am: Implement common web applets (#1188)

* am: Implemnet common web applets

This implement parsing of input and output of web applets while making
those close directly.

TODO for the future: Use and hook a web browser.

* Address Ac_K's comments

Ryujinx.HLE/HOS/Applets/Browser/BrowserApplet.cs

@@ -0,0 +1,105 @@
+using Ryujinx.Common;
+using Ryujinx.Common.Logging;
+using Ryujinx.HLE.HOS.Services.Am.AppletAE;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.HLE.HOS.Applets.Browser
+{
+    internal class BrowserApplet : IApplet
+    {
+        public event EventHandler AppletStateChanged;
+
+        private AppletSession _normalSession;
+        private AppletSession _interactiveSession;
+
+        private CommonArguments _commonArguments;
+        private List<BrowserArgument> _arguments;
+        private ShimKind _shimKind;
+
+        public BrowserApplet(Horizon system) {}
+
+        public ResultCode GetResult()
+        {
+            return ResultCode.Success;
+        }
+
+        public ResultCode Start(AppletSession normalSession, AppletSession interactiveSession)
+        {
+            _normalSession = normalSession;
+            _interactiveSession = interactiveSession;
+
+            _commonArguments = IApplet.ReadStruct<CommonArguments>(_normalSession.Pop());
+
+            Logger.PrintStub(LogClass.ServiceAm, $"WebApplet version: 0x{_commonArguments.AppletVersion:x8}");
+
+            ReadOnlySpan<byte> webArguments = _normalSession.Pop();
+
+            (_shimKind, _arguments) = BrowserArgument.ParseArguments(webArguments);
+
+            Logger.PrintStub(LogClass.ServiceAm, $"Web Arguments: {_arguments.Count}");
+
+            foreach (BrowserArgument argument in _arguments)
+            {
+                Logger.PrintStub(LogClass.ServiceAm, $"{argument.Type}: {argument.GetValue()}");
+            }
+
+            if ((_commonArguments.AppletVersion >= 0x80000 && _shimKind == ShimKind.Web) || (_commonArguments.AppletVersion >= 0x30000 && _shimKind == ShimKind.Share))
+            {
+                List<BrowserOutput> result = new List<BrowserOutput>();
+
+                result.Add(new BrowserOutput(BrowserOutputType.ExitReason, (uint)WebExitReason.ExitButton));
+
+                _normalSession.Push(BuildResponseNew(result));
+            }
+            else
+            {
+                WebCommonReturnValue result = new WebCommonReturnValue()
+                {
+                    ExitReason  = WebExitReason.ExitButton,
+                };
+
+                _normalSession.Push(BuildResponseOld(result));
+            }
+
+            AppletStateChanged?.Invoke(this, null);
+
+            return ResultCode.Success;
+        }
+
+        private byte[] BuildResponseOld(WebCommonReturnValue result)
+        {
+            using (MemoryStream stream = new MemoryStream())
+            using (BinaryWriter writer = new BinaryWriter(stream))
+            {
+                writer.WriteStruct(result);
+
+                return stream.ToArray();
+            }
+        }
+        private byte[] BuildResponseNew(List<BrowserOutput> outputArguments)
+        {
+            using (MemoryStream stream = new MemoryStream())
+            using (BinaryWriter writer = new BinaryWriter(stream))
+            {
+                writer.WriteStruct(new WebArgHeader
+                {
+                    Count    = (ushort)outputArguments.Count,
+                    ShimKind = _shimKind
+                });
+
+                foreach (BrowserOutput output in outputArguments)
+                {
+                    output.Write(writer);
+                }
+
+                writer.Write(new byte[0x2000 - writer.BaseStream.Position]);
+
+                return stream.ToArray();
+            }
+        }
+    }
+}