from xml.etree import ElementTree

from contextlib import contextmanager

_log = logging.getLogger(__name__)

class Ledger:

    def __init__(self, ledger_file=None, ledger_bin=None):

        if ledger_file is None:

            raise ValueError('ledger_file cannot be None')

        self.ledger_bin = ledger_bin or 'ledger'

        self.ledger_file = ledger_file

        _log.info('ledger file: %s', ledger_file)

        self.locked = False

        self.ledger_process = None

    @contextmanager

    def locked_process(self):

        if self.locked:

            raise RuntimeError('The process has already been locked,'

                               ' something\'s out of order.')

            # XXX: This code has no purpose in a single-threaded process

            for i in range(1, timeout + 2):

                if i > timeout:

                    raise RuntimeError('Ledger process is already locked')

                if not self.locked:

                    break

                else:

                    _log.info('Waiting for one second... %d/%d', i, timeout)

                    time.sleep(1)

        process = self.get_process()

        self.locked = True

        _log.debug('lock enabled')

        yield process

        self.locked = False

        _log.debug('lock disabled')

    def assemble_arguments(self):

        return [