Connected.Components/Services/KeyInterceptor/KeyInterceptor.cs

// Copyright (c) MudBlazor 2021
// MudBlazor licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Diagnostics.CodeAnalysis;
using Microsoft.AspNetCore.Components.Web;
using Microsoft.JSInterop;

namespace Connected.Services;

/// <summary>
/// This transient service binds itself to a parent element to observe the keys of one of its children.
/// It can call preventDefault or stopPropagation directly on the JavaScript side for single key strokes / key combinations as per configuration.
/// Furthermore, you can precisely subscribe single keystrokes or combinations and only the subscribed ones will be forwarded into .NET
/// </summary>
public class KeyInterceptor : IKeyInterceptor, IDisposable
{
   private bool _isDisposed = false;

   private readonly DotNetObjectReference<KeyInterceptor> _dotNetRef;
   private readonly IJSRuntime _jsRuntime;
   private bool _isObserving;
   private string _elementId;

   [DynamicDependency(nameof(OnKeyDown))]
   [DynamicDependency(nameof(OnKeyUp))]
   [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(KeyboardEvent))]
   [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(KeyboardEventArgs))]
   [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(KeyOptions))]
   [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(KeyInterceptorOptions))]
   public KeyInterceptor(IJSRuntime jsRuntime)
   {
      _dotNetRef = DotNetObjectReference.Create(this);
      _jsRuntime = jsRuntime;
   }

   /// <summary>
   /// Connect to the ancestor element of the element(s) that should be observed
   /// </summary>
   /// <param name="elementId">Ancestor html element id</param>
   /// <param name="options">Define here the descendant(s) by setting TargetClass and the keystrokes to be monitored / suppressed</param>
   public async Task Connect(string elementId, KeyInterceptorOptions options)
   {
      if (_isObserving || _isDisposed)
         return;
      _elementId = elementId;
      _isObserving = await _jsRuntime.InvokeVoidAsyncWithErrorHandling("mudKeyInterceptor.connect", _dotNetRef, elementId, options);
   }

   /// <summary>
   /// Update behavior of a registered keyoption
   /// The keystrike to update has to be monitored previously
   /// </summary>
   /// <param name="option">Define KeyOption to update</param>
   public async Task UpdateKey(KeyOptions option)
   {
      await _jsRuntime.InvokeVoidAsync($"mudKeyInterceptor.updatekey", _elementId, option);
   }

   /// <summary>
   /// Disconnect from the previously connected ancestor and its descendants
   /// </summary>
   public async Task Disconnect()
   {
      try
      {
         await _jsRuntime.InvokeVoidAsync($"mudKeyInterceptor.disconnect", _elementId);
      }
      catch (Exception) {  /*ignore*/ }
      _isObserving = false;
   }

   [JSInvokable]
   public void OnKeyDown(KeyboardEventArgs args)
   {
      KeyDown?.Invoke(args);
   }

   [JSInvokable]
   public void OnKeyUp(KeyboardEventArgs args)
   {
      KeyUp?.Invoke(args);
   }

   public event KeyboardEvent KeyDown;
   public event KeyboardEvent KeyUp;

   protected virtual void Dispose(bool disposing)
   {
      if (!disposing || _isDisposed)
         return;
      _isDisposed = true;
      KeyDown = null;
      KeyUp = null;
      Disconnect().AndForget();
      _dotNetRef.Dispose();
   }

   public void Dispose()
   {
      Dispose(true);
      GC.SuppressFinalize(this);
   }

}