PlaylistItem.PublishedAt is actually inaccurate

[derekantrican]

https://developers.google.com/youtube/v3/docs/playlistItems#snippet.publishedAt actually represents the value of when the item was added to the playlist. So if an item is removed from a playlist and added back, this time will change. Instead, we should use https://developers.google.com/youtube/v3/docs/videos#snippet.publishedAt

[derekantrican]

Upon further investigation, there is actually "videoPublishedAt" located in playlistItems.contentDetails. In YouTubeFunctions.GetMostRecentUploadsAsync I could almost replace Snippet with ContentDetails except that ContentDetails doesn't contain the video Title. I have submitted a request for that here: https://issuetracker.google.com/issues/152468533

[derekantrican]

I've created a new branch for this but I think it requires some layouts of pros & cons.

Using Snippet.PublishedAt for playlists:

Pro: If an old video (uploaded to YouTube a long time ago) is added to the playlist, the program will notify the user that there is a new video on the playlist

Con: If a video is removed from the playlist and re-added then the user will be notified of the re-add

Using ContentDetails.PublishedAt for playlists:

The inverse of above: Solves the "Con" but hurts the "Pro"

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One thing we could do is rather than just simply checking a date from the video against the current time, we could keep track of which videos we have notified the user of and which we haven't (then we wouldn't duplicate notifications for the same video id)

[derekantrican]

Just today there was a video uploaded by Tom Scott (playlist: UUBa659QWEk1AI4Tg--mrJ2A , video: LKSTmcvEdoU ) that has a snippet.PublishedAt date of Jan 9 (over 2 weeks ago) but a contentDetails.PublishedAt date that is accurate to today. So I don't think we can assume that the uploads playlist of a channel does not also need the contentDetails.PublishedAt field queried.

[derekantrican]

For now, I've just converted all usages of Snippet.PublishedAt to ContentDetails.VideoPublishedAt. But for non-uploads playlists, we may want to offer the user an option to choose between alerting/downloading when "a video is added to the playlist" or when "a video is uploaded to YouTube"