add save/load button

app.py

@@ -75,6 +75,36 @@ def main():
         options=list(pages.keys()),
         index=0,
     )
+    with st.sidebar.expander("Save or Load your work"):
+        # Save intermediary state
+        current_date = datetime.now().strftime(
+            "%m/%d/%Y, %H:%M:%S"
+        )
+        friendly_date = re.sub(
+            r"[^\w\s]", "_", current_date
+        ).replace(" ", "_").replace("__", "_").replace("-", "")
+        st.download_button(
+            label="Save Intermediary Card State",
+            data=json.dumps(st.session_state.get("card_dict", {}), indent=2),
+            file_name=f"data_card_{friendly_date}.json",
+        )
+        # load from file
+        uploaded_file = st.file_uploader(
+            label=f"Load Intermediary Card State",
+        )
+        if uploaded_file is not None:
+            pre_card_dict = json.load(uploaded_file, encoding="utf-8")
+            def save_dict_to_save_state(saved, prefix=None):
+                prefix = [] if prefix is None else prefix
+                if isinstance(saved, dict):
+                    for k, v in saved.items():
+                        save_dict_to_save_state(v, prefix + [k])
+                else:
+                    st.session_state.save_state["_".join(prefix)] = saved
+            # TODO: don't overwrite by default
+            st.session_state.card_dict = pre_card_dict
+            save_dict_to_save_state(st.session_state.card_dict)
+            # TODO: delete file after use
     st.markdown("#### GEM Data Card Input Form")
     pages[app_mode]()