Documentation on installed apps should show availability

[IzzySoft]

When creating the documentation for user-installed apps, we should point out whether they are still available at their source (see: How to get notified about removed apps from play store?).

At least for Playstore, this can be done by a simple HTTP request (which returns a 404 when the app became unavailable). If possible, we could even include more details (optional/configurable), such as last version available (as opposed to the version currently installed).

[IzzySoft]

For minimal overhead, we can use something like this to verify availibility (not available version):

[wget --method=HEAD -O - $url
rc=$?
if [[ $rc -eq 8 ]] …    # app unavailable
elif [[ $rc -eq 0 ] ... # app available
else ...                # unknown status (some error running `wget`)

This works for Playstore and Xposed, but e.g. not for F-Droid (which always replies with a "200 OK" and neither gives any indicator in the HTTP headers of its server-response). F-Droid would require getting the full page and parse it for the package name, which is not present if the app is not available (unless it's accidentally a substring of something else (to avoid that, we can simply prefix the package name by "/repo/", counting on the download link).

However, those "network checks" must be optional (i.e. user must opt-in by setting the corresponding variable(s)). Corresponding to the APP_MARKET_URL we could introduce a APP_MARKET_CHECK variable pointing out the check method to use on the URL defined by the former (empty for no check, HEAD for the first method above, or a string to parse GET for – which could be /repo/%s for F-Droid with the %s then being replaced by the package name).

As getting the latest version from all possible markets would go a bit beyond Adebar itself, we could at least give the user an option to provide an own script for this purpose – as done with APPNAME_CMD already, say APPVER_CMD – passing it the package name and installer name as parameters.

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As I'm still unsure if this feature is really wanted, I'm waiting for "thumbs up" on the initial post to indicate interest 😇

[IzzySoft]

Update: wget --method=HEAD --server-response https://f-droid.org/packages/<package_name>/ dutifully reports HTTP/1.1 404 Not Found if an app does not exist and HTTP/1.1 200 OK if it's there. So the following command should return 0 if an app is unavailable at F-Droid, and >0 (=1) otherwise:

wget --method=HEAD --server-response https://f-droid.org/packages/<package_name>/ 2>&1 |grep HTTP |grep "200 OK" |wc -l

For performance, apart from making the checks optional, it should by default also be restricted to the site the install source indicates (i.e. when it was installed from F-Droid, only check F-Droid) – maybe with an option to check "alternative sources" if an app is no longer available at its original source.

For "latest version available" it gets more tricky – as without involving other dependencies, this would require "scraping" the corresponding web pages. This might be overkill, though, as updates are usually dealt with on-device, using the corresponding apps (Playstore/Yalp/Aurora, F-Droid etc).