[Feature]: Additional checks to prevent users from using Pretendo on a non working installation

[piplupness]

Checked Existing

• I have checked the repository for duplicate issues.

What feature do you want to see added?

For now, Nimbus only checks if game patches and external firms are enabled and Luma3DS version being at least 13.0. But it's not enough.
Nimbus needs to also check the following:

• Nimbus must work exclusively if Luma3DS is running from a SD card, so a simple boot.firm check should be enough
• Make sure all the Nimbus patches are working, by checking for missing files or corrupted files.

Why do you want to have this feature?

As I have been helping people for a year, this change can help with troubleshooting by just reopening Nimbus and save a lot of time. (Telling people what's the issue in the app basically)

The first option will help people fix the 002-0121 error code (some people think it's a ban!!!)
The second option can help to fix 015-3060/015-3073 on Miiverse, a few 022-2613 cases when making a new PNID.

I may forgetting more error codes but this a must have to improve the setup experience.

Any other details to share? (OPTIONAL)

No response

[jonbarrow]

@DaniElectra I'm fine with this, what say you?

[DimitriPilot3]

• Nimbus must work exclusively if Luma3DS is running from a SD card

Luma3DS actually provides that information through IPC: svcGetSystemInfo(&isSdMode, 0x10000, 0x203)

A simple sdmc:/boot.firm check would miss certain edge cases:

• the user may have re-inserted the SD card after booting without it;
• the user may have reinstalled Luma via UU but has not rebooted the console yet;
• boot.firm may be corrupt or the SD card cannot be mounted by Luma3DS (may be fixed by reformatting the SD)

Thus, I propose we check that sdmc:/boot.firm exists, starts with "FIRM" in the first 4 bytes, and isSdMode != 0

[DaniElectra]

As mentioned the SD card check is doable, though the integrity checks are a more complex issue

[MisterSheeple]

I'd like to point out that now that Pretendo officially supports Azahar, this issue is a very important one to solve.

I just got done helping a user put their Nimbus files in the right location because the Azahar setup requires more manual intervention than real 3DS units do, and the Nimbus part is one where it can be easy to fail. But the user didn't know any of this, because to them, they thought they were able to switch to Pretendo fine because Nimbus didn't pop up any errors about there being missing files. The Azahar devs plan to help make this easier for us by including an "Open SDMC folder" button, but this isn't really a full solution to the problem. There really needs to be a simple file existence check for all of the files Nimbus is expecting to be on the SD card. This would save so much time diagnosing issues like this both on Azahar and 3DS hardware.