call prepare_download() to prepare a download

prolefeeder.py

@@ -29,10 +29,14 @@ def download():
         form.start_time.data = datetime.now() - timedelta(hours=1)
         form.length.data = 60
     elif form.validate_on_submit():
-        flash('The download should start immediately.', 'success')
-        return render_template('download.html', form=form, filename='test.mp3')
+        output_filename = prepare_download(form)
+        if output_filename:
+            flash('The download should start immediately.', 'success')
+            return render_template('download.html', form=form, filename=output_filename)
+        else:
+            flash('Error preparing download!', 'warning')
     else:
-        flash('Error', 'warning')
+        flash('Error in form!', 'warning')
     return render_template('download.html', form=form)
 
 
@@ -42,5 +46,9 @@ def download_file(filename):
                                as_attachment=True)
 
 
+def prepare_download(form):
+    return 'test.mp3'
+
+
 if __name__ == '__main__':
     app.run(debug=True)