using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Phihong_EVSE_UI_Tool
{
    public class FirmwareHeaderBuilder
    {
        public static void AddFirmwareHeader(string temZipPath, string modelName, string outputFilePath)
        {
            var modelNameArray = Encoding.ASCII.GetBytes(modelName);
            var imageDataArray = File.ReadAllBytes(temZipPath);

            byte[] dataSegment1 = new byte[16];
            byte[] dataSegment2 = new byte[16];
            byte[] dataSegment3 = new byte[16];

            Array.Clear(dataSegment1, 0, 16);
            for (int i = 0; i < 16; i++)
            {
                dataSegment2[i] = 0xFF;
                dataSegment3[i] = 0xFF;
            }

            var Lcm_Type = new byte[] { 0x10, 0x00, 0x00, 0x0F };

            // 0000h
            Array.Copy(modelNameArray, 0, dataSegment1, 0, modelNameArray.Length);
            // 0001h
            byte[] imgLenBytes = GetImgLenBytes(imageDataArray);
            byte[] timeBytes = GetCreateTimeBytes();
            //Array.Copy(imageType.CodeArray, 0, dataSegment2, 0, 4);
            Array.Copy(Lcm_Type, 0, dataSegment2, 0, 4);
            Array.Copy(imgLenBytes, 0, dataSegment2, 4, 4);
            Array.Copy(timeBytes, 0, dataSegment2, 8, 8);
            // 0002h
            Array.Copy(timeBytes, 8, dataSegment3, 0, 2);
            byte[] crcBytes = GetCRC32(dataSegment1, dataSegment2, dataSegment3, imageDataArray);
            Array.Copy(crcBytes, 0, dataSegment3, 2, 4);

            List<byte> contents = new List<byte>();
            contents.AddRange(dataSegment1);
            contents.AddRange(dataSegment2);
            contents.AddRange(dataSegment3);
            contents.AddRange(imageDataArray);

            File.WriteAllBytes(outputFilePath, contents.ToArray());
        }

        private static byte[] GetImgLenBytes(byte[] imageArray)
        {
            // Big Endian
            byte[] imgLenBytes = BitConverter.GetBytes(imageArray.Length);
            Array.Reverse(imgLenBytes);

            return imgLenBytes;
        }

        private static byte[] GetCreateTimeBytes()
        {
            string strTime = DateTime.Now.ToString("yyyyMMddHH");
            return Encoding.ASCII.GetBytes(strTime);
        }

        private static byte[] GetCRC32(byte[] segment1, byte[] segment2, byte[] segment3, byte[] imageArray)
        { 
            var crc32Handler = CRC32.GetInatance();
            List<byte> crcData = new List<byte>();
            crcData.AddRange(segment1);
            crcData.AddRange(segment2);
            crcData.AddRange(new byte[] { segment3[0], segment3[1] });
            crcData.AddRange(imageArray);

            ulong crc32 = crc32Handler.Calculate(crcData.ToArray(), crcData.Count);

            // Big Endian
            byte[] outcome = new byte[4];
            outcome[0] = (byte)((crc32 & 0xFF000000) >> 24);
            outcome[1] = (byte)((crc32 & 0x00FF0000) >> 16);
            outcome[2] = (byte)((crc32 & 0x0000FF00) >> 8);
            outcome[3] = (byte)(crc32 & 0x000000FF);

            return outcome;
        }
    }

    class CRC32
    {
        private static CRC32 inatance;

        /// <summary>取得實體。</summary>
        /// <returns></returns>
        public static CRC32 GetInatance()
        {
            if (inatance == null)
            {
                inatance = new CRC32();
            }

            return inatance;
        }

        private ulong[] crc32Table;

        /// <summary>初始化 CRC32 類別的新執行個體。</summary>
        private CRC32()
        {
            crc32Table = new ulong[256];
            GetCRC32Table();
        }

        /// <summary>計算。</summary>
        /// <param name="dataArray"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public ulong Calculate(byte[] dataArray, int length)
        {
            ulong crc = 0xFFFFFFFF;

            for (int i = 0; i < length; i++)
            {
                crc = (crc >> 8) ^ crc32Table[(crc & 0xFF) ^ dataArray[i]];
            }

            return crc ^ 0xFFFFFFFF;
        }

        private void GetCRC32Table()
        {
            ulong crc;
            int i, j;

            for (i = 0; i < 256; i++)
            {
                crc = (ulong)i;
                for (j = 8; j > 0; j--)
                {
                    if ((crc & 1) == 1)
                    {
                        crc = (crc >> 1) ^ 0xEDB88320;
                    }
                    else
                    {
                        crc >>= 1;
                    }
                }
                crc32Table[i] = crc;
            }
        }
    }
}