#!/usr/bin/env python
import base64
import os
import subprocess
import sys
import tempfile

_PATCHHDR = b'# HG changeset patch'

_BASE64_MAGIC = b'Content-Transfer-Encoding: base64'


def main(argv):
    tf = tempfile.NamedTemporaryFile(suffix='.diff')
    d = sys.stdin.buffer.read()
    if _PATCHHDR in d:
        junk, d = d.split(_PATCHHDR, 1)
        d = _PATCHHDR + d
    elif _BASE64_MAGIC in d:
        junk, d = d.split('\n\n', 1)
        d = d.decode('base64')
    tf.write(d)
    tf.flush()
    subprocess.check_call([os.environ['EDITOR'], tf.name],
                          stdout=sys.stderr)
    sys.stdout.buffer.write(open(tf.name, 'rb').read())


if __name__ == '__main__':
    main(argv=sys.argv)