// 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.ComponentModel.Composition;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Text.Shared.Extensions;
using Microsoft.VisualStudio.InteractiveWindow;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Classification;
using Microsoft.VisualStudio.Text.Editor;
 
namespace Microsoft.CodeAnalysis.Interactive;
 
/// <summary>
/// A classifier provider that caches the classification results from actual classifiers and
/// stores it on the text buffer so they can be used from that point on.  Used for interactive
/// buffers that have been reset but which we still want to look good.
/// </summary>
[Export(typeof(IClassifierProvider))]
[TextViewRole(PredefinedInteractiveTextViewRoles.InteractiveTextViewRole)]
internal sealed partial class InertClassifierProvider : IClassifierProvider
{
    private static readonly object s_classificationsKey = new object();
 
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public InertClassifierProvider()
    {
    }
 
    public IClassifier GetClassifier(ITextBuffer textBuffer)
        => new InertClassifier(textBuffer);
 
    internal static void CaptureExistingClassificationSpans(
        IViewClassifierAggregatorService classifierAggregator, ITextView textView, ITextBuffer textBuffer)
    {
        // No need to do this more than once.
        if (textBuffer.Properties.ContainsProperty(s_classificationsKey))
        {
            return;
        }
 
        // Capture the existing set of classifications and attach them to the buffer as a
        // property.
        var classifier = classifierAggregator.GetClassifier(textView);
        try
        {
            var classifications = classifier.GetClassificationSpans(textBuffer.CurrentSnapshot.GetFullSpan());
            textBuffer.Properties.AddProperty(s_classificationsKey, classifications);
        }
        finally
        {
            if (classifier is IDisposable disposable)
            {
                disposable.Dispose();
            }
        }
    }
}