// 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;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Linq;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Tagging;
using Microsoft.VisualStudio.Utilities;
 
namespace Roslyn.Hosting.Diagnostics.VenusMargin;
 
[Export(typeof(IViewTaggerProvider))]
[ContentType("text")]
[TagType(typeof(TextMarkerTag))]
internal sealed class ProjectionSpanTaggerProvider : IViewTaggerProvider
{
    public const string PropertyName = "Projection Tags";
 
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public ProjectionSpanTaggerProvider()
    {
    }
 
    public ITagger<T> CreateTagger<T>(ITextView textView, ITextBuffer buffer) where T : ITag
    {
        return new Tagger(textView) as ITagger<T>;
    }
 
    internal sealed class Tagger : ITagger<TextMarkerTag>, IDisposable
    {
        private readonly ITextView _textView;
 
        public Tagger(ITextView textView)
        {
            _textView = textView;
 
            ProjectionBufferMargin.SelectionChanged += OnProjectionBufferMarginSelectionChanged;
        }
 
        public event EventHandler<SnapshotSpanEventArgs> TagsChanged;
 
        private void OnProjectionBufferMarginSelectionChanged(object sender, EventArgs e)
        {
            var snapshot = _textView.TextBuffer.CurrentSnapshot;
            RaiseTagsChanged(new SnapshotSpanEventArgs(new SnapshotSpan(snapshot, new Span(0, snapshot.Length))));
        }
 
        private void RaiseTagsChanged(SnapshotSpanEventArgs args)
        {
            this.TagsChanged?.Invoke(this, args);
        }
 
        IEnumerable<ITagSpan<TextMarkerTag>> ITagger<TextMarkerTag>.GetTags(NormalizedSnapshotSpanCollection spans)
            => GetTags(spans);
 
        public IEnumerable<TagSpan<TextMarkerTag>> GetTags(NormalizedSnapshotSpanCollection spans)
        {
            if (!_textView.Properties.TryGetProperty(PropertyName, out List<Span> allSpans))
                return [];
 
            return allSpans
                .Where(s => spans.Any(ss => ss.IntersectsWith(s)))
                .Select(s => new TagSpan<TextMarkerTag>(new SnapshotSpan(spans.First().Snapshot, s), ProjectionSpanTag.Instance));
        }
 
        public void Dispose()
        {
            ProjectionBufferMargin.SelectionChanged -= OnProjectionBufferMarginSelectionChanged;
        }
    }
}