# -*- coding: utf-8- -*-

# from: http://piao-tech.blogspot.no/2010/03/get-offlineimap-working-with-non-ascii.html#resources

import binascii
import codecs

# encoding

def modified_base64 (s):
  s = s.encode ('utf-16be')
  return binascii.b2a_base64(s).rstrip('\n=').replace('/', ',')

def doB64(_in, r):
  if _in:
    r.append ('&%s-' % modified_base64(''.join(_in)))
    del _in[:]

def encoder(s):
  r = []
  _in = []
  for c in s:
    ordC = ord(c)
    if 0x20 <= ordC <= 0x25 or 0x27 <= ordC <= 0x7e:
      doB64(_in, r)
      r.append (c)
    elif c == '&':
      doB64(_in, r)
      r.append ('&-')
    else:
      _in.append(c)
  doB64(_in, r)
  return (str(''.join(r)), len(s))

# decoding
def modified_unbase64(s):
  b = binascii.a2b_base64(s.replace(',', '/') + '===')
  return unicode (b, 'utf-16be')

def decoder (s):
  r = []
  decode = []
  for c in s:
    if c == '&' and not decode:
      decode.append ('&')
    elif c == '-' and decode:
      if len(decode) == 1:
        r.append('&')
      else:
        r.append(modified_unbase64(''.join(decode[1:])))
      decode = []
    elif decode:
      decode.append(c)
    else:
      r.append(c)

  if decode:
    r.append(modified_unbase64(''.join(decode[1:])))
  bin_str = ''.join(r)
  return (bin_str, len(s))

class StreamReader (codecs.StreamReader):
  def decode (self, s, errors='strict'):
    return decoder(s)

class StreamWriter (codecs.StreamWriter):
  def decode (self, s, errors='strict'):
    return encoder(s)

def imap4_utf_7(name):
  if name == 'imap4-utf-7':
    return (encoder, decoder, StreamReader, StreamWriter)

codecs.register(imap4_utf_7)