CancellableCommand.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System.Collections.Generic;

using SiliconStudio.ActionStack;
using SiliconStudio.Presentation.ViewModel;

namespace SiliconStudio.Presentation.Commands
{
    /// <summary>
    /// A command that supports undo/redo
    /// </summary>
    public abstract class CancellableCommand : CommandBase
    {
        private readonly IActionStack actionStack;
        private readonly IEnumerable<IDirtiableViewModel> dirtiables;

        /// <summary>
        /// Initializes a new instance of the <see cref="CancellableCommand"/> class.
        /// </summary>
        /// <param name="serviceProvider">A service provider that can provide a <see cref="IActionStack"/> to use for this view model.</param>
        /// <param name="dirtiables">The <see cref="IDirtiableViewModel"/> instances associated to this command.</param>
        protected CancellableCommand(IViewModelServiceProvider serviceProvider, IEnumerable<IDirtiableViewModel> dirtiables)
            : base(serviceProvider)
        {
            actionStack = serviceProvider.Get<IActionStack>();
            this.dirtiables = dirtiables;
        }

        /// <summary>
        /// The name of this command.
        /// </summary>
        public abstract string Name { get; }
        
        /// <inheritdoc/>
        public override void Execute(object parameter)
        {
            ExecuteCommand(parameter, true);
        }

        /// <summary>
        /// Undoes the execution of this command.
        /// </summary>
        /// <param name="parameter">The parameter used to invoke the command.</param>
        /// <param name="token">The <see cref="UndoToken"/> generated by the execution of this command.</param>
        public void UndoCommand(object parameter, UndoToken token)
        {
            Undo(parameter, token);
        }

        /// <summary>
        /// Executes the command and return a token that can be used to undo it.
        /// </summary>
        /// <param name="parameter">The command parameter.</param>
        /// <param name="createActionItem">Indicates whether to create an action item in the action stack. This should be false in case of a Redo operation.</param>
        /// <returns>An <see cref="UndoToken"/> that can be used to undo the command.</returns>
        public UndoToken ExecuteCommand(object parameter, bool createActionItem)
        {
            // TODO: Improve this - we're discarding any change made directly by the command invoke and create a CommandActionItem after.
            var transactionalActionStack = actionStack as ITransactionalActionStack;
            if (transactionalActionStack != null)
                transactionalActionStack.BeginTransaction();

            UndoToken token = Redo(parameter, createActionItem);
            
            if (transactionalActionStack != null)
                transactionalActionStack.DiscardTransaction();
            
            if (token.CanUndo && createActionItem)
            {
                var actionItem = new CommandActionItem(this, parameter, token, dirtiables);
                actionStack.Add(actionItem);
            }
            return token;
        }

        /// <summary>
        /// Does or redoes the execution of the command.
        /// </summary>
        /// <param name="parameter">The command parameter.</param>
        /// <param name="creatingActionItem">Indicates whether an action item is being created for the action stack</param>
        /// <returns>An <see cref="UndoToken"/> that can be used to undo the command.</returns>
        protected abstract UndoToken Redo(object parameter, bool creatingActionItem);

        /// <summary>
        /// Undoes the execution of the command.
        /// </summary>
        /// <param name="parameter">The command parameter.</param>
        /// <param name="token">The <see cref="UndoToken"/> generated by the execution of this command.</param>
        protected abstract void Undo(object parameter, UndoToken token);
    }
}