Database transaction code adapted for more safety

app.py

@@ -76,42 +76,54 @@ def db_to_json():
 
 def json_to_db(data):
     try:
-        db.session.query(Attendance).delete()
+        # Start a single transaction for all operations
-        db.session.commit()
+        with db.session.begin():
-        db.session.query(GuestName).delete()
+            # Clear existing attendance records
-        db.session.commit()
+            db.session.query(Attendance).delete()
-        db.session.query(Date).delete()
+            db.session.query(GuestName).delete()
-        db.session.commit()
+            
-        db.session.query(Player).delete()
+            # Update players - keep existing ones, add new ones
-        db.session.commit()
+            existing_players = {p.name: p for p in Player.query.all()}
+            for name in data.get("players", []):
+                if name not in existing_players:
+                    db.session.add(Player(name=name))
+            
+            # Update dates - keep existing ones, add new ones
+            existing_dates = {d.date_str: d for d in Date.query.all()}
+            for date_str in data.get("dates", []):
+                if date_str not in existing_dates:
+                    date = Date(date_str=date_str)
+                    db.session.add(date)
+                    existing_dates[date_str] = date
+            
+            # Refresh player list after potential additions
+            player_dict = {p.name: p for p in Player.query.all()}
+            
+            # Add attendance records
+            for date_str in data.get("dates", []):
+                date = existing_dates[date_str]
+                for idx, player_name in enumerate(data["players"] + [data["guest"]]):
+                    key = f"{date_str}|{idx}"
+                    status = data["attendance"].get(key)
+                    if status and player_name in player_dict:
+                        player = player_dict[player_name]
+                        # Convert boolean True to string 'yes'
+                        status_value = 'yes' if status is True else status
+                        # Only add if status is one of the valid values
+                        if status_value in ['yes', 'no', 'maybe']:
+                            db.session.add(Attendance(date_id=date.id, player_id=player.id, status=status_value))
+                
+                # Add guest name if present
+                guest_name = data.get("guestNames", {}).get(date_str)
+                if guest_name:
+                    db.session.add(GuestName(date_id=date.id, name=guest_name))
+            
+            # The transaction will be committed automatically if no exceptions occur
     except Exception as e:
-        db.session.rollback()
+        # The transaction will be rolled back automatically if an exception occurs
-        print("Error during deletion:", e)
+        print("Error during database operation:", e)
         raise
 
-    # Insert players from JSON
-    for name in data.get("players", []):
-        db.session.add(Player(name=name))
-    db.session.commit()
-
-    # Insert dates and attendance
-    for date_str in data.get("dates", []):
-        date = Date(date_str=date_str)
-        db.session.add(date)
-        db.session.commit()
-        for idx, player_name in enumerate(data["players"] + [data["guest"]]):
-            key = f"{date_str}|{idx}"
-            status = data["attendance"].get(key)
-            if status:
-                player = Player.query.filter_by(name=player_name).first()
-                if player:
-                    # Save status as 'yes', 'no', or 'maybe'
-                    db.session.add(Attendance(date_id=date.id, player_id=player.id, status='yes' if status is True else status if status in ['no', 'maybe'] else None))
-        guest_name = data.get("guestNames", {}).get(date_str)
-        if guest_name:
-            db.session.add(GuestName(date_id=date.id, name=guest_name))
-    db.session.commit()
-
 
 
 @app.route('/')