@@ -0,0 +1,65 @@
+import os
+from icalendar.cal import Calendar, Event
+import requests
+from flask import Flask
+from datetime import date, datetime, timedelta, time
+import zoneinfo
+
+app = Flask(__name__)
+
+user_name = (os.environ.get("NAME") or os.environ.get("USER") or "unknown").title()
+tz = zoneinfo.ZoneInfo(os.environ.get("TZ") or "Europe/Berlin")
+
+def fetch_calendar(calendar_url):
+    return requests.get(calendar_url).content
+
+def read_calendar_file(calendar_file):
+    with open(calendar_file, 'rb') as f:
+        return f.read()
+
+def get_calendar():
+    file = os.environ.get('CALENDAR_FILE')
+    if file is not None:
+        return read_calendar_file(file)
+    else:
+        calendar_url = os.environ.get("CALENDAR_URL")
+        if calendar_url is None:
+            raise ValueError("CALENDAR_URL not set.")
+        return fetch_calendar(calendar_url)
+
+def fixup_date(dt):
+    if type(dt) == date:
+        return datetime.combine(dt, time.min, tzinfo=tz)
+    elif dt.tzinfo is None:
+        return dt.replace(tzinfo=tz)
+    else:
+        return dt.astimezone(tz)
+
+@app.route('/')
+def index():
+    start_date = datetime.combine(date.today(), time.min, tzinfo=tz)
+    end_date = start_date + timedelta(days=30)
+
+    output = Calendar()
+    output.add('prodid', '-//Calendar Anonymiser//alin.ovh//')
+    output.add('version', '2.0')
+
+    # Parse with icalendar
+    try:
+        input = Calendar.from_ical(get_calendar())
+        for component in input.walk():
+            if component.name == "VEVENT":
+                dtstart = fixup_date(component.get('dtstart').dt)
+                dtend = fixup_date(component.get('dtend', component.get('dtstart')).dt)
+                if dtstart >= start_date and dtend <= end_date:
+                    ev = Event()
+                    ev.add('summary', f'{user_name} Busy')
+                    ev.DTSTART = dtstart
+                    ev.DTEND = dtend
+                    output.add_component(ev)
+        return output.to_ical(), { "Content-Type": "text/plain" }
+    except Exception as e:
+        return f"Error parsing with icalendar: {str(e)}", 500
+
+if __name__ == '__main__':
+    app.run(debug=True)