// 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;
using System.Collections.Generic;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Rename.ConflictEngine;
 
namespace Microsoft.CodeAnalysis.CSharp.Rename
{
    internal sealed class LabelConflictVisitor : CSharpSyntaxVisitor
    {
        private readonly ConflictingIdentifierTracker _tracker;
 
        public LabelConflictVisitor(SyntaxToken tokenBeingRenamed)
            => _tracker = new ConflictingIdentifierTracker(tokenBeingRenamed, StringComparer.Ordinal);
 
        public override void DefaultVisit(SyntaxNode node)
        {
            foreach (var child in node.ChildNodes())
            {
                Visit(child);
            }
        }
 
        public override void VisitBlock(BlockSyntax node)
        {
            var tokens = new List<SyntaxToken>();
 
            // We want to collect any labels and add them all at once for this scope
            foreach (var statement in node.Statements)
            {
                if (statement is LabeledStatementSyntax declarationStatement)
                {
                    tokens.Add(declarationStatement.Identifier);
                }
            }
 
            _tracker.AddIdentifiers(tokens);
            DefaultVisit(node);
            _tracker.RemoveIdentifiers(tokens);
        }
 
        public IEnumerable<SyntaxToken> ConflictingTokens
        {
            get
            {
                return _tracker.ConflictingTokens;
            }
        }
    }
}