#region Disclaimer / License

// Copyright (C) 2013, Jackie Ng
// http://trac.osgeo.org/mapguide/wiki/maestro, jumpinjackie@gmail.com
//
// Original code from SharpDevelop 3.2.1 licensed under the same terms (LGPL 2.1)
// Copyright 2002-2010 by
//
//  AlphaSierraPapa, Christoph Wille
//  Vordernberger Strasse 27/8
//  A-8700 Leoben
//  Austria
//
//  email: office@alphasierrapapa.com
//  court of jurisdiction: Landesgericht Leoben
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//

#endregion Disclaimer / License

using ICSharpCode.TextEditor.Gui.CompletionWindow;
using System;
using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Schema;

namespace Maestro.Editors.Generic.XmlEditor.AutoCompletion
{
    /// <summary>
    /// Holds the completion (intellisense) data for an xml schema.
    /// </summary>
    /// <remarks>
    /// The XmlSchema class throws an exception if we attempt to load
    /// the xhtml1-strict.xsd schema.  It does not like the fact that
    /// this schema redefines the xml namespace, even though this is
    /// allowed by the w3.org specification.
    /// </remarks>
    internal class XmlSchemaCompletionData
    {
        private string namespaceUri = String.Empty;
        private XmlSchema schema;
        private string fileName = String.Empty;
        private bool readOnly = false;

        /// <summary>
        /// Stores attributes that have been prohibited whilst the code
        /// generates the attribute completion data.
        /// </summary>
        private XmlSchemaObjectCollection prohibitedAttributes = new XmlSchemaObjectCollection();

        public XmlSchemaCompletionData()
        {
        }

        /// <summary>
        /// Creates completion data from the schema passed in
        /// via the reader object.
        /// </summary>
        public XmlSchemaCompletionData(TextReader reader)
        {
            ReadSchema(String.Empty, reader);
        }

        /// <summary>
        /// Creates completion data from the schema passed in
        /// via the reader object.
        /// </summary>
        public XmlSchemaCompletionData(XmlTextReader reader)
        {
            reader.XmlResolver = null;
            ReadSchema(reader);
        }

        /// <summary>
        /// Creates the completion data from the specified schema file.
        /// </summary>
        public XmlSchemaCompletionData(string fileName)
            : this(String.Empty, fileName)
        {
        }

        /// <summary>
        /// Creates the completion data from the specified schema file and uses
        /// the specified baseUri to resolve any referenced schemas.
        /// </summary>
        public XmlSchemaCompletionData(string baseUri, string fileName)
        {
            StreamReader reader = new StreamReader(fileName, true);
            ReadSchema(baseUri, reader);
            this.fileName = fileName;
        }

        /// <summary>
        /// Gets the schema.
        /// </summary>
        public XmlSchema Schema
        {
            get
            {
                return schema;
            }
        }

        /// <summary>
        /// Read only schemas are those that are installed with
        /// SharpDevelop.
        /// </summary>
        public bool ReadOnly
        {
            get
            {
                return readOnly;
            }

            set
            {
                readOnly = value;
            }
        }

        /// <summary>
        /// Gets or sets the schema's file name.
        /// </summary>
        public string FileName
        {
            get
            {
                return fileName;
            }
            set
            {
                fileName = value;
            }
        }

        /// <summary>
        /// Gets the namespace URI for the schema.
        /// </summary>
        public string NamespaceUri
        {
            get
            {
                return namespaceUri;
            }
        }

        /// <summary>
        /// Converts the filename into a valid Uri.
        /// </summary>
        public static string GetUri(string fileName)
        {
            string uri = String.Empty;

            if (fileName != null)
            {
                if (fileName.Length > 0)
                {
                    uri = String.Concat("file:///", fileName.Replace('\\', '/'));
                }
            }

            return uri;
        }

        /// <summary>
        /// Gets the possible root elements for an xml document using this schema.
        /// </summary>
        public ICompletionData[] GetElementCompletionData()
        {
            return GetElementCompletionData(String.Empty);
        }

        /// <summary>
        /// Gets the possible root elements for an xml document using this schema.
        /// </summary>
        public ICompletionData[] GetElementCompletionData(string namespacePrefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            foreach (XmlSchemaElement element in schema.Elements.Values)
            {
                if (element.Name != null)
                {
                    AddElement(data, element.Name, namespacePrefix, element.Annotation);
                }
                else
                {
                    // Do not add reference element.
                }
            }

            return data.ToArray();
        }

        /// <summary>
        /// Gets the attribute completion data for the xml element that exists
        /// at the end of the specified path.
        /// </summary>
        public ICompletionData[] GetAttributeCompletionData(XmlElementPath path)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            // Locate matching element.
            XmlSchemaElement element = FindElement(path);

            // Get completion data.
            if (element != null)
            {
                prohibitedAttributes.Clear();
                data = GetAttributeCompletionData(element);
            }

            return data.ToArray();
        }

        /// <summary>
        /// Gets the child element completion data for the xml element that exists
        /// at the end of the specified path.
        /// </summary>
        public ICompletionData[] GetChildElementCompletionData(XmlElementPath path)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            // Locate matching element.
            XmlSchemaElement element = FindElement(path);

            // Get completion data.
            if (element != null)
            {
                data = GetChildElementCompletionData(element, path.Elements.LastPrefix);
            }

            return data.ToArray();
        }

        /// <summary>
        /// Gets the autocomplete data for the specified attribute value.
        /// </summary>
        public ICompletionData[] GetAttributeValueCompletionData(XmlElementPath path, string name)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            // Locate matching element.
            XmlSchemaElement element = FindElement(path);

            // Get completion data.
            if (element != null)
            {
                data = GetAttributeValueCompletionData(element, name);
            }

            return data.ToArray();
        }

        /// <summary>
        /// Finds the element that exists at the specified path.
        /// </summary>
        /// <remarks>This method is not used when generating completion data,
        /// but is a useful method when locating an element so we can jump
        /// to its schema definition.</remarks>
        /// <returns><see langword="null"/> if no element can be found.</returns>
        public XmlSchemaElement FindElement(XmlElementPath path)
        {
            XmlSchemaElement element = null;
            for (int i = 0; i < path.Elements.Count; ++i)
            {
                QualifiedName name = path.Elements[i];
                if (i == 0)
                {
                    // Look for root element.
                    element = FindElement(name);
                    if (element == null)
                    {
                        break;
                    }
                }
                else
                {
                    element = FindChildElement(element, name);
                    if (element == null)
                    {
                        break;
                    }
                }
            }
            return element;
        }

        /// <summary>
        /// Finds an element in the schema.
        /// </summary>
        /// <remarks>
        /// Only looks at the elements that are defined in the
        /// root of the schema so it will not find any elements
        /// that are defined inside any complex types.
        /// </remarks>
        public XmlSchemaElement FindElement(QualifiedName name)
        {
            foreach (XmlSchemaElement element in schema.Elements.Values)
            {
                if (name.Equals(element.QualifiedName))
                {
                    return element;
                }
            }
            return null;
        }

        /// <summary>
        /// Finds the complex type with the specified name.
        /// </summary>
        public XmlSchemaComplexType FindComplexType(QualifiedName name)
        {
            XmlQualifiedName qualifiedName = new XmlQualifiedName(name.Name, name.Namespace);
            return FindNamedType(schema, qualifiedName);
        }

        /// <summary>
        /// Finds the specified attribute name given the element.
        /// </summary>
        /// <remarks>This method is not used when generating completion data,
        /// but is a useful method when locating an attribute so we can jump
        /// to its schema definition.</remarks>
        /// <returns><see langword="null"/> if no attribute can be found.</returns>
        public XmlSchemaAttribute FindAttribute(XmlSchemaElement element, string name)
        {
            XmlSchemaAttribute attribute = null;
            XmlSchemaComplexType complexType = GetElementAsComplexType(element);
            if (complexType != null)
            {
                attribute = FindAttribute(complexType, name);
            }
            return attribute;
        }

        /// <summary>
        /// Finds the attribute group with the specified name.
        /// </summary>
        public XmlSchemaAttributeGroup FindAttributeGroup(string name)
        {
            return FindAttributeGroup(schema, name);
        }

        /// <summary>
        /// Finds the simple type with the specified name.
        /// </summary>
        public XmlSchemaSimpleType FindSimpleType(string name)
        {
            XmlQualifiedName qualifiedName = new XmlQualifiedName(name, namespaceUri);
            return FindSimpleType(qualifiedName);
        }

        /// <summary>
        /// Finds the specified attribute in the schema. This method only checks
        /// the attributes defined in the root of the schema.
        /// </summary>
        public XmlSchemaAttribute FindAttribute(string name)
        {
            foreach (XmlSchemaAttribute attribute in schema.Attributes.Values)
            {
                if (attribute.Name == name)
                {
                    return attribute;
                }
            }
            return null;
        }

        /// <summary>
        /// Finds the schema group with the specified name.
        /// </summary>
        public XmlSchemaGroup FindGroup(string name)
        {
            if (name != null)
            {
                foreach (XmlSchemaObject schemaObject in schema.Groups.Values)
                {
                    XmlSchemaGroup group = schemaObject as XmlSchemaGroup;
                    if (group != null)
                    {
                        if (group.Name == name)
                        {
                            return group;
                        }
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// Takes the name and creates a qualified name using the namespace of this
        /// schema.
        /// </summary>
        /// <remarks>If the name is of the form myprefix:mytype then the correct
        /// namespace is determined from the prefix. If the name is not of this
        /// form then no prefix is added.</remarks>
        public QualifiedName CreateQualifiedName(string name)
        {
            int index = name.IndexOf(":");
            if (index >= 0)
            {
                string prefix = name.Substring(0, index);
                name = name.Substring(index + 1);
                foreach (XmlQualifiedName xmlQualifiedName in schema.Namespaces.ToArray())
                {
                    if (xmlQualifiedName.Name == prefix)
                    {
                        return new QualifiedName(name, xmlQualifiedName.Namespace, prefix);
                    }
                }
            }

            // Default behaviour just return the name with the namespace uri.
            return new QualifiedName(name, namespaceUri);
        }

        /// <summary>
        /// Converts the element to a complex type if possible.
        /// </summary>
        public XmlSchemaComplexType GetElementAsComplexType(XmlSchemaElement element)
        {
            XmlSchemaComplexType complexType = element.SchemaType as XmlSchemaComplexType;
            if (complexType == null)
            {
                complexType = FindNamedType(schema, element.SchemaTypeName);
            }
            return complexType;
        }

        /// <summary>
        /// Handler for schema validation errors.
        /// </summary>
        private void SchemaValidation(object source, ValidationEventArgs e)
        {
            // Do nothing.
        }

        /// <summary>
        /// Loads the schema.
        /// </summary>
        private void ReadSchema(XmlReader reader)
        {
            try
            {
                schema = XmlSchema.Read(reader, new ValidationEventHandler(SchemaValidation));
                schema.Compile(new ValidationEventHandler(SchemaValidation));

                namespaceUri = schema.TargetNamespace;
            }
            finally
            {
                reader.Close();
            }
        }

        private void ReadSchema(string baseUri, TextReader reader)
        {
            XmlTextReader xmlReader = new XmlTextReader(baseUri, reader);

            // Setting the resolver to null allows us to
            // load the xhtml1-strict.xsd without any exceptions if
            // the referenced dtds exist in the same folder as the .xsd
            // file.  If this is not set to null the dtd files are looked
            // for in the assembly's folder.
            xmlReader.XmlResolver = null;
            ReadSchema(xmlReader);
        }

        /// <summary>
        /// Finds an element in the schema.
        /// </summary>
        /// <remarks>
        /// Only looks at the elements that are defined in the
        /// root of the schema so it will not find any elements
        /// that are defined inside any complex types.
        /// </remarks>
        private XmlSchemaElement FindElement(XmlQualifiedName name)
        {
            XmlSchemaElement matchedElement = null;
            foreach (XmlSchemaElement element in schema.Elements.Values)
            {
                if (name.Equals(element.QualifiedName))
                {
                    matchedElement = element;
                    break;
                }
            }

            return matchedElement;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaElement element, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaComplexType complexType = GetElementAsComplexType(element);

            if (complexType != null)
            {
                data = GetChildElementCompletionData(complexType, prefix);
            }

            return data;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaComplexType complexType, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaSequence sequence = complexType.Particle as XmlSchemaSequence;
            XmlSchemaChoice choice = complexType.Particle as XmlSchemaChoice;
            XmlSchemaGroupRef groupRef = complexType.Particle as XmlSchemaGroupRef;
            XmlSchemaComplexContent complexContent = complexType.ContentModel as XmlSchemaComplexContent;
            XmlSchemaAll all = complexType.Particle as XmlSchemaAll;

            if (sequence != null)
            {
                data = GetChildElementCompletionData(sequence.Items, prefix);
            }
            else if (choice != null)
            {
                data = GetChildElementCompletionData(choice.Items, prefix);
            }
            else if (complexContent != null)
            {
                data = GetChildElementCompletionData(complexContent, prefix);
            }
            else if (groupRef != null)
            {
                data = GetChildElementCompletionData(groupRef, prefix);
            }
            else if (all != null)
            {
                data = GetChildElementCompletionData(all.Items, prefix);
            }

            return data;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaObjectCollection items, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            foreach (XmlSchemaObject schemaObject in items)
            {
                XmlSchemaElement childElement = schemaObject as XmlSchemaElement;
                XmlSchemaSequence childSequence = schemaObject as XmlSchemaSequence;
                XmlSchemaChoice childChoice = schemaObject as XmlSchemaChoice;
                XmlSchemaGroupRef groupRef = schemaObject as XmlSchemaGroupRef;

                if (childElement != null)
                {
                    string name = childElement.Name;
                    if (name == null)
                    {
                        name = childElement.RefName.Name;
                        XmlSchemaElement element = FindElement(childElement.RefName);
                        if (element != null)
                        {
                            if (element.IsAbstract)
                            {
                                AddSubstitionGroupElements(data, element.QualifiedName, prefix);
                            }
                            else
                            {
                                AddElement(data, name, prefix, element.Annotation);
                            }
                        }
                        else
                        {
                            AddElement(data, name, prefix, childElement.Annotation);
                        }
                    }
                    else
                    {
                        AddElement(data, name, prefix, childElement.Annotation);
                    }
                }
                else if (childSequence != null)
                {
                    AddElements(data, GetChildElementCompletionData(childSequence.Items, prefix));
                }
                else if (childChoice != null)
                {
                    AddElements(data, GetChildElementCompletionData(childChoice.Items, prefix));
                }
                else if (groupRef != null)
                {
                    AddElements(data, GetChildElementCompletionData(groupRef, prefix));
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaComplexContent complexContent, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaComplexContentExtension extension = complexContent.Content as XmlSchemaComplexContentExtension;
            if (extension != null)
            {
                data = GetChildElementCompletionData(extension, prefix);
            }
            else
            {
                XmlSchemaComplexContentRestriction restriction = complexContent.Content as XmlSchemaComplexContentRestriction;
                if (restriction != null)
                {
                    data = GetChildElementCompletionData(restriction, prefix);
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaComplexContentExtension extension, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaComplexType complexType = FindNamedType(schema, extension.BaseTypeName);
            if (complexType != null)
            {
                data = GetChildElementCompletionData(complexType, prefix);
            }

            // Add any elements.
            if (extension.Particle != null)
            {
                XmlSchemaSequence sequence = extension.Particle as XmlSchemaSequence;
                XmlSchemaChoice choice = extension.Particle as XmlSchemaChoice;
                XmlSchemaGroupRef groupRef = extension.Particle as XmlSchemaGroupRef;

                if (sequence != null)
                {
                    data.AddRange(GetChildElementCompletionData(sequence.Items, prefix));
                }
                else if (choice != null)
                {
                    data.AddRange(GetChildElementCompletionData(choice.Items, prefix));
                }
                else if (groupRef != null)
                {
                    data.AddRange(GetChildElementCompletionData(groupRef, prefix));
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaGroupRef groupRef, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaGroup group = FindGroup(groupRef.RefName.Name);
            if (group != null)
            {
                XmlSchemaSequence sequence = group.Particle as XmlSchemaSequence;
                XmlSchemaChoice choice = group.Particle as XmlSchemaChoice;

                if (sequence != null)
                {
                    data = GetChildElementCompletionData(sequence.Items, prefix);
                }
                else if (choice != null)
                {
                    data = GetChildElementCompletionData(choice.Items, prefix);
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetChildElementCompletionData(XmlSchemaComplexContentRestriction restriction, string prefix)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            // Add any elements.
            if (restriction.Particle != null)
            {
                XmlSchemaSequence sequence = restriction.Particle as XmlSchemaSequence;
                XmlSchemaChoice choice = restriction.Particle as XmlSchemaChoice;
                XmlSchemaGroupRef groupRef = restriction.Particle as XmlSchemaGroupRef;

                if (sequence != null)
                {
                    data = GetChildElementCompletionData(sequence.Items, prefix);
                }
                else if (choice != null)
                {
                    data = GetChildElementCompletionData(choice.Items, prefix);
                }
                else if (groupRef != null)
                {
                    data = GetChildElementCompletionData(groupRef, prefix);
                }
            }

            return data;
        }

        /// <summary>
        /// Adds an element completion data to the collection if it does not
        /// already exist.
        /// </summary>
        private void AddElement(XmlCompletionDataCollection data, string name, string prefix, string documentation)
        {
            if (!data.Contains(name))
            {
                if (prefix.Length > 0)
                {
                    name = String.Concat(prefix, ":", name);
                }
                XmlCompletionData completionData = new XmlCompletionData(name, documentation);
                data.Add(completionData);
            }
        }

        /// <summary>
        /// Adds an element completion data to the collection if it does not
        /// already exist.
        /// </summary>
        private void AddElement(XmlCompletionDataCollection data, string name, string prefix, XmlSchemaAnnotation annotation)
        {
            // Get any annotation documentation.
            string documentation = GetDocumentation(annotation);

            AddElement(data, name, prefix, documentation);
        }

        /// <summary>
        /// Adds elements to the collection if it does not already exist.
        /// </summary>
        private void AddElements(XmlCompletionDataCollection lhs, XmlCompletionDataCollection rhs)
        {
            foreach (XmlCompletionData data in rhs)
            {
                if (!lhs.Contains(data))
                {
                    lhs.Add(data);
                }
            }
        }

        /// <summary>
        /// Gets the documentation from the annotation element.
        /// </summary>
        /// <remarks>
        /// All documentation elements are added.  All text nodes inside
        /// the documentation element are added.
        /// </remarks>
        private string GetDocumentation(XmlSchemaAnnotation annotation)
        {
            string documentation = String.Empty;

            if (annotation != null)
            {
                StringBuilder documentationBuilder = new StringBuilder();
                foreach (XmlSchemaObject schemaObject in annotation.Items)
                {
                    XmlSchemaDocumentation schemaDocumentation = schemaObject as XmlSchemaDocumentation;
                    if (schemaDocumentation != null)
                    {
                        foreach (XmlNode node in schemaDocumentation.Markup)
                        {
                            XmlText textNode = node as XmlText;
                            if (textNode != null)
                            {
                                if (textNode.Data != null)
                                {
                                    if (textNode.Data.Length > 0)
                                    {
                                        documentationBuilder.Append(textNode.Data);
                                    }
                                }
                            }
                        }
                    }
                }

                documentation = documentationBuilder.ToString();
            }

            return documentation;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaElement element)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaComplexType complexType = GetElementAsComplexType(element);

            if (complexType != null)
            {
                data.AddRange(GetAttributeCompletionData(complexType));
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaComplexContentRestriction restriction)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            data.AddRange(GetAttributeCompletionData(restriction.Attributes));

            XmlSchemaComplexType baseComplexType = FindNamedType(schema, restriction.BaseTypeName);
            if (baseComplexType != null)
            {
                data.AddRange(GetAttributeCompletionData(baseComplexType));
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaComplexType complexType)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            data = GetAttributeCompletionData(complexType.Attributes);

            // Add any complex content attributes.
            XmlSchemaComplexContent complexContent = complexType.ContentModel as XmlSchemaComplexContent;
            if (complexContent != null)
            {
                XmlSchemaComplexContentExtension extension = complexContent.Content as XmlSchemaComplexContentExtension;
                XmlSchemaComplexContentRestriction restriction = complexContent.Content as XmlSchemaComplexContentRestriction;
                if (extension != null)
                {
                    data.AddRange(GetAttributeCompletionData(extension));
                }
                else if (restriction != null)
                {
                    data.AddRange(GetAttributeCompletionData(restriction));
                }
            }
            else
            {
                XmlSchemaSimpleContent simpleContent = complexType.ContentModel as XmlSchemaSimpleContent;
                if (simpleContent != null)
                {
                    data.AddRange(GetAttributeCompletionData(simpleContent));
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaComplexContentExtension extension)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            data.AddRange(GetAttributeCompletionData(extension.Attributes));
            XmlSchemaComplexType baseComplexType = FindNamedType(schema, extension.BaseTypeName);
            if (baseComplexType != null)
            {
                data.AddRange(GetAttributeCompletionData(baseComplexType));
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaSimpleContent simpleContent)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaSimpleContentExtension extension = simpleContent.Content as XmlSchemaSimpleContentExtension;
            if (extension != null)
            {
                data.AddRange(GetAttributeCompletionData(extension));
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaSimpleContentExtension extension)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            data.AddRange(GetAttributeCompletionData(extension.Attributes));

            return data;
        }

        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaObjectCollection attributes)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            foreach (XmlSchemaObject schemaObject in attributes)
            {
                XmlSchemaAttribute attribute = schemaObject as XmlSchemaAttribute;
                XmlSchemaAttributeGroupRef attributeGroupRef = schemaObject as XmlSchemaAttributeGroupRef;
                if (attribute != null)
                {
                    if (!IsProhibitedAttribute(attribute))
                    {
                        AddAttribute(data, attribute);
                    }
                    else
                    {
                        prohibitedAttributes.Add(attribute);
                    }
                }
                else if (attributeGroupRef != null)
                {
                    data.AddRange(GetAttributeCompletionData(attributeGroupRef));
                }
            }
            return data;
        }

        /// <summary>
        /// Checks that the attribute is prohibited or has been flagged
        /// as prohibited previously.
        /// </summary>
        private bool IsProhibitedAttribute(XmlSchemaAttribute attribute)
        {
            bool prohibited = false;
            if (attribute.Use == XmlSchemaUse.Prohibited)
            {
                prohibited = true;
            }
            else
            {
                foreach (XmlSchemaAttribute prohibitedAttribute in prohibitedAttributes)
                {
                    if (prohibitedAttribute.QualifiedName == attribute.QualifiedName)
                    {
                        prohibited = true;
                        break;
                    }
                }
            }

            return prohibited;
        }

        /// <summary>
        /// Adds an attribute to the completion data collection.
        /// </summary>
        /// <remarks>
        /// Note the special handling of xml:lang attributes.
        /// </remarks>
        private void AddAttribute(XmlCompletionDataCollection data, XmlSchemaAttribute attribute)
        {
            string name = attribute.Name;
            if (name == null)
            {
                if (attribute.RefName.Namespace == "http://www.w3.org/XML/1998/namespace")
                {
                    name = String.Concat("xml:", attribute.RefName.Name);
                }
            }

            if (name != null)
            {
                string documentation = GetDocumentation(attribute.Annotation);
                XmlCompletionData completionData = new XmlCompletionData(name, documentation, XmlCompletionData.DataType.XmlAttribute);
                data.Add(completionData);
            }
        }

        /// <summary>
        /// Gets attribute completion data from a group ref.
        /// </summary>
        private XmlCompletionDataCollection GetAttributeCompletionData(XmlSchemaAttributeGroupRef groupRef)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();
            XmlSchemaAttributeGroup group = FindAttributeGroup(schema, groupRef.RefName.Name);
            if (group != null)
            {
                data = GetAttributeCompletionData(group.Attributes);
            }

            return data;
        }

        private static XmlSchemaComplexType FindNamedType(XmlSchema schema, XmlQualifiedName name)
        {
            XmlSchemaComplexType matchedComplexType = null;

            if (name != null)
            {
                foreach (XmlSchemaObject schemaObject in schema.Items)
                {
                    XmlSchemaComplexType complexType = schemaObject as XmlSchemaComplexType;
                    if (complexType != null)
                    {
                        if (complexType.QualifiedName == name)
                        {
                            matchedComplexType = complexType;
                            break;
                        }
                    }
                }

                // Try included schemas.
                if (matchedComplexType == null)
                {
                    foreach (XmlSchemaExternal external in schema.Includes)
                    {
                        XmlSchemaInclude include = external as XmlSchemaInclude;
                        if (include != null)
                        {
                            if (include.Schema != null)
                            {
                                matchedComplexType = FindNamedType(include.Schema, name);
                            }
                        }
                    }
                }
            }

            return matchedComplexType;
        }

        /// <summary>
        /// Finds an element that matches the specified <paramref name="name"/>
        /// from the children of the given <paramref name="element"/>.
        /// </summary>
        private XmlSchemaElement FindChildElement(XmlSchemaElement element, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;

            XmlSchemaComplexType complexType = GetElementAsComplexType(element);
            if (complexType != null)
            {
                matchedElement = FindChildElement(complexType, name);
            }

            return matchedElement;
        }

        private XmlSchemaElement FindChildElement(XmlSchemaComplexType complexType, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;

            XmlSchemaSequence sequence = complexType.Particle as XmlSchemaSequence;
            XmlSchemaChoice choice = complexType.Particle as XmlSchemaChoice;
            XmlSchemaGroupRef groupRef = complexType.Particle as XmlSchemaGroupRef;
            XmlSchemaAll all = complexType.Particle as XmlSchemaAll;
            XmlSchemaComplexContent complexContent = complexType.ContentModel as XmlSchemaComplexContent;

            if (sequence != null)
            {
                matchedElement = FindElement(sequence.Items, name);
            }
            else if (choice != null)
            {
                matchedElement = FindElement(choice.Items, name);
            }
            else if (complexContent != null)
            {
                XmlSchemaComplexContentExtension extension = complexContent.Content as XmlSchemaComplexContentExtension;
                XmlSchemaComplexContentRestriction restriction = complexContent.Content as XmlSchemaComplexContentRestriction;
                if (extension != null)
                {
                    matchedElement = FindChildElement(extension, name);
                }
                else if (restriction != null)
                {
                    matchedElement = FindChildElement(restriction, name);
                }
            }
            else if (groupRef != null)
            {
                matchedElement = FindElement(groupRef, name);
            }
            else if (all != null)
            {
                matchedElement = FindElement(all.Items, name);
            }

            return matchedElement;
        }

        /// <summary>
        /// Finds the named child element contained in the extension element.
        /// </summary>
        private XmlSchemaElement FindChildElement(XmlSchemaComplexContentExtension extension, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;

            XmlSchemaComplexType complexType = FindNamedType(schema, extension.BaseTypeName);
            if (complexType != null)
            {
                matchedElement = FindChildElement(complexType, name);

                if (matchedElement == null)
                {
                    XmlSchemaSequence sequence = extension.Particle as XmlSchemaSequence;
                    XmlSchemaChoice choice = extension.Particle as XmlSchemaChoice;
                    XmlSchemaGroupRef groupRef = extension.Particle as XmlSchemaGroupRef;

                    if (sequence != null)
                    {
                        matchedElement = FindElement(sequence.Items, name);
                    }
                    else if (choice != null)
                    {
                        matchedElement = FindElement(choice.Items, name);
                    }
                    else if (groupRef != null)
                    {
                        matchedElement = FindElement(groupRef, name);
                    }
                }
            }

            return matchedElement;
        }

        /// <summary>
        /// Finds the named child element contained in the restriction element.
        /// </summary>
        private XmlSchemaElement FindChildElement(XmlSchemaComplexContentRestriction restriction, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;
            XmlSchemaSequence sequence = restriction.Particle as XmlSchemaSequence;
            XmlSchemaGroupRef groupRef = restriction.Particle as XmlSchemaGroupRef;

            if (sequence != null)
            {
                matchedElement = FindElement(sequence.Items, name);
            }
            else if (groupRef != null)
            {
                matchedElement = FindElement(groupRef, name);
            }

            return matchedElement;
        }

        /// <summary>
        /// Finds the element in the collection of schema objects.
        /// </summary>
        private XmlSchemaElement FindElement(XmlSchemaObjectCollection items, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;

            foreach (XmlSchemaObject schemaObject in items)
            {
                XmlSchemaElement element = schemaObject as XmlSchemaElement;
                XmlSchemaSequence sequence = schemaObject as XmlSchemaSequence;
                XmlSchemaChoice choice = schemaObject as XmlSchemaChoice;
                XmlSchemaGroupRef groupRef = schemaObject as XmlSchemaGroupRef;

                if (element != null)
                {
                    if (element.Name != null)
                    {
                        if (name.Name == element.Name)
                        {
                            matchedElement = element;
                        }
                    }
                    else if (element.RefName != null)
                    {
                        if (name.Name == element.RefName.Name)
                        {
                            matchedElement = FindElement(element.RefName);
                        }
                        else
                        {
                            // Abstract element?
                            XmlSchemaElement abstractElement = FindElement(element.RefName);
                            if (abstractElement != null && abstractElement.IsAbstract)
                            {
                                matchedElement = FindSubstitutionGroupElement(abstractElement.QualifiedName, name);
                            }
                        }
                    }
                }
                else if (sequence != null)
                {
                    matchedElement = FindElement(sequence.Items, name);
                }
                else if (choice != null)
                {
                    matchedElement = FindElement(choice.Items, name);
                }
                else if (groupRef != null)
                {
                    matchedElement = FindElement(groupRef, name);
                }

                // Did we find a match?
                if (matchedElement != null)
                {
                    break;
                }
            }

            return matchedElement;
        }

        private XmlSchemaElement FindElement(XmlSchemaGroupRef groupRef, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;

            XmlSchemaGroup group = FindGroup(groupRef.RefName.Name);
            if (group != null)
            {
                XmlSchemaSequence sequence = group.Particle as XmlSchemaSequence;
                XmlSchemaChoice choice = group.Particle as XmlSchemaChoice;

                if (sequence != null)
                {
                    matchedElement = FindElement(sequence.Items, name);
                }
                else if (choice != null)
                {
                    matchedElement = FindElement(choice.Items, name);
                }
            }

            return matchedElement;
        }

        private static XmlSchemaAttributeGroup FindAttributeGroup(XmlSchema schema, string name)
        {
            XmlSchemaAttributeGroup matchedGroup = null;

            if (name != null)
            {
                foreach (XmlSchemaObject schemaObject in schema.Items)
                {
                    XmlSchemaAttributeGroup group = schemaObject as XmlSchemaAttributeGroup;
                    if (group != null)
                    {
                        if (group.Name == name)
                        {
                            matchedGroup = group;
                            break;
                        }
                    }
                }

                // Try included schemas.
                if (matchedGroup == null)
                {
                    foreach (XmlSchemaExternal external in schema.Includes)
                    {
                        XmlSchemaInclude include = external as XmlSchemaInclude;
                        if (include != null)
                        {
                            if (include.Schema != null)
                            {
                                matchedGroup = FindAttributeGroup(include.Schema, name);
                            }
                        }
                    }
                }
            }

            return matchedGroup;
        }

        private XmlCompletionDataCollection GetAttributeValueCompletionData(XmlSchemaElement element, string name)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaComplexType complexType = GetElementAsComplexType(element);
            if (complexType != null)
            {
                XmlSchemaAttribute attribute = FindAttribute(complexType, name);
                if (attribute != null)
                {
                    data.AddRange(GetAttributeValueCompletionData(attribute));
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeValueCompletionData(XmlSchemaAttribute attribute)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            if (attribute.SchemaType != null)
            {
                XmlSchemaSimpleTypeRestriction simpleTypeRestriction = attribute.SchemaType.Content as XmlSchemaSimpleTypeRestriction;
                if (simpleTypeRestriction != null)
                {
                    data.AddRange(GetAttributeValueCompletionData(simpleTypeRestriction));
                }
            }
            else if (attribute.AttributeSchemaType != null)
            {
                XmlSchemaSimpleType simpleType = attribute.AttributeSchemaType as XmlSchemaSimpleType;

                if (simpleType != null)
                {
                    if (simpleType.Name == "boolean")
                    {
                        data.AddRange(GetBooleanAttributeValueCompletionData());
                    }
                    else
                    {
                        data.AddRange(GetAttributeValueCompletionData(simpleType));
                    }
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeValueCompletionData(XmlSchemaSimpleTypeRestriction simpleTypeRestriction)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            foreach (XmlSchemaObject schemaObject in simpleTypeRestriction.Facets)
            {
                XmlSchemaEnumerationFacet enumFacet = schemaObject as XmlSchemaEnumerationFacet;
                if (enumFacet != null)
                {
                    AddAttributeValue(data, enumFacet.Value, enumFacet.Annotation);
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeValueCompletionData(XmlSchemaSimpleTypeUnion union)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            foreach (XmlSchemaObject schemaObject in union.BaseTypes)
            {
                XmlSchemaSimpleType simpleType = schemaObject as XmlSchemaSimpleType;
                if (simpleType != null)
                {
                    data.AddRange(GetAttributeValueCompletionData(simpleType));
                }
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeValueCompletionData(XmlSchemaSimpleType simpleType)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            XmlSchemaSimpleTypeRestriction simpleTypeRestriction = simpleType.Content as XmlSchemaSimpleTypeRestriction;
            XmlSchemaSimpleTypeUnion union = simpleType.Content as XmlSchemaSimpleTypeUnion;
            XmlSchemaSimpleTypeList list = simpleType.Content as XmlSchemaSimpleTypeList;

            if (simpleTypeRestriction != null)
            {
                data.AddRange(GetAttributeValueCompletionData(simpleTypeRestriction));
            }
            else if (union != null)
            {
                data.AddRange(GetAttributeValueCompletionData(union));
            }
            else if (list != null)
            {
                data.AddRange(GetAttributeValueCompletionData(list));
            }

            return data;
        }

        private XmlCompletionDataCollection GetAttributeValueCompletionData(XmlSchemaSimpleTypeList list)
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            if (list.ItemType != null)
            {
                data.AddRange(GetAttributeValueCompletionData(list.ItemType));
            }
            else if (list.ItemTypeName != null)
            {
                XmlSchemaSimpleType simpleType = FindSimpleType(list.ItemTypeName);
                if (simpleType != null)
                {
                    data.AddRange(GetAttributeValueCompletionData(simpleType));
                }
            }

            return data;
        }

        /// <summary>
        /// Gets the set of attribute values for an xs:boolean type.
        /// </summary>
        private XmlCompletionDataCollection GetBooleanAttributeValueCompletionData()
        {
            XmlCompletionDataCollection data = new XmlCompletionDataCollection();

            AddAttributeValue(data, "0");
            AddAttributeValue(data, "1");
            AddAttributeValue(data, "true");
            AddAttributeValue(data, "false");

            return data;
        }

        private XmlSchemaAttribute FindAttribute(XmlSchemaComplexType complexType, string name)
        {
            XmlSchemaAttribute matchedAttribute = null;

            matchedAttribute = FindAttribute(complexType.Attributes, name);

            if (matchedAttribute == null)
            {
                XmlSchemaComplexContent complexContent = complexType.ContentModel as XmlSchemaComplexContent;
                if (complexContent != null)
                {
                    matchedAttribute = FindAttribute(complexContent, name);
                }
            }

            return matchedAttribute;
        }

        private XmlSchemaAttribute FindAttribute(XmlSchemaObjectCollection schemaObjects, string name)
        {
            XmlSchemaAttribute matchedAttribute = null;

            foreach (XmlSchemaObject schemaObject in schemaObjects)
            {
                XmlSchemaAttribute attribute = schemaObject as XmlSchemaAttribute;
                XmlSchemaAttributeGroupRef groupRef = schemaObject as XmlSchemaAttributeGroupRef;

                if (attribute != null)
                {
                    if (attribute.Name == name)
                    {
                        matchedAttribute = attribute;
                        break;
                    }
                }
                else if (groupRef != null)
                {
                    matchedAttribute = FindAttribute(groupRef, name);
                    if (matchedAttribute != null)
                    {
                        break;
                    }
                }
            }

            return matchedAttribute;
        }

        private XmlSchemaAttribute FindAttribute(XmlSchemaAttributeGroupRef groupRef, string name)
        {
            XmlSchemaAttribute matchedAttribute = null;

            if (groupRef.RefName != null)
            {
                XmlSchemaAttributeGroup group = FindAttributeGroup(schema, groupRef.RefName.Name);
                if (group != null)
                {
                    matchedAttribute = FindAttribute(group.Attributes, name);
                }
            }

            return matchedAttribute;
        }

        private XmlSchemaAttribute FindAttribute(XmlSchemaComplexContent complexContent, string name)
        {
            XmlSchemaAttribute matchedAttribute = null;

            XmlSchemaComplexContentExtension extension = complexContent.Content as XmlSchemaComplexContentExtension;
            XmlSchemaComplexContentRestriction restriction = complexContent.Content as XmlSchemaComplexContentRestriction;

            if (extension != null)
            {
                matchedAttribute = FindAttribute(extension, name);
            }
            else if (restriction != null)
            {
                matchedAttribute = FindAttribute(restriction, name);
            }

            return matchedAttribute;
        }

        private XmlSchemaAttribute FindAttribute(XmlSchemaComplexContentExtension extension, string name)
        {
            return FindAttribute(extension.Attributes, name);
        }

        private XmlSchemaAttribute FindAttribute(XmlSchemaComplexContentRestriction restriction, string name)
        {
            XmlSchemaAttribute matchedAttribute = FindAttribute(restriction.Attributes, name);

            if (matchedAttribute == null)
            {
                XmlSchemaComplexType complexType = FindNamedType(schema, restriction.BaseTypeName);
                if (complexType != null)
                {
                    matchedAttribute = FindAttribute(complexType, name);
                }
            }

            return matchedAttribute;
        }

        /// <summary>
        /// Adds an attribute value to the completion data collection.
        /// </summary>
        private void AddAttributeValue(XmlCompletionDataCollection data, string valueText)
        {
            XmlCompletionData completionData = new XmlCompletionData(valueText, XmlCompletionData.DataType.XmlAttributeValue);
            data.Add(completionData);
        }

        /// <summary>
        /// Adds an attribute value to the completion data collection.
        /// </summary>
        private void AddAttributeValue(XmlCompletionDataCollection data, string valueText, XmlSchemaAnnotation annotation)
        {
            string documentation = GetDocumentation(annotation);
            XmlCompletionData completionData = new XmlCompletionData(valueText, documentation, XmlCompletionData.DataType.XmlAttributeValue);
            data.Add(completionData);
        }

        /// <summary>
        /// Adds an attribute value to the completion data collection.
        /// </summary>
        private void AddAttributeValue(XmlCompletionDataCollection data, string valueText, string description)
        {
            XmlCompletionData completionData = new XmlCompletionData(valueText, description, XmlCompletionData.DataType.XmlAttributeValue);
            data.Add(completionData);
        }

        private XmlSchemaSimpleType FindSimpleType(XmlQualifiedName name)
        {
            XmlSchemaSimpleType matchedSimpleType = null;

            foreach (XmlSchemaObject schemaObject in schema.SchemaTypes.Values)
            {
                XmlSchemaSimpleType simpleType = schemaObject as XmlSchemaSimpleType;
                if (simpleType != null)
                {
                    if (simpleType.QualifiedName == name)
                    {
                        matchedSimpleType = simpleType;
                        break;
                    }
                }
            }

            return matchedSimpleType;
        }

        /// <summary>
        /// Adds any elements that have the specified substitution group.
        /// </summary>
        private void AddSubstitionGroupElements(XmlCompletionDataCollection data, XmlQualifiedName group, string prefix)
        {
            foreach (XmlSchemaElement element in schema.Elements.Values)
            {
                if (element.SubstitutionGroup == group)
                {
                    AddElement(data, element.Name, prefix, element.Annotation);
                }
            }
        }

        /// <summary>
        /// Looks for the substitution group element of the specified name.
        /// </summary>
        private XmlSchemaElement FindSubstitutionGroupElement(XmlQualifiedName group, QualifiedName name)
        {
            XmlSchemaElement matchedElement = null;

            foreach (XmlSchemaElement element in schema.Elements.Values)
            {
                if (element.SubstitutionGroup == group)
                {
                    if (element.Name != null)
                    {
                        if (element.Name == name.Name)
                        {
                            matchedElement = element;
                            break;
                        }
                    }
                }
            }

            return matchedElement;
        }
    }
}