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

using System.IO;
using System.Xml.Schema;
using System.Collections;
using System.Diagnostics;
using System.Collections.Generic;


namespace System.Xml.XPath {

    /// <summary>
    /// Reader that traverses the subtree rooted at the current position of the specified navigator.
    /// </summary>
    internal class XPathNavigatorReader : XmlReader, IXmlNamespaceResolver {
        enum State {
            Initial,
            Content,
            EndElement,
            Attribute,
            AttrVal,
            InReadBinary,
            EOF,
            Closed,
            Error,
        }

        private XPathNavigator nav;
        private XPathNavigator navToRead;
        private int depth;
        private State state;
        private XmlNodeType nodeType;
        private int attrCount;
        private bool readEntireDocument;

        protected IXmlLineInfo lineInfo;
        protected IXmlSchemaInfo schemaInfo;

        private ReadContentAsBinaryHelper   readBinaryHelper;
        private State                       savedState;

        internal const string space = "space";

        internal static XmlNodeType[] convertFromXPathNodeType = {
            XmlNodeType.Document,               // XPathNodeType.Root
            XmlNodeType.Element,                // XPathNodeType.Element
            XmlNodeType.Attribute,              // XPathNodeType.Attribute
            XmlNodeType.Attribute,              // XPathNodeType.Namespace
            XmlNodeType.Text,                   // XPathNodeType.Text
            XmlNodeType.SignificantWhitespace,  // XPathNodeType.SignificantWhitespace
            XmlNodeType.Whitespace,             // XPathNodeType.Whitespace
            XmlNodeType.ProcessingInstruction,  // XPathNodeType.ProcessingInstruction
            XmlNodeType.Comment,                // XPathNodeType.Comment
            XmlNodeType.None                    // XPathNodeType.All
        };

        /// <summary>
        /// Translates an XPathNodeType value into the corresponding XmlNodeType value.
        /// XPathNodeType.Whitespace and XPathNodeType.SignificantWhitespace are mapped into XmlNodeType.Text.
        /// </summary>
        internal static XmlNodeType ToXmlNodeType( XPathNodeType typ ) {
            return XPathNavigatorReader.convertFromXPathNodeType[(int) typ];
        }

        internal object UnderlyingObject {
            get {
                return this.nav.UnderlyingObject;
            }
        }

        static public XPathNavigatorReader Create(XPathNavigator navToRead ) {
            XPathNavigator nav = navToRead.Clone();
            IXmlLineInfo xli = nav as IXmlLineInfo;
            IXmlSchemaInfo xsi = nav as IXmlSchemaInfo;
#if NAVREADER_SUPPORTSLINEINFO
            if (null == xsi) {
                if (null == xli) {
                    return new XPathNavigatorReader(nav, xli, xsi);
                }
                else {
                    return new XPathNavigatorReaderWithLI(nav, xli, xsi);
                }
            }
            else {
                if (null == xli) {
                    return new XPathNavigatorReaderWithSI(nav, xli, xsi);
                }
                else {
                    return new XPathNavigatorReaderWithLIAndSI(nav, xli, xsi);
                }
            }
#else
            if (null == xsi) {
                return new XPathNavigatorReader(nav, xli, xsi);
            }
            else {
                return new XPathNavigatorReaderWithSI(nav, xli, xsi);
            }
#endif
        }

        protected XPathNavigatorReader( XPathNavigator navToRead, IXmlLineInfo xli, IXmlSchemaInfo xsi ) {
            // Need clone that can be moved independently of original navigator
            this.navToRead = navToRead;
            this.lineInfo = xli;
            this.schemaInfo = xsi;
            this.nav = XmlEmptyNavigator.Singleton;
            this.state = State.Initial;
            this.depth = 0;
            this.nodeType = XPathNavigatorReader.ToXmlNodeType( this.nav.NodeType );
        }

        protected bool IsReading { 
            get { return this.state > State.Initial && this.state < State.EOF; } 
        }

        internal override XmlNamespaceManager NamespaceManager {
            get { return XPathNavigator.GetNamespaces( this ); }
        }


        //-----------------------------------------------
        // IXmlNamespaceResolver -- pass through to Navigator
        //-----------------------------------------------
        public override XmlNameTable NameTable {
            get {
                return this.navToRead.NameTable;
            }
        }

        IDictionary<string,string> IXmlNamespaceResolver.GetNamespacesInScope(XmlNamespaceScope scope) {
            return this.nav.GetNamespacesInScope(scope);
        }

        string IXmlNamespaceResolver.LookupNamespace(string prefix) {
            return this.nav.LookupNamespace(prefix);
        }

        string IXmlNamespaceResolver.LookupPrefix(string namespaceName) {
            return this.nav.LookupPrefix(namespaceName);
        }

        //-----------------------------------------------
        // XmlReader -- pass through to Navigator
        //-----------------------------------------------

        public override XmlReaderSettings Settings {
            get {
                XmlReaderSettings rs = new XmlReaderSettings();
                rs.NameTable = this.NameTable;
                rs.ConformanceLevel = ConformanceLevel.Fragment;
                rs.CheckCharacters = false;
                rs.ReadOnly = true;
                return rs;
            }
        }

        public override IXmlSchemaInfo SchemaInfo {
            get {
                // Special case attribute text (this.nav points to attribute even though current state is Text)
                if ( this.nodeType == XmlNodeType.Text )
                    return null;
                return this.nav.SchemaInfo;
            }
        }

        public override System.Type ValueType {
            get { return this.nav.ValueType; }
        }

        public override XmlNodeType NodeType {
            get { return this.nodeType; }
        }

        public override string NamespaceURI {
            get {
                //NamespaceUri for namespace nodes is different in case of XPathNavigator and Reader
                if (this.nav.NodeType == XPathNodeType.Namespace)
                    return this.NameTable.Add(XmlReservedNs.NsXmlNs);
                //Special case attribute text node
                if (this.NodeType == XmlNodeType.Text)
                    return string.Empty;
                return this.nav.NamespaceURI; 
            }
        }

        public override string LocalName {
            get {
                //Default namespace in case of reader has a local name value of 'xmlns'
                if (this.nav.NodeType == XPathNodeType.Namespace && this.nav.LocalName.Length == 0)
                    return this.NameTable.Add("xmlns");
                //Special case attribute text node
                if (this.NodeType == XmlNodeType.Text)
                    return string.Empty;
                return this.nav.LocalName; 
            }
        }

        public override string Prefix {
            get {
                //Prefix for namespace nodes is different in case of XPathNavigator and Reader
                if (this.nav.NodeType == XPathNodeType.Namespace && this.nav.LocalName.Length != 0)
                    return this.NameTable.Add("xmlns");
                //Special case attribute text node
                if (this.NodeType == XmlNodeType.Text)
                    return string.Empty;
                return this.nav.Prefix; 
            }
        }

        public override string BaseURI {
            get { 
                //reader returns BaseUri even before read method is called.
                if( this.state == State.Initial )
                    return this.navToRead.BaseURI; 
                return this.nav.BaseURI;
            }
        }

        public override bool IsEmptyElement { 
            get {
                return this.nav.IsEmptyElement;
            }
        }        

        public override XmlSpace XmlSpace { 
            get {
                XPathNavigator tempNav = this.nav.Clone();
                do {
                    if (tempNav.MoveToAttribute(XPathNavigatorReader.space, XmlReservedNs.NsXml)) {
                        switch (XmlConvert.TrimString(tempNav.Value)) {
                            case "default":
                                return XmlSpace.Default;
                            case "preserve":
                                return XmlSpace.Preserve;
                            default:
                                break;
                        }
                        tempNav.MoveToParent();
                    }                    
                } 
                while (tempNav.MoveToParent());
                return XmlSpace.None;
            }        
        }        

        public override string XmlLang { 
            get {
                return this.nav.XmlLang;
            }
        }              

        public override bool HasValue { 
            get {
                if( ( this.nodeType != XmlNodeType.Element ) 
                    && ( this.nodeType !=XmlNodeType.Document ) 
                    && ( this.nodeType !=XmlNodeType.EndElement ) 
                    && ( this.nodeType !=XmlNodeType.None ) )
                    return true;
                return false;
            }        
        }

        public override string Value {
            get {
                if( ( this.nodeType != XmlNodeType.Element ) 
                    && ( this.nodeType !=XmlNodeType.Document ) 
                    && ( this.nodeType !=XmlNodeType.EndElement ) 
                    && ( this.nodeType !=XmlNodeType.None ) )
                    return this.nav.Value;
                return string.Empty;
            }
        }

        private XPathNavigator GetElemNav() {
            XPathNavigator tempNav;
            switch (this.state) {
                case State.Content:
                    return this.nav.Clone();
                case State.Attribute:
                case State.AttrVal:
                    tempNav = this.nav.Clone();
                    if (tempNav.MoveToParent())
                        return tempNav;
                    break;
                case State.InReadBinary:
                    state = savedState;
                    XPathNavigator nav = GetElemNav();
                    state = State.InReadBinary;
                    return nav;
            }
            return null;
        }

        private XPathNavigator GetElemNav(out int depth) {
            XPathNavigator nav = null;
            switch (this.state) {
                case State.Content:
                    if (this.nodeType == XmlNodeType.Element)
                        nav = this.nav.Clone();
                    depth = this.depth;
                    break;
                case State.Attribute:
                    nav = this.nav.Clone();
                    nav.MoveToParent();
                    depth = this.depth - 1;
                    break;
                case State.AttrVal:
                    nav = this.nav.Clone();
                    nav.MoveToParent();
                    depth = this.depth - 2;
                    break;
                case State.InReadBinary:
                    state = savedState;
                    nav = GetElemNav(out depth);
                    state = State.InReadBinary;
                    break;
                default:
                    depth = this.depth;
                    break;
            }
            return nav;
        }

        private void MoveToAttr(XPathNavigator nav, int depth) {
            this.nav.MoveTo( nav );
            this.depth = depth;
            this.nodeType = XmlNodeType.Attribute;
            this.state = State.Attribute;
        }

        public override int AttributeCount {
            get {
                if ( this.attrCount < 0 ) {
                    // attribute count works for element, regardless of where you are in start tag
                    XPathNavigator tempNav = GetElemNav();
                    int count = 0;
                    if ( null != tempNav ) {
                        if( tempNav.MoveToFirstNamespace( XPathNamespaceScope.Local ) ) {
                            do {
                                count++;
                            } while( tempNav.MoveToNextNamespace( ( XPathNamespaceScope.Local ) ) );
                            tempNav.MoveToParent();
                        }                
                        if( tempNav.MoveToFirstAttribute() ) {
                            do {
                                count++;
                            } while( tempNav.MoveToNextAttribute() );                                        
                        }
                    }
                    this.attrCount = count;
                }
                return this.attrCount;
            }
        }

        public override string GetAttribute( string name ) {
            // reader allows calling GetAttribute, even when positioned inside attributes
            XPathNavigator nav = this.nav;
            switch (nav.NodeType) {
                case XPathNodeType.Element:
                    break;
                case XPathNodeType.Attribute:
                    nav = nav.Clone();
                    if (!nav.MoveToParent())
                        return null;
                    break;
                default:
                    return null;
            }
            string prefix, localname;
            ValidateNames.SplitQName( name, out prefix, out localname );
            if ( 0 == prefix.Length ) {
                if( localname == "xmlns" )
                    return nav.GetNamespace( string.Empty );
                if ( (object)nav == (object)this.nav )
                    nav = nav.Clone();
                if ( nav.MoveToAttribute( localname, string.Empty ) )
                    return nav.Value;
            }
            else {
                if( prefix == "xmlns" )
                    return nav.GetNamespace( localname );
                if ((object)nav == (object)this.nav)
                    nav = nav.Clone();
                if (nav.MoveToFirstAttribute()) {
                    do {
                        if (nav.LocalName == localname && nav.Prefix == prefix)
                            return nav.Value;
                    } while (nav.MoveToNextAttribute());
                }
            }
            return null;
        }

        public override string GetAttribute( string localName, string namespaceURI ) {
            if ( null == localName )
                throw new ArgumentNullException("localName");
            // reader allows calling GetAttribute, even when positioned inside attributes
            XPathNavigator nav = this.nav;
            switch (nav.NodeType) {
                case XPathNodeType.Element:
                    break;
                case XPathNodeType.Attribute:
                    nav = nav.Clone();
                    if (!nav.MoveToParent())
                        return null;
                    break;
                default:
                    return null;
            }
            // are they really looking for a namespace-decl?
            if( namespaceURI == XmlReservedNs.NsXmlNs ) {
                if (localName == "xmlns")
                    localName = string.Empty;
                return nav.GetNamespace( localName );
            }
            if ( null == namespaceURI )
                namespaceURI = string.Empty;
            // We need to clone the navigator and move the clone to the attribute to see whether the attribute exists, 
            // because XPathNavigator.GetAttribute return string.Empty for both when the the attribute is not there or when 
            // it has an empty value. XmlReader.GetAttribute must return null if the attribute does not exist.
            if ((object)nav == (object)this.nav)
                nav = nav.Clone();
            if ( nav.MoveToAttribute( localName, namespaceURI ) ) {
                return nav.Value;
            }
            else {
                return null;
            }
        }

        private static string GetNamespaceByIndex( XPathNavigator nav, int index, out int count ) {
            string thisValue = nav.Value;
            string value = null;
            if ( nav.MoveToNextNamespace( XPathNamespaceScope.Local ) ) {
                value = GetNamespaceByIndex( nav, index, out count );
            }
            else {
                count = 0;
            }
            if ( count == index ) {
                Debug.Assert( value == null );
                value = thisValue;
            }
            count++;
            return value;
        }

        public override string GetAttribute( int index ) {
            if (index < 0)
                goto Error;
            XPathNavigator nav = GetElemNav();
            if (null == nav)
                goto Error;
            if ( nav.MoveToFirstNamespace( XPathNamespaceScope.Local ) ) {
                // namespaces are returned in reverse order, 
                // but we want to return them in the correct order,
                // so first count the namespaces
                int nsCount;
                string value = GetNamespaceByIndex( nav, index, out nsCount );
                if ( null != value ) {
                    return value;
                }
                index -= nsCount;
                nav.MoveToParent();
            }
            if ( nav.MoveToFirstAttribute() ) {
                do {
                    if (index == 0)
                        return nav.Value;
                    index--;
                } while ( nav.MoveToNextAttribute() );
            }
            // can't find it... error
        Error:
            throw new ArgumentOutOfRangeException("index");
        }


        public override bool MoveToAttribute( string localName, string namespaceName ) {
            if ( null == localName )
                throw new ArgumentNullException("localName");
            int depth = this.depth;
            XPathNavigator nav = GetElemNav(out depth);
            if (null != nav) {
                if ( namespaceName == XmlReservedNs.NsXmlNs ) {
                    if (localName == "xmlns")
                        localName = string.Empty;
                    if(  nav.MoveToFirstNamespace( XPathNamespaceScope.Local ) ) {
                        do {
                            if ( nav.LocalName == localName )
                                goto FoundMatch;
                        } while( nav.MoveToNextNamespace( XPathNamespaceScope.Local ) );
                    }
                }
                else {
                    if (null == namespaceName)
                        namespaceName = string.Empty;
                    if ( nav.MoveToAttribute( localName, namespaceName ) )
                        goto FoundMatch;
                }
            }
            return false;

        FoundMatch:
            if ( state == State.InReadBinary ) {
                readBinaryHelper.Finish();
                state = savedState;
            }
            MoveToAttr(nav, depth+1);
            return true;
        }

        public override bool MoveToFirstAttribute() {
            int depth;
            XPathNavigator nav = GetElemNav(out depth);
            if (null != nav) {
                if ( nav.MoveToFirstNamespace( XPathNamespaceScope.Local ) ) {
                    // attributes are in reverse order
                    while ( nav.MoveToNextNamespace( XPathNamespaceScope.Local ) )
                        ;
                    goto FoundMatch;
                }
                if ( nav.MoveToFirstAttribute() ) {
                    goto FoundMatch;
                }
            }
            return false; 
        FoundMatch:
            if ( state == State.InReadBinary ) {
                readBinaryHelper.Finish();
                state = savedState;
            }
            MoveToAttr(nav, depth+1);
            return true;
        }            
        
        public override bool MoveToNextAttribute() {
            switch (this.state) {
                case State.Content:
                    return MoveToFirstAttribute();

                case State.Attribute: {
                    if (XPathNodeType.Attribute == this.nav.NodeType) 
                        return this.nav.MoveToNextAttribute();
                    
                    // otherwise it is on a namespace... namespace are in reverse order
                    Debug.Assert( XPathNodeType.Namespace == this.nav.NodeType );
                    XPathNavigator nav = this.nav.Clone();
                    if ( !nav.MoveToParent() )
                        return false; // shouldn't happen
                    if ( !nav.MoveToFirstNamespace( XPathNamespaceScope.Local ) )
                        return false; // shouldn't happen
                    if ( nav.IsSamePosition( this.nav ) ) {
                        // this was the last one... start walking attributes
                        nav.MoveToParent();
                        if (!nav.MoveToFirstAttribute())
                            return false;
                        // otherwise we are there
                        this.nav.MoveTo(nav);
                        return true;
                    }
                    else {
                        XPathNavigator prev = nav.Clone();
                        for (;;) {
                            if ( !nav.MoveToNextNamespace( XPathNamespaceScope.Local ) ) {
                                Debug.Fail( "Couldn't find Namespace Node! Should not happen!" );
                                return false;
                            }
                            if ( nav.IsSamePosition( this.nav ) ) {
                                this.nav.MoveTo(prev);
                                return true;
                            }
                            prev.MoveTo( nav );
                        }
                        // found previous namespace position
                    }
                }
                case State.AttrVal:
                    depth--;
                    this.state = State.Attribute;
                    if (!MoveToNextAttribute()) {
                        depth++;
                        this.state = State.AttrVal;
                        return false;
                    }
                    this.nodeType = XmlNodeType.Attribute;
                    return true;

                case State.InReadBinary:
                    state = savedState;
                    if (!MoveToNextAttribute()) {
                        state = State.InReadBinary;
                        return false;
                    }
                    readBinaryHelper.Finish();
                    return true;

                default:
                    return false;
            }
        }            

        public override bool MoveToAttribute( string name ) {
            int depth;
            XPathNavigator nav = GetElemNav(out depth);
            if (null == nav)
                return false;

            string prefix, localname;
            ValidateNames.SplitQName( name, out prefix, out localname );

            // watch for a namespace name
            bool IsXmlnsNoPrefix = false;
            if ( ( IsXmlnsNoPrefix = ( 0 == prefix.Length && localname == "xmlns" ) )
                || ( prefix == "xmlns" ) ) {
                if ( IsXmlnsNoPrefix )
                    localname = string.Empty;
                if ( nav.MoveToFirstNamespace(XPathNamespaceScope.Local) ) {
                    do {
                        if (nav.LocalName == localname)
                            goto FoundMatch;
                    } while ( nav.MoveToNextNamespace(XPathNamespaceScope.Local) );
                }
            }
            else if ( 0 == prefix.Length ) {
                // the empty prefix always means empty namespaceUri for attributes
                if ( nav.MoveToAttribute( localname, string.Empty ) )
                    goto FoundMatch;
            }
            else {
                if ( nav.MoveToFirstAttribute() ) {
                    do {
                        if (nav.LocalName == localname && nav.Prefix == prefix)
                            goto FoundMatch;
                    } while (nav.MoveToNextAttribute());
                }
            }
            return false;

        FoundMatch:
            if ( state == State.InReadBinary ) {
                readBinaryHelper.Finish();
                state = savedState;
            }
            MoveToAttr(nav, depth+1);
            return true;
        }

        public override bool MoveToElement() {
            switch (this.state) {
                case State.Attribute:
                case State.AttrVal:
                    if (!nav.MoveToParent())
                        return false;
                    this.depth--;
                    if (this.state == State.AttrVal)
                        this.depth--;
                    this.state = State.Content;
                    this.nodeType = XmlNodeType.Element;
                    return true;
                case State.InReadBinary:
                    state = savedState;
                    if (!MoveToElement()) {
                        state = State.InReadBinary;
                        return false;
                    }
                    readBinaryHelper.Finish();
                    break;
            }
            return false;
        }

        public override bool EOF { 
            get {
                return this.state == State.EOF;
            }
        }        

        public override ReadState ReadState { 
            get {
                switch (this.state) {
                    case State.Initial:
                        return ReadState.Initial;
                    case State.Content:
                    case State.EndElement:
                    case State.Attribute:
                    case State.AttrVal:
                    case State.InReadBinary:
                        return ReadState.Interactive;
                    case State.EOF:
                        return ReadState.EndOfFile;
                    case State.Closed:
                        return ReadState.Closed;
                    default:
                        return ReadState.Error;
                }
            }
        }

        public override void ResolveEntity() {
            throw new InvalidOperationException( Res.GetString( Res.Xml_InvalidOperation ) );
        }

        public override bool ReadAttributeValue() {
            if ( state == State.InReadBinary ) {
                readBinaryHelper.Finish();
                state = savedState;
            }
            if ( this.state == State.Attribute ) {
                this.state = State.AttrVal;
                this.nodeType = XmlNodeType.Text;
                this.depth++;
                return true;
            }
            return false;
        }

        public override bool CanReadBinaryContent {
            get {
                return true;
            }
        }

        public override int ReadContentAsBase64( byte[] buffer, int index, int count ) {
            if ( ReadState != ReadState.Interactive ) {
                return 0;
            }

            // init ReadContentAsBinaryHelper when called first time
            if ( state != State.InReadBinary ) {
                readBinaryHelper = ReadContentAsBinaryHelper.CreateOrReset( readBinaryHelper, this );
                savedState = state;
            }

            // turn off InReadBinary state in order to have a normal Read() behavior when called from readBinaryHelper
            state = savedState;

            // call to the helper
            int readCount = readBinaryHelper.ReadContentAsBase64( buffer, index, count );

            // turn on InReadBinary state again and return
            savedState = state;
            state = State.InReadBinary;
            return readCount;
        }

        public override int ReadContentAsBinHex( byte[] buffer, int index, int count ) {
            if ( ReadState != ReadState.Interactive ) {
                return 0;
            }

            // init ReadContentAsBinaryHelper when called first time
            if ( state != State.InReadBinary ) {
                readBinaryHelper = ReadContentAsBinaryHelper.CreateOrReset( readBinaryHelper, this );
                savedState = state;
            }

            // turn off InReadBinary state in order to have a normal Read() behavior when called from readBinaryHelper
            state = savedState;

            // call to the helper
            int readCount = readBinaryHelper.ReadContentAsBinHex( buffer, index, count );

            // turn on InReadBinary state again and return
            savedState = state;
            state = State.InReadBinary;
            return readCount;
        }

        public override int ReadElementContentAsBase64( byte[] buffer, int index, int count ) {
            if ( ReadState != ReadState.Interactive ) {
                return 0;
            }

            // init ReadContentAsBinaryHelper when called first time
            if ( state != State.InReadBinary ) {
                readBinaryHelper = ReadContentAsBinaryHelper.CreateOrReset( readBinaryHelper, this );
                savedState = state;
            }

            // turn off InReadBinary state in order to have a normal Read() behavior when called from readBinaryHelper
            state = savedState;

            // call to the helper
            int readCount = readBinaryHelper.ReadElementContentAsBase64( buffer, index, count );

            // turn on InReadBinary state again and return
            savedState = state;
            state = State.InReadBinary;
            return readCount;
        }

        public override int ReadElementContentAsBinHex( byte[] buffer, int index, int count ) {
            if ( ReadState != ReadState.Interactive ) {
                return 0;
            }

            // init ReadContentAsBinaryHelper when called first time
            if ( state != State.InReadBinary ) {
                readBinaryHelper = ReadContentAsBinaryHelper.CreateOrReset( readBinaryHelper, this );
                savedState = state;
            }

            // turn off InReadBinary state in order to have a normal Read() behavior when called from readBinaryHelper
            state = savedState;

            // call to the helper
            int readCount = readBinaryHelper.ReadElementContentAsBinHex( buffer, index, count );

            // turn on InReadBinary state again and return
            savedState = state;
            state = State.InReadBinary;
            return readCount;
        }

        public override string LookupNamespace( string prefix ) {
            return this.nav.LookupNamespace( prefix );
        }
        
        /// <summary>
        /// Current depth in subtree.
        /// </summary>
        public override int Depth {
            get { return this.depth; }
        }

        /// <summary>
        /// Move to the next reader state.  Return false if that is ReaderState.Closed.
        /// </summary>
        public override bool Read() {
            this.attrCount = -1;
            switch (this.state) {
                case State.Error:
                case State.Closed:
                case State.EOF:
                    return false;

                case State.Initial:
                    // Starting state depends on the navigator's item type
                    this.nav = this.navToRead;
                    this.state = State.Content;
                    if ( XPathNodeType.Root == this.nav.NodeType ) {
                        if( !nav.MoveToFirstChild() ) {
                            SetEOF();
                            return false;
                        }
                        this.readEntireDocument = true;
                    }
                    else if ( XPathNodeType.Attribute == this.nav.NodeType ) {
                        this.state = State.Attribute;
                    }
                    this.nodeType = ToXmlNodeType( this.nav.NodeType );
                    break;

                case State.Content:
                    if ( this.nav.MoveToFirstChild() ) {
                        this.nodeType = ToXmlNodeType( this.nav.NodeType );
                        this.depth++;
                        this.state = State.Content;
                    }
                    else if ( this.nodeType == XmlNodeType.Element 
                        && !this.nav.IsEmptyElement ) {
                        this.nodeType = XmlNodeType.EndElement;
                        this.state = State.EndElement;
                    }
                    else
                        goto case State.EndElement;
                    break;

                case State.EndElement:
                    if ( 0 == depth && !this.readEntireDocument ) {
                        SetEOF();
                        return false;
                    }
                    else if ( this.nav.MoveToNext() ) {
                        this.nodeType = ToXmlNodeType( this.nav.NodeType );
                        this.state = State.Content;
                    }
                    else if ( depth > 0 && this.nav.MoveToParent() ) {
                        Debug.Assert( this.nav.NodeType == XPathNodeType.Element, this.nav.NodeType.ToString() + " == XPathNodeType.Element" );
                        this.nodeType = XmlNodeType.EndElement;
                        this.state = State.EndElement;
                        depth--;
                    }
                    else {
                        SetEOF();
                        return false;
                    }
                    break;

                case State.Attribute:
                case State.AttrVal:
                    if ( !this.nav.MoveToParent() ) {
                        SetEOF();
                        return false;
                    }
                    this.nodeType = ToXmlNodeType( this.nav.NodeType );
                    this.depth--;
                    if (state == State.AttrVal)
                        this.depth--;
                    goto case State.Content;
                case State.InReadBinary:
                    state = savedState;
                    readBinaryHelper.Finish();
                    return Read();
            }
            return true;
        }


        /// <summary>
        /// End reading by transitioning into the Closed state.
        /// </summary>
        public override void Close() {
            this.nav = XmlEmptyNavigator.Singleton;
            this.nodeType = XmlNodeType.None;
            this.state = State.Closed;
            this.depth = 0;
        }

        /// <summary>
        /// set reader to EOF state
        /// </summary>
        private void SetEOF() {
            this.nav = XmlEmptyNavigator.Singleton;
            this.nodeType = XmlNodeType.None;
            this.state = State.EOF;
            this.depth = 0;
        }
    }

#if NAVREADER_SUPPORTSLINEINFO
    internal class XPathNavigatorReaderWithLI : XPathNavigatorReader, System.Xml.IXmlLineInfo {
        internal XPathNavigatorReaderWithLI( XPathNavigator navToRead, IXmlLineInfo xli, IXmlSchemaInfo xsi ) 
            : base( navToRead, xli, xsi ) {
        }

        //-----------------------------------------------
        // IXmlLineInfo
        //-----------------------------------------------

        public virtual bool HasLineInfo() { return IsReading ? this.lineInfo.HasLineInfo() : false; }
        public virtual int LineNumber { get { return IsReading ? this.lineInfo.LineNumber : 0; } }
        public virtual int LinePosition { get { return IsReading ? this.lineInfo.LinePosition : 0; } }
    }

    internal class XPathNavigatorReaderWithLIAndSI : XPathNavigatorReaderWithLI, System.Xml.IXmlLineInfo, System.Xml.Schema.IXmlSchemaInfo {
        internal XPathNavigatorReaderWithLIAndSI( XPathNavigator navToRead, IXmlLineInfo xli, IXmlSchemaInfo xsi ) 
            : base( navToRead, xli, xsi ) {
        }

        //-----------------------------------------------
        // IXmlSchemaInfo
        //-----------------------------------------------

        public virtual XmlSchemaValidity Validity { get { return IsReading ? this.schemaInfo.Validity : XmlSchemaValidity.NotKnown; } }
        public override bool IsDefault { get { return IsReading ? this.schemaInfo.IsDefault : false; } }
        public virtual bool IsNil { get { return IsReading ? this.schemaInfo.IsNil : false; } }
        public virtual XmlSchemaSimpleType MemberType { get { return IsReading ? this.schemaInfo.MemberType : null; } }
        public virtual XmlSchemaType SchemaType { get { return IsReading ? this.schemaInfo.SchemaType : null; } }
        public virtual XmlSchemaElement SchemaElement { get { return IsReading ? this.schemaInfo.SchemaElement : null; } }
        public virtual XmlSchemaAttribute SchemaAttribute { get { return IsReading ? this.schemaInfo.SchemaAttribute : null; } }
    }
#endif

    internal class XPathNavigatorReaderWithSI : XPathNavigatorReader, System.Xml.Schema.IXmlSchemaInfo {
        internal XPathNavigatorReaderWithSI( XPathNavigator navToRead, IXmlLineInfo xli, IXmlSchemaInfo xsi ) 
            : base( navToRead, xli, xsi ) {
        }

        //-----------------------------------------------
        // IXmlSchemaInfo
        //-----------------------------------------------

        public virtual XmlSchemaValidity Validity { get { return IsReading ? this.schemaInfo.Validity : XmlSchemaValidity.NotKnown; } }
        public override bool IsDefault { get { return IsReading ? this.schemaInfo.IsDefault : false; } }
        public virtual bool IsNil { get { return IsReading ? this.schemaInfo.IsNil : false; } }
        public virtual XmlSchemaSimpleType MemberType { get { return IsReading ? this.schemaInfo.MemberType : null; } }
        public virtual XmlSchemaType SchemaType { get { return IsReading ? this.schemaInfo.SchemaType : null; } }
        public virtual XmlSchemaElement SchemaElement { get { return IsReading ? this.schemaInfo.SchemaElement : null; } }
        public virtual XmlSchemaAttribute SchemaAttribute { get { return IsReading ? this.schemaInfo.SchemaAttribute : null; } }
    }

    /// <summary>
    /// The XmlEmptyNavigator exposes a document node with no children.
    /// Only one XmlEmptyNavigator exists per AppDomain (Singleton).  That's why the constructor is private.
    /// Use the Singleton property to get the EmptyNavigator.
    /// </summary>
    internal class XmlEmptyNavigator : XPathNavigator {
        private static volatile XmlEmptyNavigator singleton;

        private XmlEmptyNavigator() {
        }

        public static XmlEmptyNavigator Singleton {
            get {
                if (XmlEmptyNavigator.singleton == null)
                    XmlEmptyNavigator.singleton = new XmlEmptyNavigator();
                return XmlEmptyNavigator.singleton;
            }
        }

        //-----------------------------------------------
        // XmlReader
        //-----------------------------------------------

        public override XPathNodeType NodeType {
            get { return XPathNodeType.All; }
        }

        public override string NamespaceURI {
            get { return string.Empty; }
        }

        public override string LocalName {
            get { return string.Empty; }
        }

        public override string Name {
            get { return string.Empty; }
        }

        public override string Prefix {
            get { return string.Empty; }
        }

        public override string BaseURI {
            get { return string.Empty; }
        }

        public override string Value {
            get { return string.Empty; }
        }

        public override bool IsEmptyElement {
            get { return false; }
        }

        public override string XmlLang { 
            get { return string.Empty; }
        }        

        public override bool HasAttributes {
            get { return false; }
        }

        public override bool HasChildren {
            get { return false; }
        }
        
        
        //-----------------------------------------------
        // IXmlNamespaceResolver
        //-----------------------------------------------

        public override XmlNameTable NameTable {
            get { return new NameTable(); }
        }

        public override bool MoveToFirstChild() {
            return false;
        }

        public override void MoveToRoot() {
            //always on root
            return;
        }        

        public override bool MoveToNext() {
            return false;
        }

        public override bool MoveToPrevious() {
            return false;
        }
        
        public override bool MoveToFirst() {
            return false;
        }

        public override bool MoveToFirstAttribute() {
            return false;
        }

        public override bool MoveToNextAttribute() {
            return false;
        }

        public override bool MoveToId(string id) {
            return false;
        }

        public override string GetAttribute(string localName, string namespaceName) {
            return null;
        }

        public override bool MoveToAttribute(string localName, string namespaceName) {
            return false;
        }

        public override string GetNamespace( string name ) {
            return null;
        }

        public override bool MoveToNamespace( string prefix ) {
            return false;
        }
        
        
        public override bool MoveToFirstNamespace(XPathNamespaceScope scope) {
            return false;
        }

        public override bool MoveToNextNamespace(XPathNamespaceScope scope) {
            return false;
        }

        public override bool MoveToParent() {
            return false;
        }

        public override bool MoveTo(XPathNavigator other) {
            // Only one instance of XmlEmptyNavigator exists on the system
            return (object) this == (object) other;
        }

        public override XmlNodeOrder ComparePosition(XPathNavigator other) {
            // Only one instance of XmlEmptyNavigator exists on the system
            return ((object) this == (object) other) ? XmlNodeOrder.Same : XmlNodeOrder.Unknown;
        }
        
        public override bool IsSamePosition(XPathNavigator other) {
            // Only one instance of XmlEmptyNavigator exists on the system
            return (object) this == (object) other;
        }


        //-----------------------------------------------
        // XPathNavigator2
        //-----------------------------------------------
        public override XPathNavigator Clone() {
            // Singleton, so clone just returns this
            return this;
        }
    }
}