"""Backports for individual classes and functions."""

import os
import re
import sys
import codecs

__all__ = ['any', 'detect_encoding', 'fsencode', 'python_implementation',
           'wraps']


try:
    any = any
except NameError:
    def any(seq):
        for elem in seq:
            if elem:
                return True
        return False


_cookie_re = re.compile("coding[:=]\s*([-\w.]+)")


def _get_normal_name(orig_enc):
    """Imitates get_normal_name in tokenizer.c."""
    # Only care about the first 12 characters.
    enc = orig_enc[:12].lower().replace("_", "-")
    if enc == "utf-8" or enc.startswith("utf-8-"):
        return "utf-8"
    if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or \
       enc.startswith(("latin-1-", "iso-8859-1-", "iso-latin-1-")):
        return "iso-8859-1"
    return orig_enc


def detect_encoding(readline):
    """
    The detect_encoding() function is used to detect the encoding that should
    be used to decode a Python source file.  It requires one argment, readline,
    in the same way as the tokenize() generator.

    It will call readline a maximum of twice, and return the encoding used
    (as a string) and a list of any lines (left as bytes) it has read in.

    It detects the encoding from the presence of a utf-8 bom or an encoding
    cookie as specified in pep-0263.  If both a bom and a cookie are present,
    but disagree, a SyntaxError will be raised.  If the encoding cookie is an
    invalid charset, raise a SyntaxError.  Note that if a utf-8 bom is found,
    'utf-8-sig' is returned.

    If no encoding is specified, then the default of 'utf-8' will be returned.
    """
    bom_found = False
    encoding = None
    default = 'utf-8'

    def read_or_stop():
        try:
            return readline()
        except StopIteration:
            return ''

    def find_cookie(line):
        try:
            line_string = line.decode('ascii')
        except UnicodeDecodeError:
            return None

        matches = _cookie_re.findall(line_string)
        if not matches:
            return None
        encoding = _get_normal_name(matches[0])
        try:
            codec = codecs.lookup(encoding)
        except LookupError:
            # This behaviour mimics the Python interpreter
            raise SyntaxError("unknown encoding: " + encoding)

        if bom_found:
            if codec.name != 'utf-8':
                # This behaviour mimics the Python interpreter
                raise SyntaxError('encoding problem: utf-8')
            encoding += '-sig'
        return encoding

    first = read_or_stop()
    if first.startswith(codecs.BOM_UTF8):
        bom_found = True
        first = first[3:]
        default = 'utf-8-sig'
    if not first:
        return default, []

    encoding = find_cookie(first)
    if encoding:
        return encoding, [first]

    second = read_or_stop()
    if not second:
        return default, [first]

    encoding = find_cookie(second)
    if encoding:
        return encoding, [first, second]

    return default, [first, second]


def fsencode(filename):
    if isinstance(filename, str):
        return filename
    elif isinstance(filename, unicode):
        return filename.encode(sys.getfilesystemencoding())
    else:
        raise TypeError("expect bytes or str, not %s" %
                        type(filename).__name__)


try:
    from functools import wraps
except ImportError:
    def wraps(func=None):
        """No-op replacement for functools.wraps"""
        def wrapped(func):
            return func
        return wrapped


try:
    from platform import python_implementation
except ImportError:
    def python_implementation():
        """Return a string identifying the Python implementation."""
        if 'PyPy' in sys.version:
            return 'PyPy'
        if os.name == 'java':
            return 'Jython'
        if sys.version.startswith('IronPython'):
            return 'IronPython'
        return 'CPython'