// 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.Syntax;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders;
 
internal sealed class ParamKeywordRecommender() : AbstractSyntacticSingleKeywordRecommender(SyntaxKind.ParamKeyword)
{
    private static readonly ISet<SyntaxKind> s_validTypeDeclarations = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer);
 
    protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        var token = context.TargetToken;
 
        // `[field:` is legal in an attribute within a type.
        if (context.IsMemberAttributeContext(s_validTypeDeclarations, includingRecordParameters: true, cancellationToken))
            return true;
 
        if (context.IsRecordParameterAttributeContext(out _))
            return true;
 
        if (token.Kind() == SyntaxKind.OpenBracketToken &&
            token.Parent.IsKind(SyntaxKind.AttributeList))
        {
            if (token.GetAncestor<PropertyDeclarationSyntax>() != null ||
                token.GetAncestor<EventDeclarationSyntax>() != null)
            {
                return true;
            }
        }
 
        return false;
    }
}