// 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.
 
#nullable disable
 
using System.Linq;
using System.Text.RegularExpressions;
 
namespace Microsoft.CodeAnalysis.CSharp.Extensions;
 
internal partial class SyntaxNodeExtensions
{
    internal class SingleLineRewriter : CSharpSyntaxRewriter
    {
        private static readonly Regex s_newlinePattern = new(@"[\r\n]+");
 
        private readonly bool _useElasticTrivia;
        private bool _lastTokenEndedInWhitespace;
 
        public SingleLineRewriter(bool useElasticTrivia)
            => _useElasticTrivia = useElasticTrivia;
 
        public override SyntaxToken VisitToken(SyntaxToken token)
        {
            if (_lastTokenEndedInWhitespace)
            {
                token = token.WithLeadingTrivia(Enumerable.Empty<SyntaxTrivia>());
            }
            else if (token.LeadingTrivia.Count > 0)
            {
                if (_useElasticTrivia)
                {
                    token = token.WithLeadingTrivia(SyntaxFactory.ElasticSpace);
                }
                else
                {
                    token = token.WithLeadingTrivia(SyntaxFactory.Space);
                }
            }
 
            if (token.TrailingTrivia.Count > 0)
            {
                if (_useElasticTrivia)
                {
                    token = token.WithTrailingTrivia(SyntaxFactory.ElasticSpace);
                }
                else
                {
                    token = token.WithTrailingTrivia(SyntaxFactory.Space);
                }
 
                _lastTokenEndedInWhitespace = true;
            }
            else
            {
                _lastTokenEndedInWhitespace = false;
            }
 
            if (token.Kind() is SyntaxKind.StringLiteralToken or SyntaxKind.InterpolatedStringTextToken)
            {
                if (s_newlinePattern.IsMatch(token.Text))
                {
                    var newText = s_newlinePattern.Replace(token.Text, " ");
                    token = SyntaxFactory.Token(
                        token.LeadingTrivia,
                        token.Kind(),
                        newText, newText,
                        token.TrailingTrivia);
                }
            }
 
            return token;
        }
    }
}