// 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.
 
using System;
using System.ComponentModel.Composition;
using System.Diagnostics.CodeAnalysis;
using System.Threading;
using Microsoft.CodeAnalysis.Editor;
using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Options;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.BraceCompletion;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Operations;
using Microsoft.VisualStudio.Utilities;
using static Microsoft.CodeAnalysis.BraceCompletion.AbstractBraceCompletionService;
 
namespace Microsoft.CodeAnalysis.AutomaticCompletion;
 
[Export(typeof(IBraceCompletionSessionProvider))]
[ContentType(ContentTypeNames.RoslynContentType)]
[BracePair(CurlyBrace.OpenCharacter, CurlyBrace.CloseCharacter)]
[BracePair(Bracket.OpenCharacter, Bracket.CloseCharacter)]
[BracePair(SingleQuote.OpenCharacter, SingleQuote.CloseCharacter)]
[BracePair(DoubleQuote.OpenCharacter, DoubleQuote.CloseCharacter)]
[BracePair(Parenthesis.OpenCharacter, Parenthesis.CloseCharacter)]
[BracePair(LessAndGreaterThan.OpenCharacter, LessAndGreaterThan.CloseCharacter)]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed partial class BraceCompletionSessionProvider(
    IThreadingContext threadingContext,
    ITextBufferUndoManagerProvider undoManager,
    IEditorOperationsFactoryService editorOperationsFactoryService,
    EditorOptionsService editorOptionsService) : IBraceCompletionSessionProvider
{
    private readonly IThreadingContext _threadingContext = threadingContext;
    private readonly ITextBufferUndoManagerProvider _undoManager = undoManager;
    private readonly IEditorOperationsFactoryService _editorOperationsFactoryService = editorOperationsFactoryService;
    private readonly EditorOptionsService _editorOptionsService = editorOptionsService;
 
    public bool TryCreateSession(
        ITextView textView, SnapshotPoint openingPoint, char openingBrace, char closingBrace,
        [NotNullWhen(true)] out IBraceCompletionSession? session)
    {
        _threadingContext.ThrowIfNotOnUIThread();
 
        var responsiveCompletion = textView.Options.GetOptionValue(DefaultOptions.ResponsiveCompletionOptionId);
        var cancellationToken = GetCancellationToken(responsiveCompletion);
        try
        {
            return TryCreateSessionWorker(out session);
        }
        catch (OperationCanceledException)
        {
            session = null;
            return false;
        }
 
        bool TryCreateSessionWorker([NotNullWhen(true)] out IBraceCompletionSession? session)
        {
            var textSnapshot = openingPoint.Snapshot;
            var document = textSnapshot.GetOpenDocumentInCurrentContextWithChanges();
            if (document != null)
            {
                var editorSessionFactory = document.GetLanguageService<IBraceCompletionServiceFactory>();
                if (editorSessionFactory != null)
                {
                    var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
                    var editorSession = editorSessionFactory.TryGetService(parsedDocument, openingPoint, openingBrace, cancellationToken);
                    if (editorSession != null)
                    {
                        var undoHistory = _undoManager.GetTextBufferUndoManager(textView.TextBuffer).TextBufferUndoHistory;
                        session = new BraceCompletionSession(
                            this, textView, openingPoint.Snapshot.TextBuffer,
                            openingPoint, openingBrace, closingBrace,
                            undoHistory, editorSession, responsiveCompletion);
                        return true;
                    }
                }
            }
 
            session = null;
            return false;
        }
    }
 
    private static CancellationToken GetCancellationToken(bool responsiveCompletion)
    {
        if (!responsiveCompletion)
            return CancellationToken.None;
 
        // Brace completion is cancellable if the user has the 'responsive completion' option enabled. 200 ms was
        // chosen as the default timeout with the editor as a good balance of having enough time for computation,
        // while canceling early enough to not be too disruptive.
        var cancellationTokenSource = new CancellationTokenSource();
        cancellationTokenSource.CancelAfter(200);
        return cancellationTokenSource.Token;
    }
}