// 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.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Editor.Peek;
using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.CodeAnalysis.Navigation;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.SymbolMapping;
using Microsoft.CodeAnalysis.Text;
using Microsoft.VisualStudio.Language.Intellisense;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Utilities;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Editor.Implementation.Peek;
 
internal sealed class PeekableItemSource : IPeekableItemSource
{
    private readonly ITextBuffer _textBuffer;
    private readonly IPeekableItemFactory _peekableItemFactory;
    private readonly IPeekResultFactory _peekResultFactory;
    private readonly IThreadingContext _threadingContext;
    private readonly IUIThreadOperationExecutor _uiThreadOperationExecutor;
 
    public PeekableItemSource(
        ITextBuffer textBuffer,
        IPeekableItemFactory peekableItemFactory,
        IPeekResultFactory peekResultFactory,
        IThreadingContext threadingContext,
        IUIThreadOperationExecutor uiThreadOperationExecutor)
    {
        _textBuffer = textBuffer;
        _peekableItemFactory = peekableItemFactory;
        _peekResultFactory = peekResultFactory;
        _threadingContext = threadingContext;
        _uiThreadOperationExecutor = uiThreadOperationExecutor;
    }
 
    public void AugmentPeekSession(IPeekSession session, IList<IPeekableItem> peekableItems)
    {
        if (!string.Equals(session.RelationshipName, PredefinedPeekRelationships.Definitions.Name, StringComparison.OrdinalIgnoreCase))
        {
            return;
        }
 
        var triggerPoint = session.GetTriggerPoint(_textBuffer.CurrentSnapshot);
        if (!triggerPoint.HasValue)
        {
            return;
        }
 
        var document = triggerPoint.Value.Snapshot.GetOpenDocumentInCurrentContextWithChanges();
        if (document == null)
        {
            return;
        }
 
        _uiThreadOperationExecutor.Execute(EditorFeaturesResources.Peek, EditorFeaturesResources.Loading_Peek_information, allowCancellation: true, showProgress: false, action: context =>
        {
            _threadingContext.JoinableTaskFactory.Run(() => AugumentPeekSessionAsync(peekableItems, context, triggerPoint.Value, document));
        });
    }
 
    private async Task AugumentPeekSessionAsync(
        IList<IPeekableItem> peekableItems, IUIThreadOperationContext context, SnapshotPoint triggerPoint, Document document)
    {
        var cancellationToken = context.UserCancellationToken;
        var services = document.Project.Solution.Services;
 
        if (!document.SupportsSemanticModel)
        {
            // For documents without semantic models, just try to use the goto-def service
            // as a reasonable place to peek at.
            var service = document.GetLanguageService<INavigableItemsService>();
            if (service == null)
                return;
 
            var navigableItems = await service.GetNavigableItemsAsync(document, triggerPoint.Position, cancellationToken).ConfigureAwait(false);
            await foreach (var item in GetPeekableItemsForNavigableItemsAsync(
                navigableItems, document.Project, _peekResultFactory, cancellationToken).ConfigureAwait(false))
            {
                peekableItems.Add(item);
            }
        }
        else
        {
            var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
            var semanticInfo = await SymbolFinder.GetSemanticInfoAtPositionAsync(
                semanticModel,
                triggerPoint.Position,
                services,
                cancellationToken).ConfigureAwait(false);
            var symbol = semanticInfo.GetAnySymbol(includeType: true);
            if (symbol == null)
            {
                return;
            }
 
            symbol = symbol.GetOriginalUnreducedDefinition();
 
            // Get the symbol back from the originating workspace
            var symbolMappingService = services.GetRequiredService<ISymbolMappingService>();
 
            var mappingResult = await symbolMappingService.MapSymbolAsync(document, symbol, cancellationToken).ConfigureAwait(false);
 
            mappingResult ??= new SymbolMappingResult(document.Project, symbol);
 
            peekableItems.AddRange(await _peekableItemFactory.GetPeekableItemsAsync(
                mappingResult.Symbol, mappingResult.Project, _peekResultFactory, cancellationToken).ConfigureAwait(false));
        }
    }
 
    private static async IAsyncEnumerable<IPeekableItem> GetPeekableItemsForNavigableItemsAsync(
        IEnumerable<INavigableItem>? navigableItems, Project project,
        IPeekResultFactory peekResultFactory,
        [EnumeratorCancellation] CancellationToken cancellationToken)
    {
        if (navigableItems != null)
        {
            var workspace = project.Solution.Workspace;
            var navigationService = workspace.Services.GetRequiredService<IDocumentNavigationService>();
 
            foreach (var item in navigableItems)
            {
                var document = item.Document;
                if (await navigationService.CanNavigateToPositionAsync(
                        workspace, document.Id, item.SourceSpan.Start, cancellationToken).ConfigureAwait(false))
                {
                    var text = await document.GetTextAsync(project.Solution, cancellationToken).ConfigureAwait(false);
                    var linePositionSpan = text.Lines.GetLinePositionSpan(item.SourceSpan);
                    if (document.FilePath != null)
                    {
                        yield return new ExternalFilePeekableItem(
                            new FileLinePositionSpan(document.FilePath, linePositionSpan),
                            PredefinedPeekRelationships.Definitions, peekResultFactory);
                    }
                }
            }
        }
    }
 
    public void Dispose()
    {
    }
}