// 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;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Utilities;

namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders;

internal sealed class AsyncKeywordRecommender() : AbstractSyntacticSingleKeywordRecommender(SyntaxKind.AsyncKeyword, isValidInPreprocessorContext: false)
{
    private static readonly ISet<SyntaxKind> s_validLocalFunctionModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
    {
        SyntaxKind.StaticKeyword,
        SyntaxKind.UnsafeKeyword
    };

    protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        if (context.TargetToken.IsKindOrHasMatchingText(SyntaxKind.PartialKeyword) ||
            context.PrecedingModifiers.Contains(SyntaxKind.AsyncKeyword))
        {
            return false;
        }

        return InMemberDeclarationContext(position, context, cancellationToken)
            || context.SyntaxTree.IsLambdaDeclarationContext(position, otherModifier: SyntaxKind.StaticKeyword, cancellationToken)
            || context.SyntaxTree.IsLocalFunctionDeclarationContext(position, s_validLocalFunctionModifiers, cancellationToken);
    }

    private static bool InMemberDeclarationContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        return context.IsGlobalStatementContext
            || context.SyntaxTree.IsGlobalMemberDeclarationContext(position, SyntaxKindSet.AllGlobalMemberModifiers, cancellationToken)
            || context.IsMemberDeclarationContext(
                validModifiers: SyntaxKindSet.AllMemberModifiers,
                validTypeDeclarations: SyntaxKindSet.NonEnumTypeDeclarations,
                canBePartial: true,
                cancellationToken: cancellationToken);
    }
}