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

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

meh() { printf " \033[1;32m*\033[0m %s%s\n" "${jname:+${jname}: }" "${*}"; }
omg() { printf " \033[1;33m*\033[0m %s%s\n" "${jname:+${jname}: }" "${*}"; }
wtf() { printf " \033[1;31m*\033[0m %s%s\n" "${jname:+${jname}: }" "${*}"; exit 1; }
pebkac() {
  [ "${*}" ] && printf "%s\n\n" "${*}"
  cat <<EOF
Usage:
  <command> <name> [arguments]
  list
  ls      list available chroots

  status  show jail status

  start   prepare an existing chroot for use

  stop    undo what 'start' did

  enter
  shell   spawn a shell or command within the chroot

  eval    evaluate a shell command line within the chroot

EOF
  exit 1
}

cmd="$(basename "${0}")"
jbase="${J_BASE:-$(realpath "$(dirname "${0}")/../")}"
jname="${J_NAME:-$(basename "${1}")}" #"
juser="${J_USER}"

# Remove jail name from argument stack, if passed in
[ "${J_NAME}" ] || shift

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

# Create a new chroot, somehow
j_init() {
  # Either a debian jail with debootstrap or a gentoo jail with stage3 + portage tarballs
  DEBOOTSTRAP_DIR="$(base)/debootstrap" "${DEBOOTSTRAP_DIR}/debootstrap" --arch=amd64 squeeze "${jdir}"
}

# Figure out and set jail parameters; needed for all functions that follow
j_params() {
  jname="${1:-jname}"
  # Given a jail name, find and set up the jail dir
  jdir="${jbase}/${jname}"
  [ -d "${jdir}" ] || wtf "not a directory"

  # Where is the shell?
  for shell in /bin/bash /usr/bin/bash /usr/local/bin/bash /bin/sh
  do
    if [ -f "${jdir}/${shell}" ]
    then
      jshell=${shell}
      break
    fi
    wtf "cannot locate usable shell; is this a real jail?"
  done
}

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

j_status() {
  j_up && meh "$(printf '\033[1;32mup\033[0m')" || meh "$(printf '\033[1;31mdown\033[0m')"
}

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

# Execute command in chroot
j_eval() {
  j_up || wtf "jail not up"
  meh "entering ${jail} ..."
  env -i ${jenv} /usr/bin/chroot "${jdir}" /bin/su "${juser:-${USER}}" -c "${*}"
}

j_shell() {
  j_eval "${jshell} -l"
}

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

# Populate jvars
j_params "${jname}"

case "${cmd}" in
status) j_status ;;
start) j_start ;;
shell|enter) j_shell ;;
eval) j_eval "${*}" ;;
stop)  j_stop  ;;
*) pebkac ;;
esac