using System;
using System.IO;
using System.Linq;
using MediaBrowser.Model.IO;
using MediaBrowser.Model.Serialization;

namespace Emby.Server.Implementations.AppBase
{
    /// <summary>
    /// Class ConfigurationHelper
    /// </summary>
    public static class ConfigurationHelper
    {
        /// <summary>
        /// Reads an xml configuration file from the file system
        /// It will immediately re-serialize and save if new serialization data is available due to property changes
        /// </summary>
        /// <param name="type">The type.</param>
        /// <param name="path">The path.</param>
        /// <param name="xmlSerializer">The XML serializer.</param>
        /// <param name="fileSystem">The file system</param>
        /// <returns>System.Object.</returns>
        public static object GetXmlConfiguration(Type type, string path, IXmlSerializer xmlSerializer, IFileSystem fileSystem)
        {
            object configuration;

            byte[] buffer = null;

            // Use try/catch to avoid the extra file system lookup using File.Exists
            try
            {
                buffer = fileSystem.ReadAllBytes(path);

                configuration = xmlSerializer.DeserializeFromBytes(type, buffer);
            }
            catch (Exception)
            {
                configuration = Activator.CreateInstance(type);
            }

            using (var stream = new MemoryStream())
            {
                xmlSerializer.SerializeToStream(configuration, stream);

                // Take the object we just got and serialize it back to bytes
                var newBytes = stream.ToArray();

                // If the file didn't exist before, or if something has changed, re-save
                if (buffer == null || !buffer.SequenceEqual(newBytes))
                {
                    fileSystem.CreateDirectory(fileSystem.GetDirectoryName(path));

                    // Save it after load in case we got new items
                    fileSystem.WriteAllBytes(path, newBytes);
                }

                return configuration;
            }
        }
    }
}