// 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;

namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders;

internal sealed class ScopedKeywordRecommender() : AbstractSyntacticSingleKeywordRecommender(SyntaxKind.ScopedKeyword)
{
    protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        var syntaxTree = context.SyntaxTree;
        return
            syntaxTree.IsParameterModifierContext(position, context.LeftToken, includeOperators: true, out _, out _) ||
            syntaxTree.IsAnonymousMethodParameterModifierContext(position, context.LeftToken) ||
            syntaxTree.IsPossibleLambdaParameterModifierContext(position, context.LeftToken, cancellationToken) ||
            IsValidScopedLocalContext(context);
    }

    private static bool IsValidScopedLocalContext(CSharpSyntaxContext context)
    {
        // scoped ref var x ...
        if (context.IsStatementContext || context.IsGlobalStatementContext)
        {
            return true;
        }

        var token = context.TargetToken;
        switch (token.Kind())
        {
            // for (scoped ref var x ...
            // foreach (scoped ...
            case SyntaxKind.OpenParenToken:
                var previous = token.GetPreviousToken(includeSkipped: true);
                return previous.Kind() is SyntaxKind.ForKeyword or SyntaxKind.ForEachKeyword;

            // M(out scoped ..)
            case SyntaxKind.OutKeyword:
                return token.Parent is ArgumentSyntax;
        }

        return false;
    }
}