"""
HDLC framing module.

.. moduleauthor:: Min Ting <tingm417@gmail.com>
                  October 2012
"""

import logging
from .utils import format_string_buf

# from openvisualizer.utils import format_string_buf


logging.basicConfig()
log = logging.getLogger(__name__)
log.setLevel(logging.INFO)


def format_buf(buf):
    """
    Format a bytelist into an easy-to-read string. For example:

    ``[0xab,0xcd,0xef,0x00] -> '(4B) ab-cd-ef-00'``
    """

    return '({0:>2}B) {1}'.format(len(buf), '-'.join(["%02x" % b for b in buf]))


class HdlcException(Exception):
    pass


class OpenHdlc(object):
    HDLC_FLAG = '\x7e'
    HDLC_FLAG_ESCAPED = '\x5e'
    HDLC_ESCAPE = '\x7d'
    HDLC_ESCAPE_ESCAPED = '\x5d'
    HDLC_CRCINIT = 0xffff
    HDLC_CRCGOOD = 0xf0b8

    FCS16TAB = (
        0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
        0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
        0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
        0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
        0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
        0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
        0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
        0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
        0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
        0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
        0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
        0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
        0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
        0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
        0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
        0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
        0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
        0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
        0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
        0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
        0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
        0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
        0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
        0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
        0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
        0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
        0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
        0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
        0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
        0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
        0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
        0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78,
    )

    # ============================ public ======================================

    def hdlcify(self, in_buf):
        """
        Build an hdlc frame.

        Use 0x00 for both addr byte, and control byte.
        """

        # make copy of input
        out_buf = in_buf[:]

        # calculate CRC
        crc = self.HDLC_CRCINIT
        for b in out_buf:
            crc = self._crc_iteration(crc, b)

        crc = 0xffff - crc

        # append CRC
        out_buf = out_buf.decode("utf-8") + chr(crc & 0xff) + chr((crc & 0xff00) >> 8)

        # stuff bytes
        out_buf = out_buf.replace(self.HDLC_ESCAPE, self.HDLC_ESCAPE + self.HDLC_ESCAPE_ESCAPED)
        out_buf = out_buf.replace(self.HDLC_FLAG, self.HDLC_ESCAPE + self.HDLC_FLAG_ESCAPED)

        # add flags
        out_buf = self.HDLC_FLAG + out_buf + self.HDLC_FLAG

        bif = bytearray()
        for b in out_buf:
            bif += ord(b).to_bytes(1, "little")

        return bif

    def dehdlcify(self, in_buf):
        """
        Parse an hdlc frame.

        :returns: the extracted frame, or -1 if wrong checksum
        """

        assert in_buf[0] == self.HDLC_FLAG
        assert in_buf[-1] == self.HDLC_FLAG

        # make copy of input
        out_buf = in_buf[:]
        if log.isEnabledFor(logging.DEBUG):
            log.debug("got              {0}".format(format_string_buf(out_buf)))

        # remove flags
        out_buf = out_buf[1:-1]
        if log.isEnabledFor(logging.DEBUG):
            log.debug("after flags:     {0}".format(format_string_buf(out_buf)))

        # unstuff
        out_buf = out_buf.replace(self.HDLC_ESCAPE + self.HDLC_FLAG_ESCAPED, self.HDLC_FLAG)
        out_buf = out_buf.replace(self.HDLC_ESCAPE + self.HDLC_ESCAPE_ESCAPED, self.HDLC_ESCAPE)
        if log.isEnabledFor(logging.DEBUG):
            log.debug("after unstuff:   {0}".format(format_string_buf(out_buf)))

        if len(out_buf) < 2:
            raise HdlcException('packet too short')

        # check CRC
        crc = self.HDLC_CRCINIT

        for b in out_buf:
            crc = self._crc_iteration(crc, ord(b))

        if crc != self.HDLC_CRCGOOD:
            raise HdlcException('wrong CRC')

        # remove CRC
        out_buf = out_buf[:-2]  # remove CRC
        if log.isEnabledFor(logging.DEBUG):
            log.debug("after CRC:       {0}".format(format_string_buf(out_buf)))

        return out_buf

    # ============================ private =====================================

    def _crc_iteration(self, crc, b):
        return (crc >> 8) ^ self.FCS16TAB[((crc ^ b) & 0xff)]
