#!/usr/bin/python
import argparse
import configparser
import logging
import os
import shlex
import subprocess
import sys


class BackupError(Exception):
    '''Raised when an error occurs backing up an item'''


class Backup(object):

    RSYNC = os.environ.get('RSYNC', 'rsync')
    RSYNC_DEFAULT_ARGS = ['-aO', '--partial', '--delete']
    RSYNC_EXTRA_ARGS = shlex.split(os.environ.get('RSYNC_EXTRA_ARGS', ''))

    DEFAULT_CONFIG_FILENAME = 'backups.ini'

    log = logging.getLogger('backup')

    def __init__(self, destination, config=None, pretend=False):
        self.config = configparser.ConfigParser()
        print(config)
        if not config:
            config = open(self.default_config)
        self.config.read_file(config)
        self.config.filename = config.name
        self.destination = destination
        self.pretend = pretend
        self.stdout = sys.stdout
        self.stderr = sys.stderr

    @property
    def default_config(self):
        try:
            config_dir = os.environ['XDG_CONFIG_DIR']
        except KeyError:
            config_dir = os.path.expanduser('~/.config')
        return os.path.join(config_dir, self.DEFAULT_CONFIG_FILENAME)

    def logsetup(self, log_file=None, log_level='INFO'):
        if not log_file:
            return
        logger = logging.getLogger()
        logger.setLevel(logging.NOTSET)
        if log_file in ('-', '/dev/stdout', '<stdout>'):
            handler = logging.StreamHandler(sys.stdout)
        elif log_file in ('/dev/stderr', '<stderr>'):
            handler = logging.StreamHandler(sys.stderr)
        else:
            handler = logging.FileHandler(log_file)
        handler.setFormatter(logging.Formatter(
            '%(asctime)s [%(name)s] %(levelname)s %(message)s'))
        handler.setLevel(getattr(logging, log_level, logging.INFO))
        logger.addHandler(handler)
        self.stdout = self.stderr = handler.stream

    def backup_all(self, include=None, exclude=None):
        success = True
        self.log.info('Starting backup')
        if self.pretend:
            self.log.warning('Pretend mode: no files will be copied!')
        for section in self.config:
            if section != self.config.default_section:
                if exclude and section in exclude:
                    self.log.debug('Excluded section {}'.format(section))
                    continue
                if include and section not in include:
                    self.log.debug('Section {} not included'.format(section))
                    continue
                try:
                    self.backup(section)
                except BackupError as e:
                    self.log.error('{}'.format(e))
                    success = False
                except:
                    self.log.exception(
                        'Unexpected error backing up {}'.format(section))
                    success = False
        if success:
            self.log.info('Backup completed successfully')
        else:
            self.log.warning('Backup completed with at least one error')
        return success

    def backup(self, section):
        log = logging.getLogger('backup.{}'.format(section))
        try:
            item = self.config[section]
        except KeyError:
            raise BackupError('Unknown backup item {}'.format(section))

        try:
            source = item['source']
        except KeyError:
            raise BackupError('Missing source for {}'.format(s.name))
        try:
            destination = item['destination']
        except KeyError:
            src_path = source.split(':', 1)[-1]
            if src_path.endswith('/'):
                src_path = src_path.rstrip('/')
            destination = os.path.basename(src_path)
        destination = os.path.join(self.destination, destination)

        args = [self.RSYNC]
        args.extend(self.RSYNC_DEFAULT_ARGS)
        args.extend(self.RSYNC_EXTRA_ARGS)
        try:
            exclude = item['exclude']
        except KeyError:
            pass
        else:
            for e in shlex.split(exclude):
                args.extend(('--exclude', e))
        args.extend((source, destination))
        if self.pretend:
            args.append('-n')
        log.info('Backing up {} to {}'.format(source, destination))
        self._run(*args)
        log.info('Backup complete')

    def _run(self, *cmd):
        self.log.debug('Running command: {}'.format(' '.join(cmd)))
        try:
            subprocess.check_call(cmd, stdin=open(os.devnull),
                                  stdout=self.stdout, stderr=self.stderr)
        except (OSError, subprocess.CalledProcessError) as e:
            raise BackupError('Error executing rsync: {}'.format(e))
        except KeyboardInterrupt:
            raise BackupError('rsync interrupted')


def _parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('--log-file', '-l', default='-', metavar='FILENAME',
                        help='Log file path')
    parser.add_argument('--log-level', '-D', default='INFO', metavar='LEVEL',
                        help='Log level')
    parser.add_argument('--quiet', '-q', action='store_true', default=False,
                        help='Do not print informational messages')
    parser.add_argument('--pretend', '-p', action='store_true', default=False,
                        help='Execute a dry run')
    parser.add_argument('--include', '-I', action='append',
                        help='Only back up specific items')
    parser.add_argument('--exclude', '-X', action='append',
                        help='Do not back up specific items')
    parser.add_argument('--config', '-c', type=argparse.FileType('r'),
                        metavar='FILENAME',
                        help='Path to configuration file')
    parser.add_argument('destination',
                        help='Backup destination directory')
    return parser.parse_args()


def main():
    args = _parse_args()
    backup = Backup(args.destination, args.config, args.pretend)
    if not args.quiet:
        print('Backing up to {} using configuration from {}'.format(
            args.destination, backup.config.filename))
    backup.logsetup(args.log_file, args.log_level)
    if not backup.backup_all(args.include, args.exclude):
        sys.stderr.write('Errors occurred during backup\n')
        if args.log_file and args.log_file != '-':
            sys.stderr.write('See {} for details\n'.format(args.log_file))
        raise SystemExit(1)
    if not args.quiet:
        print('Backup completed successfully')


if __name__ == '__main__':
    main()