you can use this application to download all your videos and then upload them to your website
http://www.finalvideodownloader.com/supported-sites.html
sorry not a programmer, cant help you with a bot but if you are looking to download them directly to your server, i would say use
http://www.tubeoffline.com/download-VidSpot-videos.php#.Vd-LQJdSX1w
or
https://www.extramaster.net/tools/videoDownloader/.ie
and then use remote upload on your site to directly upload videos to it but this way you will have to do one by one.
Hope this helps.