// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections;
using System.Xml;
 
namespace System.Security.Cryptography.Xml
{
    internal sealed class NamespaceSortOrder : IComparer
    {
        internal NamespaceSortOrder() { }
 
        public int Compare(object? a, object? b)
        {
            XmlNode? nodeA = a as XmlNode;
            XmlNode? nodeB = b as XmlNode;
            if ((nodeA == null) || (nodeB == null))
                throw new ArgumentException();
            bool nodeAdefault = Utils.IsDefaultNamespaceNode(nodeA);
            bool nodeBdefault = Utils.IsDefaultNamespaceNode(nodeB);
            if (nodeAdefault && nodeBdefault) return 0;
            if (nodeAdefault) return -1;
            if (nodeBdefault) return 1;
            return string.CompareOrdinal(nodeA.LocalName, nodeB.LocalName);
        }
    }
}