# Copyright (C) 2002-2007 Python Software Foundation
# Author: Ben Gertzfield, Barry Warsaw
# Contact: email-sig@python.org

"""Header encoding and decoding functionality."""

__all__ = [
    'Header',
    'decode_header',
    'make_header',
    ]

import re
import binascii

import email.quoprimime
import email.base64mime

from email.errors import HeaderParseError
from email import charset as _charset
Charset = _charset.Charset

NL = '\n'
SPACE = ' '
BSPACE = b' '
SPACE8 = ' ' * 8
EMPTYSTRING = ''
MAXLINELEN = 78
FWS = ' \t'

USASCII = Charset('us-ascii')
UTF8 = Charset('utf-8')

# Match encoded-word strings in the form =?charset?q?Hello_World?=
ecre = re.compile(r'''
  =\?                   # literal =?
  (?P<charset>[^?]*?)   # non-greedy up to the next ? is the charset
  \?                    # literal ?
  (?P<encoding>[qQbB])  # either a "q" or a "b", case insensitive
  \?                    # literal ?
  (?P<encoded>.*?)      # non-greedy up to the next ?= is the encoded string
  \?=                   # literal ?=
  ''', re.VERBOSE | re.MULTILINE)

# Field name regexp, including trailing colon, but not separating whitespace,
# according to RFC 2822.  Character range is from tilde to exclamation mark.
# For use with .match()
fcre = re.compile(r'[\041-\176]+:$')

# Find a header embedded in a putative header value.  Used to check for
# header injection attack.
_embedded_header = re.compile(r'\n[^ \t]+:')