"""Implementation of reachability functionality"""

from logging import Logger
from threading import Thread
from time import sleep

from cloudsync.utils.globals import *

import requests

# REACHABILITY PARAMETERS
REACHABILITY_CHECK_PAUSE = 5
REACHABILITY_CYCLES = 3
REACHABILITY_CYCLE_PAUSE = 10


class ReachabilityProvider:

    def __init__(self, logger: Logger, url_reachability, initial_delay_s: int = 0):
        """Initialise the reachability provider.

        :param int initial_delay_s: Fleet-stagger delay applied once
            before the first probe. Zero preserves 0.5.4 behavior; a
            non-zero value prevents the PROD fleet from probing the
            reachability URL in lock-step at boot.
        """
        self.logger = logger
        self.url_reachability = url_reachability
        self.reachability = False
        self._initial_delay_s = max(0, int(initial_delay_s))
        self.thread = Thread(target=self.reachability_test, daemon=True)
        self.thread.start()

    def reachability_test(self):
        """
        Continuously monitors the connection to REACHABILITY_URL
        """
        # Optional first-probe stagger. Gated on > 0 so existing
        # tests that patch ``sleep`` to StopIteration still exercise the
        # loop body (unchanged 0.5.4 behavior when the provider is
        # constructed without a jitter).
        if self._initial_delay_s > 0:
            sleep(self._initial_delay_s)
        while True:
            headers = {
                'User-Agent': USER_AGENT,
            }

            try:
                response = requests.get(url=self.url_reachability, headers=headers, timeout=10)
                status_code = response.status_code
            except requests.exceptions.RequestException:
                status_code = INTERNAL_SERVER_ERROR

            if status_code == OK:
                if not self.reachability:
                    self.logger.info('Internet UP')
                self.reachability = True
            else:
                if self.reachability:
                    self.logger.warning('Internet DOWN')
                self.reachability = False
            sleep(REACHABILITY_CHECK_PAUSE)