// 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;
using Microsoft.CodeAnalysis.Editor;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Text;
using Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem;
using Microsoft.VisualStudio.LanguageServices.Implementation.Venus;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Operations;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation
{
    using Workspace = Microsoft.CodeAnalysis.Workspace;
 
    [ExportWorkspaceServiceFactory(typeof(ITextUndoHistoryWorkspaceService), ServiceLayer.Host), Shared]
    internal class VisualStudioTextUndoHistoryWorkspaceServiceFactory : IWorkspaceServiceFactory
    {
        private readonly ITextUndoHistoryWorkspaceService _serviceSingleton;
 
        [ImportingConstructor]
        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
        public VisualStudioTextUndoHistoryWorkspaceServiceFactory(ITextUndoHistoryRegistry undoHistoryRegistry)
            => _serviceSingleton = new TextUndoHistoryWorkspaceService(undoHistoryRegistry);
 
        public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
            => _serviceSingleton;
 
        private class TextUndoHistoryWorkspaceService : ITextUndoHistoryWorkspaceService
        {
            private readonly ITextUndoHistoryRegistry _undoHistoryRegistry;
 
            public TextUndoHistoryWorkspaceService(ITextUndoHistoryRegistry undoHistoryRegistry)
                => _undoHistoryRegistry = undoHistoryRegistry;
 
            public bool TryGetTextUndoHistory(Workspace editorWorkspace, ITextBuffer textBuffer, out ITextUndoHistory undoHistory)
            {
                switch (editorWorkspace)
                {
                    case VisualStudioWorkspaceImpl:
 
                        // TODO: Handle undo if context changes
                        var documentId = editorWorkspace.GetDocumentIdInCurrentContext(textBuffer.AsTextContainer());
                        if (documentId == null)
                        {
                            undoHistory = null;
                            return false;
                        }
 
                        // In the Visual Studio case, there might be projection buffers involved for Venus,
                        // where we associate undo history with the surface buffer and not the subject buffer.
                        var containedDocument = ContainedDocument.TryGetContainedDocument(documentId);
 
                        if (containedDocument != null)
                        {
                            textBuffer = containedDocument.DataBuffer;
                        }
 
                        break;
 
                    case MiscellaneousFilesWorkspace _:
 
                        // Nothing to do in this case: textBuffer is correct!
 
                        break;
 
                    default:
 
                        undoHistory = null;
                        return false;
 
                }
 
                return _undoHistoryRegistry.TryGetHistory(textBuffer, out undoHistory);
            }
        }
    }
}