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from __future__ import absolute_import

from txaio._version import __version__
from txaio.interfaces import IFailedFuture, ILogger

version = __version__

# This is the API
# see tx.py for Twisted implementation
# see aio.py for asyncio/trollius implementation


class _Config(object):
    """
    This holds all valid configuration options, accessed as
    class-level variables. For example, if you were using asyncio:

    .. sourcecode:: python

        txaio.config.loop = asyncio.get_event_loop()

    ``loop`` is populated automatically (while importing one of the
    framework-specific libraries) but can be changed before any call
    into this library. Currently, it's only used by :meth:`call_later`
    If using asyncio, you must set this to an event-loop (by default,
    we use asyncio.get_event_loop). If using Twisted, set this to a
    reactor instance (by default we "from twisted.internet import
    reactor" on the first call to call_later)
    """
    #: the event-loop object to use
    loop = None


__all__ = (
    'with_config',              # allow mutliple custom configurations at once
    'using_twisted',            # True if we're using Twisted
    'using_asyncio',            # True if we're using asyncio
    'use_twisted',              # sets the library to use Twisted, or exception
    'use_asyncio',              # sets the library to use asyncio, or exception

    'config',                   # the config instance, access via attributes

    'create_future',            # create a Future (can be already resolved/errored)
    'create_future_success',
    'create_future_error',
    'create_failure',           # return an object implementing IFailedFuture
    'as_future',                # call a method, and always return a Future
    'is_future',                # True for Deferreds in tx and Futures, @coroutines in asyncio
    'reject',                   # errback a Future
    'resolve',                  # callback a Future
    'cancel',                   # cancel a Future
    'add_callbacks',            # add callback and/or errback
    'gather',                   # return a Future waiting for several other Futures
    'is_called',                # True if the Future has a result

    'call_later',               # call the callback after the given delay seconds

    'failure_message',          # a printable error-message from a IFailedFuture
    'failure_traceback',        # returns a traceback instance from an IFailedFuture
    'failure_format_traceback',     # a string, the formatted traceback

    'make_batched_timer',       # create BatchedTimer/IBatchedTimer instances

    'make_logger',              # creates an object implementing ILogger
    'start_logging',            # initializes logging (may grab stdin at this point)
    'set_global_log_level',     # Set the global log level
    'get_global_log_level',     # Get the global log level
    'add_log_categories',

    'IFailedFuture',            # describes API for arg to errback()s
    'ILogger',                  # API for logging

    'sleep',                    # little helper for inline sleeping
)


_explicit_framework = None


def use_twisted():
    global _explicit_framework
    if _explicit_framework is not None and _explicit_framework != 'twisted':
        raise RuntimeError("Explicitly using '{}' already".format(_explicit_framework))
    _explicit_framework = 'twisted'
    from txaio import tx
    _use_framework(tx)
    import txaio
    txaio.using_twisted = True
    txaio.using_asyncio = False


def use_asyncio():
    global _explicit_framework
    if _explicit_framework is not None and _explicit_framework != 'asyncio':
        raise RuntimeError("Explicitly using '{}' already".format(_explicit_framework))
    _explicit_framework = 'asyncio'
    from txaio import aio
    _use_framework(aio)
    import txaio
    txaio.using_twisted = False
    txaio.using_asyncio = True


def _use_framework(module):
    """
    Internal helper, to set this modules methods to a specified
    framework helper-methods.
    """
    import txaio
    for method_name in __all__:
        if method_name in ['use_twisted', 'use_asyncio']:
            continue
        setattr(txaio, method_name,
                getattr(module, method_name))


# use the "un-framework", which is neither asyncio nor twisted and
# just throws an exception -- this forces you to call .use_twisted()
# or .use_asyncio() to use the library.
from txaio import _unframework  # noqa
_use_framework(_unframework)
