using System;
using System.Collections.Generic;
using System.Text;
using Xylem.Common.Logic.ProductionOrderCore.OrderData;
using Xylem.Common.Utils.Crc16Ccitt;

namespace Xylem.Common.Hardware.WaterMeter.Genesis.GenesisFile
{
    /// <summary>
    /// File for metrology look up table
    /// </summary>
    public class MeterLutFile
    {
        /// <summary>
        /// Meter response on invalid LUT file e.g. 0x8000FFFF
        /// </summary>
        public const String StrLutFileInvalidCrc = "0x8000";

        /// <summary>
        /// Disk number and name of meter LUT file
        /// </summary>
        public const String StrLutMeterFileName = "1\\mettbl";

        /// <summary>
        /// Disk number and name of meter LUT file
        /// </summary>
        public const String StrLutBackupMeterFileName = "1\\mettbl_b";

        // identifier for Genesis lookup table
        public const String StrLutMeterFileId = "GEN_LUT\0";
        public const Int32 IndexLutFileId = 0;
        public const Int32 LengthLutFileId = 8;

        // data length, calculated from version field to the end of the data section
        public const Int32 IndexDataLength = 8;
        public const Int32 LengthDataLength = 4;

        // CCITT-CRC-16 , calculated from version field to the end of the data section
        public const Int32 IndexCrc = 12;
        public const Int32 LengthCrc = 2;

        // version
        public const Int32 IndexVersion = 14;
        public const Int32 LengthVersion = 2;

        // meter size as enumeration
        public const Int32 IndexMeterSize = 16;

        // header size of file
        public const Int32 LutFileHeaderLength = LengthLutFileId + LengthDataLength + LengthCrc + LengthVersion;

        // data size of file is variable found 730, 5840, 13140, so it has to be read using the header
        // public const Int32 LutFileDataLength = 730;

        // LUT file entire file size
        public Int32 SizeLutFile;

        /// <summary>
        /// File name of the file on PC
        /// </summary>
        public String LutPcFileName;

        /// <summary>
        /// Standard Ctor without name
        /// </summary>
        public MeterLutFile()
        {
        }
 
        /// <summary>
        /// Ctor for meter lut file
        /// </summary>
        /// <param name="lutPcFileName"></param>
        public MeterLutFile(String lutPcFileName)
        {
            LutPcFileName = lutPcFileName;
        }
 
        /// <summary>
        /// File ID for LUT file
        /// </summary>
        public String StrLutFileId;

        /// <summary>
        /// Data length
        /// </summary>
        private UInt32 _dataLength;
        public UInt32 DataLength
        {
            get => _dataLength;
            set
            {
                SizeLutFile = (Int32)value + LutFileHeaderLength;
                _dataLength = value;
            }
        }

        /// <summary>
        /// Version of LUT file
        /// </summary>
        public UInt16 Version;

        /// <summary>
        /// Check of LUT file for verification and register write, read from file
        /// </summary>
        public UInt16 FileCrc;

        /// <summary>
        /// Calculated during file processing for verification
        /// </summary>
        public UInt16 CalculatedCrc;

        /// <summary>
        /// FileCRC and calculated CRC are different
        /// </summary>
        public Boolean CrcError;

        /// <summary>
        /// Validation of LUT file
        /// </summary>
        public Boolean IsValid;

        /// <summary>
        /// Binary file content
        /// </summary>
        public List<Byte> BinData = new List<Byte>();

        /// <summary>
        /// Meter size
        /// </summary>
        public MeterSize MeterSize;

        /// <summary>
        /// ATTENTION: The file size is dynamic!
        /// Verifies the LUT format based on its contents
        /// </summary>
        /// <returns>true if valid</returns>
        /// <remarks date="2023-Nov-13" author="Thomas Wiedebusch">
        /// - Initial.
        /// </remarks>
        /// <remarks date="2023-Nov-17" author="Thomas Wiedebusch">
        /// - Removed constant size, instead using header to calculate the size of the file.
        /// </remarks>
        public Boolean ValidateLutFormat()
        {
            IsValid = false;

            if (BinData == null || BinData.Count < LutFileHeaderLength)
                return false;
            // extract the identifier and check, if this is a LUT file
            StrLutFileId = Encoding.UTF8.GetString(BinData.ToArray(), MeterLutFile.IndexLutFileId, 
                MeterLutFile.IndexDataLength);
            if (StrLutFileId != MeterLutFile.StrLutMeterFileId)
                return false;

            MeterSize = (MeterSize)BinData[MeterLutFile.IndexMeterSize];
            FileCrc = (UInt16)(BinData[MeterLutFile.IndexCrc] + 
                                       (BinData[MeterLutFile.IndexCrc + 1] << 8));
            Version = (UInt16)(BinData[MeterLutFile.IndexVersion] + 
                                       (BinData[MeterLutFile.IndexVersion + 1] << 8));
            DataLength = (UInt32)(BinData[MeterLutFile.IndexDataLength]
                                          + (BinData[MeterLutFile.IndexDataLength + 1] << 8)
                                          + (BinData[MeterLutFile.IndexDataLength + 2] << 16)
                                          + (BinData[MeterLutFile.IndexDataLength + 3] << 24));
            // calculate CRC and compare this with the file CRC
            var entireFile = new List<Byte>();
            entireFile.AddRange(BinData);
            var payload = new List<Byte>();
            payload.AddRange(entireFile.GetRange(MeterLutFile.IndexVersion, 
                (Int32)DataLength + MeterLutFile.LengthVersion));
            CalculatedCrc = Crc16Ccitt.CalculateMsb1021(payload.ToArray());
            if (CalculatedCrc != FileCrc)
            {
                CrcError = true;
                return false;
            }

            CrcError = false;
            IsValid = true;
            return true;
        }
    }
}