+        public string[] GetFiles()
+        {
+            return _items.SelectMany(GetFiles).Select(_rootFolder.GetRelativePath).ToArray();
+        }
+
+        private string[] GetFiles(string sourcePath)
+        {
+            if (_diskProvider.FileExists(sourcePath))
+            {
+                return new [] { sourcePath };
+            }
+            else
+            {
+                return _diskProvider.GetFiles(sourcePath, SearchOption.AllDirectories);
+            }
+        }
+
+        public TransferTask MoveFile(string vfsSourcePath, string destinationPath)
+        {
+            return TransferFile(vfsSourcePath, destinationPath, TransferMode.Move);
+        }
+
+        public TransferTask CopyFile(string vfsSourcePath, string destinationPath)
+        {
+            return TransferFile(vfsSourcePath, destinationPath, TransferMode.Copy);
+        }
+
+        private TransferTask TransferFile(string vfsSourcePath, string destinationPath, TransferMode mode)
+        {
+            var sourcePath = ResolveVirtualPath(vfsSourcePath);
+
+            var fileSize = _diskProvider.GetFileSize(sourcePath);
+            var progress = new TimelineContext($"{mode} {Path.GetFileName(sourcePath)}", 0, fileSize);
+            var task = Task.Factory.StartNew(() =>
+            {
+                progress.UpdateState(TimelineState.Started);
+                _transferService.TransferFile(sourcePath, destinationPath, mode);
+                if (mode == TransferMode.Move && _items.Contains(vfsSourcePath))
+                {
+                    // If it was moved, then remove it from the list.
+                    _items.Remove(vfsSourcePath);
+                }
+                progress.FinishProgress();
+            });
+
+            return new TransferTask(progress, task);
+        }
+
+        public Stream OpenFile(string vfsFilePath)
+        {
+            var sourcePath = ResolveVirtualPath(vfsFilePath);
+
+            return _diskProvider.OpenReadStream(sourcePath);
+        }
+
+        private string ResolveVirtualPath(string virtualPath)
+        {
+            if (Path.IsPathRooted(virtualPath))
+            {
+                throw new InvalidOperationException("Path not valid in the virtual filesystem");
+            }
+
+            var basePath = virtualPath.Split(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar)[0];
+
+            if (!_items.Contains(basePath))
+            {
+                throw new InvalidOperationException("Path not valid in the virtual filesystem");
+            }
+
+            return Path.Combine(_rootFolder, virtualPath);
+        }
+    }
+}

src/NzbDrone.Core/TransferProviders/Providers/Dummy.cs

@@ -1,28 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using FluentValidation.Results;
-using NzbDrone.Core.ThingiProvider;
-
-namespace NzbDrone.Core.TransferProviders.Providers
-{
-    // Marks the files are permanently unavailable. Perhaps useful in fire-and-forget.
-    class Dummy : TransferProviderBase<NullConfig>
-    {
-        public override string Link
-        {
-            get { throw new NotImplementedException(); }
-        }
-
-        public override string Name
-        {
-            get { throw new NotImplementedException(); }
-        }
-
-        public override ValidationResult Test()
-        {
-            throw new NotImplementedException();
-        }
-    }
-}

src/NzbDrone.Core/TransferProviders/Providers/EmptyVirtualDiskProvider.cs

@@ -0,0 +1,32 @@
+using System;
+using System.IO;
+using System.Linq;
+
+namespace NzbDrone.Core.TransferProviders.Providers
+{
+    public class EmptyVirtualDiskProvider : IVirtualDiskProvider
+    {
+        public bool SupportStreaming => true;
+
+
+        public string[] GetFiles()
+        {
+            return new string[0];
+        }
+
+        public TransferTask MoveFile(string vfsSourcePath, string destinationPath)
+        {
+            throw new FileNotFoundException("File not found in virtual filesystem", vfsSourcePath);
+        }
+
+        public TransferTask CopyFile(string vfsSourcePath, string destinationPath)
+        {
+            throw new FileNotFoundException("File not found in virtual filesystem", vfsSourcePath);
+        }
+
+        public Stream OpenFile(string vfsFilePath)
+        {
+            throw new FileNotFoundException("File not found in virtual filesystem", vfsFilePath);
+        }
+    }
+}

src/NzbDrone.Core/TransferProviders/Providers/MountTransfer.cs

@@ -1,6 +1,10 @@
 using System;
+using System.IO;
 using System.Linq;
 using FluentValidation.Results;
+using NLog;
+using NzbDrone.Common.Disk;
+using NzbDrone.Core.Download;
 using NzbDrone.Core.ThingiProvider;
 using NzbDrone.Core.Validation;
 
@@ -21,18 +25,51 @@ namespace NzbDrone.Core.TransferProviders.Providers
 
     public class MountTransfer : TransferProviderBase<MountSettings>
     {
-        public override string Link
+        private readonly Logger _logger;
+        private readonly IDiskProvider _diskProvider;
+        private readonly IDiskTransferService _transferService;
+
+        public override string Name => "Mount";
+
+        public MountTransfer(IDiskTransferService transferService, IDiskProvider diskProvider, Logger logger)
         {
-            get { throw new NotImplementedException(); }
+            _logger = logger;
+            _diskProvider = diskProvider;
+            _transferService = transferService;
         }
 
-        public override string Name
+        public override ValidationResult Test()
         {
-            get { throw new NotImplementedException(); }
+            throw new NotImplementedException();
         }
 
-        public override ValidationResult Test()
+        public override bool IsAvailable(DownloadClientPath item)
+        {
+            if (item == null) return false;
+
+            var path = ResolvePath(item);
+
+            return _diskProvider.FolderExists(path) || _diskProvider.FileExists(path);
+        }
+
+        // TODO: Give MountVirtualDiskProvider the tempPath.
+        public override IVirtualDiskProvider GetFileSystemWrapper(DownloadClientPath item, string tempPath = null)
+        {
+            var path = ResolvePath(item);
+
+            if (_diskProvider.FolderExists(path) || _diskProvider.FileExists(path))
+            {
+                // Expose a virtual filesystem with only that directory/file in it.
+                // This allows the caller to delete the directory if desired, but not it's siblings.
+                return new MountVirtualDiskProvider(_diskProvider, _transferService, Path.GetDirectoryName(path), path);
+            }
+
+            return new EmptyVirtualDiskProvider();
+        }
+
+        protected string ResolvePath(DownloadClientPath path)
         {
+            // Same logic as RemotePathMapping service.
             throw new NotImplementedException();
         }
     }

src/NzbDrone.Core/TransferProviders/Providers/MountVirtualDiskProvider.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using NzbDrone.Common.Disk;
+
+namespace NzbDrone.Core.TransferProviders.Providers
+{
+    // Empty wrapper, it would server in dealing with stuff being slower and remote mounts potentially being unavailable temporarily.
+    // Ideally it should wrap a DirectVirtualDiskProvider instance, rather than inheriting from it.
+    public class MountVirtualDiskProvider : DirectVirtualDiskProvider
+    {
+        public MountVirtualDiskProvider(IDiskProvider diskProvider, IDiskTransferService transferService, string rootFolder, params string[] items)
+            : base(diskProvider, transferService, rootFolder, items)
+        {
+
+        }
+    }
+}

src/NzbDrone.Core/TransferProviders/TransferProviderBase.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using FluentValidation.Results;
+using NzbDrone.Core.Download;
 using NzbDrone.Core.ThingiProvider;
 
 namespace NzbDrone.Core.TransferProviders
@@ -19,8 +20,10 @@ namespace NzbDrone.Core.TransferProviders
         public ProviderDefinition Definition { get; set; }
         public abstract ValidationResult Test();
 
-        public abstract string Link { get; }
-
         public virtual object RequestAction(string action, IDictionary<string, string> query) { return null; }
+
+        public abstract bool IsAvailable(DownloadClientPath item);
+
+        public abstract IVirtualDiskProvider GetFileSystemWrapper(DownloadClientPath item, string tempPath = null);
     }
 }

src/NzbDrone.Core/TransferProviders/TransferTask.cs

@@ -2,13 +2,22 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using System.Threading.Tasks;
+using NzbDrone.Common.Timeline;
 
 namespace NzbDrone.Core.TransferProviders
 {
     public class TransferTask
     {
-        // TODO: Progress reporting
+        public ITimelineContext Timeline { get; private set; }
 
-        // TODO: Async task or waitable object so Importing can handle.
+        // Async task that is completed once the Transfer has finished or ended in failure. (Do not rely on ProgressReporter for finished detection)
+        public Task CompletionTask { get; private set; }
+
+        public TransferTask(ITimelineContext timeline, Task completionTask)
+        {
+            Timeline = timeline;
+            CompletionTask = completionTask.ContinueWith(t => Timeline.FinishProgress());
+        }
     }
 }