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

namespace Microsoft.AspNetCore.Razor.Language.Syntax.InternalSyntax
{
	internal abstract partial class SyntaxRewriter : SyntaxVisitor<GreenNode>
	{
		public override GreenNode VisitToken( SyntaxToken token )
		{
			var leading = VisitList( token.LeadingTrivia );
			var trailing = VisitList( token.TrailingTrivia );

			if ( leading != token.LeadingTrivia || trailing != token.TrailingTrivia )
			{
				if ( leading != token.LeadingTrivia )
				{
					token = token.TokenWithLeadingTrivia( leading.Node );
				}

				if ( trailing != token.TrailingTrivia )
				{
					token = token.TokenWithTrailingTrivia( trailing.Node );
				}
			}

			return token;
		}

		public SyntaxList<TNode> VisitList<TNode>( SyntaxList<TNode> list ) where TNode : GreenNode
		{
			SyntaxListBuilder alternate = null;
			for ( int i = 0, n = list.Count; i < n; i++ )
			{
				var item = list[i];
				var visited = Visit( item );
				if ( item != visited && alternate == null )
				{
					alternate = new SyntaxListBuilder( n );
					alternate.AddRange( list, 0, i );
				}

				if ( alternate != null )
				{
					alternate.Add( visited );
				}
			}

			if ( alternate != null )
			{
				return alternate.ToList<TNode>();
			}

			return list;
		}
	}
}
