#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from time import sleep

import pandas as pd
from catalyst.gens.sim_engine import (
    BAR,
    SESSION_START
)
from logbook import Logger

from catalyst.constants import LOG_LEVEL

log = Logger('ExchangeClock', level=LOG_LEVEL)


class SimpleClock(object):
    """Realtime clock for live trading.

    This class is a drop-in replacement for
    :class:`zipline.gens.sim_engine.MinuteSimulationClock`.

    This is a stripped down version because crypto exchanges run around the clock.

    The :param:`time_skew` parameter represents the time difference between
    the Broker and the live trading machine's clock.
    """

    def __init__(self, sessions, time_skew=pd.Timedelta("0s")):

        self.sessions = sessions
        self.time_skew = time_skew
        self._last_emit = None
        self._before_trading_start_bar_yielded = True

    def __iter__(self):
        yield pd.Timestamp.utcnow(), SESSION_START

        while True:
            current_time = pd.Timestamp.utcnow()
            current_minute = current_time.floor('1 min')

            if self._last_emit is None or current_minute > self._last_emit:
                log.debug('emitting minutely bar: {}'.format(current_minute))

                self._last_emit = current_minute
                yield current_minute, BAR
            else:
                sleep(1)