CryptoManager

using System;
using DataTypes;

namespace CryptoSystem {
    public class CryptoManager {
        private static CryptoManager i;

        public static CryptoManager I {
            get => i ?? (i = new CryptoManager());
            private set => i = value;
        }

        public CryptoManager() {
            if (i != null) throw new Exception("CryptoManager is created");
            i = this;
        }

        /// <summary>
        /// Шифрование массива
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public byte[] Encrypt(byte[] data) {
            var segments = SplitArray(data);
            for (var i = 0; i < segments.Length; i++)
                segments[i] = EncryptExternal(segments[i]);
            return CombineArray(segments);
        }

        //Дешифрование массива
        public byte[] Decrypt(byte[] data) {
            var segments = SplitArray(data);
            for (var i = 0; i < segments.Length; i++)
                segments[i] = DecryptExternal(segments[i]);
            return CombineArray(segments);
        }

        /// <summary>
        /// Внений вызов шифрования сегмента
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        private byte[] EncryptExternal(byte[] data) {
            return data;
        }

        /// <summary>
        /// Внешний вызов дешифрования сегментов
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        private byte[] DecryptExternal(byte[] data) {
            return data;
        }

        /// <summary>
        /// Разбивает массив на сегменты
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        private byte[][] SplitArray(byte[] data) {
            var segments = data.Length / PacketData._packetLength;
            if (data.Length - segments * PacketData._packetLength > 0) {
                segments++;
            }

            var arr = new byte[segments][];
            for (int i = 0; i < segments; i++) {
                arr[i] = PacketData.ExtractSubarray(data, i * PacketData._packetLength, PacketData._packetLength);
            }

            return arr;
        }

        /// <summary>
        /// Склеивает сегменты в один массив
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        private byte[] CombineArray(byte[][] data) {
            var c      = 0;
            var result = new byte[data.Length * PacketData._packetLength];
            foreach (var i in data)
                foreach (var j in i)
                    result[c] = j;
            return result;
        }
    }
}