// 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;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers
{
    internal static class DirectiveCompletionProviderUtilities
    {
        internal static bool TryGetStringLiteralToken(SyntaxTree tree, int position, SyntaxKind directiveKind, out SyntaxToken stringLiteral, CancellationToken cancellationToken)
        {
            if (tree.IsEntirelyWithinStringLiteral(position, cancellationToken))
            {
                var token = tree.GetRoot(cancellationToken).FindToken(position, findInsideTrivia: true);
                if (token.Kind() is SyntaxKind.EndOfDirectiveToken or SyntaxKind.EndOfFileToken)
                {
                    token = token.GetPreviousToken(includeSkipped: true, includeDirectives: true);
                }
 
                if (token.Kind() == SyntaxKind.StringLiteralToken && token.Parent!.Kind() == directiveKind)
                {
                    stringLiteral = token;
                    return true;
                }
            }
 
            stringLiteral = default;
            return false;
        }
    }
}