65 lines
2 KiB
Python
65 lines
2 KiB
Python
from functools import lru_cache
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from datetime import tzinfo
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from typing import Sequence
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import pytz # type: ignore
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def user_forced() -> Sequence[str]:
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# conversion from abbreviations is always ambiguous
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# https://stackoverflow.com/questions/36067621/python-all-possible-timezone-abbreviations-for-given-timezone-name-and-vise-ve
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try:
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from my.config import time as user_config
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return user_config.tz.force_abbreviations # type: ignore[attr-defined]
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except:
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# todo log/apply policy
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return []
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@lru_cache(1)
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def _abbr_to_timezone_map():
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# also force UTC to always correspond to utc
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# this makes more sense than Zulu it ends up by default
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timezones = pytz.all_timezones + ['UTC'] + list(user_forced())
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res = {}
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for tzname in timezones:
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tz = pytz.timezone(tzname)
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infos = getattr(tz, '_tzinfos', []) # not sure if can rely on attr always present?
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for info in infos:
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abbr = info[-1]
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# todo could support this with a better error handling strategy?
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# otz = res.get(abbr, tz)
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# if otz != tz:
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# raise RuntimeError(abbr, tz, otz)
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res[abbr] = tz
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# ugh. also necessary, e.g. for Zulu?? why is it not in _tzinfos?
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# note: somehow this is not the same as the tzname!
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tzn = getattr(tz, '_tzname', None)
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if tzn is not None:
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res[tzn] = tz
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return res
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# todo dammit, lru_cache interferes with mypy?
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@lru_cache(None)
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def abbr_to_timezone(abbr: str) -> tzinfo:
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return _abbr_to_timezone_map()[abbr]
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def zone_to_countrycode(zone: str) -> str:
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# todo make optional?
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return _zones_to_countrycode()[zone]
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@lru_cache(1)
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def _zones_to_countrycode():
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# https://stackoverflow.com/a/13020785/706389
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res = {}
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for countrycode, timezones in pytz.country_timezones.items():
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for timezone in timezones:
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res[timezone] = countrycode
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return res
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# todo stuff here could be a bit more defensive? e.g. dependent on policy
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