///
/// Copyright (c) 2021 Sensus Slovensko a.s.
///
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using System.Xml.Serialization;

namespace UniControlBoardTest
{
    /// <summary>
    /// Class to be serialized to an XML file...
    /// </summary>
    [XmlRootAttribute("Workplace620")]
    public class 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 };

        public int SerialPortNr;

        public LocalSettings()
        {
        }

        public LocalSettings(bool createNew)
            : this()
        {
            if (createNew)
            {
                SerialPortNr = 1;
            }
        }

        /// <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))
                                            {
                                                return serializer.Deserialize(reader) as LocalSettings;
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                else
                {
                    using (StreamReader reader = new StreamReader(fileName))
                    {
                        return serializer.Deserialize(reader) as LocalSettings;
                    }
                }
            }
            catch (Exception e)
            {
                string msg = 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);
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
            catch (Exception e)
            {
                string msg = e.Message;
            }
        }

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

            if (string.IsNullOrEmpty(lastStrValue)) return false;

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

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

            if (match >= 0 || currentHistoryLength >= MaxHistoryLen)
            {
                /// History does not have to be extended (because of a match) or should not be extended (because of the lenght)
                if (match < 0) match = currentHistoryLength - 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[currentHistoryLength + 1];
                newHistory[0] = lastStrValue;
                for (int j = 1; j <= currentHistoryLength; j++)
                {
                    newHistory[j] = history[j - 1];
                }
                history = newHistory;
            }
            Save();
            return true;
        }
    }
}