If you want to take a dump of your call records (on an Android device) in a csv format and analyse it in an excel sheet or on any database.
If you want to test this app, download from /apk folder and if you are downloading on your device, use chrome and not es file explorer it tends to corrupt the apk file.
Also, haven't handled orientation and background, foreground changes, the app crashes.
Whenever you click on the button on the landing page, the .csv overwrites the previous one (for now). May be a timestamp in the file name could be added.