Add destination time difference and live local times on trip pages

Closes #208

web_view.py

@@ -11,10 +11,13 @@ import os.path
 import sys
 import time
 import traceback
+import typing
 from collections import defaultdict
 from datetime import date, datetime, timedelta, timezone
+from zoneinfo import ZoneInfo
 
 import flask
+import pytz
 import werkzeug
 import werkzeug.debug.tbtools
 import yaml
@@ -761,6 +764,104 @@ def get_prev_current_and_next_trip(
     return (prev_trip, current_trip, next_trip)
 
 
+def _timezone_name_from_datetime(value: typing.Any) -> str | None:
+    """Get IANA timezone name from a datetime value if available."""
+    if not isinstance(value, datetime) or value.tzinfo is None:
+        return None
+
+    key = getattr(value.tzinfo, "key", None)
+    if isinstance(key, str):
+        return key
+
+    zone = getattr(value.tzinfo, "zone", None)
+    if isinstance(zone, str):
+        return zone
+
+    return None
+
+
+def _format_offset_from_bristol(offset_minutes: int) -> str:
+    """Format offset from Bristol in +/-HH:MM."""
+    if offset_minutes == 0:
+        return "Same time as Bristol"
+    sign = "+" if offset_minutes > 0 else "-"
+    hours, mins = divmod(abs(offset_minutes), 60)
+    return f"{sign}{hours:02d}:{mins:02d} vs Bristol"
+
+
+def get_destination_timezones(trip: Trip) -> list[StrDict]:
+    """Build destination timezone metadata for the trip page."""
+    per_location: dict[tuple[str, str], list[str]] = defaultdict(list)
+    for item in trip.accommodation + trip.conferences + trip.events:
+        location = item.get("location")
+        country = item.get("country")
+        if not isinstance(location, str) or not isinstance(country, str):
+            continue
+
+        key = (location, country.lower())
+        timezone_name = item.get("timezone")
+        if isinstance(timezone_name, str):
+            per_location[key].append(timezone_name)
+
+        for field in (
+            "from",
+            "to",
+            "date",
+            "start",
+            "end",
+            "attend_start",
+            "attend_end",
+        ):
+            candidate = _timezone_name_from_datetime(item.get(field))
+            if candidate:
+                per_location[key].append(candidate)
+
+    home_now = datetime.now(ZoneInfo("Europe/London"))
+    destination_times: list[StrDict] = []
+
+    for location, country in trip.locations():
+        country_code = country.alpha_2.lower()
+        key = (location, country_code)
+        timezone_name = None
+
+        for candidate in per_location.get(key, []):
+            try:
+                ZoneInfo(candidate)
+                timezone_name = candidate
+                break
+            except Exception:
+                continue
+
+        if not timezone_name:
+            country_timezones = pytz.country_timezones.get(country_code, [])
+            if len(country_timezones) == 1:
+                timezone_name = country_timezones[0]
+
+        offset_display = "Timezone unknown"
+        current_time = None
+        if timezone_name:
+            dest_now = datetime.now(ZoneInfo(timezone_name))
+            dest_offset = dest_now.utcoffset()
+            home_offset = home_now.utcoffset()
+            if dest_offset is not None and home_offset is not None:
+                offset_minutes = int((dest_offset - home_offset).total_seconds() // 60)
+                offset_display = _format_offset_from_bristol(offset_minutes)
+            current_time = dest_now.strftime("%a %H:%M:%S")
+
+        destination_times.append(
+            {
+                "location": location,
+                "country_name": country.name,
+                "country_flag": country.flag,
+                "timezone": timezone_name,
+                "offset_display": offset_display,
+                "current_time": current_time,
+            }
+        )
+
+    return destination_times
+
+
 @app.route("/trip/<start>")
 def trip_page(start: str) -> str:
     """Individual trip page."""
@@ -802,6 +903,7 @@ def trip_page(start: str) -> str:
         format_list_with_ampersand=format_list_with_ampersand,
         holidays=agenda.holidays.get_trip_holidays(trip),
         school_holidays=agenda.holidays.get_trip_school_holidays(trip),
+        destination_times=get_destination_timezones(trip),
         human_readable_delta=agenda.utils.human_readable_delta,
         trip_weather=trip_weather,
     )