refactor lib/sshnp.dart to allow it to be used in a desktop app as well as a CLI

[gkc]

Is your feature request related to a problem? Please describe.

Currently there are some behaviours which will not work in a desktop app. For example exit statements

Describe the solution you'd like

SSHNP class should be reusable in either the existing CLI or in the (new) desktop app.

Describe alternatives you've considered

No response

Additional context

No response

[XavierChanth]

I will start this in tandem with the changes I'm doing for #196

[XavierChanth]

@gkc I noticed that the sessionId was not being used to generate the path in sshnpd...
https://github.com/atsign-foundation/sshnoports/blob/284b01cb14012a593d39b2a37edfd960fed48708/packages/sshnoports/lib/sshnpd.dart#L296-L314

but it is used in sshnp...

https://github.com/atsign-foundation/sshnoports/blob/284b01cb14012a593d39b2a37edfd960fed48708/packages/sshnoports/lib/sshnp.dart#L600-L618

I am trying to merge these two functions into a single one, since they are similar enough.
Should sshnpd's path also be '$atsign/$sessionId' for its hive path or should I make sessionId an optional part of the path like in my code below:

Future<AtClient> createAtClientCli(
    {required String homeDirectory,
    required String atsign,
    String? sessionId,                    // ! OPTIONAL
    required String atKeysFilePath}) async {
  
  String pathBase = '$homeDirectory/.sshnp/$atsign/';
  if (sessionId != null) {
    pathBase += '$sessionId/';            // ! ONLY ADDED WHEN NOT NULL
  }
  // ... rest of code
}

[XavierChanth]

Starting my work here:

I separated the Impl of SSHNPD to SSHNPDImpl

https://github.com/atsign-foundation/sshnoports/tree/xc-sshnp-refactor

There are technically breaking changes... but only to anyone depending on sshnoports as a library... I don't think we should let that stop us from making these improvements though. Especially since the binaries themselves will be non-breaking

[gkc]

@XavierChanth they are different for sshnpd vs sshnp because the storage path acts as a kind of a mutex. We want only one sshnpd to be running at any given time for a given user on a given host or container; but we want to allow many sshnp to be run concurrently

@cconstab can explain further

FYI I'm out of office until Monday now so I'll be catching up with work stuff once or twice a day Thu & Fri but not at all on Sat & Sun

[XavierChanth]

Closed by the latest refactoring