It would help if you could explain the use case a bit more in detail. I think I understand that this is supposed to be only for a manual backup, but what I’m still a bit fuzzy about is why the backup must not be a normal sync process, that is pushing out the cached data and pulling in anything that might have been added from other devices.
I want to have a manual backup that overrides any other client’s version of the data. So even if another device has saved data, the data I upload forces that to be the data without being modified.
It’s as a sort of last resort to restore a previous backup saved on the user’s device.
The problem with these requirements is that what you’re describing is quite impossible for a program to figure out in the case of arbitrary data being backed up. That’s why it would be helpful to know your actual use case, not just your current conclusion on what you think the requirements should be.
Whatever you PUT onto the server, even if you force-overwrite remote data, is not certain to be the only data you have in that directory/on the server, as soon as any other device can theoretically also write data to it. If you don’t care about any other documents in the same directory (a.k.a. sync the entire situation, not just what you have locally), then your restore will not be done with what you manually backed up, but with what you force-pushed plus whatever else was on there.
The only way (that I can currently see) to safely create a one-off backup with 100% only the data you have locally on that device, is to also manually manage a specific directory it is created in. You could copy your documents to that namespace and then simply enable caching for it. And when you want to restore, you could select that namespace/directory and also just sync whatever is in there back.
However, it’s not really possible to recommend a good approach to you, without knowing anything else about the use case, like for example what kind of data is being backed up, how many documents, what average document size, and so on.
So what you can do is for example copy all documents to something like my-category/backups/2018-03-13/, then enable caching for that and sync it to the server. And for a restore, you could let a user choose from your list of backup subdirectories and then do the same, but this time the sync would retrieve it from the server.
@Putu Let me know how it’s going, and if I can still help in any way. Would be great to document the outcome of this for other developers, who might run into the same issues.