"""allow bash-completion for argparse with argcomplete if installed
needs argcomplete>=0.5.6 for python 3.2/3.3 (older versions fail
to find the magic string, so _ARGCOMPLETE env. var is never set, and
this does not need special code.

argcomplete does not support python 2.5 (although the changes for that
are minor).

Function try_argcomplete(parser) should be called directly before
the call to ArgumentParser.parse_args().

The filescompleter is what you normally would use on the positional
arguments specification, in order to get "dirname/" after "dirn<TAB>"
instead of the default "dirname ":

   optparser.add_argument(Config._file_or_dir, nargs='*'
                               ).completer=filescompleter

Other, application specific, completers should go in the file
doing the add_argument calls as they need to be specified as .completer
attributes as well. (If argcomplete is not installed, the function the
attribute points to will not be used).

---
To include this support in another application that has setup.py generated
scripts:
- add the line:
    # PYTHON_ARGCOMPLETE_OK
  near the top of the main python entry point
- include in the file calling parse_args():
    from _argcomplete import try_argcomplete, filescompleter
   , call try_argcomplete just before parse_args(), and optionally add
   filescompleter to the positional arguments' add_argument()
If things do not work right away:
- switch on argcomplete debugging with (also helpful when doing custom
  completers):
    export _ARC_DEBUG=1
- run:
    python-argcomplete-check-easy-install-script $(which appname)
    echo $?
  will echo 0 if the magic line has been found, 1 if not
- sometimes it helps to find early on errors using:
    _ARGCOMPLETE=1 _ARC_DEBUG=1 appname
  which should throw a KeyError: 'COMPLINE' (which is properly set by the
  global argcomplete script).
   
"""

import sys
import os

if os.environ.get('_ARGCOMPLETE'):
    # argcomplete 0.5.6 is not compatible with python 2.5.6: print/with/format
    if sys.version_info[:2] < (2, 6):
        sys.exit(1)
    try:
        import argcomplete.completers
    except ImportError:
        sys.exit(-1)
    filescompleter = argcomplete.completers.FilesCompleter()

    def try_argcomplete(parser):
        argcomplete.autocomplete(parser)
else:
    def try_argcomplete(parser): pass
    filescompleter = None