Implement worker AddItem commands

src/MxGateway.Worker/MxAccess/IMxAccessServer.cs

@@ -5,4 +5,17 @@ public interface IMxAccessServer
     int Register(string clientName);
 
     void Unregister(int serverHandle);
+
+    int AddItem(
+        int serverHandle,
+        string itemDefinition);
+
+    int AddItem2(
+        int serverHandle,
+        string itemDefinition,
+        string itemContext);
+
+    void RemoveItem(
+        int serverHandle,
+        int itemHandle);
 }

src/MxGateway.Worker/MxAccess/MxAccessComServer.cs

@@ -35,6 +35,44 @@ public sealed class MxAccessComServer : IMxAccessServer
         Invoke(nameof(Unregister), serverHandle);
     }
 
+    public int AddItem(
+        int serverHandle,
+        string itemDefinition)
+    {
+        if (mxAccessComObject is ILMXProxyServer mxAccessServer)
+        {
+            return mxAccessServer.AddItem(serverHandle, itemDefinition);
+        }
+
+        return (int)Invoke(nameof(AddItem), serverHandle, itemDefinition);
+    }
+
+    public int AddItem2(
+        int serverHandle,
+        string itemDefinition,
+        string itemContext)
+    {
+        if (mxAccessComObject is ILMXProxyServer3 mxAccessServer)
+        {
+            return mxAccessServer.AddItem2(serverHandle, itemDefinition, itemContext);
+        }
+
+        return (int)Invoke(nameof(AddItem2), serverHandle, itemDefinition, itemContext);
+    }
+
+    public void RemoveItem(
+        int serverHandle,
+        int itemHandle)
+    {
+        if (mxAccessComObject is ILMXProxyServer mxAccessServer)
+        {
+            mxAccessServer.RemoveItem(serverHandle, itemHandle);
+            return;
+        }
+
+        Invoke(nameof(RemoveItem), serverHandle, itemHandle);
+    }
+
     private object Invoke(
         string methodName,
         params object[] arguments)

src/MxGateway.Worker/MxAccess/MxAccessCommandExecutor.cs

@@ -34,6 +34,9 @@ public sealed class MxAccessCommandExecutor : IStaCommandExecutor
         {
             MxCommandKind.Register => ExecuteRegister(command),
             MxCommandKind.Unregister => ExecuteUnregister(command),
+            MxCommandKind.AddItem => ExecuteAddItem(command),
+            MxCommandKind.AddItem2 => ExecuteAddItem2(command),
+            MxCommandKind.RemoveItem => ExecuteRemoveItem(command),
             _ => CreateInvalidRequestReply(command, $"Unsupported MXAccess command kind {command.Kind}."),
         };
     }
@@ -67,6 +70,66 @@ public sealed class MxAccessCommandExecutor : IStaCommandExecutor
         return CreateOkReply(command);
     }
 
+    private MxCommandReply ExecuteAddItem(StaCommand command)
+    {
+        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AddItem)
+        {
+            return CreateInvalidRequestReply(command, "AddItem command payload is required.");
+        }
+
+        AddItemCommand addItemCommand = command.Command.AddItem;
+        int itemHandle = session.AddItem(
+            addItemCommand.ServerHandle,
+            addItemCommand.ItemDefinition);
+
+        MxCommandReply reply = CreateOkReply(command);
+        reply.ReturnValue = variantConverter.Convert(itemHandle);
+        reply.AddItem = new AddItemReply
+        {
+            ItemHandle = itemHandle,
+        };
+
+        return reply;
+    }
+
+    private MxCommandReply ExecuteAddItem2(StaCommand command)
+    {
+        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AddItem2)
+        {
+            return CreateInvalidRequestReply(command, "AddItem2 command payload is required.");
+        }
+
+        AddItem2Command addItem2Command = command.Command.AddItem2;
+        int itemHandle = session.AddItem2(
+            addItem2Command.ServerHandle,
+            addItem2Command.ItemDefinition,
+            addItem2Command.ItemContext);
+
+        MxCommandReply reply = CreateOkReply(command);
+        reply.ReturnValue = variantConverter.Convert(itemHandle);
+        reply.AddItem2 = new AddItem2Reply
+        {
+            ItemHandle = itemHandle,
+        };
+
+        return reply;
+    }
+
+    private MxCommandReply ExecuteRemoveItem(StaCommand command)
+    {
+        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.RemoveItem)
+        {
+            return CreateInvalidRequestReply(command, "RemoveItem command payload is required.");
+        }
+
+        RemoveItemCommand removeItemCommand = command.Command.RemoveItem;
+        session.RemoveItem(
+            removeItemCommand.ServerHandle,
+            removeItemCommand.ItemHandle);
+
+        return CreateOkReply(command);
+    }
+
     private static MxCommandReply CreateOkReply(StaCommand command)
     {
         return new MxCommandReply

src/MxGateway.Worker/MxAccess/MxAccessHandleRegistry.cs

@@ -6,12 +6,19 @@ namespace MxGateway.Worker.MxAccess;
 public sealed class MxAccessHandleRegistry
 {
     private readonly Dictionary<int, RegisteredServerHandle> serverHandles = new();
+    private readonly Dictionary<long, RegisteredItemHandle> itemHandles = new();
 
     public IReadOnlyList<RegisteredServerHandle> ServerHandles => serverHandles
         .Values
         .OrderBy(handle => handle.ServerHandle)
         .ToArray();
 
+    public IReadOnlyList<RegisteredItemHandle> ItemHandles => itemHandles
+        .Values
+        .OrderBy(handle => handle.ServerHandle)
+        .ThenBy(handle => handle.ItemHandle)
+        .ToArray();
+
     public void RegisterServerHandle(
         int serverHandle,
         string clientName)
@@ -22,10 +29,54 @@ public sealed class MxAccessHandleRegistry
     public void UnregisterServerHandle(int serverHandle)
     {
         serverHandles.Remove(serverHandle);
+
+        foreach (long key in itemHandles
+            .Where(pair => pair.Value.ServerHandle == serverHandle)
+            .Select(pair => pair.Key)
+            .ToArray())
+        {
+            itemHandles.Remove(key);
+        }
     }
 
     public bool ContainsServerHandle(int serverHandle)
     {
         return serverHandles.ContainsKey(serverHandle);
     }
+
+    public void RegisterItemHandle(
+        int serverHandle,
+        int itemHandle,
+        string itemDefinition,
+        string itemContext,
+        bool hasItemContext)
+    {
+        itemHandles[CreateItemKey(serverHandle, itemHandle)] = new RegisteredItemHandle(
+            serverHandle,
+            itemHandle,
+            itemDefinition,
+            itemContext,
+            hasItemContext);
+    }
+
+    public void RemoveItemHandle(
+        int serverHandle,
+        int itemHandle)
+    {
+        itemHandles.Remove(CreateItemKey(serverHandle, itemHandle));
+    }
+
+    public bool ContainsItemHandle(
+        int serverHandle,
+        int itemHandle)
+    {
+        return itemHandles.ContainsKey(CreateItemKey(serverHandle, itemHandle));
+    }
+
+    private static long CreateItemKey(
+        int serverHandle,
+        int itemHandle)
+    {
+        return ((long)serverHandle << 32) | (uint)itemHandle;
+    }
 }

src/MxGateway.Worker/MxAccess/MxAccessSession.cs

@@ -106,6 +106,51 @@ public sealed class MxAccessSession : IDisposable
         handleRegistry.UnregisterServerHandle(serverHandle);
     }
 
+    public int AddItem(
+        int serverHandle,
+        string itemDefinition)
+    {
+        ThrowIfDisposed();
+
+        int itemHandle = mxAccessServer.AddItem(serverHandle, itemDefinition);
+        handleRegistry.RegisterItemHandle(
+            serverHandle,
+            itemHandle,
+            itemDefinition,
+            string.Empty,
+            hasItemContext: false);
+
+        return itemHandle;
+    }
+
+    public int AddItem2(
+        int serverHandle,
+        string itemDefinition,
+        string itemContext)
+    {
+        ThrowIfDisposed();
+
+        int itemHandle = mxAccessServer.AddItem2(serverHandle, itemDefinition, itemContext);
+        handleRegistry.RegisterItemHandle(
+            serverHandle,
+            itemHandle,
+            itemDefinition,
+            itemContext,
+            hasItemContext: true);
+
+        return itemHandle;
+    }
+
+    public void RemoveItem(
+        int serverHandle,
+        int itemHandle)
+    {
+        ThrowIfDisposed();
+
+        mxAccessServer.RemoveItem(serverHandle, itemHandle);
+        handleRegistry.RemoveItemHandle(serverHandle, itemHandle);
+    }
+
     public void Dispose()
     {
         if (disposed)

src/MxGateway.Worker/MxAccess/MxAccessStaSession.cs

@@ -81,6 +81,19 @@ public sealed class MxAccessStaSession : IDisposable
             cancellationToken);
     }
 
+    public Task<IReadOnlyList<RegisteredItemHandle>> GetRegisteredItemHandlesAsync(
+        CancellationToken cancellationToken = default)
+    {
+        if (session is null)
+        {
+            throw new InvalidOperationException("MXAccess COM session has not been started.");
+        }
+
+        return staRuntime.InvokeAsync(
+            () => session.HandleRegistry.ItemHandles,
+            cancellationToken);
+    }
+
     public void Dispose()
     {
         if (disposed)

src/MxGateway.Worker/MxAccess/RegisteredItemHandle.cs

@@ -0,0 +1,28 @@
+namespace MxGateway.Worker.MxAccess;
+
+public sealed class RegisteredItemHandle
+{
+    public RegisteredItemHandle(
+        int serverHandle,
+        int itemHandle,
+        string itemDefinition,
+        string itemContext,
+        bool hasItemContext)
+    {
+        ServerHandle = serverHandle;
+        ItemHandle = itemHandle;
+        ItemDefinition = itemDefinition;
+        ItemContext = itemContext;
+        HasItemContext = hasItemContext;
+    }
+
+    public int ServerHandle { get; }
+
+    public int ItemHandle { get; }
+
+    public string ItemDefinition { get; }
+
+    public string ItemContext { get; }
+
+    public bool HasItemContext { get; }
+}