consolidate database transactions when creating new thread

backend/main.py

@@ -36,34 +36,38 @@ async def get_posts(db: db_dependency):
 
 @app.post('/', status_code=status.HTTP_201_CREATED)
 async def create_thread(db: db_dependency, data: PostCreate):
-    # Create the post
-    post = Post(
-        author=data.author,
-        title=data.title,
-        content=data.content
-    )
-    db.add(post)
-    db.commit()
+    try:
+        # Create the post
+        post = Post(
+            author=data.author,
+            title=data.title,
+            content=data.content
+        )
+        db.add(post)
+        db.flush()
 
-    # Create the thread
-    thread = Thread(
-        author=post.author,
-        title=post.title,
-        content=post.content
-    )
-    db.add(thread)
-    db.commit()
+        # Create the thread
+        thread = Thread(
+            author=post.author,
+            title=post.title,
+            content=post.content
+        )
+        db.add(thread)
+        db.flush()
 
-    # Update the Post with thread_id
-    post.thread_id = thread.id
-    db.commit()
+        # Update the Post with thread_id
+        post.thread_id = thread.id
+        db.commit()
 
-    return {
-        'id': post.id,
-        'author': post.author,
-        'title': post.title,
-        'content': post.content
-    }
+        return {
+            'id': post.id,
+            'author': post.author,
+            'title': post.title,
+            'content': post.content
+        }
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(status_code=400, detail=str(e))
 
 
 @app.get('/{thread_id}', status_code=status.HTTP_200_OK)
@@ -95,7 +99,7 @@ async def create_reply(db: db_dependency, data: PostCreate, thread_id: int = Pat
             'content': post.content
         }
 
-    raise HTTPException(404, f'Could not find thread')
+    raise HTTPException(status_code=404, detail='Could not find thread')
 
 
 @app.get('/catalog', status_code=status.HTTP_200_OK)