//------------------------------------------------------------------------------
// <copyright file="XPathNodeList.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>                                                                
// <owner current="true" primary="true">[....]</owner>
//------------------------------------------------------------------------------

namespace System.Xml {
    using System.Xml.XPath;
    using System.Diagnostics;
    using System.Collections;
    using System.Collections.Generic;

    internal class XPathNodeList: XmlNodeList {
        List<XmlNode> list;
        XPathNodeIterator nodeIterator;
        bool done;

        public XPathNodeList(XPathNodeIterator nodeIterator) {
            this.nodeIterator = nodeIterator;
            this.list = new List<XmlNode>();
            this.done = false;
        }

        public override int Count {
            get {
                if (! done) {
                    ReadUntil(Int32.MaxValue);
                }
                return list.Count;
            }
        }

        private static readonly object[] nullparams = {};

        private XmlNode GetNode(XPathNavigator n) {
            IHasXmlNode iHasNode = (IHasXmlNode) n;
            return iHasNode.GetNode();
        }

        internal int ReadUntil(int index) {
            int count = list.Count;
            while (! done && count <= index) {
                if (nodeIterator.MoveNext()) {
                    XmlNode n = GetNode(nodeIterator.Current);
                    if (n != null) {
                        list.Add(n);
                        count++;
                    }
                } else {
                    done = true;
                    break;
                }
            }
            return count;
        }

        public override XmlNode Item(int index) {
            if (list.Count <= index) {
                ReadUntil(index);
            }
            if (index < 0 || list.Count <= index) {
                return null;
            }
            return list[index];
        }

        public override IEnumerator GetEnumerator() {
            return new XmlNodeListEnumerator(this);
        }
    }

    internal class XmlNodeListEnumerator : IEnumerator {
        XPathNodeList list;
        int index;
        bool valid;

        public XmlNodeListEnumerator(XPathNodeList list) {
            this.list = list;
            this.index = -1;
            this.valid = false;
        }

        public void Reset() {
            index = -1;
        }

        public bool MoveNext() {
            index++;
            int count = list.ReadUntil(index + 1);   // read past for delete-node case
            if (count - 1 < index) {
                return false;
            }
            valid = (list[index] != null);
            return valid;
        }

       public object Current {
            get {
                if (valid) {
                    return list[index];
                }
                return null;
            }
        }
    }
}