proc get_ip {host} {
  lassign [split $host .] host
  set host $host.psi.ch
  # clientlog HOST:$host
  set ip [exec dig $host +short]
  # clientlog IP:$ip
  return $ip
}

proc get_subnet {ip} {
  if {[string match {129.129.*} $ip]} {
    set subnet office
  } else {
    set instip [lrange [split $ip .] 0 2]
    # instrument computer ip ends with 60
    lappend instip 60
    lassign [split [exec dig -x [join $instip .] +short] .] subnet
  }
  return $subnet
}

proc get_rack {{oldrack ""}} {
  source config/rack.list
  set mysubnet [get_subnet [get_ip [info hostname]]]
  if {$oldrack ne ""} {
    array set racks $racklist
    if {[catch {
      set racklist [list]
      lappend racklist $oldrack $racks($oldrack)
    }]} {
      return "$oldrack is not in ~/sea/tcl/config/rack.list"
    }
  }
  set found [list]
  set inmynet [list]
  foreach {rack rack_cfg} $racklist {
    array set cfg_array $rack_cfg
    if {[catch {
      lassign [split $cfg_array(_cc) :] host
    } msg]} {
      return "$oldrack has no ccu configured $msg $rack_cfg"
    } 
    if {$host ne "unconnected"} {
      set ip [get_ip $host]
      if {$ip eq ""} {
        if {$rack eq $oldrack} {
          return "$rack not reachable"
        }
      } else {
        set subnet [get_subnet $ip]
        if {$mysubnet eq $subnet} {
          lappend found $rack
          lappend inmynet $rack
        } elseif {$subnet eq "office"} {
          lappend found $rack
        } elseif {$rack eq $oldrack} {
          return "$rack at $subnet net is not accessible from $mysubnet net"
        }
      }
    }
  }
  set hostname [lindex [split [info hostname] .] 0]
  if {$mysubnet ne "office" && [llength $inmynet] && $hostname eq [result instrument]} {
    # if any rack is in the instrument subnet, racks in office net are not shown
    return $inmynet
  }
  return $found
}