import os
import time
from datetime import timedelta
from typing import Any, Dict

from django.core.management.base import BaseCommand
from django.utils.timezone import now as timezone_now

from analytics.lib.counts import COUNT_STATS, CountStat
from analytics.models import installation_epoch
from zerver.lib.timestamp import TimezoneNotUTCException, floor_to_day, floor_to_hour, verify_UTC
from zerver.models import Realm

states = {
    0: "OK",
    1: "WARNING",
    2: "CRITICAL",
    3: "UNKNOWN",
}


class Command(BaseCommand):
    help = """Checks FillState table.

    Run as a cron job that runs every hour."""

    def handle(self, *args: Any, **options: Any) -> None:
        fill_state = self.get_fill_state()
        status = fill_state['status']
        message = fill_state['message']

        state_file_path = "/var/lib/nagios_state/check-analytics-state"
        state_file_tmp = state_file_path + "-tmp"

        with open(state_file_tmp, "w") as f:
            f.write(f"{int(time.time())}|{status}|{states[status]}|{message}\n")
        os.rename(state_file_tmp, state_file_path)

    def get_fill_state(self) -> Dict[str, Any]:
        if not Realm.objects.exists():
            return {'status': 0, 'message': 'No realms exist, so not checking FillState.'}

        warning_unfilled_properties = []
        critical_unfilled_properties = []
        for property, stat in COUNT_STATS.items():
            last_fill = stat.last_successful_fill()
            if last_fill is None:
                last_fill = installation_epoch()
            try:
                verify_UTC(last_fill)
            except TimezoneNotUTCException:
                return {'status': 2, 'message': f'FillState not in UTC for {property}'}

            if stat.frequency == CountStat.DAY:
                floor_function = floor_to_day
                warning_threshold = timedelta(hours=26)
                critical_threshold = timedelta(hours=50)
            else:  # CountStat.HOUR
                floor_function = floor_to_hour
                warning_threshold = timedelta(minutes=90)
                critical_threshold = timedelta(minutes=150)

            if floor_function(last_fill) != last_fill:
                return {
                    'status': 2,
                    'message': f'FillState not on {stat.frequency} boundary for {property}',
                }

            time_to_last_fill = timezone_now() - last_fill
            if time_to_last_fill > critical_threshold:
                critical_unfilled_properties.append(property)
            elif time_to_last_fill > warning_threshold:
                warning_unfilled_properties.append(property)

        if len(critical_unfilled_properties) == 0 and len(warning_unfilled_properties) == 0:
            return {'status': 0, 'message': 'FillState looks fine.'}
        if len(critical_unfilled_properties) == 0:
            return {
                'status': 1,
                'message': 'Missed filling {} once.'.format(
                    ', '.join(warning_unfilled_properties),
                ),
            }
        return {
            'status': 2,
            'message': 'Missed filling {} once. Missed filling {} at least twice.'.format(
                ', '.join(warning_unfilled_properties),
                ', '.join(critical_unfilled_properties),
            ),
        }