Command refactor

src/AppCommon/FileTime.App.Core/Services/UserCommandHandler/UserCommandHandlerServiceBase.cs

@@ -0,0 +1,60 @@
+using System.Reactive.Linq;
+using DynamicData;
+using FileTime.App.Core.ViewModels;
+using FileTime.Core.Models;
+
+namespace FileTime.App.Core.Services.UserCommandHandler;
+
+public abstract class UserCommandHandlerServiceBase : IUserCommandHandler
+{
+    private readonly List<IUserCommandHandler> _userCommandHandlers = new();
+    private readonly IAppState? _appState;
+
+    protected UserCommandHandlerServiceBase(IAppState? appState = null)
+    {
+        _appState = appState;
+    }
+
+    public bool CanHandleCommand(UserCommand.IUserCommand command) => _userCommandHandlers.Any(h => h.CanHandleCommand(command));
+
+    public async Task HandleCommandAsync(UserCommand.IUserCommand command)
+    {
+        var handler = _userCommandHandlers.Find(h => h.CanHandleCommand(command));
+
+        if (handler is null) return;
+        await handler.HandleCommandAsync(command);
+    }
+
+    protected void AddCommandHandler(IUserCommandHandler userCommandHandler) => _userCommandHandlers.Add(userCommandHandler);
+
+    protected void AddCommandHandlers(IEnumerable<IUserCommandHandler> commandHandlers)
+    {
+        foreach (var userCommandHandler in commandHandlers)
+        {
+            AddCommandHandler(userCommandHandler);
+        }
+    }
+
+    protected void RemoveCommandHandler(IUserCommandHandler userCommandHandler) => _userCommandHandlers.Remove(userCommandHandler);
+
+    protected IDisposable SaveSelectedTab(Action<ITabViewModel?> handler) => RunWithAppState(appState => appState.SelectedTab.Subscribe(handler));
+
+    protected IDisposable SaveCurrentSelectedItem(Action<IItemViewModel?> handler)
+        => RunWithAppState(appState => appState.SelectedTab.Select(t => t == null ? Observable.Return<IItemViewModel?>(null) : t.CurrentSelectedItem).Switch().Subscribe(handler));
+
+    protected IDisposable SaveCurrentLocation(Action<IContainer?> handler)
+        => RunWithAppState(appState => appState.SelectedTab.Select(t => t == null ? Observable.Return<IContainer?>(null) : t.CurrentLocation).Switch().Subscribe(handler));
+
+    protected IDisposable SaveCurrentItems(Action<IEnumerable<IItemViewModel>> handler)
+        => RunWithAppState(appState => appState.SelectedTab.Select(t => t?.CurrentItemsCollectionObservable ?? Observable.Return((IEnumerable<IItemViewModel>?) Enumerable.Empty<IItemViewModel>())).Switch().Subscribe(i => handler(i ?? Enumerable.Empty<IItemViewModel>())));
+
+    protected IDisposable SaveMarkedItems(Action<IChangeSet<IAbsolutePath>> handler)
+        => RunWithAppState(appState => appState.SelectedTab.Select(t => t == null ? Observable.Empty<IChangeSet<IAbsolutePath>>() : t.MarkedItems).Switch().Subscribe(handler));
+
+    private IDisposable RunWithAppState(Func<IAppState, IDisposable> act)
+    {
+        if (_appState == null) throw new NullReferenceException($"AppState is nit initialized in {nameof(UserCommandHandlerServiceBase)}.");
+
+        return act(_appState);
+    }
+}