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#!/usr/bin/env python

import sys
if sys.version_info < (2, 6):
    raise RuntimeError("Python 2.6+ is required.")

import codecs
import logging
import optparse
import os
import unittest

CRLF_OFFSET_ERROR = '\r\0\r\n\0'
CRLF_OFFSET_FIX = '\r\0\n\0'

def fsckByteString(content=None, log=None):
  if not content:
    raise ArgumentException('Content must not be empty.')
  
  if content.startswith(codecs.BOM_UTF16):
    if log: log.info('Detected UTF-16 BOM.')

    if CRLF_OFFSET_ERROR in content:
      if log: log.error('Byte shift due to improper line ending conversion!')
      if log: log.info('Correcting line endings...')
      content = content.replace(CRLF_OFFSET_ERROR, CRLF_OFFSET_FIX)
    
    if log: log.info('Converting to UTF-8...')
    return content.decode("utf16").encode("utf8")

  if content.startswith(codecs.BOM_UTF8):
    if log: log.warn('Detected unneccessary UTF-8 BOM.')
    if log: log.info('Removing BOM...')

    return content[len(codecs.BOM_UTF8):]
  
  if log: log.info('No action required.')
  return content


class fscker(unittest.TestCase):
  DATA = "simple\r\ntest\r\nof\r\nencodings"
  EXPECTED = DATA.encode("utf8")

  def test_valid_utf8(self):
    value  = self.DATA.encode("utf8")
    actual = fsckByteString(value)
    self.assertEqual(self.EXPECTED, actual)
  
  def test_valid_utf8_with_bom(self):
    value  = codecs.BOM_UTF8 + self.DATA.encode("utf8")
    actual = fsckByteString(value)
    self.assertEqual(self.EXPECTED, actual)
  
  def test_valid_utf16_to_utf8(self):
    value  = self.DATA.encode("utf16")
    actual = fsckByteString(value)
    self.assertEqual(self.EXPECTED, actual)
  
  def test_invalid_utf16_to_utf8(self):
    value  = self.DATA.encode("utf16").replace('\n', '\r\n')
    actual = fsckByteString(value)
    self.assertEqual(self.EXPECTED, actual)


if __name__ == '__main__':
  parser = optparse.OptionParser(usage='Usage: %prog [options] file1 [... fileN]')
  parser.add_option('--test', dest='is_testing', action='store_true', default=False, help='run test suite')

  options, files = parser.parse_args()
  logging.basicConfig(format='%(name)s  %(levelname)s: %(message)s', level=logging.INFO)

  print
  if options.is_testing:
    unittest.TextTestRunner(verbosity=2).run(unittest.TestSuite(
      unittest.defaultTestLoader.loadTestsFromTestCase(fscker)
    ))
  elif files:
    for fname in files:
      log = logging.getLogger(os.path.basename(fname))
      try:
        content = None
        with open(fname, 'rb') as f:
          content = fsckByteString(f.read(), log)
        with open(fname, 'wb') as f:
          f.write(content)
      except Exception, e:
        log.error('"%s" could not be checked.', fname)
        log.error(e)
      print
  else:
    parser.print_help()