using System;
using System.IO;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;

namespace Configuration
{
    public static class Serialization
    {
        #region Private Delegates, Events, Enums, Properties, Indexers and Fields

        private static XmlSerializer ConfigurationSerializer { get; } = new XmlSerializer(typeof(Settings));

        private static XmlReaderSettings XmlReaderSettings { get; } = new XmlReaderSettings
        {
            Async = true,
            ValidationType = ValidationType.Schema,
            IgnoreWhitespace = true,
            ValidationFlags =
                XmlSchemaValidationFlags
                    .ProcessInlineSchema |
                XmlSchemaValidationFlags
                    .ProcessSchemaLocation |
                XmlSchemaValidationFlags
                    .ReportValidationWarnings,
            DtdProcessing = DtdProcessing.Parse
        };

        private static XmlWriterSettings XmlWriterSettings { get; } = new XmlWriterSettings
        {
            Async = true,
            Indent = true,
            IndentChars = "    ",
            OmitXmlDeclaration = false
        };

        #endregion

        #region Public Methods

        public static async Task<SerializationState> Serialize(this Settings settings, string file)
        {
            try
            {
                using (var streamWriter = new StreamWriter(file))
                {
                    using (var xmlWriter =
                        XmlWriter.Create(streamWriter, XmlWriterSettings))
                    {
                        await xmlWriter.WriteDocTypeAsync("Configuration",
                            null,
                            null,
                            "<!ATTLIST Configuration xmlns:xsi CDATA #IMPLIED xsi:noNamespaceSchemaLocation CDATA #IMPLIED>");

                        ConfigurationSerializer.Serialize(xmlWriter, settings);
                    }
                }

                return new SerializationSuccess();
            }
            catch (Exception ex)
            {
                return new SerializationFailure {Exception = ex};
            }
        }

        public static SerializationState Deserialize(string file)
        {
            try
            {
                Settings configuration;

                using (var streamReader = new StreamReader(file))
                {
                    using (var xmlReader = XmlReader.Create(streamReader, XmlReaderSettings))
                    {
                        configuration = (Settings) ConfigurationSerializer.Deserialize(xmlReader);
                    }
                }

                return new SerializationSuccess<Settings>
                {
                    Result = configuration
                };
            }
            catch (Exception ex)
            {
                return new SerializationFailure
                {
                    Exception = ex
                };
            }
        }

        #endregion
    }
}