feat: implement caching for duty-related data and enhance performance

- Added a TTLCache class for in-memory caching of duty-related data, improving performance by reducing database queries.
- Integrated caching into the group duty pin functionality, allowing for efficient retrieval of message text and next shift end times.
- Introduced new methods to invalidate caches when relevant data changes, ensuring data consistency.
- Created a new Alembic migration to add indexes on the duties table for improved query performance.
- Updated tests to cover the new caching behavior and ensure proper functionality.

duty_teller/api/app.py

@@ -3,6 +3,7 @@
 import logging
 import re
 from datetime import date, timedelta
+
 import duty_teller.config as config
 from fastapi import Depends, FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
@@ -18,6 +19,7 @@ from duty_teller.api.dependencies import (
     require_miniapp_username,
 )
 from duty_teller.api.personal_calendar_ics import build_personal_ics, build_team_ics
+from duty_teller.cache import ics_calendar_cache
 from duty_teller.db.repository import (
     get_duties,
     get_duties_for_user,
@@ -116,14 +118,18 @@ def get_team_calendar_ical(
     user = get_user_by_calendar_token(session, token)
     if user is None:
         return Response(status_code=404, content="Not found")
-    today = date.today()
-    from_date = (today - timedelta(days=365)).strftime("%Y-%m-%d")
-    to_date = (today + timedelta(days=365 * 2)).strftime("%Y-%m-%d")
-    all_duties = get_duties(session, from_date=from_date, to_date=to_date)
-    duties_duty_only = [
-        (d, name) for d, name in all_duties if (d.event_type or "duty") == "duty"
-    ]
-    ics_bytes = build_team_ics(duties_duty_only)
+    cache_key = ("team_ics",)
+    ics_bytes, found = ics_calendar_cache.get(cache_key)
+    if not found:
+        today = date.today()
+        from_date = (today - timedelta(days=365)).strftime("%Y-%m-%d")
+        to_date = (today + timedelta(days=365 * 2)).strftime("%Y-%m-%d")
+        all_duties = get_duties(session, from_date=from_date, to_date=to_date)
+        duties_duty_only = [
+            (d, name) for d, name in all_duties if (d.event_type or "duty") == "duty"
+        ]
+        ics_bytes = build_team_ics(duties_duty_only)
+        ics_calendar_cache.set(cache_key, ics_bytes)
     return Response(
         content=ics_bytes,
         media_type="text/calendar; charset=utf-8",
@@ -151,13 +157,17 @@ def get_personal_calendar_ical(
     user = get_user_by_calendar_token(session, token)
     if user is None:
         return Response(status_code=404, content="Not found")
-    today = date.today()
-    from_date = (today - timedelta(days=365)).strftime("%Y-%m-%d")
-    to_date = (today + timedelta(days=365 * 2)).strftime("%Y-%m-%d")
-    duties_with_name = get_duties_for_user(
-        session, user.id, from_date=from_date, to_date=to_date, event_types=["duty"]
-    )
-    ics_bytes = build_personal_ics(duties_with_name)
+    cache_key = ("personal_ics", user.id)
+    ics_bytes, found = ics_calendar_cache.get(cache_key)
+    if not found:
+        today = date.today()
+        from_date = (today - timedelta(days=365)).strftime("%Y-%m-%d")
+        to_date = (today + timedelta(days=365 * 2)).strftime("%Y-%m-%d")
+        duties_with_name = get_duties_for_user(
+            session, user.id, from_date=from_date, to_date=to_date, event_types=["duty"]
+        )
+        ics_bytes = build_personal_ics(duties_with_name)
+        ics_calendar_cache.set(cache_key, ics_bytes)
     return Response(
         content=ics_bytes,
         media_type="text/calendar; charset=utf-8",

duty_teller/api/calendar_ics.py

@@ -7,12 +7,15 @@ from urllib.error import URLError
 
 from icalendar import Calendar
 
+from duty_teller.cache import TTLCache
 from duty_teller.utils.http_client import safe_urlopen
 
 log = logging.getLogger(__name__)
 
-# In-memory cache: url -> (cached_at_timestamp, raw_ics_bytes)
+# Raw ICS bytes cache: url -> (cached_at_timestamp, raw_ics_bytes)
 _ics_cache: dict[str, tuple[float, bytes]] = {}
+# Parsed events cache: url -> list of {date, summary}. TTL 7 days.
+_parsed_events_cache = TTLCache(ttl_seconds=7 * 24 * 3600, max_size=100)
 CACHE_TTL_SECONDS = 7 * 24 * 3600  # 1 week
 FETCH_TIMEOUT_SECONDS = 15
 
@@ -68,8 +71,8 @@ def _event_date_range(component) -> tuple[date | None, date | None]:
     return (start_d, last_d)
 
 
-def _get_events_from_ics(raw: bytes, from_date: str, to_date: str) -> list[dict]:
-    """Parse ICS bytes and return list of {date, summary} in [from_date, to_date]. One-time events only."""
+def _parse_ics_to_events(raw: bytes) -> list[dict]:
+    """Parse ICS bytes and return all events as list of {date, summary}. One-time events only."""
     result: list[dict] = []
     try:
         cal = Calendar.from_ical(raw)
@@ -79,9 +82,6 @@ def _get_events_from_ics(raw: bytes, from_date: str, to_date: str) -> list[dict]
         log.warning("Failed to parse ICS: %s", e)
         return result
 
-    from_d = date.fromisoformat(from_date)
-    to_d = date.fromisoformat(to_date)
-
     for component in cal.walk():
         if component.name != "VEVENT":
             continue
@@ -95,13 +95,27 @@ def _get_events_from_ics(raw: bytes, from_date: str, to_date: str) -> list[dict]
 
         d = start_d
         while d <= end_d:
-            if from_d <= d <= to_d:
-                result.append({"date": d.strftime("%Y-%m-%d"), "summary": summary_str})
+            result.append({"date": d.strftime("%Y-%m-%d"), "summary": summary_str})
             d += timedelta(days=1)
 
     return result
 
 
+def _filter_events_by_range(
+    events: list[dict], from_date: str, to_date: str
+) -> list[dict]:
+    """Filter events list to [from_date, to_date] range."""
+    from_d = date.fromisoformat(from_date)
+    to_d = date.fromisoformat(to_date)
+    return [e for e in events if from_d <= date.fromisoformat(e["date"]) <= to_d]
+
+
+def _get_events_from_ics(raw: bytes, from_date: str, to_date: str) -> list[dict]:
+    """Parse ICS bytes and return events in [from_date, to_date]. Wrapper for tests."""
+    events = _parse_ics_to_events(raw)
+    return _filter_events_by_range(events, from_date, to_date)
+
+
 def get_calendar_events(
     url: str,
     from_date: str,
@@ -135,4 +149,10 @@ def get_calendar_events(
             return []
         _ics_cache[url] = (now, raw)
 
-    return _get_events_from_ics(raw, from_date, to_date)
+    # Use parsed events cache to avoid repeated Calendar.from_ical() + walk()
+    cache_key = (url,)
+    events, found = _parsed_events_cache.get(cache_key)
+    if not found:
+        events = _parse_ics_to_events(raw)
+        _parsed_events_cache.set(cache_key, events)
+    return _filter_events_by_range(events, from_date, to_date)