//
// System.Xml.Schema.XmlSchema.cs
//
// Author:
//	Dwivedi, Ajay kumar  Adwiv@Yahoo.com
//	Atsushi Enomoto  ginga@kit.hi-ho.ne.jp
//
using System;
using System.Collections;
using System.Xml;
using System.IO;
using System.Xml.Serialization;
using System.ComponentModel;

namespace System.Xml.Schema
{
        /// <summary>
        /// Summary description for XmlSchema.
        /// </summary>
        [XmlRoot("schema",Namespace=XmlSchema.Namespace)]
        public class XmlSchema : XmlSchemaObject
        {
                //public constants
                public const string Namespace = "http://www.w3.org/2001/XMLSchema";
                public const string InstanceNamespace = "http://www.w3.org/2001/XMLSchema-instance";

                //private fields
                private XmlSchemaForm attributeFormDefault ;
                private XmlSchemaObjectTable attributeGroups ;
                private XmlSchemaObjectTable attributes ;
                private XmlSchemaDerivationMethod blockDefault ;
                private XmlSchemaForm elementFormDefault ;
                private XmlSchemaObjectTable elements ;
                private XmlSchemaDerivationMethod finalDefault ;
                private XmlSchemaObjectTable groups ;
                private string id ;
                private XmlSchemaObjectCollection includes ;
                private XmlSchemaObjectCollection items ;
                private XmlSchemaObjectTable notations ;
                private XmlSchemaObjectTable schemaTypes ;
                private string targetNamespace ;
                private XmlAttribute[] unhandledAttributes ;
                private string version;
                private string language;

		// other post schema compilation infoset
		private Hashtable idCollection;
		private XmlSchemaObjectTable namedIdentities;
		private XmlSchemaCollection schemas;

		private XmlNameTable nameTable;

		internal bool missedSubComponents;

                // Compiler specific things
                private static string xmlname = "schema";

                public XmlSchema()
                {
                        attributeFormDefault= XmlSchemaForm.None;
                        blockDefault            = XmlSchemaDerivationMethod.None;
                        elementFormDefault      = XmlSchemaForm.None;
                        finalDefault            = XmlSchemaDerivationMethod.None;
                        includes                        = new XmlSchemaObjectCollection();
                        isCompiled                      = false;
                        items                           = new XmlSchemaObjectCollection();
                        attributeGroups         = new XmlSchemaObjectTable();
                        attributes                      = new XmlSchemaObjectTable();
                        elements                        = new XmlSchemaObjectTable();
                        groups                          = new XmlSchemaObjectTable();
                        notations                       = new XmlSchemaObjectTable();
                        schemaTypes                     = new XmlSchemaObjectTable();
			idCollection                    = new Hashtable ();
                        namedIdentities                 = new XmlSchemaObjectTable();
                }

                #region Properties

                [DefaultValue(XmlSchemaForm.None)]
                [System.Xml.Serialization.XmlAttribute("attributeFormDefault")]
                public XmlSchemaForm AttributeFormDefault
                {
                        get{ return attributeFormDefault; }
                        set{ this.attributeFormDefault = value;}
                }

                [DefaultValue(XmlSchemaDerivationMethod.None)]
                [System.Xml.Serialization.XmlAttribute("blockDefault")]
                public XmlSchemaDerivationMethod BlockDefault
                {
                        get{ return blockDefault;}
                        set{ blockDefault = value;}
                }

                [DefaultValue(XmlSchemaDerivationMethod.None)]
                [System.Xml.Serialization.XmlAttribute("finalDefault")]
                public XmlSchemaDerivationMethod FinalDefault
                {
                        get{ return finalDefault;}
                        set{ finalDefault = value;}
                }

                [DefaultValue(XmlSchemaForm.None)]
                [System.Xml.Serialization.XmlAttribute("elementFormDefault")]
                public XmlSchemaForm ElementFormDefault
                {
                        get{ return elementFormDefault;}
                        set{ elementFormDefault = value;}
                }

                [System.Xml.Serialization.XmlAttribute("targetNamespace")]
                public string TargetNamespace
                {
                        get{ return targetNamespace;}
                        set{ targetNamespace = value;}
                }

                [System.Xml.Serialization.XmlAttribute("version")]
                public string Version
                {
                        get{ return version;}
                        set{ version = value;}
                }

                [XmlElement("include",typeof(XmlSchemaInclude),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("import",typeof(XmlSchemaImport),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("redefine",typeof(XmlSchemaRedefine),Namespace="http://www.w3.org/2001/XMLSchema")]
                public XmlSchemaObjectCollection Includes
                {
                        get{ return includes;}
                }

                [XmlElement("simpleType",typeof(XmlSchemaSimpleType),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("complexType",typeof(XmlSchemaComplexType),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("group",typeof(XmlSchemaGroup),Namespace="http://www.w3.org/2001/XMLSchema")]
                        //Only Schema's attributeGroup has type XmlSchemaAttributeGroup.
                        //Others (complextype, restrictions etc) must have XmlSchemaAttributeGroupRef
                [XmlElement("attributeGroup",typeof(XmlSchemaAttributeGroup),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("element",typeof(XmlSchemaElement),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("attribute",typeof(XmlSchemaAttribute),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("notation",typeof(XmlSchemaNotation),Namespace="http://www.w3.org/2001/XMLSchema")]
                [XmlElement("annotation",typeof(XmlSchemaAnnotation),Namespace="http://www.w3.org/2001/XMLSchema")]
                public XmlSchemaObjectCollection Items
                {
                        get{ return items;}
                }

                [XmlIgnore]
                public bool IsCompiled
                {
                        get{ return this.CompilationId != Guid.Empty;}
                }

                [XmlIgnore]
                public XmlSchemaObjectTable Attributes
                {
                        get{ return attributes;}
                }

                [XmlIgnore]
                public XmlSchemaObjectTable AttributeGroups
                {
                        get{ return attributeGroups; }
                }

                [XmlIgnore]
                public XmlSchemaObjectTable SchemaTypes
                {
                        get{ return schemaTypes; }
                }

                [XmlIgnore]
                public XmlSchemaObjectTable Elements
                {
                        get{ return elements;}
                }

                [System.Xml.Serialization.XmlAttribute("id")]
                public string Id
                {
                        get{ return id;}
                        set{ id = value;}
                }

                [XmlAnyAttribute]
                public XmlAttribute[] UnhandledAttributes
                {
                        get
                        {
                                if(unhandledAttributeList != null)
                                {
                                        unhandledAttributes = (XmlAttribute[]) unhandledAttributeList.ToArray(typeof(XmlAttribute));
                                        unhandledAttributeList = null;
                                }
                                return unhandledAttributes;
                        }
                        set
                        {
                                unhandledAttributes = value;
                                unhandledAttributeList = null;
                        }
                }

                [XmlIgnore]
                public XmlSchemaObjectTable Groups
                {
                        get{ return groups;}
                }

                [XmlIgnore]
                public XmlSchemaObjectTable Notations
                {
                        get{ return notations;}
                }

                // New attribute defined in W3C schema element
                [System.Xml.Serialization.XmlAttribute("xml:lang")]
                public string Language
                {
                        get{ return  language; }
                        set{ language = value; }
                }

		internal Hashtable IDCollection
		{
			get { return idCollection; }
		}

		internal XmlSchemaObjectTable NamedIdentities
		{
			get { return namedIdentities; }
		}

		internal XmlSchemaCollection Schemas
		{
			get { return schemas; }
		}
                #endregion

                #region Compile

                // Methods
                /// <summary>
                /// This compile method does two things:
                /// 1. It compiles and fills the PSVI dataset
                /// 2. Validates the schema by calling Validate method.
                /// Every XmlSchemaObject has a Compile Method which gets called.
                /// </summary>
                /// <remarks>
                ///             1. blockDefault must be one of #all | List of (extension | restriction | substitution)
                ///             2. finalDefault must be one of (#all | List of (extension | restriction| union| list))
                ///             3. id must be of type ID
                ///             4. targetNamespace should be any uri
                ///             5. version should be a normalizedString
                ///             6. xml:lang should be a language
                /// </remarks>
                public void Compile (ValidationEventHandler handler)
		{
			Compile (handler, new XmlUrlResolver ());
		}

#if NET_1_0
                internal void Compile (ValidationEventHandler handler, XmlResolver resolver)
#else
                public void Compile (ValidationEventHandler handler, XmlResolver resolver)
#endif
		{
			Compile (handler, new Stack (), this, null, resolver);
			isCompiled = true;
		}

		internal void Compile (ValidationEventHandler handler, XmlSchemaCollection col, XmlResolver resolver)
		{
			Compile (handler, new Stack (), this, col, resolver);
		}

		private void Compile (ValidationEventHandler handler, Stack schemaLocationStack, XmlSchema rootSchema, XmlSchemaCollection col, XmlResolver resolver)
                {
			if (rootSchema != this) {
				CompilationId = rootSchema.CompilationId;
				schemas = rootSchema.schemas;
			}
			else {
				schemas = col;
				if (schemas == null) {
					schemas = new XmlSchemaCollection ();
					schemas.SchemaSet.CompilationId = Guid.NewGuid ();
				}
				CompilationId = schemas.SchemaSet.CompilationId;
				this.idCollection.Clear ();
			}
			schemas.Add (this);

			attributeGroups.Clear ();
			attributes.Clear ();
			elements.Clear ();
			groups.Clear ();
			notations.Clear ();
			schemaTypes.Clear ();

			//1. Union and List are not allowed in block default
                        if(BlockDefault != XmlSchemaDerivationMethod.All)
                        {
                                if((BlockDefault & XmlSchemaDerivationMethod.List)!=0 )
                                        error(handler, "list is not allowed in blockDefault attribute");
                                if((BlockDefault & XmlSchemaDerivationMethod.Union)!=0 )
                                        error(handler, "union is not allowed in blockDefault attribute");
                        }

                        //2. Substitution is not allowed in finaldefault.
                        if(FinalDefault != XmlSchemaDerivationMethod.All)
                        {
                                if((FinalDefault & XmlSchemaDerivationMethod.Substitution)!=0 )
                                        error(handler, "substitution is not allowed in finalDefault attribute");
                        }

                        //3. id must be of type ID
                        XmlSchemaUtil.CompileID(Id, this, this.IDCollection, handler);

                        //4. targetNamespace should be of type anyURI or absent
                        if(TargetNamespace != null)
                        {
                                if(!XmlSchemaUtil.CheckAnyUri(TargetNamespace))
                                        error(handler, TargetNamespace+" is not a valid value for targetNamespace attribute of schema");
                        }

                        //5. version should be of type normalizedString
                        if(!XmlSchemaUtil.CheckNormalizedString(Version))
                                error(handler, Version + "is not a valid value for version attribute of schema");

                        //6. xml:lang must be a language
                        if(!XmlSchemaUtil.CheckLanguage(Language))
                                error(handler, Language + " is not a valid language");

                        // Compile the content of this schema

			XmlSchemaObjectCollection compilationItems = new XmlSchemaObjectCollection ();
			foreach (XmlSchemaObject obj in Items)
				compilationItems.Add (obj);

			// First, we run into inclusion schemas to collect 
			// compilation target items into compiledItems.
                        foreach(XmlSchemaObject obj in Includes)
                        {
				XmlSchemaExternal ext = obj as XmlSchemaExternal;
                                if(ext != null)
                                {
					if (ext.SchemaLocation == null) 
						continue;
					Stream stream = null;
					string url = null;
					if (resolver != null) {
						url = GetResolvedUri (resolver, ext.SchemaLocation);
						if (schemaLocationStack.Contains (url)) {
							error(handler, "Nested inclusion was found: " + url);
							// must skip this inclusion
							continue;
						}
						try {
							stream = resolver.GetEntity (new Uri (url), null, typeof (Stream)) as Stream;
						} catch (Exception) {
						// LAMESPEC: This is not good way to handle errors, but since we cannot know what kind of XmlResolver will come, so there are no mean to avoid this ugly catch.
							stream = null;
						}
					}

					// Process redefinition children in advance.
					XmlSchemaRedefine redefine = obj as XmlSchemaRedefine;
					if (redefine != null) {
						foreach (XmlSchemaObject redefinedObj in redefine.Items) {
							redefinedObj.isRedefinedComponent = true;
							redefinedObj.isRedefineChild = true;
							if (redefinedObj is XmlSchemaType ||
								redefinedObj is XmlSchemaGroup ||
								redefinedObj is XmlSchemaAttributeGroup)
								compilationItems.Add (redefinedObj);
							else
								error (handler, "Redefinition is only allowed to simpleType, complexType, group and attributeGroup.");
						}
					}

					XmlSchema includedSchema = null;
					if (stream == null) {
						// It is missing schema components.
						missedSubComponents = true;
						continue;
					} else {
						schemaLocationStack.Push (url);
						includedSchema = XmlSchema.Read (new XmlTextReader (url, stream, nameTable), handler);
						includedSchema.schemas = schemas;
					}

					// Set - actual - target namespace for the included schema * before compilation*.
					XmlSchemaImport import = ext as XmlSchemaImport;
					if (import != null) {
						if (TargetNamespace == includedSchema.TargetNamespace) {
							error (handler, "Target namespace must be different from that of included schema.");
							continue;
						} else if (includedSchema.TargetNamespace != import.Namespace) {
							error (handler, "Attribute namespace and its importing schema's target namespace must be the same.");
							continue;
						}
					} else {
						if (TargetNamespace == null && 
							includedSchema.TargetNamespace != null) {
							error (handler, "Target namespace is required to include a schema which has its own target namespace");
							continue;
						}
						else if (TargetNamespace != null && 
							includedSchema.TargetNamespace == null)
							includedSchema.TargetNamespace = TargetNamespace;
					}

					// Compile included schema.
					includedSchema.idCollection = this.IDCollection;
					includedSchema.Compile (handler, schemaLocationStack, rootSchema, col, resolver);
					schemaLocationStack.Pop ();

					if (import != null)
						rootSchema.schemas.Add (includedSchema);

					// Add compiled items.
					foreach (XmlSchemaObject includedObj in includedSchema.Items)
						compilationItems.Add (includedObj);
                                }
                                else
                                {
                                        error(handler,"Object of Type "+obj.GetType().Name+" is not valid in Includes Property of XmlSchema");
                                }
                        }

			// Compilation phase.
			// At least each Compile() must gives unique (qualified) name for each component.
			// It also checks self-resolvable properties correct.
			// Post compilation schema information contribution is not required here.
			// It should be done by Validate().
			foreach(XmlSchemaObject obj in compilationItems)
                        {
                                if(obj is XmlSchemaAnnotation)
                                {
                                        int numerr = ((XmlSchemaAnnotation)obj).Compile(handler, this);
                                        errorCount += numerr;
                                        if( numerr == 0)
                                        {
                                                //FIXME: What PSVI set do we add this to?
                                        }
                                }
                                else if(obj is XmlSchemaAttribute)
                                {
                                        XmlSchemaAttribute attr = (XmlSchemaAttribute) obj;
                                        attr.ParentIsSchema = true;
                                        int numerr = attr.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
						if (!attr.IsComplied (this.CompilationId))
							schemas.SchemaSet.GlobalAttributes.Add (attr.QualifiedName, attr);
                                                XmlSchemaUtil.AddToTable (Attributes, attr, attr.QualifiedName, handler);
                                        }
                                }
                                else if(obj is XmlSchemaAttributeGroup)
                                {
                                        XmlSchemaAttributeGroup attrgrp = (XmlSchemaAttributeGroup) obj;
                                        int numerr = attrgrp.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
                                                XmlSchemaUtil.AddToTable (AttributeGroups, attrgrp, attrgrp.QualifiedName, handler);
                                        }
                                }
                                else if(obj is XmlSchemaComplexType)
                                {
                                        XmlSchemaComplexType ctype = (XmlSchemaComplexType) obj;
                                        ctype.ParentIsSchema = true;
                                        int numerr = ctype.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
						if (!ctype.IsComplied (this.CompilationId))
	                                                schemas.SchemaSet.GlobalTypes.Add (ctype.QualifiedName, ctype);
                                                XmlSchemaUtil.AddToTable (schemaTypes, ctype, ctype.QualifiedName, handler);
                                        }
                                }
                                else if(obj is XmlSchemaSimpleType)
                                {
                                        XmlSchemaSimpleType stype = (XmlSchemaSimpleType) obj;
                                        stype.islocal = false; //This simple type is toplevel
                                        int numerr = stype.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
						if (!stype.IsComplied (this.CompilationId))
	                                                schemas.SchemaSet.GlobalTypes.Add (stype.QualifiedName, stype);
                                                XmlSchemaUtil.AddToTable (SchemaTypes, stype, stype.QualifiedName, handler);
                                        }
                                }
                                else if(obj is XmlSchemaElement)
                                {
                                        XmlSchemaElement elem = (XmlSchemaElement) obj;
                                        elem.parentIsSchema = true;
                                        int numerr = elem.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
						if (!elem.IsComplied (this.CompilationId))
							schemas.SchemaSet.GlobalElements.Add (elem.QualifiedName, elem);
                                                XmlSchemaUtil.AddToTable (Elements, elem, elem.QualifiedName, handler);
                                        }
                                }
                                else if(obj is XmlSchemaGroup)
                                {
                                        XmlSchemaGroup grp = (XmlSchemaGroup) obj;
                                        int numerr = grp.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
                                                XmlSchemaUtil.AddToTable (Groups, grp, grp.QualifiedName, handler);
                                        }
                                }
                                else if(obj is XmlSchemaNotation)
                                {
                                        XmlSchemaNotation ntn = (XmlSchemaNotation) obj;
                                        int numerr = ntn.Compile(handler, this);
                                        errorCount += numerr;
                                        if(numerr == 0)
                                        {
                                                XmlSchemaUtil.AddToTable (Notations, ntn, ntn.QualifiedName, handler);
                                        }
                                }
                                else
                                {
                                        ValidationHandler.RaiseValidationEvent (
						handler, null,
                                                "Object of Type "+obj.GetType().Name+" is not valid in Item Property of Schema",
						null, this, null, XmlSeverityType.Error);
                                }
                        }

			if (rootSchema == this)
				Validate(handler);
		}

		private string GetResolvedUri (XmlResolver resolver, string relativeUri)
		{
			Uri baseUri = null;
			if (this.SourceUri != null && this.SourceUri != String.Empty)
				baseUri = new Uri (this.SourceUri);
			return resolver.ResolveUri (baseUri, relativeUri).ToString ();
		}

		internal bool IsNamespaceAbsent (string ns)
		{
			return this.schemas [ns] == null;
		}

                #endregion

                private void Validate(ValidationEventHandler handler)
                {
			ValidationId = CompilationId;

                        foreach(XmlSchemaAttribute attr in Attributes.Values)
                        {
                                errorCount += attr.Validate(handler, this);
                        }
                        foreach(XmlSchemaAttributeGroup attrgrp in AttributeGroups.Values)
                        {
                                errorCount += attrgrp.Validate(handler, this);
                        }
                        foreach(XmlSchemaType type in SchemaTypes.Values)
                        {
                                errorCount += type.Validate(handler, this);
                        }
                        foreach(XmlSchemaElement elem in Elements.Values)
                        {
                                errorCount += elem.Validate(handler, this);
                        }
                        foreach(XmlSchemaGroup grp in Groups.Values)
                        {
                                errorCount += grp.Validate(handler, this);
                        }
                        foreach(XmlSchemaNotation ntn in Notations.Values)
                        {
                                errorCount += ntn.Validate(handler, this);
                        }
                }

                #region Read

		// We cannot use xml deserialization, since it does not provide line info, qname context, and so on.
                public static XmlSchema Read (TextReader reader, ValidationEventHandler validationEventHandler)
                {
                        return Read (new XmlTextReader (reader),validationEventHandler);
                }
                public static XmlSchema Read (Stream stream, ValidationEventHandler validationEventHandler)
                {
                        return Read (new XmlTextReader (stream),validationEventHandler);
                }

                public static XmlSchema Read (XmlReader rdr, ValidationEventHandler validationEventHandler)
                {
			XmlSchemaReader reader = new XmlSchemaReader (rdr, validationEventHandler);

			if (reader.ReadState == ReadState.Initial)
				reader.ReadNextElement ();

			int startDepth = reader.Depth;

			do
                        {
                                switch(reader.NodeType)
                                {
                                case XmlNodeType.Element:
					if(reader.LocalName == "schema")
					{
						XmlSchema schema = new XmlSchema ();
						schema.nameTable = rdr.NameTable;

						schema.LineNumber = reader.LineNumber;
						schema.LinePosition = reader.LinePosition;
						schema.SourceUri = reader.BaseURI;

						ReadAttributes(schema, reader, validationEventHandler);
						//IsEmptyElement does not behave properly if reader is
						//positioned at an attribute.
						reader.MoveToElement();
						if(!reader.IsEmptyElement)
						{
							ReadContent(schema, reader, validationEventHandler);
						}
						else
							rdr.Skip ();

						if (rdr.NodeType == XmlNodeType.EndElement)
							rdr.Read ();
						return schema;
					}
					else
						//Schema can't be generated. Throw an exception
						error (validationEventHandler, "The root element must be schema", null);
					break;
                                default:
					error(validationEventHandler, "This should never happen. XmlSchema.Read 1 ",null);
					break;
                                }
                        } while(reader.Depth > startDepth && reader.ReadNextElement());

			// This is thrown regardless of ValidationEventHandler existence.
			throw new XmlSchemaException ("The top level schema must have namespace " + XmlSchema.Namespace, null);
                }

		private static void ReadAttributes(XmlSchema schema, XmlSchemaReader reader, ValidationEventHandler h)
                {
                        Exception ex;

                        reader.MoveToElement();
                        while(reader.MoveToNextAttribute())
                        {
                                switch(reader.Name)
                                {
                                        case "attributeFormDefault" :
                                                schema.attributeFormDefault = XmlSchemaUtil.ReadFormAttribute(reader,out ex);
                                                if(ex != null)
                                                        error(h, reader.Value + " is not a valid value for attributeFormDefault.", ex);
                                                break;
                                        case "blockDefault" :
                                                schema.blockDefault = XmlSchemaUtil.ReadDerivationAttribute(reader,out ex, "blockDefault",
							XmlSchemaUtil.ElementBlockAllowed);
                                                if(ex != null)
                                                        error (h, ex.Message, ex);
                                                break;
                                        case "elementFormDefault":
                                                schema.elementFormDefault = XmlSchemaUtil.ReadFormAttribute(reader, out ex);
                                                if(ex != null)
                                                        error(h, reader.Value + " is not a valid value for elementFormDefault.", ex);
                                                break;
                                        case "finalDefault":
                                                schema.finalDefault = XmlSchemaUtil.ReadDerivationAttribute(reader, out ex, "finalDefault",
							XmlSchemaUtil.FinalAllowed);
                                                if(ex != null)
                                                        error (h, ex.Message , ex);
                                                break;
                                        case "id":
                                                schema.id = reader.Value;
                                                break;
                                        case "targetNamespace":
                                                schema.targetNamespace = reader.Value;
                                                break;
                                        case "version":
                                                schema.version = reader.Value;
                                                break;
                                        case "xml:lang":
                                                schema.language = reader.Value;
                                                break;
                                        default:
                                                if((reader.NamespaceURI == "" && reader.Name != "xmlns") || reader.NamespaceURI == XmlSchema.Namespace)
                                                        error(h, reader.Name + " attribute is not allowed in schema element",null);
                                                else
                                                {
                                                        XmlSchemaUtil.ReadUnhandledAttribute(reader,schema);
                                                }
                                                break;
                                }
                        }
                }

                private static void ReadContent(XmlSchema schema, XmlSchemaReader reader, ValidationEventHandler h)
                {
                        reader.MoveToElement();
                        if(reader.LocalName != "schema" && reader.NamespaceURI != XmlSchema.Namespace && reader.NodeType != XmlNodeType.Element)
                                error(h, "UNREACHABLE CODE REACHED: Method: Schema.ReadContent, " + reader.LocalName + ", " + reader.NamespaceURI,null);

                        //(include | import | redefine | annotation)*,
                        //((simpleType | complexType | group | attributeGroup | element | attribute | notation | annotation)*
                        int level = 1;
                        while(reader.ReadNextElement())
                        {
                                if(reader.NodeType == XmlNodeType.EndElement)
                                {
                                        if(reader.LocalName != xmlname)
                                                error(h,"Should not happen :2: XmlSchema.Read, name="+reader.Name,null);
                                        break;
                                }
                                if(level <= 1)
                                {
                                        if(reader.LocalName == "include")
                                        {
                                                XmlSchemaInclude include = XmlSchemaInclude.Read(reader,h);
                                                if(include != null)
                                                        schema.includes.Add(include);
                                                continue;
                                        }
                                        if(reader.LocalName == "import")
                                        {
                                                XmlSchemaImport import = XmlSchemaImport.Read(reader,h);
                                                if(import != null)
                                                        schema.includes.Add(import);
                                                continue;
                                        }
                                        if(reader.LocalName == "redefine")
                                        {
                                                XmlSchemaRedefine redefine = XmlSchemaRedefine.Read(reader,h);
                                                if(redefine != null)
                                                        schema.includes.Add(redefine);
                                                continue;
                                        }
                                        if(reader.LocalName == "annotation")
                                        {
                                                XmlSchemaAnnotation annotation = XmlSchemaAnnotation.Read(reader,h);
                                                if(annotation != null)
                                                        schema.items.Add(annotation);
                                                continue;
                                        }
                                }
                                if(level <=2)
                                {
                                        level = 2;
                                        if(reader.LocalName == "simpleType")
                                        {
                                                XmlSchemaSimpleType stype = XmlSchemaSimpleType.Read(reader,h);
                                                if(stype != null)
                                                        schema.items.Add(stype);
                                                continue;
                                        }
                                        if(reader.LocalName == "complexType")
                                        {
                                                XmlSchemaComplexType ctype = XmlSchemaComplexType.Read(reader,h);
                                                if(ctype != null)
                                                        schema.items.Add(ctype);
                                                continue;
                                        }
                                        if(reader.LocalName == "group")
                                        {
                                                XmlSchemaGroup group = XmlSchemaGroup.Read(reader,h);
                                                if(group != null)
                                                        schema.items.Add(group);
                                                continue;
                                        }
                                        if(reader.LocalName == "attributeGroup")
                                        {
                                                XmlSchemaAttributeGroup attributeGroup = XmlSchemaAttributeGroup.Read(reader,h);
                                                if(attributeGroup != null)
                                                        schema.items.Add(attributeGroup);
                                                continue;
                                        }
                                        if(reader.LocalName == "element")
                                        {
                                                XmlSchemaElement element = XmlSchemaElement.Read(reader,h);
                                                if(element != null)
                                                        schema.items.Add(element);
                                                continue;
                                        }
                                        if(reader.LocalName == "attribute")
                                        {
                                                XmlSchemaAttribute attr = XmlSchemaAttribute.Read(reader,h);
                                                if(attr != null)
                                                        schema.items.Add(attr);
                                                continue;
                                        }
                                        if(reader.LocalName == "notation")
                                        {
                                                XmlSchemaNotation notation = XmlSchemaNotation.Read(reader,h);
                                                if(notation != null)
                                                        schema.items.Add(notation);
                                                continue;
                                        }
                                        if(reader.LocalName == "annotation")
                                        {
                                                XmlSchemaAnnotation annotation = XmlSchemaAnnotation.Read(reader,h);
                                                if(annotation != null)
                                                        schema.items.Add(annotation);
                                                continue;
                                        }
                                }
                                reader.RaiseInvalidElementError();
                        }
                }
		#endregion

                #region write

                public void Write(System.IO.Stream stream)
                {
                        Write(stream,null);
                }
                public void Write(System.IO.TextWriter writer)
                {
                        Write(writer,null);
                }
                public void Write(System.Xml.XmlWriter writer)
                {
                        Write(writer,null);
                }
                public void Write(System.IO.Stream stream, System.Xml.XmlNamespaceManager namespaceManager)
                {
                        Write(new XmlTextWriter(stream,null),namespaceManager);
                }
                public void Write(System.IO.TextWriter writer, System.Xml.XmlNamespaceManager namespaceManager)
                {
                        XmlTextWriter xwriter = new XmlTextWriter(writer);
                        xwriter.Formatting = Formatting.Indented;
                        Write(xwriter,namespaceManager);
                }
                public void Write(System.Xml.XmlWriter writer, System.Xml.XmlNamespaceManager namespaceManager)
                {
                        if(Namespaces == null)
                        {
                                Namespaces = new XmlSerializerNamespaces();
                        }
                        //Add the xml schema namespace.
                        if(Namespaces.Count == 0)
                        {
								if (writer.LookupPrefix (XmlSchema.Namespace) == null)
	                                Namespaces.Add("xs", XmlSchema.Namespace);
                                if (TargetNamespace != null && TargetNamespace != String.Empty)
                                        Namespaces.Add("tns", TargetNamespace);
                        }
                        if(namespaceManager != null)
                        {
                                foreach(string name in namespaceManager)
                                {
                                        //xml and xmlns namespaced are added by default in namespaceManager.
                                        //So we should ignore them
                                        if(name!="xml" && name != "xmlns")
                                                Namespaces.Add(name,namespaceManager.LookupNamespace(name));
                                }
                        }

                        XmlSerializer xser = new XmlSerializer(typeof(XmlSchema));
                        xser.Serialize(writer,this,Namespaces);
                        writer.Flush();
                }
                #endregion
        }
}