MultiTerm/MultiTerm.Protocols/ProtocolSettingsViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using CommunityToolkit.Mvvm.Messaging;
using MultiTerm.Protocols.Types;

namespace MultiTerm.Protocols;

/// <summary>
/// Class that represents all connection and usage settings for a specific <see cref="CommunicationProtocol"/>.
/// Can be bound to UI using MVVM pattern.
/// Implementing class must also implement <see cref="IProtocolSettings"/>! Otherwise <see cref="ConnectDisconnectCommand"/> does not work.
/// </summary>
public abstract partial class ProtocolSettingsViewModel : ObservableObject, IProtocolSettingsViewModel
{
    private const string connectedStateButtonText = "Disconnect";
    private const string disconnectedStateButtonText = "Connect";
    protected readonly IMessenger messenger;

    public event EventHandler<ConnectionRequestEventArgs>? ConnectRequested;
    public event EventHandler? DisconnectRequested;

    public abstract ProtocolType ProtocolType { get; }

    [ObservableProperty]
    private string connectDisconnectButtonText = disconnectedStateButtonText;

    [ObservableProperty]
    private bool areEditable = true;  // initially editable

    
    public ProtocolSettingsViewModel(IMessenger messenger)
    {
        this.messenger = messenger;
    }

    /// <summary>
    /// Binding to Connect/Disconnect button.
    /// Button text is provided in <see cref="ConnectDisconnectButtonText"/>
    /// Implementing class must also implement <see cref="IProtocolSettings"/>! Otherwise <see cref="ConnectDisconnectCommand"/> does not work.
    /// </summary>
    [RelayCommand(AllowConcurrentExecutions = false)]
    private async Task ConnectDisconnectAsync()
    {
        await Task.Factory.StartNew(() =>
        {
            // if currently disconnected
            if (this.ConnectDisconnectButtonText == disconnectedStateButtonText)
            {
                // CONNECT
                this.AreEditable = false;

                // create event args. Important: derivative classes must also implement IProtocolSettings!
                var eventArgs = new ConnectionRequestEventArgs((IProtocolSettings)this);
                // fire event
                this.ConnectRequested?.Invoke(this, eventArgs);

                // after invoke: connection was made successfully?
                if (eventArgs.Success)
                {
                    // set button to connected state
                    this.ConnectDisconnectButtonText = connectedStateButtonText;
                }
                else
                {
                    // rollback
                    this.AreEditable = true;
                }
            }
            // if currently connected
            else if (this.ConnectDisconnectButtonText == connectedStateButtonText)
            {
                // DISCONNECT
                this.DisconnectRequested?.Invoke(this, EventArgs.Empty);
                this.ConnectDisconnectButtonText = disconnectedStateButtonText;
                this.AreEditable = true;
            }
            else
            {
                throw new Exception($"'{nameof(ConnectDisconnectAsync)}()' has not recognized button text, cannot identify state of connection.");
            }
        });
    }
}