"""Pure python library for calculating CRC16"""

##############################################################################
#
#    Copyright (C) Gennady Trafimenkov, 2011
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU Lesser General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU Lesser General Public License for more details.
#
#    You should have received a copy of the GNU Lesser General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
##############################################################################


# table for calculating CRC
# this particular table was generated using pycrc v0.7.6, http://www.tty1.net/pycrc/
# using the configuration:
#  *    Width        = 16
#  *    Poly         = 0x1021
#  *    XorIn        = 0x0000
#  *    ReflectIn    = False
#  *    XorOut       = 0x0000
#  *    ReflectOut   = False
#  *    Algorithm    = table-driven
# by following command:
#   python pycrc.py --model xmodem --algorithm table-driven --generate c
from typing import List

__all__ = ["crc16xmodem"]


_CRC16_XMODEM_TABLE = [
    0x0000,
    0x1021,
    0x2042,
    0x3063,
    0x4084,
    0x50A5,
    0x60C6,
    0x70E7,
    0x8108,
    0x9129,
    0xA14A,
    0xB16B,
    0xC18C,
    0xD1AD,
    0xE1CE,
    0xF1EF,
    0x1231,
    0x0210,
    0x3273,
    0x2252,
    0x52B5,
    0x4294,
    0x72F7,
    0x62D6,
    0x9339,
    0x8318,
    0xB37B,
    0xA35A,
    0xD3BD,
    0xC39C,
    0xF3FF,
    0xE3DE,
    0x2462,
    0x3443,
    0x0420,
    0x1401,
    0x64E6,
    0x74C7,
    0x44A4,
    0x5485,
    0xA56A,
    0xB54B,
    0x8528,
    0x9509,
    0xE5EE,
    0xF5CF,
    0xC5AC,
    0xD58D,
    0x3653,
    0x2672,
    0x1611,
    0x0630,
    0x76D7,
    0x66F6,
    0x5695,
    0x46B4,
    0xB75B,
    0xA77A,
    0x9719,
    0x8738,
    0xF7DF,
    0xE7FE,
    0xD79D,
    0xC7BC,
    0x48C4,
    0x58E5,
    0x6886,
    0x78A7,
    0x0840,
    0x1861,
    0x2802,
    0x3823,
    0xC9CC,
    0xD9ED,
    0xE98E,
    0xF9AF,
    0x8948,
    0x9969,
    0xA90A,
    0xB92B,
    0x5AF5,
    0x4AD4,
    0x7AB7,
    0x6A96,
    0x1A71,
    0x0A50,
    0x3A33,
    0x2A12,
    0xDBFD,
    0xCBDC,
    0xFBBF,
    0xEB9E,
    0x9B79,
    0x8B58,
    0xBB3B,
    0xAB1A,
    0x6CA6,
    0x7C87,
    0x4CE4,
    0x5CC5,
    0x2C22,
    0x3C03,
    0x0C60,
    0x1C41,
    0xEDAE,
    0xFD8F,
    0xCDEC,
    0xDDCD,
    0xAD2A,
    0xBD0B,
    0x8D68,
    0x9D49,
    0x7E97,
    0x6EB6,
    0x5ED5,
    0x4EF4,
    0x3E13,
    0x2E32,
    0x1E51,
    0x0E70,
    0xFF9F,
    0xEFBE,
    0xDFDD,
    0xCFFC,
    0xBF1B,
    0xAF3A,
    0x9F59,
    0x8F78,
    0x9188,
    0x81A9,
    0xB1CA,
    0xA1EB,
    0xD10C,
    0xC12D,
    0xF14E,
    0xE16F,
    0x1080,
    0x00A1,
    0x30C2,
    0x20E3,
    0x5004,
    0x4025,
    0x7046,
    0x6067,
    0x83B9,
    0x9398,
    0xA3FB,
    0xB3DA,
    0xC33D,
    0xD31C,
    0xE37F,
    0xF35E,
    0x02B1,
    0x1290,
    0x22F3,
    0x32D2,
    0x4235,
    0x5214,
    0x6277,
    0x7256,
    0xB5EA,
    0xA5CB,
    0x95A8,
    0x8589,
    0xF56E,
    0xE54F,
    0xD52C,
    0xC50D,
    0x34E2,
    0x24C3,
    0x14A0,
    0x0481,
    0x7466,
    0x6447,
    0x5424,
    0x4405,
    0xA7DB,
    0xB7FA,
    0x8799,
    0x97B8,
    0xE75F,
    0xF77E,
    0xC71D,
    0xD73C,
    0x26D3,
    0x36F2,
    0x0691,
    0x16B0,
    0x6657,
    0x7676,
    0x4615,
    0x5634,
    0xD94C,
    0xC96D,
    0xF90E,
    0xE92F,
    0x99C8,
    0x89E9,
    0xB98A,
    0xA9AB,
    0x5844,
    0x4865,
    0x7806,
    0x6827,
    0x18C0,
    0x08E1,
    0x3882,
    0x28A3,
    0xCB7D,
    0xDB5C,
    0xEB3F,
    0xFB1E,
    0x8BF9,
    0x9BD8,
    0xABBB,
    0xBB9A,
    0x4A75,
    0x5A54,
    0x6A37,
    0x7A16,
    0x0AF1,
    0x1AD0,
    0x2AB3,
    0x3A92,
    0xFD2E,
    0xED0F,
    0xDD6C,
    0xCD4D,
    0xBDAA,
    0xAD8B,
    0x9DE8,
    0x8DC9,
    0x7C26,
    0x6C07,
    0x5C64,
    0x4C45,
    0x3CA2,
    0x2C83,
    0x1CE0,
    0x0CC1,
    0xEF1F,
    0xFF3E,
    0xCF5D,
    0xDF7C,
    0xAF9B,
    0xBFBA,
    0x8FD9,
    0x9FF8,
    0x6E17,
    0x7E36,
    0x4E55,
    0x5E74,
    0x2E93,
    0x3EB2,
    0x0ED1,
    0x1EF0,
]


def _crc16(data: bytes, crc: int, table: List[int]):
    """Calculate CRC16 using the given table.
    `data`      - data for calculating CRC, must be bytes
    `crc`       - initial value
    `table`     - table for caclulating CRC (list of 256 integers)
    Return calculated value of CRC
    """
    for byte in data:
        crc = ((crc << 8) & 0xFF00) ^ table[((crc >> 8) & 0xFF) ^ byte]
    return crc & 0xFFFF


def crc16xmodem(data: bytes, crc: int = 0) -> int:
    """Calculate CRC-CCITT (XModem) variant of CRC16.
    `data`      - data for calculating CRC, must be bytes
    `crc`       - initial value
    Return calculated value of CRC
    """
    return _crc16(data, crc, _CRC16_XMODEM_TABLE)
