refactor login logic to improve user feedback and session handling

app.py

@@ -116,24 +116,25 @@ def update_vote(
 
 
 
-if 'loggedin' not in st.session_state:
-    st.session_state['loggedin'] = 'false'
-    # st.session_state["vote-osman-image-path"] = "None"
-
-with st.form("login"):
-    username = st.selectbox("Select voter", voters)
-    password = st.text_input("Password (get password from [email protected])", type="password")
-    submitted = st.form_submit_button("Login")
-
-if submitted or st.session_state['loggedin'] == 'true':
-    if not password == os.environ.get("app_password"):
-        st.error("The password you entered is incorrect")
-        st.stop()
-    else:
-        st.success("Welcome, " + username)
-        st.write("You are now logged in")
-        st.session_state['loggedin'] = 'true'
-
+if 'loggedin' not in st.session_state: # user is not logged in
+    st.error("You are not logged in")
+    with st.form("login"):
+        username = st.selectbox("Select voter", voters)
+        password = st.text_input("Password (get password from [email protected])", type="password")
+        submitted = st.form_submit_button("Login")
+
+    if submitted: # submitted password
+        if not password == os.environ.get("app_password"): # password is incorrect
+            st.error("The password you entered is incorrect")
+            st.stop()
+        else: # password is correct
+            st.success("Welcome, " + username)
+            st.write("You are now logged in")
+            st.session_state['loggedin'] = username
+
+else: # logged in
+    username = st.session_state['loggedin']
+    st.success(f"Welcome, {username}")
     image_path = get_one_from_queue(username)
 
     with st.form("images", clear_on_submit=True):