package keymgr

import "ssh-access-tui/internal/model"

// AllocatedForward is a model.Forward together with the local port it will
// be bound to on the user's machine.
type AllocatedForward struct {
	model.Forward
	LocalPort int
}

// localPortBase is where every local port is handed out from. Forwards are
// never given a local port equal to their remote port: many remote ports
// worth forwarding are privileged (< 1024 — ssh's own 22 above all), and
// binding a listener on a privileged local port requires admin/root rights
// the end user does not have and should not need. Even for unprivileged
// remote ports, always starting from a fixed high range keeps assignment
// simple and collision-free without a "does this port happen to be free
// locally" special case.
const localPortBase = 20000

// AllocateLocalPorts assigns every forward a local port, all of which the
// user opens at once over a single ssh connection (one LocalForward line
// per forward — see RenderClientConfig). Ports are handed out sequentially
// from localPortBase, so many forwards sharing the same remote port (e.g.
// port 22 repeated across ten hosts) each still get a distinct, unprivileged
// local port. Assignment is a pure function of the input order, so
// re-exporting an unchanged host list reproduces the same local ports.
func AllocateLocalPorts(forwards []model.Forward) []AllocatedForward {
	next := localPortBase
	out := make([]AllocatedForward, 0, len(forwards))
	for _, f := range forwards {
		out = append(out, AllocatedForward{Forward: f, LocalPort: next})
		next++
	}
	return out
}