Add download csv

app.py

@@ -1,6 +1,7 @@
 # Example taken from here - https://shinylive.io/py/examples/#map
 
 import os
+import io
 from shiny import reactive, render, ui, App
 
 from plot_utils import show_one_plot, show_two_plots
@@ -21,7 +22,8 @@ app_ui = ui.page_fluid(
     ui.output_ui("tab_slider"),
     ui.input_radio_buttons("split_filter", "Apply filter?",
                choices=["No filter", "Filter"], selected="No filter"),
-    ui.output_ui("page_ui")
+    ui.output_ui("page_ui"),
+    ui.download_button("download_csv", "Download simulation as CSV")
 )
 
 def server(input, output, session):
@@ -139,5 +141,26 @@ def server(input, output, session):
                   "Tree canopy coverage increase in %pt")
         return fig
 
+    @output
+    @render.download(filename=lambda: (
+        f"gdf_trees_{input.tree_pct()}pct.csv" if input.tab_choice() == "Effect of trees on temperature"
+        else f"gdf_temp_{input.temp_goal()}C.csv"
+    ))
+    def download_csv():
+        if input.tab_choice() == "Effect of trees on temperature":
+            df = get_gdf_trees()
+        else:
+            df = get_gdf_temp()
+
+        if not hasattr(df, "to_csv"):
+            raise ValueError("Expected a DataFrame or GeoDataFrame")
+
+        df = df.drop(columns="geometry", errors="ignore")
+
+        buffer = io.StringIO()
+        df.to_csv(buffer, index=False)
+        buffer.seek(0)
+        return buffer 
+
 app = App(app_ui, server)