// 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.Composition;
using System.Linq;
using System.Threading;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.Highlighting;

[Export(typeof(IHighlightingService))]
[Shared]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed class HighlightingService(
    [ImportMany] IEnumerable<Lazy<IHighlighter, LanguageMetadata>> highlighters) : IHighlightingService
{
    private readonly List<Lazy<IHighlighter, LanguageMetadata>> _highlighters = [.. highlighters];
    private static readonly PooledObjects.ObjectPool<List<TextSpan>> s_listPool = new(() => []);

    public void AddHighlights(
         SyntaxNode root, int position, List<TextSpan> highlights, CancellationToken cancellationToken)
    {
        using (s_listPool.GetPooledObject(out var tempHighlights))
        {
            foreach (var highlighter in _highlighters.Where(h => h.Metadata.Language == root.Language))
            {
                cancellationToken.ThrowIfCancellationRequested();
                highlighter.Value.AddHighlights(root, position, tempHighlights, cancellationToken);
            }

            tempHighlights.Sort();
            var lastSpan = default(TextSpan);
            foreach (var span in tempHighlights)
            {
                if (span != lastSpan && !span.IsEmpty)
                {
                    highlights.Add(span);
                    lastSpan = span;
                }
            }
        }
    }
}