// 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.Collections.Generic;
using System.Threading;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders
{
    internal class VirtualKeywordRecommender : AbstractSyntacticSingleKeywordRecommender
    {
        private static readonly ISet<SyntaxKind> s_validNonInterfaceMemberModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.ExternKeyword,
            SyntaxKind.InternalKeyword,
            SyntaxKind.NewKeyword,
            SyntaxKind.PublicKeyword,
            SyntaxKind.ProtectedKeyword,
            SyntaxKind.PrivateKeyword,
            SyntaxKind.UnsafeKeyword,
        };
 
        private static readonly ISet<SyntaxKind> s_validInterfaceMemberModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.ExternKeyword,
            SyntaxKind.InternalKeyword,
            SyntaxKind.NewKeyword,
            SyntaxKind.PublicKeyword,
            SyntaxKind.ProtectedKeyword,
            SyntaxKind.PrivateKeyword,
            SyntaxKind.StaticKeyword,
            SyntaxKind.UnsafeKeyword,
        };
 
        public VirtualKeywordRecommender()
            : base(SyntaxKind.VirtualKeyword)
        {
        }
 
        protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
        {
            if (!context.IsMemberDeclarationContext(
                    validModifiers: s_validNonInterfaceMemberModifiers,
                    validTypeDeclarations: SyntaxKindSet.ClassRecordTypeDeclarations,
                    canBePartial: false,
                    cancellationToken: cancellationToken) &&
                !context.IsMemberDeclarationContext(
                    validModifiers: s_validInterfaceMemberModifiers,
                    validTypeDeclarations: SyntaxKindSet.InterfaceOnlyTypeDeclarations,
                    canBePartial: false,
                    cancellationToken: cancellationToken))
            {
                return false;
            }
 
            var modifiers = context.PrecedingModifiers;
            return !modifiers.Contains(SyntaxKind.PrivateKeyword) || modifiers.Contains(SyntaxKind.ProtectedKeyword);
        }
    }
}