# Base class for import tools written in Python.
#
# Copyright (C) 2014  Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.


import logging
import os
import sys


class ImportException(Exception):
    pass


class ImportExtension(object):
    '''A base class for import extensions.

    A subclass should subclass this class, and add a ``process_args`` method.

    Note that it is not necessary to subclass this class for import extensions.
    This class is here just to collect common code.

    '''

    def __init__(self):
        self.setup_logging()

    def setup_logging(self):
        '''Direct all logging output to MORPH_LOG_FD, if set.

        This file descriptor is read by Morph and written into its own log
        file.

        This overrides cliapp's usual configurable logging setup.

        '''
        log_write_fd = int(os.environ.get('MORPH_LOG_FD', 0))

        if log_write_fd == 0:
            return

        formatter = logging.Formatter('%(message)s')

        handler = logging.StreamHandler(os.fdopen(log_write_fd, 'w'))
        handler.setFormatter(formatter)

        logger = logging.getLogger()
        logger.addHandler(handler)
        logger.setLevel(logging.DEBUG)

    def process_args(self, args):
        raise NotImplementedError()

    def run(self):
        try:
            self.process_args(sys.argv[1:])
        except ImportException as e:
            sys.stderr.write('ERROR: %s' % e.message)
            sys.exit(1)