fix(prompts): can now be removed (#2154)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

backend/modules/brain/controller/brain_routes.py

@@ -137,17 +137,21 @@ async def update_existing_brain(
     if existing_brain is None:
         raise HTTPException(status_code=404, detail="Brain not found")
 
-    brain_service.update_brain_by_id(brain_id, brain_update_data)
-
     if brain_update_data.prompt_id is None and existing_brain.prompt_id:
         prompt = prompt_service.get_prompt_by_id(existing_brain.prompt_id)
         if prompt and prompt.status == "private":
             prompt_service.delete_prompt_by_id(existing_brain.prompt_id)
 
-    if brain_update_data.status == "private" and existing_brain.status == "public":
-        brain_user_service.delete_brain_users(brain_id)
+            return {"message": f"Prompt {brain_id} has been updated."}
 
-    return {"message": f"Brain {brain_id} has been updated."}
+    elif brain_update_data.status == "private" and existing_brain.status == "public":
+        brain_user_service.delete_brain_users(brain_id)
+        return {"message": f"Brain {brain_id} has been deleted."}
+
+    else:
+        brain_service.update_brain_by_id(brain_id, brain_update_data)
+
+        return {"message": f"Brain {brain_id} has been updated."}
 
 
 @brain_router.put(

backend/modules/brain/service/brain_service.py

@@ -268,7 +268,6 @@ class BrainService:
                 status_code=404,
                 detail=f"Brain with id {brain_id} not found",
             )
-
         brain_update_answer = self.brain_repository.update_brain_by_id(
             brain_id,
             brain=BrainUpdatableProperties(

backend/modules/prompt/repository/prompts.py

@@ -1,10 +1,10 @@
 from fastapi import HTTPException
+from models.settings import get_supabase_client
 from modules.prompt.entity.prompt import Prompt
 from modules.prompt.repository.prompts_interface import (
     DeletePromptResponse,
     PromptsInterface,
 )
-from models.settings import get_supabase_client
 
 
 class Prompts(PromptsInterface):
@@ -30,6 +30,18 @@ class Prompts(PromptsInterface):
         Returns:
         A dictionary containing the status of the delete and prompt_id of the deleted prompt
         """
+
+        # Update brains where prompt_id is equal to the value to NULL
+        self.db.from_("brains").update({"prompt_id": None}).filter(
+            "prompt_id", "eq", prompt_id
+        ).execute()
+
+        # Update chat_history where prompt_id is equal to the value to NULL
+        self.db.from_("chat_history").update({"prompt_id": None}).filter(
+            "prompt_id", "eq", prompt_id
+        ).execute()
+
+        # Delete the prompt
         response = (
             self.db.from_("prompts")
             .delete()