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from __future__ import absolute_import

import abc
import six

#: all the log-levels that txaio recognizes
log_levels = [
    'critical',
    'error',
    'warn',
    'info',
    'debug',
    'trace',
]


@six.add_metaclass(abc.ABCMeta)
class ILogger(object):
    """
    This defines the methods you can call on the object returned from
    :meth:`txaio.make_logger` -- although the actual object may have
    additional methods, you should *only* call the methods listed
    here.

    All the log methods have the same signature, they just differ in
    what "log level" they represent to the handlers/emitters. The
    ``message`` argument is a format string using `PEP3101
    <https://www.python.org/dev/peps/pep-3101/>`_-style references to
    things from the ``kwargs``. Note that there are also the following
    keys added to the ``kwargs``: ``log_time`` and ``log_level``.

    For example::

        class MyThing(object):
            log = txaio.make_logger()

            def something_interesting(self, things=dict(one=1, two=2)):
                try:
                    self.log.debug("Called with {things[one]}", things=things)
                    result = self._method_call()
                    self.log.info("Got '{result}'.", result=result)
                except Exception:
                    fail = txaio.create_failure()
                    self.log.critical(txaio.failure_format_traceback(fail))

    The philsophy behind txaio's interface is fairly similar to
    Twisted's logging APIs after version 15. See `Twisted's
    documentation
    <http://twistedmatrix.com/documents/current/core/howto/logger.html>`_
    for details.
    """

# stdlib notes:
# levels:
#   CRITICAL 50
#   ERROR 40
#   WARNING 30
#   INFO 20
#   DEBUG 10
#   NOTSET 0


# NOTES
# things in Twisted's event:
# - log_level
# - log_failure (sometimes?)
# - log_format (can be None)
# - log_source (sometimes? no, always, but sometimes None)
# - log_namespace
#
# .warn not warning!

    def critical(self, message, **kwargs):
        "log a critical-level message"

    def error(self, message, **kwargs):
        "log a error-level message"

    def warn(self, message, **kwargs):
        "log a error-level message"

    def info(self, message, **kwargs):
        "log an info-level message"

    def debug(self, message, **kwargs):
        "log an debug-level message"

    def trace(self, message, **kwargs):
        "log a trace-level message"


@six.add_metaclass(abc.ABCMeta)
class IFailedFuture(object):
    """
    This defines the interface for a common object encapsulating a
    failure from either an asyncio task/coroutine or a Twisted
    Deferred.

    An instance implementing this interface is given to any
    ``errback`` callables you provide via :meth:`txaio.add_callbacks`

    In your errback you can extract information from an IFailedFuture
    with :meth:`txaio.failure_message` and
    :meth:`txaio.failure_traceback` or use ``.value`` to get the
    Exception instance.

    Depending on other details or methods will probably cause
    incompatibilities between asyncio and Twisted.
    """

    @abc.abstractproperty
    def value(self):
        """
        An actual Exception instance. Same as the second item returned from
        ``sys.exc_info()``
        """
