#!/bin/bash
# Keeps respawning stapsh on the given port
# External programs used: basename, date, expr (all in coreutils)
# Must be in libexec dir

STAPSH=@bindir@/stapsh

# Make sure we were given a port
if [ ! -n "$1" ]; then
   echo "Usage: `basename $0` <port>" >&2
   exit 1
fi

STAPSH_PID=/var/run/stapsh.$(basename $1).pid
STAPSHD_PID=/var/run/stapshd.$(basename $1).pid

# Make sure the port exists
if [ ! -c "$1" ]; then
   echo "Argument $1 is not a character device" >&2
   if [ -f "$STAPSHD_PID" ]; then
      rm "$STAPSHD_PID"
   fi
   exit 2
fi

# Returns the time in seconds
now() {
   echo $(date "+%s")
}

# Returns the time elapsed in seconds since arg
elapsed() {
   echo $(expr $(now) - $1)
}

# If stapsh is restarted more than 5 times in less than 1 second, we abort
last=$(now)
respawns=0
while [ true ]; do
   if [ "$(elapsed $last)" -gt 1 ]; then
      last=$(now)
      respawns=0
   elif [ "$respawns" -gt 5 ]; then
      echo "Too many respawns... aborting" >&2
      rm "$STAPSH_PID"
      if [ -f "$STAPSHD_PID" ]; then
         rm "$STAPSHD_PID"
      fi
      exit 3
   elif [ ! -c "$1" ]; then
      echo "Port no longer available" >&2
      if [ -f "$STAPSHD_PID" ]; then
         rm "$STAPSHD_PID"
      fi
      exit 4
   fi
   $STAPSH -l "$1" &>/dev/null &
   pid=$!
   echo $pid > $STAPSH_PID
   wait $pid
   respawns=$(expr $respawns + 1)
done