// 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.Linq;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.Host.Mef;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Shared.Extensions
{
    internal static class ILanguageServiceProviderExtensions
    {
        public static IEnumerable<Lazy<T, TMetadata>> SelectMatchingExtensions<T, TMetadata>(
            this HostLanguageServices serviceProvider,
            IEnumerable<Lazy<T, TMetadata>>? items)
            where TMetadata : ILanguageMetadata
        {
            if (items == null)
            {
                return SpecializedCollections.EmptyEnumerable<Lazy<T, TMetadata>>();
            }
 
            return items.Where(lazy => lazy.Metadata.Language == serviceProvider.Language);
        }
    }
}