Fix availability checks

backend/src/main/resources/db/migration/V18__past_appointments_missed.sql

@@ -1,6 +1,7 @@
--- V18: Normalize past appointments.
--- Any appointment that is still 'Booked' but the date/time has passed should be marked as 'Missed'.
+-- V18: Normalize past appointments and resolve initial employee double-bookings
 
+-- Part 1: Normalize past appointments.
+-- Any appointment that is still 'Booked' but the date/time has passed should be marked as 'Missed'.
 UPDATE appointment
 SET appointmentStatus = 'Missed'
 WHERE LOWER(appointmentStatus) = 'booked'
@@ -8,3 +9,37 @@ WHERE LOWER(appointmentStatus) = 'booked'
     appointmentDate < CURRENT_DATE
     OR (appointmentDate = CURRENT_DATE AND appointmentTime < CURRENT_TIME)
   );
+
+-- Part 2: Resolve potential double-bookings caused by V15's simple backfill.
+-- We try to spread overlapping appointments among other active staff in the same store.
+-- This is a one-time cleanup for demo data integrity.
+
+-- Temporary table to find conflicts (same employee, same date, overlapping time)
+-- For simplicity in SQL, we just check exact same time for the demo data cleanup.
+UPDATE appointment a1
+SET a1.employeeId = (
+    SELECT es.employeeId
+    FROM employeeStore es
+    JOIN employee e ON e.employeeId = es.employeeId
+    JOIN users u ON u.id = e.user_id
+    WHERE es.storeId = a1.storeId
+      AND e.isActive = TRUE
+      AND u.role = 'STAFF'
+      -- Find an employee who DOES NOT have an appointment at this exact time
+      AND NOT EXISTS (
+          SELECT 1 FROM appointment a2 
+          WHERE a2.employeeId = es.employeeId 
+            AND a2.appointmentDate = a1.appointmentDate 
+            AND a2.appointmentTime = a1.appointmentTime
+            AND a2.appointmentId <> a1.appointmentId
+      )
+    ORDER BY es.employeeId ASC
+    LIMIT 1
+)
+WHERE EXISTS (
+    SELECT 1 FROM appointment a3
+    WHERE a3.employeeId = a1.employeeId
+      AND a3.appointmentDate = a1.appointmentDate
+      AND a3.appointmentTime = a1.appointmentTime
+      AND a3.appointmentId < a1.appointmentId
+) AND LOWER(a1.appointmentStatus) NOT IN ('cancelled', 'missed');