add time helpers to MacPublicState for views

src/capport/cptypes.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import capport.utils.zoneinfo
 import dataclasses
 import datetime
 import ipaddress
@@ -79,6 +80,18 @@ class MacPublicState:
     def captive(self) -> bool:
         return not self.allowed
 
+    @property
+    def allowed_remaining_duration(self) -> str:
+        mm, ss = divmod(self.allowed_remaining, 60)
+        hh, mm = divmod(mm, 60)
+        return f'{hh}:{mm:02}:{ss:02}'
+
+    @property
+    def allowed_until(self) -> typing.Optional[datetime.datetime]:
+        zone = capport.utils.zoneinfo.get_local_timezone()
+        now = datetime.datetime.now(zone).replace(microsecond=0)
+        return now + datetime.timedelta(seconds=self.allowed_remaining)
+
     def to_rfc8908(self, config: Config) -> quart.Response:
         response: typing.Dict[str, typing.Any] = {
             'user-portal-url': quart.url_for('index', _external=True),

src/capport/utils/zoneinfo.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+import typing
+import zoneinfo
+
+
+_zoneinfo: typing.Optional[zoneinfo.ZoneInfo] = None
+
+
+def get_local_timezone():
+    global _zoneinfo
+    if not _zoneinfo:
+        try:
+            with open('/etc/timezone') as f:
+                key = f.readline().strip()
+                _zoneinfo = zoneinfo.ZoneInfo(key)
+        except (OSError, zoneinfo.ZoneInfoNotFoundError):
+            _zoneinfo = zoneinfo.ZoneInfo('UTC')
+    return _zoneinfo