#!/bin/sh
# Copyright 2011 CyberLeo, All Rights Reserved
# http://wiki.cyberleo.net/wiki/CyberLeo/COPYRIGHT

meh() { printf "%s\n" "${*}"; }
omg() { printf "%s\n" "${*}"; }
wtf() { printf "%s\n" "${*}"; exit 1; }
pebkac() {
  [ "${*}" ] && printf "%s\n\n" "${*}"
  cat <<EOF
Usage: <start|enter|stop> <jailname>
EOF
  exit 1
}

cmd="$(basename "${0}")"
base="$(realpath "$(dirname "${0}")")"
jail="$(basename "${1:-DebianChroot}")"
jdir="${base}/${jail}"

[ -d "${jdir}" ] || wtf "${jail}: not a jail?"

# Propagate certain environment variables; sterilize the rest of the environment
env="
  TERM=${TERM}
  USER=${USER}
"

# Create a new jail (Will not work, since a new jail will not exist and will not pass the 'not a jail' check above)
jail_new() {
  DEBOOTSTRAP_DIR="$(base)/debootstrap" "${DEBOOTSTRAP_DIR}/debootstrap" --arch=amd64 squeeze "${jdir}"
}

# Jail is 'up' if /dev/pts and /proc are mounted
jail_up() {
  grep -q "^devpts ${jdir}/dev/pts devpts" /proc/mounts || return 1
  grep -q "^proc ${jdir}/proc proc" /proc/mounts || return 1
  return 0
}

# Mount /dev/pts and /proc in the jail
jail_start() {
  jail_up && return 0
  meh "starting ${jail} ..."
  mount -t devpts devpts "${jdir}/dev/pts"
  mount -t proc proc "${jdir}/proc"
}

# Enter jail
jail_enter() {
  jail_up || wtf "jail not up"
  meh "entering ${jail} ..."
  env -i ${env} /usr/bin/chroot "${jdir}" /bin/su "${USER}" -c /bin/bash -l
}

# Unmount /dev/pts and /proc in the jail
jail_stop() {
  jail_up || return 0
  meh "stopping ${jail} ..."
  umount "${jdir}/proc"
  umount "${jdir}/dev/pts"
}

# Need root beyond here
[ "$(id -u)" -eq 0 ] || exec sudo env ${env} "${0}" "${@}"

case "${cmd}" in
start) jail_start ;;
enter) jail_enter ;;
stop)  jail_stop  ;;
*) pebkac ;;
esac