#  BSD 3-Clause License
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#  Copyright (c) 2019, Elasticsearch BV
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#  modification, are permitted provided that the following conditions are met:
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#  * Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer.
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#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
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#    contributors may be used to endorse or promote products derived from
#    this software without specific prior written permission.
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#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
#  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
#  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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from __future__ import absolute_import

import logging
import os
import threading
from timeit import default_timer

logger = logging.getLogger("elasticapm.utils.threading")


class IntervalTimer(threading.Thread):
    """
    A timer that runs a function repeatedly. In contrast to threading.Timer,
    IntervalTimer runs the given function in perpetuity or until it is cancelled.
    When run, it will wait `interval` seconds until the first execution.
    """

    def __init__(
        self, function, interval, name=None, args=(), kwargs=None, daemon=None, evaluate_function_interval=False
    ) -> None:
        """

        :param function: the function to run
        :param interval: the interval in-between invocations of the function, in milliseconds
        :param name: name of the thread
        :param args: arguments to call the function with
        :param kwargs: keyword arguments to call the function with
        :param daemon: should the thread run as a daemon
        :param evaluate_function_interval: if set to True, and the function returns a number,
               it will be used as the next interval
        """
        super(IntervalTimer, self).__init__(name=name, daemon=daemon)
        self.daemon = daemon
        self._args = args
        self._kwargs = kwargs if kwargs is not None else {}
        self._function = function
        self._interval = interval
        self._interval_done = threading.Event()
        self._evaluate_function_interval = evaluate_function_interval

    def run(self) -> None:
        execution_time = 0
        interval_override = None
        while True:
            real_interval = (interval_override if interval_override is not None else self._interval) - execution_time
            interval_completed = True
            if real_interval:
                interval_completed = self._interval_done.wait(real_interval)
            if interval_completed:
                # we've been cancelled, time to go home
                return
            start = default_timer()
            try:
                rval = self._function(*self._args, **self._kwargs)
                if self._evaluate_function_interval and isinstance(rval, (int, float)):
                    interval_override = rval
                else:
                    interval_override = None
            except Exception:
                logger.error("Exception in interval timer function", exc_info=True)

            execution_time = default_timer() - start

    def cancel(self) -> None:
        self._interval_done.set()


class ThreadManager(object):
    def __init__(self) -> None:
        self.pid = None
        self.start_stop_order = 100

    def start_thread(self, pid=None) -> None:
        if not pid:
            pid = os.getpid()
        self.pid = pid

    def stop_thread(self):
        raise NotImplementedError()

    def is_started(self, current_pid=None):
        if not current_pid:
            current_pid = os.getpid()
        return self.pid == current_pid