"""
websocket - WebSocket client library for Python

Copyright (C) 2010 Hiroki Ohtani(liris)

    This library 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 2.1 of the License, or (at your option) any later version.

    This library 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 library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1335  USA

"""

import six

__all__ = ["NoLock", "validate_utf8", "extract_err_message"]

class NoLock(object):
    def __enter__(self):
        pass

    def __exit__(self,type, value, traceback):
        pass


# UTF-8 validator
# python implementation of http://bjoern.hoehrmann.de/utf-8/decoder/dfa/

UTF8_ACCEPT = 0
UTF8_REJECT=12

_UTF8D = [
    # The first part of the table maps bytes to character classes that
    # to reduce the size of the transition table and create bitmasks.
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,  9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
    10,3,3,3,3,3,3,3,3,3,3,3,3,4,3,3, 11,6,6,6,5,8,8,8,8,8,8,8,8,8,8,8,

    # The second part is a transition table that maps a combination
    # of a state of the automaton and a character class to a state.
    0,12,24,36,60,96,84,12,12,12,48,72, 12,12,12,12,12,12,12,12,12,12,12,12,
    12, 0,12,12,12,12,12, 0,12, 0,12,12, 12,24,12,12,12,12,12,24,12,24,12,12,
    12,12,12,12,12,12,12,24,12,12,12,12, 12,24,12,12,12,12,12,12,12,24,12,12,
    12,12,12,12,12,12,12,36,12,36,12,12, 12,36,12,12,12,12,12,36,12,36,12,12,
    12,36,12,12,12,12,12,12,12,12,12,12, ]

def _decode(state, codep, ch):
    tp = _UTF8D[ch]

    codep = (ch & 0x3f ) | (codep << 6) if (state != UTF8_ACCEPT)  else (0xff >> tp) & (ch)
    state = _UTF8D[256 + state + tp]

    return state, codep;

def validate_utf8(utfbytes):
    """
    validate utf8 byte string.
    utfbytes: utf byte string to check.
    return value: if valid utf8 string, return true. Otherwise, return false.
    """
    state = UTF8_ACCEPT
    codep = 0
    for i in utfbytes:
        if six.PY2:
            i = ord(i)
        state, codep = _decode(state, codep, i)
        if state == UTF8_REJECT:
            return False

    return True


def extract_err_message(exception):
    return getattr(exception, 'strerror', str(exception))
