import logging
from datetime import datetime, timedelta
from threading import Timer
from time import sleep

import pytz


# Provides a timed cleanup of the spot list.
class CleanupTimer:

    # Constructor
    def __init__(self, spots, alerts, cleanup_interval):
        self.spots = spots
        self.alerts = alerts
        self.cleanup_interval = cleanup_interval
        self.cleanup_timer = None
        self.last_cleanup_time = datetime.min.replace(tzinfo=pytz.UTC)
        self.status = "Starting"

    # Start the cleanup timer
    def start(self):
        self.cleanup()

    # Stop any threads and prepare for application shutdown
    def stop(self):
        self.cleanup_timer.cancel()

    # Perform cleanup and reschedule next timer
    def cleanup(self):
        try:
            # Perform cleanup
            self.spots.expire()
            self.alerts.expire()

            # Alerts can persist in the system for a while, so we want to explicitly clean up any alerts that have
            # expired
            for id in list(self.alerts.iterkeys()):
                alert = self.alerts[id]
                if alert.expired():
                    self.alerts.evict(id)

            self.status = "OK"
            self.last_cleanup_time = datetime.now(pytz.UTC)

        except Exception as e:
            self.status = "Error"
            logging.exception("Exception in Cleanup thread")
            sleep(1)

        self.cleanup_timer = Timer(self.cleanup_interval, self.cleanup)
        self.cleanup_timer.start()