// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;

namespace Microsoft.AspNetCore.Razor.Language.Syntax;

/// <summary>
/// Represents a <see cref="SyntaxVisitor"/> that descends an entire <see cref="SyntaxNode"/> graph
/// visiting each SyntaxNode and its child SyntaxNodes and <see cref="SyntaxToken"/>s in depth-first order.
/// An optional range can be passed in which reduces the <see cref="SyntaxNode"/>s and <see cref="SyntaxToken"/>s
/// visited to those overlapping with the given range.
/// </summary>
internal abstract class SyntaxWalker : SyntaxVisitor
{
    private int _recursionDepth;

    public override void Visit(SyntaxNode? node)
    {
        if (node != null)
        {
            Debug.Assert(!node.IsToken);
            Debug.Assert(!node.IsList);

            _recursionDepth++;
            StackGuard.EnsureSufficientExecutionStack(_recursionDepth);

            ((RazorSyntaxNode)node).Accept(this);

            _recursionDepth--;
        }
    }

    public override void DefaultVisit(SyntaxNode node)
    {
        Debug.Assert(!node.IsToken);
        Debug.Assert(!node.IsList);

        foreach (var child in node.ChildNodesAndTokens())
        {
            if (child.IsToken)
            {
                VisitToken(child.AsToken());
            }
            else
            {
                Visit(child.AsNode());
            }
        }
    }

    public virtual void VisitToken(SyntaxToken token)
    {
    }
}