// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Windows.Input;
 
namespace Microsoft.VisualStudio.LanguageServices.Utilities;
 
internal class DelegateCommand : ICommand
{
    public event EventHandler? CanExecuteChanged;
 
    private readonly Func<object, bool> _canExecute;
    private readonly Action<object> _action;
 
    private bool _lastCanExecute;
 
    public DelegateCommand(Action<object> action)
        : this(action, (_) => true)
    {
    }
 
    public DelegateCommand(Action<object> action, Func<object, bool> canExecute)
    {
        _canExecute = canExecute;
        _action = action;
    }
 
    public bool CanExecute(object parameter)
    {
        var canExecute = _canExecute(parameter);
        if (canExecute != _lastCanExecute)
        {
            _lastCanExecute = canExecute;
            CanExecuteChanged?.Invoke(this, new EventArgs());
        }
 
        return canExecute;
    }
 
    public void Execute(object parameter) => _action(parameter);
}