Playlists history

Capabilities
1. Keeps track of changes of the YouTube playlists (saves playlists history).
2. Subscribes to a specific playlist instead of the whole channel.
3. Gives the ability to investigate deleted videos.
4. Shows max quality video thumbnails.
5. Reserves thumbnails of deleted videos.

1. Summary
The app generates a change story for YouTube playlists. The story includes information about the video, including images, and includes information about the action with the video in the playlist. The data with the history is stored in a Google Drive account, so the app can run on other hardware with the same playlist history.

2. Description
The system is a single-page application (SPA) and expands YouTube's capabilities, allowing the user to save their playlist history.
The app data is stored using the Google Drive API in the user's account. YouTube data is requested through the YouTube Data API.

Items on YouTube
The user interfaces of SPA and YouTube are connected by links and buttons built into YouTube pages.

2.2. Location of built-in items
1. Playlist action panel:
1. The "Playlists history" link (available only if the system has the playlist);
2. The "Keep history" button (only available if there is no playlist in the system);
2. The "Playlists history" link to the playlists history page is in the YouTube history section;

2.2. Spa

2.2.1. Playlists section
The page shows a list of items. Each item describes the history of the playlist.

Possibilities:
1. Filtering items by the name of the playlist;
2. Filter the history in the playlist using the initial date;
3. Hiding all the elements with an empty history;
4. Removing the history before the chosen date;
5. Enabling the editing mode of the items;
These elements may belong to two groups: "Mine" and "Manually added."

The “Mine” group
The group contains information about the user's playlists and can only be created if he has created his own channel. Elements of this group are added automatically and can not be manually deleted.

The “Manually added” group
Contains information about added playlists using the "Keep history" button. These items can be removed manually.

Item editing mode
Items acquire two additional properties: “Deep Check” and “Save Images”.
The enabling of the “Deep Check” feature forces the system to make more requests to YouTube Data API, but it lets you know the approximate moment when the (existing) video is no longer available. If you turn this feature off, the history will only be updated if someone adds or deletes the video from the playlist.
Turning on "Save images" requires additional requests to the Google Drive API, but this allows you to view the stored image of the unavailable videos. The images are stored on the user's Google Drive. This user is shown in the settings. If the video is available from at least one playlist registered in the system, the saved image will not be used.

Playlist history
When you click on the image inside the item, you'll be navigated to the page with the list of playlist changes. Filtering options are not lost.
The playlist history page contains a table with change data. Each row of this table opens the modal window with the details of the change when clicked.

2.2.2. Settings
The section consists of a form with fields. The form allows you to change the settings of the system. You can create a list of configurations with different names. An active configuration is set in the dropdown list when the page is loaded.

Possibilities
1. Editing the name of the folders and files in the Google Drive used by the app.
2. Security settings (only for developers), including user change.
3. Default settings for “Deep Check” and “Save Images”.
4. Settings for the frequency of the history generation mechanism.

Changing the user
This feature is controlled by the "Use Chrome App client id from manifest.json file" checkbox.
Turning on the feature forces the system to use the credentials used by the browser. The need to enter credentials will be rare. When you turn off the feature (and save) you can change your credentials (you can not do that if you don't have client id) by clicking on the "Change login" button, but credentials will be requested more often.

2.2.3. Information
The section contains data to monitor the system. The system uses APIs that have limitations.

Recommendations
The system must successfully execute the history generation mechanism at least once every 24 hours. This can be understood by the value of "Refreshed." Turning off "Deep Check" and/or "Save images" increases the chances of a successful running of the history-generating mechanism, especially for large playlists.