Tournesol's rate-later page enables contributors to select videos to rate.
Algorithm run when a contributor adds a new video
When a contributor adds a video identifier to Tournesol, via the rate-later page, the chrome extension or the Android application, Tournesol first checks if the video is in the Tournesol video metadata database. If it is, then the video identifier is added to the contributor's rate-later list.
If the video is not in the Tournesol video metadata database, then Tournesol checks if the video identifier matches the YouTube video identifier format. This allows to prevent erroneous addition of content. In case of an error, an error message "The content you are selecting does not seem to be a YouTube video identifier".
If the video identifier has the right format, it is added to the contributor's pre-rate-later list. At this point, Tournesol also checks whether the video identifier is in the global pending video database. If it is not, then the video identifier is added to the pending video database, and a call is made to youtube-dl to download the video metadata. As described in the video metadata wiki page, the call is repeatedly with an exponentially increasing delay time, without an eventual timeout, until the video metadata are successfully retrieved.
If the video metadata are successfully retrieved, then the video identifier is removed from the pending video database. As described in the wiki pending video database page, the video identifier is also moved from all contributors' pre-rate-later lists to their rate-later list.
Removal from rate-later list
When a contributor rates a video of the rate-later list, the video is removed from the rate-later list.