// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Collections.Generic;
using System.Xml;

namespace System.ServiceModel.Syndication
{
    // NOTE: This class implements Clone so if you add any members, please update the copy ctor
    internal struct ExtensibleSyndicationObject : IExtensibleSyndicationObject
    {
        private Dictionary<XmlQualifiedName, string> _attributeExtensions;
        private SyndicationElementExtensionCollection _elementExtensions;

        private ExtensibleSyndicationObject(ExtensibleSyndicationObject source)
        {
            if (source._attributeExtensions != null)
            {
                _attributeExtensions = new Dictionary<XmlQualifiedName, string>();
                foreach (XmlQualifiedName key in source._attributeExtensions.Keys)
                {
                    _attributeExtensions.Add(key, source._attributeExtensions[key]);
                }
            }
            else
            {
                _attributeExtensions = null;
            }
            if (source._elementExtensions != null)
            {
                _elementExtensions = new SyndicationElementExtensionCollection(source._elementExtensions);
            }
            else
            {
                _elementExtensions = null;
            }
        }

        public Dictionary<XmlQualifiedName, string> AttributeExtensions
        {
            get => _attributeExtensions ??= new Dictionary<XmlQualifiedName, string>();
        }

        public SyndicationElementExtensionCollection ElementExtensions
        {
            get => _elementExtensions ??= new SyndicationElementExtensionCollection();
        }

        private static XmlBuffer CreateXmlBuffer(XmlDictionaryReader unparsedExtensionsReader, int maxExtensionSize)
        {
            XmlBuffer buffer = new XmlBuffer(maxExtensionSize);
            using (XmlDictionaryWriter writer = buffer.OpenSection(unparsedExtensionsReader.Quotas))
            {
                writer.WriteStartElement(Rss20Constants.ExtensionWrapperTag);
                while (unparsedExtensionsReader.IsStartElement())
                {
                    writer.WriteNode(unparsedExtensionsReader, false);
                }
                writer.WriteEndElement();
            }
            buffer.CloseSection();
            buffer.Close();
            return buffer;
        }

        internal void LoadElementExtensions(XmlReader readerOverUnparsedExtensions, int maxExtensionSize)
        {
            ArgumentNullException.ThrowIfNull(readerOverUnparsedExtensions);

            if (maxExtensionSize < 0)
            {
                throw new ArgumentOutOfRangeException(nameof(maxExtensionSize));
            }

            XmlDictionaryReader r = XmlDictionaryReader.CreateDictionaryReader(readerOverUnparsedExtensions);
            _elementExtensions = new SyndicationElementExtensionCollection(CreateXmlBuffer(r, maxExtensionSize));
        }


        internal void LoadElementExtensions(XmlBuffer buffer)
        {
            _elementExtensions = new SyndicationElementExtensionCollection(buffer);
        }

        internal void WriteAttributeExtensions(XmlWriter writer)
        {
            ArgumentNullException.ThrowIfNull(writer);

            if (_attributeExtensions != null)
            {
                foreach (XmlQualifiedName qname in _attributeExtensions.Keys)
                {
                    string value = _attributeExtensions[qname];
                    writer.WriteAttributeString(qname.Name, qname.Namespace, value);
                }
            }
        }

        internal void WriteElementExtensions(XmlWriter writer, Func<string, string, bool> shouldSkipElement = null)
        {
            ArgumentNullException.ThrowIfNull(writer);

            _elementExtensions?.WriteTo(writer, shouldSkipElement);
        }

        public ExtensibleSyndicationObject Clone() => new ExtensibleSyndicationObject(this);
    }
}