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

using System.Xml;
using System.Xml.XPath;

namespace MS.Internal.Xml.XPath
{
    internal sealed class XPathAncestorQuery : CacheAxisQuery
    {
        private readonly bool _matchSelf;

        public XPathAncestorQuery(Query qyInput, string name, string prefix, XPathNodeType typeTest, bool matchSelf) : base(qyInput, name, prefix, typeTest)
        {
            _matchSelf = matchSelf;
        }
        private XPathAncestorQuery(XPathAncestorQuery other) : base(other)
        {
            _matchSelf = other._matchSelf;
        }

        public override object Evaluate(XPathNodeIterator context)
        {
            base.Evaluate(context);

            XPathNavigator? ancestor = null;
            XPathNavigator? input;
            while ((input = qyInput.Advance()) != null)
            {
                if (_matchSelf)
                {
                    if (matches(input))
                    {
                        if (!Insert(outputBuffer, input))
                        {
                            // If input is already in output buffer all its ancestors are in a buffer as well.
                            continue;
                        }
                    }
                }
                if (ancestor == null || !ancestor.MoveTo(input))
                {
                    ancestor = input.Clone();
                }
                while (ancestor.MoveToParent())
                {
                    if (matches(ancestor))
                    {
                        if (!Insert(outputBuffer, ancestor))
                        {
                            // If input is already in output buffer all its ancestors are in a buffer as well.
                            break;
                        }
                    }
                }
            }
            return this;
        }

        public override XPathNodeIterator Clone() { return new XPathAncestorQuery(this); }
        public override int CurrentPosition { get { return outputBuffer.Count - count + 1; } }
        public override QueryProps Properties { get { return base.Properties | QueryProps.Reverse; } }
    }
}