Backend/events: Add GetEventCalendarFile API

app/backend/src/couchers/email/calendar_events.py

@@ -1,57 +1,68 @@
+from datetime import UTC, datetime
 from email.headerregistry import Address
+from typing import Literal
+from zoneinfo import ZoneInfo
 
-from ics import Calendar, Event
+from ics import Calendar, Event, Geo
 from ics.grammar.parse import ContentLine  # type: ignore[import-untyped]
 
 from couchers import urls
 from couchers.config import config
 from couchers.email.locales import get_emails_i18next
 from couchers.i18n import LocalizationContext
+from couchers.markup import markdown_to_plaintext
+from couchers.proto import events_pb2, messages_pb2, requests_pb2
 from couchers.proto.internal.jobs_pb2 import EmailPart
-from couchers.proto.requests_pb2 import HostRequest
+from couchers.utils import now, to_aware_datetime
 
 HOST_REQUEST_ICS_FILENAME = "host_request.ics"
 
 
 def create_host_request_attachment(
-    host_request: HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
+    host_request: requests_pb2.HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
 ) -> EmailPart:
-    calendar = create_host_request_calendar(host_request, other_name, hosting, loc_context)
-    return calendar_to_attachment(calendar, HOST_REQUEST_ICS_FILENAME)
+    calendar = create_host_request_ics_calendar(host_request, other_name, hosting, loc_context)
+    return ics_calendar_to_attachment(calendar, HOST_REQUEST_ICS_FILENAME)
 
 
-def create_host_request_calendar(
-    host_request: HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
+def create_host_request_ics_calendar(
+    host_request: requests_pb2.HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
 ) -> Calendar:
-    event = create_host_request_event(host_request, other_name, hosting, loc_context)
+    event = create_host_request_ics_event(host_request, other_name, hosting, loc_context)
 
     # METHOD:PUBLISH means this is part of a stream of calendar event information.
     # It allows for later cancellation, and doesn't expose accept/decline functionality.
-    return event_to_calendar(event, "PUBLISH", loc_context)
+    # METHOD:CANCEL might leave the event in cancelled state or not work.
+    return ics_event_to_calendar(event, "PUBLISH", loc_context)
 
 
-def create_host_request_event(
-    host_request: HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext, sequence: int = 0
+def create_host_request_ics_event(
+    host_request: requests_pb2.HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
 ) -> Event:
     """Creates an ics event for a host request."""
 
     event = Event()
-    event.uid = get_host_request_event_uid(host_request.host_request_id)
-
-    # Explicitly allow later sequencing of a cancellation with SEQUENCE:1
-    event.extra.append(ContentLine(name="SEQUENCE", value=str(sequence)))
+    event.uid = _event_uid(host_request.host_request_id, kind="host_request")
+    _set_sequence_timestamp(event, now())
 
+    title: str
     if hosting:
-        event.name = loc_context.localize_string(
+        title = loc_context.localize_string(
             "calendar_events.host_requests.title_host", i18next=get_emails_i18next(), substitutions={"name": other_name}
         )
     else:
-        event.name = loc_context.localize_string(
+        title = loc_context.localize_string(
             "calendar_events.host_requests.title_surfer",
             i18next=get_emails_i18next(),
             substitutions={"name": other_name},
         )
 
+    event.name = _final_title(
+        title,
+        loc_context,
+        is_cancelled=host_request.status == messages_pb2.HostRequestStatus.HOST_REQUEST_STATUS_CANCELLED,
+    )
+
     # Our to_date is inclusive, iCalendar's DTEND is exclusive (for full-day events)
     # make_all_day will adjust the end date by one day accordingly.
     event.begin = host_request.from_date
@@ -64,32 +75,85 @@ def create_host_request_event(
     # Google Calendar™ will hide the URL if there is a location, so also include it in the description
     event.description = event.url
 
+    if host_request.status == messages_pb2.HostRequestStatus.HOST_REQUEST_STATUS_CANCELLED:
+        event.status = "CANCELLED"
+
     return event
 
 
-def create_host_request_cancellation_attachment(
-    host_request: HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
-) -> EmailPart:
-    calendar = create_host_request_cancellation_calendar(host_request, other_name, hosting, loc_context)
-    return calendar_to_attachment(calendar, HOST_REQUEST_ICS_FILENAME)
+def create_event_ics_calendar(event: events_pb2.Event, loc_context: LocalizationContext) -> Calendar:
+    ics_event = create_event_ics_event(event, loc_context)
 
+    # METHOD:PUBLISH means this is part of a stream of calendar event information.
+    # It allows for later cancellation, and doesn't expose accept/decline functionality.
+    return ics_event_to_calendar(ics_event, "PUBLISH", loc_context)
 
-def create_host_request_cancellation_calendar(
-    host_request: HostRequest, other_name: str, hosting: bool, loc_context: LocalizationContext
-) -> Calendar:
-    event = create_host_request_event(host_request, other_name, hosting, loc_context, sequence=1)
-    event.name = loc_context.localize_string(
-        "calendar_events.title_cancelled", i18next=get_emails_i18next(), substitutions={"title": event.name}
-    )
-    event.status = "CANCELLED"
 
-    # METHOD:PUBLISH means this is part of a stream of calendar event information.
-    # Gmail™ will immediately remove the event from the user's calendar.
-    # METHOD:CANCEL might leave the event in cancelled state or not work.
-    return event_to_calendar(event, "PUBLISH", loc_context)
+def create_event_ics_event(event: events_pb2.Event, loc_context: LocalizationContext) -> Event:
+    """Creates an ics event for a host request."""
+
+    ics_event = Event()
+    ics_event.uid = _event_uid(event.event_id, kind="event")
+    ics_event.name = _final_title(event.title, loc_context, is_cancelled=event.is_cancelled)
+
+    last_update_datetime = to_aware_datetime(event.created if event.last_edited.seconds == 0 else event.last_edited)
+    ics_event.last_modified = last_update_datetime
+    _set_sequence_timestamp(ics_event, last_update_datetime)
 
+    timezone = ZoneInfo(event.timezone)
+    _set_datetime_with_timezone(ics_event, "DTSTART", to_aware_datetime(event.start_time).astimezone(timezone))
+    _set_datetime_with_timezone(ics_event, "DTEND", to_aware_datetime(event.end_time).astimezone(timezone))
 
-def event_to_calendar(event: Event, method: str | None, loc_context: LocalizationContext) -> Calendar:
+    ics_event.location = event.location.address
+    ics_event.geo = Geo(event.location.lat, event.location.lng)
+    url = urls.event_link(occurrence_id=event.event_id, slug=event.slug)
+    ics_event.url = url
+    # Google Calendar™ will hide the URL if there is a location, so also include it in the description
+    ics_event.description = markdown_to_plaintext(event.content) + "\n\n" + url
+
+    if event.is_cancelled:
+        ics_event.status = "CANCELLED"
+
+    return ics_event
+
+
+def _final_title(title: str, loc_context: LocalizationContext, *, is_cancelled: bool) -> str:
+    if is_cancelled:
+        title = loc_context.localize_string(
+            "calendar_events.title_cancelled", i18next=get_emails_i18next(), substitutions={"title": title}
+        )
+    return title
+
+
+def _event_uid(item_id: int, *, kind: Literal["host_request"] | Literal["event"]) -> str:
+    uid_domain = Address(addr_spec=config.NOTIFICATION_EMAIL_ADDRESS).domain
+    return f"{kind}.{item_id}@{uid_domain}"
+
+
+def _set_sequence_timestamp(event: Event, dt: datetime) -> None:
+    # SEQUENCE is 32-bit, so only support second granularity to avoid overflows
+    # A better implementation would need to reply on a stored sequence number.
+    timestamp = round(dt.timestamp())
+    event.extra.append(ContentLine(name="SEQUENCE", value=str(timestamp)))
+
+
+def _set_datetime_with_timezone(event: Event, name: str, dt: datetime) -> None:
+    """
+    Adds a property whose value is a datetime with a timezone.
+    Working around that ics's native Event.begin/end properties don't encode the timezone.
+    """
+    datetime_format = "%Y%m%dT%H%M%S"
+    params: dict[str, list[str]] = {}
+    value: str
+    if isinstance(dt.tzinfo, ZoneInfo) and dt.tzinfo.key != "Etc/UTC":
+        params["TZID"] = [dt.tzinfo.key]
+        value = dt.strftime(datetime_format)
+    else:
+        value = dt.astimezone(UTC).strftime(datetime_format) + "Z"
+    event.extra.append(ContentLine(name, params, value=value))
+
+
+def ics_event_to_calendar(event: Event, method: str | None, loc_context: LocalizationContext) -> Calendar:
     # PRODID is mandatory and generally follows "-//[Organization]//[Product Name]//[Language]"
     calendar = Calendar(creator=f"-//Couchers.org//Couchers//{loc_context.locale.upper()}")
     if method:
@@ -98,7 +162,7 @@ def event_to_calendar(event: Event, method: str | None, loc_context: Localizatio
     return calendar
 
 
-def calendar_to_attachment(calendar: Calendar, filename: str) -> EmailPart:
+def ics_calendar_to_attachment(calendar: Calendar, filename: str) -> EmailPart:
     data = calendar.serialize().encode("utf-8")
     content_disposition = f'attachment; filename="{filename}"'
     content_type = 'text/calendar; charset="utf-8"'
@@ -108,8 +172,3 @@ def calendar_to_attachment(calendar: Calendar, filename: str) -> EmailPart:
         content_type += f"; method={calendar.method}"
 
     return EmailPart(data=data, content_disposition=content_disposition, content_type=content_type)
-
-
-def get_host_request_event_uid(host_request_id: int) -> str:
-    uid_domain = Address(addr_spec=config.NOTIFICATION_EMAIL_ADDRESS).domain
-    return f"host_request.{host_request_id}@{uid_domain}"

app/backend/src/couchers/notifications/render_email.py

@@ -6,7 +6,7 @@
 from couchers import urls
 from couchers.config import config
 from couchers.email.blocks import EmailBase, EmailFooter, UnsubscribeInfo, UnsubscribeLink
-from couchers.email.calendar_events import create_host_request_attachment, create_host_request_cancellation_attachment
+from couchers.email.calendar_events import create_host_request_attachment
 from couchers.email.rendering import render_email
 from couchers.i18n import LocalizationContext
 from couchers.models import Notification, NotificationTopicAction, User
@@ -184,7 +184,7 @@ def get_ics_attachment(notification: Notification, loc_context: LocalizationCont
     elif notification.topic_action == NotificationTopicAction.host_request__cancel:
         # Caveat: only the party getting cancelled receives this notification,
         # we have no opportunity to provide the cancelling party with a cancelled ics attachment.
-        return create_host_request_cancellation_attachment(
+        return create_host_request_attachment(
             data.host_request, other_name=data.surfer.name, hosting=True, loc_context=loc_context
         )
     else:

app/backend/src/couchers/servicers/events.py

@@ -13,6 +13,7 @@
 
 from couchers.context import CouchersContext, make_notification_user_context
 from couchers.db import can_moderate_node, get_parent_node_at_location, session_scope
+from couchers.email.calendar_events import create_event_ics_calendar
 from couchers.event_log import log_event
 from couchers.helpers.completed_profile import has_completed_profile
 from couchers.jobs.enqueue import queue_job
@@ -38,6 +39,7 @@
 from couchers.moderation.utils import create_moderation
 from couchers.notifications.notify import notify
 from couchers.proto import events_pb2, events_pb2_grpc, notification_data_pb2
+from couchers.proto.google.api import httpbody_pb2
 from couchers.proto.internal import jobs_pb2
 from couchers.servicers.api import user_model_to_pb
 from couchers.servicers.blocking import is_not_visible
@@ -1366,3 +1368,16 @@ def RemoveEventOrganizer(
         session.delete(organizer_to_remove)
 
         return empty_pb2.Empty()
+
+    def GetEventCalendarFile(
+        self, request: events_pb2.GetEventCalendarFileReq, context: CouchersContext, session: Session
+    ) -> httpbody_pb2.HttpBody:
+        res = _get_event_and_occurrence_one_or_none(session, occurrence_id=request.event_id, context=context)
+        if not res:
+            context.abort_with_error_code(grpc.StatusCode.NOT_FOUND, "event_not_found")
+
+        _, occurrence_db = res
+
+        event_pb = event_to_pb(session, occurrence_db, context)
+        ics_data = create_event_ics_calendar(event_pb, context.localization).serialize().encode("utf-8")
+        return httpbody_pb2.HttpBody(content_type="text/calendar", data=ics_data)