utils/tunnel-nim/tunnel.nim

import std/[os, osproc, sequtils, strformat, strutils, sugar]
import cligen

proc checkHost(host: seq[string]): string =
  case host.len:
  of 1: return host[0]
  of 0: quit "expected hostname"
  else: quit "expected one positinal argument"

proc check(name: string): bool = (execCmd &"ssh -O check {name}") == 0
proc startSsh(name: string) = discard execCmd &"ssh -M -f -N {name}"
proc activateTunnel(name: string, port: int): int = execCmd &"""ssh -fNL "{port}:localhost:{port}" {name}"""
proc exitSsh(name: string):int = execCmd &"ssh -O exit {name}"

proc up(port: int, host: seq[string]) =
  ## activate a tunnel
  let name = checkHost host
  echo "activating connection to", name
  if not check(name):
    startSsh(name)
  quit activateTunnel(name, port)


proc down(host: seq[string]) =
  ## disable all tunnels
  let name = checkHost host
  echo "deactivating connection to", name
  quit exitSsh(name)

proc show() =
  ## show active connections
  let sshDir = (getEnv "HOME") / ".ssh"
  let controllers =
    collect(for _,p in walkDir(sshDir): p)
    .map(extractFilename)
    .filterIt(it.startsWith("control"))
  echo &"{controllers.len} active connections"
  if controllers.len == 0: quit 0
  echo "hosts:"
  echo controllers.mapIt("  " & it.split('-')[1]).join("\n")

const
  hostUsage = "$command [flags] hostname\n${doc}Options:\n$options"
  usage = "$command [flags]\n${doc}Options:\n$options"

dispatchMulti([up, usage=hostUsage], [down, usage=hostUsage], [show, usage=usage])