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

namespace MS.Internal.Xml.XPath {
    using System;
    using System.Xml;
    using System.Xml.XPath;
    using System.Diagnostics;
    using System.Collections.Generic;
    using StackNav = ClonableStack<System.Xml.XPath.XPathNavigator>;

    internal sealed class FollSiblingQuery : BaseAxisQuery {
        StackNav              elementStk;
        List<XPathNavigator>  parentStk;
        XPathNavigator        nextInput;
		
        public FollSiblingQuery(Query qyInput, string name, string prefix, XPathNodeType type) : base (qyInput, name, prefix, type) {
            this.elementStk = new StackNav();
            this.parentStk  = new List<XPathNavigator>();
        }
        private FollSiblingQuery(FollSiblingQuery other) : base(other) {
            this.elementStk = other.elementStk.Clone();
            this.parentStk = new List<XPathNavigator>(other.parentStk);
            this.nextInput = Clone(other.nextInput);
        }

        public override void Reset() {
            elementStk.Clear();
            parentStk.Clear();
            nextInput = null;
            base.Reset();
        }

        private bool Visited(XPathNavigator nav) {
            XPathNavigator parent = nav.Clone();
            parent.MoveToParent();
            for (int i = 0; i < parentStk.Count; i++) {
                if (parent.IsSamePosition(parentStk[i])) {
                    return true;
                }
            }
            parentStk.Add(parent);
            return false;
        }

        private XPathNavigator FetchInput() {
            XPathNavigator input;
            do {
                input = qyInput.Advance();
                if (input == null) {
                    return null;
                }
            } while (Visited(input));
            return input.Clone();
        }

        public override XPathNavigator Advance() {
        	while (true) {
                if (currentNode == null) {
                    if (nextInput == null) {
                        nextInput = FetchInput(); // This can happen at the begining and at the end 
                    }
                    if (elementStk.Count == 0) {
                        if (nextInput == null) {
                            return null;
                        }
                        currentNode = nextInput;
                        nextInput = FetchInput();
                    } else {
                        currentNode = elementStk.Pop();
                    }
                }

                while (currentNode.IsDescendant(nextInput)) {
                    elementStk.Push(currentNode);
                    currentNode = nextInput;
                    nextInput = qyInput.Advance();
                    if (nextInput != null) {
                        nextInput = nextInput.Clone();
                    }
                }

				while (currentNode.MoveToNext()) {
				    if (matches(currentNode)) {
				        position++;
    				    return currentNode;
			        }
			    }
		        currentNode = null;
			}
        } // Advance
                
        public override XPathNodeIterator Clone() { return new FollSiblingQuery(this); }
    }
}