using System;

using System.Windows.Input;

using System.Diagnostics;

namespace NumediaStack

{

/// <summary>

/// Simple implementation of the DelegateCommand (aka RelayCommand) pattern.

/// </summary>

internal class DelegateCommand : ICommand

{

/// <summary>

/// Stores a reference to the CanExecute Func.

/// </summary>

private readonly Func<object, bool> _canExecute;

/// <summary>

/// Stores a reference to the Execute Action.

/// </summary>

private readonly Action<object> _execute;

/// <summary>

/// Initializes a new instance of the DelegateCommand class.

/// </summary>

/// <param name="execute">Action to invoke when Execute is called.</param>

public DelegateCommand(Action<object> execute)

: this(param => true, execute)

{

}

/// <summary>

/// Initializes a new instance of the DelegateCommand class.

/// </summary>

/// <param name="canExecute">Func to invoke when CanExecute is called.</param>

/// <param name="execute">Action to invoke when Execute is called.</param>

public DelegateCommand(Func<object, bool> canExecute, Action<object> execute)

{

Debug.Assert(canExecute != null, "canExecute must not be null.");

Debug.Assert(execute != null, "execute must not be null.");

_canExecute = canExecute;

_execute = execute;

}

/// <summary>

/// Determines if the command can execute.

/// </summary>

/// <param name="parameter">Data used by the command.</param>

/// <returns>True if the command can execute.</returns>

public bool CanExecute(object parameter)

{

return _canExecute(parameter);

}

/// <summary>

/// Executes the command.

/// </summary>

/// <param name="parameter">Data used by the command.</param>

public void Execute(object parameter)

{

_execute(parameter);

}

/// <summary>

/// Invoked when changes to the execution state of the command occur.

/// </summary>

public event EventHandler CanExecuteChanged;

/// <summary>

/// Invokes the CanExecuteChanged event.

/// </summary>

public void OnCanExecuteChanged()

{

EventHandler handler = CanExecuteChanged;

if (null != handler)

{

handler(this, EventArgs.Empty);

}

}

}

}