///
/// Copyright (c) 2017-2019 Sensus Metering Systems
///
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using System.Xml.Serialization;
using log4net;
using Common;

namespace UserManagement
{
    /// <summary>
    /// Class to be serialized to an XML file...
    /// Public members are local settings.
    /// These settings are modified by dialogs invoked by menu items
    ///   Edit->Preferences ... PreferencesDlg ... S1.1(language, etc. local settings), and
    ///   Edit->Advanced settings ... AdvancedSettingsDlg ... S1.2(spec. where bench settings are stored)
    /// </summary>
    [XmlRootAttribute("UserManagement")]
    public class LocalSettings
    {
        private static readonly ILog log = LogManager.GetLogger(typeof(LocalSettings));
        static XmlSerializer serializer = XmlSerializer.FromTypes(new[] { typeof(LocalSettings) })[0];

        ///
        /// Configuration file ecryption/decryption key and initialization vector
        ///
        static byte[] key = new byte[] { 83, 254, 105, 64, 184, 201, 195, 127, 52, 99, 77, 45, 252, 132, 163, 156 };
        static byte[] IV = new byte[] { 189, 23, 137, 56, 204, 241, 242, 118, 28, 89, 9, 198, 224, 111, 186, 125 };


		/// <summary>
        /// User interface language (used as CultureInfo(..) constructor argument).
        /// </summary>
        public string Language = "en";

        public string ConnectionString = "SERVER=10.42.128.24; DATABASE=st_wr_shared_config; UID=u9305784; PASSWORD=p89344390; CHARSET=utf8;";
		
		/// <summary>
		/// Login method: UserName, FullName or Number
		/// </summary>
		public LoginMethod LoginMethod;

		
        public LocalSettings()
        {
        }

        /// <summary>
        /// Load public fields of this class from the XML file.
        /// </summary>
		/// <returns>LocalSettings object or null when Load() fails</returns>
		public static LocalSettings Load(string fileName)
        {
            try
            {
                bool isEncrypted = true;
                using (StreamReader reader = new StreamReader(fileName))
                {
                    isEncrypted = !reader.ReadLine().StartsWith("<?xml version=");
                    reader.Close();
                }

                if (isEncrypted)
                {
                    /// Write settings to a string
                    StringBuilder plain = new StringBuilder();

                    using (RijndaelManaged aes = new RijndaelManaged { Padding = PaddingMode.Zeros })
                    {
                        using (FileStream fsCrypt = new FileStream(fileName, FileMode.Open))
                        {
                            using (ICryptoTransform decryptor = aes.CreateDecryptor(key, IV))
                            {
                                using (CryptoStream cs = new CryptoStream(fsCrypt, decryptor, CryptoStreamMode.Read))
                                {
                                    using (MemoryStream mStream = new MemoryStream())
                                    {
                                        using (var writer = new BinaryWriter(mStream))
                                        {
                                            int data;
                                            while ((data = cs.ReadByte()) != -1)
                                            {
                                                if (data != 0) writer.Write((byte)data);
                                            }
                                            writer.Flush();
                                            mStream.Position = 0;

                                            using (var reader = new StreamReader(mStream))
                                            {
                                                LocalSettings ls = serializer.Deserialize(reader) as LocalSettings;
                                                log.WarnFormat("Succesfully loaded and decrypted from '{0}'", fileName);
                                                return ls;
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                else
                {
                    using (StreamReader reader = new StreamReader(fileName))
                    {
                        LocalSettings ls = serializer.Deserialize(reader) as LocalSettings;
                        log.WarnFormat("Succesfully loaded from '{0}'", fileName);
                        return ls;
                    }
                }
            }
            catch (Exception e)
            {
                log.ErrorFormat("Failed to load from '{0}': {1}", fileName, e.Message);
                return null;
            }
        }

        /// <summary>
        /// Save public fields of this class to the XML file.
        /// </summary>
        public void Save()
        {
            try
            {
                /// Encrypt and write to file 'Program.LocalSettingsFileName'
                using (RijndaelManaged aes = new RijndaelManaged { Padding = PaddingMode.Zeros })
                {
                    using (FileStream fsCrypt = new FileStream(Program.LocalSettingsFileName, FileMode.Create))
                    {
                        using (ICryptoTransform encryptor = aes.CreateEncryptor(key, IV))
                        {
                            using (CryptoStream cs = new CryptoStream(fsCrypt, encryptor, CryptoStreamMode.Write))
                            {
                                using (MemoryStream mStream = new MemoryStream())
                                {
                                    using (var writer = new StreamWriter(mStream))
                                    {
                                        /// Serialize and write settings to a memory stream
                                        serializer.Serialize(writer, this);
                                        writer.Flush();
                                        mStream.Position = 0;

                                        using (var reader = new StreamReader(mStream))
                                        {
                                            /// Encrypt and write to file 'Program.LocalSettingsFileName'
                                            int data;
                                            while ((data = mStream.ReadByte()) != -1) cs.WriteByte((byte)data);

                                            log.WarnFormat("Succesfully encrypted and saved to '{0}'", Program.LocalSettingsFileName);
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
            catch (Exception e)
            {
                log.ErrorFormat("Failed to save to '{0}': {1}", Program.LocalSettingsFileName, e.Message);
            }
        }

		/// <summary>
		/// Updates history stored in a string array by a new latest string.
		/// </summary>
		/// <param name="lastStrValue">Lste entered string</param>
		/// <returns>true = updated and saved</returns>
		public bool UpdateHistory(string lastStrValue, ref string[] history, int maxHistoryLen = 10)
		{
			if (string.IsNullOrEmpty(lastStrValue)) return false;

			int currentHistoryCount = (history != null) ? history.Length : 0;

			int match = -1;
			for (int i = 0; i < currentHistoryCount; i++)
			{
				if (history[i] == lastStrValue)
				{
					match = i;
					break;
				}
			}

			if (match >= 0 || currentHistoryCount >= maxHistoryLen)
			{
				/// History does not have to be (because of a match) or should not be extended (because of the lenght)
				if (match < 0) match = currentHistoryCount - 1;

				for (int j = match; j > 0; j--)
				{
					history[j] = history[j - 1];
				}
				history[0] = lastStrValue;
			}
			else
			{
				/// History wiil be extended, new item inserted at the beginning
				string[] newHistory = new string[currentHistoryCount + 1];
				newHistory[0] = lastStrValue;
				for (int j = 1; j <= currentHistoryCount; j++)
				{
					newHistory[j] = history[j - 1];
				}
				history = newHistory;
			}
			Save();
			return true;
		}
	}
}