// Copyright © 2013 The CefSharp Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.

using System;
using System.Windows.Input;

namespace CefSharp.Wpf
{
    /// <summary>
    /// DelegateCommand
    /// </summary>
    /// <seealso cref="System.Windows.Input.ICommand" />
    internal class DelegateCommand : ICommand
    {
        /// <summary>
        /// The command handler
        /// </summary>
        private readonly Action commandHandler;
        /// <summary>
        /// The can execute handler
        /// </summary>
        private readonly Func<bool> canExecuteHandler;

        /// <summary>
        /// Occurs when changes occur that affect whether or not the command should execute.
        /// </summary>
        public event EventHandler CanExecuteChanged;

        /// <summary>
        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
        /// </summary>
        /// <param name="commandHandler">The command handler.</param>
        /// <param name="canExecuteHandler">The can execute handler.</param>
        public DelegateCommand(Action commandHandler, Func<bool> canExecuteHandler = null)
        {
            this.commandHandler = commandHandler;
            this.canExecuteHandler = canExecuteHandler;
        }

        /// <summary>
        /// Defines the method to be called when the command is invoked.
        /// </summary>
        /// <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
        public void Execute(object parameter)
        {
            commandHandler();
        }

        /// <summary>
        /// Defines the method that determines whether the command can execute in its current state.
        /// </summary>
        /// <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
        /// <returns>true if this command can be executed; otherwise, false.</returns>
        public bool CanExecute(object parameter)
        {
            return
                canExecuteHandler == null ||
                canExecuteHandler();
        }

        /// <summary>
        /// Raises the can execute changed.
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            if (CanExecuteChanged != null)
            {
                CanExecuteChanged(this, EventArgs.Empty);
            }
        }
    }
}