Jun 29 - Implement auto reminder 45 min before user's shift end if not finish checking websites

app.py

@@ -17,6 +17,46 @@ logging.basicConfig(
 logger = logging.getLogger("app")
 
 
+def _run_reminder_job():
+    """Background job: send shift-incomplete reminders if within the reminder window."""
+    from routes.admin_shifts import do_send_incomplete_reminders
+    try:
+        result = do_send_incomplete_reminders(triggered_by_user_id=None)
+        if result["sent"] > 0:
+            logger.info(f"[scheduler] Shift reminders sent: {result}")
+    except Exception as e:
+        logger.error(f"[scheduler] Shift reminder job error: {e}")
+
+
+def _start_scheduler():
+    """
+    Start a background scheduler that fires shift-incomplete reminder emails
+    every 5 minutes. Guards against double-start in Flask's debug reloader.
+    Uses daemon threads so the process exits cleanly even if the scheduler is running.
+    """
+    if os.environ.get("WERKZEUG_RUN_MAIN") == "false":
+        # Flask reloader: skip in the parent monitor process; the child sets WERKZEUG_RUN_MAIN=true
+        return
+    try:
+        from apscheduler.schedulers.background import BackgroundScheduler
+        import atexit
+
+        scheduler = BackgroundScheduler(daemon=True)
+        scheduler.add_job(
+            func=_run_reminder_job,
+            trigger="interval",
+            minutes=5,
+            id="shift_incomplete_reminders",
+            max_instances=1,
+            misfire_grace_time=120,
+        )
+        scheduler.start()
+        atexit.register(lambda: scheduler.shutdown(wait=False))
+        logger.info("[scheduler] Background scheduler started — shift reminders every 5 min.")
+    except Exception as e:
+        logger.error(f"[scheduler] Failed to start background scheduler: {e}")
+
+
 def create_app():
     app = Flask(__name__)
 
@@ -73,10 +113,12 @@ def create_app():
 
     if not os.environ.get("CRON_SECRET"):
         logger.warning(
-            "CRON_SECRET not set in .env — the /internal/cron/* endpoints are "
-            "disabled. Set CRON_SECRET to enable automated shift reminders."
+            "CRON_SECRET not set in .env — the /internal/cron/* endpoints are disabled."
         )
 
+    # ── Background scheduler: automatic shift-incomplete reminders ────────────
+    _start_scheduler()
+
     # ── CSRF protection (Flask-WTF) ────────────────────────────────────────────
     from flask_wtf.csrf import CSRFProtect
     CSRFProtect(app)