added ics support. and some thread safety

API.py

@@ -1 +1,81 @@
-# TODO
+from flask import Flask, Response
+from icalendar import Calendar, Event
+from datetime import datetime
+import pytz
+import uuid
+
+
+class Webserver:
+    def __init__(self, ip, port, db_instance):
+        self.ip = ip
+        self.port = port
+        self.db = db_instance
+
+        self.app = Flask(__name__)
+        self.tz = pytz.timezone("Europe/Amsterdam")
+
+        self._register_routes()
+
+    def _register_routes(self):
+        self.app.add_url_rule("/", "index", lambda: "Calendar server running ✅")
+        self.app.add_url_rule("/calendar.ics", "calendar", self._calendar_endpoint)
+
+    def _fetch_shifts(self):
+        con = self.db._get_connection()
+        cur = con.cursor()
+
+        cur.execute("""
+            SELECT shift_start, shift_end, department, description
+            FROM shifts
+            ORDER BY shift_start ASC
+        """)
+
+        rows = cur.fetchall()
+        con.close()
+
+        shifts = []
+        for row in rows:
+            start_str, end_str, department, description = row
+
+            # Convert string → datetime
+            start = self._parse_datetime(start_str)
+            end = self._parse_datetime(end_str)
+
+            shifts.append({
+                "start": start,
+                "end": end,
+                "description": f"{description} ",
+                "department": f"{department} "
+            })
+
+        return shifts
+
+    def _parse_datetime(self, dt_str):
+        dt = datetime.fromisoformat(dt_str)
+        if dt.tzinfo is None:
+            dt = self.tz.localize(dt)
+        return dt
+
+    def _calendar_endpoint(self):
+        cal = Calendar()
+        cal.add('prodid', '-//Shift Calendar//example//')
+        cal.add('version', '2.0')
+
+        shifts = self._fetch_shifts()
+
+        for shift in shifts:
+            event = Event()
+            event.add('uid', str(uuid.uuid4()))
+            event.add('dtstart', shift["start"])
+            event.add('dtend', shift["end"])
+            event.add('summary', shift["department"])
+            event.add('description', shift["description"])
+            event.add('dtstamp', datetime.now(tz=self.tz))
+
+            cal.add_component(event)
+
+        return Response(cal.to_ical(), mimetype="text/calendar")
+
+    def run(self):
+        print(f"🚀 Starting server on {self.ip}:{self.port}")
+        self.app.run(host=self.ip, port=self.port)