Move towards a more object-oriented API

This implied switching to a different caching approach.

.gitignore

@@ -6,3 +6,4 @@ docker-compose.yml
 dist/
 node_modules/
 yarn*.log
+*.yml

config.yml.example

@@ -0,0 +1,7 @@
+calendars:
+  - name: "Events"
+    url: "https://example.org/events.ics"
+
+  - name: "More events"
+    url: "https://example.com/more-events.ics"
+    default_color: "#aabbcc"

fabcal/app.py

@@ -3,8 +3,6 @@ import locale
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.staticfiles import StaticFiles
-from fastapi_cache import FastAPICache
-from fastapi_cache.backends.inmemory import InMemoryBackend
 
 from fabcal.routers import api_v1, frontend
 
@@ -29,8 +27,3 @@ app.add_middleware(
 
 
 locale.setlocale(locale.LC_TIME, locale.getlocale())
-
-
-@app.on_event("startup")
-async def startup():
-    FastAPICache.init(InMemoryBackend())

fabcal/calendar_client.py

@@ -1,53 +1,112 @@
+import asyncio
 import os
 
 from collections import OrderedDict
 from datetime import date, datetime, timedelta, timezone
-from typing import List
+from typing import Dict, List, NamedTuple
 
 import aiohttp
 import recurring_ical_events
+import yaml
 
-from fastapi_cache.decorator import cache
-from icalendar import Calendar, vText
+from asyncache import cached
+from cachetools import TTLCache, LRUCache
+from icalendar import Calendar
 
 from fabcal.models import CalendarEvent
 
 
-def sanitize(data: str):
-    # sanitize input from random source
-    cal = Calendar.from_ical(data)
-
-    # name needs to be fixed
-    cal["X-WR-CALNAME"] = vText(b"FabLab-Termine")
-
-    return cal.to_ical()
+class ConfiguredCalendar(NamedTuple):
+    name: str
+    url: str
+    default_color: str = None
 
 
-def get_calendar_url():
-    url = os.environ["CALENDAR_URL"]
+class CalendarClient:
+    def __init__(self, url: str):
+        self.url = url
 
-    # convenience feature
-    url = url.replace("webcal://", "https://")
-
-    return url
-
-
-# caching strings works better than caching calendar objects
-@cache(expire=120)
-async def get_data() -> str:
-    async with aiohttp.ClientSession() as session:
-        async with session.get(get_calendar_url()) as response:
+    async def get(self, session):
+        async with session.get(self.url) as response:
             response.raise_for_status()
             assert response.content_type.lower() == "text/calendar"
 
-            return sanitize(await response.text())
+            return await response.text()
+
+
+# this will be cached permanently, i.e., the server process needs to be restarted to apply config changes
+@cached(LRUCache(100))
+def read_calendars_from_config_file():
+    with open("config.yml") as f:
+        data = yaml.safe_load(f)
+
+        for calendar in data["calendars"]:
+            yield ConfiguredCalendar(**calendar)
+
+
+
+class CombinedCalendarClient:
+    def __init__(self, configured_calendars: List[ConfiguredCalendar]):
+        # make sure it's a list since read_calendars_from_config_file() returns an iterator
+        self.configured_calendars = list(configured_calendars)
+
+    async def fetch_calendars(self) -> Dict[ConfiguredCalendar, str]:
+        async with aiohttp.ClientSession() as session:
+            calendar_clients = [CalendarClient(calendar.url) for calendar in self.configured_calendars]
+            responses = await asyncio.gather(*[calendar.get(session) for calendar in calendar_clients])
+
+        return dict(zip(self.configured_calendars, responses))
+
+    @staticmethod
+    def combine_calendars(data: Dict[ConfiguredCalendar, str]) -> Calendar:
+        combined_calendar = Calendar()
+
+        combined_calendar.add("prodid", "-//FabCal//NONSGML//EN")
+        combined_calendar.add("version", "2.0")
+        combined_calendar.add("x-wr-calname", "FabLab Altmühlfranken e.V.")
+        # TODO: normalize timezones of calendar events
+
+        for configured_calendar, ical_str in data.items():
+            cal = Calendar.from_ical(ical_str)
+
+            # check for a calendar color (e.g., Nextcloud has such a feature)
+            # events that don't have a color assigned will be assigned this color unless a color was configured
+            default_color = configured_calendar.default_color
+
+            if not default_color:
+                try:
+                    # note: for some reason, getattr doesn't work
+                    default_color = cal["x-apple-calendar-color"]
+                except KeyError:
+                    default_color = None
+
+            # we don't copy anything but events from the
+            for event in cal.walk("VEVENT"):
+                # if no color has been configured in the event, we
+
+                if "color" not in event:
+                    event["color"] = default_color
+
+                combined_calendar.add_component(event)
+
+        return combined_calendar
+
+    async def fetch_and_combine_calendars(self) -> Calendar:
+        return self.combine_calendars(await self.fetch_calendars())
+
+
+@cached(TTLCache(maxsize=100, ttl=int(os.environ.get("FABCAL_CACHE_EXPIRE", 120))))
+async def get_data() -> Calendar:
+    client = CombinedCalendarClient(read_calendars_from_config_file())
+    combined_calendar = await client.fetch_and_combine_calendars()
+    return combined_calendar
 
 
 def get_tzinfo():
     return timezone(timedelta(hours=1))
 
 
-def get_events_from_calendar_string(cal: Calendar) -> List[CalendarEvent]:
+def get_events_from_calendar(cal: Calendar) -> List[CalendarEvent]:
     """
     Generate list of events from calendar vevents.
     Expands recurring events for +- one year.
@@ -106,9 +165,7 @@ def get_events_from_calendar_string(cal: Calendar) -> List[CalendarEvent]:
 
 
 async def get_future_events():
-    cal = Calendar.from_ical(await get_data())
-
-    events = get_events_from_calendar_string(cal)
+    events = get_events_from_calendar(await get_data())
 
     today = datetime.today().date()
 

fabcal/routers/api_v1.py

@@ -10,7 +10,7 @@ router = APIRouter()
 @router.get("/events.ics")
 async def events_ics():
     return Response(
-        await get_data(),
+        (await get_data()).to_ical(True),
         headers={
             "content-type": "text/calendar",
         },

pyproject.toml

@@ -15,9 +15,10 @@ fastapi = "^0.75.0"
 uvicorn = {extras = ["standard"], version = "^0.17.6"}
 Jinja2 = "^3.1.0"
 Babel = "^2.9.1"
-fastapi-cache2 = "^0.1.8"
 aiohttp = {extras = ["speedups"], version = "^3.8.1"}
 recurring-ical-events = "^1.0.1-beta.0"
+pyyaml = "^6.0"
+asyncache = "^0.3.1"
 
 [tool.poetry.dev-dependencies]
 black = "^22.1.0"