from __future__ import annotations

from zoneinfo import ZoneInfo, ZoneInfoNotFoundError

from django.utils import timezone


class UserTimezoneMiddleware:
    """Activate the visitor's selected timezone (defaults to UTC).

    Everything is stored in UTC; this is the only place display time is chosen,
    so a page that renders a naive local time is a bug in the template, not here.
    """

    SESSION_KEY = "user_timezone"
    DEFAULT_TIMEZONE = "UTC"

    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        tz_name = request.session.get(self.SESSION_KEY, self.DEFAULT_TIMEZONE)
        try:
            timezone.activate(ZoneInfo(tz_name))
            request.current_timezone_name = tz_name
        except (ZoneInfoNotFoundError, ValueError):
            timezone.activate(ZoneInfo(self.DEFAULT_TIMEZONE))
            request.current_timezone_name = self.DEFAULT_TIMEZONE

        response = self.get_response(request)
        timezone.deactivate()
        return response