// 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 sealed class FixedKeywordRecommender() : AbstractSyntacticSingleKeywordRecommender(SyntaxKind.FixedKeyword)
{
    private static readonly ISet<SyntaxKind> s_structDeclaration = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
    {
        SyntaxKind.StructDeclaration,
    };

    private static readonly ISet<SyntaxKind> s_validModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
    {
        SyntaxKind.NewKeyword,
        SyntaxKind.PublicKeyword,
        SyntaxKind.ProtectedKeyword,
        SyntaxKind.InternalKeyword,
        SyntaxKind.PrivateKeyword,
        SyntaxKind.UnsafeKeyword,
    };

    protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
        => context.IsStatementContext || IsMemberDeclarationContext(context, cancellationToken);

    private static bool IsMemberDeclarationContext(CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        return
           context.SyntaxTree.IsGlobalMemberDeclarationContext(context.Position, SyntaxKindSet.AllGlobalMemberModifiers, cancellationToken) ||
           context.IsMemberDeclarationContext(validModifiers: s_validModifiers, validTypeDeclarations: s_structDeclaration, canBePartial: false, cancellationToken);
    }
}