// --------------------------------------------------------------------------------------------------------------------
// <copyright file="DelegateCommand.cs" company="OxyPlot">
//   Copyright (c) 2014 OxyPlot contributors
// </copyright>
// <summary>
//   Represents a delegate command.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

namespace WpfExamples
{
    using System;
    using System.Windows.Input;

    /// <summary>
    /// Represents a delegate command.
    /// </summary>
    public class DelegateCommand : ICommand
    {
        /// <summary>
        /// The can execute.
        /// </summary>
        private readonly Func<bool> canExecute;

        /// <summary>
        /// The execute.
        /// </summary>
        private readonly Action execute;

        /// <summary>
        /// Initializes a new instance of the <see cref="DelegateCommand" /> class.
        /// </summary>
        /// <param name="execute">The execute.</param>
        public DelegateCommand(Action execute)
            : this(execute, null)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="DelegateCommand" /> class.
        /// </summary>
        /// <param name="execute">The execute.</param>
        /// <param name="canExecute">The can execute.</param>
        public DelegateCommand(Action execute, Func<bool> canExecute)
        {
            if (execute == null)
            {
                throw new ArgumentNullException("execute");
            }

            this.execute = execute;
            this.canExecute = canExecute;
        }

        /// <summary>
        /// Occurs when changes occur that affect whether or not the command should execute.
        /// </summary>
        public event EventHandler CanExecuteChanged
        {
            add
            {
                if (this.canExecute != null)
                {
                    CommandManager.RequerySuggested += value;
                }
            }

            remove
            {
                if (this.canExecute != null)
                {
                    CommandManager.RequerySuggested -= value;
                }
            }
        }

        /// <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 <c>null</c>.</param>
        /// <returns><c>true</c> if this command can be executed; otherwise, <c>false</c>.</returns>
        public bool CanExecute(object parameter)
        {
            return this.canExecute == null ? true : this.canExecute();
        }

        /// <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 <c>null</c>.</param>
        public void Execute(object parameter)
        {
            this.execute();
        }

        /// <summary>
        /// Raises the can execute changed.
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            CommandManager.InvalidateRequerySuggested();
        }
    }
}