// 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.
 
#nullable disable
 
using System;
using System.Composition;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.Host.Mef;
 
namespace Microsoft.CodeAnalysis.Editor.Undo;
 
/// <summary>
/// This factory will create a service that provides workspace global undo service.
/// </summary>
[ExportWorkspaceServiceFactory(typeof(IGlobalUndoService), ServiceLayer.Default), Shared]
internal class NoOpGlobalUndoServiceFactory : IWorkspaceServiceFactory
{
    public static readonly IWorkspaceGlobalUndoTransaction Transaction = new NoOpUndoTransaction();
 
    private readonly NoOpGlobalUndoService _singleton = new();
 
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public NoOpGlobalUndoServiceFactory()
    {
    }
 
    public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
        => _singleton;
 
    private class NoOpGlobalUndoService : IGlobalUndoService
    {
        public bool IsGlobalTransactionOpen(Workspace workspace)
        {
            // TODO: this is technically wrong -- Transaction shouldn't be a singleton.
            return false;
        }
 
        public bool CanUndo(Workspace workspace)
        {
            // by default, undo is not supported
            return false;
        }
 
        public IWorkspaceGlobalUndoTransaction OpenGlobalUndoTransaction(Workspace workspace, string description)
            => Transaction;
    }
 
    /// <summary>
    /// null object that doesn't do anything
    /// </summary>
    private class NoOpUndoTransaction : IWorkspaceGlobalUndoTransaction
    {
        public void Commit()
        {
        }
 
        public void Dispose()
        {
        }
 
        public void AddDocument(DocumentId id)
        {
        }
    }
}