// 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.Immutable;
using System.Composition;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeDefinitionWindow;
using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.VisualStudio.Shell.Interop;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeDefinitionWindow;
 
[Export(typeof(ICodeDefinitionWindowService)), Shared]
internal sealed class VisualStudioCodeDefinitionWindowService : ICodeDefinitionWindowService
{
    private readonly IVsService<IVsCodeDefView> _codeDefView;
    private readonly IThreadingContext _threadingContext;
 
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public VisualStudioCodeDefinitionWindowService(IVsService<SVsCodeDefView, IVsCodeDefView> codeDefView, IThreadingContext threadingContext)
    {
        _codeDefView = codeDefView;
        _threadingContext = threadingContext;
    }
 
    public async Task<bool> IsWindowOpenAsync(CancellationToken cancellationToken)
    {
        var vsCodeDefView = await _codeDefView.GetValueAsync(cancellationToken).ConfigureAwait(true);
 
        // Switch to the UI thread before using the IVsCodeDefView service
        await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
 
        // IsVisible returns S_FALSE if it's not visible
        return vsCodeDefView.IsVisible() == VSConstants.S_OK;
    }
 
    public async Task SetContextAsync(ImmutableArray<CodeDefinitionWindowLocation> locations, CancellationToken cancellationToken)
    {
        // If the new context has no location, then just don't update, instead of showing the
        // "No definition selected" page.
        if (!locations.Any())
        {
            return;
        }
 
        var vsCodeDefView = await _codeDefView.GetValueAsync(cancellationToken).ConfigureAwait(true);
 
        // Switch to the UI thread before using the IVsCodeDefView service
        await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
 
        Marshal.ThrowExceptionForHR(vsCodeDefView.SetContext(new Context(locations)));
    }
 
    private class Context : IVsCodeDefViewContext
    {
        private readonly ImmutableArray<CodeDefinitionWindowLocation> _locations;
 
        public Context(ImmutableArray<CodeDefinitionWindowLocation> locations)
        {
            _locations = locations;
        }
 
        int IVsCodeDefViewContext.GetCount(out uint pcItems)
        {
            pcItems = (uint)_locations.Length;
            return VSConstants.S_OK;
        }
 
        int IVsCodeDefViewContext.GetSymbolName(uint iItem, out string pbstrSymbolName)
        {
            pbstrSymbolName = GetItem(iItem).DisplayName;
            return VSConstants.S_OK;
        }
 
        int IVsCodeDefViewContext.GetFileName(uint iItem, out string pbstrFilename)
        {
            pbstrFilename = GetItem(iItem).FilePath;
            return VSConstants.S_OK;
        }
 
        int IVsCodeDefViewContext.GetLine(uint iItem, out uint piLine)
        {
            piLine = (uint)GetItem(iItem).Position.Line;
            return VSConstants.S_OK;
        }
 
        int IVsCodeDefViewContext.GetCol(uint iItem, out uint piCol)
        {
            piCol = (uint)GetItem(iItem).Position.Character;
            return VSConstants.S_OK;
        }
 
        private CodeDefinitionWindowLocation GetItem(uint iItem)
        {
            var index = (int)iItem;
            if (index < 0 || index >= _locations.Length)
            {
                throw new ArgumentOutOfRangeException(nameof(iItem));
            }
 
            return _locations[index];
        }
    }
}