// 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.Composition;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.LanguageServer;
using Microsoft.CodeAnalysis.LanguageServer.Handler;
using Roslyn.LanguageServer.Protocol;
using Microsoft.VisualStudio.LanguageServices.Xaml.Features.AutoInsert;
using Microsoft.CodeAnalysis;
 
namespace Microsoft.VisualStudio.LanguageServices.Xaml.LanguageServer.Handler;
 
[ExportStatelessXamlLspService(typeof(OnAutoInsertHandler)), Shared]
[Method(VSInternalMethods.OnAutoInsertName)]
internal sealed class OnAutoInsertHandler : ILspServiceRequestHandler<VSInternalDocumentOnAutoInsertParams, VSInternalDocumentOnAutoInsertResponseItem?>
{
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public OnAutoInsertHandler()
    {
    }
 
    public bool MutatesSolutionState => false;
    public bool RequiresLSPSolution => true;
 
    public TextDocumentIdentifier GetTextDocumentIdentifier(VSInternalDocumentOnAutoInsertParams request) => request.TextDocument;
 
    public async Task<VSInternalDocumentOnAutoInsertResponseItem?> HandleRequestAsync(VSInternalDocumentOnAutoInsertParams request, RequestContext context, CancellationToken cancellationToken)
    {
        var document = context.Document;
        if (document == null)
        {
            return null;
        }
 
        var insertService = document.Project.Services.GetService<IXamlAutoInsertService>();
        if (insertService == null)
        {
            return null;
        }
 
        var text = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
        var offset = text.Lines.GetPosition(ProtocolConversions.PositionToLinePosition(request.Position));
        var result = await insertService.GetAutoInsertAsync(document, request.Character[0], offset, cancellationToken).ConfigureAwait(false);
        if (result == null)
        {
            return null;
        }
 
        Contract.ThrowIfNull(result.TextChange.NewText);
        var insertText = result.TextChange.NewText;
        var insertFormat = InsertTextFormat.Plaintext;
        if (result.CaretOffset.HasValue)
        {
            insertFormat = InsertTextFormat.Snippet;
            insertText = insertText.Insert(result.CaretOffset.Value, "$0");
        }
 
        return new VSInternalDocumentOnAutoInsertResponseItem
        {
            TextEditFormat = insertFormat,
            TextEdit = new TextEdit
            {
                NewText = insertText,
                Range = ProtocolConversions.TextSpanToRange(result.TextChange.Span, text)
            }
        };
    }
}