// 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.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders
{
    internal class AliasKeywordRecommender : AbstractSyntacticSingleKeywordRecommender
    {
        public AliasKeywordRecommender()
            : base(SyntaxKind.AliasKeyword)
        {
        }
 
        protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
        {
            // cases:
            //   extern |
            //   extern a|
            var token = context.TargetToken;
 
            if (token.Kind() == SyntaxKind.ExternKeyword)
            {
                // members can be 'extern' but we don't want
                // 'alias' to show up in a 'type'.
                return token.GetAncestor<TypeDeclarationSyntax>() == null;
            }
 
            return false;
        }
    }
}