// 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.Threading;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using Microsoft.CodeAnalysis.Text.Shared.Extensions;
using Microsoft.VisualStudio.LanguageServices.Implementation.Extensions;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Utilities;
using IVsLanguageBlock = Microsoft.VisualStudio.TextManager.Interop.IVsLanguageBlock;
using IVsTextLines = Microsoft.VisualStudio.TextManager.Interop.IVsTextLines;
using VsTextSpan = Microsoft.VisualStudio.TextManager.Interop.TextSpan;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.LanguageService;
 
internal abstract partial class AbstractLanguageService<TPackage, TLanguageService>
    : IVsLanguageBlock
{
    public int GetCurrentBlock(
        IVsTextLines pTextLines,
        int iCurrentLine,
        int iCurrentChar,
        VsTextSpan[] ptsBlockSpan,
        out string pbstrDescription,
        out int pfBlockAvailable)
    {
        var snapshot = this.EditorAdaptersFactoryService.GetDataBuffer(pTextLines).CurrentSnapshot;
        var position = snapshot?.TryGetPosition(iCurrentLine, iCurrentChar);
        if (position == null)
        {
            pbstrDescription = null;
            pfBlockAvailable = 0;
            return VSConstants.S_OK;
        }
 
        (string description, TextSpan span)? foundBlock = null;
 
        var uiThreadOperationExecutor = this.Package.ComponentModel.GetService<IUIThreadOperationExecutor>();
        uiThreadOperationExecutor.Execute(
            ServicesVSResources.Current_block,
            ServicesVSResources.Determining_current_block,
            allowCancellation: true,
            showProgress: false,
            action: context =>
            {
                foundBlock = VsLanguageBlock.GetCurrentBlock(snapshot, position.Value, context.UserCancellationToken);
            });
 
        pfBlockAvailable = foundBlock != null ? 1 : 0;
        pbstrDescription = foundBlock?.description;
 
        if (foundBlock != null && ptsBlockSpan != null && ptsBlockSpan.Length >= 1)
        {
            ptsBlockSpan[0] = foundBlock.Value.span.ToSnapshotSpan(snapshot).ToVsTextSpan();
        }
 
        return VSConstants.S_OK;
    }
}
 
internal static class VsLanguageBlock
{
    public static (string description, TextSpan span)? GetCurrentBlock(
        ITextSnapshot snapshot,
        int position,
        CancellationToken cancellationToken)
    {
        var document = snapshot.GetOpenDocumentInCurrentContextWithChanges();
        if (document == null || !document.SupportsSyntaxTree)
        {
            return null;
        }
 
        var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
        var syntaxRoot = document.GetSyntaxRootSynchronously(cancellationToken);
        var node = syntaxFactsService.GetContainingMemberDeclaration(syntaxRoot, position, useFullSpan: false);
        if (node == null)
        {
            return null;
        }
 
        var description = syntaxFactsService.GetDisplayName(node,
            DisplayNameOptions.IncludeMemberKeyword |
            DisplayNameOptions.IncludeParameters |
            DisplayNameOptions.IncludeType |
            DisplayNameOptions.IncludeTypeParameters);
 
        return (description, node.Span);
    }
}