feat: add personal ics feeds for assigned tasks

app/services/bootstrap.py

@@ -17,8 +17,18 @@ def ensure_schema_and_admins() -> None:
         db.session.execute(text("ALTER TABLE user ADD COLUMN is_admin BOOLEAN NOT NULL DEFAULT 0"))
         db.session.commit()
 
+    if "calendar_feed_token" not in column_names:
+        db.session.execute(text("ALTER TABLE user ADD COLUMN calendar_feed_token VARCHAR(255)"))
+        db.session.commit()
+
     ensure_app_settings()
 
+    users_without_feed = User.query.filter(User.calendar_feed_token.is_(None)).all()
+    if users_without_feed:
+        for user in users_without_feed:
+            user.ensure_calendar_feed_token()
+        db.session.commit()
+
     admin_exists = User.query.filter_by(is_admin=True).first()
     if admin_exists:
         return

app/services/calendar_feeds.py

@@ -0,0 +1,60 @@
+from __future__ import annotations
+
+from datetime import UTC, datetime, time, timedelta
+
+from ..models import TaskInstance, User
+
+
+def _ics_escape(value: str | None) -> str:
+    text = (value or "").replace("\\", "\\\\")
+    text = text.replace(";", "\\;").replace(",", "\\,")
+    text = text.replace("\r\n", "\\n").replace("\n", "\\n").replace("\r", "\\n")
+    return text
+
+
+def _format_date(value) -> str:
+    return value.strftime("%Y%m%d")
+
+
+def _format_timestamp(value: datetime | None) -> str:
+    timestamp = value or datetime.now(UTC).replace(tzinfo=None)
+    return timestamp.strftime("%Y%m%dT%H%M%SZ")
+
+
+def build_calendar_feed(user: User, base_url: str) -> str:
+    tasks = (
+        TaskInstance.query.filter_by(assigned_user_id=user.id)
+        .order_by(TaskInstance.due_date.asc(), TaskInstance.id.asc())
+        .all()
+    )
+
+    lines = [
+        "BEGIN:VCALENDAR",
+        "VERSION:2.0",
+        "PRODID:-//hnz.io//Putzliga//DE",
+        "CALSCALE:GREGORIAN",
+        "METHOD:PUBLISH",
+        f"X-WR-CALNAME:{_ics_escape(f'Putzliga - {user.name}')}",
+        f"X-WR-CALDESC:{_ics_escape('Persoenlicher Aufgabenfeed aus Putzliga')}",
+    ]
+
+    for task in tasks:
+        due_end = task.due_date + timedelta(days=1)
+        description = _ics_escape(task.description)
+        lines.extend(
+            [
+                "BEGIN:VEVENT",
+                f"UID:taskinstance-{task.id}@putzliga",
+                f"DTSTAMP:{_format_timestamp(task.updated_at)}",
+                f"LAST-MODIFIED:{_format_timestamp(task.updated_at)}",
+                f"SUMMARY:{_ics_escape(task.title)}",
+                f"DESCRIPTION:{description}",
+                f"DTSTART;VALUE=DATE:{_format_date(task.due_date)}",
+                f"DTEND;VALUE=DATE:{_format_date(due_end)}",
+                f"URL:{_ics_escape(base_url)}",
+                "END:VEVENT",
+            ]
+        )
+
+    lines.append("END:VCALENDAR")
+    return "\r\n".join(lines) + "\r\n"