// 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.Threading;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Editor;
using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Editor;
using Roslyn.Utilities;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.Preview;
 
internal sealed partial class PreviewUpdater
{
    private PreviewDialogWorkspace? _previewWorkspace;
    private readonly ITextView _textView;
    private DocumentId? _currentDocumentId;
    private readonly PreviewTagger _tagger;
 
    public PreviewUpdater(ITextView textView)
    {
        _textView = textView;
        _tagger = new PreviewTagger(textView.TextBuffer);
        _textView.Properties[typeof(PreviewTagger)] = _tagger;
    }
 
    public void CloseWorkspace()
    {
        _previewWorkspace?.Dispose();
    }
 
    public void UpdateView(TextDocument document, SpanChange spanSource)
    {
        UpdateBuffer(document);
 
        // Picking a different span: no text change; update span anyway.
        _tagger.Span = spanSource.GetSpan();
        var spanInBuffer = new SnapshotSpan(_textView.TextBuffer.CurrentSnapshot, new Span(_tagger.Span.Start, 0));
        _textView.ViewScroller.EnsureSpanVisible(spanInBuffer, EnsureSpanVisibleOptions.None);
 
    }
 
    private void UpdateBuffer(TextDocument document)
    {
        // Note, even if the passed TextDocument has the same ID as _currentDocumentId, we still need
        // to refresh the buffer; if the user has a set of edits for a single document from a fix all operation,
        // you can check and uncheck the individual edits and we show the result. In that case, we're getting new
        // snapshots each time of the same document.
 
        if (document.Id == _currentDocumentId)
        {
            Contract.ThrowIfNull(_previewWorkspace, "We shouldn't have a current document if we don't have a workspace.");
            var existingDocument = _previewWorkspace.CurrentSolution.GetRequiredTextDocument(_currentDocumentId);
            if (existingDocument.GetTextSynchronously(CancellationToken.None).ContentEquals(document.GetTextSynchronously(CancellationToken.None)))
            {
                // The contents of the buffer matches what we'd update it to, so no reason to change.
                return;
            }
        }
 
        if (_currentDocumentId != null)
        {
            Contract.ThrowIfNull(_previewWorkspace, "We shouldn't have a current document if we don't have a workspace.");
            var currentDocument = _previewWorkspace.CurrentSolution.GetRequiredTextDocument(_currentDocumentId);
            var currentDocumentText = currentDocument.GetTextSynchronously(CancellationToken.None);
            _previewWorkspace.CloseDocument(currentDocument, currentDocumentText);
        }
 
        _previewWorkspace ??= new PreviewDialogWorkspace(document.Project.Solution);
 
        _currentDocumentId = document.Id;
        ApplyDocumentToBuffer(document, out var container);
        _previewWorkspace.OpenDocument(document.Id, container);
    }
 
    private void ApplyDocumentToBuffer(TextDocument document, out SourceTextContainer container)
    {
        var contentTypeService = document.Project.Services.GetRequiredService<IContentTypeLanguageService>();
        var contentType = contentTypeService.GetDefaultContentType();
 
        _textView.TextBuffer.ChangeContentType(contentType, null);
 
        var documentText = document.GetTextSynchronously(CancellationToken.None).ToString();
 
        using (var edit = _textView.TextBuffer.CreateEdit())
        {
            edit.Replace(new Span(0, _textView.TextBuffer.CurrentSnapshot.Length), documentText);
            edit.ApplyAndLogExceptions();
        }
 
        container = _textView.TextBuffer.AsTextContainer();
    }
}