#!/usr/bin/env bash

help () {
  echo 'dchr-run [options] <chroot-dir> [command]'
  echo '-- options:'
  echo '   -u uid[:gid]  invoke command in chroot as a different user'
  # TODO:
  #echo '   -x11          apply options for correctly starting GUI apps'
  echo 'https://dchr.dc09.ru'
}

clean () {
  echo '-- Cleaning up'
  umount "$1/proc"
  umount "$1/sys"
  umount "$1/dev"
  umount "$1/run"
}

error () {
  echo -e '-- \e[1;31mError\e[0m -- see output above'
  exit 1 # `trap` in main() calls cleanup function
}

setup () {
  echo '-- Mounting'
  mount -t proc /proc "$1/proc" || error
  mount -t sysfs /sys "$1/sys" || error
  mount -o bind /dev "$1/dev" || error
  mount -o bind /run "$1/run"
}

runcmd () {
  echo -e '-- \e[1;32mOK\e[0m -- running chroot'
  userspec="--userspec=$1"
  chrdir="$2"
  shift 2
  chrcmd=("$@")
  chroot "$userspec" "$chrdir" "${chrcmd[@]}"
}

main () {
  [[ "$1" == "--help" || "$1" == "" ]] && help && exit 0

  userspec="$(id -u):$(id -g)"

  while [[ "$1" == -* ]]
  do
    case "$1" in
      -u)
        userspec="$2"
        shift 2
        ;;
      #-x11);; TODO
      *)
        echo -ne '-- \e[1mInvalid option:\e[0m '
        echo "$1"
        echo '-- Use ./ or full path if your chroot-dir starts with dash (-)'
        help
        exit 2
        ;;
    esac
  done

  chrdir=$(readlink -f "$1")
  shift

  trap "clean \"$chrdir\"" EXIT

  setup "$chrdir"
  runcmd "$userspec" "$chrdir" "$@"
  exit $?
}

sourced () {
  [ -n "$ZSH_VERSION"  ] && [[ "$ZSH_EVAL_CONTEXT" =~ :file ]] && return 0
  [ -n "$BASH_VERSION" ] && [[ "$0" != "$BASH_SOURCE" ]] && return 0
  return 1
}

sourced || main "$@"