Implement a rudimentary applets system (#804)

* Implement Player Select applet

* Initialize the Horizon system reference

* Tidy up namespaces

* Resolve nits

* Resolve nits

* Rename stack to queue

* Implement an applet FIFO

* Remove debugging log

* Log applet creation events

* Reorganise AppletFifo

* More reorganisation

* Final changes

8 files changed, 245 insertions, 14 deletions

diff --git a/Ryujinx.HLE/HOS/Applets/AppletManager.cs b/Ryujinx.HLE/HOS/Applets/AppletManager.cs
new file mode 100644
index 00000000..e5426cd7
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Applets/AppletManager.cs
@@ -0,0 +1,29 @@
+using Ryujinx.HLE.HOS.Services.Am.AppletAE;
+using System;
+using System.Collections.Generic;
+
+namespace Ryujinx.HLE.HOS.Applets
+{
+    static class AppletManager
+    {
+        private static Dictionary<AppletId, Type> _appletMapping;
+
+        static AppletManager()
+        {
+            _appletMapping = new Dictionary<AppletId, Type>
+            {
+                { AppletId.PlayerSelect, typeof(PlayerSelectApplet) }
+            };
+        }
+
+        public static IApplet Create(AppletId applet, Horizon system)
+        {
+            if (_appletMapping.TryGetValue(applet, out Type appletClass))
+            {
+                return (IApplet)Activator.CreateInstance(appletClass, system);
+            }
+
+            throw new NotImplementedException($"{applet} applet is not implemented.");
+        }
+    }
+}
diff --git a/Ryujinx.HLE/HOS/Applets/IApplet.cs b/Ryujinx.HLE/HOS/Applets/IApplet.cs
new file mode 100644
index 00000000..aa248bf5
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Applets/IApplet.cs
@@ -0,0 +1,13 @@
+using Ryujinx.HLE.HOS.Services.Am.AppletAE;
+using System;
+
+namespace Ryujinx.HLE.HOS.Applets
+{
+    interface IApplet
+    {
+        event EventHandler AppletStateChanged;
+
+        ResultCode Start(AppletFifo<byte[]> inData, AppletFifo<byte[]> outData);
+        ResultCode GetResult();
+    }
+}
diff --git a/Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectApplet.cs b/Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectApplet.cs
new file mode 100644
index 00000000..7658c6db
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectApplet.cs
@@ -0,0 +1,55 @@
+using Ryujinx.HLE.HOS.Services.Account.Acc;
+using Ryujinx.HLE.HOS.Services.Am.AppletAE;
+using System;
+using System.IO;
+
+namespace Ryujinx.HLE.HOS.Applets
+{
+    internal class PlayerSelectApplet : IApplet
+    {
+        private Horizon _system;
+
+        private AppletFifo<byte[]> _inputData;
+        private AppletFifo<byte[]> _outputData;
+
+        public event EventHandler AppletStateChanged;
+
+        public PlayerSelectApplet(Horizon system)
+        {
+            _system = system;
+        }
+
+        public ResultCode Start(AppletFifo<byte[]> inData, AppletFifo<byte[]> outData)
+        {
+            _inputData  = inData;
+            _outputData = outData;
+
+            // TODO(jduncanator): Parse PlayerSelectConfig from input data
+            _outputData.Push(BuildResponse());
+
+            AppletStateChanged?.Invoke(this, null);
+
+            return ResultCode.Success;
+        }
+
+        public ResultCode GetResult()
+        {
+            return ResultCode.Success;
+        }
+
+        private byte[] BuildResponse()
+        {
+            UserProfile currentUser = _system.State.Account.LastOpenedUser;
+
+            using (MemoryStream stream = new MemoryStream())
+            using (BinaryWriter writer = new BinaryWriter(stream))
+            {
+                writer.Write((ulong)PlayerSelectResult.Success);
+
+                currentUser.UserId.Write(writer);
+
+                return stream.ToArray();
+            }
+        }
+    }
+}
diff --git a/Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectResult.cs b/Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectResult.cs
new file mode 100644
index 00000000..682e094e
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectResult.cs
@@ -0,0 +1,8 @@
+namespace Ryujinx.HLE.HOS.Applets
+{
+    enum PlayerSelectResult : ulong
+    {
+        Success = 0,
+        Failure = 2
+    }
+}
diff --git a/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/LibraryAppletCreator/ILibraryAppletAccessor.cs b/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/LibraryAppletCreator/ILibraryAppletAccessor.cs
index 9d8e2a96..8c4d1008 100644
--- a/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/LibraryAppletCreator/ILibraryAppletAccessor.cs
+++ b/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/LibraryAppletCreator/ILibraryAppletAccessor.cs
@@ -1,19 +1,37 @@
 using Ryujinx.Common.Logging;
+using Ryujinx.HLE.HOS.Applets;
 using Ryujinx.HLE.HOS.Ipc;
 using Ryujinx.HLE.HOS.Kernel.Common;
 using Ryujinx.HLE.HOS.Kernel.Threading;
-using Ryujinx.HLE.HOS.Services.Am.AppletAE.Storage;
 using System;
 
 namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.LibraryAppletCreator
 {
     class ILibraryAppletAccessor : IpcService
     {
+        private IApplet _applet;
+
+        private AppletFifo<byte[]> _inData;
+        private AppletFifo<byte[]> _outData;
+
         private KEvent _stateChangedEvent;
 
-        public ILibraryAppletAccessor(Horizon system)
+        public ILibraryAppletAccessor(AppletId appletId, Horizon system)
         {
             _stateChangedEvent = new KEvent(system);
+
+            _applet  = AppletManager.Create(appletId, system);
+            _inData  = new AppletFifo<byte[]>();
+            _outData = new AppletFifo<byte[]>();
+            
+            _applet.AppletStateChanged += OnAppletStateChanged;
+            
+            Logger.PrintInfo(LogClass.ServiceAm, $"Applet '{appletId}' created.");
+        }
+
+        private void OnAppletStateChanged(object sender, EventArgs e)
+        {
+            _stateChangedEvent.ReadableEvent.Signal();
         }
 
         [Command(0)]
@@ -29,8 +47,6 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.Lib
 
             context.Response.HandleDesc = IpcHandleDesc.MakeCopy(handle);
 
-            Logger.PrintStub(LogClass.ServiceAm);
-
             return ResultCode.Success;
         }
 
@@ -38,25 +54,23 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.Lib
         // Start()
         public ResultCode Start(ServiceCtx context)
         {
-            Logger.PrintStub(LogClass.ServiceAm);
-
-            return ResultCode.Success;
+            return (ResultCode)_applet.Start(_inData, _outData);
         }
 
         [Command(30)]
         // GetResult()
         public ResultCode GetResult(ServiceCtx context)
         {
-            Logger.PrintStub(LogClass.ServiceAm);
-
-            return ResultCode.Success;
+            return (ResultCode)_applet.GetResult();
         }
 
         [Command(100)]
         // PushInData(object<nn::am::service::IStorage>)
         public ResultCode PushInData(ServiceCtx context)
         {
-            Logger.PrintStub(LogClass.ServiceAm);
+            IStorage data = GetObject<IStorage>(context, 0);
+
+            _inData.Push(data.Data);
 
             return ResultCode.Success;
         }
@@ -65,9 +79,11 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.Lib
         // PopOutData() -> object<nn::am::service::IStorage>
         public ResultCode PopOutData(ServiceCtx context)
         {
-            MakeObject(context, new IStorage(StorageHelper.MakeLaunchParams()));
+            byte[] data = _outData.Pop();
 
+            MakeObject(context, new IStorage(data));
+            
             return ResultCode.Success;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/SystemAppletProxy/ILibraryAppletCreator.cs b/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/SystemAppletProxy/ILibraryAppletCreator.cs
index 8b0b225b..094ed305 100644
--- a/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/SystemAppletProxy/ILibraryAppletCreator.cs
+++ b/Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/SystemAppletProxy/ILibraryAppletCreator.cs
@@ -1,3 +1,4 @@
+using Ryujinx.HLE.HOS.Applets;
 using Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.LibraryAppletCreator;
 
 namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.SystemAppletProxy
@@ -10,7 +11,10 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.Sys
         // CreateLibraryApplet(u32, u32) -> object<nn::am::service::ILibraryAppletAccessor>
         public ResultCode CreateLibraryApplet(ServiceCtx context)
         {
-            MakeObject(context, new ILibraryAppletAccessor(context.Device.System));
+            AppletId appletId          = (AppletId)context.RequestData.ReadInt32();
+            int      libraryAppletMode = context.RequestData.ReadInt32();
+
+            MakeObject(context, new ILibraryAppletAccessor(appletId, context.Device.System));
 
             return ResultCode.Success;
         }
diff --git a/Ryujinx.HLE/HOS/Services/Am/AppletAE/AppletFifo.cs b/Ryujinx.HLE/HOS/Services/Am/AppletAE/AppletFifo.cs
new file mode 100644
index 00000000..2391ba5e
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Services/Am/AppletAE/AppletFifo.cs
@@ -0,0 +1,79 @@
+using System;
+using System.Collections;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+
+namespace Ryujinx.HLE.HOS.Services.Am.AppletAE
+{
+    internal class AppletFifo<T> : IEnumerable<T>
+    {
+        private ConcurrentQueue<T> _dataQueue;
+
+        public int Count => _dataQueue.Count;
+
+        public AppletFifo()
+        {
+            _dataQueue = new ConcurrentQueue<T>();
+        }
+
+        public void Push(T item)
+        {
+            _dataQueue.Enqueue(item);
+        }
+
+        public T Pop()
+        {
+            if (_dataQueue.TryDequeue(out T result))
+            {
+                return result;
+            }
+
+            throw new InvalidOperationException("FIFO empty.");
+        }
+
+        public bool TryPop(out T result)
+        {
+            return _dataQueue.TryDequeue(out result);
+        }
+
+        public T Peek()
+        {
+            if (_dataQueue.TryPeek(out T result))
+            {
+                return result;
+            }
+
+            throw new InvalidOperationException("FIFO empty.");
+        }
+
+        public bool TryPeek(out T result)
+        {
+            return _dataQueue.TryPeek(out result);
+        }
+
+        public void Clear()
+        {
+            _dataQueue.Clear();
+        }
+
+        public T[] ToArray()
+        {
+            return _dataQueue.ToArray();
+        }
+
+        public void CopyTo(T[] array, int arrayIndex)
+        {
+            _dataQueue.CopyTo(array, arrayIndex);
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            return _dataQueue.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return _dataQueue.GetEnumerator();
+        }
+    }
+}
diff --git a/Ryujinx.HLE/HOS/Services/Am/AppletAE/Types/AppletId.cs b/Ryujinx.HLE/HOS/Services/Am/AppletAE/Types/AppletId.cs
new file mode 100644
index 00000000..917f6865
--- /dev/null
+++ b/Ryujinx.HLE/HOS/Services/Am/AppletAE/Types/AppletId.cs
@@ -0,0 +1,27 @@
+namespace Ryujinx.HLE.HOS.Services.Am.AppletAE
+{
+    enum AppletId
+    {
+        Application          = 0x01,
+        OverlayDisplay       = 0x02,
+        QLaunch              = 0x03,
+        Starter              = 0x04,
+        Auth                 = 0x0A,
+        Cabinet              = 0x0B,
+        Controller           = 0x0C,
+        DataErase            = 0x0D,
+        Error                = 0x0E,
+        NetConnect           = 0x0F,
+        PlayerSelect         = 0x10,
+        SoftwareKeyboard     = 0x11,
+        MiiEdit              = 0x12,
+        LibAppletWeb         = 0x13,
+        LibAppletShop        = 0x14,
+        PhotoViewer          = 0x15,
+        Settings             = 0x16,
+        LibAppletOff         = 0x17,
+        LibAppletWhitelisted = 0x18,
+        LibAppletAuth        = 0x19,
+        MyPage               = 0x1A
+    }
+}