GenServer that owns an OTP :ssh.daemon/2 listening for TUI clients.

This is the transport-level supervisor for ExRatatui.App under transport: :ssh. It starts an :ssh daemon on the requested port, registers the app module as an SSH subsystem + default shell, and tears the daemon down on shutdown. Each connected SSH client gets its own ExRatatui.SSH channel process, which in turn supervises its own internal server running the app — so a single Daemon can serve many concurrent clients without any shared state between them.

Usage

Typically you don't start this directly; use ExRatatui.App routes start_link(transport: :ssh, ...) through here. But for full control you can add it to a supervision tree by hand:

children = [
  {ExRatatui.SSH.Daemon,
   mod: MyApp.TUI,
   port: 2222,
   system_dir: ~c"/etc/ssh",
   user_dir: ~c"/var/ssh/users"}
]

Options

• :mod (required) — the ExRatatui.App module to serve.
• :port (default 2222) — TCP port to listen on. 0 picks a random free port — call port/1 on the daemon pid to discover the chosen port.
• :system_dir — path to the daemon's host key directory, forwarded as-is to :ssh.daemon/2. May be a binary or charlist; binaries are converted automatically.
• :auto_host_key (default false) — when true, the daemon resolves the OTP application that owns :mod, ensures <priv_dir>/ssh/ exists, and generates a 2048-bit RSA host key there on first boot (ssh_host_rsa_key). Subsequent boots reuse the same key. Set :system_dir explicitly to override the directory; passing both raises. Intended for "drop into a supervision tree and it just works" setups (Phoenix admin TUIs, internal tools); production deployments should keep an explicit :system_dir under their own configuration management.
• :user_dir — path to client-authentication key material.
• :authorized_keys — forwarded through to :ssh.daemon/2.
• :name — process name (default __MODULE__, pass nil to skip).
• :app_opts — extra opts that will be merged into every client's mount/1 callbacks (e.g. shared PubSub topic names).
• Any other keyword pair is forwarded verbatim to :ssh.daemon/2, so e.g. :pwdfun, :idle_time, :profile all work unchanged.

Testability

:daemon_starter and :daemon_stopper keyword options let tests substitute fakes for &:ssh.daemon/2 and &:ssh.stop_daemon/1 so the GenServer can be exercised without starting a real SSH listener. The real functions are the defaults; production callers never pass either.