Fixed some errors

app.py

@@ -7,22 +7,31 @@ from dotenv import load_dotenv
 load_dotenv()
 
 def upload_file():
-    st.title("Upload File to chat with file")
+    if not st.session_state.filename_and_retriever_engine:
+        st.title("Upload File to chat with file")
+    else:
+        st.title(f"File {st.session_state.filename_and_retriever_engine[0]} loaded.")
+        st.info("Click on Chat in sidebar")
+        st.info("Upload another file if you want to chat with a different pdf")
     uploaded_file = st.file_uploader("Choose a PDF file", type="pdf")
     if uploaded_file is None:
-        st.info("Please upload a PDF file.")
+        if not st.session_state.filename_and_retriever_engine:
+            st.info("Please upload a PDF file.")
     else:
         st.info(f"Uploaded PDF: {uploaded_file.name}")
         if st.button("Process PDF"):
             with st.spinner("Processing PDF..."):
-                st.session_state.retriever_engine = process_pdf(uploaded_file)
+                st.session_state.filename_and_retriever_engine = uploaded_file.name, process_pdf(uploaded_file)
                 st.success("PDF processed successfully!")
+                st.success("Click on Chat in sidebar")
+    
 
 def ask_question():
-    if st.session_state.retriever_engine :
+    if st.session_state.filename_and_retriever_engine :
+        st.title(f"Chat with {st.session_state.filename_and_retriever_engine[0]}")
         if user_question := st.chat_input("Ask a question"):
             with st.spinner("Retrieving information..."):
-                response, retrieved_image_path_list = retrieve_and_query(user_question, st.session_state.retriever_engine)
+                response, retrieved_image_path_list = retrieve_and_query(user_question, st.session_state.filename_and_retriever_engine[1])
                 print(retrieved_image_path_list)
             st.write("Retrieved Context:")
             for node in response.source_nodes:
@@ -40,8 +49,8 @@ def ask_question():
     
     
 def main():
-    if "retriever_engine" not in st.session_state:
-        st.session_state.retriever_engine = None
+    if "filename_and_retriever_engine" not in st.session_state:
+        st.session_state.filename_and_retriever_engine = None
     page_names_to_funcs = {
         "Upload File": upload_file,
         "Chat": ask_question